VEGF-C inhibition reverses resistance of bladder cancer cells to cisplatin via upregulating maspin

Abstract

The aim of the current study was to elucidate the association between vascular endothelial growth factor C (VEGF-C) and resistance of bladder cancer cells to cisplatin and the underlying mechanism involving maspin. A total of 32 bladder cancer tissue samples from patients (18 males and 14 females with an average age of 65.9 years) were collected from the Fifth Affiliated Hospital of Zhengzhou University (Zhengzhou, China). All patients had undergone cisplatin-based combination chemotherapy. In addition, the BIU87 human bladder cancer cell line was cultured and a cisplatin-resistant subline (BIU87-CisR) was established by continuous exposure to cisplatin. The mRNA expression levels of VEGF-C and maspin in tissue samples, BIU87 cells and BIU87-CisR cells were analyzed by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Targeted inhibition of VEGF-C in BIU87-CisR cells was performed using small interfering (si)RNA technology and the alteration in levels of maspin was confirmed by RT-qPCR and western blot analysis. siRNA-treated and -untreated BIU87-CisR cells were divided into the following four groups: Control group (no drug treatment), 3 μM cisplatin treated group, 3 μM cisplatin + siRNA treated group and the siRNA treated group. Cell viability following treatment in each group was evaluated by the cell counting kit 8 assay. The cell cycle and apoptotic rate of BIU87-CisR cells was analyzed by propidium iodide (PI) staining and Annexin V-PI double staining with flow cytometry. Furthermore, pcDNA-maspin transfected BIU78-CisR cells were used to establish the effect of maspin on the sensitivity to cisplatin. VEGF-C expression in chemoresistant patients and BIU87-CisR cells was significantly increased compared with chemosensitive patients and normal BIU87 cells, respectively. By contrast, maspin levels were lower in chemoresistant patients and BIU87-CisR cells. Subsequent to VEGF-C inhibition, maspin expression was markedly increased. Cisplatin (3 μM) resulted in moderate proliferation inhibition of BIU87-CisR cells without siRNA pretreatment; however, significant inhibition was observed in the VEGF-C siRNA treated group. In addition, the cell cycle arrest and apoptosis induced by cisplatin was enhanced by VEGF-C inhibition. Overexpression of maspin was able to improve the sensitivity of BIU87-CisR cells to cisplatin. In conclusion, the resistance of bladder cancer cells to cisplatin may be induced by upregulation of VEGF-C, and inhibition of VEGF-C reverses resistance by elevating maspin expression levels.