Wnt 5a signaling is critical for macrophage-induced invasion of breast cancer cell lines.

Interactions between neoplastic and stromal cells contribute to tumor progression. Wnt genes, involved in cell migration and often deregulated in cancers, are attractive candidates to regulate these effects. We have recently shown that coculture of breast cancer cells with macrophages enhances invasiveness via matrix metalloproteases and TNF-alpha. Here we demonstrate that coculture of MCF-7 cells and macrophages leads to up-regulation of Wnt 5a in the latter. This was accompanied by activation of AP-1/c-Jun in MCF-7. Recombinant Wnt 5a mimicked the coculture effect. Wnt 5a was also detectable in tumor-associated macrophages in primary breast cancers. Experiments with agonists and antagonists of Wnt signaling revealed that a functional canonical pathway in the tumor cells was a necessary prerequisite; however, noncanonical signaling via Wnt 5a and the Jun-N-terminal kinase pathway was critical for invasiveness. It was also responsible for induction of matrix metalloprotease-7, known to release TNF-alpha. All these effects could be antagonized by dickkopf-1. Our results indicate that Wnt 5a is essential for macrophage-induced invasiveness, because it regulates tumor cell migration as well as proteolytic activity of the macrophages. The function of Wnt 5a as either a suppressor or promoter of malignant progression seems to be modulated by intercellular interactions. Wnt 5a detection in tumor-associated macrophages in breast cancer biopsies supports the assumption that similar events play a role in vivo.

Elevated concentrations of serum relaxin are associated with metastatic disease in breast cancer patients.

Relaxin (RLX) is known to induce remodeling of benign stromal tissues through upregulation of matrix metalloproteases (MMPs). Recently, we could show that RLX also induces MMPs in breast cancer cells and enhances in vitro invasiveness. To investigate its potential role for progression of breast cancer in vivo, RLX serum concentrations were determined in 160 breast cancer patients during post-surgical follow-up. RLX concentrations in cancer patients were significantly higher than in a control population of healthy blood donors and patients with various other diseases (0.47 versus 0.29 ng/ml, p < 0.0001). There was a significant difference between patients with metastases (0.62 ng/ml) and those without (0.38 ng/ml, p < 0.0001). Overall survival was shorter in RLX-positive ( > 0.4 ng/ml) than in RLX-negative patients (p = 0.016). Cox regression analysis showed that RLX was not an independent variable, in contrast to metastatic disease and primary lymph node involvement. Taken together, the detection of elevated RLX concentrations especially in patients with metastases supports the assumption that there is a role for RLX in tissue remodeling during breast cancer progression.

Relaxin enhances in-vitro invasiveness of breast cancer cell lines by up-regulation of matrix metalloproteases.

Until recently, relaxin (RLX) has been known predominantly for its effects on the reproductive system, where it induces remodelling of the extracellular matrix and up-regulation of matrix metalloproteases (MMPs). In solid cancers, tissue remodelling and MMP activation are essential for invasion and metastasis. We therefore investigated the effect of RLX on invasiveness and MMP expression of human breast cancer cell lines. Upon incubation with porcine RLX, the invasiveness of SK-BR3 cells was significantly increased. Similar effects could be achieved in MCF-7 cells, especially when RLX was combined with epidermal growth factor. Enhanced invasiveness was accompanied by up-regulation of MMP production and could be almost completely blocked by the MMP inhibitor FN 439. Zymography revealed increased secretion of MMP-2, -7 and -9, associated with up-regulated mRNA concentrations of MMP-2, -9, -13 and -14. mRNA expression levels of MMP-1, -3, -7, -8, -10, -11, -12 and of tissue inhibitors of metalloproteases-1, -2, -3 and -4 were either very low or not detectably influenced by RLX. Taken together, RLX enhances in-vitro invasiveness of breast cancer cell lines by induction of MMP expression. It remains to be clarified whether RLX might play a similar role in vivo and promote tumour progression.