Elevated expression of IRS-1 associates with phosphorylated Akt expression and predicts poor prognosis of breast invasive ductal carcinoma

Overexpression of insulin receptor substrate 1 (IRS-1) has been reported to promote cell growth, atypical hyperplasia, and carcinogenesis, and phosphorylated Akt (p-Akt) is certified to be involved in many types of cancers such as breast invasive ductal carcinoma (BIDC). However, the relationship between IRS-1 and Akt, as well as the role of expression of IRS-1 in BIDC, has never been reported. The purpose of this research is to investigate the association between expression of IRS-1 and p-Akt proteins and clinicopathological features of BIDC by immunohistochemistry, as well as the survival status. The results showed that the percentage of either elevated expression of IRS-1 or positive p-Akt expression in BIDC was significantly higher than that in control breast tissue from noncancer patients (P < .001 and P = .001, respectively). Overexpression of IRS-1 was evidently associated with positive expression of p-Akt (r = 0.337, P < .001). Also, positive percentage of p-Akt expression was statistically different among different molecular subtypes of BIDC (highest in luminal B BIDC, P = .009). Furthermore, significantly worse overall survival was found in BIDC patients with high expression of IRS-1 and p-Akt than in patients with low expression (P = .006 and P = .004, respectively). The multivariate Cox proportional hazard regression analysis showed that high expression of IRS-1 and positive expression of p-Akt protein were independent poor prognostic factors for patients with BIDC (P = .022 and P = .046, respectively). In conclusion, we report for the first time that overexpression of IRS-1 protein is associated with expression of p-Akt, and overexpression of IRS-1 and positive expression of p-Akt might be independent biomarkers for poor prognosis in BIDC.