PRRX1/FOXM1 reduces gemcitabin-induced cytotoxicity by regulating autophagy in bladder cancer

BACKGROUND: Bladder cancer (BC) is a common urological malignancy with high mortality worldwide. Many proteins can influence tumorigenesis by participating in cellular processes. Recently, abundant evidence has illustrated that paired related homeobox 1 (PRRX1) is closely related to the progression and development of human cancers. However, the function of PRRX1 in BC remains poorly understood. The aim of our study is to explore the role of PRRX1 in BC progression. METHODS: The expression of genes (PRRX1, FOXM1, LC3B, and Beclin-1) was examined through real-time quantitative polymerase chain reaction (RT-qPCR) and western blot. The expression of proteins (PRRX1, FOXM1, LC3B, and Beclin-1) was measured through immunohistochemistry. Cell viability and the half-maximal inhibitory concentration were detected using the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay. Cell apoptosis was assessed through flow cytometry. Autophagy was tested by GFP-LC3 immunofluorescence assay. Tumors were grown in nude mice in vivo, and the tumor size, volume, and weight were evaluated. RESULTS: In our study, PRRX1 was highly expressed in BC tissues and cells, and high PRRX1 expression resulted in poor overall survival in patients with BC. PRRX1 accelerated the viability and hindered the apoptosis of BC cells. It also weakened gemcitabine-induced cytotoxicity and strengthened gemcitabine-induced autophagy. PRRX1 was found to cooperate with forkhead box protein M1 (FOXM1) to influence downstream genes, and FOXM1 was found to regulate Beclin-1 and microtubule-associated protein 1 light chain 3 (LC3) genes to influence autophagy. PRRX1 up-regulated the expression of LC3 and Beclin-1 by cooperating with FOXM1. In rescue assays, FOXM1 reversed the effects of PRRX1 on gemcitabine-induced cytotoxicity and autophagy. Knockdown of PRRX1 enhanced the inhibitive effects of gemcitabine on tumor growth in vivo. CONCLUSIONS: PRRX1 reduces gemcitabine-induced cytotoxicity in BC cells by regulating the expression of the autophagy proteins LC3 and Beclin-1. This discovery suggests that PRRX1 may be a useful therapeutic biomarker for BC.