The SP/NK1R system promotes the proliferation of breast cancer cells through NF-κB-mediated inflammatory responses.

backgroundNumerous molecules have been introduced to participate in the formation of breast cancer, the most common malignancy in women. Among them, neuropeptide substance P (SP) and its related receptor neurokinin-1 receptor (NK1R) have attracted unprecedented attention in tumorigenesis processes. In this study, we investigated the effect of the SP/NK1R pathway on the induction of oxidative stress in breast cancer and examine the therapeutic potential of NK1R inhibition in this malignancy.

methodsMCF-7 cells were treated with varying concentrations of SP and aprepitant, an FDA-approved NK1R antagonist, either as a single drug or in a combined modality. Resazurin assay was used to evaluate the anti-cancer ability of aprepitant. The alteration in the intracellular levels of reactive oxygen species (ROS) and gene expression were determined using ROS assay and the qRT-PCR analysis, respectively.

resultsThe stimulation of the SP/NK1R axis in the MCF-7 cells was coupled with the accumulation of ROS as well as upregulation of NF-κB and its related pro-inflammatory cytokines, including tumor necrosis factor (TNF)-α and IL-6. In contrast, the suppression of NK1R by aprepitant halted the viability of MCF-7 cells, at least partly due to p53-mediated upregulation of p21. Moreover, aprepitant attenuated the oncogenic properties of SP by preventing the oxidative property of this neuropeptide.

conclusionOverall, our results suggest that the SP/NK1R pathway might play a critical role in breast cancer pathogenesis, probably through inducing ROS/NF-κB-mediated inflammatory responses. Moreover, it seems that blockage of the axis has promising therapeutic value against breast cancer cells. Schematic representation proposed for the plausible mechanism by which the stimulation of the SP/NK1R might induce oxidative stress in breast cancer-derived MCF-7 cells. Once SP interacts with NK1R, this signaling axis could disturb the balance between the expression of p53 and NF-κB, an event that leads to the accumulation of ROS within MCF-7 cells. The produced ROS, in turn, elevates the expression of pro-inflammatory cytokines (TNF-α and IL-6) and downregulates the expression of p21. On the other hand, aprepitant, an antagonist of NK1R, could reduce the survival of proliferative capacity of MCF-7 cells by decreasing the intracellular levels of ROS and p53-mediated up-regulation of p21. Along with the effect on p53, aprepitant could also reduce the expression of NF-κB and its related pro-inflammatory cytokines.