FHIT Loss Research Articles

Early Loss of Fhit in the Respiratory Tract of Rodents Exposed to Environmental Cigarette Smoke

The Fhit gene, encompassing the most active common human chromosomal fragile region, FRA3B, has been shown to act as a tumor suppressor. Several studies have shown significant Fhit alterations or Fhit protein loss in lung cancers from smokers compared with lung cancers from nonsmokers. To evaluate the role of Fhit under controlled experimental conditions, we exposed rodents to environmental cigarette smoke (ECS) and evaluated Fhit expression or Fhit protein in the respiratory tract. After 14 days of exposure to ECS, loss of Fhit protein in the bronchial/bronchiolar epithelium affected half of the tested B6-129(F(1)) mice, either wild type or Fhit(+/-). After 28 days, it affected the vast majority of the tested SKH-1 hairless mice and of A/J mice and all (UL53-3 x A/J)F(1) mice, either wild type or P53(+/-). In Sprague-Dawley rats, exposure to ECS for up to 30 days caused a time-dependent loss of Fhit in pulmonary alveolar macrophages. Moreover, ECS down-regulated Fhit expression and significantly decreased Fhit protein in the rat bronchial epithelium. The oral administration of N-acetylcysteine attenuated the ECS-related loss of Fhit, whereas oltipraz, 5,6-benzoflavone, phenethyl isothiocyanate, and indole 3-carbinol, and their combinations had no significant effect. Parallel studies evaluated a variety of molecular, biochemical, and cytogenetic alterations in the respiratory tract of the same animals. In conclusion, there is unequivocal evidence that Fhit is an early, critical target in smoke-related lung carcinogenesis in rodents, and that certain chemopreventive agents can attenuate the occurrence of this gene alteration.

Loss of Fhit expression is associated with poorer survival in gastric cancer but is not an independent prognostic marker

Several studies have reported conflicting results regarding correlations of the loss of Fhit expression with clinicopathological parameters in gastric cancer. We investigated the immunohistochemical expression of Fhit in 362 cases of sporadic advanced gastric adenocarcinoma. The series included 64 cases with microsatellite instability associated with defective mismatch repair genes. Fhit expression resulted absent in 72% of the tumors analyzed. Absence of Fhit expression was more frequent in cases with diffuse and mixed histotype compared to the intestinal histotype (P=0.009). Absence of Fhit expression also correlated with tumor stage (P<0.001), lymph node involvement (P<0.001), presence of distant metastasis (P=0.033), and increasing histological grade (P=0.005). Retained Fhit expression also correlated with microsatellite instability as 61% of instable tumors had lost Fhit expression compared to 74% of microsatellite stable cancers (P=0.050). While loss of Fhit correlates with poorer survival in univariate analysis, it is not an independent prognostic factor in multivariate analysis and is thus not of clinical utility.

Differential protein expression between esophageal squamous cell carcinoma and dysplasia, and prognostic significance of protein markers

The aim of the current study was to evaluate the protein expression involved in the progression from dysplasia to invasive esophageal squamous cell carcinomas and to analyze the prognostic value of markers. Immunohistochemistry was performed for cell cycle regulators [p53, p21, p27, p16, cyclin D1, Rb], apoptosis-related proteins [Fas, Fas-L, FADD, TRAIL, DR4, DR5, caspase-8, caspase-3, bcl-2, Bax], tumor suppressor proteins [ β-catenin, E-cadherin, FHIT, Smad 4, VHL, PTEN, KAI-1], and oncoproteins [c-myc, COX-2, EGFR]. Caspase-3, TRAIL, Fas-L, Fas, Smad 4, VHL, E-cadherin, and EGFR revealed significant differences between dysplasia and their corresponding invasive cancer portion in 25 cases. In a total of 118 cases of invasive cancer, proteins with frequent (⩾60% of the cases) alterations were p53 (overexpression in 64% of SCCs), p27 (loss in 91%), p16 (loss in 81%), and FHIT (loss in 75%). Early clinical stage and bcl-2 immunopositivity were related to the survival rate of patients. In conclusion, caspase-3, TRAIL, Fas-L, Fas, Smad 4, VHL, E-cadherin, and EGFR may be involved in the progression from dysplasia to invasive esophageal SCCs. Clinical stage and bcl-2 are independent prognostic factors throughout the multivariate analysis.

Cancer and the FRA3B/FHIT fragile locus: it's a HIT.

The FHIT gene encompassing the most active common human chromosomal fragile region, FRA3B, was discovered in 1996 and proposed as a tumour suppressor gene for important human cancers. Seven years and more than 350 reports later, early questions concerning its tumour suppressor role have been answered. Recent studies on the role of Fhit loss in major types of human cancers report association with high proliferative and low apoptotic indices, node positivity, loss of mismatch repair protein, likelihood of progression and reduced survival.

Microsatellite Instability Is Often Observed in Esophageal Carcinoma Patients with Allelic Loss in the FHIT/FRA3B Locus

We have previously reported a significant correlation between the progression of colorectal carcinoma and the loss of Fhit and Msh2 expression. This observation led us to investigate the effect of an allelic loss of the FHIT gene on esophageal cancer when coupled with a deficient mismatch repair system. In this study, 8 of 42 patients with esophageal cancer had microsatellite instability (MSI), and 29 cases demonstrated allelic loss (loss of heterozygosity or homozygous deletion) at the FHIT/FRA3B locus. All 8 MSI-positive cases showed allelic loss, while 13 of 34 MSI-negative cases retained both alleles, and a significant correlation was found between the incidence of MSI and allelic loss (p < 0.05). On the other hand, only 1 of the 8 MSI-positive patients exhibited neither Msh2 nor Fhit protein expression in both normal and carcinoma epithelial tissues, but neither a relationship between Msh2 expression and Fhit expression nor with the incidence of MSI was noted. This result indicated that the disruption of the mismatch repair system of Msh2 does not mainly lead to allelic loss of the FHIT/FRA3B locus as well as MSI in esophageal cancer. We concluded that MSI is significantly related to the allelic loss in the FHIT/FRA3B region, but Msh2 might be unrelated to the progression or oncogenic process in esophageal cancer.

Loss of FHIT Expression in Non-Small Cell Lung Cancer: The Clinical Significance and Effects on Apoptosis and Cell Proliferation Cycle

Background :3 p deletion has been shown to be the most frequently occurring change in lung cancers, suggesting the presence of a tumor suppressor gene in this region. Recent attention has focused on a candidate 3p14.2 tumor suppressor gene, FHIT. Therefore, the association of the expression of FHIT, with apoptosis, cell proliferation cycle and the clinicopathological features, including survival, were investigated. Materials and methods : 83 patients with non-small cell lung cancer, who underwent curative operation, between Jan. 1996 and Aug. 2000, at the Wonkwang university hospital, were analyzed. The expression of the FHITwas identified by immunohistochemical staining, and rate of apoptosis and cell proliferation cycle by flow cytometry. Results : 43% (36/83) of patients exhibited no FHIT expression. The rates of FHIT loss were 52% (28/54), 22% (5/23), 50% (3/6); 30% (11/37), 48% (16/33), 69% (9/13); 54% (30/56) and 22% (6/27), in squamous cell cancers, adenocarcinomas, large cell cancers, TNM stages Ⅰ, Ⅱ and Ⅲ, smokers and non-smokers, respectively. All the differences in FHIT loss rates, according to the histopathology, TNM stages and smoking habits, were statistically significant. The median survival time and 2-year survival

Homozygous mutations in the Fhit gene results in resistance to ionizing radiation and inhibition of apoptosis

Purpose: The Fhit gene was identified because it represents the most active constitutive chromosome fragile site and has functions often associated with a tumor suppressor gene. Mutations in the Fhit locus have been identified in many cancer-derived cell lines, primary human tumors including lung, head and neck, colon, breast, and esophagus, and are associated with tobacco-induced lung cancers. In this study, we examined the cellular response of mouse epithelial cells with complete loss of Fhit to therapeutic doses of ionizing radiation and the prognostic importance of Fhit protein in early stage breast cancer patients treated with breast conserving therapy. Materials and Methods: Mouse epithelial cell lines containing either homozygous mutant Fhit −/− or wild-type Fhit +/+ were derived from mice (C57BL/6J X 129/SvJ) with either wild-type or inactivated Fhit gene. Clonogenic cell survival assays were carried out on subconfluent cells in logarithmic growth using a 137Cs irradiator and survival curves were plotted as the log of the surviving cells versus dose and corrected for cloning efficiency. Apoptosis following ionizing radiation was determined by flow cytometry using the Annexin-V FITC kit and DAPI staining. Paraffin-embedded breast tumor blocks were obtained from 42 women with local breast tumor recurrence and 42 matched breast cancer patients without local cancer relapse treated with breast conserving therapy and stained with a 1:4000 dilution of polyclonal antibody to the Fhit protein and scored based on both intensity and distribution of Fhit staining within the invasive breast cancer component. Results: Treatment of Fhit −/− mouse epithelial cells with single fraction doses of ionizing radiation including 2, 4, 6, and 10 Gy result in 4-6 fold increase in cellular survival compared with isogenic parental cells from Fhit +/+ mice. Fhit −/− epithelial cells displayed 3-5 fold lower levels of apoptosis in response to both low and high doses of ionizing radiation compared to parental mammalian cells expressing wild-type Fhit protein. Finally, we demonstrated that breast tumors from breast cancer patients with local breast tumor recurrences following breast conserving therapy more often lacked immunhistochemical detection of Fhit protein compared to tumors from breast cancer patients without local breast cancer recurrence (p=0.02). Interestingly, the adjacent benign regions of these sections contained similar levels of Fhit protein expression suggesting that a somatic alteration is critical in the clinical resistance to ionizing radiation observed in these patients. Apoptotic pathways regulating the aberrant response to DNA damage-induced apoptosis in Fhit knock-out cells are currently being studied. Conclusion: Mouse epithelial cells containing homozygous Fhit mutations are resistant to single fraction low and high dose ionizing radiation with decreased levels of radiation-induced apoptotic cell death. Breast tumors from women with local breast cancer recurrence following breast conserving therapy have low levels of Fhit protein. These findings may have important biologic and treatment implications including those for cancer patients with tumors having mutations in Fhit and suggest that treatment with ionizing radiation in these patients may not result in optimal responses.

Fhit loss in familial breast cancer: is loss of DNA repair function linked to alterations at chromosome fragile sites?

The FHIT gene at 3p14.2 encompasses the common fragile site, FRA3B, and is involved in frequent chromosome rearrangements in human cancers. Fhit protein expression is reduced or lost in the majority of esophageal, lung, gastric, cervical, pancreatic, kidney and bladder cancers, and a large fraction of other cancers. Fhit expression in sporadic breast cancers has been studied by several groups, and reported to show alteration in expression of Fhit in 30-50%. Because familial breast cancers were reported to show a higher frequency of LOH at 3p14.2 than sporadic breast cancers, we were interested in whether common fragile regions might be targets for repair by the Brca1 and Brca2 proteins, and might thus be a downstream target in BRCA1- and BRCA2-induced familial breast tumors. We studied a panel of Brca2-deficient breast tumors and showed that only 18% expressed Fhit strongly, compared with 48% of sporadic tumors (P = 0.002). Very recently we completed a similar study of BRCA1 familial tumors, and observed that only 9% of these tumors showed strong expression versus more than 40% of sporadic breast tumors (P <0.001, odds ratio 0.09). We conclude that loss of BRCA1 and BRCA2 functions affect stability of the FHIT/FRA3B locus and possibly other fragile loci.

FHIT gene therapy prevents tumor development in Fhit-deficient mice.

The tumor suppressor gene FHIT spans a common fragile site and is highly susceptible to environmental carcinogens. FHIT inactivation and loss of expression is found in a large fraction of premaligant and malignant lesions. In this study, we were able to inhibit tumor development by oral gene transfer, using adenoviral or adenoassociated viral vectors expressing the human FHIT gene, in heterozygous Fhit(+/-) knockout mice, that are prone to tumor development after carcinogen exposure. We therefore suggest that FHIT gene therapy could be a novel clinical approach not only in treatment of early stages of cancer, but also in prevention of human cancer.

Di-, tri- and tetra-5'-O-phosphorothioadenosyl substituted polyols as inhibitors of Fhit: Importance of the α-β bridging oxygen and β phosphorus replacement

BackgroundThe human FHIT gene is inactivated early in the development of many human cancers and loss of Fhit in mouse predisposes to cancer while reintroduction of FHIT suppresses tumor formation via induction of apoptosis. Fhit protein, a diadenosine polyphosphate hydrolase, does not require hydrolase activity to function in tumor suppression and may signal for apoptosis as an enzyme-substrate complex. Thus, high affinity nonhydrolyzable substrate analogs may either promote or antagonize Fhit function, depending on their features, in Fhit + cells. Previously synthesized analogs with phosphorothioadenosyl substitutions and "supercharged" branches do not bind better than natural substrates and thus have limited potential as cellular probes.ResultsHere we link adenosine 5'-O-phosphates and phosphorothioates to short-chain polyols to generate a series of substrate analogs. We obtain structure-activity data in the form of in vitro Fhit inhibition for four types of analog substitutions and describe two compounds, inhibitory constants for which are 65 and 75-fold lower than natural substrates.ConclusionsThe best Fhit inhibitors obtained to date separate two or more 5'-O-phosphoromonothioadenosyl moieties with as many bond lengths as in AppppA, maintain oxygen at the location of the α-β bridging oxygen, and replace carbon for the β phosphorus.

Fhitness and cancer in the mouse

The human FHIT gene is located at 3p14.2, a position on the short arm of chromosome 3 that includes the most fragile site in the human genome and spans a t(3;8) translocation that predisposes to early onset, clear cell renal carcinoma. FHIT deletions are extremely common in human cancers, especially those that arise from lung and stomach epithelia exposed to environmental carcinogens. Nonetheless, because FHIT spans a fragile site and tumors usually lose FHIT by deletion rather than point mutation, some researchers have argued that FHIT deletions are not a cause of cancer but rather a consequence of genome instability. Although the early kinetics of FHIT inactivation in lung carcinogenesis, and the fact that re-expression of Fhit protein induces apoptosis in parallel with suppressing tumor formation, support assignment of FHIT as a tumor suppressor, many cancer geneticists consider the knockout mouse to be the ultimate test.If FHIT inactivation in humans is merely a consequence of genome instability, then inactivation of Fhit in the mouse would not be expected to effect carcinogenesis. On the other hand, if FHIT loss in humans does contribute to cell transformation, then murine Fhit− animals might be expected to develop tumors, potentially in the same organs in which human FHIT− tumors appear. This was precisely the result obtained by Fong et al.1xMuir–Torre-like syndrome in Fhit-deficient mice. Fong, L.Y.Y. et al. Proc. Natl. Acad. Sci. U. S. A. 2000; 97: 4742–4747Crossref | PubMed | Scopus (162)See all References1, all the more striking because this was after genetically inactivating only one Fhit allele in the mouse. Because the murine Fhit locus, like its syntenic human counterpart, is fragile, mice that were heterozygous for inactivation of Fhit developed stomach and sebaceous tumors when given N-nitrosomethylbenzylamine intragastrically. Ten weeks after treatment, 10 of 12 heterozygous mice had tumors of the forestomach, and 7 of 12 had sebaceous tumors; these tumors lacked Fhit protein. Among eight identically treated wild-type mice, one developed a tumor in the forestomach and none developed a sebaceous tumor. The combination of visceral and sebaceous tumors in Fhit heterozygous mice struck these researchers as similar to human Muir–Torre syndrome (MTS), a variant of hereditary nonpolyposis colorectal cancer, and they showed that some human MTS tumors are Fhit.Whereas MTS usually arises from inherited defects in mismatch repair genes, the full complement of genetic changes in MTS tumors is not known. The phenotype of Fhit heterozygous mice not only demonstrates that loss of Fhit predisposes to carcinogenesis, but also suggests that an intact mismatch repair system might either protect the FHIT locus or maintain Fhit expression in humans.

Fhit expression in gastric adenocarcinoma

The FHIT gene is inactivated by deletion in a large fraction of human tumors, including gastric carcinomas, and the Fhit protein has been proposed to act as a tumor suppressor in multiple tumor types. A large fraction of gastric adenocarcinomas have lost expression of the candidate tumor suppressor protein, Fhit, whereas normal gastric epithelial cells are strongly positive and Fhit loss has been found to correlate with alterations of the FHIT locus. Because the majority of gastric tumors in the current study were found to be entirely negative for Fhit protein, it is possible that alteration of the carcinogen-susceptible fragile region within the FHIT gene is an early event in gastric carcinoma, as it is in lung carcinoma. To determine whether the absence of Fhit protein correlates with expression of tumor markers or with clinical parameters, such as grade, stage, and survival time, the authors assessed Fhit expression using immunohistochemistry in a well characterized set of 55 gastric adenocarcinomas resected over several years, with longitudinal follow-up of patients for outcome. In this set of 55 gastric cancers, the absence of Fhit protein correlated with higher tumor stage (P = 0.003) and higher histologic grade (P = 0.007). In addition, patients whose tumors had lost expression of Fhit died of disease significantly earlier than those with Fhit positive tumors (P = 0.017). The absence of Fhit expression did not correlate with the expression of any tumor markers. Larger studies will be required to elucidate further the relation between tumor stage, grade, and Fhit loss and to determine whether inclusion of Fhit antiserum in immunophenotyping of gastric adenocarcinomas will be a useful indicator of post-diagnosis prognosis.

Expression of FHIT in primary cultures of human epithelial ovarian tumors and malignant ovarian ascites.

Abnormal FHIT gene expression has been reported in a variety of epithelial tumors shown to harbor deletions of chromosome 3p14, the chromosomal assignment of this gene. Recently, we described loss of heterozygosity of 3p in a subset of epithelial ovarian cancers. To investigate a potential role of the FHIT gene in ovarian cancer, we examined primary cell cultures derived from normal ovarian surface epithelium, ovarian tumors, and the cellular fraction of malignant ascites to determine the expression of FHIT by using reverse transcription-polymerase chain reaction. Included in this analysis were four spontaneously immortalized cell lines: three derived from malignant epithelial ovarian tumors (TOV21G, TOV112D, and TOV81D) and one from malignant ovarian ascites (OV90). OV90 was previously shown to harbor a deletion of the whole p arm of chromosome 3. The FHIT transcript was not detectable in two of 11 primary cultures derived from normal ovarian surface epithelium or in a primary culture derived from malignant ovarian ascites, whereas the remaining samples (34 malignant, eight borderline, and three benign specimens), exhibited identical expression patterns. In each case, this pattern was consistent with the co-expression of a normal FHIT transcript and a smaller transcript. DNA sequencing revealed that the abnormal-sized message lacked exons 4-7 (inclusive), which were deleted at their exact intron-exon splice sites. The aberrant-sized transcript was detectable by Northern blot analysis. There was no concordance between FHIT expression and loss of heterozygosity at the FHIT locus. Northern blot analysis also revealed that FHIT was differentially expressed, and the spontaneously immortalized cell lines TOV21G and TOV112D showed the highest level of expression. Because the same reverse transcription-polymerase chain reaction expression pattern was observed in both normal and tumor-derived primary cell cultures, these results argue against a significant role for FHIT in epithelial ovarian tumorigenesis.