Studies have demonstrated that pRb inactivation leads to elevated p16 expression in different cancer types through a reciprocal regulatory mechanism.79, 80, 81, 82, 83, 84, 85, 86, 87, 88 Patients who have HPV-related tongue tumours show improved treatment outcomes and better survival rates when their P16 expression levels are elevated compared to HPV-negative patients. This evidence concerns the gene CDKN2A and cancer.