Genistein Sensitizes Human Cholangiocarcinoma Cell Lines to Be Susceptible to Natural Killer Cells

SIMPLE SUMMARY: Cholangiocarcinoma (CCA) is a malignancy of bile duct epithelial cells, which has a poor prognosis and high mortality. Consequently, effective therapeutic options are required to improve the treatment outcome. In the present study, we demonstrated the effects of genistein on sensitizing CCA and enhancing natural killer (NK-92) cells to induce cytotoxicity of CCA cells. Genistein treatment could promote extrinsic apoptotic pathway to induce CCA cell death. Mechanistically, genistein treatment decreased the expression of anti-apoptotic protein, cFLIP, and significantly upregulated the expression of death receptors (Fas receptor; FasR, and TRAIL receptor; TRAIL-R), which might contribute to the increased susceptibility of CCA to NK-92 cells. ABSTRACT: Cholangiocarcinoma (CCA) is a lethal bile duct cancer, which has poor treatment outcomes due to its high resistance to chemotherapy and cancer recurrence. Activation of aberrant anti-apoptotic signaling pathway has been reported to be a mechanism of chemoresistance and immune escape of CCA. Therefore, reversal of anti-apoptotic signaling pathway represents a feasible approach to potentiate effective treatments, especially for CCA with high chemoresistance. In this study, we demonstrated the effects of genistein on reactivation of apoptosis cascade and increase the susceptibility of CCA cells to natural killer (NK-92) cells. Genistein at 50 and 100 µM significantly activated extrinsic apoptotic pathway in CCA cells (KKU055, KKU100, and KKU213A), which was evident by reduction of procaspase-8 and -3 expression. Pretreatment of CCA cells with genistein at 50 µM, but not NK-92 cells, significantly increased NK-92 cell killing ability over the untreated control, suggesting the ability of genistein to sensitize CCA cells. Interestingly, genistein treatment could greatly lower the expression of cFLIP, an anti-apoptotic protein involved in the immune escape pathway, in addition to upregulation of death receptors, Fas- and TRAIL-receptors, in CCA cells, which might be the underlying molecular mechanism of genistein to sensitize CCA to be susceptible to NK-92 cells. Taken together, this finding revealed the benefit of genistein as a sensitizer to enhance the efficiency of NK cell immunotherapy for CCA.