title: Possible role of ceramide as an indicator of chemoresistance: decrease of the ceramide content via activation of glucosylceramide synthase and sphingomyelin synthase in chemoresistant leukemia.
abstract: We investigated the possibility of the proapoptotic lipid ceramide as an indicator of chemoresistance in leukemia. Doxorubicin (DOX) increased the ceramide level and apoptosis in drug-sensitive HL-60 cells but not in drug-resistant HL-60/ADR cells, under the condition that the uptake of DOX was not different between the two cell lines. In addition, exogenous N-acetylsphingosine (C2-ceramide) enhanced DOX-induced apoptosis in HL-60/ADR cells without affecting the expression of multidrug resistant-1 protein (MDR 1) and the uptake of DOX. A lower level of ceramide with higher activities of glucosylceramide synthase (GCS) and sphingomyelin synthase (SMS) was detected in HL-60/ADR cells than in HL-60 cells. In contrast, HL-60/GCS cells, overexpressing GCS, significantly inhibited DOX-induced ceramide increase and apoptosis. These observations suggest the involvement of ceramide regulation in drug resistance of leukemia cells. In vivo, the level of ceramide was lower in chemoresistant leukemia patients (6.4 +/- 1.8 pmol/nmol phosphate; n = 14) than in chemosensitive patients (9.5 +/- 2.7 pmol/nmol phosphate; n = 9), and the activities of GCS and SMS were more than 2-fold higher in chemoresistant leukemia cells than in chemosensitive cells. MDR-1 protein was faintly expressed in one of four chemoresistant patients, but Bcl-2 were clearly detected in four patients. Therefore, it is suggested that a decrease of the ceramide level via activation of GCS and SMS is associated with the chemoresistant condition in leukemia, probably in relation to Bcl-2 but not to MDR-1 expression.
authors.affiliation: Department of Hematology and Oncology, Graduate School of Medicine, Kyoto University, Kyoto 606-8507, Japan.
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Itoh
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Kitano
authors.forename: Mitsumasa
authors.initials: M
authors.lastname: Watanabe
authors.forename: Tadakazu
authors.initials: T
authors.lastname: Kondo
authors.forename: Takeshi
authors.initials: T
authors.lastname: Yabu
authors.forename: Yoshimitu
authors.initials: Y
authors.lastname: Taguchi
authors.forename: Kazuya
authors.initials: K
authors.lastname: Iwai
authors.forename: Masaro
authors.initials: M
authors.lastname: Tashima
authors.forename: Takashi
authors.initials: T
authors.lastname: Uchiyama
authors.forename: Toshiro
authors.initials: T
authors.lastname: Okazaki
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D017209:Apoptosis; D002460:Cell Line; D002469:Cell Separation; D002518:Ceramides / Q000378:metabolism / Q000494:pharmacology*; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004318:Doxycycline / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm; D004789:Enzyme Activation; D005434:Flow Cytometry; D005964:Glucosyltransferases / Q000378:metabolism*; D018922:HL-60 Cells; D006801:Humans; D007938:Leukemia / Q000188:drug therapy; D008875:Middle Aged; D009369:Neoplasms / Q000188:drug therapy; D011419:Propidium / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D014162:Transfection; D017855:Transferases (Other Substituted Phosphate Groups) / Q000378:metabolism*
chemical_list: D002518:Ceramides; D018076:DNA, Complementary; C064769:N-acetylsphingosine; D012333:RNA, Messenger; D011419:Propidium; D005964:Glucosyltransferases; C023246:ceramide glucosyltransferase; D017855:Transferases (Other Substituted Phosphate Groups); C070186:phosphatidylcholine-ceramide phosphocholine transferase; D004318:Doxycycline; D013110:Sphingosine