Bulk SUM149PT and CD44+/CD24−/Low cancer cells were treated with the antimetabolite methotrexate (a conventional chemotherapeutic drug) or SU9516 (a small molecule inhibitor of Cdk2 activity) and cytotoxicity was quantified by analyzing the percentage of cells harboring cleaved PARP as a marker of apoptosis. This evidence concerns the gene CD44 and cancer.