Abstract

Breast cancer is the most common cancer that affects women worldwide. The latest investigation on the incidence of this disease in North America shows that 114,900 women will be diagnosed with breast cancer each year and another 37,000 will die in the same period [1-2]. The same study indicates that the number of deaths will double by 2030, reaching 74,000 annual deaths. In fact, 90% of breast cancer deaths are the result of metastasis, primarily to the bone, lungs, liver, brain and regional lymph nodes. In Chile, breast cancer produces 13/100,000 deaths every year, being the first cause of death for cancer in women [3]. Advances in diagnosis and treatment have rendered most solid tumors largely curable if they are diagnosed and treated before dissemination. However, once they spread beyond the initial primary location, these cancers are usually highly fatal [1]. The resistance to radiotherapy, endocrine therapy and chemotherapy in locally advanced and metastatic disease remains major therapeutic challenges [4]. A unique approach is not enough and therefore the search and identification of new regulatory molecules may contribute to antitumoral therapy. Over the last decade, it has become increasingly clear that inflammation and components of the tumor microenvironment play a major role in the pathogenesis of cancer [5-9]. Consistent with human evidence, murine models clearly indicate that inflammatory molecules, released by the tumor, resident immune cells or secreted systemically, are permissive for tumor development, invasiveness and malignant behavior of breast cancer cells [6-9]. In addition, it is known that not only cellular proteins (i.e. the proteome), but also proteins secreted or shed into the tumor microenvironment (i.e. the secretome) play a key role in the processes that contribute to the malignant nature of a tumor [10-11]. A few years ago, patients with breast cancer were found to have high levels of serum peptides with a molecular mass below 3 kDa (serum peptidome). Among those peptides, the agonist of the kinin B1 receptor (B1R) kinin, des[Arg9]bradykinin and its precursor, bradykinin, are at higher levels in the sera of breast cancer patients than in normal subjects [12-13]. The effects of B1R agonists on breast tumor have been barely explored, highlighting the importance of determining what their role in tumor progression is. These kinin peptides have proinflammatory activities and the expression of their receptors is increased when the cells are exposed to a proinflammatory microenvironment consisting of high levels of TNF-α and IL-1β. Kinin peptides are formed by the enzymatic action of two serine proteases, true tissue kallikrein (KLK1) and plasma kallikrein (KLKB1). They act on circulating or locally synthesized precursors known as kininogens. Once generated, bradykinin and Lys-bradykinin undergo hydrolysis by carboxypeptidases N and M, which remove the C-terminal arginine off the kinin molecule. This lead to the formation of des[Arg9]-bradykinin (DBK) or Lys-des[Arg9]-bradykinin (LDBK) [14,15]. DBK and LDBK are two ligands that exert their biological actions through a 7-transmembrane domains G protein-coupled receptor known as B1R [16,17]. Recent evidence has shown that expression of KLK1, carboxypeptidase M and kinin receptors are enhanced in a number of human tumors and cancer cell lines. Stimulation of B1R triggers release of matrix metalloproteases (MMPs) and modulates cell proliferation and migration/invasion of tumor cells [17-23]. By contrast, kinin receptor antagonists cause apoptosis of cultured prostate cancer cells and show therapeutic benefit in animal models for other types of cancer [24,25]. We have demonstrated the expression of all components of kallikrein kinin system (kininogens, kallikrein and B1R) in breast cancer cell and tissues. [26 Ehrenfeld et al, manuscript accepted]. Moreover, the B1R activation controls the expression of some kallikrein-related peptidases, proteases influencing tumor biology. In addition, the reported expression of various components of the kinin system in others cells of tumor microenvironment could facilitate kinin generation in situ and contribute also to explain the higher levels of kinin peptides reported in the sera of breast cancer patients [12,17] In brief, evidence remarking the importance of kinin peptides and their receptors in breast cancer includes: i) an increase generation of kinin peptides in breast cancer patients [12], ii) kinin receptors and other components of the system present in the tumor microenvironment may support an autocrine-paracrine generation of kinins [17; 26 Ehrenfeld et al, manuscript submitted, see annexes] and iii), activation of both B1 and B2 receptors in breast cancer cells has been shown to stimulate cell proliferation, activation of ERK1/2 MAPK pathway and secretion of proteases associated with invasiveness [21, 27-29]. Thus, our main aim is to determine if “Kinin B1R stimulation shifts tumor microenvironment cells (endothelial and tumoral) towards a dissemination promoting state”. In our approaches we will determine whether kinin B1R stimulation favors two fundamental actions: a) increase the expression/secretion of invasion/metastatic modulators and b) angiogenesis and vascular permeability.