Tumor suppression in human skin carcinoma cells by chromosome 15 transfer or thrombospondin-1 overexpression through halted tumor vascularization

Abstract

The development of skin carcinomas presently is believed to be correlated with mutations in the p53 tumor suppressor and ras gene as well as with the loss of chromosome 9. We now demonstrate that, in addition, loss of chromosome 15 may be a relevant genetic defect. Reintroduction of an extra copy of chromosome 15, but not chromosome 4, into the human skin carcinoma SCL-I cells, lacking one copy of each chromosome, resulted in tumor suppression after s.c. injection in mice. Transfection with thrombospondin-1 (TSP-1), mapped to 15q15, induced the same tumor suppression without affecting cell proliferation in vitro or in vivo. Halted tumors remained as small cysts encapsulated by surrounding stroma and blood vessels. These cysts were characterized by increased TSP-1 matrix deposition at the tumor͞stroma border and a complete lack of tumor vascularization. Coinjection of TSP-1 antisense oligonucleotides drastically reduced TSP-1 expression and almost completely abolished matrix deposition at the tumor͞stroma border. As a consequence, the tumor phenotype reverted to a well vascularized, progressively expanding, solid carcinoma indistinguishable from that induced by the untransfected SCL-I cells. Thus, these data strongly suggest TSP-1 as a potential tumor suppressor on chromosome 15. The data further propose an unexpected mechanism of TSP-1-mediated tumor suppression. Instead of interfering with angiogenesis in general, in this system TSP-1 acts as a matrix barrier at the tumor͞stroma border, which, by halting tumor vascularization, prevents tumor cell invasion and, thus, tumor expansion.

UVA radiation causes DNA strand breaks, chromosomal aberrations and tumorigenic transformation in HaCaT skin keratinocytes

“…One exception may be loss of chromosome 15, the only common aberration. We previously showed that loss of chromosome 15 correlated with loss of the angiogenesis inhibitor TSP-1 which in turn correlated with the angiogenic switch required for malignant conversion (Folkman and Hanahan, 1991;Bleuel et al, 1999). We recently also showed that loss of chromosome 15 occurs in human skin carcinomas and that this correlated with progression from benign to malignant tumor phenotype (Burnworth et al, 2006).…”

Identification of fibroblast growth factor-8b target genes associated with early and late cell cycle events in breast cancer cells

“…epithelial membrane protein 1 (Emp1), Dusp4 and cyclin D) are proteins associated with proliferation and tumorigenesis (Bartkova et al, 1994;Hippo et al, 2001;Wang et al, 2003;Wang et al, 1994). Correspondingly, antiproliferative genes such as Btg2 and genes with tumor suppressor functions such as Fibroblast growth factor 2 (FGFR2) (Eswarakumar et al, 2005) and Thrombospondin-1 (TSP-1) (Bleuel et al, 1999;Castle et al, 1997) were down regulated in response to FGF-8b (Supplemental table 2 is a large glycoprotein secreted by various cell types. In normal mammalian tissue TSP-1 is a natural occurring angiogenic inhibitor which helps to maintain the normal quiescent vasculature (Bouck et al, 1996;Good et al, 1990;Hanahan and Folkman, 1996).…”

“…In normal mammalian tissue TSP-1 is a natural occurring angiogenic inhibitor which helps to maintain the normal quiescent vasculature (Bouck et al, 1996;Good et al, 1990;Hanahan and Folkman, 1996). Because of its antiangiogenic properties, overexpression of TSP-1 slows tumor growth in various experimental mouse models including breast cancer (Bleuel et al, 1999;Castle et al, 1997;Weinstat-Saslow et al, 1994;Volpert et al, 1998). Suppression of TSP-1 mRNA and protein in response to FGF-8b in breast cancer cells has also been shown in a previous study by our group (Mattila et al, 2006) which strengthens the finding of this study.…”

Tumorigenic conversion of immortal human skin keratinocytes (HaCaT) by elevated temperature

“…HaCaT cells were routinely cultured as described (Boukamp et al, 1988) and tumor formation was analysed as previously described (Bleuel et al, 1999). To recultivate cells from nude mouse tumors, these were excised, quickly rinsed in 70% ethanol, thoroughly washed in MEM culture medium and minced.…”