Normal mammary fibroblasts induce reversion of the malignant phenotype in human primary breast cancer.

BACKGROUND/AIM: The tumor microenvironment plays a major role in tumor growth and progression. Its manipulation can lead to a reversion of the malignant phenotype. Here we explored the ability of normal mammary fibroblasts (HMFs) to induce reversion of the malignant phenotype of primary breast carcinoma cells (PBCs) in a three-dimensional (3D) context. MATERIALS AND METHODS: PBCs were isolated from 13 primary breast carcinomas and cultured in 3D collagen-I gels as mono- or co-culture with HMFs. RESULTS: In five co-cultures, PBCs exhibited reversion of their malignant phenotype, whereas PBCs in matched monocultures exhibited disorganized growth. Reversion, defined as the restoration of the complete baso-apical polarity axis, was confirmed with established polarity markers. Secretion of the tissue-specific glycoprotein MAM-6 into the acinar lumens and deposition of basement membrane indicated functional differentiation. Gene expression analysis revealed a set of differentially regulated genes which possibly affect the reversion process. These included MAL, ELF5, MAP6, ZMYND11 and SQLE. CONCLUSION: These findings highlight the significant role of fibroblasts in regulating the carcinoma phenotype.

Mammary fibroblasts regulate morphogenesis of normal and tumorigenic breast epithelial cells by mechanical and paracrine signals.

Stromal factors play a critical role in the development of the mammary gland. Using a three dimensional-coculture model we demonstrate a significant role for stromal fibroblasts in the regulation of normal mammary epithelial morphogenesis and the control of tumor growth. Both soluble factors secreted by fibroblasts and fibroblast-derived modifications of the matrix compliance contribute to the regulation of epithelial cell morphogenesis. Readjustment of matrix tension by fibroblasts can even induce a phenotypic reversion of breast carcinoma cells. These data offer a basis to develop new strategies for the normalization of the tumor stroma as an innovative target in cancer therapy.

Activated coagulation factors in human malignant effusions and their contribution to cancer cell metastasis and therapy.

We have shown that the thrombin G-protein coupled receptors (GPCR) designated as protease-activated receptors (PAR-1) are expressed in primary cancer cells isolated from peritoneal and pleural malignant effusions. Here, our main goal was to evaluate several coagulation and thrombin activation effectors and markers in a series of 136 malignant effusions from cancer patients with gastrointestinal, lung and mammary carcinomas. All these patients present a highly activated coagulation system in blood and their malignant effusions, as indicated by high levels of prothrombin F1.2 fragments and D-dimers. Notably, we detected in the effusions all the coagulation factors of the tissue factor pathway inducing thrombin activation, namely factors VII, V, X and II, as well as high VEGF levels and IGF-II in mature and precursor forms. Fibrin clot formation also correlated with higher levels of free ionized calcium (iCa), suggesting that iCa and its binding protein albumin are regulatory factors for fibrinogenesis in effusions. Consequently, thrombin, VEGF and IGFII appear to converge in the promotion of survival and invasivity of the metastatic cancer cells from blood to the malignant effusions. Thus, we add new insights on the interconnections between blood coagulation disorders in cancer patients and thrombin activation in malignant effusions, including their functional interaction with PAR in metastatic cancer cells. Based on these data we propose to counteract the metastatic cascades by targeted invalidation of key effectors of the coagulation system. Therefore, potential therapeutic approaches include the application of thrombin protease inhibitors, VEGF-blocking antibodies, and drugs targeting the VEGF and thrombin signaling pathways, such as tyrosine kinase or GPCR inhibitors.