FHIT (fragile histidine triad) cleaves adenosine 5' PPP 5' A to yield AMP and ADP. 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. In normal cells, FHIT may act as a tumor suppressor. FHIT physically associates with ubiquitin conjugating enzyme 9.