title: Heterogeneity of molecular targets on clonal cancer lines derived from a novel hormone-refractory prostate cancer tumor system.
abstract: OBJECTIVE
  We recently described a new hormone refractory prostate cancer cell line, CL1, derived from LNCaP via in vitro androgen deprivation. To study gene expression during prostate cancer progression and to identify molecular targets for therapy, a pure clonal tumor system was generated.
  
  
  METHODS
  Limiting dilution of CL1 stably transfected with a green fluorescent protein, generated 35 single-cell clones, which were expanded into stable cell lines. In vitro responses to various therapeutic modalities were assessed in each clone. Gene expression was determined using reverse transcriptase-polymerase chain reaction and oligonucleotide microarrays. In vivo biology was assessed following orthotopic injection into intact and castrated severe combined immunodeficient mice.
  
  
  RESULTS
  In vitro, all clones demonstrated similar resistance to traditional therapeutic efforts including chemotherapy and radiation therapy, but differential sensitivity to cell-mediated cytotoxicity. The clones demonstrated differential gene expression relative to each other and to the parental CL1 and LNCaP cell lines. Following orthotopic injection into mice, three distinct growth patterns were observed: fast growth with widespread metastasis; slower grower with widespread metastasis; and no tumor formation. Using oligonucleotide microarrays, several genes were identified as differentially expressed between the most aggressive and the nontumorigenic clone.
  
  
  CONCLUSIONS
  We have described a novel fluorescent-labeled clonal hormone refractory prostate cancer tumor system that exhibited marked heterogeneity in its response to various therapeutic modalities, gene expression, and in vivo biology. Our data suggests that given the marked clonal heterogeneity, multi-modality approaches directed against multiple molecular targets rather than single agent therapy will be necessary to adequately eradicate the entire malignant cell population. Clonal tumor lines may allow more accurate examination of molecular pathways involved in tumor progression and resistance to treatment.
authors.affiliation: Department of Urology, UCLA, Los Angeles, California 90095-1738, USA.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Freedland
authors.forename: Allan J
authors.initials: AJ
authors.lastname: Pantuck
authors.forename: Sun H
authors.initials: SH
authors.lastname: Paik
authors.forename: Amnon
authors.initials: A
authors.lastname: Zisman
authors.forename: Thomas G
authors.initials: TG
authors.lastname: Graeber
authors.forename: David
authors.initials: D
authors.lastname: Eisenberg
authors.forename: William H
authors.initials: WH
authors.lastname: McBride
authors.forename: David
authors.initials: D
authors.lastname: Nguyen
authors.forename: Cho-Lea
authors.initials: CL
authors.lastname: Tso
authors.forename: Arie S
authors.initials: AS
authors.lastname: Belldegrun
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D002999:Clone Cells; D015972:Gene Expression Regulation, Neoplastic; D049452:Green Fluorescent Proteins; D006651:Histocytochemistry; D006801:Humans; D008164:Luminescent Proteins / Q000096:biosynthesis / Q000235:genetics; D008297:Male; D051379:Mice; D016513:Mice, SCID; D009376:Neoplasms, Hormone-Dependent / Q000188:drug therapy / Q000235:genetics / Q000473:pathology; D020411:Oligonucleotide Array Sequence Analysis; D011471:Prostatic Neoplasms / Q000188:drug therapy* / Q000235:genetics* / Q000473:pathology; D012334:RNA, Neoplasm / Q000737:chemistry / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection; D014407:Tumor Cells, Cultured; D023041:Xenograft Model Antitumor Assays
chemical_list: D000970:Antineoplastic Agents; D008164:Luminescent Proteins; D012334:RNA, Neoplasm; D049452:Green Fluorescent Proteins