Tumour Suppressor Gene Identification

Tumour suppressor genes are crucial for controlling cell growth and preventing cancer. When these genes are inactivated, cells can grow uncontrollably, leading to tumour formation.

Key Gene Analysis

The question asks for a tumour suppressor gene inactivated in over 50% of human tumours, specifically mentioning breast and colon carcinomas and childhood leukaemias. Let's analyze the options:

• p Rb: While a significant tumour suppressor involved in cell cycle regulation, its inactivation is not characteristic of over 50% of all human cancers broadly.
• STK 11: This gene is linked to Peutz-Jeghers syndrome and related cancers but doesn't meet the high prevalence criteria across diverse tumours.
• p 53: Often called the "guardian of the genome", the p53 protein (encoded by the TP53 gene) plays a vital role in DNA repair and apoptosis. Mutations or inactivation of p53 are extremely common, occurring in more than half of all human cancers, including breast, colon, lung, and various leukaemias. This high frequency aligns perfectly with the question's description.
• VHL: The VHL gene is a tumour suppressor, but its inactivation is primarily associated with Von Hippel-Lindau disease and specific tumour types, not the broad range and high percentage mentioned.

Based on prevalence data in human oncology, p 53 is the tumour suppressor gene most frequently inactivated across a wide spectrum of cancers.