R Ojha1, S K Singh1, S Bhattacharyya2. 1. Department of Urology, Post Graduate Institute of Medical Education and Research, Chandigarh 160010032, India. 2. Department of Biophysics, Post Graduate Institute of Medical Education and Research, Chandigarh 160012, India. Electronic address: shalmoli2007@yahoo.co.in.
Abstract
BACKGROUND: Autophagy is a critical process in acquiring drug resistance in solid tumors. However, the mechanisms by which autophagy modulate resistance to chemotherapy in bladder cancer remains poorly understood. MATERIAL AND METHODS: We have established cisplatin resistant patient derived primary cultured cells as well as T24 bladder cancer cells. The autophagy flux as well as the effect of chemotherapeutic agents, gemcitabine (GC) and mitomycin (MM) were evaluated in these cells. Side population analysis, tumorisphere assay and expression of stemness genes were also studied to evaluate the role of autophagy during chemoresistance. The role of cytokines in autophagy induced chemoresistance was demonstrated. RESULTS: Our results show that resistant cells have higher basal autophagic flux. GC and MM led to increase in autophagy and combination of autophagy inhibitors synergistically inhibited bladder cancer cell growth. When autophagy was inhibited, only IFN-γ level was decreased in cytokine array. Blocking IFN-γ decreased JAK2 expression and reduced the autophagy. Inhibition of JAK2 decreased the proportion of cancer stem cell enriched side population, tumor sphere forming ability and led to decrease in expression of stemness genes. Combined treatment with inhibitors of JAK2 and autophagy led to inhibition in cell growth, reduced the levels of inflammatory cytokines and decreased the resistance gene expression. CONCLUSION: GC and MM treatment increased autophagy process via IFN-γ mediated JAK2 and STAT3 pathway. GENERAL SIGNIFICANCE: These findings support a key role of the autophagy in drug resistance. Thus, autophagy-based, "customized" combinatorial approaches may effectively manage resistance and relapse in bladder cancer.
BACKGROUND: Autophagy is a critical process in acquiring drug resistance in solid tumors. However, the mechanisms by which autophagy modulate resistance to chemotherapy in bladder cancer remains poorly understood. MATERIAL AND METHODS: We have established cisplatin resistant patient derived primary cultured cells as well as T24 bladder cancer cells. The autophagy flux as well as the effect of chemotherapeutic agents, gemcitabine (GC) and mitomycin (MM) were evaluated in these cells. Side population analysis, tumorisphere assay and expression of stemness genes were also studied to evaluate the role of autophagy during chemoresistance. The role of cytokines in autophagy induced chemoresistance was demonstrated. RESULTS: Our results show that resistant cells have higher basal autophagic flux. GC and MM led to increase in autophagy and combination of autophagy inhibitors synergistically inhibited bladder cancer cell growth. When autophagy was inhibited, only IFN-γ level was decreased in cytokine array. Blocking IFN-γ decreased JAK2 expression and reduced the autophagy. Inhibition of JAK2 decreased the proportion of cancer stem cell enriched side population, tumor sphere forming ability and led to decrease in expression of stemness genes. Combined treatment with inhibitors of JAK2 and autophagy led to inhibition in cell growth, reduced the levels of inflammatory cytokines and decreased the resistance gene expression. CONCLUSION:GC and MM treatment increased autophagy process via IFN-γ mediated JAK2 and STAT3 pathway. GENERAL SIGNIFICANCE: These findings support a key role of the autophagy in drug resistance. Thus, autophagy-based, "customized" combinatorial approaches may effectively manage resistance and relapse in bladder cancer.