Ho me o box ge nes: a mo le cu lar link bet we en de ve lop ment
and can cer
Ge nes ho me o box: uma re la ção mo le cu lar en tre o de sen vol vi men to e o cân cer
Fa bio Da u mas Nu nes*
Fer nan da Cam pos Sou za de Alme i da**
Re na ta Tuc ci***
Su za na Can ta nhe de Orsini Machado de Sou sa****
AB STRACT: Homeobox genes are reg u la tory genes en cod ing nu clear pro teins that act as tran scrip tion fac tors, reg u lat ing as pects of morphogenesis and cell dif fer en ti a tion dur ing nor mal em bry onic de vel op ment of sev eral an i mals. Ver te -brate homeobox genes can be di vided in two subfamilies: clus tered, or HOX genes, and nonclustered, or di ver gent, homeobox genes. Dur ing the last de cades, sev eral homeobox genes, clus tered and nonclustered ones, were iden ti fied in nor mal tis sue, in ma lig nant cells, and in dif fer ent dis eases and met a bolic al ter ations. Homeobox genes are in volved in the nor mal teeth de vel op ment and in fa mil ial teeth agenesis. Nor mal de vel op ment and can cer have a great deal in com mon, as both pro cesses in volve shifts be tween cell pro lif er a tion and dif fer en ti a tion. The lit er a ture is ac cu mu lat ing ev i dences that homeobox genes play an im por tant role in oncogenesis. Many can cers ex hibit ex pres sion of or al ter -ation in homeobox genes. Those in clude leukemias, co lon, skin, pros tate, breast and ovar ian can cers, among oth ers. This re view is aimed at in tro duc ing read ers to some of the homeobox fam ily func tions in nor mal tis sues and es pe cially in can cer.
DES CRIP TORS: Ge nes, ho me o box; Ne o plasms; Growth & De ve lop ment.
RE SU MO: Os ge nes ho me o box são ge nes re gu la do res que co di fi cam pro te í nas nu cle a res as qua is atu am como fa to res de trans cri ção, re gu lan do vá ri os as pec tos da mor fo gê ne se e da di fe ren ci a ção ce lu lar du ran te o de sen vol vi men to em bri o -ná rio nor mal de di ver sos ani ma is. Os ge nes ho me o box de ver te bra dos po dem ser sub di vi di dos em duas fa mí li as: os agru pa dos, ou HOX, e os não agru pa dos, ou di ver gen tes. Du ran te as úl ti mas dé ca das, vá ri os ge nes ho me o box, agru pa dos e não agru pa dos, fo ram iden ti fi ca dos em te ci dos nor ma is, em cé lu las ma lig nas e em di fe ren tes do en ças e con di ções me ta bó li cas. Os ge nes ho me o box es tão en vol vi dos, por exem plo, no de sen vol vi men to nor mal do den te e em age -ne si as den tá ri as de ocor rên cia fa mi li ar. O de sen vol vi men to nor mal e o cân cer têm mu i to em co mum, já que am bos en vol vem pro li fe ra ção ce lu lar e di fe ren ci a ção. A li te ra tu ra tem mos tra do um nú me ro cada vez ma i or de tra ba lhos re la ci o nan do os ge nes ho me o box à on co gê ne se. Mu i tos ti pos de cân cer exi bem ex pres são ou al te ra ção nos ge nes ho me o -box. Eles in clu em le u ce mi as, cân cer de có lon, pele, prós ta ta, mama e ová rio, en tre ou tros. Esta re vi são ob je ti va le var os le i to res a co nhe cer al gu mas das fun ções da fa mí lia ho me o box nos te ci dos nor ma is e es pe ci al men te no cân cer.
DESCRITORES: Genes homeobox; Neoplasias; Crescimento & desenvolvimento.
INTRO DUC TI ON
Homeobox genes are mas ter de vel op ment con trol
genes that act at the top of ge netic hi er ar chies reg u lat
-ing as pects of morphogenesis and cell dif fer en ti a tion in
an i mals
24. These genes were first dis cov ered in the fruit
fly Drosophila
22and iden ti fied as genes whose mu ta
-tions cause body seg ment trans for ma tion, also known
as homeotic trans for ma tion. This phe nom e non con
-sists of the trans for ma tion of one part of the body into
an other, e.g. a fly with four wings in stead of two.
Homeobox fam ily of genes en codes reg u la tory pro
teins con trol ling ba sic de vel op men tal pro cesses in sev
-eral tis sues, in clud ing orofacial tis sues
33. They con tain
a com mon 180nucleotide se quence (homeobox) cod
-ing for spe cific nu clear pro teins (homeoproteins) that
act as tran scrip tion fac tors. The homeobox se quence
en codes a 60-aminoacid do main, the homeodomain,
re spon si ble for DNA bind ing
8,11,32. Struc tural anal y ses
have shown that the homeodomain con sists of a he
-lix-turn-helix mo tif that binds the DNA by in sert ing the
rec og ni tion he lix into the ma jor groove of the DNA and
its amino-terminal arm into the ad ja cent mi nor
groove
13. The spec i fic ity of this bind ing al lows
homeoproteins to ac ti vate or re press the ex pres sion of
bat ter ies of down stream tar get genes
21. Homeobox are
also un der reg u la tion of some pro teins, such as the
sig nal ing pro teins Sonic hedge hog (SHH), fibroblast
growth fac tor (FGF) and bone morphogenetic pro tein
(BMP). The homeobox were shown to oc cur in all
Metazoa, rang ing from sponges to ver te brates and also
plants and fungi
6.
This re view aims at in tro duc ing read ers to some of
the homeobox fam ily func tions in nor mal tis sues and
es pe cially in can cer de vel op ment, which could be of
valu able clin i cal in ter est in the near fu ture.
HO ME O BOX GE NES IN DE VE LOP MENT
The fam ily of ver te brate homeobox genes can be di
-vided in two subfamilies: a) the clus tered homeobox
genes, known as HOX genes or class I; and b) the
nonclustered, or di ver gent homeobox genes.
The HOX fam ily plays a fun da men tal role in the
morphogenesis of ver te brate em bryo cells, pro vid ing
re gional in for ma tion along the main body axis
11,24. This
fam ily is struc tur ally and func tion ally ho mol o gous to
the homeotic com plex (HOM-C) of
Drosophila. There
are at least 39 genes in mice (HOX genes) and hu mans
(HOX genes) or ga nized in four genomic clus ters of
about 100 kb in length called HOX loci. Each clus ter is
lo cated in a dif fer ent chro mo some (HOX-A, HOX-B,
HOX-C and HOX-D, re spec tively at 7p, 17p, 12p and
2p) and com prises 9 to 11 genes ar ranged in a ho mol o
-gous se quence or ga ni za tion (Fig ure 1)
7,8. HOX genes
have been re ported as im pli cated in angiogenesis and
wound re pair
36, in func tions of the fe male re pro duc tive
tract
35, and in pul mo nary hy per ten sion and em phy
-sema
14. Mu ta tions in HOX genes may yet par tic i pate in
hu man mal for ma tions, e.g., HOXA13 gen er ate the
hand-foot-genital syn drome
15, HOXB1 gen er ate the
Mowat-Wilson syn drome
39, and Duanes Re trac tion
Syn drome (DRS) links to the HOXD clus ter
1. Also,
Ingram et al.
16(2000) re ported ev i dence of an in ter ac
tion be tween HOXA1, HOXB1, and gen der in sus cep ti
-bil ity to au tism spec trum dis or ders.
The nonclustered genes are a large num ber of
genes scat tered through out the ge nome that, nev er
-the less, can be or ga nized in dis tinct fam i lies based on
their homologies and func tional sim i lar i ties. Some of
the fam i lies in clude paired (PAX), orthodenticle (OTX),
mus cle seg ment (MSX), distalless (DLX), cau dal (CDX),
and empty spi ra cles (EMX) homeobox genes, among
oth ers
24.
Dur ing the last de cades, sev eral homeobox genes,
clus tered and nonclustered, were iden ti fied in nor mal
tis sue, in ma lig nant cells, and in dif fer ent dis eases and
met a bolic al ter ations
7. PAX genes are the homeobox
fam ily with the stron gest con nec tions with hu man dis
-eases. PAX2 has been im pli cated in breast can cer
34, re
-nal hypoplasia and re -nal dis ease
26; PAX3 has a role in
rhabdomyosarcomas
2and mel a no mas
31; PAX5 de ter
-mines the iden tity of B cells
28. MSX homeobox genes
are in volved in the nor mal teeth de vel op ment and in
fa mil ial teeth agenesis
9.
HO ME O BOX AND CAN CER
Oral can cer is, re spec tively, the fifth and sev enth
most com mon can cer for male and fe male in the gen
-eral pop u la tion. About half of the pa tients af flicted
will die within five years of di ag no sis
38. Squamous cell
car ci no mas ac count for 96% of all oral can cers. Dur
-ing the last de cade, much prog ress has been made in
de lin eat ing the mo lec u lar al ter ations that lead to
oncogenic transfor mation
11. Sev eral stud ies in di cate
that al co hol and to bacco use are im por tant fac tors
caus ing oral can cer
19,38. A ge netic pre dis po si tion has
been sug gested, since the ma jor ity of the pop u la tion
ex posed to the men tioned risk fac tors does not de
-velop oral can cer. Also, spo radic cases of oral can cer
oc cur in young adults, non-users of any iden ti fi able
car cin o gen, and there have been re ports of fam ily his
-tory in volve ment
23. To day, many ge netic events
caused by chro mo somal al ter ations or mu ta tions
have been pro posed to un der line the pro gres sion of
oral tu mors
38. The de vel op ment reg u la tory genes
4,11with oral can cer. Re cently, we were able to show that
four dis tinct squamous cell car ci noma cell lines ex
-press HOX genes dif fer ently from the con trol cells and
tis sue
27.
Can cer and nor mal de vel op ment have a great deal
in com mon, as both pro cesses in volve shifts be tween
cell pro lif er a tion and dif fer en ti a tion
4. Re cent re search
has dem on strated that im proper reg u la tion of de vel
-op ment genes may re sult in can cer. How ever, there is
a lot to be learned about the in ter play that ex ists be
-tween de vel op ment, cell cy cle, apoptosis and can cer.
Many can cers ex hibit ex pres sion or al ter ation in
homeobox genes. They in clude leu ke mia, co lon, skin,
pros tate, breast and ovary can cers, among oth ers.
Re cently it was shown that loss of ex pres sion in hu
-man breast can cer of p53, a gene that pro tects cells
against ma lig nant trans for ma tion, may be pri mar ily
due to lack of ex pres sion of HOXA5
29. How ever, the
pre cise mech a nisms by which homeobox gene al ter
-ations lead to can cer are still un known
11.
The dem on stra tion of cell lin eage-specific pat terns
of HOX gene ac ti va tion in hu man and murine leu ke
-mic cell lines sup ports the hy poth e sis that HOX gene
ex pres sion can reg u late nor mal hematopoietic dif fer
-en ti a tion
21. Al tered ex pres sion of HOX genes lo cated
in HOXA and HOXB loci is of ten in volved in
leukemogenesis. The in fec tion of nor mal mar row cells
with a LTR/HOXB8 con struct, to gether with the ac
tion of the IL3 gene, was able to in duce myeloid leu
-ke mia in mice
24.
A genomic fu sion in frame be tween the nucleoporin
gene NUP98 and the HOXA9 gene was shown in three
pa tients with myeloid leu ke mia and translocation
t(7;11)
25. Chi me ric fu sion pro teins re sult ing from the
tran scrip tion ac ti va tor do main of one pro tein and the
DNA bind ing do main of an other dis play a high
oncogenic po ten tial. Other fu sions, as PBX1 to E2A
and HRX to nu clear pro teins, al ter the se
-quence-specific bind ing of HOX genes, di rect
homeoproteins to a dif fer ent tar get, and in duce
leukemogenesis
19. The lo cus HOXC is mainly im pli
-cated in lym pho mas. HOXC4, C5 and C6 are ex
pressed in non-Hodgkin lymphom s, dis play ing a type-
and site-restricted ex pres sion pat tern in both T- and
B-cell non-Hodgkin lym pho mas
3.
Ma jor dif fer ences in HOX gene ex pres sion are de
-tect able in pri mary solid tu mors (kid ney, co lon,
breast, pros tate and smal cell lung can cer) com pared
with the cor re spond ing nor mal adult or gans
7,20.
Misexpression of HOX genes is de tect able in met a
-static le sions re lated to the pri mary tu mor of or i gin
and the cor re spond ing nor mal tis sue, sup port ing the
hy poth e sis of an im pli ca tion of homeoproteins in can
-cer evo lu tion
10.
Overexpression of the homeobox gene HSIX1 in
MCF7 cells ab ro gated the G2 cell cy cle check point in
re sponse to X-ray ir ra di a tion, as it was ob served with
HOX11. Fur ther more, HSIX1, as HOX11, is aberrantly
ex pressed in can cer. Overexpression of HSIX1 is ob
-served in 44% of pri mary and 90% of met a static breast
le sions, sug gest ing that HSIX1 may play a role in the
pro gres sion of breast can cer
11. In mam mary glands,
HOXC6 tran scripts, which are ac tive dur ing the pu
-berty and ma tu rity, be came si lent dur ing preg nancy,
prob a bly be cause of the neg a tive reg u la tion of ste roid
hor mone, and are also in ac tive in mam mary
adenocarcinomas
12.
In other neoplasms, ex pres sion of HOX genes was
also re ported. For in stance, re nal adenocarcinomas
con sis tently ex press the HOXA9 gene and only rarely
ex press ei ther HOXD10 or HOXC9
30. HOXB6, HOXB8
and HOXC9 are misexpressed at var i ous stages of co
-lon can cer evo lu tion
37. HOXB7 is si lent in nor mal
melanocytes, but be came ac tive in mel a no mas
5. In
mouse skin, HOXA6, A7 and B7 were iden ti fied in
papilloma, but not in nor mal skin
6. HOXC6, D1 and
D8 are ex pressed in hu man neuroblastoma cells
8.
Finally, in osteosarcomas, HOXC6 ex pres sion seems
to be reg u lated by mem bers of the TGF-
β
superfamily
18.
CONCLUSIONS
A link be tween de vel op ment and can cer is ex pected
since both pro cesses in volve cell pro lif er a tion and cell
dif fer en ti a tion. Homeobox genes were first de scribed in
or gan isms in de vel op ment and are now rec og nized to
be ex pressed in many types of can cers. The dif fer ence
be tween the ex pres sion pat tern in dis tinct nor mal tis
sues and in tu mor tis sues must be fur ther char ac ter
-ized in or der to all in carcinogenesis. Also, fur ther
char ac ter iza tion isences of mod u lat ing these genes ex
-pres sion in neoplasms, in clud ing oral can cer.
ACKNOW LED GE MENTS
REFERENCES
1. Appu kut tan B, Sood R, Ott S, Ma ka lows ka I, Pa tel RJ, Wang X, et al. Iso la ti on and cha rac te ri za ti on of the hu man ho me o box gene HOX D1. Mol Biol Rep 2002;27:95-201. 2. Bar ber TD, Bar ber MC, To mes cu O, Barr FG, Ru ben S, Fri
-ed man TB. Iden ti fi ca ti on of tar get ge nes re gu la t-ed by PAX3 and PAX3 FKHR in em bryo ge ne sis and al ve o lar rhab dom -yo sar co ma. Ge no mics 2002;79:278-84.
3. Bijl JJ, van Oost ve en JW, Wal bo o mers JM, Hors tman A, van den Bru le AJ, Wil lem ze R, et al. HOXC4, HOXC5 and HOXC6 ex pres si on in noHodgking’s lympho ma: pre fe ren -ti al ex pres si on of the HOXC5 gene in pri mary cu ta ne ous ana plas tic Tcell and orogastrointestinal tract mu co -sa-associated B-cell lympho mas. Blo od 1997;90:4116-25. 4. Cal das C, Apa ri cio S. Cell Me mory and can cer – the his tory of the trit ho rax and Poly comb group ge nes. Can cer Me tas -ta sis Rev 1999;18:313-29.
5. Care A, Sil va ni A, Mec cia E, Mat tia G, Stop pac ci a ro A, Par mi a ni G, et al. HOXB7 cons ti tu ti vely ac ti va tes ba sic fi bro -blast growth fac tor in me la no mas. Mol Cell Biol 1996;16:4842-51.
6. Chang PY, Ko zo no T, Chi da K, Ku ro ki T, Huh N. Dif fe ren ti al ex pres si on of Hox ge nes in mul tis ta ge car ci no ge ne sis of mou se skin. Bi o chim Bi ophys Res Com mun 1998; 248:749-52.
7. Cil lo C, Can ti le M, Fa i el la A, Bon ci nel li E. Ho me o box ge nes in nor mal and ma lig nant cells. J Cell Physi ol 2001;188:161-9. 8. Cil lo C, Fa i el la A, Can ti le M, Bon ci nel li E. Ho me o box ge nes
and can cer. Exp Cell Res 1999;248:1-9.
9. Da vi de au JL, Dem ri P, Hot ton D, Gu TT, Mac Dou gall M, Shar pe P, et al. Com pa ra ti ve study of MSX-2, DLX-5, and DLX7 gene ex pres si on du ring early hu man to oth de ve lop -ment. Pe di atr Res 1999;46:650-6.
10. De Vita G, Bar ba P, Odart chen ko N, Gi vel JC, Fres chi G, Buc ci a rel li G, et al. Expres si on of ho me o boxcontaining ge -nes in pri mary and me tas ta tic co lo rec tal can cer. Eur J Can cer 1993;29A:887-93.
11. Ford HL. Ho me o box ge nes: a link bet we en de ve lop ment, cell cycle, and can cer. Cell Biol Int1998;22:397-400. 12. Fri ed mann Y, Da ni el CA, Strick land P, Da ni el CW, Strick
land P. Hox ge nes in nor mal and ne o plas tic mou se mam -mary gland. Can cer Res 1994;54:5981-5.
13. Geh ring WJ, Mul ler M, Affol ter M, Per ci val-Smith A, Bil le ter M, Qian YQ, et al. The struc tu re of the ho me o do ma in and its func ti o nal im pli ca ti ons. Trends Ge net 1990;6:323-9. 14. Gol pon HA, Ge ra ci MW, Mo o re MD, Mil ler HL, Mil ler GJ,
Tu der RM, et al. HOX ge nes in hu man lung: al te red ex pres -si on in pri mary pul mo nary hyper ten -si on and emphyse ma. Am J Pat hol 2001;158:955-66.
15. Go od man FR, Scam bler PJ. Hu man HOX gene mu ta ti ons. Clin Ge net 2001;59:1-11.
16. Ingram JL, Stod gell CJ, Hyman SL, Fi gle wicz DA, We it -kamp LR, Ro di er PM. Dis co very of al le lic va ri ants of HOXA1 and HOXB1: ge ne tic sus cep ti bi lity to au tism spec trum di sor ders. Te ra to logy 2000,62:393-405. 17. Katz MR, Irish JC, De vins GM, Ro din GM, Gul la ne PJ. Re li
a bi lity and va li dity of an ob ser verrated dis fi gu re ment sca -le for head and neck can cer pa ti ents. Head Neck 2000; 22:132-41.
we en hu man os te os sar co ma and ne u ro blas to ma cell li nes. Bi o chem Bi ophys Res Com mun 1997;233:365-9.
19. Kno ep fler PS, Kamps MP. The hig hest af fi nity DNA ele ment bound by Pbx com ple xes in t(1;19) le u ke mic cells fa ils to me di a te co o pe ra ti ve DNAbinding or co o pe ra ti ve transac tion by E2aPbx1 and class I Hox pro te ins – evi den ce for se lec ti ve tar get ting of E2aPbx1 to a sub set of Pbxrecogni -tion ele ments. Onco ge ne 1997;14:2521-31.
20. Law ren ce HJ, Sa u wa ge au G. The role of HOX ho me o box ge nes in nor mal and le u ke mic he ma to po i e sis. Stem Cells 1996;14:281-91.
21. Le vi ne M, Hoey T. Ho me o box pro te ins as se quen ce-specific trans crip ti on fac tors. Cell 1988;55:537-40.
22. Le wis EB. A gene com plex con trol ling seg men ta ti on in Dro -sop hi la. Na tu re 1978;276:565-70.
23. Lle wellyn CD, John son NW, War na ku la su ri ya KA. Risk fac tors for squa mous cell car ci no ma of the oral ca vity in young pe o ple – a com pre hen si ve li te ra tu re re vi ew. Oral Oncol 2001;37:401-18.
24. Mark M, Rij li FM, Cham bon P. Ho me o box ge nes in em bryo -ge ne sis and pat ho -ge ne sis. Pe di atr Res 1997;42:421-9. 25. Na ka mu ra T, Lar ga es pa da DA, Lee MP, John son LA,
Ohyas hi ki K, To ya ma K, et al. Fu si on of the nu cle o po rin gene NUP98 to HOXA9 by the chro mo so me trans lo ca ti on t(7;11)(p15;p15) in hu man mye lo id le u ke mia. Nat Ge net 1996;12:154-8.
26. Nis hi mo to K, Ii ji ma K, Shi ra ka wa T, Ki ta ga wa K, Sa to mu ra K, Na ka mu ra H, et al. PAX2 gene mu ta ti on in a fa mily with iso la ted re nal hypo pla sia. J Am Soc Neph rol 2001; 12:1769-72.
27. Nu nes FD; Tuc ci R, Ma ti zon kas LF, Pin to Jú ni or DS. Expres si on of the HOX ge nes in oral squa mous cell car ci -no ma cell li nes [sub mit ted to pu bli ca ti on].
28. Nutt SL, Eber hard D, Hor cher M. Pax5 de ter mi nes the iden tity of B cells from the be gin ning to the end of B-lymphopoiesis. Int Rev Immu nol 2001;20:65-82. 29. Ra man V, Mar ten sen SA, Re is man D, Evron E, Oden wald
WF, Jaf fee E, et al. Com pro mi sed HOXA5 func ti on can li -mit p53 ex pres si on in hu man bre ast tu mours. Na tu re 2000;405:974-8.
30. Red li ne RW, Ne ish A, Hol mes LB, Col lins T. Ho me o box ge nes and con ge ni tal mal for ma ti ons. Lab Invest 1992;66:773-82. 31. Scholl FA, Ka ma ras hev J, Mur mann OV, Ge ert sen R,
Dum mer R, Scha fer BW. PAX3 is ex pres sed in hu man me -la no mas and con tri bu tes to tu mor cell sur vi val. Can cer Res 2001;61:823-6.
32. Scott GA, Gold smith LA. Ho me o box ge nes and skin de ve -lop ment: a re vi ew. J Invest Der ma tol 1993;101:3-8. 33. Shar pe PT. Ho me o box ge nes and oro fa ci al de ve lop ment.
Con nect Tis sue Res 1995;32:17-25.
34. Sil bers te in GB, Dress ler GR, Van Horn K. Expres si on of the PAX2 on co ge ne in hu man bre ast can cer and its role in pro -ges te ro ne-dependent mam mary growth. Onco ge ne 2002; 21:1009-16.
37. Vi der BZ, Zim ber A, Hirsch D, Estle in D, Chas tre E, Pre vot S, et al. Hu man co lo rec tal car ci no ge ne sis is as so ci a ted with de re gu la ti on of ho me o box gene ex pres si on. Bi o chem Bi ophys Res Com mun 1997;232:742-8.
38. Wong DT, Todd R, Tsu ji T, Do noff RB. Mo le cu lar bi o logy of hu man oral can cer. Crit Rev Oral Biol Med 1996;7:319-28.
39. Zwe i er C, Albrecht B, Mi tul la B, Beh rens R, Be e se M, Gil -les sen-Kaesbach G, et al. “Mo wat-Wilson” syndro me with and wit hout Hirschsprung di se a se is a dis tinct, re cog ni za -ble mul ti ple con ge ni tal ano ma li es-mental re tar da ti on syndro me ca u sed by mu ta ti ons in the zinc fin ger ho me o -box 1B gene. Am J Med Ge net 2002;108:177-81.
