Evaluation of hTERT Gene Expression and Chromosome 7 Copy Number Variation in Anal Squamous Intra-Epithelial Lesions: A Pilot Study

Background: Akin to cervical squamous intra-epithelial neoplasia (CIN), anal squamous intra-epithelial lesion (a-SIL) is attributed to persistent infection with high-risk human papilloma virus infection. Amplification of human telomerase reverse transcriptase (hTERT) gene and aneuploidy are known to correlate with CIN evolution. It is plausible that the underlying genetic events in a-SIL are similar. We conducted this cross-sectional analytical study with the objective of determining expression of hTERT gene expression and chromosome 7, as marker of cell ploidy in a-SIL. Methods: Conventional anal cytology was performed in 86 adult consenting subjects with history of receptive anal intercourse (RAI) and 4 controls without history of RAI. Cases with a-SIL and controls were subjected to fluorescent in-situ hybridization (FISH) to evaluate hTERT gene and chromosome 7 expression, as marker of cell ploidy. Results were expressed as number of abnormal nuclei (≥3 respective signals), maximum degree of amplification, mean signals/nucleus and proportion of cases showing abnormal nuclei. Results: Twenty cases showed a-SIL; with 15 atypical squamous cells of undetermined significance (ASCUS), 3 low grade squamous intra-epithelial lesion (LSIL) and 2 cases of high-risk cytology. Expression of both hTERT gene and chromosome 7 increased from controls to ASCUS to LSIL with concomitant increase in proportion of cases having abnormal hTERT gene and chromosome 7 expression. Conclusions: Positive association of hTERT gene with a-SIL suggests its possible role in evolution of anal squamous abnormalities. Increase in chromosome 7 also correlated positively with a-SIL. These findings corroborate the similarities between squamous carcinogenesis in CIN and a-SIL.