title: Phenylbutyrate-induced G1 arrest and apoptosis in myeloid leukemia cells: structure-function analysis.
abstract: The aromatic fatty acid phenylbutyrate (PB) induces cytostasis, differentiation, and apoptosis in primary myeloid leukemic cells at clinically achievable concentrations. In the present study, we have investigated the structural and cellular basis for PB-induced cytostasis, using the ML-1 human myeloid leukemia cell line as a model system. PB induced a dose-dependent increase in cells in G1 with a corresponding decrease in cells in S-phase of the cell cycle. At comparable doses, PB induced expression of CD11b, indicating myeloid differentiation. At higher doses, the drug induced apoptosis. The antitumor activity was independent of the aromatic ring, as butyric acid (BA) was of equal or greater potency at producing these biological changes. In contrast, shortening of the fatty acid carbon chain length, as demonstrated with phenylacetate (PA), significantly diminished drug potency. Consistent with their effects on cell cycle, PB and BA, but not PA, induced the cyclin-dependent kinase inhibitor, p21(WAF1/CIP1), and led to the appearance of hypophosphorylated Rb, suggesting a role for p21(WAF1/CIP1) in PB-induced cytostasis. Therefore, it appears that the fatty acid moiety of PB, rather than its aromatic ring, is critical for its activity in myeloid leukemic cells. These data provide a potential mechanistic basis for the increased potency of PB over PA previously demonstrated in primary leukemic samples, and support the further clinical development of PB in the treatment of hematologic malignancies.
authors.affiliation: Department of Oncology, The Johns Hopkins Medical Institutions, Baltimore, MD, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: DiGiuseppe
authors.forename: L J
authors.initials: LJ
authors.lastname: Weng
authors.forename: K H
authors.initials: KH
authors.lastname: Yu
authors.forename: S
authors.initials: S
authors.lastname: Fu
authors.forename: M B
authors.initials: MB
authors.lastname: Kastan
authors.forename: D
authors.initials: D
authors.lastname: Samid
authors.forename: S D
authors.initials: SD
authors.lastname: Gore
mesh_terms: D000970:Antineoplastic Agents / Q000737:chemistry / Q000494:pharmacology* / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects*; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D016193:G1 Phase / Q000187:drug effects*; D006801:Humans; D007951:Leukemia, Myeloid / Q000188:drug therapy* / Q000473:pathology*; D010654:Phenylbutyrates / Q000737:chemistry / Q000494:pharmacology* / Q000627:therapeutic use; D013329:Structure-Activity Relationship; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D010654:Phenylbutyrates