High RRM2 expression has poor prognosis in specific types of breast cancer

Abstract

Background: RRM2 plays an important role in different malignant tumors, but there are few studies in breast cancer. Public databases were used to analyze the expression of RRM2 in breast cancer and its prognostic value.

Materials and methods: A total of 2,509 breast cancer samples were downloaded from the METABRIC database. The relationship between RRM2 expression and clinical pathology was evaluated. Using the BCIP database and real-time-PCR, and western blotting, RRM2 mRNA and protein expression of RRM2 in breast cancer tissues and cell lines were evaluated. Univariate and multivariate analysis defined independent prognostic factors that affected the overall survival of patients with breast cancer. The Kaplan-Meier method was used to study the relationship between the high expression of RRM2 and overall survival and distant metastasis-free survival (DMFS) of breast cancer patients. Finally, We performed Gene Set Enrichment Analysis (GSEA) and obtained the relevant pathways associated with high expression of RRM2 potentially influencing breast cancer progression.

Results: RRM2 expression was significantly correlated with age, tumor size, grade, menopausal status, molecular typing, ER, PR, and Her-2 of patients with breast cancer(P<0.05). Univariate and multivariate regression analysis showed that RRM2, the number of positive lymph nodes, ER, Her-2, tumor size, and tumor stage can be used as independent prognostic factors for overall survival of patients with breast cancer. Kaplan-Meier analysis showed that in patients with Luminal A and Normal like breast cancers and Stage1 and stage2 breast cancers, patients with high expression of RRM2 had worse overall survival and DMFS. The analysis of the GSEA pathway showed that RRM2 is mainly enriched in the ERBB signaling pathway and other pathways.

Conclusion: The high expression of RRM2 has a worse prognosis in patients with breast cancer with specific features. It can be used as a biomarker for the prognosis of breast cancer.

Fig 1. Expression of RRM2 in breast cancer tissues from public databases and breast cancer cell lines by qRT-PCR.

(A) METABRIC; (B) TCGA Agilent; (C) TCGA RNA-seq; (D) GSE5364; (E) MDA-MB-453; (F) MDA-MB-231; (G) MCF-7; and (H) BT474.

Fig 2. The mRNA and protein expression levels of RRM2 in breast cancer.

(A) The relative expression level of RRM2 mRNA was higher in breast cancer tissues than in adjacent normal tissues. (B) The protein expression of RRM2 was higher in breast cancer tissues and breast cancer cell lines. (C) Quantitative results of protein expression levels obtained by Image J.

Fig 3. The scatter plot shows the expression of RRM2 in the clinicopathological characteristics of METABRIC.

(A) Age; (B) Molecular subtype; (C) Grade; (D) Menopausal state; (E) Tumor stage; (F) Tumor size; (G) Lymph Node; (H) Her-2 status; (I) ER status; (J) PR status.

Fig 4. Forest plots showing univariate and multivariate Cox regression analysis of the overall survival of breast cancer patients.

RRM2, the number of positive lymph nodes, ER status, Her-2 status, Tumor size, and Tumor stage were significantly correlated with overall survival (P<0.05). (A): Univariate Cox analysis. (B): Multivariate Cox analysis.

Fig 5. Overall survival and ROC curve.

(A): Breast cancer patients with High-RRM2 expression have poor overall survival compared to those with Low-RRM2 expression. (P<0.05). (B): The ROC curve shows the diagnostic value of RRM2 for patients with breast cancer. (C): Overall survival analysis showed that patients with the Luminal A subtype of breast cancer have the best prognosis, and the Basal-like subtype has the worst prognosis in 1,350 breast cancer patients. (D): The high expression of RRM2 has poor overall survival in stage 1 and stage 2 breast cancer patients. (P<0.05).

Fig 6. The effect of RRM2 expression on the overall survival of breast cancer patients with different molecular subtypes.

We found that in Luminal A and Normal like breast cancers, the High RRM2 expression group had poor overall survival. (A) Normal-like; (B) Claudin-low; (C) Her-2 enriched; (D) Luminal A; (E) Luminal B; (F) Basal-like.

Fig 7. The effects of RRM2 high expression and low expression on the overall survival of breast cancer patients.

Our study found that the RRM2 high expression group had a poor prognosis among stage1 and stage2 breast cancer patients. However, there was no significant difference in stage3. (A) stage 1; (B) stage 2; (C) stage 3.

Fig 8. The effects of RRM2 expression on the DMFS of breast cancer patients.

(A) All breast cancer patients, (B) Luminal A, (C) Luminal B, (D) Her-2 enriched, and (E) Basal-like.

Fig 9. GSEA analysis showed the KEGG signaling pathway in breast cancer patients with high expression of RRM2.