Wang Yan, Qi Yan-Xiang, Qi Zenghua, Tsang Suk-Ying
School of Life Sciences, The Chinese University of Hong Kong, Hong Kong, China.
State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Hong Kong, China.
Cancers (Basel). 2019 Apr 18;11(4):558. doi: 10.3390/cancers11040558.
Currently, there is no effective molecular-based therapy for triple-negative breast cancer (TNBC). Canonical transient receptor potential isoform 3 (TRPC3) was previously shown to be upregulated in breast cancer biopsy tissues when compared to normal breast tissues. However, the biological role of TRPC3 in breast cancer still remains to be elucidated. In this study, subcellular fractionation followed by Western blot and immunocytochemistry showed that TRPC3 was over-expressed on the plasma membrane of TNBC line MDA-MB-231 when compared to an estrogen receptor-positive cell line MCF-7. TRPC3 blocker Pyr3 and dominant negative of TRPC3 attenuated proliferation, induced apoptosis and sensitized cell death to chemotherapeutic agents in MDA-MB-231 as measured by proliferation assays. Interestingly, Ras GTPase-activating protein 4 (RASA4), a Ca-promoted Ras-MAPK pathway suppressor, was found to be located on the plasma membrane of MDA-MB-231. Blocking TRPC3 decreased the amount of RASA4 located on the plasma membrane, with concomitant activation of MAPK pathways. Our results suggest that, in TNBC MDA-MB-231 cells, Ca influx through TRPC3 channel sustains the presence of RASA4 on the plasma membrane where it inhibits the Ras-MAPK pathway, leading to proliferation and apoptosis resistance. Our study reveals the novel TRPC3-RASA4-MAPK signaling cascade in TNBC cells and suggests that TRPC3 may be exploited as a potential therapeutic target for TNBC.
目前，三阴性乳腺癌（TNBC）尚无有效的分子靶向治疗方法。与正常乳腺组织相比，经典瞬时受体电位3型（TRPC3）先前已被证明在乳腺癌活检组织中上调。然而，TRPC3在乳腺癌中的生物学作用仍有待阐明。在本研究中，通过亚细胞分级分离，随后进行蛋白质免疫印迹和免疫细胞化学分析，结果显示，与雌激素受体阳性细胞系MCF-7相比，TRPC3在TNBC细胞系MDA-MB-231的质膜上过度表达。通过增殖实验检测发现，TRPC3阻滞剂Pyr3和TRPC3显性负性突变体可减弱MDA-MB-231细胞的增殖、诱导其凋亡，并使其对化疗药物敏感。有趣的是，Ras GTP酶激活蛋白4（RASA4），一种钙促进的Ras-MAPK通路抑制剂，被发现定位于MDA-MB-231细胞的质膜上。阻断TRPC3可减少质膜上RASA4的量，同时激活MAPK通路。我们的研究结果表明，在TNBC的MDA-MB-231细胞中，通过TRPC3通道的钙内流维持了RASA4在质膜上的存在，在此RASA4抑制Ras-MAPK通路，从而导致细胞增殖和抗凋亡。我们的研究揭示了TNBC细胞中新型的TRPC3-RASA4-MAPK信号级联反应，并表明TRPC3可能成为TNBC潜在的治疗靶点。
