Impact of HIF-1alpha and PKM1 expression on acquisition of paclitaxel resistance in gastric cancer

Introduction: In gastric cancer patients, one of the greatest obstacles to effective chemotherapy is the development of chemoresistance. It has been previously noted that HIF-1α was concerned with chemoresistance acquisition, and it was recently noted about the association of PKM1 and chemoresistance. The purpose of this study was to identify the effect of HIF-1α and PKM1 expression in leading to acquired chemoresistance using established paclitaxel-resistant gastric cancer cell line. Methods: Cancer cell line resistant to paclitaxel was established from MKN45 by stepwise exposure. The expressions of HIF-1α, apoptosis, VEGF, multidrug transporters and glycolytic enzyme were examined by western blotting, ELISA and Immunohistochemistry. We also assessed the tumor proliferation by subcutaneous tumor and peritoneal dissemination of mouse xenograft model. Results: The resistance index (RI) was 6.1 by determining as the ratio of the IC50 of rMKN45-PTX / IC50 of MKN45. Expression of NF-kB and HIF-1α was increased in rMKN45-PTX compared with those in the parent cells. Expressions of Bax and caspase-3 were significantly downregulated in rMKN45-PTX (p<0.05). In contrast, an increased expression of Bcl-xL, P-gp, MRP, and VEGF (2200 pg/ml) was observed in rMKN45-PTX. The expression level of PKM1 was 2 times up-regulated in rMKN45-PTX (p<0.05), on the other hand, PKM2 was almost similar to MKN45. We demonstrated that mouse subcutaneous tumors derived from rMKN45-PTX were significantly larger than those from MKN45 cells (1450 mm3 vs 750 mm3, p<0.05). Peritoneal dissemination model of rMKN45-PTX also showed larger than those of MKN45 (0.8 g/16 nodules vs 0.4 g/7 nodules, p<0.05). HIF-1α was key molecular of chemoresistance acquisition, which might be impacted the angiogenesis, cell proliferation, anti-apoptosis and multidrug transporter. Furthermore, PKM1 might be important molecular in chemoresistance acquisition. Conclusion: Under the stress of chemotherapeutic agent exposure, high expression of HIF-1α affects downstream various genes. Although the underlying mechanism is unknown, our data suggest that PKM1 is also a molecular target for gastric cancer treatment.