Yao Mu, Xie Chanlu, Kiang Mei-Yee, Teng Ying, Harman David, Tiffen Jessamy, Wang Qian, Sved Paul, Bao Shisan, Witting Paul, Holst Jeff, Dong Qihan
Department of Endocrinology, Royal Prince Alfred Hospital, Camperdown, NSW 2050, Australia.
Central Clinical School and Bosch Institute, The University of Sydney, Sydney, NSW 2006, Australia.
Oncotarget. 2015 Oct 27;6(33):34458-74. doi: 10.18632/oncotarget.5277.
Cell cycle re-entry of quiescent cancer cells has been proposed to be involved in cancer progression and recurrence. Cytosolic phospholipase A2α (cPLA2α) is an enzyme that hydrolyzes membrane glycerophospholipids to release arachidonic acid and lysophospholipids that are implicated in cancer cell proliferation. The aim of this study was to determine the role of cPLA2α in cell cycle re-entry of quiescent prostate cancer cells. When PC-3 and LNCaP cells were rendered to a quiescent state, the active form of cPLA2α with a phosphorylation at Ser505 was lower compared to their proliferating state. Conversely, the phospho-cPLA2α levels were resurgent during the induction of cell cycle re-entry. Pharmacological inhibition of cPLA2α with Efipladib upon induction of cell cycle re-entry inhibited the re-entry process, as manifested by refrained DNA synthesis, persistent high proportion of cells in G0/G1 and low percentage of cells in S and G2/M phases, together with a stagnant recovery of Ki-67 expression. Simultaneously, Efipladib prohibited the emergence of Skp2 while maintained p27 at a high level in the nuclear compartment during cell cycle re-entry. Inhibition of cPLA2α also prevented an accumulation of cyclin D1/CDK4, cyclin E/CDK2, phospho-pRb, pre-replicative complex proteins CDC6, MCM7, ORC6 and DNA synthesis-related protein PCNA during induction of cell cycle re-entry. Moreover, a pre-treatment of the prostate cancer cells with Efipladib during induction of cell cycle re-entry subsequently compromised their tumorigenic capacity in vivo. Hence, cPLA2α plays an important role in cell cycle re-entry by quiescent prostate cancer cells.
静止癌细胞重新进入细胞周期被认为与癌症进展和复发有关。胞质磷脂酶A2α（cPLA2α）是一种将膜甘油磷脂水解以释放花生四烯酸和溶血磷脂的酶，这些物质与癌细胞增殖有关。本研究的目的是确定cPLA2α在静止前列腺癌细胞重新进入细胞周期中的作用。当PC-3和LNCaP细胞进入静止状态时，与增殖状态相比，Ser505位点磷酸化的cPLA2α活性形式较低。相反，在诱导细胞周期重新进入过程中，磷酸化cPLA2α水平会回升。在诱导细胞周期重新进入时，用依非普拉地对cPLA2α进行药理抑制会抑制重新进入过程，表现为DNA合成受到抑制、G0/G1期细胞持续保持高比例、S期和G2/M期细胞百分比低，以及Ki-67表达恢复停滞。同时，依非普拉地在细胞周期重新进入过程中阻止了Skp2出现，同时使p27在核区室中保持高水平。抑制cPLA2α还能防止在诱导细胞周期重新进入过程中细胞周期蛋白D1/细胞周期蛋白依赖性激酶4（CDK4）、细胞周期蛋白E/细胞周期蛋白依赖性激酶2（CDK2）、磷酸化视网膜母细胞瘤蛋白（pRb）、预复制复合物蛋白细胞分裂周期蛋白6（CDC6）、微小染色体维持蛋白7（MCM7）、复制起始点识别复合物6（ORC6）以及DNA合成相关蛋白增殖细胞核抗原（PCNA）的积累。此外，在诱导细胞周期重新进入时用依非普拉地对前列腺癌细胞进行预处理，随后会损害其体内致瘤能力。因此，cPLA2α在静止前列腺癌细胞重新进入细胞周期中起重要作用。
