Farrell W E, Talbot J A, Bicknell E J, Simpson D, Clayton R N
Centre for Cell and Molecular Medicine, School of Post Graduate Medicine, University of Keele, Stoke-on-Trent, UK.
Clin Endocrinol (Oxf). 1997 Aug;47(2):241-4. doi: 10.1046/j.1365-2265.1997.2891088.x.
With isolated exceptions the only oncogene significantly associated with pituitary tumours is a constitutively active Gs protein (G alpha s). The recent cloning of the cDNA of human G alpha q has facilitated the study of this activator of the phospholipase C beta/Ca2+/ protein kinase C pathway. Since, with isolated exceptions, non-functional tumours are responsive in vitro to TRH and GnRH which activate Gq, we have investigated the genomic sequence of G alpha q, in non-functional (NF) invasive pituitary adenomas, at a residue corresponding to the one most frequently mutated in G alpha s.
We studied 27 invasive NF pituitary tumours by direct sequencing of DNA derived from archival slide extracted tumour cells. Primers were designed to encompass Arg183 (corresponding to Arg201 of G alpha s) which when mutated has been shown to have oncogenic potential when transfected into cultural rat fibroblasts. In a previous study we have described allelic loss at tumour suppressor gene loci (TSG) in 7 of these 27 tumours.
We successfully amplified genomic DNA with primers designed from the cDNA sequence of G alpha q with specific exclusion of a processed pseudogene. No mutations were found at Arg183, in either the tumours showing allelic losses at specific TSG loci, or in the 20 remaining tumours in which we found no losses at the TSG loci investigated.
Mutations at this key residue in G alpha q occur infrequently, if at all, in invasive non-functional pituitary tumours. However we cannot exclude the possibility of mutation(s) at the other key residue of G alpha q, Gin209, implicated in GTP hydrolysis, or in other components of this pathway.
除个别例外，唯一与垂体肿瘤显著相关的癌基因是组成型激活的Gs蛋白（Gαs）。人Gαq cDNA的近期克隆促进了对磷脂酶Cβ/ Ca2 + /蛋白激酶C途径激活剂的研究。由于除个别例外，无功能肿瘤在体外对激活Gq的促甲状腺激素释放激素（TRH）和促性腺激素释放激素（GnRH）有反应，我们研究了侵袭性无功能垂体腺瘤中Gαq的基因组序列，该序列对应于Gαs中最常发生突变的残基。
我们通过对存档玻片提取的肿瘤细胞DNA进行直接测序，研究了27例侵袭性无功能垂体肿瘤。设计引物以涵盖Arg183（对应于Gαs的Arg201），当该残基发生突变时，已证明将其转染到培养的大鼠成纤维细胞中具有致癌潜力。在先前的一项研究中，我们描述了这27例肿瘤中的7例肿瘤抑制基因位点（TSG）的等位基因缺失。
我们成功地用根据Gαq cDNA序列设计的引物扩增了基因组DNA，特异性排除了一个加工过的假基因。在Arg183处未发现突变，无论是在特定TSG位点显示等位基因缺失的肿瘤中，还是在其余20例在研究的TSG位点未发现缺失的肿瘤中。
在侵袭性无功能垂体肿瘤中，Gαq的这个关键残基即使发生突变也很少见。然而，我们不能排除Gαq的另一个关键残基Gln209（与GTP水解有关）或该途径其他成分发生突变的可能性。
