Division of Hematology/Oncology, Case Western Reserve University, University Hospitals Case Medical Center, Cleveland, Ohio, United States.
Mol Oncol. 2011 Jun;5(3):256-64. doi: 10.1016/j.molonc.2011.03.004. Epub 2011 Mar 30.
Protein Inhibitor of Activated Signal Transducer and Activators of Transcription 3 (PIAS3) is an endogenous inhibitor of STAT3 transcriptional activity. We have previously demonstrated the concentration-dependent negative regulatory effect of PIAS3 on STAT3 signaling and its capacity to decrease lung cancer proliferation and synergize with epidermal growth factor inhibition. We now investigate PIAS3 expression in both non-small cell lung cancer (NSCLC) cell lines and human resected NSCLC specimens. We also investigated the mechanism by which some lung cancers have significantly decreased PIAS3 expression. Expression of PIAS3 is variable in lung cancer cells lines with 2 of 3 squamous cell carcinoma (SCC) cell lines having no or little PIAS3 protein expression. Similarly, the majority of human SCCs of the lung lack PIAS3 expression by immunohistochemistry; this despite the finding that SCCs have significantly higher levels of PIAS3 mRNA compared to adenocarcinomas. High PIAS3 expression generally correlates with decreased phosphorylated STAT3 in both SCC cell lines and human specimens compatible with the negative regulatory effect of this protein on STAT3 signaling. To investigate this variable expression of PIAS3 we first performed sequencing of the PIAS3 gene that demonstrated single nucleotide polymorphisms but no mutations. Exposure of lung cancer cells to 5-azacytidine and trichostatin A results in a significant increase in PIAS3 mRNA and protein expression. However, methylation-specific PCR demonstrates a lack of CpG island methylation in the promoter region of PIAS3. Exposure of cells to an agent blocking proteosomal degradation results in a significant increase in PIAS3. Our data thus shows that SCC of the lung commonly lacks PIAS3 protein expression and that post-translational modifications may explain this finding in some cases. PIAS3 is a potential therapeutic molecule to target STAT3 pathway in lung cancer.
激活信号转导和转录激活因子 3（STAT3）的蛋白抑制剂（PIAS3）是 STAT3 转录活性的内源性抑制剂。我们之前已经证明了 PIAS3 对 STAT3 信号的浓度依赖性负调控作用及其降低肺癌增殖和与表皮生长因子抑制协同作用的能力。我们现在研究了 PIAS3 在非小细胞肺癌（NSCLC）细胞系和人切除的 NSCLC 标本中的表达。我们还研究了一些肺癌中 PIAS3 表达显著降低的机制。PIAS3 在肺癌细胞系中的表达是可变的，其中 3 个鳞状细胞癌（SCC）细胞系中的 2 个没有或几乎没有 PIAS3 蛋白表达。同样，大多数人 SCC 缺乏免疫组织化学表达的 PIAS3；尽管 SCC 与腺癌相比具有显著更高水平的 PIAS3 mRNA。高 PIAS3 表达通常与 SCC 细胞系和人标本中磷酸化 STAT3 的减少相关，这与该蛋白对 STAT3 信号的负调控作用一致。为了研究 PIAS3 的这种可变表达，我们首先对 PIAS3 基因进行了测序，结果表明存在单核苷酸多态性但没有突变。肺癌细胞暴露于 5-氮杂胞苷和曲古抑菌素 A 会导致 PIAS3 mRNA 和蛋白表达显著增加。然而，甲基化特异性 PCR 表明 PIAS3 启动子区域不存在 CpG 岛甲基化。细胞暴露于阻断蛋白酶体降解的试剂会导致 PIAS3 显著增加。我们的数据表明，肺 SCC 通常缺乏 PIAS3 蛋白表达，在某些情况下，翻译后修饰可能解释了这一发现。PIAS3 是一种针对肺癌 STAT3 通路的潜在治疗分子。
