Understanding of the signaling pathways that govern tumor formation and progression is confronted with the complexity, balance and cross-talk of pro- and anti-oncogenic signaling pathways. The major aim of our team is to unravel signaling pathways involved in the positive (oncogenes) or negative regulation (tumor suppressor genes) of tumor formation and progression (invasion & metastasis) and identify novel biomarkers and therapeutic targets. Our studies initially focused on breast cancer but are, dependent on recent observations, also extended to ovarian and lung cancer. Breast cancer is the most common invasive cancer in women and metastatic spread is the main cause of treatment failure and mortality. In this cancer, we are interested in the signaling pathways controlled by the Syk protein tyrosine kinase (P. Coopman) and the PTPN13 protein tyrosine phosphatase (G. Freiss) for which we have established for the first time their negative effect on the formation and invasion of mammary tumors (tumor suppressor role). Our team and others have found a positive correlation between decreased expression and increased metastatic capacity, as well as decreased survival in breast cancer patients; findings that were corroborated in a growing number of others carcinomas. Among these carcinomas, our team is interested in lung cancer, which is the leading cause of cancer deaths in the world. Our research focuses on the KRAS and the EGFR receptor oncogenes (J. Solassol), known to have a positive effect on the development, progression or chemoresistance of lung cancers, and possible connections with the pathways controlled by Syk and PTPN13.