Objective  To analyze the expression levels of miR-27a-3p mRNA and Yes-associated protein 1 (YAP1) mRNA in breast cancer, and to explore their relationships with clinicopathological features and the survival prognosis of patients.

Methods A total of 130 breast cancer patients who underwent mastectomy in our hospital between January 2019 and January 2021 were enrolled. The expression levels of miR-27a-3p and YAP1 mRNA in breast tumor tissues and adjacent normal breast tissues were assessed by qRT-PCR. Furthermore, the relationships between their expression and clinicopathological features, as well as the survival prognosis of patients, were investigated.

Results Compared with adjacent normal breast tissues, the expression of miR-27a-3p mRNA in breast tumor tissues was lower (P < 0.05), while that of YAP1 mRNA was higher (P < 0.05). A negative correlation was observed between the expression of miR-27a-3p mRNA and YAP1 mRNA in breast tumor tissues (r = −0.456, P < 0.05). The expression of miR-27a-3p mRNA was correlated with tumor diameter, histological grade, tumor staging by the TNM system, lymph node metastasis, and vascular invasion in patients with breast cancer (P < 0.05). The YAP1 mRNA expression was correlated with histological grade, tumor staging by the TNM system, lymph node metastasis, and vascular invasion (P < 0.05). Kaplan-Meier survival analysis revealed that the 3-year overall survival rate of the miR-27a-3p low-expression group was 71.60% (48/67), which was lower than the 91.50% (54/59) of the miR-27a-3p high-expression group (log-rank χ² = 8.211, P = 0.004). The 3-year overall survival rate of the YAP1 high-expression group was 73.80% (45/61), lower than that of the YAP1 low-expression group (87.70%, 57/65) (log-rank χ²=4.429, P = 0.035). Multivariate regression analysis indicated that lymph node metastasis (hazard ratio HR = 1.409; 95% CI, 1.057-1.644; P = 0.046), vascular invasion (HR = 1.541; 95% CI, 1.076-1.869; P = 0.045), low miR-27a-3p mRNA expression (HR = 0.593; 95% CI, 0.388-0.925; P = 0.018), and high YAP1 mRNA expression (HR = 0.628; 95% CI, 0.405-0.912; P = 0.022) were relevant factors affecting the 3-year overall survival of patients with breast cancer.

Conclusion A significant downregulation of miR-27a-3p mRNA and upregulation of YAP1 mRNA are observed in breast tumor tissues. The low expression of miR-27a-3p mRNA and the high expression of YAP1 mRNA are associated with adverse clinicopathological features and poor survival prognosis, and are risk factors affecting the 3-year overall survival of patients with breast cancer. They show promise as new potential therapeutic targets for breast cancer.