Vitamin D3 is a potent inhibitor of tumor cell-induced angiogenesis.

Vitamin D3 derivative 1,25-dihydroxyvitamin D3 (1,25[OH]2D3) exerts various biological effects in cells that possess vitamin D3 receptor (VDR), including enhancement of cell differentiation and inhibition of cell proliferation. These activities of 1,25(OH)2D3 might be responsible for its anti-neoplastic effects, as shown in various experimental systems. The aim of this study was to compare the anti-angiogenic activity of 1,25(OH)2D3, retinoids, and interleukin-12 (IL-12) in an experimental tumor cell-induced angiogenesis assay in mice. Tumor cell-induced angiogenesis assay was performed in x-ray immunosuppressed BALB/c mice by intradermal injections of human tumor cell lines of different origin. The injections resulted within 3 d in a local formation of new blood vessels, and the intensity of angiogenesis correlated with the number of injected cells. Systemic treatment of the mouse recipients with 1,25(OH)2D3 significantly decreased angiogenesis, comparable to the effect of retinoids (all-trans retinoic acid [RA], 9-cis RA and 13-cis RA) and of IL-12. In vitro preincubation of the cells with all compounds (except IL-12) led to the inhibition of their angiogenic capability in vivo. Moreover, combination of 1,25(OH)2D3 and retinoids resulted in a synergistic inhibition of angiogenesis. The results strongly suggest that anti-angiogenic compounds with relatively low toxicity (e.g., 1,25(OH)2D3, retinoids, and IL-12) and their combinations could be beneficial in the treatment of some angiogenesis-associated malignancies.

A mouse model for studying epidermodysplasia-verruciformis-associated carcinogenesis.

Epidermodysplasia verruciformis (EV) is considered as a model of genetic cancer due to unusual susceptibility to EV-specific human papillomaviruses (HPVs). We established an in vivo experimental system for long-term propagation of EV tissue which should facilitate the study of tumor progression in EV. Skin fragments from benign and early pre-malignant lesions of 6 EV patients were grafted under the kidney capsule of athymic mice. After several months the grafted tissue formed epidermal cysts. These cysts showed typical EV cytopathic effect, in situ hybridization revealed the presence of HPV 5, 8, 9, 12 and 36 DNA, and immunoperoxidase staining detected papillomavirus-group-specific antigens in the permissive cells of the cysts. In some cysts, there were numerous mitoses and downward proliferation of the epidermis with slight dyskeratotic changes. The experimental system described constitutes a model for studies on the role of HPV and other co-factors in human cutaneous carcinogenesis.

Systemic administration of 2-chloro-2'-deoxyadenosine (2-CdA) in patients with systemic scleroderma.

Three patients with diffuse variety of systemic scleroderma were treated with 2-chloro-2'-deoxyadenosine. In two of them a moderate improvement of skin involvement was observed. No significant effects of the drug on the immunological parameters have been found.

Adhesion of peripheral blood mononuclear cells to vascular endothelium in patients with systemic sclerosis (scleroderma).

OBJECTIVE: Perivascular infiltrates in skin, subcutaneous tissue, and internal organs are a characteristic feature of early systemic sclerosis (SSc). We studied the first step of migration of peripheral blood mononuclear cells (PBMC) through the vessel wall to the extravascular space, i.e., adhesion of PBMC to endothelial cells (EC), in patients with various forms of SSc (limited scleroderma, diffuse scleroderma, and the transitional form). METHODS: Radioisotope-labeled patient PBMC were coincubated with umbilical cord EC in vitro, and the percentage adhesion was measured. RESULTS: Adhesion of PBMC to EC was markedly decreased, while adhesion of isolated active rosette-forming cells (ARFC) was significantly increased, in SSc patients compared with healthy controls. Decreased adhesion of PBMC to EC was found to correlate with a diminished percentage of ARFC in the peripheral blood. Preincubation of PBMC from healthy donors with interleukin-2 (IL-2) enhanced their adhesion to EC, while preincubation of PBMC from SSc patients with this cytokine resulted in a decrease in adhesion in 10 of 14 individuals. IL-1, interferon-gamma, and transforming growth factor beta had no significant effect on adhesion of SSc patient PBMC to EC. Differences in adhesion of PBMC to EC among the SSc subgroups were not significant. CONCLUSION: Our findings suggest that in SSc, activation of subpopulations of PBMC leads to their enhanced adhesion to vascular endothelium in vivo and to migration of these cells to the extravascular space, resulting in the elimination from the peripheral blood of those PBMC with high ability to adhere to EC.

Acitretin decreases tumor cell-induced angiogenesis.

The effects of acitretin and etretinate on angiogenesis induced in Balb/c mice by intradermal injection of keratinocyte tumor cell lines were evaluated. It was shown that both retinoids are capable of inhibiting angiogenesis evoked by a human epidermoid carcinoma cell line (A431). Acitretin, but not etretinate, inhibited also angiogenesis induced by the spontaneously transformed murine keratinocyte cell line Pam 212 and by the established tumorigenic SKv cell line harboring the HPV16 genome. We suggest that inhibition of blood vessel formation may be one of the mechanisms responsible for the anticancerogenic effect of retinoids.

Beta-carotene in prevention of cutaneous carcinogenesis.

Beta-carotene, administered orally to mice, caused a decrease in angiogenesis evoked by HPV-transformed tumorigenic cell lines (SKv-t, HeLa). It did not affect angiogenesis induced by the non-tumorigenic SKv (not-t) cell line, and increased lymphocyte-induced immune angiogenesis. We suggest that the anti-cancerogenic effect of beta-carotene may be due, at least in part, to its inhibitory effect on formation of new blood vessels within the tumour mass.