Involvement of p73-dependent apoptosis pathway in the process of acquisition of drug-resistance in human lung cancer cell lines

p73是与p53肿瘤抑制基因具有实质性DNA和蛋白质同源性的候选肿瘤抑制基因。在本研究的第一部分中，我们研究了两个假设：（a）p73在不同类型的人类癌症中突变，（B）p73在致癌作用中与p53功能冗余，因此突变在这两个基因中是排他性的。在54个癌细胞系中检测了p73的整个编码区和内含子剪接点。三种肺癌细胞系含有影响氨基酸序列的突变。一个氨基酸取代是在与p53的特异性DNA结合区同源的区域中，两个微缺失是在同源区域之外。两个具有p73突变的细胞系也携带p53突变。我们的结果与两个假设检验不一致。接下来，我们检验了p63的假设，即（a）p63在不同类型的人类癌症中发生突变，（B）p63与p53和p73在癌前病变中的作用途径相同。 ...更多信息 因此，这三个基因的突变是相互排斥的。我们分析了p63基因的基因组结构，并使用与p73相同的细胞系进行了突变分析。我们已经证明，DLD 1和SKOV 3细胞在p63的假定DNA结合域中具有杂合突变或多态性。在这些细胞系中，p63是双等位基因表达的。在研究的最后一部分，我们分析了在肺癌细胞系中发现的三种自然发生的p73突变体。NCI-H1155在DNA结合结构域中具有p73突变p73（G264 W），以及“功能获得性”p53突变p53（R273 H）。p73α（G264 W）本身缺乏反式激活活性，并抑制野生型p73α的反式激活活性，表明p73α（G264 W）是一个显性失活突变体。p73α（G264 W）不能抑制集落形成。在DMS 92或A427中发现的p73突变体没有显示功能异常。在NCI-H1155细胞中，废除p73和p53的正常功能的突变的共存可能表明每个突变赋予细胞累加生长优势。少

p73 is a candidate tumor suppressor gene with substantial DNA and protein homology to the p53 tumor suppressor gene. In the first part of this study, we have investigated two hypotheses: (a) p73 is mutated in diverse types of human cancer, and (b) p73 is functionally redundant with p53 in carcinogenesis so that mutations would be exclusive in these two genes. The entire coding region and intronic splice junctions of p73 were examined in 54 cancer cell lines. Three lung cancer cell lines contained mutations that affected the amino acid sequence. One amino acid substitution was in a region with homology to the specific DNA binding region of p53 and two microdeletions were outside the region of homology. Two of the cell lines with p73 mutations also carried p53 mutations. Our results are inconsistent with the two hypotheses tested. Next we checked hypotheses for p63 that (a) p63 is mutated in diverse types of human cancers and (b)p63 functions in the same pathway as p53 and p73 in the pro … More cess of carcinogenesis, so that mutations in these three genes would be mutually exclusive. We analyzed the genomic structure of the p63 gene and have performed mutational analyses using the same set of cell lines as for p73. We have shown that DLD1 and SKOV3 cells have either heterozygous mutations or polymorphisms in the putative DNA binding domain of p63. In these cell lines, p63 is biallelically expressed. In the last part of the study, we analyzed three naturally occurring p73 mutants found in lung cancer cell lines. NCI-H1155 has a p73 mutation, p73(G264W), in the DNA binding domain, as well as a "gain-of-function" p53 mutation, p53(R273H). p73α(G264W) lacks the transactivation activity itself, and suppressed the transactivation activity of wild-type p73α, indicating that p73α(G264W) is a dominant negative mutant. Consistently, p73α(G264W) failed to suppress colony formation. p73 mutants found in DMS 92 or in A427 showed no functional abnormalities. In NCI-H1155 cells the coexistence of mutations that abrogate the normal function of p73 and p53 may indicate that each mutation confers an additive growth advantage on the cells. Less