Inhibition of Protein Kinase c-Src Reduces the Incidence of Breast Cancer Metastases and Increases Survival in Mice: Implications for Therapy

Abstract

c-Src is a proto-oncogene, belonging to the nonreceptor protein kinases family, which plays a prominent role in carcinogenesis. In this study, we tested the hypothesis that c-Src could promote breast cancer metastasis acting on several cell types and that pharmacological disruption of its kinase activity could be beneficial for the treatment of metastases. Female BALB/cnu/nu mice were subjected to intracardiac injection of the human breast cancer cells MDA-MB-231 (MDA-231), which induced prominent bone and visceral metastases. of a c-Src kinase-dead dominant-negative construct (MDA-231-Src DN ) resulted in reduced morbidity, lethality, and incidence of metastases similar to the mice treated with the inhibitor. An analogous beneficial effect of c-Src inhibition was observed in subcutaneous and intratibial implanted tumors. In vitro, c-Src suppression reduced MDA-231 cell aggressiveness. It also impaired osteoclast bone resorption both directly and by reducing expression by osteoblasts of the osteoclastogenic cytokines interleukin-1␤ and interleukin-6, whereas parathyroid hormone-related peptide was not implicated. c-Src was also modestly but consistently involved in the enhancement of endothelial cell proliferation in vitro and angiogenesis in vivo. In conclusion, we propose that c-Src disruption affects the metastatic process and thus is a therapeutic target for the treatment of breast cancer.Breast cancer is a relatively common tumor, with an estimated incidence of 1.2 million new cases diagnosed worldwide every year (Henderson et al., 1993). The outcome of patients mainly depends on the development of distant metastases (Greenberg et al., 1996). Bone is the principal metastatic site in patients with mammary carcinomas (James et al., 2003), of whom approximately 20% survives for more than 5 years, whereas those with minor metastases in the bone can survive up to 10 years or more. In contrast, visceral metastases, although less common, are more likely to be fatal with a higher risk of early death.Consistent evidence suggests the involvement of the protooncogene c-Src in the development and progression of many human cancers, including breast carcinomas (Otthenoff-Kalff et This work was supported by the E.C. Grant METABRE (LSHM-CT-2003-503049) and by a grant from the Associazione Italiana per la Ricerca sul Cancro (AIRC).Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.

c-Src and IL-6 inhibit osteoblast differentiation and integrate IGFBP5 signalling

“…4b). BALB/c-nu/nu mice were subjected to intracardiac injection of MDA-MB-231 cells and treated with CGP76030, which, as expected, significantly reduced the incidence of bone metastases compared with untreated mice 17 ( Fig. 4c).…”

“…A potential therapeutic impact could be predicted from these results, hypothesizing that a c-Src inhibitor could be used in cancer-induced bone diseases not only to impair osteoclast bone resorption and tumour cell proliferation 17,26,27 , but also to reduce IL-6 production and, therefore, its deleterious systemic effects on the body. Indeed, clinical trials are in progress for cancer using the c-Src inhibitor Saracatinib, which, in our opinion, associated with the IL-6 receptor-neutralizing antibody Tucilizumab, may open new avenues for combination treatment of patients.…”

“…To investigate the significance of the interplay between c-Src and IL-6 on bone in vivo, we evaluated the IL-6 mRNA expression in WT and IL-6 transgenic (TG) mice, overexpressing human IL-6 in the circulation and treated with the pharmacological c-Src inhibitor, substituted 5,7-diphenylpyrrolo[2,3-d]-pyrimidine, CGP76030 (ref. 17). As in the TG mice the human IL-6 transgene is constitutively overexpressed and, therefore, not regulated, we analysed the expression of the endogenous (mouse) IL-6.…”

“…Breast cancer bone metastases are inhibited by c-Src inactivation due to its antiresorptive and antiproliferative effects 17 . To assess whether this condition influenced IL-6 metabolism, we evaluated IL-6 in mice carrying bone metastases induced by the human breast cancer MDA-MB-231 cells.…”

Dual targeting of Src and ER prevents acquired antihormone resistance in breast cancer cells

“…Overexpression of the non-receptor tyrosine kinase, Src, and/or an increase in its kinase activity has been associated with the development and progression of a number of human malignancies including breast cancer [12,13] where it has been implicated in metastatic progression [14]. Interestingly, it has recently been reported that expression of activated Src is associated with a reduced recurrencefree survival in ductal carcinoma in situ [15].…”