During cancer progression, some genes that prevent tumor development are inactivated and are called tumor suppressors. The identification and characterization of these tumor suppressors is essential to develop new cancer therapies. This project aims to investigate a new function of a novel tumor suppressor gene: HD-PTP. Our previous work showed that inactivation of HD-PTP lead to lung tumors in mouse and that HD-PTP could be inactivated during human lung cancer. To explore the HD-PTP tumor suppressor mechanism, we inactivated HD-PTP in normal mouse cells and observed the appearance of cancer cells characteristics, suggesting that loss of HD-PTP is associated with the early steps of tumorigenesis. Therefore, the goal of this project is to characterize this new cellular function of HD-PTP and to determine how HD-PTP depletion contributes to cancer progression. Results that we will obtain could lead to new diagnostic, prognostic as well as new clinical perspectives in the development of lung cancer treatment.