Vorinostat加強cisplatin在小細胞肺癌的抗癌效果:細胞與動物研究

Abstract

小細胞肺癌(small-cell lung cancer)相較於非小細胞肺癌(non-SCLC)是極具侵略性的惡性腫瘤，並有著快速生長、早期轉移和產生抗藥性等特點。因其可使用的治療策略有限，小細胞肺癌患者的臨床治療預期表現並不佳。Vorinostat是種一種組織蛋白去乙醯酶抑制劑(HDAC inhibitor)，且已應用在許多癌症的標靶治療中。將vorinostat與cisplatin組合時，vorinostat能使染色體結構變得相對疏鬆，增加cisplatin與DNA結合的效率，達到提升細胞毒殺的效果。而此組合療法尚未於小細胞肺癌進行測試。在本研究中，我們先測試vorinostat是否能增強臨床用藥cisplatin與etoposide的效能；接著著重研究vorinostat與cisplatin在細胞生長、細胞凋亡、細胞週期抑制、細胞訊號傳遞與免疫缺陷裸鼠動物模式中的複合效果。我們發現，vorinostat與cisplatin/etoposide結合能有效抑制細胞生長、增加細胞凋亡。而vorinostat與cisplatin雙加藥物組合亦能顯著抑制細胞增生、加強細胞凋亡，且能調控並抑制細胞週期。Vorinostat的調控蛋白histone H3與α-tubulin的乙醯化現象在藥物雙加時比單加vorinostat有更顯著增強的表現。此外，雙加藥物組合能持續抑制胸腺嘧啶合成酶(thymidylate synthase)的表現。最後，在肺癌腫瘤異種移植裸鼠實驗中，vorinostat與cisplatin能更有效抑制腫瘤生長(T/C% = 20.5%)。我們發現，雙加組合能夠透過調節染色體結構與乙醯化蛋白，顯著增強細胞毒殺作用。在三加藥物實驗中，亦有類似的抗癌效果。這些治療組合提供了降低cisplatin藥物使用量的可能，並有機會能減少藥物使用的副作用。因此，我們建議此有效的新穎複合藥物能進入臨床測試階段。

Background: Vorinostat, a histone deacetylase (HDAC) inhibitor, is a promising agent for cancer therapy. Combining vorinostat with cisplatin may relax the chromatin structure and facilitate the accessibility of cisplatin, thus enhancing its cytotoxicity. Studies have not yet investigated the effects of the combination of vorinostat and cisplatin on small-cell lung cancer (SCLC). Methods: We first assessed the efficacy of vorinostat with etoposide/cisplatin (EP; triple combination) and then investigated the effects of cotreatment with vorinostat and cisplatin on H209 and H146 SCLC cell lines. The anticancer effects of various combinations were determined in terms of cell viability, apoptosis, cell cycle distribution, and vorinostat-regulated proteins. We also evaluated the efficacy of vorinostat/cisplatin combination in H209 xenograft nude mice. Results: Our data revealed that the triple combination engendered a significant reduction of cell viability and high apoptotic cell death. In addition, vorinostat combined with cisplatin enhanced cell growth inhibition, induced apoptosis, and promoted cell cycle arrest. We observed that the acetylation levels of histone H3 and α-tubulin were higher in combination treatments than in vorinostat treatment alone. Moreover, vorinostat reduced the expression of thymidylate synthase (TS), and TS remained inhibited after cotreament with cisplatin. Furthermore, an in vivo study revealed that the combination of vorinostat and cisplatin significantly inhibited tumor growth in xenograft nude mice (tumor growth inhibition = 20.5%). Conclusions: Combined treatments with vorinostat promote the cytotoxicity of cisplatin and induce the expression of vorinostat-regulated acetyl proteins, eventually enhancing antitumor effects in SCLC cell lines. Triple combinations with a low dosage of cisplatin demonstrate similar therapeutic effects. Such triple combinations, if applied clinically, may reduce the undesired adverse effects of cisplatin. The effects of the combination of vorinostat and cisplatin should be evaluated further before conducting clinical trials for SCLC treatment.