Study Silibinin effects on the improvement of immunogenic chemotherapy in CT26 colon cancer cell line

Abstract

Introduction: Cancer treatment has become a challenge all over the world. Despite immunotherapy is considered as a promising method for treatment of malignancies, it is limited, mainly due to the immunosuppression in tumor microenvironment (TME). Induction of immunogenic cell death (ICD) in cancer cells has been suggested to be an effective strategy to reduce immunosuppression in TME. Many chemotherapeutic agents, including oxaliplatin and some natural compounds have the ability to induce ICD. Silibinin is a flavonoid derived from Silybum marianum seeds that has been shown to have anticancer effects in various cancer models. The most important benefit of silibinin is its low toxicity. Aim: The aim of this study was to investigate the effects of silibinin on enhancing the ICD induced with chemotherapy in colon cancer cells. Methods: The growth inhibitory effect of silibinin was assessed by MTT assay. Annexin V/PI staining was used to evaluate the induction of apoptosis. Calreticulin (CRT) cell surface expression was assessed by flow cytometry. The level of High Mobility Group Box 1 (HMGB1) and Heat Shock Protein (HSP70) in the cell supernatant was measured by ELISA. Results: Silibinin significantly inhibited the growth of CT26 cells with IC50 being 105.8 µM. Silibinin increased the growth inhibitory effects of oxaliplatin in CT26 with CI being 1.07 indicating an additive effect. Treatment of CT26 with silibinin resulted in induction of an ICD which was indicated by a significant increase in the level of HMGB1 and HSP70 as well as an elevated level of CRT expression. While silibinin montherapy was found to induce ICD in CT26, combination therapy with silibinin and oxaliplatin didn’t result in significantly higher level of ICD in these cells. Conclusion: silibinin as a natural anticancer agent has good potential for inducing ICD.