Kong Dexin, Yamori Takao, Yamazaki Kanami, Dan Shingo
Tianjin Key Laboratory on Technologies Enabling Development of Clinical Therapeutics and Diagnostics, School of Pharmaceutical Sciences and Research Center of Basic Medical Sciences, Tianjin Medical University, 22 Qixiangtai RD, Heping, Tianjin, 300070, China,
Invest New Drugs. 2014 Dec;32(6):1134-43. doi: 10.1007/s10637-014-0152-z. Epub 2014 Aug 26.
As accumulating evidences suggest close involvement of phosphatidylinositol 3-kinase (PI3K) in cancer, novel PI3K inhibitors such as ZSTK474, GDC-0941, NVP-BEZ235 and BKM-120 have been developed for cancer therapy. A high frequency of hotspot mutations known as E542K, E545K and H1047R in the PIK3CA gene, which encodes the catalytic subunit of PI3Kα, has been found in various types of human cancers. The hotspot PIK3CA mutations also lead to resistance to therapeutics targeting epidermal growth factor receptor (EGFR), further suggesting that inhibition of hotspot mutant PIK3CA be required for a PI3K inhibitor as anticancer drug candidate.
To investigate the activity of the novel PI3K inhibitors on the hotspot mutant PIK3CA, we determined the inhibition against the respective recombinant mutant PI3Kαs by biochemical assay. We further examined the activity at cellular background by determining the effect on phosphorylation of Akt (Ser473), and that on the growth of cancer cells. In addition, apoptosis and autophagy in cells with or without hotspot PIK3CA mutation induced by the four inhibitors were investigated.
Our results indicated that each inhibitor exhibit comparable activity on the hotspot mutant PI3Kα to that on the wild type, which was further demonstrated by the cell-based assays. No clear correlation was shown between the PIK3CA genetic status and the sensitivity for apoptosis or autophagy induction. Interestingly, among the 4 PI3K inhibitors, BKM-120 is the weakest in PI3K inhibitory potency, but induces most potent apoptosis, suggesting that BKM-120 might have a unique mode of action.
Our result shows that the PI3K inhibitors exhibit potent activity on both hotspot mutant and wild type PI3Kα, suggesting they might be used to treat patients with or without PIK3CA mutation when approved.
越来越多的证据表明磷脂酰肌醇3激酶（PI3K）与癌症密切相关，因此已开发出新型PI3K抑制剂，如ZSTK474、GDC-0941、NVP-BEZ235和BKM-120用于癌症治疗。在各种类型的人类癌症中，已发现编码PI3Kα催化亚基的PIK3CA基因中存在高频率的热点突变，即E542K、E545K和H1047R。热点PIK3CA突变还导致对靶向表皮生长因子受体（EGFR）的治疗产生耐药性，这进一步表明，作为抗癌药物候选物的PI3K抑制剂需要抑制热点突变型PIK3CA。
为了研究新型PI3K抑制剂对热点突变型PIK3CA的活性，我们通过生化分析确定了它们对各自重组突变型PI3Kα的抑制作用。我们还通过测定对Akt（Ser473）磷酸化的影响以及对癌细胞生长的影响，进一步研究了细胞背景下的活性。此外，还研究了这四种抑制剂诱导的有无热点PIK3CA突变的细胞中的凋亡和自噬情况。
我们的结果表明，每种抑制剂对热点突变型PI3Kα的活性与对野生型的活性相当，基于细胞的分析进一步证明了这一点。PIK3CA基因状态与凋亡或自噬诱导敏感性之间未显示出明显的相关性。有趣的是，在这4种PI3K抑制剂中，BKM-120的PI3K抑制效力最弱，但诱导的凋亡作用最强，这表明BKM-120可能具有独特的作用方式。
我们的结果表明，PI3K抑制剂对热点突变型和野生型PI3Kα均具有强大的活性，这表明它们在获批后可能用于治疗有或无PIK3CA突变的患者。
