title: Overexpression of glucosylceramide synthase and P-glycoprotein in cancer cells selected for resistance to natural product chemotherapy.
abstract: Resistance to natural product chemotherapy drugs is a major obstacle to successful cancer treatment. This type of resistance is often acquired in response to drug exposure; however, the mechanisms of this adverse reaction are complex and elusive. Here, we have studied acquired resistance to Adriamycin, Vinca alkaloids, and etoposide in MCF-7 breast cancer cells, KB-3-1 epidermoid carcinoma cells, and other cancer cell lines to determine if there is an association between expression of glucosylceramide synthase, the enzyme catalyzing ceramide glycosylation to glucosylceramide, and the multidrug-resistant (MDR) phenotype. This work shows that glucosylceramide levels increase concomitantly with increased drug resistance in the KB-3-1 vinblastine-resistant sublines KB-V.01, KB-V.1, and KB-V1 (listed in order of increasing MDR). The levels of glucosylceramide synthase mRNA, glucosylceramide synthase protein, and P-glycoprotein (P-gp) also increased in parallel. Increased glucosylceramide levels were also present in Adriamycin-resistant KB-3-1 sublines KB-A.05 and KB-A1. In breast cancer, detailed analysis of MCF-7 wild-type and MCF-7-AdrR cells (Adriamycin-resistant) demonstrated enhanced glucosylceramide synthase message and protein, P-gp message and protein, and high levels of glucosylceramide in resistant cells. Similar results were seen in vincristine-resistant leukemia, etoposide-resistant melanoma, and Adriamycin-resistant colon cancer cell lines. Cell-free glucosylceramide synthase activity was higher in lysates obtained from drug-resistant cells. Lastly, glucosylceramide synthase promoter activity was 15-fold higher in MCF-7-AdrR compared with MCF-7 cells. We conclude that selection pressure for resistance to natural product chemotherapy drugs selects for enhanced ceramide metabolism through glucosylceramide synthase in addition to enhanced P-gp expression. A possible connection between glucosylceramide synthase and P-gp in drug resistance biology is suggested.
authors.affiliation: John Wayne Cancer Institute at Saint John's Health Center, Santa Monica, California 90404, USA.
authors.forename: Valerie
authors.initials: V
authors.lastname: Gouazé
authors.forename: Jing Y
authors.initials: JY
authors.lastname: Yu
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Bleicher
authors.forename: Tie-Yan
authors.initials: TY
authors.lastname: Han
authors.forename: Yong-Yu
authors.initials: YY
authors.lastname: Liu
authors.forename: Hongtao
authors.initials: H
authors.lastname: Wang
authors.forename: Michael M
authors.initials: MM
authors.lastname: Gottesman
authors.forename: Arie
authors.initials: A
authors.lastname: Bitterman
authors.forename: Armando E
authors.initials: AE
authors.lastname: Giuliano
authors.forename: Myles C
authors.initials: MC
authors.lastname: Cabot
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics / Q000378:metabolism*; D001685:Biological Factors / Q000494:pharmacology* / Q000627:therapeutic use; D045744:Cell Line, Tumor; D004317:Doxorubicin / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm / Q000502:physiology*; D005047:Etoposide / Q000494:pharmacology; D005963:Glucosylceramides / Q000378:metabolism; D005964:Glucosyltransferases / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D014747:Vinblastine / Q000494:pharmacology
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D001685:Biological Factors; D005963:Glucosylceramides; D012333:RNA, Messenger; D014747:Vinblastine; D005047:Etoposide; D004317:Doxorubicin; D005964:Glucosyltransferases; C023246:ceramide glucosyltransferase