Journal Article

Resistance to skin tumorigenesis in DNAPK-deficient SCID mice is not due to immunodeficiency but results from hypersensitivity to TPA-induced apoptosis

Christopher J. Kemp, Khoa Vo and Kay E. Gurley

in Carcinogenesis

Volume 20, issue 11, pages 2051-2056
Published in print November 1999 | ISSN: 0143-3334
Published online November 1999 | e-ISSN: 1460-2180 | DOI: http://dx.doi.org/10.1093/carcin/20.11.2051
Resistance to skin tumorigenesis in DNAPK-deficient SCID mice is not due to immunodeficiency but results from hypersensitivity to TPA-induced apoptosis

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Scid/scid mice have a mutation in the gene encoding the catalytic subunit of DNA-dependent protein kinase (DNAPKcs) and are defective in end joining of DNA double-strand breaks. As a consequence, they are radiosensitive, lack mature T and B lymphocytes and are predisposed to lymphomagenesis. To determine if this DNA repair defect also increased predisposition to skin tumor formation, we treated the dorsal skin of scid/scid mice with the carcinogen 7,12-dimethylbenz[a]anthracene followed by the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA). Contrary to expectations, we observed a 5-fold reduction in skin tumor multiplicity in scid/scid mice. We addressed whether this was related to their immunodeficiency by similarly treating Rag1–/– and Rag2–/– knockout mice which also lack mature T and B lymphocytes. We observed no difference in skin tumor multiplicity for either strain compared with control littermates. This indicates a lack of a significant role for T or B lymphocyte mediated immunity on either papilloma or carcinoma formation. We observed a significant increase in apoptotic and necrotic cell death in follicular and interfollicular epithelial cells of scid/scid mice following TPA treatment. This hypersensitivity of SCID (severe combined immunodeficient) cells to TPA indicates that the resistance to skin tumor formation in scid/scid mice is due to loss of initiated cells through TPA-induced cell killing.

Keywords: DMBA, dimethylbenz[a]anthracene; DNAPK, DNA-dependent protein kinase; dsbs, double-stranded breaks; SCID, severe combined immunodeficient; TPA, 12-O-tetradecanoylphorbol-13-acetate.

Journal Article.  4784 words.  Illustrated.

Subjects: Clinical Cytogenetics and Molecular Genetics

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