Bhattacharyya Sayantan, Sekar Vasanthakumar, Majumder Biswanath, Mehrotra Debapriya G, Banerjee Samir, Bhowmick Anup K, Alam Neyaz, Mandal Gautam K, Biswas Jaydip, Majumder Pradip K, Murmu Nabendu
Department of Signal Transduction and Biogenic Amines, Chittaranjan National Cancer Institute, 37, S. P. Mukherjee Road, Kolkata, 700026, India.
Department of Molecular Pathology and Cancer Biology, Mitra Biotech, 202, Narayana Nethralaya, Hosur Main Road, Bangalore, 560099, India.
Cell Oncol (Dordr). 2017 Apr;40(2):145-155. doi: 10.1007/s13402-016-0311-7. Epub 2016 Dec 30.
The tumor suppressor protein p53 is known to control cell cycle arrest and apoptosis. Lupeol is a phytochemical that has been found to induce apoptosis in different cancer types through the extrinsic pathway. As yet, however, its role in the induction of cell cycle arrest and apoptosis through the intrinsic pathway in head and neck cancer has not been investigated. Here, we aimed at understanding the mechanism underlying the antitumor effect of Lupeol in head and neck cancer.
The antitumor effect of Lupeol on oral and laryngeal carcinomas was assessed using two in vitro 2D cell line models (HEp-2, UPCI:SCC-131) and, subsequently, an ex vivo 3D tumor explant culture platform that maintains key features of the native tumor microenvironment. The mechanism underlying Lupeol-mediated antitumor responses was delineated using MTT, colony formation, flow cytometry, immunofluorescence, Western blotting and immunohistochemistry assays.
We found that Lupeol induced an enhanced expression of p53 in both cell line models tested and, subsequently, cell cycle arrest at the G1 phase. In addition we found that, following Lupeol treatment, p53 induced Bax expression and activated the intrinsic apoptotic pathway (as measured by Caspase-3 cleavage). Interestingly, Lupeol was also found to trigger G1 cell cycle arrest through up-regulation of the expression of CDKN2A, but not p21, resulting in inhibition of CyclinD1. In an ex vivo platform Lupeol was found to impart a potent antitumor response as defined by inhibition of Ki67 expression, decreased cell viability and concomitant activation (cleavage) of Caspase-3. Finally, we found that Lupeol can re-sensitize primary head and neck squamous cell carcinoma (HNSCC) tumor samples that had clinically progressed under a Cisplatin treatment regimen.
Together, our data indicate that Lupeol may orchestrate a bifurcated regulation of neoplastic growth and apoptosis in head and neck cancers and may serve as a promising agent for the management of tumors that have progressed on a platinum-based treatment regimen.
肿瘤抑制蛋白p53已知可控制细胞周期停滞和凋亡。羽扇豆醇是一种植物化学物质，已发现其可通过外源性途径诱导不同癌症类型的细胞凋亡。然而，迄今为止，其在头颈部癌中通过内源性途径诱导细胞周期停滞和凋亡的作用尚未得到研究。在此，我们旨在了解羽扇豆醇对头颈部癌抗肿瘤作用的潜在机制。
使用两种体外二维细胞系模型（HEp-2、UPCI:SCC-131）评估羽扇豆醇对口腔癌和喉癌的抗肿瘤作用，随后使用维持天然肿瘤微环境关键特征的体外三维肿瘤外植体培养平台进行评估。使用MTT、集落形成、流式细胞术、免疫荧光、蛋白质印迹和免疫组织化学分析来阐明羽扇豆醇介导的抗肿瘤反应的潜在机制。
我们发现羽扇豆醇在所测试的两种细胞系模型中均诱导p53表达增强，随后导致细胞在G1期停滞。此外，我们发现，在羽扇豆醇处理后，p53诱导Bax表达并激活内源性凋亡途径（通过Caspase-3裂解来衡量）。有趣的是，还发现羽扇豆醇通过上调CDKN2A而非p21的表达来触发G1期细胞周期停滞，从而抑制细胞周期蛋白D1。在体外平台中，发现羽扇豆醇可产生有效的抗肿瘤反应，表现为抑制Ki67表达、降低细胞活力并伴随Caspase-3的激活（裂解）。最后，我们发现羽扇豆醇可使在顺铂治疗方案下临床进展的原发性头颈部鳞状细胞癌（HNSCC）肿瘤样本重新敏感。
总之，我们的数据表明羽扇豆醇可能对头颈部癌的肿瘤生长和凋亡进行分叉调节，并可能成为治疗在铂类治疗方案下进展的肿瘤的有前景的药物。
