MD by portfolio or published work in OMFS

Abstract

Background: The Fanconi Anaemia (FA) pathway is responsible for homologous recombination repair of DNA interstrand crosslink damage. This checkpoint in S-phase of the cell cycle is mediated by ATR (Ataxia Telangiectasia Rad-3) and BRCA-1. The role of this tumour suppressor pathway in early oncogenesis is evaluated in oral dysplasia (OED) which transformed into oral squamous cell carcinoma (OSCC) by evaluating expression of FANC-D2 protein. Methods:Forty patients with OED (and documented clinical outcomes/parameters) were identified from a cohort of patients who were prospectively recruited into a molecular biomarker study (1996-2012). The OED in 23 patients transformed into OSCC while the remaining 17 patients were in remission. Archival formalin fixed paraffin embedded (FFPE) blocks from the first biopsy confirming the diagnosis of OED, immediately preceding malignant transformation and OSCC blocks, where applicable, were retrieved. 0.4 micron thickness sections were stained with FANC-D2, ATR and H2AX (control) antibodies. Immunohistochemistry (IHC) scoring was performed by two clinicians, assessing nuclear and cytoplasmic staining extent and intensity. Corresponding FFPE cores (0.5 mm diameter) were processed for protein and DNA extraction to validate the IHC findings. Results: Based on the FANC-D2 dysplasia scoring system devised: a score ≥4 was associated with stable nontransforming OED (16 non-transformers vs. 5 transformers) and a score of ≤3 was associated with malignant transformation of OED (7 non-transformers vs. 12 transformers) (Fisher exact test p = 0.02). ATR IHC showed staining patterns which correlate with FANC-D2 expression. The findings of IHC were validated with Western blots of protein extracts from the FFPE cores stained with FANC-D2 antibodies. Conclusion: Failure to activate the FA pathway (indicated by poor expression of FANC-D2 protein) due to defective DNA damage detection by ATR has been shown to be related to malignant transformation in OED. FANC-D2 IHC has the potential to influence the management of OED where equipoise exists.