ABSTRACT
PURPOSE: We have synthesized a series of hybrid polar compounds that induce differentiation and/or apoptosis of various transformed cells. These agents are also potent inhibitors of histone deacetylases (HDACs). Pyroxamide (suberoyl-3-aminopyridineamide hydroxamic acid) is a new member of this class of compounds that is currently under development as an anticancer agent. We investigated the activity of pyroxamide as an inducer of differentiation and/or apoptosis in transformed cells. EXPERIMENTAL DESIGN AND RESULTS: Pyroxamide, at micromolar concentrations, induced terminal differentiation in murine erythroleukemia (MEL) cells and caused growth inhibition by cell cycle arrest and/or apoptosis in MEL, prostate carcinoma, bladder carcinoma, and neuroblastoma cells. Administration of pyroxamide (100 or 200 mg/kg/day) to nude mice at doses that caused little evident toxicity significantly suppressed the growth of s.c. CWR22 prostate cancer xenografts. Despite the potent growth-inhibitory effects of pyroxamide in this tumor model, serum prostate-specific antigen levels in control versus pyroxamide-treated mice were not significantly different. Pyroxamide is a potent inhibitor of affinity-purified HDAC1 (ID(50) = 100 nM) and causes the accumulation of acetylated core histones in MEL cells cultured with the agent. Human CWR22 prostate tumor xenografts from mice treated with pyroxamide (100 or 200 mg/kg/day) showed increased levels of histone acetylation and increased expression of the cell cycle regulator p21/WAF1, compared with tumors from vehicle-treated control animals. CONCLUSIONS: The findings suggest that pyroxamide may be a useful agent for the treatment of malignancy and that induction of p21/WAF1 in transformed cells by pyroxamide may contribute to the antitumor effects of this agent.
Subject(s)
Aminopyridines/pharmacology , Antineoplastic Agents/pharmacology , Cell Differentiation/drug effects , Enzyme Inhibitors/pharmacology , Histone Deacetylase Inhibitors , Hydroxamic Acids/pharmacology , Acetylation/drug effects , Aminopyridines/therapeutic use , Animals , Antineoplastic Agents/therapeutic use , Cell Division/drug effects , Cell Line, Transformed , Cyclin-Dependent Kinase Inhibitor p21 , Cyclins/biosynthesis , Disease Models, Animal , Enzyme Inhibitors/therapeutic use , Histone Deacetylases/metabolism , Histones/metabolism , Humans , Hydroxamic Acids/therapeutic use , Male , Mice , Mice, Inbred BALB C , Mice, Nude , Prostate-Specific Antigen/blood , Prostatic Neoplasms/blood , Prostatic Neoplasms/drug therapy , Treatment Outcome , Tumor Cells, Cultured , Xenograft Model Antitumor AssaysABSTRACT
Histone deacetylase inhibitors (HDACIs) inhibit the growth of a variety of transformed cells in culture. We demonstrated previously that the hybrid-polar HDACI m-carboxycinnamic acid bis-hydroxamide (CBHA) induces apoptosis of human neuroblastoma in vitro and is effective in lower doses when combined with retinoids. The current study investigates the effect of CBHA on the growth of human neuroblastoma in vivo, both alone and in combination with all-trans retinoic acid (atRA), using a severe combined immunodeficiency-mouse xenograft model. CBHA (50, 100, and 200 mg/kg/day) inhibited growth of SMS-KCN-69n tumor xenografts in a dose-dependent fashion, with 200 mg/kg CBHA resulting in a complete suppression of tumor growth. The efficacy of 50 and 100 mg/kg CBHA was enhanced by the addition of 2.5 mg/kg atRA. This dose of atRA was ineffective when administered alone. Treatment was accompanied by mild weight loss in all groups except the lowest dose of CBHA. Our results suggest HDACIs alone or combined with retinoids may have therapeutic utility for neuroblastoma.
Subject(s)
Antineoplastic Combined Chemotherapy Protocols/pharmacology , Cinnamates/pharmacology , Enzyme Inhibitors/pharmacology , Neuroblastoma/drug therapy , Tretinoin/pharmacology , Acetylation , Animals , Antineoplastic Agents/pharmacology , Antineoplastic Agents/toxicity , Antineoplastic Combined Chemotherapy Protocols/toxicity , Cell Division/drug effects , Cinnamates/administration & dosage , Cinnamates/toxicity , Dose-Response Relationship, Drug , Drug Synergism , Enzyme Inhibitors/toxicity , Female , Growth Inhibitors/pharmacology , Histone Deacetylase Inhibitors , Histones/metabolism , Humans , Mice , Mice, SCID , Neuroblastoma/enzymology , Neuroblastoma/pathology , Tretinoin/administration & dosage , Tumor Cells, Cultured , Weight Loss/drug effects , Xenograft Model Antitumor AssaysABSTRACT
BACKGROUND: Neuroblastoma is a common childhood cancer with a poor overall prognosis. Retinoic acids (RAs) have been studied as a potential therapy, showing promise in recurrent disease. The histone deacetylase inhibitor (HDACI) M-carboxycinnamic acid bishydroxamide (CBHA) is another potential therapy, which we recently described. Combinations of RAs and HDACIs currently under investigation display synergy in certain neoplasms. In this study, we evaluate the effect of combinations of RAs and HDACIs on human neuroblastoma cells. PROCEDURE: Established cell lines were cultured in increasing concentrations of HDACIs, RAs, and combinations thereof. Following exposure, viable cell number was quantified by trypan blue dye exclusion on a hemacytometer. Cell cycle analysis was performed by propidium iodide staining and FACS. RESULTS: All assayed HDACIs and RAs decreased viable cell number. Lower concentrations of each agent were effective when the two were combined. The primary reason for decreased cell number appears to be apoptosis following HDACI exposure and G1 arrest following RA exposure. Both effects are seen with cotreatment. Caspase inhibition abrogates the apoptotic response. CONCLUSIONS: CBHA causes apoptosis of human neuroblastoma in vitro, an effect that can add to the effects of RA. HDACIs and RAs inhibit neuroblastoma in significantly lower concentrations when used together than when used individually. Combination therapy may improve the ultimate efficacy while reducing the side effects of these agents in clinical use.
