PI3K/AKT/mTOR信号通路及其在卵巢癌治疗中的应用

卵巢癌是女性生殖系统常见的恶性肿瘤,发病率居于妇科恶性肿瘤第三位,死亡率居于妇科恶性肿瘤之首。目前对卵巢癌的标准治疗包括肿瘤细胞减灭术及卡铂和紫杉醇的联合化疗。PI3K/AKT/mTOR信号通路在卵巢癌的细胞增殖、侵袭、细胞周期进展、血管生成及耐药中发挥重要作用,是卵巢癌中最常发生改变的细胞内途径。本文对PI3K/AKT/mTOR信号通路及其在卵巢癌增殖和进展中的影响、PI3K/AKT/mTOR信号通路抑制剂在卵巢癌中的治疗应用做简要综述。     

Protein abundance of AKT and ERK pathway components governs cell type‐specific regulation of proliferation

Signaling through the AKT and ERK pathways controls cell proliferation. However, the integrated regulation of this multistep process, involving signal processing, cell growth and cell cycle progression, is poorly understood. Here, we study different hematopoietic cell types, in which AKT and ERK signaling is triggered by erythropoietin (Epo). Although these cell types share the molecular network topology for pro‐proliferative Epo signaling, they exhibit distinct proliferative responses. Iterating quantitative experiments and mathematical modeling, we identify two molecular sources for cell type‐specific proliferation. First, cell type‐specific protein abundance patterns cause differential signal flow along the AKT and ERK pathways. Second, downstream regulators of both pathways have differential effects on proliferation, suggesting that protein synthesis is rate‐limiting for faster cycling cells while slower cell cycles are controlled at the G1‐S progression. The integrated mathematical model of Epo‐driven proliferation explains cell type‐specific effects of targeted AKT and ERK inhibitors and faithfully predicts, based on the protein abundance, anti‐proliferative effects of inhibitors in primary human erythroid progenitor cells. Our findings suggest that the effectiveness of targeted cancer therapy might become predictable from protein abundance.     

New strategy for in vitro activation of primordial follicles with mTOR and PI3K stimulators

It had been known for decades that primordial follicles in mammalian ovaries are assembled with definite numbers and represent the ovarian reserve throughout the reproductive life. Intra-oocyte PI3K/mTOR pathways have been indicated to play a central role on the activation of primordial follicles. Genetic modified mouse models with chronic activation of PI3K/mTOR signals in primordial oocytes showed premature activation of all primordial follicles and eventually their exhaustion. On the other hand, this may suggest that, unlike chronic activation of PI3K/mTOR, its acute activation in infertility would activate primordial follicles, permitting fertility during the treatment. Previously, PI3K stimulators were reported as a temporary measure to accelerate primordial follicle activation and follicular development in both mouse and human, and were applied in the treatment of infertility in premature ovarian failure (POF) patients. To address whether mTOR stimulators could play similar role in the process, we transiently treated neonatal and aged mouse ovaries with mTOR stimulators-phosphatidic acid (PA) and propranolol. Our results demonstrated the stimulators increased activation of primordial follicles and the production of progeny. Human ovarian cortex cubes were also treated with mTOR or/and PI3K stimulators in vitro. When they were used separately, both of them showed similar promotive effects on primordial follicles. Surprisingly, after joint-treatment with the 2 kinds of stimulators together, synergistic effects on follicular development were observed. Based on increased efficiency of follicular activation in humans, here we propose in vitro transient treatment with mTOR and PI3K stimulators as an optimized protocol for the application in different clinical conditions with limited follicle reserve.     

上皮性卵巢癌中TFAP2A对hTERT表达的调节及其机制研究

摘要 目的：探讨在上皮性卵巢癌中TFA2A对hTERT表达的调节和作用机制。方法：采用免疫组织化学方法检测TFAP2A和hTERT蛋白在卵巢正常、交界及上皮性卵巢癌组织中的表达,采用Western Blot和qRT-PCR技术检测hTERT在敲减TFAP2A基因的SKOV3、CAOV3细胞中的表达水平、检测hTERT在过表达TFAP2A基因的HO8910细胞中的表达水平。在干扰TFAP2A的CAOV3细胞中或过表达TFAP2A的HO8910细胞中分别加入PI3K/AKT信号通路激动剂740-YP或抑制剂LY294002,检测相关蛋白表达变化,探讨TFAP2A、hTERT与PI3K/AKT信号通路的关系。结果：TFAP2A在71.88%的上皮性卵巢癌组织中呈高表达,hTERT在78.12%的上皮性卵巢癌组织中呈高表达; 将hTERT 和TFAP2A的免疫组化评分行Pearson相关性分析,两者间相关系数r=0.78,P＜0.001。Western Blot和qRT-PCR的结果均显示,在SKOV3和CAOV3卵巢癌细胞中,敲减TFAP2A后,hTERT的表达均明显下降,而在HO8910卵巢癌细胞中,增强TFAP2A基因表达后,hTERT的表达均明显上升。在CAOV3和HO8910处理细胞中,分别使用PI3K/AKT信号通路激动剂740-YP 或阻滞剂LY294002处理后,Western Blot 检验hTERT和PI3K/AKT通路蛋白的表达,发现激动剂740-YP 或阻滞剂LY294002可以逆转敲减或过表达TFAP2A引发的PI3K/AKT通路蛋白表达下调或上调,但不能逆转hTERT蛋白表达下调或上调。结论：在卵巢肿瘤组织中,TFAP2A和hTERT在上皮性卵巢癌组织中均呈高表达,且hTERT的表达和TFAP2A成正相关,在上皮性卵巢癌细胞中TFAP2A可调节hTERT的表达,且TFAP2A对hTERT的表达的调节不经由PI3K/AKT通路。     

Dictyostelium uses ether‐linked inositol phospholipids for intracellular signalling

Inositol phospholipids are critical regulators of membrane biology throughout eukaryotes. The general principle by which they perform these roles is conserved across species and involves binding of differentially phosphorylated inositol head groups to specific protein domains. This interaction serves to both recruit and regulate the activity of several different classes of protein which act on membrane surfaces. In mammalian cells, these phosphorylated inositol head groups are predominantly borne by a C38:4 diacylglycerol backbone. We show here that the inositol phospholipids of Dictyostelium are different, being highly enriched in an unusual C34:1e lipid backbone, 1‐hexadecyl‐2‐(11Z‐octadecenoyl)‐sn‐glycero‐3‐phospho‐(1'‐myo‐inositol), in which the sn‐1 position contains an ether‐linked C16:0 chain; they are thus plasmanylinositols. These plasmanylinositols respond acutely to stimulation of cells with chemoattractants, and their levels are regulated by PIPKs, PI3Ks and PTEN. In mammals and now in Dictyostelium, the hydrocarbon chains of inositol phospholipids are a highly selected subset of those available to other phospholipids, suggesting that different molecular selectors are at play in these organisms but serve a common, evolutionarily conserved purpose.     

PC-1解除S6K对AKT信号通路的负反馈抑制

目的:通过建立过表达PC-1的前列腺癌LNCaP细胞系及敲低PC-1表达的C4-2细胞系,探究PC-1激活AKT信号通路的分子机制。方法:将PC-1基因及针对PC-1的siRNA序列,分别克隆至慢病毒表达载体pCDH-EF1-Myc-MCS-T2A-Puro及干扰载体pSIH1-H1-Puro,包装成慢病毒后分别感染前列腺癌LNCaP及C4-2细胞,通过Western印迹鉴定PC-1过表达及敲低效果,并检测PI3K/AKT/mTOR信号通路相关蛋白S6K、AKT的磷酸化水平。结果:PC-1过表达时,S6K磷酸化水平下降,而AKT的磷酸化水平上升。结论:PC-1可以通过抑制S6K激酶活性,解除其对AKT的负反馈抑制作用,从而激活AKT激酶的活性。