The protein encoded by FHIT (Fragile Histidine Triad) gene is a P1-P3-bis(5'-adenosyl) triphosphate hydrolase involved in purine metabolism. The FHIT gene encompasses the common fragile site FRA3B on chromosome 3, where carcinogen-induced damage can lead to translocations and aberrant transcripts. In fact, aberrant transcripts from this gene have been found in about half of all esophageal, stomach, and colon carcinomas. The encoded protein is also a tumor suppressor, as loss of its activity results in replication stress and DNA damage. FHIT protein is a tumor suppressor with reduced or no expression in many types of cancer. FHIT expression is more frequently lost in cancers of individuals with familial mutations causing deficiency in DNA repair genes such as BRCA1 and BRCA2 and MSH2.