Quercetin and tamoxifen sensitize human melanoma cells to hyperthermia.

Hyperthermia produces regression of human cancer. Because hyperthermia has produced only limited results, attention has focused on searching for substances able to sensitize tumour cells to the effects of hyperthermia. The flavonoid quercetin has been reported to be a hyperthermic sensitizer in ovarian and uterine cervical tumours and in leukaemia. Quercetin and tamoxifen inhibit melanoma cell growth. We therefore investigated whether quercetin and tamoxifen can sensitize M10, M14 and MNT1 human melanoma cells to hyperthermia. We observed that both quercetin and tamoxifen synergize with hyperthermia (42.5 degrees C) in reducing the clonogenic activity of M14 and MNT1 and in inducing apoptotic cell death in all three cell lines. As revealed by flow cytometric and Northern blot analyses, quercetin and tamoxifen reduced heat shock protein-70 expression at both protein and mRNA levels. Our results suggest that quercetin and tamoxifen can be usefully combined with hyperthermia in the therapy of recurrent and/or metastatic melanoma.

Antitumor activity of the proteinase inhibitor tetra-p-amidinophenoxyneopentane in a nude mouse model of human melanoma.

An aromatic poly-amidine (tetra-p-amidinophenoxyneopentane, TAPP-Br) exhibiting anti-proteinase activity and known to exert antitumor activity in vitro was analysed for its ability to inhibit the in vivo growth of a human melanoma cell line transplanted in nude mice. 5 X 10(6) melanoma cells were injected subcutaneously in groups of nude mice and treatment with TAPP-Br was performed (0.125-1 mg/0.2 ml injections, repeated three times at the beginning of the experiment and after 20 days). After 25 days tumors displaying a volume of 0.9-1.8 cm3 were detectable in control untreated mice. Mice treated with TAPP-Br on the other hand did not develop sizable tumors or consistently developed tumors of significantly smaller sizes. Despite these therapeutic effects, significant chronic toxicity of the compound was observed when administered at higher dosage (500-1000 micrograms). These side effects, which may hamper the therapeutic use of TAPP-Br, are likely to be circumvented by alternative routes of administration or by vehiculation into liposomes. These alternative strategies of treatment are currently investigated.

Effect of sequential application of hyperthermia and chemotherapy on the survival of a thermoresistant human melanoma cell line.

The human melanoma cell line M14 has been proven in previous experiments to be much less sensitive to the action of heat (42 degrees C, 60 min) than other melanoma lines. In the present study, we have investigated the possibility of increasing the effect of heat by means of drug treatment. Thermochemotherapy was applied to exponentially growing cells according to different schedulings, and was analyzed in its efficacy by measuring the impairment of the cellular colony-forming ability. Findings of the present study point out that: (a) appropriate sequencing between hyperthermia and cis-diamminedichloroplatinum II(DDP), melphalan (L-Pam), 1,2,4-dichlorobenzyl-1H-indazol-3-carboxylic acid (LNA) or 5-3,3-dimethyl-1-triazeno-imidazole-4-carboxamide (DTIC) strongly influences the cytotoxic effect of the two agents; and (b) the optimal combination appears to be the simultaneous application of heat and drugs. However, as far as thermochemotherapy with DDP is concerned, a synergistic effect may also be achieved when hyperthermia precedes DDP.