Mutations in DNA polymerase η are not detected in squamous cell carcinoma of the skin

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The major etiological agent in skin cancer is exposure to UV-irradiation and the concomitant DNA damage. UV-induced DNA lesions, such as thymine dimers, block DNA synthesis by the major DNA polymerases and inhibit the progression of DNA replication. Bypass of thymine dimers and related lesions is dependent on the translesion polymerase DNA polymerase η (Polη). In the inherited disorder, xeroderma pigmentosum variant (XPV), inactivation of Polη results in extreme sensitivity to UV light and a marked increase in the incidence of skin cancer. Here, we tested the hypothesis that somatic mutations and/or polymorphisms in thePOLHgene that encodes Polη are associated with the induction of UV-dependent skin cancers. We sequenced the exonic regions of the Polη open reading frame in DNA from 17 paired samples of squamous cell skin carcinoma and adjacent histologically normal tissue. We analyzed approximately 120,000 nucleotides and detected no mutations inPOLHin the tumors. However, we identified 6 different single-nucleotide polymorphisms, 3 of them previously undocumented, which were present in both the tumor and paired normal tissue. We conclude that neither mutations nor polymorphisms in the coding regions ofPOLHare required for the generation of human skin squamous cell carcinoma.

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