Replacement of Fhit in cancer cells suppresses tumorigenicity

Abstract

The candidate tumor suppressor gene, FHIT, encompasses the common human chromosomal fragile site at 3p14.2, the hereditary renal cancer translocation breakpoint, and cancer cell homozygous deletions. Fhit hydrolyzes dinucleotide 5,5ٟ-P 1 ,P 3 -triphosphate in vitro and mutation of a central histidine abolishes hydrolase activity. To study Fhit function, wild-type and mutant FHIT genes were transfected into cancer cell lines that lacked endogenous Fhit. No consistent effect of exogenous Fhit on growth in culture was observed, but Fhit and hydrolase ''dead'' Fhit mutant proteins suppressed tumorigenicity in nude mice, indicating that 5,5ٟ-P 1 ,P 3 -triphosphate hydrolysis is not required for tumor suppression.The structure and expression of the FHIT gene encompassing the FRA3B common fragile site frequently are altered in primary or cultured esophageal, head and neck, lung, gastric, breast, and cervical carcinomas (1-8). Structural alterations tend to be because of deletion within both FHIT alleles, resulting in loss of exons and concomitant absence of full-length FHIT transcript and protein (ref. 6; for review, ref. 9). It has been argued that the FHIT gene may be altered in cancer cells simply because it encompasses the fragile region and is likely to be very susceptible to breakage (7). We agree that the locus is highly susceptible to carcinogen damage, explaining why deletion is much more frequent than point mutation in the gene, but we argue that loss of Fhit function provides a selective advantage for the tumor cell; otherwise, frequent expansion of the deleted FHIT clones in tumors and tumor-derived cell lines would be difficult to explain.Fhit-related proteins have been found in mammals and yeasts (1, 10, 11) and constitute a branch of the histidine triad (HIT) superfamily (12). The Fhit branch includes the Schizosaccharomyces pombe diadenosine tetraphosphate hydrolase [dinucleoside 5Ј,5ٞ-P 1 ,P 4 -tetraphosphate (Ap 4 A) hydrolase] (10) to which Fhit is similar. Barnes et al. (13) have shown that Fhit behaves in vitro as a typical dinucleoside 5Ј,5ٞ-P 1 ,P 3 -triphosphate (Ap 3 A) hydrolase (EC 3.6.1.29); site-directed mutagenesis of FHIT demonstrated that the conserved histidines are required for full activity, and the central histidine of the triad is essential for Ap 3 A hydrolase activity.To investigate mechanisms for a selective growth advantage of Fhit negative tumors, we have prepared vectors for expression of Fhit in cancer-derived cells and have examined the phenotypes of the Fhit-expressing clones relative to the Fhit negative parental cells. To determine if the in vitro enzymatic activity was associated with a role in tumor suppression, the hydrolase ''dead'' mutant gene, FHITH96N, with the central histidine codon of the HIT changed to an asparagine codon, also was expressed in Fhit negative cancer cells. MATERIALS AND METHODSCells. The MKN74 cell line (kindly provided by Eiichi Tahara, University of Hiroshima, Japan), was derived from a gastric carcinoma (14) and forms tumors rapidly ...

Genetic alterations in poorly differentiated endocrine carcinomas of the gastrointestinal tract

“…9,11,31 In addition, the status of FHIT as a candidate tumor suppressor gene in 3p14 has been well demonstrated in endocrine lung carcinomas by immunohistochemical methods 31 and by in vivo experiments. 32 Overall, the data from the current study may support the hypothesis that FHIT functions as a tumor suppressor gene in the pathogenesis of GI PDECs.…”

Roles of Fhit and p53 in Taiwanese surgically treated non-small-cell lung cancers

“…The cloning of the fragile histidine triad(FHIT) gene at 3p14.2 in 1996 (Ohta et al, 1996) and the subsequent reports demonstrated frequent allelic deletion, aberrant FHIT transcripts in primary lung cancers (Fong et al, 1997), cell lines of small cell and nonsmall cell type (Yanagisawa et al, 1996). The evidence that FHIT suppresses tumorigenicity in cancer cells (Siprashvili et al, 1997) supports the contention that FHIT is a tumour suppressor gene. This, together with the recent observation (Sozzi et al, 1997a) that there is more FHIT allelic loss in carcinomas from smokers than from nonsmokers, strengthens the case for its involvement in the multistage development of lung cancer.…”

High throughput tissue microarray analysis of FHIT expression in diffuse large cell B-cell lymphoma from Saudi Arabia

“…The exact molecular mechanism or functional pathway mediating FHIT's tumor suppressor action is still not fully understood. It is known that FHIT hydrolases diadenosine nucleotides into ADP and AMP, but since this enzymatic activity does not seem to be required for its tumor-suppressor function there must be other relevant features of the protein, 12 that is regulation of apoptosis. It has been demonstrated that restoration of FHIT expression in lung and cervical cancer cell lines resulted in efficient induction of apoptosis and suppression of tumorigenicity, and that the apoptotic mechanism seems to be FADD (Fas associated via death domain) dependent, caspase-8 mediated and independent from regulation through Bcl-2 or Bcl-xl.…”

“…7,8 FHIT is known to be inactivated in various human malignancies. [9][10][11][12][13][14][15][16][17][18][19][20] FHIT inactivation by point mutation is a rare event, [21][22][23] but significant loss or reduction of expression can be caused by other mechanisms, including loss of heterozygosity (LOH) and/or promoter hypermethylation. 24 For example, FHIT hypermethylation with consequent transcriptional inactivation has been shown in breast, lung, esophageal, cervical, prostate and bladder cancer.…”