Objective: We aimed to investigate the expression, diagnostic and prognostic values, and potential molecular mechanisms of the origin recognition complex (ORC) in breast cancer (BC).
Methods: Kaplan–Meier estimation was used to assess the prognostic value of ORC  genes, and Oncomine, TCGA, GEO and ULCAN databases were used to analyze their expression in BC. Wilcoxon rank-sum tests were used to evaluate the relationship between ORC  gene expression levels and BC clinicopathological features. Receiver operating characteristic (ROC) curves were used to assess the diagnostic value of ORC  genes in BC. Survival analysis was performed using Kaplan–Meier estimation and Cox regression. A nomogram was constructed to predict 1-, 3-, and 5-year survival probabilities in BC. Gene set enrichment analysis (GSEA) and immune infiltration were used to investigate potential molecular mechanisms of the ORC.
Results: ORC1L  and ORC6L  were highly expressed in BC compared with healthy tissue, while ORC5L  expression patterns were inconsistent; no significant differences in ORC2L, ORC3L  or ORC4L  expression were observed between BC and healthy tissues. ORC1L  and ORC6L  expression levels were significantly correlated with age, tumor (T) stage and molecular subtype; ORC5L  expression was significantly correlated with age and number of nearby lymph nodes with cancer (N stage). ORC6L  expression had the highest diagnostic value in BC and was an independent prognostic factor for poor overall survival (OS). ORC6L may be involved in cell cycle progression and may regulate cancer signaling pathways, including NF-κB, P53, and WNT, in BC. ORC6L  expression was also associated with immune infiltration.
Conclusion: ORC1L  and ORC6L  are highly expressed in BC; ORC6L  has a high diagnostic value and is an independent prognostic factor for poor OS. ORC6L may be involved in the initiation and progression of BC by regulating cell cycle progression, promoting cancer signaling pathway activation, and influencing tumor immune cell infiltration.
Keywords: origin recognition complex, breast cancer, prognostic biomarker, nomogram, gene set enrichment analysis, immune infiltration