IMP dehydrogenase inhibitor mycophenolate mofetil induces caspase-dependent apoptosis and cell cycle inhibition in multiple myeloma cells

Abstract

Multiple myeloma is an incurable disease for the majority of patients, therefore requiring new biological targeted therapies. In primary myeloma cells, IMP dehydrogenase (IMPDH) was shown to be consistently overexpressed. We therefore tested the IMPDH inhibitor mycophenolate mofetil (MMF) currently available as a clinical therapeutic agent for its antimyeloma activity in vitro. MMF depleted intracellular guanosine 5V -triphosphate (GTP) levels in myeloma cells. We showed apoptosis induction in myeloma cell lines and primary myeloma cells between 1 and 5 Mmol/L MMF. MMF was also cytotoxic at this concentration in dexamethasone-resistant and Mcl-1-overexpressed myeloma cell lines shown by the tetrazolium salt XTT assay along with cell survival measured by a modified flow cytometric assay. Apoptosis was not inhibited by the presence of an antioxidant, suggesting that MMF-induced apoptosis is less likely to be associated with reactive oxygen species. However, apoptosis was abrogated by exogenously added guanosine, which activates an alternative pathway for GTP formation, implicating that this effect is directly mediated by IMPDH inhibition. MMF-induced G 1 -S phase cell cycle arrest and its apoptosis induction mechanism were associated with a caspase-dependent pathway as shown by alteration of mitochondrial membrane potential and cytochrome c release followed by activation of the caspases. MMF-induced apoptosis was also inhibited by a pan-caspase inhibitor Z-VAD-fmk. MMF-treated myeloma cells showed an up-regulation of Bak, which most likely together with Bax resulted in the release of cytochrome c. In summary, MMF attenuates G 1 -S phase cell cycle progression and activates the pathway of mitochondrial dysfunction, leading to cytochrome c release followed by activation of caspases. [Mol Cancer Ther 2006;5(2): 457-66]

Hydroxamic Acid Derivatives of Mycophenolic Acid Inhibit Histone Deacetylase at the Cellular Level

“…After 10 h of stirring, the reaction mixture was evaporated, washed with 2 M HCl, dried over Na 2 SO 4 and evaporated. The residue was purified by PTLC (CHCl 3 /EtOAc, 1/1) to give a white solid (21.7 mg, 90% (E)-6-(1,3-Dihydro-4-(2-methoxyethoxy)methoxy-6-hydroxy-7-methyl-3-oxo-5-isobenzofuranyl)-4-methyl-4-hexenohydroxamic acid (12). A solution of 5 M KOH in MeOH (2 ml) was added dropwise while stirring to a mixture containing compound 9 (46.4 mg, 0.11 mmol) dissolved in THF (1.5 ml) and hydroxylamine hydrochloride (61 mg, 0.88 mmol) dissolved in MeOH (2 ml).…”

“…[7][8][9][10] Due to its apoptotic properties, 1 has entered phase I clinical trials in advanced multiple myeloma patients. 11,12) Dynamic histone acetylation and deacetylation exhibit a critical regulatory function on gene expression through an effect on nucleosome conformation. 13) Interestingly, histone deacetylase (HDAC) inhibitors specifically induce the expression level of such anticancer genes as p21, TRAIL and FasL, DR5 and FAS in leukemia cells and not in normal cells.…”

The Immunosuppressor Mycophenolic Acid Kills Activated Lymphocytes by Inducing a Nonclassical Actin-Dependent Necrotic Signal

“…3). An increase in IMPDH activity has been reported in solid neoplastic cells or in leukemic cells (4,5), and the administration of IMPDH inhibitors protects patients from developing tumors (6,7) by a yet undefined mechanism that may involve modulation of cell death (8,9). Despite Ͼ3,000 publications investigating the functional and the molecular effects of MPA on cells, its cytotoxic action remains poorly defined.…”

Prognostic significance of drug-regulated genes in high-grade osteosarcoma

“…In multiple myeloma cells inhibition of IMPDH has been shown to induce caspase-dependent apoptosis and cell-cycle arrest. 26 Further, increased IMPDH mRNA levels have been detected in methotrexate (MTX)-treated and MTXresistant human colon cancer and erythroleukemia cells. The authors suggested that the increased IMPDH expression might be interpreted as a compensation for the inhibition of dihydrofolate reductase by MTX.…”