Investigation of the effect of quercetin on cell death pathways in HCT-116 and HT-29 colon cancer cell line

Cancer is a multi-step and long-term process and is characterized by the uncontrolled division and growth of an unhealthy cell followed by the absence of tumor-producing cell death. Colorectal cancers are among the most common cancers in the world. It is one of the first five types of cancer in our country and its incidence is increasing. One of the major challenges in cancer research is how to kill cancer cells effectively before healthy cells are destroyed, and at this point, knowing the death pathways is critical to treating cancerous cells. Discovered in recent years, ferroptosis is known as a new type of programmed cell death induced by iron dependence, and it has been confirmed that induction of ferroptosis in cancer cells reverses the resistance of multiple chemotherapeutics and reduces cancer resistance, as cancer cells exhibit greater demand for iron than normal cells to promote growth. These studies have shown that ferroptosis plays an important role as an important regulator in tumor formation and development. Quercetin, one of the flavonoids, is a metabolite known to be successful in preventing cancer, stopping its progression, and reducing the side effects of conventional cancer treatments. In this study, which was conducted to reveal the effects of quercetin inhibitory effects on colon cancer, on cell death pathways, it was aimed to evaluate the potential effects of quercetin molecule on apoptosis and ferroptosis by determining the effects of quercetin molecule in combination with a chemotherapy agent in colon cancer cell lines and the effects of single use on cell viability. In our study, first of all, quercetin and chemotherapeutic agent cytotoxic concentrations were determined in HT- 29 and HCT-116 cells by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) test. HCT-116 and HT-29 cells, which were then incubated for 24 hours with cytotoxic quercetin and chemotherapeutic agent, Apoptotic Protease Activating 16 Factor-1(APAF-1), Human Caspase-3 Protein (CASP-3), Long Chain Fatty Acid-CoA Ligase (ACSL4) and Glutathione Peroxidase 4 (GPx4) levels were determined by enzyme-linked immunosorbent assay method (ELISA). In the study, it was determined that the quercetin molecule alone activates the apoptotic pathway by increasing APAF-1 and CASP-3 biomarkers in both colon cancer cells compared to the control group. In GPx4 and ACSL4 biomarkers, it was determined that the combined application had a synergistic effect on cancer cells by increasing ACSL4 and decreasing GPx4, inducing the ferroptotic pathway. The data from this study can provide basic data for combined or other alternative approaches against colon cancer. Further investigation of the ferroptosis signaling pathway for cancer treatment may contribute to studies on the use of the active substance.