The effect of pentamidine on melanoma ex vivo.

Pentamidine is a small molecule inhibitor of the Ca(+)-binding protein S100B and disrupts the S100B-p53 protein-protein interaction; this is thought to restore wild-type p53 tumour suppressor function in melanoma. Additional anticancer effects may be the result of inhibition of regenerating liver family phosphatases. In this study, we have used a standardized ATP-tumour chemosensitivity assay to investigate the effect of pentamidine on cells derived from 18 skin melanoma samples and one uveal melanoma sample. The cells were tested at six concentrations from which the IC(50) and IC(90) were calculated. To allow comparison between samples, an index(sum) was calculated based on the percentage of tumour growth inhibition at each concentration. Of the skin melanoma samples tested, 78% exhibited an index(sum) less than 300 indicating strong inhibition. The median index(sum) of 237 also indicates considerable activity against these samples. The median IC(90) (30.2 micromol/l) may be clinically achievable in a proportion of patients. The uveal melanoma sample exhibited an index(sum) of 333 indicating moderate inhibition, and 86% inhibition at test drug concentration (37.96 micromol/l). These results show that pentamidine has activity against melanoma, and support the prospect of its development for therapeutic use.

Resistance gene expression determines the in vitro chemosensitivity of non-small cell lung cancer (NSCLC).

BACKGROUND: NSCLC exhibits considerable heterogeneity in its sensitivity to chemotherapy and similar heterogeneity is noted in vitro in a variety of model systems. This study has tested the hypothesis that the molecular basis of the observed in vitro chemosensitivity of NSCLC lies within the known resistance mechanisms inherent to these patients' tumors. METHODS: The chemosensitivity of a series of 49 NSCLC tumors was assessed using the ATP-based tumor chemosensitivity assay (ATP-TCA) and compared with quantitative expression of resistance genes measured by RT-PCR in a Taqman Array following extraction of RNA from formalin-fixed paraffin-embedded (FFPE) tissue. RESULTS: There was considerable heterogeneity between tumors within the ATP-TCA, and while this showed no direct correlation with individual gene expression, there was strong correlation of multi-gene signatures for many of the single agents and combinations tested. For instance, docetaxel activity showed some dependence on the expression of drug pumps, while cisplatin activity showed some dependence on DNA repair enzyme expression. Activity of both drugs was influenced more strongly still by the expression of anti- and pro-apoptotic genes by the tumor for both docetaxel and cisplatin. The doublet combinations of cisplatin with gemcitabine and cisplatin with docetaxel showed gene expression signatures incorporating resistance mechanisms for both agents. CONCLUSION: Genes predicted to be involved in known mechanisms drug sensitivity and resistance correlate well with in vitro chemosensitivity and may allow the definition of predictive signatures to guide individualized chemotherapy in lung cancer.