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

Abstract

Pupose: 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 FHITexpression 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 (m 2 = 13.8; degrees of freedom = 4; P = 0.008). Loss of FHITexpression 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 (m 2 = 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: FHITseems 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.

Immunohistochemical characterization of FHIT expression in normal human tissues

“…Characterization of the pattern of human FHIT expression could contribute to our understanding of the function of this protein in normal tissues and provide a reference framework for interpretation of abnormal FHIT expression in human tumors. In contrast to previously published studies that reported exclusively cytoplasmic localization of FHIT, we showed a nuclear and cytoplasmic localization of the FHIT protein by immunohistochemical methods [12]. We, therefore, aim to perform a comprehensive immunohistochemical analysis of FHIT expression in normal human tissues and compare FHIT expression with proliferation and diff erentiation within individual organs.…”

“…For scoring, negative and low (no staining or immunoreactivity staining present in <10% of cells) staining scores and moderate (immunoreactivity in ≥10-50% of cells) and strong (immunoreactivity in >50% of cells) staining scores were combined as negative or positive, respectively, as described previously by Kujan et al [12]. The software SPSS 22.0 was used to analyze all the statistical analyses.…”

“…FHIT immunohistochemical testing was performed according to the protocol that was developed earlier by Kujan et al [12] using primary rabbit polyclonal anti-glutathione S-transferase-FHIT antibody (abcam, Cambridge, UK). Briefl y, three paraffi n-embedded, formalin-fi xed sections from each studied organ were deparaffi nized, rehydrated, and immersed in 0.5% H 2 O 2 -methanol for 5 min.…”

“…The FHIT gene can be inactivated by several mechanisms, including deletions, point mutations, methylation, loss of a whole chromosome, and genetic recombination. It was reported that the loss or decreased RNA and protein products of FHIT was found in stomach, liver, cervix, esophagus, breast, renal, pulmonary, gall bladder, colon, and oral cavity tumors, as well as leukemia [5,11,12].…”

P53 nuclear stabilization is associated with FHIT loss and younger age of onset in squamous cell carcinoma of oral tongue

“…Few studies have identified FHIT to be a predictor of poor survival in OSCC [34] in HNSCC [35]. However, these studies did not analyze the status of p53 aberrations in the tumors.…”