Phenotypic effect correlating with loss of a novel tumor suppressor gene: towards cloning by complementation

We intend to use a gene complementation approach to clone a tumor suppresso r gene on mouse chromosome 2, the loss of which contributes to myeloid leuk emia. An in vitro model system has been generated using a clonal cell line, in which tumorigenic chromosomal lesions have been selected along with mye loid differentiation. Among these lesions are deletions of chromosome 2. Co mparison of subclones with deleted vs intact chromosomes 2 has allowed the identification of a growth related phenotypic pattern which correlates with the deletion, viz the retention of a marker of immature cells, resistance to inhibition by lipopolysaccharide (LPS), even in the presence of markers of mature myeloid cells, such as resistance to killing by apoptosis-inducin g agents. The phenotype is shared by chromosome 2-deleted cell lines derive d from conventional tumors. We have begun to investigate the mechanism of t he phenotype. The LPS resistance does not correlate with lack of mRNA for C D14, a known cell surface receptor for this agent, or with failure to induc e TNF alpha or nitric oxide synthase in response to its binding. The system should allow cloning of the gene using complementation of this phenotype i n transfected cell lines.