Most cancer susceptibility genes are tumor suppressor genes. Tumor suppressor genes are just one type of the many genes malfunctioning in cancer. These genes, under normal circumstances, suppress cell growth. Some do so by encoding transcription factors for other genes needed to slow growth. For example, the protein product of the suppressor gene TP53 is called p53 protein. It binds directly to DNA and leads to the expression of genes that inhibit cell growth or trigger cell death. Other tumor suppressor genes code for proteins that help control the cell cycle.