Evaluation of serum level of substance P and tissue distribution of NK-1 receptor in breast cancer.

Breast cancer is the second leading cause of cancer death in women with increasing incidence. Hence, finding a diagnostic factor and/or potential drug target could lead to an earlier diagnosis or a more effective therapeutic protocol. It is shown that substance P (SP) through its receptor neurokinin-1 (NK1R) could initiate tumor cell proliferation, angiogenesis, and migration. This was a case-control study on 41 women with breast cancer and 34 healthy controls. Serum level of SP was measured using an ELISA method, and immunohistochemistry staining was performed to study NK1R expression in different cell compartments. Assessing serum SP values of patients showed significantly higher levels than those of healthy individuals. However, no significant correlation was found between SP levels and tumor criteria, but between SP and HER-2. Moreover, the percentage, intensity of staining as well as tissue distribution of NK1R were significantly higher in tumor tissues as compared with controls. Increased serum SP levels and NK1R tissue distribution were observed in patients with breast cancer as compared with their controls, highlighting the involvement of SP/NK1R complex in breast cancer incidence. NK1R profound expression in tumor cell cytoplasm and its significant correlation with the majority of cancer features can be of importance to be taken into consideration as a possible potential therapeutic target in future targeted therapeutic strategies. Furthermore, cytoplasmic expression of NK1R can be suggested as a potent prognostic factor as it has shown significant correlation with TNM and tumor grade.