N this study, we have shown that TRPC1, TRPC3, TRPC4 and TRPC6 exist in human lung cancer including the adenocarcinoma, squamous cell carcinoma and the adenocarcinomaderived cell line A549. The expression level of TRPC Title Loaded From File channels is correlated to the differentiation grade of lung cancer. ATRA upregulates TRPC gene expression in A549 cells. Inhibition of TRPC channel activity shows antiproliferative effect. These findings are important for understanding the roles of TRPC channels in lung cancer cell differentiation and proliferation. TRPC channels have been detected in many tissues [32,34,35,36] including cancer tissues, such as breast cancer [37], ovarian cancer [9,20], hepatoma [12], prostate cancer [13], basal cell carcinoma [21], renal cell carcinoma [15], malignantgliomas [16], glioblastoma [8], and gastric tumors [19]. The expression level of each TRPC isoform in different type of cancer cells or tissues are variable, suggesting the contribution or biological importance of each TRPC isoform in different cancer type could be different. For example, the expression of TRPC7 is negative in A549 and SKOV-3, but positive in HepG2 cells in this study and in the differentiated neuroblastoma cells [17]. Moreover, the alternative spliced variants may also contribute to the functionality of TRPC channels, such as TRPC1 and TRPC4 16985061 spliced isoforms in ovarian cancer SKOV3 cells [9]. In addition, the expression level of TRPC channels may depend on the differentiation status of the cancer cells, because we found the mRNA expression of TRPC1, TRPC3, TRPC4 and TRPC6 in the low differentiation grade lung cancer was lower than that in the well differentiated cancer, which is consistent to our observation in ovarian cancer [9] and the low level expression of TRPC4 and TRPC6 in immature stem cells [38]. Although our data showed that the mRNA levels of TRPCs in normal lung were higher than that in lung cancer, it is difficult to do such comparison due to variation of cell types, because the normal lung samples contains much more non-epithelial cells than that inTRPC in Lung Cancer DifferentiationFigure 6. Role of TRPC channels in A549 cell proliferations and the effect of ATRA. A, 23148522 the time course for the effect of ATRA on A549 cell proliferation. B, A549 cells were incubated with 2-APB at different concentrations for 24 hours (n = 8 wells for each groups) and the cell proliferation was assayed by WST-1 cell proliferation assay kit. C, A549 cells treated with Title Loaded From File specific E3-targeting TRPC blocking antibodies or combination with ATRA for 48 hours (n = 6? for each group; comparison with the control (#); * or # P,0.05, ** or ## P,0.01). D, A549 cell proliferation was assessed by WST-1 after transfection with TRPC1, 3, 4, and 6 plasmid cDNAs for 48 hours (n = 8 for each group, ** P,0.01). doi:10.1371/journal.pone.0067637.gthe solid tumour samples, such as vascular cells, alveolar macrophages, fibroblasts, and blood cells. The immunostaining on the lung cancer tissue microarrays showed less significant, which could be due to the low sensitivity of methodology comparing to the high sensitivity of real-time PCR. On the other hand, the relationship of TRPC expression with cell differentiation was further confirmed in the in vitro lung cancer cell culture model by application of the cell differentiation regulator ATRA, which significantly enhances the expression of TRPC3, 4, and 6. However, the TRPC5 and TRPC7 were still undetectable after ATRA treatment. The TRPC1 mRN.N this study, we have shown that TRPC1, TRPC3, TRPC4 and TRPC6 exist in human lung cancer including the adenocarcinoma, squamous cell carcinoma and the adenocarcinomaderived cell line A549. The expression level of TRPC channels is correlated to the differentiation grade of lung cancer. ATRA upregulates TRPC gene expression in A549 cells. Inhibition of TRPC channel activity shows antiproliferative effect. These findings are important for understanding the roles of TRPC channels in lung cancer cell differentiation and proliferation. TRPC channels have been detected in many tissues [32,34,35,36] including cancer tissues, such as breast cancer [37], ovarian cancer [9,20], hepatoma [12], prostate cancer [13], basal cell carcinoma [21], renal cell carcinoma [15], malignantgliomas [16], glioblastoma [8], and gastric tumors [19]. The expression level of each TRPC isoform in different type of cancer cells or tissues are variable, suggesting the contribution or biological importance of each TRPC isoform in different cancer type could be different. For example, the expression of TRPC7 is negative in A549 and SKOV-3, but positive in HepG2 cells in this study and in the differentiated neuroblastoma cells [17]. Moreover, the alternative spliced variants may also contribute to the functionality of TRPC channels, such as TRPC1 and TRPC4 16985061 spliced isoforms in ovarian cancer SKOV3 cells [9]. In addition, the expression level of TRPC channels may depend on the differentiation status of the cancer cells, because we found the mRNA expression of TRPC1, TRPC3, TRPC4 and TRPC6 in the low differentiation grade lung cancer was lower than that in the well differentiated cancer, which is consistent to our observation in ovarian cancer [9] and the low level expression of TRPC4 and TRPC6 in immature stem cells [38]. Although our data showed that the mRNA levels of TRPCs in normal lung were higher than that in lung cancer, it is difficult to do such comparison due to variation of cell types, because the normal lung samples contains much more non-epithelial cells than that inTRPC in Lung Cancer DifferentiationFigure 6. Role of TRPC channels in A549 cell proliferations and the effect of ATRA. A, 23148522 the time course for the effect of ATRA on A549 cell proliferation. B, A549 cells were incubated with 2-APB at different concentrations for 24 hours (n = 8 wells for each groups) and the cell proliferation was assayed by WST-1 cell proliferation assay kit. C, A549 cells treated with specific E3-targeting TRPC blocking antibodies or combination with ATRA for 48 hours (n = 6? for each group; comparison with the control (#); * or # P,0.05, ** or ## P,0.01). D, A549 cell proliferation was assessed by WST-1 after transfection with TRPC1, 3, 4, and 6 plasmid cDNAs for 48 hours (n = 8 for each group, ** P,0.01). doi:10.1371/journal.pone.0067637.gthe solid tumour samples, such as vascular cells, alveolar macrophages, fibroblasts, and blood cells. The immunostaining on the lung cancer tissue microarrays showed less significant, which could be due to the low sensitivity of methodology comparing to the high sensitivity of real-time PCR. On the other hand, the relationship of TRPC expression with cell differentiation was further confirmed in the in vitro lung cancer cell culture model by application of the cell differentiation regulator ATRA, which significantly enhances the expression of TRPC3, 4, and 6. However, the TRPC5 and TRPC7 were still undetectable after ATRA treatment. The TRPC1 mRN.
