Withaferin A induces p53-dependent apoptosis by repression of HPV oncogenes and upregulation of tumor suppressor proteins in human cervical cancer cells
Withaferin A induces p53-dependent apoptosis by repression of HPV oncogenes and upregulation of tumor suppressor proteins in human cervical cancer cells
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DOI：
10.1093/carcin/bgr192
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发表时间：
2011-11-01
期刊：
影响因子：
4.7
通讯作者：
Gupta, Ramesh C.
中科院分区：
文献类型：
--
作者：
Munagala, Radha;Kausar, Hina;Gupta, Ramesh C.
宫颈癌是由表达E6和E7癌蛋白的人乳头瘤病毒（HPV）引起的，已知E6和E7癌蛋白分别抑制肿瘤抑制蛋白p53和pRb。因此，HPV癌蛋白的抑制将导致肿瘤抑制途径的重新激活并引起癌细胞的凋亡。Withaferin A（WA）是药用植物睡茄的活性成分，对几种不同的癌症具有抑制作用。我们在体外和体内研究了WA对人宫颈癌细胞的活性。WA有效地抑制宫颈癌细胞CaSki的增殖（IC 50 0.45 +/- 0.05 μ M）。机制上，发现WA（i）下调HPV E6和E7癌蛋白的表达，（ii）诱导p53的积累，（iii）增加p21的水平，（iv）诱导p53的表达。（cip 1/waf 1）及其与增殖细胞核抗原（PCNA）的相互作用，（iv）引起G（2）/M细胞周期阻滞，与细胞周期蛋白B1、p34（cdc 2）和PCNA水平的调节相关，（v）降低STAT 3的水平及其在Tyr（705）和Ser（727）处的磷酸化和（vi）改变p53介导的凋亡标记物Bcl 2、Bax、半胱天冬酶-3和裂解的PARP的表达水平。在体内，WA导致近70%的无胸腺裸鼠肿瘤体积的减少，在分子标志物的调制与体外基本相似的趋势。这是第一次表明WA显著下调HPV E6/E7癌基因的表达并恢复p53通路，导致宫颈癌细胞凋亡。总之，我们的数据表明，WA可以作为一种有效的治疗剂，用于治疗和预防宫颈癌，而不会产生有害影响。
Cervical cancer is caused by human papilloma virus (HPV) expressing E6 and E7 oncoproteins, which are known to inactivate tumor suppressor proteins p53 and pRb, respectively. Repression of HPV oncoproteins would therefore result in reactivation of tumor suppressor pathways and cause apoptosis in cancer cells. Withaferin A (WA), the active component of the medicinal plant Withania Somnifera, has exhibited inhibitory effects against several different cancers. We examined the activity of WA on human cervical cancer cells in vitro and in vivo. WA potently inhibited proliferation of the cervical cancer cells, CaSki (IC50 0.45 +/- 0.05 mu M). Mechanistically, WA was found to (i) downregulate expression of HPV E6 and E7 oncoproteins, (ii) induce accumulation of p53, (iii) increase levels of p21(cip1/waf1) and its interaction with proliferating cell nuclear antigen (PCNA), (iv) cause G(2)/M cell cycle arrest, associated with modulation of cyclin B1, p34(cdc2) and PCNA levels, (v) decrease the levels of STAT3 and its phosphorylation at Tyr(705) and Ser(727) and (vi) alter expression levels of p53-mediated apoptotic markers-Bcl2, Bax, caspase-3 and cleaved PARP. In vivo, WA resulted in reduction of nearly 70% of the tumor volume in athymic nude mice with essentially similar trend in the modulation of molecular markers as in vitro. This is the first demonstration indicating that WA significantly downregulates expression of HPV E6/E7 oncogenes and restores the p53 pathway, resulting in apoptosis of cervical cancer cells. Together, our data suggest that WA can be exploited as a potent therapeutic agent for the treatment and prevention of cervical cancer without deleterious effects.