Loss of Fragile Histidine Triad Gene Expression in Advanced Lung Cancer Is Consequent to Allelic Loss at 3p14 Locus and Promoter Methylation

Integrated analysis of FHIT gene alterations in cancer

The Fragile Histidine Triad Diadenosine Triphosphatase (FHIT) gene is located in the Common Fragile Site FRA3B and encodes an enzyme that hydrolyzes the dinucleotide Ap3A. Although FHIT loss is one of the most frequent copy number alterations in cancer, its relevance for cancer initiation and progression remains unclear. FHIT is frequently lost in cancers from the digestive tract, which is compatible with being a cancer driver event in these tissues. However, FHIT loss could also be a passenger event due to the inherent fragility of the FRA3B locus. Moreover, the physiological relevance of FHIT enzymatic activity and the levels of Ap3A is largely unclear. We have conducted here a systematic pan-cancer analysis of FHIT status in connection with other mutations and phenotypic alterations, and we have critically discussed our findings in connection with the literature to provide an overall view of FHIT implications in cancer.

Potential Role of the Fragile Histidine Triad in Cancer Evo-Dev

Cancer development follows an evolutionary pattern of "mutation-selection-adaptation" detailed by Cancer Evolution and Development (Cancer Evo-Dev), a theory that represents a process of accumulating somatic mutations due to the imbalance between the mutation-promoting force and the mutation-repairing force and retro-differentiation of the mutant cells to cancer initiation cells in a chronic inflammatory microenvironment. The fragile histidine triad (FHIT) gene is a tumor suppressor gene whose expression is often reduced or inactivated in precancerous lesions during chronic inflammation or virus-induced replicative stress. Here, we summarize evidence regarding the mechanisms by which the FHIT is inactivated in cancer, including the loss of heterozygosity and the promoter methylation, and characterizes the role of the FHIT in bridging macroevolution and microevolution and in facilitating retro-differentiation during cancer evolution and development. It is suggested that decreased FHIT expression is involved in several critical steps of Cancer Evo-Dev. Future research needs to focus on the role and mechanisms of the FHIT in promoting the transformation of pre-cancerous lesions into cancer.

Detection of FHIT and p16 mRNA deletion in biopsy specimens obtained by bronchoscopy for the diagnosis of lung cancer

The purpose of this study was to investigate the diagnostic value of the deletion of fragile histidine triad (FHIT) and p16INK4a (p16) mRNA in biopsies obtained by bronchoscopy. Biopsies were analyzed using RT-PCR in 52 patients with lung cancer and 19 patients with benign lung disease. The results showed that the detection rates of FHIT and p16 gene transcript deletion were significantly higher in lung cancer patients than in patients with benign lung disease (65.4% versus 10.5%, p=0.001 and 59.6% versus 5.3%, p<0.001, respectively). The sensitivities for detecting FHIT and p16 transcript deletion in biopsies were 65.4% and 59.6% (combined 80.8%), respectively, which were markedly better than those of histology and cytology (42.3% and 34.6%, respectively; combined 57.7%). In 22 lung cancer patients with negative histology and cytology at initial bronchoscopy, FHIT and p16 mRNA loss was detected in 40.9% (9/22) and 36.4% (8/22) cases, respectively. FHIT mRNA loss was associated with smoking status in lung cancer patients. In conclusion, deletion of FHIT and p16 mRNA can be identified in biopsies obtained during bronchoscopic procedures. FHIT and p16 mRNA deletion can be used as biomarkers in the clinical diagnosis of lung cancer and may serve as adjuncts to histology and cytology in lung cancer diagnosis.

Molecular diagnosis and prognostic significance of lymph node micrometastasis in patients with histologically node-negative non-small cell lung cancer

Lymph node metastasis is a major prognostic factor in resected non-small cell lung cancer (NSCLC). However, 30-40 % rate of recurrence after performing complete resection in node-negative patients suggests that their nodal staging is suboptimal. We aimed to evaluate the molecular diagnosis and prognostic significance of lymph node micrometastasis in patients with node-negative NSCLC. Primary tumor samples from 62 patients with resected stage I-IIB NSCLC were screened for fragile histidine triad (FHIT) and CDKN2A mRNA deletion using reverse transcriptase polymerase chain reaction (RT-PCR). The molecular alternations were found in tumors of 49 patients. A total of 269 lymph nodes from these 49 NSCLC patients with FHIT or/and CDKN2A deletion tumors were examined. Fifteen positive-control nodes and ten negative-control nodes were also analyzed for FHIT and CDKN2A mRNA deletion. Thirty-nine (22 %) and 22 (18 %) lymph nodes from the 49 patients with FHIT and CDKN2A mRNA deletion in primary tumor had FHIT and CDKN2A mRNA deletion, respectively. The types of FHIT and CDKN2A mRNA deletion in lymph nodes were identical with those in their primary tumors. By combination of two markers, 16 patients (32.7 %) were found to have nodal micrometastasis. Survival analysis showed that patients with nodal micrometastasis had reduced disease-free survival (P = 0.001) and overall survival (P = 0.002) rates. Multivariate analysis demonstrated that nodal micrometastasis was an independent predictor for worse prognosis. Thus, the detection of lymph node micrometastasis by FHIT and CDKN2A mRNA deletion RT-PCR will be helpful to predict the recurrence and prognosis of patients with completely resected stage I-IIB NSCLC.

Down-regulation of FHIT inhibits apoptosis of colorectal cancer: Mechanism and clinical implication

Fragile histidine triad (FHIT) gene, a candidate tumor suppressor gene located at 3p14.2, has been shown to be involved in carcinogenesis of many human tissues, including digestive tract tissues. However, the expression and role of FHIT in the initiation and the development of the colorectal cancer (CRC) are poorly understood. In our present study, we have demonstrated that the FHIT gene exhibits significantly decreased expression in human CRC compared to colorectal adenoma and normal colorectal tissue by tissue microarray (TMA). The positive of FHIT gene expression in normal colorectal tissue, adenoma and adenocarcinoma were 93.75%, 68.75% and 46.25%, respectively. We showed that decreased FHIT expression was significantly correlated with the progression of colorectal carcinoma (P<0.05) as well as differentiation and lymph node metastasis (P<0.05). Two somatic mutations in the FHIT gene were also detected in human CRC. The presence of these mutations correlated significantly with decreased FHIT expression in the human CRC. In addition, we identified decreased FHIT expression resulting in apoptosis inhibition and decreasing apoptosis associated with abnormal levels of some pro- and anti-apoptotic proteins (Bax, Bcl-2 and Survivin) by TUNEL and TMA. Our results demonstrated that the mutation in the FHIT gene significantly reduced FHIT expression in human CRC. Both TUNEL and TMA experiments demonstrated significantly inhibited apoptosis by down-regulation of Bax and up-regulation of Survivin and Bcl-2. Collectively, these studies identify the mechanism by which an important tumor suppressor gene, FHIT, inactivated specifically in human CRC, and contributes to our understanding of the mechanism of colorectal carcinogenesis.

Fragile Histidine Triad Expression in Oral Squamous Cell Carcinoma and Precursor Lesions

PURPOSE

Fragile histidine triad (FHIT) expression in precursor oral lesions (POL) and oral squamous cell carcinomas (OSCC) was studied with regard to (a) the frequency of loss of FHIT expression, (b) whether loss of FHIT expression correlates with degree of dysplasia in POLs, (c) whether FHIT loss predicts high-risk POLs that are more likely to transform, and (d) whether FHIT loss in OSCCs correlates with survival.

EXPERIMENTAL DESIGN

Ninety-four POLs and 86 OSCCs were immunostained for FHIT. Survival analysis was done for cases with validated clinical outcomes.

RESULTS

By optimizing the immunostaining protocol, we found that FHIT is expressed in a distinctive strong nuclear and weak cytoplasmic pattern in oral tissues. Loss of FHIT expression was found in 42 of 94 (45%) POLs and in 66 of 86 (77%) OSCCs. We observed a statistically significant positive correlation between frequency of FHIT loss and increasing grade of dysplasia (chi2=13.8; degrees of freedom=4; P=0.008). Loss of FHIT expression in POLs that progressed to malignancy was more frequent than in those that did not [17 of 25 (68%) versus 12 of 29 (41.4%), respectively]. This difference was statistically significant (chi2=3.8; degrees of freedom=1; P=0.046). In OSCCs, loss of FHIT staining indicated a worse prognosis (survival rate, 36.2%) than when positive FHIT staining was observed (survival rate, 50%), but the difference was not statistically significant (P=0.546, Kaplan-Meier, log-rank).

CONCLUSIONS

FHIT seems to localize to both nuclear and cytoplasmic domains. FHIT inactivation occurs early in oral carcinogenesis and may be useful molecular marker for progressive dysplastic oral lesions.

Coexpression of Fragile Histidine Triad and c-kit Is Relevant for Prediction of Survival in Patients with Small Cell Lung Cancer

BACKGROUND

In a retrospective analysis of 195 patients with small cell lung cancer (SCLC), we examined the prognostic value of a coexpression of fragile histidine triad (FHIT) protein and c-kit on patient's survival.

METHODS

As assessed by immunohistochemistry using formalin-fixed, paraffin-embedded tissue sections, tumors of 195 patients with SCLC were evaluated for FHIT and c-kit coexpression.

RESULTS

Coexpression of FHIT and c-kit was observed in 53.3%; a positive expression of either FHIT or c-kit was found in 40.5%. Complete lack of FHIT and c-kit (6.2%) was associated with a significantly shorter survival time for the patients with a mean of 122 +/- 45 days compared with 468 +/- 89 days for patients with lung cancer coexpressing FHIT and c-kit (P = 0.0011). The proportion of FHIT- and c-kit-positive cells within a tumor was also related to survival time. Patients with tumors with a proportion between 0% to 25% of FHIT- and c-kit-positive cells had the worst survival of 157 +/- 34 days compared with 496 +/- 95 days for patients showing >25% FHIT- and c-kit-positive cells (P = 0.0002). Further, variables associated with shorter survival times were low performance status, elevated lactate dehydrogenase level, and advanced tumor stage according to tumor-node-metastasis classification. Multivariate analysis using Cox regression model, including 11 variables, confirmed the prognostic significance of a combined expression of FHIT and c-kit next to tumor stage, performance status, and lactate dehydrogenase level.

CONCLUSIONS

Differential FHIT and c-kit expression was of prognostic relevance for survival in patients with SCLC and therefore provide useful variables for therapeutic decisions.