The effect of SMAC mimetics on apoptotic and necroptotic cell death mechanisms on neuroblastoma cells

SMAC proteins bind to inhibitory apoptosis proteins within the cell and ubiquitinate them, causing their degradation or directly blocking them. In this way, they contribute to initiating the cell death response. SMAC mimetics are chemical agents developed by mimicking the 3D structure of SMAC proteins. SMAC mimetics have increased cell death and chemotherapy efficacy in many hematological or solid cancer cell lines. Neuroblastoma is the most common solid tumor of childhood. Although the survival rates of patients vary, the survival of especially high-risk group patients is still below fifty percent. There is a need to develop better treatments for high-risk patients. The study aimed to investigate whether LCL-161, one of the SMAC mimetic varieties, could be a candidate agent in the treatment of neuroblastoma. The study used two human neuroblastoma cell lines reflecting different prognostic phenotypes: MYCN-positive KELLY and MYCN-negative SH-SY5Y. The effect of LCL-161 as a mono agent or as a combined agent with the drugs Etoposide and Cisplatin on cell viability and apoptotic cell death was examined. It was determined that KELLY cells were more sensitive to LCL-161 and applied chemotherapy agents than SH-SY5Y cells. In combined use, LCL-161 increased the effectiveness of Cisplatin in these cell lines but failed to increase the effectiveness of Etoposide.In the continuation of the study, the effect of mono LCL-161 application on total gene expression changes was examined by RNA sequencing method, and its effect on apoptotic, anti-apoptotic, and necroptotic gene expressions was examined by real-time quantitative PCR method. RNA sequencing results showed that LCL-161 treatment led to a significant increase in the expression of endoplasmic reticulum stress (ER)-related genes in cells. PCR studies also confirmed the increase in the expression of ER-stress-related genes. Furthermore, an increase in some apoptotic genes and a decrease in some anti-apoptotic genes were detected due to LCL-161 treatment, while no change was observed in necroptotic genes. In conclusion, in our thesis study, we revealed for the first time that ER-stress-mediated pathways are involved in the LCL-161 response in cells and that this may play an essential role in the regulation of the apoptotic response induced by LCL-161.