Rationale behind using valproic acid for Non-Hodgkin lymphoma: a biomolecular perspective.

OBJECTIVE: Non-Hodgkin lymphoma (NHL) is a hematological malignancy with a high rate of relapse and refractory cases. It is believed to be caused by resistance to standard treatment modalities. Valproic acid (VPA), previously used as a broad-spectrum anticonvulsant drug, has been proposed for NHL owing to its action of epigenetic modification by inhibiting histone deacetylase. However, VPA studies on NHL are limited. This review describes the rationale behind the use of VPA for NHL treatment, particularly focusing on its molecular mechanism of action. MATERIALS AND METHODS: This is a narrative review. The literature search strategy for indexed Scopus articles was performed randomly using PubMed and MEDLINE as the primary sources. No specific term was used. RESULTS: Several mechanisms are responsible for NHL development. VPA can modulate these mechanisms via epigenetic and nonepigenetic modifications. It may also have an impact on the proteins responsible for treatment resistance. The mechanisms of action of VPA in NHL are as follows: the induction of cell cycle arrest via the upregulation of cyclin-dependent protein kinase inhibitors; induction of Apo2 ligand or tumor necrosis factor-related apoptosis-inducing ligand-induced apoptosis; inactivation of B-cell lymphoma 6; inhibition of Janus kinase/signal transducer and activator of transcription, phosphoinositide 3-kinase/Akt, and nuclear factor kappa B signaling pathways; upregulation of tumor antigen as the primary target of immunotherapy; and strengthening of tumor immunosurveillance. CONCLUSIONS: Based on its biomolecular mechanism of action, VPA appears to be a promising initial treatment before initiating the standard treatment in patients with NHL to overcome resistance.

The AP-1 transcription factor JunB is essential for multiple myeloma cell proliferation and drug resistance in the bone marrow microenvironment.

Despite therapeutic advances, multiple myeloma (MM) remains an incurable disease, predominantly because of the development of drug resistance. The activator protein-1 (AP-1) transcription factor family has been implicated in a multitude of physiologic processes and tumorigenesis; however, its role in MM is largely unknown. Here we demonstrate specific and rapid induction of the AP-1 family member JunB in MM cells when co-cultured with bone marrow stromal cells. Supporting a functional key role of JunB in MM pathogenesis, knockdown of JUNB significantly inhibited in vitro MM cell proliferation and survival. Consistently, induced silencing of JUNB markedly decreased tumor growth in a murine MM model of the microenvironment. Subsequent gene expression profiling revealed a role for genes associated with apoptosis, DNA replication and metabolism in driving the JunB-mediated phenotype in MM cells. Importantly, knockdown of JUNB restored the response to dexamethasone in dexamethasone-resistant MM cells. Moreover, 4-hydroxytamoxifen-induced activation of a JunB-ER fusion protein protected dexamethasone-sensitive MM cells against dexamethasone- and bortezomib-induced cytotoxicity. In summary, our results demonstrate for the first time a specific role for AP-1/JunB in MM cell proliferation, survival and drug resistance, thereby strongly supporting that this transcription factor is a promising new therapeutic target in MM.