NIH -- By activating a cancer suppressor gene, a small molecule called nutlin-3a can block cancer cell division, according to researchers at the National Cancer Institute (NCI), part of the National Institutes of Health. This activation of the p53 gene leads to cellular senescence, a process by which cells lose their ability to grow and divide. An opportunity for new genetic mutations occurs each time a cell divides, so limiting the number of cell divisions in a cancer cell inhibits tumor progression. This study is published in the May 1, 2008, issue of Cancer Research.