Altered expression of transforming growth factor‐β1 mrna and protein in mouse skin carcinogenesis

Abstract

Transforming growth factor (TGF)-beta 1, whose gene is located on mouse chromosome 7, has been proposed to be involved in skin carcinogenesis. In the study presented here, we demonstrated that single topical treatments with different types of tumor promoters, i.e., the protein kinase C activator 12-O-tetradecanoylphorbol-13-acetate (TPA, 2 micrograms); the non-protein kinase C activators anthralin (22.6 micrograms), benzoyl peroxide (20 mg), and cumene hydroperoxide (1.2 mg); the first-stage tumor promoters 4-O-methyl-TPA (500 micrograms) and A23187 (166 micrograms); and the second-stage tumor promoter mezerein (2 micrograms) produced transient induction of TGF-beta 1 mRNA in SSIN (inbred SENCAR) mouse skin. The time of maximum induction varied from 3 to 12 h; the relative extent of induction was ranked as cumene hydroperoxide > benzoyl peroxide > anthralin > TPA > 4-O-methyl-TPA > mezerein > A23187. These findings suggested that TGF-beta 1 mRNA induction is a common response of skin to several types of complete and stage-specific promoters; however, the extent of induction did not correlate with the reported hyperplastic activity of single applications of these promoters. We also demonstrated that TGF-beta 1 mRNA expression in papillomas of SENCAR mice generally correlated with expression levels of cyclin D1, another gene on chromosome 7, and with stage of tumor progression. TGF-beta 1 mRNA expression was constitutively elevated in most squamous cell carcinomas from either initiation-promotion or complete carcinogenesis protocols. Cell lines established from carcinomas also overexpressed TGF-beta 1 mRNA. Immunohistochemical staining of tissue sections of normal and TPA-treated skin revealed the presence of extracellular TGF-beta 1 protein in the dermis and intracellular TGF-beta 1 protein in the epidermis, especially in the suprabasal layers. The staining patterns of papillomas varied, with 62 +/- 13% of the tissue showing strong intracellular staining but only 25 +/- 8% of the connective tissue staining for extracellular TGF-beta 1. Variable staining patterns were also found in carcinomas; some areas stained heavily for both the intracellular and extracellular forms of TGF-beta 1. Overall, 28 +/- 6% of the tissue of the 12 analyzed carcinomas stained for the intracellular form and 18 +/- 5% for the extracellular form of TGF-beta 1.

Smads mediate signaling of the TGFβ superfamily in normal keratinocytes but are lost during skin chemical carcinogenesis

“…Treatment of both proliferative and dierentiated keratinocytes with 1 ng/ml TGFb1 for 24 h did not signi®cantly alter mRNA levels of Smad1 through -5 ( Figure 1a). In addition, although it has been documented that the TGFb transcripts are elevated in chemically-induced papillomas and SCC (Akhurst et al, 1988;Fowlis et al, 1992;Krieg et al, 1991;Patamalai et al, 1994;Rundhaug et al, 1997;Sherman et al, 1993), we did not observe signi®cant changes in the level of Smad1 through ®ve transcripts in papillomas or SCC (Figure 1b). Transcripts of Smad6 were undetectable in all samples examined (not shown).…”

Expression of the TGF-β coreceptor endoglin in epidermal keratinocytes and its dual role in multistage mouse skin carcinogenesis

“…Although the molecular mechanism by which endoglin modulates TGF-b responses remains to be determined, a recent report suggests that by directly et al, 2002). TGF-b 1 is an endogenous regulator of epidermal homeostasis that is preferentially expressed in suprabasal layers, where it is thought to block proliferation of differentiating keratinocytes (Akhurst et al, 1988;Fowlis et al, 1992;Patamalai et al, 1994). Interestingly, endoglin is synthesized in basal proliferative keratinocytes, the appropriate cell type to counteract the negative regulation of growth exerted by this factor.…”

Opposite effect of stable transfection of bioactive transforming growth factor-β1 (TGFβ1) versus exogenous TGFβ1 treatment on expression of 92-kDa type iv collagenase in mouse skin squamous cell carcinoma CH72 cells

“…TGFβ1 is growth inhibitory for normal (as well as some transformed) epithelial, endothelial, and hematopoietic cells [6,7], including normal keratinocytes in culture [8]. In normal skin, intracellular TGFβ1 protein staining has been shown in nonproliferating, suprabasal keratinocytes [9][10][11]. Loss of responsiveness to the growthinhibitory effects of TGFβ1 has been associated with malignant progression in the mouse skin model [12,13] as well as in other model systems [14][15][16][17].…”