Kurtyka Courtney A, Chen Lu, Cress W Douglas
Department of Cancer Biology and Evolution, H. Lee Moffitt Cancer Center and Research Institute, Tampa, Florida, United States of America.
PLoS One. 2014 May 15;9(5):e96357. doi: 10.1371/journal.pone.0096357. eCollection 2014.
The CDK/Rb/E2F pathway is commonly disrupted in lung cancer, and thus, it is predicted that blocking the E2F pathway would have therapeutic potential. To test this hypothesis, we have examined the activity of HLM006474 (a small molecule pan-E2F inhibitor) in lung cancer cell lines as a single agent and in combination with other compounds. HLM006474 reduces the viability of both SCLC and NSCLC lines with a biological IC50 that varies between 15 and 75 µM, but with no significant difference between the groups. Combination of HLM006474 with cisplatin and gemcitabine demonstrate little synergy; however, HLM006474 synergizes with paclitaxel. Surprisingly, we discovered that brief treatment of cells with HLM006474 led to an increase of E2F3 protein levels (due to de-repression of these promoter sites). Since paclitaxel sensitivity has been shown to correlate with E2F3 levels, we hypothesized that HLM006474 synergy with paclitaxel may be mediated by transient induction of E2F3. To test this, H1299 cells were depleted of E2F3a and E2F3b with siRNA and treated with paclitaxel. Assays of proliferation showed that both siRNAs significantly reduced paclitaxel sensitivity, as expected. Taken together, these results suggest that HLM006474 may have efficacy in lung cancer and may be useful in combination with taxanes.
细胞周期蛋白依赖性激酶/视网膜母细胞瘤蛋白/E2F通路在肺癌中常被破坏，因此，预计阻断E2F通路具有治疗潜力。为了验证这一假设，我们研究了HLM006474（一种小分子泛E2F抑制剂）在肺癌细胞系中作为单一药物以及与其他化合物联合使用时的活性。HLM006474可降低小细胞肺癌和非小细胞肺癌细胞系的活力，其生物学半数抑制浓度（IC50）在15至75μM之间变化，但两组之间无显著差异。HLM006474与顺铂和吉西他滨联合使用时几乎没有协同作用；然而，HLM006474与紫杉醇具有协同作用。令人惊讶的是，我们发现用HLM006474短暂处理细胞会导致E2F3蛋白水平升高（由于这些启动子位点的去抑制）。由于已证明紫杉醇敏感性与E2F3水平相关，我们推测HLM006474与紫杉醇的协同作用可能由E2F3的短暂诱导介导。为了验证这一点，用小干扰RNA（siRNA）使H1299细胞中的E2F3a和E2F3b缺失，然后用紫杉醇处理。增殖试验表明，正如预期的那样，两种小干扰RNA均显著降低了紫杉醇敏感性。综上所述，这些结果表明HLM006474可能对肺癌有效，并且可能与紫杉烷类药物联合使用有用。
