The role of cancer stem cells in immunotherapy for bladder cancer: An in vitro study

Objective Bladder cancer is characterized by frequent recurrence and progression. CD44+ cancer stem cells (CSCs) might be one of the main reasons for recurrence. Although Bacillus Calmette Guerin (BCG) has become a gold standard immunotherapy, after treatment recurrence frequently occur. Based on this knowledge, the aim of this study was to evaluate the changes in cytokine and chemokine expressions in bladder cancer and CSCs cultures in vitro with BCG only and in combination with IL2 and lymphocyte (MNCs) applications. Material and methods In this study, 3 cell lines of human bladder cancer cells with different characteristics (T24, 5637, and JMSU-1) and CD44+ bladder CSCs isolated by magnetic bead isolation (Miltenyl Magtech) were used. Bladder cancer cell lines and bladder CSCs in complete medium were cultured under humidified conditions of 37°C temperature in 5% CO2. BCG only and its combination with IL2 and MNCs were applied to bladder cancer cell lines and bladder CSCs for 24, 48, and 72 hours. Annexin V-PI was used to detect the percentages of apoptotic and necrotic cells in treatment groups and control groups. After treatments, total RNAs were isolated and converted to cDNA for each group and controls. Quantitative fold changes in terms of gene expression were measured by RT2–PCR array and fold changes for expression levels of genes were compared among groups. Eighty-four genes were analyzed in standard array of chemokines and cytokines (Biorad). Results BCG treatment with 7.32 µg/ml dose alone and in combination with IL2 (1000 IU/ml) and MNCs (1000 cells/ml) were found to be most effective on bladder cancer cells. When BCG and its combinations were applied to CSCs of the 3 cell lines, BCG treatment showed cytotoxic effect on CSCs as well as cancer cells. CSCs of 3 cell lines over expressed CXCL5, CCL8, CNTF, and CSF2 compared with cancer cells. Cancer cells over expressed IL6, TNSFF11, FASLG, and CXCL9 compared with CSCs. In all 3 cell lines, BCG application increased expression of CXCL5 and LTB and also decreased CCL20 and IL6. When BCG was combined with IL2 and MNCs, CXCL10, CXCL5, and IFNG were increased and CXCL12, IL6, and TNSF11 were decreased. BCG treatment of CSCs caused increases in ADIPOQ, CXCL10, and XCL1 and a decrease in CCL8. When IL2 and MNCs were combined with BCG, the expression of many cytokines and chemokines decreased. Conclusion BCG treatment changes the expression of many cytokines and chemokines in bladder cancer. The expression differs in 3 different cell lines and their CSCs. Immune modulation of each case differs from each other. The effectivity of BCG-based immunotherapy in bladder cancer on CSCs might decrease in combination with IL2. Our results indicate that recurrence after BCG treatment for bladder cancer may not occur mainly based on the CSCs hypothesis considering bladder cancer occurs at different loci of surface epithelium.