Advanced melanoma is difficult to treat, in part because of greater resistance to therapy compared with other cancer types. The mechanisms underlying this resistance are not well-understood. One factor that is reported to be involved in melanoma cell survival is PAX3, a transcription factor normally expressed during embryonic development, and which is critically required for development of neural crestderivatives, including skin melanocytes. PAX3 expression is deregulated in primary melanomas and most melanoma cell lines. Here we have investigated whether targeting PAX3 expression in melanoma cell lines together with chemotherapeutic treatment increases susceptibility to therapeutic cell death. Using PAX3-specific antisense oligodeoxynucleotides (PAX3-AS) to treat melanoma cell lines in vitro, we showed dose-dependent reduction of proliferation of melanoma cells, and induction of apoptosis compared with control treatments. Induction of apoptosis was accompanied by the induction of active caspase-3 in UACC62 and M14 cells, and p53 protein in UACC62 cells.

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Abstract— Effects of ultraviolet and visible radiation on the viability of Landschutz ascites tumour cells have been tested by growing control and treated tumour samples in adult mice. The tumour cells were irradiated as a dilute suspension in isotonic buffered salt solution, and were equilibrated at 0°C with oxygen or with nitrogen before irradiation. Tumour cell proliferation was measured by a variety of techniques. The preferred assay‐method was the growth of solid tumours in the axillae and groins of mice after sub‐cutaneous inoculation of varying dilutions of treated or control ascites tumour cells. The immune response of the mice to the injected cells was reduced by whole body irradiation with a 300r dose of x‐rays two days before inoculation. Results were calculated from parallel line assays using the reciprocal of the delay in appearance of the solid tumours up to 30 days post‐innoculation. This reciprocal (1/T) was linearly related to the logarithm of the number of cells inoculated. Photoreactivation has been demonstrated for this system, in which both U.V. and visible radiations were absorbed by the same cells. Light delivered alone in oxygen or in nitrogen was without effect on cell‐viability, but it increased cell‐survival after u.v.‐irradiation in nitrogen and decreased survival after u.v.‐irradiation in oxygen. Ultraviolet radiation alone was not significantly more lethal in oxygen than in nitrogen. A further observation in this work was an interaction between irradiated and control tumour cells injected into the same animal. It is suggested that the radiation used may affect the antigenic character of the tumour cells as well as their reproductive capadity.

Integrins have become a target for novel therapeutic strategies against malignant gliomas. Cilengitide, a synthetic Arg-Gly-Asp (RGD)-motif peptide, interferes with ligand binding to avb3 and avb5 integrins and is currently investigated in clinical trials. Integrins may also be involved in the activation of transforming growth factor (TGF)-b, a mediator of invasiveness and immune escape of glioma cells. Using flow cytometry, we demonstrate that the target integrins of cilengitide are expressed not only in glioblastoma blood vessels, but also by tumor cells. After exposure of glioma cells to cilengitide, we noticed reduced phosphorylation of Smad2 in most glioma cell lines, including stem-like glioma cells. Phophorylation of Smad2, but not cilengitide-induced detachment, is rescued by addition of recombinant TGF-b. Administration of cilengitide to glioma cells results in reduced TGF-b-mediated reporter gene activity. Furthermore, exposure to cilengitide leads to decreased TGF-b 1 and TGF-b 2 mRNA and protein expression. These effects are mimicked by blocking av, b3 or b5 antibodies or by silencing of integrins av, b3, b5 or b8 using RNA interference. Treatment of mice bearing experimental LN-308 glioma xenografts with cilengitide results in reduced pSmad2 levels. Taken together, cilengitide may exert anti-invasive and immune stimulatory activity in human glioblastoma patients by its anti-TGF-b properties.

Abstract— The growth of ultraviolet‐irradiated ascites tumour cells in adult animals which have received a total‐body dose of x‐radiation appears to be a suitable method to obtain data on the survival of the treated tumour cells, if the dose of total‐body radiation and its time before tumour cell inoculation are chosen correctly. In assessing tumour cell survival, the analysis of the time of appearance of the resulting solid tumours, using the linear relationship between the reciprocal of this time and the logarithm of the number of cells injected is preferred to probit or to Reed‐Muench analysis of the number of tumour‐takes. The 1/T method of analysis yields more precise estimates of the survival ratios and greater economy in the use of host animals without a disproportionate increase in the labour involved in obtaining the data. An application of this method to the determination of survival‐ratios of u.v.‐irradiated Landschütz ascites tumour cells is described.