Inducible cutaneous inflammation reveals a protumorigenic role for keratinocyte CXCR2 in skin carcinogenesis.

Transgenic mice that overexpress PKCalpha in the epidermis (K5-PKCalpha mice) exhibit acute CXCR2-mediated intraepidermal neutrophilic inflammation and a strong epidermal hyperplasia in response to application of 12-O-tetradecanoylphorbol-13-acetate (TPA). We now show that hyperplasia is independent of infiltrating neutrophils. Furthermore, when K5-PKCalpha mice were initiated with 7,12-dimethylbenz(a)anthracene (DMBA) and promoted with a low dose of TPA, 58% of K5-PKCalpha mice developed skin papillomas that progressed to carcinoma, whereas wild-type mice did not develop tumors.

The high-risk benign tumor: evidence from the two-stage skin cancer model and relevance for human cancer.

Benign tumors that form following chemical initiation and promotion in the mouse skin can be grouped into two classes. The majority of papillomas do not progress to squamous cell carcinoma (SCC), and these are designated as low-risk or terminally benign papillomas. In contrast, a much smaller group forms the true precursor to the SCC, and these have a significantly higher frequency and rate of malignant conversion than the bulk of low-risk papillomas.

Expression profile of skin papillomas with high cancer risk displays a unique genetic signature that clusters with squamous cell carcinomas and predicts risk for malignant conversion.

Chemical induction of squamous tumors in the mouse skin induces multiple benign papillomas: high-frequency terminally benign low-risk papillomas and low-frequency high-risk papillomas, the putative precursor lesions to squamous cell carcinoma (SCC). We have compared the gene expression profile of twenty different early low- and high-risk papillomas with normal skin and SCC. Unsupervised clustering of 514 differentially expressed genes (P<0.

Methylation of the O6-methylguanine-DNA methyltransferase promoter suppresses expression in mouse skin tumors and varies with the tumor induction protocol.

Hypermethylation of CpG sites within the promoter region of the O6-methylguanine-DNA methyltransferase (MGMT) gene occurs frequently in human cancer, preventing both MGMT expression and repair of alkylation damage. To assess the role of MGMT in the development of mouse skin tumors induced by initiation-promotion protocols, methylation of the MGMT promoter was examined in tumor DNA using methylation-specific PCR. To determine whether MGMT promoter methylation was affected by the tumor induction protocol, tumors were initiated by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) or 7,12-dimethylbenz[a]anthracene (DMBA) and promoted by 12-O-tetradecanoylphorbol-13-acetate (TPA) or mezerein.

Strain-dependent differences in malignant conversion of mouse skin tumors is an inherent property of the epidermal keratinocyte.

The multistage evolution of squamous skin tumors induced by chemical or viral carcinogens on mice from different genetic backgrounds has been a valuable model to define low penetrance loci that determine cancer susceptibility or resistance. Susceptibility determinants are multigenic, stage-specific, dependent on the carcinogenesis protocol, and in the case of initiating events, intrinsic properties of keratinocytes. In this study we examined the malignant conversion frequency of keratinocytes derived from FVB/N, inbred SENCARA/Pt, BALB/c or C57BL/6 mouse strains that differ substantially in the frequency of progression from papilloma to carcinoma.