Effects of Substance P antagonists on mouse metastatic breast carcinoma cells

Distant metastasis is the leading cause of death in breast carcinoma. Breast carcinoma metastasizes frequently to bone, liver, and brain. In order to device effective treatments, features of the cancer cells metastasized to distant organs should be explored and new treatments should be tested on metastatic cells. Substance P, a member of Tachykinin family is found in both neuronal and non-neuronal cells. The role of Substance P in cancer progression and dissemination is not entirely known and there are conflicting results in the literature. In order to clarify these differences, specific antagonists of NK1 (neurokinin 1) and NK2 (neurokinin 2) receptors which mediate the effects of Substance P should be used in different metastatic cancer models. In this study, we aimed to examine the effect of substance p and of its antagonists in different metastatic breast cancer models. In our this study, we investigated the effect of NK1 and NK2 receptor antagonists (RP 67580 and GR 159897) on the proliferation of the metastatic breast cancer cells (4THM, 4TBM, 4TLM) as well as the parental cells (4T1) and non-metastatic cells (67NR). The effects of antagonists on phosphorylation of AKT, ERK and p38, proteins that play a critical role in intracellular signaling pathways, were examined using Western Blot. Given the fact that SP and its receptors ( NK1 and NK2) play a significant role in regulation of inflammation, we also examined the changes in secretion of MIP-2, an inflammatory and angiogenic factor using ELISA. We found that NK1 and NK2 receptors were over expressed in metastatic breast cells compared to non-metastatic cells. SP and SP methyl ester did not alter the growth rate of metastasis breast cancer cells. NK1 receptor antagonist at 30 μM dose (relatively high dose) inhibited cell growth and induced cell death. In accordance, NK1R antagonists enhanced phosphorylation of Akt. This effect was not observed in 67NR, non-metastatic breast cancer cells. NK1R antagonist, however, significantly suppressed proliferation of 67NR cells, an effect less prominent than metastatic cells. NK2 receptor antagonist (30 µM) also suppressed cell proliferation in all cell lines examined but the effect was less than the effects of NK1R antagonist. Differently NK2R antagonist also increased phosphorylation of P38 and increased MIP-2 secretion. SP did not alter the effects of NK1R and NK2R antagonists on cell proliferation. Key Words : SP, NK1 receptor antagonist, NK2 receptor antagonist, metastatic breast cancer , MIP-2.