ABSTRACT
@#Objective: To study the regulatory effects and possible mechanism of long non-coding RNA plasmacytoma variant translocation 1 (lncRNA PVT1) on chemotherapy sensitivity to cisplatin (DDP) of colorectal cancer (CRC)．Methods: A total of 112 pairs of matched cancer and adjacent non-cancerous tissues were obtained from the CRC patients who underwent surgical resection in the First Affiliated Hospital of Xinxiang Medical University betweenApril 2006 and March 2011.All specimens were confirmed by pathological examinations. Tumor tissues and corresponding adjacent non-cancerous tissues from 30 cisplatin-sensitive CRC patients and 30 cisplatin-resistant patients were selected. Human CRC cell lines (HT29, SW480, HCT116, RKO and LoVo) and normal colonic epithelial cell line NCM460 were also collected for this study; and DDP-resistant RKO/DDP and LoVo/DDP cell lines were constructed. siPVT1, siNC, LV-PVT1 and LV-NC were transfected into LoVo and RKO cells or LoVo/DDP and RKO/DDP cells using lipofectamineTM2000. The expression of lncRNA PVT1 in CRC tissues and cells was tested by Real-time qPCR. CCK-8 assay, flow cytometry and WB were performed to test the effect of PTV1 knockout or enforcement on cell proliferation, apoptosis and expressions of apoptosis-related proteins, respectively. The CRC subcutaneous transplanted xenograft model was established on athymic nude mice to study the effect of PVT1 over-expression on tumor growth and DDP resistance. Results: PVT1 was highly expressed in the cancer tissues and CRC cells, and its expression was positively associated with cisplatin resistance of CRC. After knockdown of PVT1, the proliferation of cisplatinresistant CRC cells was significantly suppressed, while the apoptosis was significantly enhanced (P<0.05 or P<0.01); Mechanically, the levels of drug resistance-associated molecules, including MDR1 and MRP1, as well as the expression of anti-apoptotic Bcl-2 were significantly downregulated whereas the levels of pro-apoptotic Bax and cleaved caspase-3 were increased in PVT1-silenced DDP-resistant CRC cells. Over-expression of PVT1 reversely increased proliferation and decreased apoptosis of CRC cells (P<0.05 or P<0.01). In addition, PVT1 over-expression in CRC cells significantly promoted DDP-resistance in vivo (P<0.05). Conclusion: Collectively, knockdown of PVT1 expression can significantly suppress cell proliferation and promote apoptosis of DDP-resistant CRC cells. Overexpression of PVT1 can significantly promote the growth of CRC cells in vitro and transplanted xenograft in vivo. PVT1 regulates endogenous apoptosis pathways and further promotes the sensitivity of CRC cells to cisplatin chemotherapy via inhibiting the expressions of MDR1 and MRP1.