Abstract

Breast cancer is the most common cancer and the second leading cause of cancer death in american and chilean women. Despite advances in early detection and the understanding of the molecular bases of breast cancer biology, current cancer therapies still exhibit limited success to improve quality of life and life expectancy of cancer patients. Major advances to control the growth of breast cancer cells have been focused on the antiestrogen receptor therapy, but some breast tumors have a variable response or do not respond to endocrine therapy suggesting that additional factors, in concert with tumor microenvironment may contribute to breast malignancy. We and others have explored the participation of the kallikrein-kinin system in breast cancer. Nevertheless, the presence of kininogens, the kinin-releasing substrates, or tissue kallikrein hk1, the enzyme responsible for kinin generation and activator of MMP-9 (gelatinase B) has not been accomplished yet. At the same time, the elevated levels of kinin peptides detected in cancer patients may have a close interaction with tumor cells and with other members of the tumor microenvironment such as neutrophils, fibroblast and endothelial cells. Until now, four reports have evaluated the role of kinin receptors in breast cancer cells and the underlying molecular mechanisms that are triggered after its activation. The B2 receptor increases cell proliferation, free intracellular Ca2+, protein kinase C activation, phosphorylation of extracellular-regulated kinases (ERK1/2) of the mitogen-activated protein kinases (MAPK) family, and produces partial transactivation of epidermal growth factor receptor (EGFR). We have demonstrated B1 receptor (B1R) expression in human breast tumors and in the MCF-7 and ZR-75 estrogensensitive breast cancer cells. In these cells, the B1R activation produces a proliferative effect that depends on the activity of EGFR and subsequent ERK1/2 MAPK phosphorylation. Moreover, B1R activation increases the expression and release of metalloproteases (MMP)-2 and -9, an event that may initiate matrix degradation and metastasis. Malignant behavior of breast cancer cells including the acquisition of an invasive phenotype, relays at least on NFκB and AKT-mTOR activation, COX-2 expression, ERK1/2, p38 and JNK MAPK phosphorylation. Our preliminary work shows that B1R activation in MCF-7 cells induces the phosphorylation of AKT, JNK and ERK1/2 MAPK and increases EGFR expression. The up-regulation of EMT-induced markers (vimentin, desmoplakin, α- smooth muscle actin, N-cadherin and cadherin 11) and over-expression of proteins involved in extracellular matrix remodeling and invasion (laminin, fascin, metalloproteases) together with a reduction of characteristic epithelial markers (E-cadherin), in invasive breast carcinomas have been associated with poor prognosis and major ability to form distant metastases. Our preliminary results show that B1R stimulation, in MCF-7 cells, triggers the morphological changes of EMT together with a reduction in E-cadherin and an increase in the levels of N-cadherin. Tumoral heterogeneity derives partially from the genetic and epigenetic instability and from signals that tumor cells receive from their microenvironment. In breast carcinomas, interactions of tumor cells with different components of the microenvironment such as the extracellular matrix and stromal cells (e.g. fibroblasts, leukocytes and endothelial cells) may affect tumor growth and metastasis formation. At this point, we have also observed that B1R stimulation results in the release of MMP-9 from neutrophils and MMP-2 from fibroblast and endothelial cells. Consequently, we propose that activation of the kinin B1R, expressed by stromal and tumoral cells, develops a molecular and cellular program that favors the acquisition of a malignant behavior in breast cancer cells. Our general goals are: I) To determine the molecular and cellular changes produced by B1R activation in breast cancer cells and II) To investigate the role of stromal cellular components on the behavior of breast cancer cells. Our specific goals are i) To determine the expression of kinin system components (kininogens and kallikrein hk1) in estrogen-sensitive and -insensitive breast cancer cells, to address the question as to whether the kinin system function in an autocrine or paracrine manner; ii) To dilucidate whether B1R stimulation activates AKT-mTOR, MAPK signaling, NFκB and/or induces COX-2 and EGFR expression in estrogen-sensitive and -insensitive breast cancer cells and iii) to relate these signaling pathways to epithelial-mesenchymal transition (EMT) and to develop an invasive phenotype in breast cancer cells; and iv) To determine the capacity of the B1R agonist to shift microenvironment to a growth and dissemination promoting state. Our major goal is to understand how the B1R modulates the tumor microenvironment to switch its dissemination promoting effects to a suppressive state able to promote a more controlled phenotype. Current cancer therapies exhibit limited success with efficacy in only 20-40% of cases suggesting that anticytokine or antipeptides therapy, for example using B1R antagonists, may be a new approach for the complex treatment of breast cancer.