Activation of Ret oncogene in human adrenal tumors

• Main Authors: Yang, Yuan-Chieh, 楊淵傑
• Other Authors: Lin Shiu-Ru
• Format: Others
• Language: zh-TW
• Published: 1997
• Online Access: http://ndltd.ncl.edu.tw/handle/18373984698404705139

碩士 === 高雄醫學院 === 醫學研究所 === 85 === Ret原型致癌基因為酪胺酸激之接受器，主要角色是參與細胞內訊 息之傳遞，搏而影響生長與分裂。此基因之構造分別由富涵半胱胺酸鈣離 子結合區與相似於細胞間黏連因子的配位體結合位之膜外簇；和具酪胺酸 激之膜內簇以及膜間簇所共同組成。近年來許多文獻報告 指出 ，在人類甲狀腺乳突狀瘤；Ret原型致癌基因的活化是藉由本身酪胺酸激 簇和其它基因（包括H4、PKA/RIa及RFG）之5'端發生重組所造成。而最 近的研究結果更顯示Ret原型致癌基因同時存在以點突變致活化的方式， 且僅發生於多發性內分泌腫瘤2A型、2B型、嗜鉻性細胞瘤及家族性和一些 散發性的甲狀腺髓質癌病例中。其中點突變發生的位置主要集中在一些半 胱胺酸基、酪胺酸激簇和膜間簇所在的區域，特別是譯碼634在多發性 內分泌腫瘤2A型，有高達84%之突變率。 為了想瞭解Ret原型致癌基因 在散發性腎上腺腫瘤是否同樣有受活化的情形存在，本實驗室直接運用聚 合連鎖反應合併單股構形多型性分析以及核酸定序法等技術，將所收集 之35例腎上腺腫瘤（包括18例Conn's症候群、3例庫欣氏症候群、2例非功 能性腎上腺腫瘤與12例嗜鉻性細胞瘤），分別針對Ret原型致癌基因之富 涵半胱胺酸膜外簇（exon 6和10）、膜間簇（exon 11）及酪胺酸激簇 （exon12-17）進行序列分析。另外並透過反轉錄聚合連鎖反應及南 方雜交法分析此致癌基因於各種腎上腺腫瘤組織中基因重組的變化情形。 結果顯示，Ret基因相同之誤訊突變發現於1例嗜鉻性細胞瘤及1例Conn's 症候群。同時亦證實在庫欣氏症候群和Conn's症候群病患腫瘤組織中各1 例存在有Ret 重組型致癌基因(RET/PTC1：Ret酪胺酸激簇與H4基因重組 ）。 綜合上述實驗結果發現，Ret原型致癌基因之突變及RET/PTC1不 僅出現在先天性多發性內分泌腫瘤症候群、甲狀腺髓質癌以及甲狀腺乳突 狀癌中，而且同樣地也發生於散發性的腎上腺腫瘤中。除此之外，亦有譯 碼634熱突變點的產生。所以我們推測Ret致癌基因可能在腎上腺腫瘤發生 過程中同樣扮演重要的角色，至於詳細作用機制則有待更深一層的研究與 探索。 The Ret proto-oncogene is a tyrosine kinase receptor whichwas isolated in 1985. It was found to be involved in signaltransduction during cell growth an differentiation. The Retproto-oncogene has a calcium-binding cysteine-rich extra- cellular domain along with a cadherin-like ligand binding site,a tyrosine kinase containing intracellular domain, and ashort transmembrane domain. previous studies have shown thatRet proto- oncogene is frequently activated in human thyroidpapillary carcinoma by chromosome rearrangements that involvein the fusion of tyrosine kinase domain to the 5'-terminalregion of other genes(including H4, PKA/RIa and RFG). Recently,other studies showed that the point mutation of Ret proto-oncogene was only found in the MEN 2A(Multiple endocrineneoplasia type 2A), MEN 2B, pheochromocytomas,FMTC(familialmedullary thyroid carcinoma) and some sporadic MTC. Inaddition, the point mutation sites were located in the codonsspecifying for some cysteine residues, tyrosine kinase domainand transmembrane domain. Especially, the mutation rate of Retproto-oncogene at codon 634 which specifies for cycteineresidues in MEN2A was up to 84%. For further understanding the role of the activation ofRet proto-oncogenein sporadic adrenal tumors, we analyzed thegenetic changes of Ret proto-oncogene on cysteine rich extra-cellular domain(exon 6 and 10), transmembranedomain(exon 11)and tyrosine kinase domain(exon 12-17) in 35 cases of adrenaltumors(including 18 Conn's syndrome , 3 Cushing's syndrome,2 non-functional adrenal tumors and 12 pheochromocytomas) byPCR-SSCP(Polymerase Chain Reaction-Single Strand ConformationalPolymorphism ) and sequencing methods. We also detected therearrangement of Ret by RT-PCR and Southern hybridization.The results show that 1 case with pheochromocytoma and 1 casewith Conn's syndrome have single missense mutation. Also,1 casewith Conn's syndrome and 1 case withCushing's syndrome haveRET/PTC1(Ret tyrosine kinase domain rearranged with H4 gene). The results above show that the mutations of Ret proto-oncogene and RET/PTC1 not only happened in the congenitalMEN syndromes, MTC and papillary thyroid cacinoma but also insporadic adrenal tumors. The mutation site of Ret oncogene atcodon 634 was also found in adrenal tumors. It suggests thatthe Ret oncogene may play an important role in the tumori-genesis of adrenal tumors,and it needs further investigation.