PKC-ε-Smad3 信号轴调节前列腺癌细胞Warburg 效应及促瘤生长的作用和机制

Warburg effect(known as aerobic glycolysis), a hallmark of cancer cells, has attracted much attention in recent years, but the exact molecular mechanism underlying this metabolic switch is not clear. Our previous results and preliminary data showed that endogenous PKC-ε knockdown by siRNA transfection in prostate cancer cells not only significantly reduce the glucose uptake and lactate production , but also inhibit the expression of proteins involved in aerobic glycolysis as well as tumor cell growth, while overexpression of Smad3 can antagonize the inhibitory effects of endogenous PKC-ε knockdown on the glucose uptake , lactate production , glycolytic related gene expression and tumor cell growth. However, how PKC-ε contributions to Warburg effect and tumor growth in prostate cancer via Smad3 signaling remain unclear. Here in this proposal we hypothesize for the first time that PKC-ε-Smad3 signaling axis promotes Warburg effect and tumor growth in prostate cancer. To test this hypothesis, the proposed study will utilize the following AIMs: AIM 1: Determine the correlations of PKC-ε expression ,Smad3 activation as well as lactate secretion with prostate cancer clinical progression. AIM 2 :verify PKC-ε-Smad3 signaling axis promotes the Warburg effect and tumor growth in prostate cancer through tumor cell models in vitro and orthotopic tumor xenograft model in vivo. AIM 3 :explore the mechanism underlying PKC-ε-Smad3 signaling axis contributions to Warburg effect, lactate secretion and tumor growth in prostate cancer. This proposal will provide new insights and idea into the intrinsic correlation of tumor glucose metaoblic switch with the tumor growth and progression in prostate cancer.

Warburg 效应是近年备受关注的肿瘤特征标志,但其确切调控机制尚不完全清楚。我们近期研究发现：内源性PKC-ε的敲低降低前列腺癌细胞葡萄糖吸收、乳酸分泌、糖酵解相关蛋白的表达及肿瘤细胞生长，而Smad3的过表达则可拮抗PKC-ε的敲低对上述效应的抑制作用。但PKC-ε如何通过Smad3调节Warburg 效应而促进前列腺癌细胞的生长及机制尚不清楚。基于此，本项目首次以PKC-ε-Smad3信号轴这个新视点探讨：（1）明确PKC-ε的表达、Smad3的激活及乳酸分泌与前列腺癌进展的临床相关性；（2）体外及体内移植瘤模型确证PKC-ε通过Smad3 激活促进前列腺癌细胞Warburg 效应及肿瘤生长；（3）探讨PKC-ε-Smad3 信号轴促进前列腺癌细胞Warburg 效应、乳酸分泌及肿瘤细胞生长的机制。本研究将为揭示糖代谢改变与前列腺癌生长及进展的内在关联提供新的视野和思路。

PKC-ε已证实在包括前列腺癌、乳腺癌、肺癌等多种肿瘤中过表达，其上调表达被认为是肿瘤复发和生存期缩短的重要不良预后指标。然而，PKC-ε是否通过调节肿瘤的糖代谢而促进肿瘤的生长及进展尚不清楚。本项目通过一系列的细胞生物学、分子生物学等研究策略首次证实PKC-ε通过以PKDs 和TGF-beta 非依赖的方式促进Smad3的链接区Ser213的磷酸化，进而促使Smad3 入核与糖酵解相关蛋白基因的启动子结合，促进糖酵解相关蛋白的表达，最终促进糖酵解和前列腺癌的生长及进展。结果显示：（1）无论是PKC-ε还是Smad2/3都促进葡萄糖的吸收、乳酸的分泌、糖酵解相关蛋白的表达及前列腺癌细胞的增殖；（2）PKC-ε以PKDs非依赖方式上调糖酵解相关蛋白的表达；（3）Smad2/3 是PMA或EGF介导的前列腺癌细胞糖酵解的关键调节分子，且不依赖于TGF-beta 信号的激活；（4）PKC-ε与Smad2/3直接相互作用，且导致Smad3的链接区Ser213的磷酸化，进而促使Smad3入核与糖酵解相关蛋白基因启动子结合；（5）Smad3的过表达恢复PKCε敲低对前列腺癌细胞葡萄糖吸收、乳酸分泌及细胞增殖的抑制；（6）MCT4抑制剂可拮抗PKC-ε或Smad3过表达诱导的前列腺癌细胞增殖。上述研究为进一步揭示前列腺癌糖代谢改变与肿瘤生长及进展的内在关联奠定基础，并以前列腺癌的代谢异常作为靶向治疗策略提供了新的靶点和思路。