m5C related-regulator-mediated methylation modification patterns and prognostic significance in breast cancer

Background: Breast cancer (BC) is the most common malignancy worldwide. 5-methylcytosine (m 5 C) is closely related to cancer and its mechanism in BC remains unclear. We aimed to assess the expression of m 5 C regulators involved in BC and investigate their correlation with the prognosis of BC. Methods: BC samples from TCGA and GEO databases were respectively analyzed as the training and testing sets, and identified their m 5 C modification patterns based on the differential expression of m 5 C-related regulators and construct an m 5 C scoring system. Subsequently, we evaluate the value of m 5 C modification in predicting prognosis, investigate the underlying pathways and functions associated with m 5 C modification, identify m 5 C modifications related to the infiltration of immune cells in the tumor microenvironment and assess the patients' potential response to pharmacotherapy based on m 5 C patterns. Results: Three distinct m 5 C modification patterns were identified in the training dataset. Based on the m 5 C-related differentially expressed genes, the m 5 Cscore was constructed, and divided BC patients into high and low m 5 Cscore groups. Patients with a high m 5 Cscore had more abundant immune cell infiltration and better prognosis. However, a low m 5 Cscore was linked to an enhanced response to immunotherapy. Finally, the potential roles of the m 5 Cscore were validated in the testing dataset, and the results demonstrated the stability of the m 5 Cscore and its independent prognostic value. Conclusions: This study revealed the m 5 Cscore is a potential tool for evaluating m 5 C modification patterns and immune cell infiltration in individual patients and has the potential to be a novel prognostic marker for BC.