Epigenetic changes have been implicated in silencing several B-cell genes in Hodgkin and Reed-Sternberg cells (HRS) of Hodgkin lymphoma (HL), and this mechanism has been proposed to promote HRS survival and escape from immunosurveillance. However, the molecular and functional consequences of histone deacetylase (HDAC) inhibition in HL have not been previously described. In this study, we report that the HDAC inhibitor vorinostat induced p21 expression and decreased Bcl-xL levels causing cellcycle arrest and apoptosis. Furthermore, vorinostat inhibited STAT6 phosphorylation and decreased its mRNA levels in a dose-and time-dependent manner, which was associated with a decrease in the expression and secretion of Thymus and Activation-Regulated Chemokine (TARC/ CCL17) and interleukin (IL)-5 and an increase in IP-10 levels. Moreover, vorinostat inhibited TARC secretion by dendritic cells that were activated by the thymic stromal lymphopoietin (TSLP). Collectively, these data suggest that pharmacologic HDAC inhibition in HL may induce favorable antitumor activity by a direct antiproliferative effect on HRS cells, and possibly by an immune mediated effect by altering cytokine and chemokines secretion in the microenvironment. (Blood.

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BACKGROUND The prognosis of patients with relapsed Hodgkin lymphoma, especially those who relapsed after stem cell transplant, remains poor, and the development of new agents for this relatively young patient population represents an unmet medical need. In this study, we examined the safety and efficacy of mocetinostat, an oral isotype-selective histone deacetylase inhibitor, in patients with relapsed classical Hodgkin lymphoma METHODS Patients with relapsed or refractory classical Hodgkin lymphoma aged 18 years or older were treated with mocetinostat administered as an oral dose three-times weekly, in 28-day cycles. Two dose cohorts were evaluated (85 mg and 110 mg). Patients were treated until disease progression or prohibitive toxicity. The primary objective was to estimate the disease control rate induced by mocetinostat, defined as CR, PR or SD (for at least 6 cycles) analysed by intention to treat. This trial has been completed and is registered with ClinicalTrials.gov, number NCT00358982 FINDINGS A total of 51 patients were enrolled. Initially, 23 patients were enrolled in the 110 mg cohort. Subsequently, 28 additional patients were treated with a reduced dose of 85 mg to improve treatment tolerance. Based on intent to treat analysis, the overall disease control rate was 34.8% and 25% for the 110 mg and 85 mg groups, respectively. Thirty-four out of 42 (81%) patients who completed at least 2 cycles of therapy had a decrease in their tumor measurements. Forty-seven percent (24/51) discontinued therapy due to disease progression, 57% (16/28) in the 85 mg cohort and 34% in the 110 mg cohort. Twenty-four percent (12/51) discontinued due to adverse events, 32% (9/28) in the 85 mg cohort and 13% (3/23) in the 110 mg cohort. The most frequent treatment-related grade 3 and 4 adverse events included neutropenia, which was observed in 4 (17.4%) patients in the 110 mg group and in 3 (10.7%) patients in the 85 mg group; fatigue (in 5 (21.7%) of the 110 mg group vs 3 (10.7%) of the 85 mg group); and pneumonia (4 (17.4%) of the 110 mg group vs 2 (7.1% of the 85 mg group). Four patients, all in the 110 mg cohort, died during study, of whom two were considered possibly related to treatment. INTERPRETATION Mocetinostat 85 mg three-times weekly has promising single-agent clinical activity with manageable toxicity in patients with relapsed classical Hodgkin lymphoma. FUNDING MethylGene Inc., Montreal, Canada; Celgene Corporation, Summit, New Jersey; Tufts Medical Center, Boston, MA

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