LOH for all or part of a chromosomal arm in a tumor is a characteristic trait of tumor suppressor gene inactivation and a good predictor of the presence of a tumor suppressor gene (14—21)

Mitotic recombination or nondysjunction are common mechanisms for tumor-specific loss of constitutional heterozygosity (LOH) and tumor suppressor allelic inactivation and can be useful in localizing new putative tumor suppressor genes. In osteosarcoma, the highest frequencies of LOll have been reported for chromosomes 3q, 13q, lip, and lSq. The high incidenceof LOll on chromosome3q suggeststhe presenceof a novel tumor suppressor gene. To localize this putative tumor suppressor gene, we have used polymorphicmarkerson chromosome3q to define the minimal region in which mitotic recombination or deletion results in LOll, which should contain the tumor suppressor gene. This putative tumorsuppressorhasbeenlocalizedto a regionbetween3q26.2-3q26.3of less than I cM between the polymorphic lcd D3S1212 and D3S1246.