FHIT and cancer: Numerous reports have confirmed that the FHIT gene is a preferential target of allelic deletion and that Fhit inactivation has roles in initiation, development and progression of cancers ([13] for review), and we have recently reported that Fhit protein deficiency causes reduced expression of thymidine kinase, subsequent dTTP imbalance, impaired DNA replication fork progression, and spontaneous DNA breaks that are transmitted to daughter cells, leading to genome instability [14].