Antisense Oligonucleotides to Glucosylceramide Synthase Can Reverse Multidrug Resistance in Breast Cancer

Abstract

Abstract : Glucosylceramide synthase (GCS) catalyzes ceramide glycosylation, disrupts ceramide- induced apoptosis elicited by chemotherapy, and appeared to be a major cause of multidrug resistance (MDR) in cancer. Previous studies pinpoint GCS as a therapeutic target for MDR. In this work, we have synthesized antisense GCS oligodeoxyribonucleotides (asGCS cDNs) to block GCS mRNA transcription, and tested several of the oligos for chemotherapy- enhancing properties in drug resistant cancer cell models. Antisense GCS ODN-7 suppressed OCS mRNA expression (RT-PCR) by 80%, and GCS protein (Western blot) by 40%, and affected 30-fold increases in sensitivity to Adriamycin in drug resistant breast cancer MCF-7-AdrR (EC50 0.25 vs. 7.8 %). Further, asGCS ODN-7 increased MCF-7-AdrR cell sensitivity to Taxol, Vinblastine, and Actinomycin D by 3-, 9- and 11-fold, respectively. Compared to asGCS ODN-7, the GCS chemical inhibitor, PDMP (D-threo-l-phenyl-2-decanoylamino-3- morpholino-l-propanol), was less efficient and increased Adriamycin sensitivity approximately 4-fold. Subsequent studies revealed that asGCS ODN-7 overcomes drug resistance by enhancing ceramide-induced apoptosis and drug uptake. In conclusion, antisense CCs oligonucleotides effectively depress GCS expression, enhance apoptosis and drug uptake, and increase chemotherapy sensitivity, making them promising agents for cancer therapy.