Inactivation of tumour suppressor genes (TSG) controlling aberrant cell proliferation is a hallmark of tumorigenesis and characterization of new TSGs is essential to uncover novel cancer pathways, which will ultimately lead to new therapeutic strategies. The human chromosomal region 3p21.3 has been described as a region containing many TSGs and is frequently deleted in kidney, lung, breast and cervical tumours. One TSG candidate located in this region is the PTPN23 gene encoding the poorly characterized HD-PTP protein. Our previous work suggests that HD-PTP inactivation leads to lung tumour development in the mouse. We are planning to use cellular and mouse models to investigate HD-PTP functions in term of tumour growth. Results that we will obtain could lead to new clinical perspectives in the development of cancer therapeutics.