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 PBinduced 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 cyclindependent 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.

Complementary effects of HDAC inhibitor 4-PB on gap junction communication and cellular export mechanisms support restoration of chemosensitivity of PDAC cells

“…Low proliferating primary human fibroblasts and PBMC were not effected by 4-PB in the concentrations tested. Partly in contrast to other studies reporting a cell cycle arrest of tumour cells upon 4-PB treatment (DiGiuseppe et al, 1999;Clarke et al, 2001), only half of the cell lines investigated by us showed an arrest of the cell cycle in the G1-phase. This divergence namely of the PDAC cells might be explained by significant differences in the transcriptome of these cell lines (Grutzmann et al, 2004).…”

“…This divergence namely of the PDAC cells might be explained by significant differences in the transcriptome of these cell lines (Grutzmann et al, 2004). It has been previously described that the cell cycle arrest in tumour cells upon 4-PB treatment depends on p21 (DiGiuseppe et al, 1999). Interestingly, according to a microarray-based study (Grutzmann et al, 2004), cells showing a cell cycle arrest in this study (T3M-4 and Colo357) express p21 to a higher extend than the nonarresting cells (Panc1 and BxPc3).…”

Histone deacetylase inhibitor selectively induces p21 WAF1 expression and gene-associated histone acetylation

“…The expression of the cell cycle kinase inhibitor p21 WAF1 is induced in transformed cells by HDAC inhibitors such as phenylbutyrate, trichostatin A, and SAHA (4,14,15). Increased expression of p21 WAF1 may play a critical role in the growth arrest induced in transformed cells by these agents.…”

Histone deacetylase inhibitor NVP-LAQ824 has significant activity against myeloid leukemia cells in vitro and in vivo

“…26 For some AML patient samples, we observed a slightly higher cell number at lower concentrations of NVP-LAQ824, suggesting that low concentrations of NVP-LAQ824 may sometimes increase cell proliferation. Previously, DiGiuseppe et al 71 published that low doses of phenylbutyrate (o1 mM) consistently led to a slight transient increase in S-phase cells on days 2-3 of incubation. The increase in S phase was o10%, but was not necessarily associated with increased cell number, which was not examined.…”