Malignant transformation of actinic cheilitis: A systematic review of observational studies.

The aim of the present systematic review was to determine the malignant transformation rate of actinic cheilitis (AC). A comprehensive literature search was conducted using Medline/PubMed, Cumulative Index of Nursing and Allied Health Literature, Scopus, OvidSP, and Google Scholar. The inclusion criteria comprised of observational human studies involving the malignant transformation of AC and publications in English. Studies included in this review were clinical follow-up, cohort, retrospective, or prospective investigations. The search yielded 1126 articles, and after exclusion, 34 full-text articles were eligible for full-text analysis. Only one article met the inclusion criteria. Based on the included article, it was determined that the malignant transformation rate of AC to squamous cell carcinoma (SCC) was 3.07%. Excluded articles focused on the clinicopathological characteristics and treatment efficacies of AC, and no malignant transformation rate was assessed. There is a need for more clinical studies on the malignant transformation of AC, as lip cancer is a public health concern. High-risk populations, including those living in tropical regions, have excessive exposure to UV radiation, and have older aged males, fair-skinned people, and smokers should be identified to prevent AC and its malignant change. Health practitioners should facilitate early intervention to prevent the progression of AC to SCC of the lip.

Differences in the enzymatic efficiency of human and bony fish AID are mediated by a single residue in the C terminus modulating single-stranded DNA binding.

Activation-induced cytidine deaminase (AID) mediates antibody diversification by deaminating deoxycytidines to deoxyuridine within immunoglobulin genes. However, it also generates genome-wide DNA lesions, leading to transformation. Though the biochemical properties of AID have been described, its 3-dimensional structure has not been determined. Hence, to investigate the relationship between the primary structure and biochemical characteristics of AID, we compared the properties of human and bony fish AID, since these are most divergent in amino acid sequence. We show that AIDs of various species have different catalytic rates that are thermosensitive and optimal at native physiological temperatures. Zebrafish AID is severalfold more catalytically robust than human AID, while catfish AID is least active. This disparity is mediated by a single amino acid difference in the C terminus. Using functional assays supported by models of AID core and surface structure, we show that this residue modulates activity by affecting ssDNA binding. Furthermore, the cold-adapted catalytic rates of fish AID result from increased ssDNA binding affinity at lower temperatures. Our work suggests that AID may generate DNA damage with variable efficiencies in different organisms, identifies residues critical in regulating AID activity, and provides insights into the evolution of the APOBEC family of enzymes.