Intrinsic and acquired multidrug-resistance (MDR) and the activity of the enzyme telomerase have been demonstrated in human melanoma. A direct regulation of the MDR pathways and of telomerase by interpheron-α (IFN-α), which is currently used in the therapy of advanced cutaneous melanoma, has also been hypothesized. In this study, we used five melanoma cell lines not selected in vitro for drug resistance (Me665/2/21, Me665/2/60, HT-144, SK-MEL-28, and SK-MEL-5), which in a previous study, had shown different responses to IFN-α in terms of proliferation, apoptosis, telomerase activity and expression of mRNA for the human telomerase reverse transcriptase (hTERT). We investigated the expression of the multidrug resistance (MDR1) gene, multidrug resistance protein (MRP), lung resistance protein (LRP), topoisomerase IIα (Topo IIα), hTERT, and telomerase-associated protein (TEP1), which is shared by telomerase and vault MDR proteins at the mRNA expression level, using the reverse transcription-PCR (RT-PCR). All cell lines showed an intrinsic expression of hTERT, TEP1, and MDR gene transcripts (only MDR1 mRNA was under the detection level in SK-MEL-28 cells). After IFN-α exposure, we observed either no effect, a trend towards a decrease of hTERT, MRP, and Topo IIα, or an increase of TEP1, MDR1, and LRP mRNA expression in some cell lines. Effects were usually temporary and not always significant. No correlation was found between hTERT and TEP1 mRNA expression, whereas significant positive correlations were found between TEP1 and MDR1 mRNA, and between TEP1 and LRP mRNA. IFN-α modulates differently MDR gene transcripts in human melanoma cell lines. Positive correlation between TEP1 and LRP also seems to identify them as common targets of IFN-α effects.

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