title: Down-regulation of ATM protein sensitizes human prostate cancer cells to radiation-induced apoptosis.
abstract: Treatment with the protein kinase C activator 12-O-tetradecanoylphorbol 12-acetate (TPA) enables radiation-resistant LNCaP human prostate cancer cells to undergo radiation-induced apoptosis, mediated via activation of the enzyme ceramide synthase (CS) and de novo synthesis of the sphingolipid ceramide (Garzotto, M., Haimovitz-Friedman, A., Liao, W. C., White-Jones, M., Huryk, R., Heston, D. W. W., Cardon-Cardo, C., Kolesnick, R., and Fuks, Z. (1999) Cancer Res. 59, 5194-5201). Here, we show that TPA functions to decrease the cellular level of the ATM (ataxia telangiectasia mutated) protein, known to repress CS activation (Liao, W.-C., Haimovitz-Friedman, A., Persaud, R., McLoughlin, M., Ehleiter, D., Zhang, N., Gatei, M., Lavin, M., Kolesnick, R., and Fuks, Z. (1999) J. Biol. Chem. 274, 17908-17917). Gel shift analysis in LNCaP and CWR22-Rv1 cells demonstrated a significant reduction in DNA binding of the Sp1 transcription factor to the ATM promoter, and quantitative reverse transcription-PCR showed a 50% reduction of ATM mRNA between 8 and 16 h of TPA treatment, indicating that TPA inhibits ATM transcription. Furthermore, treatment of LNCaP, CWR22-Rv1, PC-3, and DU-145 human prostate cells with antisense-ATM oligonucleotides, which markedly reduced cellular ATM levels, significantly enhanced radiation-induced CS activation and apoptosis, leading to apoptosis at doses as a low as 1 gray. These data suggest that the CS pathway initiates a generic mode of radiation-induced apoptosis in human prostate cancer cells, regulated by a suppressive function of ATM, and that ATM might represent a potential target for pharmacologic inactivation with potential clinical applications in human prostate cancer.
authors.affiliation: Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA.
authors.forename: Jean-Philip
authors.initials: JP
authors.lastname: Truman
authors.forename: Nuri
authors.initials: N
authors.lastname: Gueven
authors.forename: Martin
authors.initials: M
authors.lastname: Lavin
authors.forename: Steven
authors.initials: S
authors.lastname: Leibel
authors.forename: Richard
authors.initials: R
authors.lastname: Kolesnick
authors.forename: Zvi
authors.initials: Z
authors.lastname: Fuks
authors.forename: Adriana
authors.initials: A
authors.lastname: Haimovitz-Friedman
mesh_terms: D017209:Apoptosis; D064007:Ataxia Telangiectasia Mutated Proteins; D015153:Blotting, Western; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000378:metabolism*; D016923:Cell Death; D045744:Cell Line, Tumor; D002469:Cell Separation; D002518:Ceramides / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D015536:Down-Regulation; D005434:Flow Cytometry; D006801:Humans; D007700:Kinetics; D008297:Male; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D010088:Oxidoreductases / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011471:Prostatic Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000532:radiotherapy*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016329:Sp1 Transcription Factor / Q000378:metabolism; D013997:Time Factors; D014162:Transfection; D025521:Tumor Suppressor Proteins / Q000378:metabolism*
chemical_list: D018797:Cell Cycle Proteins; D002518:Ceramides; D004268:DNA-Binding Proteins; D016376:Oligonucleotides, Antisense; D012333:RNA, Messenger; D011838:Radiation-Sensitizing Agents; D016329:Sp1 Transcription Factor; D025521:Tumor Suppressor Proteins; D010088:Oxidoreductases; C108138:dihydroceramide desaturase; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases