Cad . Saúde Púb lic a, Rio de Jane iro , 14(Sup. 3):7-13, 1998
Genetic polymorphism and their
cont ribution to cancer susceptibility
P o l i m o rfismo g e né tic o e sua c o ntrib uiç ão
na susc e ptib ilid ad e ao c ânc e r
1 In stitu t o de Bi o c i ê n c i a s , L e t ras e Ciên cia s Ex a t a s , Un i v ersid a de Es t a d u a l Pa u l i s t a .
Crist óv ão Colom b o 2 265, Sã o José d o R io Pre t o, São Pa u l o , SP 1 5 0 5 4 - 0 0 0 , Bra s i l . 2 De p a rt m en t of Pre ve n t i ve M e d i c i n e , Un i v ersit y of Tex a s - M ed ical Bran ch of Ga l ve s t o n . Ew i n g Ha l l , 700 Ha r b o r s i d e D r i ve , 77 555- 11 10 Ga l ve s t o n , T X ,U S A .
N í v ea Con fo rt i - Froes 1 Ra n d a El - Z ei n 2 W illi a m Au 2
Abstract Si n ce t h e m ajo rit y o f ch em i ca l ca rcin oge n s a re n o t ca p a ble of ca u sin g h a z a rd o u s ef-f ect s p er se , t h e m et a b oli sm oef-f t h ese co m p ou n d s is a cru ci a l p a rt o ef-f t h e i n it ia l h ost resp o n se t o t h e en v iron m en t a l ex p o s u re . D ist u rb an ces in t h e bala n ce b et w een a ct iv a t ion an d d et ox i f i c a t i o n m ay t h u s ex p la in t h e in div id u al v aria t ion s in resp on ses to ex p o s u res t o carc i n o g e n s . Th e a m ou n t of t h e u lt im a t e ca rci n ogen p ro d u ced d ep en d s o n t h e a ct io n of com p et in g act iv a t i on a n d d et ox i-fica t ion p at h w ays in v olv in g cytoch rom e P450 a n d glu t a t h ion e-S- t ra n s f e ra ses en z ym es.
Key words Po lym orp h ism (Ge n e t i c s ) ; N e o p l a s m ; Molecu la r Ep i d e m i o l o gy
Re sumo U m a v ez q u e a m a i ori a d o s ca rcin o gên i co s qu í m i cos n ã o é ca p a z d e ca u sa r efei t o s d a n osos p er se, o m eta bolism o d esses com p ost os é a p a rt e cru cial d a resp osta in icia l à ex p o s i ç ã o a m b i e n t a l . Os d ist ú rb ios ca u sa d os n o ba la n ço en t re os p rocessos d e a t iv a çã o e d est ox ifica çã o p o-d e m , a s s i m , ex p li ca r a s v a ri a ções in o-d i v i o-d u a i s em re sp o st a à ex p o si çã o a os ca rc i n o g ê n i c o s . A qu a n t id ad e d e com p ost os carcin ogên icos fin a is p rod u z ida dep en d e d a a çã o com p et it iv a en t re os p assos d e a t iv a çã o e d est ox i f i c a ç ã o, e n vo l v en d o a s en z im a s do cit o crom o P450 e d a s S-glu t a t ião t ra n s f e ra s e s .
Cad. Saúde Púb lica , Rio d e Jane iro , 14(Sup . 3):7-13, 1998 I n t ro d u c t i o n
Genetic fact ors in individual responses t o environmental exposure
Ac c o rd in g t o t h e rece n t a d va n ce s in m o lecu la r e p i d e m i o l o g y, a n e m e rgin g n e w field th a t co m -b in e s h igh ly se n sitive a n d sp e cific t e ch n iq u e s fo r d e t e ct in g e a r ly d a m age a s s o cia t e d wit h c a n c e r, it h a s b e e n p o ss ib le t o id e n t ify ri s k s a n d p re ve n t a d ve r se h e a lt h e ffe ct s re la t e d t o e n v i ro n m en ta l exp o su re s.
T h e re a re ap p roxim at ely 500,000 can cer- re-la t e d d e at h s a n n u a lly in t h e Un it e d St a t e s; a s m an y a s 80% o f t h o se d ea th s cou ld b e p re ve n t -e d d u -e t o th -e fa ct th at m o st m align an ci-e s a r-e a re su lt o f e xt e r n a l fa ct o r s ra t h e r t h a n in h e re n t b io logical co n d ition s (Eu b a n k s, 1994). By co m b in in g kn owle d ge a b o u t e xt e rn a l fa ct o rs re l a t -e d t o lif-e st yl-e a n d -e n viro n m -e n t al o r o c cu p a-t ion al e xp osu re a-t o ch em ica ls wia-t h h ow ge n e a-t ic d i f f e ren ce s ca u se va riation s in h um an res p o n s e t o e n viron m en t al p ollu t an t s, it will b e p o ssib le t o a n swe r q u est ion s like wh y ce rt a in gro u p s of p e o p le h a ve a h igh e r in cid e n ce o f ca n ce r a ft er e x p o s u re t o a toxican t an d ot h e rs d o n o t. Mo l e-cu lar ep id em io lgy is an e m e rgin g n ew field t h at c o m b in e s h igh ly se n sit ive m o le c u la r t e c h -n iq u e s fo r d e t e ct i-n g e a rly d a m a ge a s s o c i a t e d wit h ca n ce r.
Fo r t h is p u r p o se, it is n e ce ssa ry t o u se b io -lo gic a l m ar ke rs a s “in dica t ors sign a lin g eve n t s in bio logica l syst em s or sa m p les”( Na t io n a l Re -s e a rch Cou n cil, 1987:3). U-s u a l l y, t h re e t yp e -s o f b iological m arkers are id en tified : th e first is a b i-o li-o gic a l m a rke r i-o f e xp i-o su r e, i-or e xp i-o su re b ii-o- io-m a rk e r, t h at io-m a y b e an e xo ge n o u s c o io-m p o u n d (or a m eta b olit e) with in th e b o d y, a n in tera c t i ve p r od u ct b e t we e n t h e co m p o u n d (o r m e t ab olite ) an d an e n d oge n ou s com p on e n t, or a n ot h -e r -e v-en t r-ela t-e d t o t h -e -e xp osu r-e. Th -e s-eco n d , a m a rker for the effect, wh ich m ay b e an en d o gen o u s com p o gen egen t , o r a m e asu re o f th e fu gen ctiogen -al cap a cit y, o r so m e o t h e r in d ic a t o r o f st at e or b a la n ce of the b od y o r orga n system , as affected b y th e exp osure. Su ch effect m arke rs are gen er-a lly p re clin icer-al in d icer-at ors o f er-ab n o rm er-a l i t i e s. T h e t h i rd is a m a rke r o f s u sce p tib ilit y, w h e t h e r in -h e rited or in d u ced , w-h ic-h serves as an in d icator in th a t in d ivid u a l is p articu la rly sen sitive to th e e ffect of a xen o b iot ic or to t h e e ffects o f a gro u p o f su ch co m p ou n d s (Gran d je an et a l., 1994).
Am o n g all b io m a rk e r s , t h e m a rke rs o f su sce p t ib ilit y a re p a rt icu la rly re l e va n t t o d e t e r m in in g in h e rit e d p re d isp o sit io n t o risk o f a d -ve rs e h e a lt h e ffe c t s a s a re s u lt o f e xp o s u re t o e n v i ro n m en tal ch e m ica ls. Th e u n d erlyin g p ri n
-cip le o f t h is m a rke r is t h e in t e r in d ivid u a l d if-f e re n ce s t h a t co n if-fer se n sit ivity o r resista n ce t o e n v i ro n m e n t a lly in d u c e d d ise as e . T h e r e a re t h ree typ es o f su scep tib ilit y m arkers: th e first is b a s e d o n t h e fa ct t h a t m o s t ch e m ica ls a re a lt e red by e n zym es an d lt h e se allte ra ltion s m a y in -c re a se o r d e -c re a s e t h e a b ilit y o f a -ch e m i-ca l t o i n t e ra c t wit h t is su e m a cro m o le cu le s s u ch a s DNA, RNA, o r p ro t e i n s. Th e b a la n c e b e t we e n e n zym e s t h a t a ct iva t e a n d d e t o xify ch e m ica ls d iffers a m on g in d ivid u a ls an d et h n ic gro u p s. A se co n d t yp e o f s u s ce p t ib ilit y m a rke r re f l e c t s ge n etic d ifferen ces in t h e ca p a cit y o f cells t o re p air DNA d am a ge ca u se d by en viron m en t al in -su lt. Pe o p le d eficien t in DNA re p air ge n es m ay e xh ib it m o re DN A d a m a ge m an ife st e d as in -c re a s e d le ve ls o f D NA a d d u -ct s; a lt e ra t io n s in c h rom o so m e n u m b e r, st ru c t u ra l ch ro m o s o m e m o d ific a t io n , ac t iva t e d o n c o ge n e s a n d t h e ir p rot ein p ro d u ct s a n d h igh e r in cid e n ce of can c e r. A t h ird typ e o f su scep tib ility m arker is p re -exist in g in h e rit ed ge n e tic d e fe ct s t h a t in cre a s e th e risk of ca n cer. If a p e rson h as in h erite d on e o r m o re o f t h e n e ce ss a ry ge n e t ic a lt e r a t i o n s, f e we r st ep s a re n e ed e d for a ch e m ica l t o cau se c a n c e r, p u t tin g th is p e rson at a greate r risk. We will co n ce n t ra t e o n t h e first o n e re la t e d t o e n -zym e m et ab olism .
Susceptibility marker and enzyme m e t a b o l i s m
T h e re is con sid era b le va ria tion am on g h u m a n s in t h e p ro d u c t io n o f e n zym e s t h a t e it h e r a ct i-vat e t h e for m at ion o f e le ctro p h ilic m et a b o lit es th a t cova le n tly b in d to DNA o r ca t alyze d e tox i-fica t ion o f che m ical ca rcin o gen s (Ha r ri s, 1989; 1 9 9 1 ) .
Dist u rb a n ce s in t h e b a la n ce b e t wee n act i-vatio n a n d d e t oxificat io n m a y t h u s e xp la in t h e in d ivid u a l va ria tion s in re sp o n se s t o exp osu re s t o ca rc in o ge n s (H i r vo n e n , 1995). In o t h e r w o rd s, t h e in t e r in d ivid u a l va ria t io n in re -sp o n se t o xe n o b io tics a n d t h e ir p o t e n t ia l c a rcin oge n ic effe ct s is m e d ia t e d by in h e rit ed p re -d ispo sition (Sh i e l -d s, 1994). Ce rta in in -d ivi-d u a ls m a y b e a t sign ifica n t ly grea ter risk o f che m ical-ly in d u ce d ca n ce r t h a n th e a ve ra ge in d ivid u a l d u e to m arke d d ifferen ces in th e a ctivat io n an d d e t oxifica t io n p ro c e s s e s.
Cad. Saúde Púb lic a, Rio d e Jane iro , 14(Sup. 3):7-13, 1998
Th e xe n o b io t ic -m e t a b olizin g m ac h in e r y co n ta in s two m a in t yp e s o f e n zym es: Ph a se I – m e d ia tin g ox i d a t i ve m e t a b o lism , a n d Ph a se II – co n ju gat in g e n zym e s. Ma n y c o m p o u n d s a re c o n ve rte d t o re a c t i ve e le ctro p h ilic m et ab olit es b y t h e ox i d a t i ve P h a se I e n z ym e s , w h ic h ar e m a in ly c yt o c h ro m e P-450 e n zym e s (CYPs ) . Ph a se II c o n ju ga t in g e n zym e s, s u ch a s glu t a t h i o n e S t ra n s f e ra se (GST), UDP g l u c u ro n o -s y l t ra n -s f e ra-se-s an d N-acetylt ra n -s f e ra -se -s ( N AT ) , a ct u su a lly as in act iva t in g e n zym e s (Rau n io e t a l., 1995).
Th e cyt oc h ro m e P-450 ge n e s u p e r f a m i l y c a r r y o u t a m yria d o f d ive rs e b io t ra n s f o rm a tio n s in clu d in g b ot h a n a b olic an d cata b o lic re -ac t io n s ( Wo lf, 1986; U m e n o e t a l., 1988). Du e t o t h e im p o r t a n t ro le o f cyt o c h r o m e s P450 in t h e m e t ab olic a ct iva tio n o f m a n y p ro c a rc i n o g e n s, e xt e n sive re s e a rch in t h e p a st h as fo cu sed o n th e re lat io n sh ip b e t we e n th e d ist ri b -u t io n o f p o lym o rp h ic va r ia n t s o f d iffe re n t i s ozym e s o f P450 a n d can ce r su sce p t ib ilit y. In t h is re sp ec t , t h re e isozym e s in p a rt icu la r h a ve b e en st u d ies: CYP1A1, CYP2D6, CYP2E1.
CYP genes and polymorphism
In rece n t ye a r s, in crea se att en t ion h as b ee n fo cu se d on t he po ssib le re lat io n sh ip b e twe en in -t e rin d ivid u al d iffe ren ce s in CYP gen e s-tru c -t u re a n d in d ucib ilit y of CYP en zym es. Th is in form a t io n h a s b e e n u se d fo r t h e e va lu a t io n o f in -c reased su s-ce pt ib ility for -can -cer. As a m att er of fa ct , m an y o f t h e d ifferen t isofo rm s o f P450 ac-t i va ac-t e p re c a rcin o ge n s an d ac-t h e in ac-t e ri n d i v i d u a l d i f f e re n ces in e xp ressio n o f P450 fo rm s ca u se a p ro n o u n ce d va r ia t io n in t h e le ve l o f t h e a ct i-vate d ca rcin o gen s in th e ce ll.
It is n o t s o lo n g sin ce it wa s b e lie ve d t h a t t h e re we re 2 cyt oc h ro m e P450 e n zym e s, t h e m e t h y l c h o l a n t h re n e -in d u c ib le P448 a n d t h e p h e n o b ar b it o n e -in d u cib le P450. Fr o m c lo n e d cD NA se q u e n ce s, t h e d e d u c e d a m in o ac id s e -q u e n ce s o f so m e 57 P450 sp e c ie s h a ve n o w b e e n a rri ve d at (Id l e, 1991). Th is is a lso a likely e xp la n a t io n if p olym o rp h ic a lly d ist r i b u t e d va ria n t fo rm s o f t h e iso z y m e , w it h d iffe re n t ca t a lyt ic p ro p e rt i e s , occ u r wit h in t h e p o p u la -tio n . P 450 p o lym o rp h ism in c a n c e r su sce p t i-b ilit y co u ld a lso i-b e lin e d t o t h e fac t t h a t t h e P450 iso zym e p a r t icip a t e s in t h e t ra n s f o rm a tio n o f e n d oge n ou s co m p o u n d s, wh ich a re im -p o rta n t d ur in g th e -p roce ss of d ifferen t ia t io n of t h e in it ia t e d c e ll t o t h e u lt im a t e m a lign a n t s t a g e. A ge n e tic lin kage b et we en P450 a n d ca r-cin o ge n e sis m igh t a lso b e fo u n d a t t h e level o f i n h e r it e d h a p lo t yp e s, wh e re a n a s so cia t io n cou ld b e relat ed t o lin kage d iseq u ilib riu m with
c a n c e r-a s so c ia te d ge n e s su c h a s on co ge n e s a n d tum or su p resso r gen es, lo cated in th e s a m e c h rom osom a l re gio n (Ra n n u g e t a l., 1995).
• C Y P 1 A
Th e CYP 1A is t h e ge n e e n c o d in g P4501A1, a P 450 is o zym e t h a t ca t a lyze s t h e oxid a t io n o f p o l yc yclic a r o m a t ic h yd r o ca rb o n s (PAH s ) t o p h e n olic p ro d u ct s a n d e p oxid e s (Go n z a l e s, 1989). Th e in d u ct io n o f CYP 1A1 p ro ce e d s via b in d in g o f t h e in d u ce r co m p o u n d t o t h e a r y l h yd ro c ar b o n (Ah ) re c e p t o r, an d t h e ligan d e d re ce p t o r a c t iva t e s t ra n s c rip t io n o f s e ve ra l gen e s th a t en co d e p rot ein s in vo l ve d in xe n ob i-o tic m e ta b i-o lism .
Th e b io a ct ivatio n of se ve ra l PAHs h a s b e en s h o w n t o b e gin wit h s t im u la t io n of t h e a ro -m a t ic h yd ro ca rb o n (Ah ) re c e p t o r, wh ich t h e n a c t iva te s CYP1A1, e p oxid e hyd ro l a s e , a n d oth -e r -e n z ym -e s (Hi r vo n -e n , 1995). B-e s id -e PA H s, CYP1A1 is a lso in d u cib le b y xe n o b iot ics fou n d in cru c i f e ro u s ve ge t ab le s such a s flavo n e s, a n d b y in d o le d e ri va t i ve s su ch a s ac id c o n d e n s a t io n p ro d u ct s of in d o le 3c ar b in o l a n d p h o t o ox i d i zed d e r i va t i ves o f t r yp t op h a n (Mc D o n -n e ll e t a l., 1992). Ad d i t i o -n a l l y, st u d ie s i-n m ic e a n d r at s h a ve in d ic a t e d t h a t U V ligh t in d u ce s CYP1A1 in t h e skin an d in t h e live r (Ran n u g e t al., 1995).
Th e c a t a lyt ic a c t ivitie s a n d t h e m o d e o f i n d u ct io n o f CYP1A1 a p p e a r t o b e ve r y, we l l c o n s e r ved in h igh e r a n im a ls, in d ica t in g t h a t it h a s so m e im p o rt a n t p h ys io lo gic a l fu n ct io n . Th e act ivity a n d in d u cib ilit y p a tte rn in h u m an s o f t h is e n zym e , wh ic h fo r m s DN A-re a c t i ve m e ta b o lit es fro m PAH , is t h ere f o re o f gre a t im p o rt an ce wh e n assessin g th e ca n cer risk t o h u -m a n s. CYP1A1 is co n sid ered t o b e p ri -m a rily a n e x t r a h e p a t ic e n zym e in h u m a n s. It is in d u ce d in lu n g, in lym p h o cyt e s, a n d in p lac e n t a a ft e r e x p o s u re t o PAH s a n d t ob a cco sm o ke (An t illa e t al., 1991).
• C Y P 2 D 6
Th e ge n e tic p o lym o rp h ism re lat e d t o t h e an ti-h y p e rt e n s i ve d ru g d e b r iso q u in e w a s t ti-h e firs t o n e d e scrib e d a ss o cia t in g t h e m e t ab o lism o f d r u gs w it h e xp re s sio n o f a P450 e n zym e . T h e ge n e CYP 2D 6 e n co d e s P 450IID 6 o r d e b r i s o-q u in e 4-h yd rox y l a s e, so m et im e s re f e r re d t o as P450d b l (Go n z a l e s, 1995).
-Cad. Saúde Púb lica , Rio de Jane iro , 14(Sup . 3):7-13, 1998
b r is o q u in e h yd ro xyla s e ac t ivit y (Hi r vo n e n , 1995). Th is p o lym o rp h ism h a s co n ve n t i o n a l l y b e e n d e t e r m in e d b y t h e a d m in is t r a t io n o f a t e s t d r u g (u s u a lly d e b r iso q u in e ) a n d s u b s e -q u e n t a n a lysis o f t h e u ri n a r y m e t a b o lic ra t i o. Ac c o rd in g t o t h a t, in d ivid u a ls h ave b e e n cla s-s ifie d as-s p o o r m et a b olize rs-s (PMs-s) or e xt e n s-sive m e t a b o l i ze rs (EMs) o f d e b r iso q u in e (Id l e , 1991). Usin g p o lym e rase ch a in rea ctio n (PCR)-b a s e d a n a lys is t o ge t h e r wit h t h e (re s t ri c t i o n f ra gm e n t le n gt h p o lym o r p h ism (RFLP) an aly-s i aly-s, t h e th ree m oaly-st co m m on d efect ive a llele aly-s o f CYP2D6 in Ca u casian s are CYP2D6A, a d ele tion o f A2637 in e xo n 5 ca u sin g a fra m e sh ift m u t a-t ion ; CYP2D6B, a a-tra n sia-tio n in vo lvin g G1934 a-t o A ca u sin g a s p lic in g d e fe ct a n d CYP 2D 6D, w h e re a d e le t io n o f th e e n t ire CYP2D 6 fu n c-t ion al ge n e h as occu rred (Ran n u g e c-t al., 1995). T h e re is a p ro n o u n ce d in t e re t h n ic d iffe r-e n cr-e in t h r-e d ist rib u t io n o f th r-e sr-e d r-e fr-ect a llr-e lr-e s, w h e re t h e CYP2D6B a n d CYP 2D6A a lle le s a re a lm o s t e xc l u s i ve ly p re s e n t in t h e Ca u c a s i a n p o p u lat io n . By con t ra st , t h e CYP2D6D alle le is m o re e ve n ly d ist rib u t e d b e twe en b la ck, Asia n , a n d Cau ca sia n p o p u lat ion s.
Se ve ra l st u d ie s h a ve sh own t h a t t h e e xt e n -s i ve m e tab o lize r (EM) p h e n o t yp e i-s a-s-so ciate d w it h in cre a se d r isk o f va r io u s ca n c e rs, e sp e -c ia lly t o b a -c-c o -s m o ke -in d u -c e d lu n g -ca n -ce r ( Ra u n io e t a l., 1995). Re ce n t ge n o t yp in g st u d -ie s h a ve e it h e r co n fir m e d (Hi r vo n e n e t a l., 1993) o r re fu t e d (Ra n n u g e t a l., 1995) su c h an a s s o c i a t i o n .
Ac c o rd in g t o Ra u n io et a l. (1995), t h e ove r-re p r-re se n t a t io n o f CYP2D 6 EM s a m o n g lu n g c a n c e r p a t ie n t s ca n b e e xp lain e d in t wo wa ys: firs t , t h e CYP2D6 m a y m e d iat e t h e a c t iva t i o n o f p ro c a rc in o ge n ic a ge n t s p re se n t in t o b a cco s m o k e . Th e d e m o n st ra t io n t h at CYP2D6 is ca -p a b le o f a ctivatin g t he t ob acco-s-p ecific -p ro c a rcin o gen 4(m et h ylin it ro s a m i n o ) 1 ( 3 p y ri d y l ) -1- b u t a n on e (NNK), d ire ct ly s u p p o r t s t h is h y-p o t h e s i s. Secon d , t h e CYP2D6 ge n e m ay b e in a lin kage d iseq u ilib riu m with th e ca u sative gen e.
• C Y P 2 E 1
Th e cyt o c h ro m e P4502E1 (CYP2E1) is a m a jo r e t h a n o lin d u cib le P450 iso zym e t h a t m e t a b o -l i ze s a wid e va riet y o f ch e m ica-ls with d iffe re n t s t ru c t u re s, p a rt icu la r ly sm a ll a n d h yd ro p h i l i c co m p o u n d s (Persson e t a l., 1993). To d a y, m ore t h a n 100 sp e cific su b s t ra t e s fo r CYP2E1 h a ve b e e n id e n t ifie d , su ch as b en ze n e, d im e t h yln it ro s o a m i n e, a n d vin yl ch lo rid e a ll o f ith e m p o -t en -tia lly im p or-ta n -t ca rcin oge n s (Ran n u g e -t al., 1995). CYP2E1 is lo ca lize d in se ve ra l d iffe re n t t i s s u e s, a m o n g t h e m t h e b ra in a n d lu n g, b u t
t h e h igh e st e xp re ss io n is in t h e live r. Th e re -gion a l d istrib u t io n o f CYP2E1 correla te s well to t h e a re a s wh e re t h e h e p a t ot o xic c h e m ic a ls, k n own t o b e a c t ivat e d b y CYP2E1, e xe r t t h e ir t oxic a ctio n (Per sso n et al., 1993).
Polym orp h ism o f CYP2E1 ge n e ha s re c e n t l y b e e n sh own t o b e on e o f t h e p o t e n t ia l in d ica -to rs o f a cy-to ch rom e P450-associat ed su scep ti-b ilit y t o ca n ce r in m a n (Hi rvo n e n e t al., 1993). Ge n e tic p olym o rp h ism , id en t ifie d b y RFLP u s-in g t h e re s t r ic t io n e n z ym e D ra I, Ps t 1, (R s a I) a n d Ta q Io f CYP2E1 ge n e, h a ve b e e n sh ow n t o b e a sso ciat ed wit h h u m an can ce r. In Ja p a n e s e, th e d istr ib u t io n of t wo D ra Ige n ot yp e s a m o n g lu n g ca n cer ca se s is sign ifican t ly d iffe ren t fro m t h a t a m o n g co n t ro ls a n d a n a s so cia t io n wa s fo u n d t o e xis t b e t w e e n t h e a m o u n t o f life lon g sm o kin g e xp os u re a n d t h e d ist r ib u t io n o f t h e
D ra Ige n o t yp e s a m o n g lu n g ca n ce r p a t ie n t s. Su b seq u en t stu d ies h ave revealed p rofou n d eth -n ic d iffe re -n ce s i-n t h e fre q u e -n cie s of t h e p o ly-m o r p h ic alle le s. In a s t u d y in vo lvin g Fi n n i s h lun g can cer p a tie n ts, h om ozygosity fo r th e ra re
D ra Ia lle le (m in o r, alle le C) w a s fo u n d t o b e le ss fre q u en t t h a n in t h e Ja p an e se p o p u la t ion , a n d t h e d ist r ib u t io n wa s sim ilar a m o n g lu n g ca n cer p atien t s a n d t he ir con t ro ls (Hi r vo n en et al., 1993) wh ich is in agree m e n t with t h e re s u l t s ob tain e d b y Pe rsson et al. (1993).
An o t h e r CYP 2E1 p o lym o r p h ism is id e n t i-fied by RFLP, u sin g Ps t 1(R s a 1) is also id en t ifie d . Th is re s t rict io n sit e is lo cat e d in t h e t ra n s c ri p t io n re gion o f t h e ge n e a n d m igh t h a ve a b io -logica l e ffect (Ka to et a l., 1994).
G S Ts genes and polymorphism
Th e glu t a t h io n e S-t ra n s f e ra se s (GSTs ) a re a fa m ily o f m u lt ifu n c t io n a l d im e r ic p ro t e i n s wh ich ca n co n ju gat e e le c t ro p h ilic m o le cu le s wit h glu t a t h io n e t o re n d e r t h em less t oxic a n d h a ve th e a d d it ion al p ro p e rty o f act in g a s b in d -in g p r ot e -in s o r liga n d -in s -in t h e live r (Id l e , 1991). Ca rcin o ge n s d et o xifie d b y GSTs in clu d e p o l yc yc lic a r o m a t ic h yd ro ca rb on s p re s e n t in th e d ie t a n d to b a cco sm o ke.
H u m a n GSTs h a ve b e e n gr o u p e d o n t h e b a sis of t h eir iso e lect ric p oin t s in t o alp h a (b a -sic) m u (n e ar- n e u t ra l) an d th e ta (a cid ic) fo rm s. Mem b ers of th e sam e class sh are 75-95% a m i n o acid sim ilari t y, b ut b et wee n cla sse s t h e id en t it y d ro p s t o 25 30%. It a p p e a rs t h a t wh ile a ll h u -m a n live rs exp re ss s eve ral alp h a fo r-m s o f GST, o n ly a b o u t 50% o f t h e m e xp re ss a m u iso z y m e ( Ma n n e rvik et a l., 1992).
Cad. Saúde Púb lic a, Rio de Jane iro , 14(Sup . 3):7-13, 1998
i n h e r it t w o d e ficie n t a lle le s a n d a re h o m o z y-go u s fo r th e n u ll alle le (Ra u n io e t al., 1995). T h e GSTM 1 a ct ivit y is la ckin g in a b o u t 38-65% o f d i f f e re n t e t h n ic p o p u la t io n s (Bo a rd e t a l., 1 9 9 0 ) .
As DNA ad d u ct s form atio n is in verse ly co r-re la t e d w it h GSTM1 e xp r-re s sio n , in d ivid u a ls m issin g GSTM1 m a y h a ve re d u ce d cap a cit y t o d e t o xify re a c t i ve m e t a b o lit e s (Se i d e g a rd e t a l., 1990; Na ka jim a e t a l., 1995). H i r vo n e n e t a l. (1993) re p o r t e d t h a t t h e GSTM 1 n u ll (GSTM1 0/ 0) ge n o typ e is associa t ed with in cre a se d ri s k of sq u a m ou s ce ll ca rcin o m a of t h e lu n g. Ot h e r s fo u n d a n as so cia t ion b e t we e n a d e n o ca rc i n o -m a a n d la ck o f GSTM1 e xp re ssio n (Se i d e g a rd e t al., 1990; Be ll e t a l., 1993). Howe ve r, Bro c k-m o ller e t a l. (1993) d id n o t fin d an y sign ifica n t c o r re la tio n b e t we e n GSTM 1 ge n o t yp e s a n d va rio u s t yp es o f lu n g ca n cer.
In d ivid u a ls la ckin g GSTM1 c o u ld b e a t a g re a t e r risk fo r d e ve lo p in g ca n ce r d u e t o d e fi-cien t d et oxificat ion p ro c e s s e s. T h e re a re, h ow-e vow-e r, sow-evow-e ra l p u tat ivow-e co n fo u n d in g fa cto rs t h at a re kn own t o affect t h e p h e n ot yp e, su ch a s e n -v i ro n m e n t a l e xp o su re s, n u t r it io n a n d d iffe r-en ce s in sm okin g h a b it s. Stu d ie s co n d u ct ed b y H i rvon e n e t al. (1993) wit h Fin n ish lu n g can ce r p a t ie n t s s h owe d t h a t 62 % o f in d ivid u als wit h sq u a m o u s c e ll ca rc in o m a o f t h e lu n g we re o f t h e GSTM1 n u ll ge n o t yp e c o m p a re d with 44% in t h e c o n t ro l p o p u la t io n . La ck o f t h e GSTM1 ge n e is a ls o as s o cia t e d w it h su sc e p t ib ility t o b l a d d e r, skin a n d co lon can cer s (Ra u n io e t al., 1 9 9 5 ) .
Na ka jim a e t a l. (1995) re ce n t ly re p o rt e d t h at p a t ie n t s la c kin g t h e GSTM1 ge n e h a ve a le ss e fficie n t p u lm o n a ry d e toxificat io n syste m th a n GSTM1 p o sitive gen ot yp es d u e t o an ove r-all lo w GST a ct ivit y. Su ch in d ivid u a ls wit h t h e GSTM 1 n u ll ge n o t yp e we re also fo u n d to e x-p re ss s ign ifica n t ly lowe r le ve ls of t h e µ -c la ss GSTM3-3 in th e lu n g th an in d ivid u als wh o p ossessed t h e GSTM1 ge n e. An t illa e t a l. (1991) re p o r t e d t h at all GST e n zym e s a re m o st a b u n -d a n t in t h e cilia t e -d e p it h e liu m of t h e b ro n c h i , a n d le ast in th e d istal air w a y s. Fu rt h er an alysis o f t h e lu n g tis su es b y h igh p e r f o rm a n ce liq u id c h ro m a t o g ra p h y d e m o n st ra t e d t h a t GST s u b -u n its A1, A2, M1, M3 & P1 we re p resen t in va r y-in g a m o u n t s wit h t h e d iffe re n t y-in d ivid u a ls st u d ie d . Th e la ck o f GSTs (e sp e cially a m o n g GST n u ll in d ivid u als) in t h e b ro n ch ia l w a ll c ou ld fa vor t h e d e ve lo p m e n t o f SCC w h ich u su sa lly or igin ate s from th e b ro n chia l e p ith eli-u m (An tilla et a l., 1991). Howe ve r, in view of th e re l a t i ve ly h igh co n t e n t o f GSTP 1 a n d GSTM3 an d low c o n t en t of GSTM1 in t h e lu n g, t h e in -flu e n ce o f GSTM1 o n su sce p t ib ilit y t o lu n g
ca n ce r p ro b a b ly o rigin a t es in e xt ra p u l m o n a ry c o m p a r tm en t s su ch a s th e live r wh ere GSTM1 is t h e o n ly ac t ive GST d e t e ct e d (Ra n d e ra t h e t al., 1989). A con sid erab le am o u n t o f PAH s fro m t o b a c co sm o ke p a s se s in t o syst e m ic b lo o d t o b e a ct iva t e d o r d e t o xifie d in e xt ra p u l m o n a r y t i s s u e s, e.g. live r, a n d ca u se s ca n ce r in n on -p u l m o n a ry t issu es (Ra n d e ra th e t al., 1989). It is t h e re f o re re a son ab le t o a ssu m e th at m o re ca r-cin o ge n ic e le c t ro p h ile s e n t e r t h e circ u l a t i o n f ro m t h e live r in GSTM1 n u ll in d ivid u als co m p a re d t o GSTM1 +/ + in d ivid u a ls. Th is a ssu m p -t io n is a ls o co n s is -t e n -t w i-t h -t h e a sso cia-t io n o f t h e GSTM1 n u ll ge n ot yp e with in crea sed risk o f o th e r ca n cer s su c h as t h e st o m ach , co lo n , u ri-n a ry b la d d e r ari-n d la ryri-n x (La fu eri-n t e e t a l., 1993; An war e t a l., 1996).
Glu t a t h io n e S-t ra n s f e rase t h e ta (GSTT1) is an ot h e r p olym orp h ic ge n e w h ich is d e le t e d in 38% o f a Eu rop e a n p o p u lat io n (Pe m b le e t al., 1994) a n d 20% in No rt h Am e rica n s (Ne lso n e t a l., 1995). Th e d e ficie n cy is h igh ly c o rre l a t e d with t h e in ab ility to con ju gat e glu tath io n e wit h sm a ll m ole cu la r weigh t t ox i c a n t s. Howe ve r, its a sso c ia t io n wit h t h e d e ve lo p m e n t o f ca n ce r h a s n o t b ee n a d eq u a t ely in ve s t i g a t e d .
Sin ce m etab olism of ch em icals re q u i re s th e i n t e ractio n s wit h m u lt ip le ge n es, in ve s t i g a t o r s h a ve b e gu n t o d o cu m e n t t h e in h e r it an ce o f m u lt ip le p olym o rp h ic ge n e s in t h e d e ve l o p -m e n t o f ca n cer (Ra u n io e t a l., 1995).
Th e fre q u e n cy o f t h e GSTT1 n u ll ge n o t yp e h a s n o t ye t b e e n st u d ie d e xt e n sive l y. T h re e s t u d ie s h a ve re p o rt e d t h a t t h e n u ll a lle le fre q u e n cy ra n ge d b e twe en 20.4% to 38% d ep e n d -in g o n t h e size a n d e t h n icit y o f t h e st u d ie d p o p u la t io n (Pe m b le e t a l., 1994; El - Ze in e t a l., 1997; Ab d e l - Ra h m a n e t a l., 1996).
Th e a ss o cia t io n b e t we e n t h e GSTT1 d e le -t io n a n d in cre as e d in cid e n ce o f lu n g ca n c e r ca n b e explain ed in d iffere n t ways. GSTT1 d efic ie n eficy wa s s h o wn t o b e re sp o n sib le fo r in -c re a se d in d u -ct io n o f -ch ro m o so m a l d am a ge b y e p o xid e su b st ra t e s su ch a s e t h yle n e o xid e i n v i t ro( Ha llier et a l., 1993).
Cad . Saúde Púb lic a, Rio de Jane iro , 14(Sup. 3):7-13, 1998
t h at a re su b st ra t es for b ot h GSTM1 an d GSTT 1 ge n e p ro d u c t s. T h e re f o re, t h e com b in e d p o ly-m o rp h ic d e le t io n o f t h e tw o ge n e s is e xp e ct e d t o in t eract p osit ive ly t o m od ify ca n ce r risk.
M olecular epidemiology in Brazil
Th e m o lec u la r e p id em io logy in Bra zil is a n e w fie ld o f e xp e rt i s e. De s p i t e , a gre at in t e re st h a s b e e n e m e rge d in sc ie n t ific co m m u n it y. In o u r l a b o ra t o r y we are cu r re n t ly se a rc h in g t h e lin k b e t we e n so m e t yp e s o f c a n ce r a n d e n viro n -m e n t a l e xp o s u re s. To b e t t e r u n d e rs t a n d t h a t re l a t i o n s h i p, we m u st kn ow th e b razilie n d istri-b u t io n co n ce r n in g t h e xe n o istri-b io t ic m e t a istri-b o liz-in g ge n e s, su ch a s t h e CYPs a n d GSTs fa m ily. Ac c o rd in g o f t h at , t h is is ou r first p ri o rity o n go-in g p roject we are con cen tra ted go-in ord er to h a ve t ho se d a ta soo n . Alo n g wit h, we a re co n d u ctin g t wo d ifferen t st ud ie s re g a rd in g ge n et ic su scep -t ib ili-t y an d e n viro n m en -ta l-can cer re l a -t e d .
On e o f t h em co n ce rn s th e lin k b et we en h e-p at o c e llu la r ca rc in o m a (H CC) a n d t h e e-p oly-m o rp h ic a ct iva t in g a n d d e to xifyin g ge n e s. T h e H CC is t h e m o st fre q u e n t m align an t t u m o r o f t h e live r a n d t h e co m m on e st ca n ce r occu rri n g in m a le s in t h e wo rld . Th e a n n u a l in cid en ce o f
t h e d ise as e w o r ld wid e is e s t im a t e d t o b e o n e m illio n ca se s (La u & La i, 1990). T h e re is a s t ron g an d sp e cific associat io n b e twee n ch ro n -ic h e p a t it is B a n d C vir u s in fe ct io n a n d H CC . He p a t ic cirrh osis d u e to a lcoh o l is a n o t h e r a e -t io lo gic fa c-t o r in crim in a -t ed . Howe ve r, ge n e -t ic p re d isp o sit io n m a y also a ct t o p r o m o t e h e p a -t o c a rc i n o g e n e s i s, o n ce h e avy d r in ke r s d o n o -t a lwa ys d e ve lo p alco h o lic live r d isea se ( Ts u t s u -m i e t a l., 1994) a n d p o ly-m o r p h is -m of C YP 2E1 m a y b e re la t e d t o live r d ise a s e in cid e n c e in Ja p a n e se p o p u latio n (Kat o e t a l.,1995).
Th e o t h e r o n go in g p ro je c t c o n ce r n s t h e st u d y o f c arc in o ge n -m e t a b oliz in g e n zym e s an d skin ca n cer. Th e gen e tic fa cto rs t h at m e d ia t e t h e p ia t h o ge n e sis of skin t u m or s is u n -k n own (Le a r e t a l., 1996). S-kin ca n ce rs are t h e m o st c o m m o n t yp e of h u m a n n e o p la s ia . Ex-c e s s i ve u lt ra viole t irra d iat io n , with Ex-con seq u en t re a c t i ve oxyge n sp e cie s a tt ac k o n ta rge t m o le -cu le s s u c h a s DN A, a p p e a rs t o b e t h e m a jo r c a u s e, a lt h ou gh t h e e ffe ct s o f U V a re co m p le x a n d o t h e r fa c to rs, in clu d in g so o t , ciga re t t e s m o k e , a n d a rse n ic a re re l e van t (H e a g e rt y e t a l., 1994). Co n s e q u e n t l y, p o lym o rp h is m a sso cia te d with im p aire d act iva t io n an d d et ox i f i c a -t io n m a y d e -t e r m in e su s ce p -t ib ili-t y -t o m u l-t ip le skin ca n cers.
R e f e re n c e s
ABDEL- RAHM AN , S. Z.; AN WAR, W. A.; ABDEL-AAL, W. E.; GH ON EIM , M . A. & AU , W. W., 1996. T h e CYP2D6 e xt en sive m e t a b o lize r ge n o t yp e is a sso -cia t e d w it h in c re a s e d ris k fo r b la d d e r ca n ce r.
Can cer Letter, 107:229- 233.
A N T I L LA, S.; H IETAN EN , E. & VA I N I O, M ., 1991 . Sm okin g a n d p er i p h e ra l t yp e o f ca n cer a re re l a t-e d t o h igh lt-evt-e ls of p u lm on ary cyt o ch ro m t-e – P450 IA in lu n g ca n ce r p at ie n t s. In t ern ation a l Jo u r n a l Ca n c e r, 47:681-685.
A N WAR, W. A.; ABD EL-RAH MAN , S. Z.; EL- ZEIN , R. A.; M OSTA FA, H . M . & AU, W. W., 1996. Ge n e t i c p o lym o r p h is m o f GSTM 1, CYP 2E1 a n d CYP 2D 6 in Egyp t ia n b la d d e r c a n ce r p a t ien ts. Ca rc i n o g e n -e s i s, 17:1923-1929.
BELL, D. A.; TAY LOR, J. A.; PAULSON, D. F.; RO B E RT-SON, C. N.; MOHLER, J. L. & LUCIER, G. W., 1993. Ge n e tic risk an d ca rcin oge n e xp osu re: a co m m o n i n h e rit e d d e fe ct o f t h e c arcin o ge n m e t ab o lism o f ge n e glu ta t h io n e S-t ra n s f e ra se M 1(GSTM 1) t h a t i n c re a se s su sc e p t ib ilit y t o b la d d e r c a n ce r. Jo u r-n al Natior-n al Car-n cer Ir-n s t i t u t e, 85:1158-1164. B OA R D, P. G.; COGGAN, M .; JOH N STON, P.; ROSS, V.
& SUZUKI, T. G. W., 1990. Ge n e t ic h e t e r o g e n e i t y o f t h e h u m a n glu ta th io n e t ra n s f e ra se : a co m p le x o f g e n e fa m ili e s. Ph arm a cologi cal Th era p y, 48 : 3 5 7 - 3 6 9 .
BOIS, F.; KROWECH , G. & ZEISE, L., 1995. Mo d e l i n g h u m a n in t er in d ivid u al va r iab ility in m e t a b o lism
a n d r isk: t h e e xa m p le o f 4-a m in o b ip h e n yl. R i s k An a l y s i s ,1 5 : 2 0 5 - 2 1 3 .
B ROCKMOLLER, J.; KERB, R.; DRAKOOULIS, N.; S TA F F E L D T, B. & RO OTS, T., 1993. Gl u t a t h i o n e S -t ra n s f e ra se M1 an d i-t s va ria n -t A a n d B a s h os-t fa ct o rs o f b la d d e r ca n cer su s cep ct ib ilict y: a cas e co n -t ro l s-tu d y. Can cer Re s e a rc h, 54:4103-4111. CO N F O RT I - F ROES, N.; EL-ZEIN, R.; ABD
EL-RAH-M AN, S.; SWISCHENBERGER, J. & AU , W. W., 1997. Pre d is p o s in g ge n e s a n d in cre a s e d ch ro m o s o m e a b e r ra tion s in lu n g c an ce r ciga re tte sm o ke rs. M u -tation Re s e a rc h, 379:53-59.
EL-ZEIN , R.; CO N F O RT I - F ROES, N . & AU, W. W., 1997. In t e ra c tion s b e t we en ge n e t ic p re d isp o sit io n a n d e n v i ro n m e n t a l t o xic an t s fo r de ve lop m e n t o f lu n g c a n c e r. En v i ron m en ta l M olecu lar Mu t a g e n e s i s, 3 0 : 1 9 6 - 2 0 4 .
EUBAN KS, M., 1994. Bi o m a rker s: t h e clu e s to ge n e t ic s u s c e p t i b i l i t y.En v i ron m en tal Health Pe r s p e c t i ve s, 1 0 2 : 5 0 - 5 6 .
G O N ZALES, F. J., 1989. Th e m o le cu la r b io lo gy o f c y-t o c h r o m e P450s. Ph a r m a c o l o gy Re v i ew, 40:243-2 8 8 .
G O N ZALES, F., 1995. Ge n et ic p olym o rp h ism a n d ca n -c e r s u s-c e p t ib ilit y: Fo u rt e e n t h Sa p p o ro Ca n -c e r Se m i n a r. Can cer Re s e a rc h, 55:710-715.
Cad . Saúd e Púb lic a, Rio de Jane iro , 14(Sup. 3):7-13, 1998
HARRIS, C. C., 1989. In t e rin d ivid u al va ria t io n a m o n g h u m a n s in ca rc in o ge n m e ta b o lism , DNA a d d u ct f o r m a t io n a n d DN A re p a i r. Ca rc i n o g e n e s i s, 10: 1 5 6 3 - 1 5 6 6 .
HARRIS, C. C., 1991. Ch e m ic al a n d p h ysica l ca rc i n o-ge n e s is: a d va n c e s a n d p e rs p e ct ive s. Can cer Re-s e a rc h, 51:5023-5044.
HALLIER, E.; LA N G H O F, T.; DAN NAPPEL, D.; LEUT-BECHER, M.; SCHROEDER, K.; GOERGENS, H. W. ; MULLER, A. & BOLT, H. M ., 1993. Po l y m o r p h i s m of glu tat h io n e con ju gat io n of m et h yl b ro m i d e, et h-ylen e oxide a n d dich lo ro m et ha n e in h um an bloo d: in flu e n ce o n t h e in d u ct io n o f s ist e r- c h ro m a t i d e xc h a n g e s. Arc h i ves of Tox i c o l o gy, 67:173-178. H E AG E RT Y, A.; FITZG E R A L D, D.; SMITH , A. &
ST RAN GE, R., 1994 . Glu t a t h io n e S-t ra n s f e ra s e GSTM 1 p h en o typ es a n d p rot e ct ion a gain st cu ta -n e o u s tu m o rs. La n c e t, 343:266-268.
H I RVONEN , A., 1995. Gen e tic fa cto rs in in d ivid u al re -sp o n se s t o e n viro n m e n t a l e xp o s u r e s. Jou rn al of Occu p a tion a l a n d En v i ron m en ta l M e d i c i n e, 37: 3 7 - 4 3 .
H I RVON EN , A.; HU SGAFVELPU RSIAIN EN , K.; AN -T I L LA, S.; KARJALAIN EN , A. & VAIN IS, H ., 1993. Th e h u m a n CYP2E1 gen e a n d lu n g ca n ce r: D ra I a n d Rs a I r e s t r ict io n fra gm e n t le n gt h p o lym o r-p h ism in a fin n ish st u d y r-p or-p u la tio n . Ca rc i n o g e n -e s i s, 14:85-88.
ID LE, J., 1991. Is e n viron m e n t al carcin o ge n e sis m o d-u la te d b y h o s t p o lym o rp h ism ? M u t at i on Re-s e a rc h, 247: 259-266.
K ATO, S.; O ND A, M .; M ATSUKU RA, N.; TO K U N AG A , A.; TAJIRI, T.; KIM, D. & YA M A S H I TA, K., 1995. Cy-t o c h ro m e P450 2E1 ge n e Cy-t ic p o lym o rp h ism in a c a s e - c o n t ro l stu d y o f gast ric ca n ce r a n d live r d is-e a s is-e.Ph a r m a c o g e n e t i c s, 5:141-144.
K ATO, S.; SHIELDS, G.; CAPORASO, N. & SU GIMURA, H., 1994. An a lysis of cyt o ch r om e P450 2E1 ge n et ic p olym o rp h ism s in rela t io n to h u m an lu n g can -c e r. Can cer Ep i d e m i o l o gy, Bi o m a rk ers an d Pre-ve n t i o n, 3:515-518.
K ROEMER, H . & EICHELBAUM , M ., 1995. Mo l e c u l a r b a s e s a n d c lin ic a l co n s e q u e n ce s o f ge n e ti c c y-t o c h ro m e P450 2D6 p olym o rp h ism . Life Sci en ces, 5 6 : 2 2 8 5 - 2 2 9 8 .
LAFUEN TE, A.; PUJOL, F.; CARRETERO, P.; V I L LA, J. P. & GU CH I, A., 1993. H u m a n glu t a t h io n e S-t ra n f e ra se (GST ) d e fic ie n cy a s a m a rke r fo r t h e s u s-c e p t ib ilit y t o b la d d e r a n d la ryn x s-ca n s-ce r a m o n g s m o k e r s. Can cer Letter, 68:49-54.
LAU, J. & LAI, C., 1990. He p a t o c a rc i n o g e n e s i s. Tro p i-cal Ga s t ro e n t e ro l o gy, 11:9-24.
LEAR, J.; HEAG E RTY, A.; SMITH , A.; BOWERS, B. ; PAYN E, C.; SMITH , C.; JON ES, P.; GILFORD, J. & STRAN GE, R., 1996. Mu lt ip le cu t a n e o u s b asa l ce ll c a rc in o m a s : glu t a t h io n e S-t ra n s f e ra s e a n d c y-t o c h ro m e P450 p o lym o rp h ism s in flu e n ce y-t u m o r n u m b e rs a n d a ccru a l. Ca rc i n o g e n e s i s ,1 7 : 1 8 9 1 - 9 6 . MANNERVIK, B.; AWASTHI, Y. C.; BOARD, P. G.; HAYES, J. D.; D ILLIO, C.; BOA R D, P. G.; HAYES, J. D.; D IL-L I O, C.; KETTERER, B.; IL-LITOW S K Y, B.; MORG E N-STERN , R.; M U RAMATSU , M .; PEARSON , W. R.; PI C K E TT, C. B.; SATO, K.; WID ERSTERN , M . & WO L F, C. R., 1992. No m e n c l a t u re fo r h u m a n glu -ta th io n e t ra n s f e ra s e s. Bi o c h e m i s t ry Jo u r n a l, 282: 305-306.
M CD ONN ELL, M . W.; SCH EIMAN , J. & TRABER, P. , 1992. In d u ct io n o f cyt o c h r o m e P 450IA ge n e s (cYP1A) b y O m e p ra go le in h u m a n a lim e n ta ry t ra ct . Ga s t ro e n t e ro l o gy, 103: 1509-1515.
N AKAJIMA, T.; ELVORAARA, E.; AN TILLA, S.; HIRVO-NEN, A.; CAMU S, A. M .; HAYES, J. D., KETT E R E R , B., & VA I N I O, H., 1995. Ex p re ssio n a n d p o lym o r-p h is m o f glyt a t h io n e - S- tr a n s f e ra se in h u m a n lu n gs: r iks fact o rs in sm o kin g re la t e d lu n g ca n c er.
Ca rc i n o g e n e s i s, 16:707- 711.
N ATIONAL RESEARCH COUN CIL, 1987. Bi o l o g i c a l m a rkers in en viro nm en tal health re s e a rch . Co m m i t-tee o n Biolo gical Ma rkers o f t h e Nat ion al Re s e a rc h Cou n cil. En v i ron m en tal Health Pe r s p e c t i ve s, 74:3-9. NELSON , H. H.; WEIN CKE, J. K.; CH RISTIAN I, D. C.; CHENG, T. J. & KELSEY, K. T., 1995. Et h n ic d iffe re n cre s in th re p rre valren cre of t h re h o m o zygo u s d re lret -e d g-e n o t yp -e o f glu t a t h io n -e S-t ra n s f -e r a s -e t h -e ta .
Ca rc i n o g e n e s i s, 16:1243-1245.
P EM BLE, S. ; SCH ROEDER, K. R.; SP EN CER, S. R.; M EYER, D. J.; H ALLIER, E.; BOLT, H. M.; KETT E R-ER, B. & TAY LOR, J. B., 1994. Hu m a n Gl u t a t h i o n e S - t ra n s f e ra se t h e t a (GSTT1): c DN A c lo n in g a n d t h e ch a ra c t e riza tion o f a ge n e t ic p o lym o rp h is m .
Bioch em ical Jo u r n a l, 300:271-276.
PERSSON, T.; JOH AN SSON , T.; BERGLING, H .; M AR-JA-LIISA, D. & SEIDEGARD, J., 1993. Ge n e tic p oly-m o rp h isoly-m of cyt oc h ro oly-m e P 4502E1 in a Swe d i s h p o p u la t io n . Fe d e rati on of Eu ropea n Bi o c h e m i s t ry S o c i e t i e s, 319:207-211.
R A N D E R ATH, E.; MILLER, R. H .; M CHAL, D.; AV I TTS , T.; DUNSFOR, H. A. & RAND ERATH, K., 1989. Co-va le n t DN A d a m a ge in t iss u es o f ciga re t te sm o k-ers as de t erm in ed by 32P p ostlab e llin g a ssa y. Jo u r-n a l of th e Natior-n a l Car-n cer Ir-n s t i t u t e, 81:341-347. RANNUG, A.; ALEXANDRIE, A. K.; PERSSON, T. & IN
-G E L M A N - S U N D B E R-G, M ., 1995. -Ge n e t ic p o ly-m o r p h isly-m o f c yt o c h r o ly-m e s P 450 1A1, 2D6 a n d 2E1 : re gu la t io n a n d t o xic o lo gic a l s ign ifica n ce .
Jou rn al of Occu p ati on al an d En v i ron m en tal M e d-i c d-i n e, 37:25-36.
R AU N I O, H.; HUSGAFNEL-PURSIANINEN, K.; ANTIL-LA, S.; HIETAN EN , E.; HIRVON EN , A. & PE L KO-NEN, O., 1995. Diagn osis of p olym orp h ism s in car-c i n o g e n - a car-c t i vat in g an d in a car-ctiva t in g e n zym es a n d ca n ce r su sce p tib ility: a re v i e w. Ge n e, 159:113-121. S E I D E G A R D, J.; P E RO, R. W.; M ARKOWITZ, M .;
ROUCH, G.; MILLER, D. G. & BEATTIE, E. J., 1990. Iso e n zym e (s) o f g lu t a t h io n e tr a n s f e ra se (c la ss Mu ) a s a m a rke r fo r t h e su sce p tib ility to lu n g can -c e r: a follow u p st u d y. Ca rc i n o g e n e s i s, 11:33-36. SH IELD S, P. G., 1994. P h a r m a c o ge n e t ics : D e t e c t i n g
s e n s i t i ve p op u la tion s. En v i ron m en tal Health Pe r-s p e c t i ve r-s ,102:81-87.
TS U TSUM I, M .; TAKASE, S. & TAKAD A, A., 1994. Ge -n e t ic p o lim o rp h is m s o f cyt o ch ro m e P4502E1 t o t h e d e ve lo p m e n t o f a lco h olic live r d is ea s e. Ga s-t ro e n s-t e ro l o gy,1 0 6 : 1 4 3 0 - 1 4 3 5 .
U M E N O, M.; MCBRIDE, O.; YAN G, C.; GELBOIN , H. & G O N ZALEZ, F., 1988. Hu m a n e th a n o l- in d u cib le P450IIE1: com p le te gen e se qu en ce, p ro m o te r ch ar-a c t e rizar-at io n , ch r om o so m e m ar-a p p in g, ar-a n d cD NA-d i re ct eNA-d exp ressio n . Bi o c h e m i s t ry, 27:9006-9013. WO L F, C. R., 1986. Cy t o c h r o m e P 450s: a m u lt ige n e
