Loss of FANCD2 and related proteins may predict malignant transformation in oral epithelial dysplasia

Abstract

Background: Predicting malignant transformation in oral epithelial dysplasia(OED) is a clinical challenge. The higher rate of malignant transformation in non-smokers supports an endogenous aetiology. Loss of FANCD2 and associated proteins could lead to genomic instability and oncogenesis. Methods: Longitudinal archival samples from 40 individuals with OED from time of diagnosis to the most recent review in 23 stable OED; or until excision of the SCC in 17 unstable OED undergoing malignant transformation. Histopathological reassessment, immunohistochemistry for FANCD2 and Western blotting for phosphorylation/monubiquitination status of ATR, CHK1, FANCD2 and FANCG were undertaken on each tissue sample. Results: Decreased expression of FANCD2 was observed in the diagnostic biopsy of OED lesions which later underwent malignant transformation. Combining the FANCD2 expression scores with histological grading more accurately predicted malignant transformation (p=0.005) than histology alone and correctly predicted malignant transformation in 10/17 initial biopsies. Significantly reduced expression of total FANCD2, pFANCD2, pATR, pCHK-1 and pFANCG were observed in unstable OED. Discussion: There is good evidence that defects in the DNA damage sensing-signalling-repair cascade are associated with malignant transformation in OED. Loss of post-translational modification in FANCD2 and related proteins, was more predictive of malignant transformation when compared to clinicopathological parameters.