3176 - The Molecular Mechanism of RCC1 - Mediated Promotion of Ferroptosis and Enhancement of Oxaliplatin Sensitivity via the ATM Pathway in Colorectal Cancer
Presenter(s)
Y. Zhao1, and Y. Liu2; 1Peking University Shenzhen Hospital, Shenzhen, China, 2Department of Radiation Oncology, Peking University Shenzhen Hospital, Shenzhen, China
Purpose/Objective(s): Colorectal cancer (CRC) ranks among the most prevalent malignancies globally, and China bears the highest burden of new CRC cases. In systemic therapy, chemoresistance currently poses the most formidable challenge in clinical treatment. Our previous research has revealed that the regulator of chromatin condensation 1 (RCC1) is highly expressed in CRC tissues, which is associated with a poor prognosis. Knocking down RCC1 can arrest the CRC cell cycle at the G1 phase and suppress cell proliferation. Simultaneously, the sensitivity of CRC to oxaliplatin - a common chemotherapy drug - is inhibited. Therefore, identifying molecular markers of oxaliplatin resistance in CRC and elucidating the underlying molecular mechanisms of oxaliplatin chemoresistance are of great clinical significance.
Materials/Methods: CRC cell models with stable RCC1 overexpression or knockdown were established. The in - vitro mechanism by which RCC1 affects CRC sensitivity to oxaliplatin was investigated using apoptosis drug - sensitivity tests, TUNEL assays, and comet assays. The expression levels of key proteins in DNA repair pathways, such as ATM, ATR, CHK1, and CHK2, were measured, along with the levels of ROS, iron content, and MDA expression. Additionally, the expression levels of these proteins were reversed when an ATM inhibitor, the ferroptosis promoter erastin, or the ferroptosis inhibitor ferrostatin - 1 was used. The binding sites of relevant transcription factors to the RCC1 promoter region were predicted using JASPAR and then experimentally verified.
Results: RCC1 was found to inhibit ATM phosphorylation and down - regulate the expression of p - CHK2, pp53, and p21. Upon treatment with oxaliplatin, the inhibition of p21 can elevate the level of ferroptosis, thereby enhancing the chemotherapy sensitivity of CRC cells. Meanwhile, the inhibition of ATM down - regulates p21 and up - regulates cyclinD1, which promotes the progression of the CRC cell cycle and leads to malignant progression. Through database prediction and further experimental validation, c - Myc was identified as the upstream regulatory transcription factor of RCC1. On one hand, RCC1 reduces the DNA damage repair capacity of cells; on the other hand, it down - regulates the expression of molecules like p21, resulting in an increased level of ferroptosis in tumor cells and enhanced sensitivity of CRC cells to oxaliplatin. Moreover, the p21 down - regulated by RCC1 can increase the expression of cyclin D1 and promote CRC cell proliferation.
Conclusion: Our study has elucidated the molecular mechanism by which RCC1 enhances the chemotherapy sensitivity of CRC via the ATM pathway. This finding is beneficial for predicting the sensitivity of CRC patients to oxaliplatin treatment and for exploring novel targets to reverse oxaliplatin resistance. Our study provides an experimental basis for the future development of new drugs to reverse oxaliplatin resistance.