Identification of Dss1 as a 12-O-Tetradecanoylphorbol-13-acetate-responsive Gene Expressed in Keratinocyte Progenitor Cells, with Possible Involvement in Early Skin Tumorigenesis

Abstract

This study identifies genes expressed early in 12-Otetradecanoylphorbol-13-acetate (TPA)-induced skin carcinogenesis in genetically initiated Tg⅐AC v-Ha-ras transgenic mice. Keratinocyte progenitor cells from TPA-treated Tg⅐AC mice were isolated with fluorescence-activated cell sorting and expression was analyzed using cDNA microarray technology. Eleven genes were identified whose expression changed significantly in response to carcinogen treatment. Deleted in split hand/split foot 1 (Dss1) is a gene associated with a heterogeneous limb developmental disorder called split hand/split foot malformation. cDNA microarray expression analysis showed that the mouse homologue of Dss1 is induced by TPA. Dss1 overexpression was detected by Northern blot analysis in early TPA-treated hyperplastic skins and in JB6 Cl 41-5a epidermal cells. Interestingly, Dss1 expression was also shown to be elevated in skin papillomas relative to normal skins, and further increased in squamous cell malignancies. Functional studies by ectopically constitutive expression of Dss1 in JB6 Cl 41-5a preneoplastic cells strongly increased focus formation and proliferation of these cells and enhanced efficiency of neoplastic transformation of the cells in soft agar. These results strongly suggest that Dss1 is a TPA-inducible gene that may play an important role in the early stages of skin carcinogenesis.Skin carcinogenesis is a complex multistage process that progresses through distinct stages of initiation, promotion, progression, and malignancy (1-3). The Tg⅐AC mouse is a genetically modified (transgenic) form of the FVB/N mouse strain that carries a genomic copy of the v-Ha-ras gene fused to a fetal -globin gene promoter (4). Tg⅐AC mice have already entered the initiation stage of cancer development and have a higher sensitivity to many types of environmentally inducible cancer than wild type mice. Tg⅐AC mice develop hyperplasia in skin keratinocytes after exposure to tumor promoters such as TPA 1 (4), full thickness wounding (5), ultraviolet radiation (6), or carcinogens such as 7,12-dimethylbenz[a]anthracene (7). These hyperplasias eventually develop into benign papillomas, some of which become malignant tumors such as squamous cell carcinomas or spindle cell tumors (7). The in vivo Tg⅐AC mouse model is a valuable tool to study the early stages of skin carcinogenesis.The epidermis is a stratified, rapidly renewing tissue in which terminally differentiated cells are continuously lost from the skin surface and replaced by an intricate and highly regulated proliferative process. Skin cells are regenerated through the proliferative capacity of keratinocyte stem cells (KSCs) and transit amplifying (TA) cells in the basal layer. KSCs are a minor subpopulation of relatively quiescent cells that have broad proliferative potential and an unlimited capacity for self-renewal (8, 9). It has been proposed that carcinogens generate mutations in the population of stem cells which are transformed them into initiated preneoplastic cells (10). It has also been r...

DSS1 is required for the stability of BRCA2

“…Characterization of the endogenous DSS1 protein Previous studies have shown that endogenous human and mouse DSS1 cannot be detected by Western blotting, although both recombinant and yeast DSS1 are detectable by this method (Jantti et al, 1999;Marston et al, 1999;Wei et al, 2003;Gudmundsdottir et al, 2004;Isono et al, 2004;Sone et al, 2004). To detect endogenous human DSS1, we generated an anti-DSS1 antiserum against a full-length DSS1 GST-fusion protein.…”

“…Recently, DSS1 (sem1p/RPN7) has been found to form a structural subunit of the 26S proteasome and is required for the structural integrity of the 26S proteasome (Isono et al, 2004;Sone et al, 2004). DSS1 has also been identified as a 12-O-tetradecanoylphorbol-13-acetate-responsive gene expressed in keratinocyte progenitor cells that may be involved in early skin tumorigenesis (Wei et al, 2003).…”

Biological, cellular, and molecular characteristics of an inducible transgenic skin tumor model: a review

“…A total of 11 genes were identified as either upregulated (nine genes, including galectin 7, nucleoside diphosphate kinase B, keratin 14, Dss1, and a double-strand break repair RAD21 homolog) or downregulated (two genes, including keratin 15 and apoliprotein E precursor) in CD34 þ cells from TPA-treated mice. Further characterization of Dss1 has revealed that (1) Dss1 is overexpressed in TPA-induced hyperplastic skin, papillomas, and cutaneous malignancies; (2) constitutive expression of Dss1 promoted cell proliferation and soft agar growth in preneoplastic epidermal cell lines, demonstrating in vitro transformation potential and defining a possible role for Dss1 in early TPA-induced neoplastic development (Wei et al, 2003).…”

“…The advent and use of gene array technology has revealed TPA-inducible genes involved in the Tg.AC tumorigenic response (Wei et al, 2003). Ongoing studies continue to explore the role Dss-1, NDPK-B, and other genes involved in the early stage of neoplastic development and skin tumorigenesis.…”

“…The identification of CD34 as a selectable determinant of follicular bulge cells allowed us to identify several important candidate genes that may contribute to tumor development. CD34 þ keratinocytes were isolated from either TPA-treated or untreated Tg.AC skin, and a gene expression profile was developed using cDNA nylon arrays (Wei et al, 2003). A total of 11 genes were identified as either upregulated (nine genes, including galectin 7, nucleoside diphosphate kinase B, keratin 14, Dss1, and a double-strand break repair RAD21 homolog) or downregulated (two genes, including keratin 15 and apoliprotein E precursor) in CD34 þ cells from TPA-treated mice.…”