FHIT (fragile histidine triad) is an enzyme that cleaves adenosine 5' PPP 5' A to yield AMP and ADP. FHIT gene encompasses the common fragile site FRA3B on chromosome 3. Alterations and deletions of the FHIT gene are strongly linked to the genesis and establishment of human tumors of the lung, cervix, breast, colon, stomach and pancreas.