[1695] Suppression of Glucosylceramide Synthase Gene Expression: A Novel Approach for Cancer Treatment

Y-Y Liu, GA Patwardhan, D Ying, M Jazwinski, J Bao. University of Louisiana, Monroe, LA; Tulane University School of Medicine, New Orleans, LA; Lousiana State University Healthe Science Center, Shreveport, LA

Background: Glucosylceramide synthase (GCS) is pivotal enzyme in ceramide metabolism and ceramide induced-apoptosis pathway. This enzyme catalyzes the transfer of ceramide into glucosylceramide, a key step in glycosphingolipid biosynthesis and is associated with reduced signaling of apoptosis. GCS has recently been implicated in the cytotoxic response of cancer cells to chemotherapy. Our previous works and those of others indicated that GCS confers drug resistance via defecting ceramide induced-apoptosis pathway by disrupting drug uptake in cancer cells. This study evaluates the effects of GCS expression on reversal of drug resistance.
Design: Antisense oligonucleotides were synthesized to target human GCS gene expression. The expression and knockdown of GCS gene were assessed by quantitative PCR, Western blot and ceramide glycosylation assay. The influences of antisense oligonucleotides on GCS expression and on chemosensitivity were examined in drug-resistant cell lines (MCF-7-AdrR, and EMT6/AR1) and in tumor-bearing mice. The effects of overexpression GCS gene, cell response to chemotherapy agent and treatment sensitivity were evaluated in these animal models. Microarray analysis of chemo-sensitized gene expression was performed using Affymetrix Human Genome U133 Plus 2.0.
Results: Suppression of GCS overexpression by treatment of antisense oligonucleotide sensitized all drug-resistant cancer cell lines to doxorubicin in vitro. Knockdown GCS by antisense gene transfection significantly inhibited tumor growth from the inoculation of drug-resistant cancer cells (MCF-7-AdrR) in vivo.

The treatment of antisense oligonucleotide (mixed backbone, methyl-RNA-DNA) suppressed tumor growth to 30% as compared with scrambled control groups and sensitized doxorubicin efficacy by 3-fold in orthotopic breast tumor models.
Conclusions: The present study demonstrated glucosylceramide synthase (GCS) is a potential novel target for drug-resistance reversal and suppressing the overexpression of GCS might be an effective approach to improve cancer chemotherapy.
Category: Special Category for 2009 - Pan-genomic/Pan-proteomic approaches to Cancer

Tuesday, March 10, 2009 9:30 AM

Poster Session III # 243, Tuesday Morning