Wu Daqing, Thakore Chittam U, Wescott Ginger G, McCubrey James A, Terrian David M
Department of Anatomy and Cell Biology, Brody School of Medicine, East Carolina University, Greenville, NC 27858, USA.
Oncogene. 2004 Nov 11;23(53):8659-72. doi: 10.1038/sj.onc.1207900.
Failure of hormone therapy often involves an outgrowth of protein kinase Cepsilon (PKCepsilon)-positive cells in recurrent prostate cancer. Our previous investigations have uncovered evidence of a complex signaling network operating downstream of this oncogenic protein kinase to actively advance the survival and proliferation of prostate cancer cells. In this study, we present evidence of a functional interplay among integrin receptors, PKCepsilon, and protein kinase B (PKB/Akt) in recurrent CWR-R1 prostate cancer cells. Flow cytometry and confocal microscopy provided evidence that PKCepsilon signaling promoted the assembly of matrix adhesions containing an abundance of colocalized actin filaments and beta1 integrins that exhibited an exposed activation epitope on the surface of live CWR-R1 cells. Reciprocal coimmunoprecipitations provided evidence of signaling complexes containing PKCepsilon, beta1 integrins, Src, and PKB/Akt in CWR-R1 cell cultures. An investigation into the functional significance of these interactions, and of their positive influence on beta1 integrins, demonstrated that PKCepsilon and several key components of the PKB/Akt signaling pathway remain constitutively phosphorylated/activated in adherent but not suspension cultures of PTEN-positive CWR-R1 cells. Gene transfer, antisense and pharmacological experiments provided additional support for the hypothesis that a mutually reinforcing signaling loop sustains the activation of beta1 integrins, PKCepsilon, and PKB/Akt in adherent prostate cancer cells.
激素疗法的失败通常与复发性前列腺癌中蛋白激酶Cε（PKCε）阳性细胞的增多有关。我们之前的研究发现了一个复杂信号网络的证据，该网络在这种致癌蛋白激酶的下游发挥作用，积极促进前列腺癌细胞的存活和增殖。在本研究中，我们展示了复发性CWR-R1前列腺癌细胞中整合素受体、PKCε和蛋白激酶B（PKB/Akt）之间功能相互作用的证据。流式细胞术和共聚焦显微镜提供了证据，表明PKCε信号传导促进了基质黏附的组装，这些黏附包含大量共定位的肌动蛋白丝和β1整合素，在活的CWR-R1细胞表面呈现出暴露的活化表位。相互免疫共沉淀提供了CWR-R1细胞培养物中含有PKCε、β1整合素、Src和PKB/Akt的信号复合物的证据。对这些相互作用的功能意义及其对β1整合素的积极影响的研究表明，在PTEN阳性CWR-R1细胞的贴壁培养而非悬浮培养中，PKCε和PKB/Akt信号通路的几个关键成分保持组成性磷酸化/活化状态。基因转移、反义及药理学实验为以下假说提供了额外支持：一个相互增强的信号环维持着贴壁前列腺癌细胞中β1整合素、PKCε和PKB/Akt的活化。
