DAC DIEM D O T BIEN GEN C-KFT VA GEN PDGFRA TRONG U MO DEM TIEU HOA PGS. TS. BS. Hda Thi Ngoc Ha, ThS. BS. Ngo Quoc Dat
Bp mon Gidi plmu benh, Dai hoc Y Dupc TP HCM U md dem tieu hoa (GISTs) la Ioai u tnmg md thudng gap nhat oia duong tieu hda [34]. Hau het GISTs deu cd nhinig dot bi&i tang chuc nang ciia gen c-kit hoac gen PDGFRA, cac dot bieh nay ra't cd gia tri trong tien lupng cung nhu trong chi dinh dieu tri vdi thudc li'c che chuyen biet tren nhiing thy the tyrosine kinase (TK) cua ABL, KIT va PDGFRA, imatinib mesylate [18,24].
1. Cau tnic va chirc nang gen c-kit va gen PDGFRA
Gen c-kit va gen PDGFRA nam tren NST 4ql2, ma hda ra rihiing glycoprotein xuyen mang thupc gja dinh thu the tyrosine kinase loai IH. Gia dinh protein nay cd cac phin tli d^c biet gdm mpt domain ngoai mang (EC) vdi 5 cau tnic dang vdng gidng phan tii immunoglobulin mien dich va domain bao tuong vdi hai thanh ph&i, mot viing can mang (JM) va mpt domain tyrosin kinase (TK). Domain TK lai chia thanh hai vimg nhd, vimg gan adenosine triphosphate (ATP) (TKl) va vimg phosphotransferase (TK2), hai vimg nay ngan each nhau bdi su chen vao cua vimg kinase ai nudc (KI). Domain ngoai mang (EQ va domain bao tuong gdn vdi nhau bdi vimg xuyen mang [34,41].
Binh thudng gen c-kit va PDGFRA bi kich ho?t bdi cac Ugand ciia chiing, cac yeii to te bao gdc va PDGFs. Khi cac hgand gin vao thu the ciia domain EC gay phan iing nhi trimg ciia thii the va hoat hda qua trinh phosphoryl hda cua tyrosines d domain TK: nam trong bao tuong. Qua trinh nay kich ho^t ddng thac phosphoryl hda ciia cac tyrosine cdn lai thdng qua chuoi cac phan tu truyen tin hieu va ho^it hda cac dudng dan truyen tin hieu nhu; he thong din truyen tin hieu Ras/MAP kinase, Rac/Rho-JNK, P13K/AKT va SFK/STAT. Ho^t dpng aia KZT-TK dupe dieu hda bdi chinh domain JM ciia nd, nd se lie che boat dpng oia KIT kinase khi khong cd cac KIT hgand. Su hoat hda KIT anh hudng d&h qua trinh dieu hda cac chiic nang quan trpng oia tdbao nhu: tang sinh te bao, chdt tdbao theo chuong tririh hda, hda hudng dpng va ket dinh te bao, dong thdi la yeu to quan trpng cho su duy tri, phat trien va biet hda ciia mdt so' ddng tdbao. Cac ddng te bao nay bao gdm cac te'bao oia hi tgo mau, dudng bao, h3c bao, giao tii va tdbao md d^m ke ciia Cajal, mot Ioai tdbao dieu nhip cua nhu dpng cua ong tieu hda va dieu hda dan truyai than kinh tu ddng [44]. Tuy nhien, tinh trang khang thudc thudng hen quan den nhiing trudng hpp dot biai gen c-kit va gen PDGFRA thii phat [23, 28].
FTinh : Dot bieii tang chdc ndng cua gen c-kit, gen PDGFRA nguyen phdt va thd plmt.
2. Dot bien gen c-kit va gen PDGFRA trong GISTs:
Cd hai loai: (1) Ddt bieh nguyen phat, dot bidn xay ra trudc khi benh nhan dupc dieu tri lie chdTK, lien quan ddn benh sinh cua GISTs; (2) Dot bieh thii phat, xay ra trong sud't qua trinh dieu tri lie che TK, gay de khang vdi imatiiub [11].
Dua \-ao vj tri, nhiing dot biai nay dupc chia thanh hai loai chinh: dpt bim ciia domain dieu hda Qm the' (EC va JM) \'a dot bioi cua domam men (TKl va TK2) [32]. Trong GISTs, hau he't cac dpt bim gen c-kit xay ra o domain JM (exon 11), tiep theo la domain EC (exon 9). Dot bieh 6 domain JM
129
anh huong dlh dnic nang tu dieu hda \ a dieu khien hoat ddng cua kinase. E)dt H&\ tai domain EC Iam ma't diuc nang iic die'phan ung nhi trimg phan, t?o ra qua nhieu thu th^™*"*™"™™-"-"^.
Ciing \a}-, nhiing dot bim d exon 9 anh hudng dm nhieu dudng dan truyen tin hieu te'bao khac nhau hon la nhimg dot bim xay ra d domain JM. Da sd' cac dot bieh gm PDGFRA anh hudng deh domain TK2 (exon 18). Nhung dpt bim nay lam thay doi vdng hoat hda, mpt ca'u true dieu hda qua trinh gin kei ATP cui^ nhu kidi hoat kinase. Dot bim tang hoat c-kit va PDGFRA da dupc duing ininh la qui luat thiei ym b-ong anh bmh hpe cua GISTs ca lam sang va thuc n ^ O T
6 cac tnrong hpp GIST khdng cd tinh gja (finh, dpt bim gen c-kit nguyen phat tfiudng dupc phat hien tren cac domain EC (exon 9), JM (exon II) va TK2 (exon 13,17), ngupc lai dpt bim gen PDGFRA nguyen phat thudng xay ra d domain JM (exon 12), TKl \'a TK2 (exon 14, 18). Nhiing dot bim thii phat da so xay ra tren cac domain K/T-TKl va -TK2 (exon 13,14,17) va KI (exon 15 va 16) va PDGFiM-TK2 (exon 18) [24,42],
vi tri d$t bien Kjr-IM (exon 8) Ja7-JM (exon 11) KIT-JM (exon 11) XIT-JM (exon 11) K!7-JM (exon 11) KIT-JM (exon 11) ja7-JM(exonll) Jtir-TKl (exon 13) jaT-TK2(exon]7) PDGfiM-TKl (exon 12) PDGFRA-ra (exon 12) PDGFRA-TKl (exon 18)
Dgt bien a muc dp protein Asp419del Trp557Arg Val559Ala Val560Gly Val560del Gln575 Leu576dup Asp579del Lys642Glu Asp820Tvr Tvr555Cys Asp561Val Asp846Tyr
Bieu 1)1^ lam sang GISTs CO tinh p a dinh GISTs CO tinh gia dinh GISTs CO tinh gia dinh GISTs CO tinh gia dinh GISTs CO tinh gia dinh GISTs CO tinh gia dinh GISTs CO tinh gia dinh GISTs CO tinh gia dinh GISTs CO tinh gia dinh GISTs CO tinh gia dinh Da polip soi, u mo va GISTs GISTs CO tinh gia dinh D^t bioi gen c.iit va gen PDGFRA tren fcenh nhan GISTs gia dmh 6 te'bao dau dong, tuong tu GISTs Idiong co tinh gia dinh. Tuy nhiea co hai Ioai dot bieh chi tha'y 6 GISTs gia dinh la dot bieh gen c-fa"l Asp419del (c.l276_1278delGAC) va dot bieh gen PDGFRA Tyr555Cys (C.1803A -> G) (12|.
Nhung dot bieh gen c-kit va gen PDGFRA la nhimg dot bieh loai tru lln nhau, ngliia la trong mot truong hop GISTs nguyen phat hoac thii phat ne'u da co dot bien gen c-itit thi se Idiong CO dot bieh gen PDGFRA [18],
2.1. Nhimg dot bien gen c-kit nguyen phat:
Dpt bien mat doan;
La loai dot bioi gen c-kit thuong gap nha't va chi xay ra tren exon 11 va co the mat tir 3 den 30 hoac hon, gay dpt biai mat doan hoac mat doan va chen doan 6 miic dp protein. Loai dpt bien nay mi the 6 doan 1669_1704 (Lys550_Glu561) tren exon 11 theo chieu 5', trong do thuong gap nha't la mat tu vi tri 1690J695 mat doan TGGAAG (Trp557_Lys558del) (1690J695delTGGAAG (Trp557_Lys558del)). Mpt vai dot bieh ma* doan dai 6 exon 11 theo chieu 5'-3'hau qua mat phan lon ca'u tnic ciia domain JM. Dot bieh exon 11 theo chieu 3' thuong gap nha't la mS doan 6 vi tri tii 1755_1759 mat GAT (mat Asp579) [4, 27]. Nhiing dot bieh mat doan theo cMeu 5' co the anh huong deh c-kit intton lO^exon 11 vi tri noi ghep va thuong gay mat add amin Lys550_Lys558 6 miic dp protein [ 8).
Dot bien diem don nucleotide:
Loai dot bieh gen c-fal thudng gap thii hai va ciing thuong xay ra 6 vi tri exon 11. Dieh htah, nhihig loai dot bien nay xay ra 4 4 bp ma Tryp557, VaI559 va Val560 (5'c-fa't exon 11) va Leuo76 (3'c-fat exon 11) [24]. Dot bieh diem o gen c-kit thucmg gap la Val559Asp, Va]560A5p, Trp5D7Arg, Val559Ala, VaI559GIy va Leu576-Pro. Nhihig dot bieh nay la dot bieh hoat hoa cau tnic phosphoryl.Tuy nhien, mpt ngMen cuu tren thuc nghiem tien mau GISTs co dot bien
diem hiern g3p Val559Ile gay de Idiang voi imatinib, ngupc lai dot bieh thudng gap Val559- Asp lai nhay vdi Imatinib^™''"*'*"""'™""™*'™"*^. Cd nghia la tren cimg mpt bd ma vdi eae kieu dpt bidn diem khac nhau ed the gay ra cac bim dd'i chiic nang sinh hoc khac nhau [4, 27].
Thinh thoang lo^ dpt bidn thay the mpt nucleotide ciing cd the cd 6 exon 13 (TKl) la loai thay the mpt nudeoride 1945A^G (Lys642Glu) va exon 17 (TK2) [24, 32Error! Reference source not found.]. ^™^ RehieB« lonrci not foaB±j^y nhlm, cac nghien cihi gan day ghi nhan dot bieh diem d exon 13 cung kha da dang, gom 6 loai khac nhau: Glu635Lys, Leu641Pro, Val643Ala, Leu647Pro, Met651Val va Asn655Lys. Hon the niia, loai dot bim nhan doan Lys642GIu va Val643Ile cung mdi dupc bao cao. Loai ddt bieh diem Lys642GIu va Asn655Lys gay hoat hda ca'u tnic phosphoryl aia TK, loai dot bieh nay nhay vdi imatinib [Error!
Reference source not found.27,32].
Hau he\ dpt high gen c-fcif exon 17 la dot bien diem 2487T->A (Asn822Lys). Tuy nhien, nhiing ddt bien diem khac nhu Asp816Phe, Asp816Tyr, Asp820Tyr, Asp820Val, Asn822His, Tyr823Asp ding da dupc ghi hh|n. Cac Ioai dot bim CMI tnic tuong tu cdng cd d u te bao mam cua h | sinh dye, u tinh bao va lymphom T loai te bao diet tu nhien ciia mui xoang [21], Dot bien nhan doan:
La Ioai dpt bim thuong gap ttiii 3 [24], tiiudng xay ra tren exon 9 va exon 11 [32Error!
Reference source not ftrand]. Ve caii tnic hau hei dot bim nhan doan d exon 9 la 1525,1530dupGCCTAT (AIa502_Tyr503dup) [32, 41]. Tuy nhien, ba ca ddt bieh nhan doan 1537_1545dup TTTGCATTr (Phe506_Phe508dup) ding dupc bao cao [Error! Reference source not found.24],
Ddt bim nhan do^n a exon 11 rat da dang, ed the thay doi tir 1 dm 18 bp ma (khong tinh phan nitron) [4, 34,Error! Reference source not found. 47]. Da so Ioai dot bieh nay xay ra d dau 3' cua exon 11, chi cd 2 trong td'ng so' 80 bao cao dot bieh xay ra a dau 5' hoac vimg trung tam [4].
Dpt bien chen doan:
La lo^ ddt bidn rdt hidm gap tren gen c-kit va chi co d exon 11, dac taet uu the d bd ma 558.
Hau hdt dpt bim dim doan tren exon 11 la dot bieh eaii tnie: 1694_1695insTCC (Lys558deIinsAstiPro) [24], Tuy nhiea hai loai khac Lys558deIinsGIuPro va Lys558deIinsAsnGln cd trong mdt sd' trudng hpp. Dpt bim Lys558deIinsAsnPro dupc chiing mmh la dot bieh kich boat cau tnic phosphoryl [1, 4, Error! Reference source not found.44].
Dpt bidn phiic t^p mat do^n - chen doan, nhSn doan - chen doan va mat doan - dao doan:
Ma't doan - chen doan va n h ^ d o ^ - chm doan la nhiing Ioai dot l)im himi gap a gen c- kit exon 11. Nhung loai ddt bim nay bao gom mat mot hoac vai nudeotide ket hop vdi nhan doan hoac chen doan nhd.
Gain day ngudi ta phat hi$n ra mot loai dot bidn phiic tap cua gen c-kit exon 9 va exon 11 la dpt bien mat doan kem vdi chen doan, ma doan chen da bi dao ngupc tiinh ty [Error! Reference source not found.31]. 6 miic dp DNA, loai dot bieh nay dupc gpi ten chen doan - dao doan (delinv). Tuy nhien, loai dot bidn nay se chuyen thanh dpi bidn mat doan - chen do^n d miic dd protein. Nhiing loai dot bien nay chua timg dupc bao cao trudc day trong ung thu hpc.
2.2. Nhung dpt bien gen PDGFRA ngnyen phat Dpt bien diem thay the mpt nudeotide:
La loai dot bidn gen PDGFRA thudng gap nha't, thuong xay ra 6 exon 18 (PDGFRA- TK2). Tuy nhien, PDGFRA exon 12 (PDCFRA-JM) va exon 14 (PDGFRA-TKl) ciing cd the bi dot bieh diem [24].
6 exon 18, dpt bieh diem thudng gap nhat la 2664A -^ T (Asp842VaI) [5,18] Tuy nhien, cac lo^i khae nhu Asp842TyT, Asp842Ile, Asp846T}T va Tyr849Cys cung dupe ghi nhan. Dot bien Asp846Tyr cd tren ca GISTs gia dinh va GISTs Ididng gia dinh. Loai dot bieh nay tuong dong vdi ddt bidn Asp820Val tren exon 17, loai dot bim gap nhieu gap hai lah hon d GIST gia
131
dinh. Dot bieh Asp842VaI la loai ddt bien hoat hda PDGFRA trong ca thuc nghiem va lam simg [Error! Reference source not found.l8,22).
6 exon 12 hSu het cac dot bim diem la dot bieh 1821T ^ A (VaI561Asp), la Ioai dot bien nay kich hoat gen PDGFRA tren thyc nghiem [5, Error! Reference source not found.lO, 18, 22] Dot bim Glu556Lys va GIu563Lys duoc bao cao trong hai tmdng hpp, hiy nhien dac tinh sinh hpc cua hai loai dot bim nay deh nay vln diua dupc biet rd [6Error! Reference source not found.].
Dpt biSi di&n d exon 14 hiein gap, dii cd 15 tmdng hop dupe bao cao [5, 10, 22ErTor!
Reference source not found.]. Da so' xay ra d bp ma 659, chii yeu la 2125C->A va 2125C^G (Asn659Lys). Tuy nhien, mpt vai tnrcmg hpp co kieu dpt bieh 2123A^T (Asn659Lys) [22]. Ki&
dot bim Asn659Lys kich boat gen PDGFRA tren thuc nghiem [5].
Dpt bien mat doan:
Dpt bim ma't doan khdng lam mat khung dpe la loai dot bidh diing hang thii hai sau dot bien diem, thudng xay ra tren exon 18 {PDGFRA-TV2) va exon 12 (PDGFRA-JM). Loai dot bieh nay cd the mat tir ba nucleotide tro Im, tucmg iing o miic dp protein cd the gay ra dpt bieh mat doan hoac trong mpt sd tmdng hpp thanh mat doan-chen dogn. Mac dii dot bien mat doan d gen PDGFRA cd th6' xay ra d nhieu vi tri khac nhau, nhung chu yeu mat doan giiia bp ma 840-848 d exon 18 va 559-572 d exon 12 [, 5, Error! Reference source not found.lO, 18, Error! Reference source not found.39]. Loai ddt bien nay kich ho?t gen PDGFRA ea thyic nghi?m va lam sang [5].
Dot bien nhan doan:
La Ioai dot bieh rat hiem gip, chi cd 3 ca xay ra tren exon 12. Hai trong so dd xay ra quanh bd ma 561 va mpt tmong hpp a bp ma thii 20 tinh tir dau 3' [10, Error! Reference source not found.l8]
Dpt bien chen doan:
La loai dot bidn cue ky hiem g|ip. Chi cd mpt ca dupc bao cao 561_562insER tren exon 12 [18].
Dot bien phiic tgp:
Mpt vai ca dot bieh mat dogn-chen doan tren exon 18 da dupe bao cao. Nhiing Iogi dpt bien nay bao gom mat mpt vai nucleotide va chen mpt dm boh nudeotide va thudng gap mat dogn d vimg giiia bp ma 840_849 tren exon 18 [5Error! Reference source not found.]. Mpt vai kieu dpt bieh nay hoat hda gen PDGFRA trm thuc nghiem.
3. Li@n quan giua dpt bi^n gen c-kit va vj tri u, tinh chsCt u:
Tm xuat dot bim gen c-kit va gen PDGFRA khdng gichg lihau gjua GISTs Ianh va ac tinh va Cling khac nhau tiiy theo v; tri u trin dudng tilu hda. Mac dii dot bidn tren exon 11 cua gm c- ht nhu dpt bim mat doan, mat dogn - chen doan va dpt bidn diem dupc ghi nlign d mpi vi tri u khac nhau tren dudng tilu hda tir thuc quan dm dng hgu mdn [32ErrDr! Reference source not found.]. Mpt ti 11 Idn (>80%) cac dpt bim nhan doan oia gen c-kit tren exon 11 la GISTs ciia da day [4,34, Error! Reference source not found.39]. Cho deh nay, ngudi ta khdng ghi nhan cd mdi liln quan giiia dpt biih gm c-kit 6 exon 11 vdi dac diem md isenh hpc, Tuy niiien, dpt bim gen c-kit trin exon 11 thudng xay ra d logi te'bao hinh thoi hon la loai tdbao dang biai md [46].
Hau hdt cac trudng hpp dpt biln nhan dogn ciia gen c-kit a exon 9 xay ra 6 mpt non, rdt it khi 6 da day [4, Error! Reference souice not found.21, 39, 41Error! Reference source not found.]. Mpt nghim ciiu gan day ghi nhan GISTs a mpt non cd dot bien gen c-kit a exon 17 nhieu gap hai lan so vdi GIST d dg day. Tuong tu, ti Ie GIST mdt non cd dpt bim c-Mt exon 13 dmg tang nhe so vdi GISTs d nhiing vi tri khac. Dpt bien c-kit a exon 9,13 va 17 thuong la GISTs Iogi te bao hinh thoi Tuy nhiin, nhiing Iogi d$t bim nay cung ggp trong GIST ac tinh Iogi bieu md d mpt non, trong tmdng hpp nay logi bilii md dupc cho la do chuyen dgng ac
tinh^™"' " • ' • » " « soum noi bond
132
Dot bieh PDGFRA gain nhu chi cd o GISTs da dav va mgc nm, cho thav moi lien he chat che \-di vi tri u [5, Error! Reference sonrce not fonnd-Erroi! Reference soiuce not found.Erroi! Reference source not foiind39,47].
Mot \-ai bao cao cd meu Um he gjiia loai dot bim gen c-kit vdi luoi va gidi tinh, nhung cac ngjiien cirii ldn lai khdng ghi nhan cd mm lim he nay [24]. Tuy nhien, GISTs Ire em va tam dning Carney od uu the' loai bieii md, tren bmh nhan nii, da day la \i tri thuong gap.
NhuT^ u nay khdng cd dpi bim gen c-kit cdng nhu gen PDGFRA, cd Ie trong biidng hop nay hoat hda KIT thdng qua con duong khac khong Uen quan dm dot bim tim gen sinh ung nhu cac loai GISTs khac
6 benh nhan da u soi than kinh tip 1 dii cd KFT-UT va PDGFRA-WT chii khdng cd dot bieh gen c-kit hay gen PDGFRA, ghi nhan hai tmong hpp cd dot bim gen c-kit va 2 truong hgp CO dpi bim gen PDGFRA, nhung nhung dot bieh nay khdng cimg kieu dot bim gen c-kit va gen PDGFRA dmyen biet dio GISTs nhu da md ta tren, cd le day la nhiing dot bim ngau nhien.
Da GISTs cdng co d nhiing benh nhan da u spi than kinh tip 1. Nhiing u nay thudng cd kich Ihudc nho vdi nhieu \deii gen c-kit va PDGFRA khac nhau [16]. Tuy nhien, mpt \ai benh nhan da GISTs nhd, da loai trir dot bim ddng te'bao m ^ , cd ciing kieu dpt bim da dupc ghi nhan, cd the day la traong hpp di can da d cua GISTs [26]. Kilii gm KIT-WT va PDGFRA-WT cung dupc tim thay trong <10% cac trudng hpp GISTs khdng gja dinli. Khong co su khac biet ve mat Iam sang - giai phlu benh trong nhiing truong hpp nkv, ngogi trir u kem nhgy vdi imatinib.
Bang 2: Lien qium giu:a dot hieh gen c-kit vd PDGFRA vdi PI tri u, loqi mo hpc va gid tri tiin lupng:
Vitri d p i bien KTF-EC (exon 9)
KFT-JM (exon 11)
KTF-TKl (exon 13)
K1T-TK2 (exon 17)
PDGFRA- JM {exon 12) PDCFRA-
TKI
D o t b i e n d mxtc dp protein Ala502_T>T503dup
Trp557 L y » 5 8 d d Mat d o a n Mat dogn-Chen dogn
Ddt bieh diem
N h a n d o a n
Lys642Glu
Asn822Lys
Mat d o a n E)dt bieh didm DQt b i m diein
Bien h i e n l a m sang
>90% GISTs d o t b i m kieu n a y la GISTs o n i p t
n o n GISTs 6 m p i noi
trong d h g tieu hoa
Thucmg la GISTs dg d a y
GISTs o moi noi trong d'ng d e u
hda Cd a GISTs m p t
g a p hai lan nhieu h o n GISTs 6 cac n o i
khac
>95% ddt bieh cac Ioai nay xay
ra 6 GISTs d a d a v
Loai m o hoc l / u thi'loai te bao hinh thoi
Loai te'bao lunh thoi \'a Ioai bieu
m o
L'u the Ioai te' bao h i n h thoi
U u thi'loai GISTs bieu m d hoac GISTs ket h p p bieu m o va h i n h thoi
Gia tri tien l u o n g Khdng cd gia tri t i m l u p n g trong GISTs m p t
Bieu hien ac tinh h o n d a c biet la GISTs da
dav Bieu hien it ac tinh h o n khi u 6
da d a y Bieu hien it ac tinh h o n khi u d
da d a y Bieu h i m ac tinh nhieu h o n khi u d d a day Khdng cd gja tri
h e n l u p n g
Bieu hien it ac tinh h o n khi u d
d g d a y
(exon 14) PDCFRA-
TK2 (exon 18)
C-klt PDGFRA
Mat d o a n Ddt bien diem
Khdng dot b i m GISTs d mpi noi trong d'ng tieu
hda GISTs m p t trong hpi chiing
da u spi than ldnh tip 1 GIST trong tam
chiing Carney va GISTs tre em (GISTs dg day)
Logi t d b a o h i n h thoi va logi bieu
m d H a u n h u chi cd loai t d b a o h i n h
thoi
U'u thi'loai te bao iiinh thoi
Khdng cd gja tri tien Iupng
Khong cd gia tri tien Iupng
4. Lien quan voi yeu T6 chimg tpc:
Cho deh nay, nhieu nghien cuu deu Uiong ghi nhan co moi lien quan giua dot bieh gen c-kit va gen PDGFRA va chiing tpc. Tuy nhien, Idii so sanh giira cac nghien ciiu 6 Chau A va Chau Au thay co su khac nhau ve tan xua't xua't Men cua cac loai dpt big'n gen c-kil va gen PDGFRA. Vi du, kieu dpt bien Ala502_Tyr503dup hiem gap, chie'm 6,6% h-png cac GISTs da day 6 cac nuoc Chau Au va Hoa Ky, ngupc lai, loai dpt big'n nay co tan xua't den 32% trpng cac nghien cuu 6 Chau A [24].
5. Tan xuat cac loai dpt bien gen c-kit va gen PDGFRA nguyen phat:
Day la van de con gay nhieu tranh cai vi cac sp heu rat khac nhau giiia cac nghien ciiu Vi dy, SP lipu ve tan xua't dpt bieh gen c-lcit 6 domain KIT-JM trong hai nghien ciiu truoc dly da chenh nhau deh gih 4 lan (25% sp voi 92%), giai thich cho su khong nhH quan nay do:
nhiing vah de ve ky thuat va su khac nhau trong vigc tong hpp cac so Iigu phan tich trong nghien ciiu doan hg. Da so cac nghien ciiu deu lay vat lieu Hi cac trung tam ung thu hpc va cac chuong trinh thii nghiem imatinib, do do hau he't cac truong hpp la GISTs ac tinh co tan xua't dpt bieh gen c-kil nhieu hpn, it dpt bieh gen PDGFRA. COng vay, vi sci ligu tu nhimg nghiin ciiu doan hg tii cac trung tim ung thu hpc va cac chuong trmh thii nghigm imatinib nen ti lg cac ca GISTs rupt npn cung cao hon bmh thuong, vi GISTs mpt non da so ac tinh nen bieu hign Iam sang nhieu hon, va vi vay ti Ig cac dpt bign gen c-kit exon 9 cung cap hon bmh thudng. Tuong tu, so' hgu cOng dupc lay tir cac tmng tam lon, co uy tin, do do ti Ie cac ca kho Cling nhieu, nhu la cac huong hpp GISTs Ioai bigu mO [5, Error! Reference source not found.
6. Gia bri Irong chan doan va Ben lupng ciia dot bifo gen c-kit va PDGFRA trong GISTS:
Hign nay, van con nhieu tranh cai ve' gia tit tign Iupng ciia nhimg dot high gen c-kit exon 11. Cac nghien cuu tnroc day ghi nh|n nhung dot bieh nay thuong gap 6 cac GISTs kich thuoc lon, CP hoat dpng phin bao manh, vi vay co mm lign quan voi GIST ac Unh Tuy nhien nhung ngWen ciiu vg' sau ghi nhan loai dot bieh nay co thg thiy 6 ca GISTs lanh tinh GISTs phat hlgn tinh co va ac tinh, do do khong co moi lign quan giOa nhihig Ioai dot bign nay va hem nang ac Unh [Error! Reference source not found.27. Error! Reference source not round.44].
^^^"fiZ"^ S ^ "^'y V ghi nhan, loai dot bieh gen c-kit exon 11 co lign quan voi hen lupng [24]. Nhung truong hop GISTs co dot bieh nguygn phat trgn c-kit exon 11 Ioai mi't dpan Ihuong bieu hien ac dnh nhieu hon so voi truong hpp dot bi&i digm. Nhung cimg cp ngoai lp, u CO dpt bien digm Tyr557_Lys558 thuong bieu hign ac tinh. Tuy nhien, dpi viM GISTS mpt non dpt bien gen c-kil exon 11 kieu mi't dpan khpng ac tinh hon so voi kieli dpt bien diem. GISTs da day cp dot bieh nhan dpan gen 3'c-fat thuong lanh tinh. Tuy nhien, cQng
CO mdt vai ca GISTs ac tinh cd kieu dot bim nhu tren dupc ghi nhan trong cac nghien ciiu thu nghiem imatinib [1,4, 22, 34Error! Reference source not found.].
Dot bieh gen c-kit exon II dgng dong hpp hi ddi khi ding duac phat hiln tren giai trinh ttr gen true tidp. Ciing vay, ngudi ta cung thdy ed s\r chuyen tir kieii di hop tir sang ddng hpp tir trong qua tiinh tieh trim cua u, cy the trong cac khdi u di can, nhung lgi khdng cd trong cac u nguyen phat. Nhiing nghien ciiu gan day ^ nhan mat allele KIT-WT va tidp theo do la su nhan Ien cua allele KIT-MT la nguyen nhan ciia qua trinh chuyen tii di hpp tir sang dong hpp tu. Co chd sinh hpc tuong ty ciing da duoc tim tha'y trong cac dot bieh gen c-kit exon 13, GISTs dg day va rupt non vdi kieu hinh dong hpp tir ciia dpt bil'n gen c-kit exon 11 la nhung u ac tinh [5, 6].
Ban dau, nguoi ta cho r^ng GISTs vdi dot bieh nhan doan gen c-kit exon 9 la GISTs ac tinh, vi ti II tli vong cao tren nhdm GISTs mpt non so vdi nhdm GISTs dg day co kieu dpt bim nay [4, 30]. Tuy nhien, mpt nghien ciiu gm day tren 145 GISTs mpt non vdi n h i ^ kidu dpt biln gen c-ldt exon 9 khac nhau khdng thay su khac nhau trong tiln lupng khi so sanh vdi GISTs cd dpt biih gen c-kit exon 11 [37].
Mac dil nhiing dot bim gen c-kit exon 13 va exon 17 hiem gap trong GISTs, nhiing nghiin ciiu da trung tam gan day ghi nhgn GISTs dg day cd dot bim c-kit exon 13 cd xu hudng ac tinh hon, ngupc Igi khdng gjd nhan thdy su khac bilt nay tren nhdm GISTs dg day cd ddt bieh exon 13. Hon thd niia, Ichdng cd khac bilt vl' dac tinh sinh hpc trong hai nhdm GISTs mpt non cd dot bidn gen c-ktt exon 13 va exon 17^™^ Reiermte soum not found.
Mpt each tdng quat, nhiing truong hpp GISTs cd dpt bim gen PDGFRA cd chi so' phan bao thap va tien lupng tdt; hau hit deu la GISTs dg day, nhieu ea trong nhdm nay tmdc day dupc chin doan u nguyen bao co tron [24,34].
7. Dot bidn gen c-kit, gen PDGFRA nguyen phat, thu phat vdi lieu phap dieu tri uc chd tyrosine kinase:
Vao nam 2000, ke tir b|nh nhSn GISTs dSu tiln dupe die'u tn thanh cdng vdi thud'c iic chl'TK, imatinb mesylate, nhieu b?nh nhan GISTs da dupe dieu tri thanh cdng vdi Ii|u phap nham tning didi phan hi nay [24]. Tuy nhien, dap iing dieu tn vdi imatinib con phu thupc rdt nhieu vao tinh trang dpt bien gen c-kit va gen PDGFRA.
Bdng 3; Lien quan kieu dot bien gen c-kit vd PDGFRA vdi mdc dp nhay imatinib tren thuc nghiem vd ddp ibig v&i imatinib trong dieii tri theo cac ngluen ci'ni thd nghiem lam sdng cm My vd Chdu Au Loai gen Exon Ki^u ddt bien gen c-kit,
PDGFRA nguyen phat (n)
Muc dp nhay imatinib AIa502_Tyr503dup
Mat doan/Mat doan-Chen dogn
Dpt bien diem Nhan dogn
Nhay vdi imatinib trin thuc nghi|m Dap ling hoan toan (5%); dap iing mpt phan (29%); benh on dinh (47%), benh tim trim (17%) (nghien oiu pha m EORTC).
Lieu cao gia tang thdi gian lui benh La nhiing Ioai dot biih nhay imatinib thudng gap nhat tren thuc nghiem
Dot bie'n hie'm gap VaI559Ile khang imatinib tren thuc nghiem Dap ling hoan toan (6%); dap iing mpt phan (61%); binh dn dinh (25%), benh tieh trim (3%) (nghien Cliu pham EORTC), Lys642GIu (8)
GIu635Lys (1)
Nhay vdi imatinib trin thuc nghiem Dap ling mpt phsm hoac b|nh on dinh 6 ca 9 ca
135
Logi gen
PDGFRA
c-kit
PDGFRA Exon 17
12
14 18
9,11,13, 17
12,14, 18
Kieu dot b i e n gen c-ktt, PDGFRA n g u y e n p h a t (n) Asp820Tyr (1) Asn822Lys (2) Asn822His (2)
A5p561Val (4) Mat doan/Mat doan-Chen d o a n
N h a n dogn, Chen doan Asn659Lvs Asp842_HisS45deI (2) Asp842_Met844deI (1) lle843del (1) ne843_HisS45dd (1) Asp842VaI (7) Asp846Val (1) Khdng dpt b i m
Miic dp n h a y i m a t i n i b
Asn822Lys va Asn822His n h a y imatinib tren t h u c n g h i e m D a p ling mot p h a n (4 ca):
Asn820Tyr, Asn822Lys, Asn822His29,84 Khang imatinib n g u y g n phat:
Asn822Lys
Asp561 Vai va m p t sd'kieu dot b i m khac d exon 12 n h a y vai imatinib tren thyc n g h i e m va Iam sang
Nhgy vdi imatinib tren t h u c ngliiem Mpt vai ca n h a y vdi imatinib tren di\rc nghiem va Iam sang Asp842VaI k h a n g imatinib tren thuc nghi$m
Cd 7 ca k h a n g thuoc bao g o m ca Asp846VaI; b e n h on djnh d 1 ca sau 5 thang dieu tri imatinib D a p ling mpt p h a n (23%); b m h o n d i n h (50%), benh tim t r i m (19%) (nghien ciiu p h a ffl EORTC).
Tren Iam sang benh nhan GISTs cd dot bieh gen c-kit exon 11 thudng dap iing imatinib tot hem benh nhan GISTs cd dot bieh exon 9 va GISTs KlT-WT, benh nhan cd dot bieh c-kit exon 9 thuong phai dimg lieu cao hon de dat dupe kei qua tuong tu benh nhan cd dot bie'n c- kif exon 11. GISTs vdi dot bieh gen PDGFRA kieu dpt bieh dil'm Aps842VaI de khang imatinib,
Trong Idii di^u tri vdi imatinib, khang thud'c thuong xay ra sau mpt dpt bieh gen c-kit va PDGFRA thii phat va hau het la cac dot bie'n die'm d cac bd ma dac biet trin exon 13 va 14 (TKl), exon 15 va 16 (KI) va 17 (TK2) [5,11,15, 30,35].
Gan day, sunitinib malate, cdn gpi SU1248, mpt thudc lie che dong thdi nhieu tfiu the nhu: KIT, PDGFRs, VEGFRs, FLT3 va RET receptor TKs, da dupc dimg trong nhiing tmdng hpp GISTs khang imatinib nhu la mpt thud'c iic chl'TK Ihe'h^ thii hai [14, ISError! Reference source not found.]. Nhiing nghien ciiu trin thuc nghiem va lam sang cho tha'y dap iing Iam sang vdi sunitinib hm quan cd y nghia thd'ng ke vdi tinh trgng dot bim gen c-Mt va gen PDGFRA. Mac dii dap iing sunitinib dupc ghi nhgn d tat ca cac kieu ddt bim dunh, tuy nhiin dap ling nguyen phat tot nhat thudng cao hon d GISTs ed dot bieh gen c-kit exon 9. Hieu qua lie die cua sunitinib tren hoat dpng aia kinase KIT khdng bi anh hudng bdi dpt bim gm c-Mt thii phat tren TKl. Tuy nhim, GISTs vdi dot bieh thii phat gen c-Mt tren TK2 lai khang tri vdi sunitinib. Vi vgy, cae nghien ciiu de fim ra thuoc iic che TK vin cdn tiep hac [19, 39Error!
Reference source not found.].
Tuong ty vay, nWeu nghiin cuu khac trin nhung thu ttie dich khac nhau dang dupc tieh hanh tren ttiyc nghiem va ca tiln thii nghiem Iam sang, cu till' nhu tren cac thanh phan thupc ddng thac ben dudi cua eon dudng KIT va PDGFRA nhu protein AKT va mTOR trong con dudng AKT. Vi du everoUmus cd tiie dupc dimg don dpc hoac ket hpp vdi ttiudc tie che
136
Mpt chi tiet ciing kha thu vi, ngoai cac thud'c tac ddng vao thu the TK cua KIT va PDGFRA va cac thanh phan ciia nhiing con dudng tin hieu cd lien quan thi cac thud'c khang sinh madi trong khd'i u cung cd hieu quadidhgu.
Gan day, cac phuong thiic dieu tri mdi da va dang dupc phat trim tap tmng vao viec Iam gjam hoac loai bd hoan toan bieu hien ciia KIT dua tren su lie che'protein shock nhilt-90 (heat-shock protein-90 (HSP-90)), loai protein ddng vai tro on dinh cau tnic ba chieu ciia KIT, ngan KIT khdng bi thoai hda. Do do, neii HSF-90 bi lie chl'se lam KIT thoai hda va te'bao u se bi chet theo chuong trinh.
S. Ket Luan
Bdi vi logi dot bieh gen c-kit va PDGFRA cd anh hudng nhieu dm tiln lupng va heu phap dieu tri tning didi phan tir, phan tich dot bim gen c-kit va PDGFRA la rat can thiet, dac biet tren nhung trudng hpp GISTs nguyen phat cd tiem nang di can cao va cung dl' logi ra nhiing ca cd dot bieh khang imatinib. Ciing vay, phan tich dot bieh thii phat ding rat can thiet trong qua trinh dieu tn imatinib
Tai li?u tham khao:
Andersson J, B u m m m g F, Meis-Kmdblom ]M et al (2006) "Gastrointestinal stromal tumors w i t h KIT exon 11 deletions are associated with p o o r prognosis Gastroenterology" 130; 1573-1581.
Andersson J, Sjogren H, Meis-Kindblom JM et al (2002) ' T h e complexity of KIT gene mutations a n d chromosome rearrangements a n d their dmical correlation in gastromtesdnai stromal (pacemaker cell) t u m o r s " ADY. J.
Pathol 160; 15-22
Antonescu CR, Besmer P, Guo T et al. (2005) "Acquired resistance to imatinib in gastromtestinal stromal t u m o r s occurs through secondary gene m u t a t i o n " CliiL Cancer Res ;11,4182—4190
Antonescu CR, Sommer G, S a n a n L et al, (2003) "Association of KIT exon 9 mutation with n o n g a s t n c p r i m a r y site and aggressive behavior- KIT mutation analysis a n d clinical correlates of 120 gastromtestinal stromal t u m o r s " Clin, Cancer Res , 9; 3329-3337-
Chen LL, Trent JC, W u EF et al. (2004) " A missense mutation in JOT d o m a m 1 correlates with imahnib resistance in gastrointestinal stromal t u m o r s " Cancer Res. 64; 5913-5919.
C h o S, Kitadai Y, Yoshida S et al. (2006) 'Tleletion of the KIT gene is associated with hver metastasis and poor prognosis in patients with gastrointestmal stromal t u m o r m the stomach" Int. J. Oncol 28; 136I-I367.
C h o m p r e t A, Kannengiesser C, Barrois M et al (2004) 'T DG FRA germline mutation m a family w i t h multiple cases of gastrointestmal stromal t u m o r " Gastroenterology 126; 318-321.
Coriess CL, McGreevey L. Town A et ai. (2004) "KIT gene deletion at the intron ID-exon I I b o u n d r y in GI stromal tumors' J Moi Diag 6; 366-370
Coriess CL, Schroeder A, Gnffith D et al (2005) "PDGFRA mutations m gastromtestinal stromal tumors:
frequency, spectrum a n d in vitro sensitivity to imatinib" J. Clin. Oncol 23; 5357-5364.
D a u m O, Grossmann P, Vanecek T et al (2007) "Diagnostic morphological features of PDGfRA-mutated gastrointestinal stromal tumors, molecular genetic a n d h i s t o l o ^ c analysis of 60 cases of gastric gastrointestmal stromal t u m o r s " Ann. Diagn Pathol. I I , 2 7 - 3 3 .
Demetri GD. (2002) "Identification a n d tieatment of chemoresistant inoperable or metastatic GIST, expenence with the selective tyrosine kinase inhibitor imatinib mesylate (STI571)" Eur J C a n c e r , 38 (Suppl. 5); S 5 2 - S59
d e Raedt T, Cools J, Debiec-Rychter M et al (2006) "Intestmai neurofibromatosis is a subtj'pe of familial GIST a n d results from dominant activating mutation m PDGFR,4" Gastroenterology 131; 1907-1912.
Enule JF, Theou N , Tabone S et al. (2004) "Clinicopathologic, phenotypic, a n d genotypic characteristics of gasfrointestina! mesenchymal t u m o r s Clin. Gastroenlerol" Hepatol 2; 597-605.
Faivre S, Delbaldo C, Vera K et al. (2006) "Safety, pharmacokmehc, and antitumor activity of SU11248, a novel oral multitarget tyrosine kinase inhibitor, in p a h e n t s with cancer" J. Q i n Oncol. 24,25-35.
Haller F, Detken S, Schulten HJ et al. (2007) "Surgical management after neoadjuvant imatinib therapy in gastromtestinal stromal t u m o u r s (GISTs) with respect to imatinib resistance caused b y secondary KIT mutations"
A n n . Surg Oncol, 14; 526-532
Haller F, Schulten H-], A n n b r u s t T et al. (2006) "Multicentric sporadic gastrointestinal stromal t u m o r s (GISTs) of the stomach tvith distinct clonal ongin differential diagnosis to familial a n d syndxomal GIST variants a n d peritoneal metastasis" A m J. Surg Pathol. 31,933-937
H a r t m a n n K, Wardelmarm E, Ma Y et al. (2005) "Novel g e n n l i n e mutation of KIT a s s o d a t e d w i t h familial gastrointestinal stromal t u m o r s a n d mastocytosis" Gastroenterology 129,1042-1046
H e i n n c h MC, Coriess CL, Blanke CD et aL (2006) "Molecular correlates of imatinib resistance m gastrointestmal stiomal tumors". J. Q i n . Oncol 24; 4764—4774
Heinrich MC, Coriess CL, D u e n s m g A et al. (2003) "PDGFRA activating mutations in gastromtestinal stiomal t u m o r s " S d e n c e 299, 708-710.
137
Hirota S, Isozaki K, Morivama Y et al (1998) "Gain-of-function m u t a t i o n s of c-kil m h u m a n gastt-ointeshnal stromal tumors" Saence 279; 577-580
Hirota S, Nishida T, Isozaki K et al. (2001) "Gain-of-funcHon mutation at the extracellular domain of KIT in gastrointestmal stiomal tumours". J. Pathol. 193; 505-510.
Hirota S, Ohashi A, Nishjda T et a l (2003) "Gain-of-function mutations of platelet-derived growth factor receptor alpha gene in gastrointestmal stiomal tumors". Gasti-oenterology 125,660-667.
Hostein I Longy M, Gastaldello B et al. (2006) "Detection of a n e w mutation in KIT exon 9 in a gastrointestinal stromal tumor" Int J, Cancer 118; 2089-2091
Joensuu H (2007) "Second line therapies for the h«atment of gastrointestinal sti-omal tijmor" Curr. Opin O n c o l 19; 353-358.
Joensuu H, Roberts PJ, Sarlomo-Rikala M ef al. (2001) "Effect of tyrosine kinase inhibitor STI57] m a patient with a metastatic gasti^intestmal stromal tumor" N Engl J Med. 344; 1052-1056
Kang DY, Park CK, Choi JS et aL (2007) "Multiple gasti-ointestinal stromal t u m o r s : clinicopathologic and genetic analysis of 12 patienls". Am. J Surg Patiiol 31; 224-232
Kmoshita K, Hirota S, Isozaki K el al (2007) "Characterization of tyrosine kinase I domain c-kit gene mutation Asn655Lys newly found in primal)- jejunal gastiointestinal stromal tumor". Am. J. Gastroenterol. 102; 1134-1136.
Lasota J, Dansonka-Mieszkowska A, Sobin LH et al (2004) " A great majonly of GISTs with PDGFRA mutations represents gastric tumors of low or no malignant polential" Lab Invest. 84,874-883
Lasota J, Jasinski M. Sarlomo-Rikala M et al (1999) "Mutations m exon 11 of c-ht occur preferentially in malignant versus benign gastrointestinal stiomal tumors and do not occur in leiomyomas or leiomyosarcomas" Am.
J.Pathol 154; 53-60.
Lasota J, Jerzak vel Dobosz A, Wasag B et al. (2007) "Presence of h o m o z y g o u s KIT exon 11 mutations is strongly associated with malignant clinical behavior in gastromtestinal stromal t u m o r s " Lab Invest 87; 1029-1041,
Lasota J, Miettinen M (2007) "KIT exon 1] deletion-mversions represent complex mutations in gastiointestmal stromal tumors". Cancer Genet Cytogenet 175,69-72,
LasoU J, Slachura J. Miettmen M. (2006) "GISTs with PDGFRA exon 14 m u t a h o n s represent subset ol clinically favorable gastric tumors with epithelioid morphology" Lab Invest. 86,94-100
Lasota J, Wozniak A, Sarlomo-Rikala M et ai (2000) "Mutations in exons 9 a n d 13 of KIT gene are rare evraits in gastrointestinal stromal tumors A study of two hundred cases". Am. J Pathol 157; 1091-1095.
Martm J, Poveda J, Llombart-Bosch A et al Deletions affecting codons 557-558 of the c-hl gene indicate a poor prognosis in patients with completely resected gastrointestinal stiomal tumors: a study by the Spanish Group for Sarcoma Research (GEIS). J. Cim Oncol. 2005; 23; 6190-6198,
McLean SR, Gana-Weisz M, Hartzoulakis B et al. (2005) "Imatinib b i n d m g a n d cKIT inhibition is abrogated by the cKIT kinase domain I missense mutahon Val654Ala" Moi, Cancer Ther. 4,2008-2015
Miettinen M, Makhlouf H, Sobm LH et al. (2006) "Gastrointestinal stiomal himors (GISTs) of the jejunum a n d Ileum: a dimcopathologic, uiununohistochemical and molecular genetic study of 906 cases before imatinib with long- tem) follow-up" Am. J. Surg Pathol 30,477-489.
Miettinen M, S<*in LH, Lasota J, (2005) "Gastrointestinal stromal tumors (GISTs) of the stomach—a clinicopatiiologii; immunohistochemical and molecular genelic study of 1756 cases w i t h long-term follow-up" Am.
J, Surg Pathol. 29; 52-68.
Miselli F, Casien P, Negri T et al (2007) "c-kit - PDGFRA gene status alterations possibly related to primary imatinib resistance in gastiointestinal stiomal tumors" Cim Cancer Res. 13; 2369-2377
Penzel R, Aulmann S, Moock M et al, (2005) "The location of KIT and PDGFRA gene m u t a h o n s in gastrointestinal stiomal tumours is site and phenotype associated", J, Clin. Pathol 58.634-639,
Prenen H, Cools J, Mentens N et al. (2006) "Efficacy of tiie kinase inhibitor SU11248 agamst gastrointestinal stromal hjmor mutants refractory lo imatmib mesylate". Cim Cancer Res. 12,2622-2627.
Sakurai S, Oguni S, Hironaka M et al (2001) " M u t a t o n s in c-ktl gene exons 9 a n d 13 m gastrointestinal stroma! tumors among Japanese" Jpn J Cancer Res. 92; 494-^98
S a o t R , Debiec-Rychter M. (2006) "GIST under imatinib therapy", Semin Diagn Pathol 23-84-90 Tambonni E, Bonadiman L, Grecx, A et al. (2004) "A new mutation m tiie KIT ATP pod<et causes acquired resistance to imatinib m a gastiointestinal stiomal tiimor patient". Gastroenterology 127- 294-299
T a n i g u d u H Nishida T, Hirota S et al (1999) "Effect of c-kil mutation o n prognosis of gastrointestinal stromal himors". Cancer Res 59,4297-4300,
Tuveson D A Willis NA. Jacks T et al (2001) "STI571 inactivation of the gastrointestinal stromal c-kit oncoprotein: biological and dirucal imphcabons" Oncogene 20,5054-5058
v . HA. Xmh PT. l a t o s h l ™ M n ,J (2005) "A r e c u m n l d « o d e ™ i g a . t r o m t M l n . l . I r o m . l t „ ™ , w i l h a f r a m e s h , f l m u n t i o n r « u l l m s m a . t o p c o d o i , m i a r e > , o i , 1 3 - Genes Chromosomes C a r a , 42 179-183
W a r d e t o ™ , E. H-ychyk A M a r k e l b . c h - B ™ S el .1 <2004) -Associalion of pl.l.lel^derived growih factor
Zot' 1 M r r ^ t f ^ s : """'"• *"" "'•"'""'' - -'^ -" -•^'•-"•^ •- «=«"'••««'»•' - • » '
, 7 Z ^^ f ' * ° ' " " N, Merkelbach-Bnrse S el .1 (2005) " A c q ^ r e d resistance lo , m . a « , b i n Sasliomleslinal s l r o ™ l lumouis caused by mulBple KIT mulalions-. U n c e l Oncol 6 249-251
Vanoss R. Rosenberg AE 5 a ™ L el .1 (2005) "Mulhple g a s t r o m l e s B ^ l a r o m d l u m o r s „ lype 1 neurotibromalosis: a pathologic and molecular study". Mod Palhol 18,475-484
138
