Background: Patients with arsenic-induced Bowen's disease (As-BD) are at risk of developing invasive cancers in the skin, lung, and urinary bladder. However, a longitudinal follow-up study on the association between As-BD and invasive cancers is still lacking. Objectives: This study aims to investigate the underlying molecular mechanisms of this malignant progression in the skin and internal organs. Methods: This is a biopsy-based follow-up study. We tested the DNA histograms, Cyclin D1 (CCND1) protein expression and CCND1 promoter DNA methylation in 40 pathologically confirmed specimens from As-BD patients to correlate with individual's invasive cancer occurrence in the 5-year follow-up. Results: Flow cytometric DNA histogram analysis of skin specimens showed aneuploid (n=15), G2/M arrest (n=22), and normal (n=3) DNA histograms. No patients with normal DNA histograms developed invasive cancers, whereas 13 developed invasive cancers in the aneuploid group and 2 developed invasive cancers in the G2/M arrest group. The aneuploid group showed a high risk of invasive cancer development. In all assessed aneuploid specimens, the CCND1 promoter hypomethylation was observed. Statistically, percentage of un-methylation more than 55.85% among 17 detected CpG sites showed extremely high predictive power in the occurrence of invasive arsenical cancers. Furthermore, the un-methylation at -56 and -54bp CpG sites was statistically significantly associated with invasive arsenical cancer development (p=1.29×10-5). Conclusions: As-BD lesions showing an aneuploid DNA histogram had a high risk of invasive cancer development. Un-methyaltion at -56 and -54. bp CpG in the CCND1 promoter serves as a predictor for invasive progression in As-BD patients.
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