Stromal genes discriminate preinvasive from invasive disease, predict outcome, and highlight inflammatory pathways in digestive cancers.

The stromal compartment is increasingly recognized to play a role in cancer. However, its role in the transition from preinvasive to invasive disease is unknown. Most gastrointestinal tumors have clearly defined premalignant stages, and Barrett's esophagus (BE) is an ideal research model. Supervised clustering of gene expression profiles from microdissected stroma identified a gene signature that could distinguish between BE metaplasia, dysplasia, and esophageal adenocarcinoma (EAC). EAC patients overexpressing any of the five genes (TMEPAI, JMY, TSP1, FAPalpha, and BCL6) identified from this stromal signature had a significantly poorer outcome. Gene ontology analysis identified a strong inflammatory component in BE disease progression, and key pathways included cytokine-cytokine receptor interactions and TGF-beta. Increased protein levels of inflammatory-related genes significantly up-regulated in EAC compared with preinvasive stages were confirmed in the stroma of independent samples, and in vitro assays confirmed functional relevance of these genes. Gene set enrichment analysis of external datasets demonstrated that the stromal signature was also relevant in the preinvasive to invasive transition of the stomach, colon, and pancreas. These data implicate inflammatory pathways in the genesis of gastrointestinal tract cancers, which can affect prognosis.

A 4-gene signature predicts survival of patients with resected adenocarcinoma of the esophagus, junction, and gastric cardia.

BACKGROUND & AIMS: The incidence of esophageal and junctional adenocarcinoma has increased 6-fold in the past 30 years and 5-year survival remains approximately 20%. Current staging is limited in its ability to predict survival which has ramifications for treatment choices. The aim of this study was to generate and validate a molecular prognostic signature for esophageal adenocarcinoma. METHODS: Gene expression profiling was performed and the resulting 42,000 gene signatures correlated with clinical and pathologic features for 75 snap-frozen esophageal and junctional resection specimens. External validation of selected targets was performed on 371 independent cases using immunohistochemistry to maximize clinical applicability. RESULTS: A total of 119 genes were associated significantly with survival and 270 genes with the number of involved lymph nodes. Filtering of these lists resulted in a shortlist of 10 genes taken forward to validation. Four genes proved to be prognostic at the protein level (deoxycytidine kinase [DCK], 3'-phosphoadenosine 5'-phosphosulfate synthase 2 [PAPSS2], sirtuin 2 [SIRT2], and tripartite motif-containing 44 [TRIM44]) and were combined to create a molecular prognostic signature. This 4-gene signature was highly predictive of survival in the independent external validation cohort (0/4 genes dysregulated 5-year survival, 58%; 95% confidence interval [CI], 36%-80%; 1-2/4 genes dysregulated 5-year survival, 26%; 95% CI, 20%-32%; and 3-4/4 genes dysregulated 5-year survival, 14%; 95% CI, 4%-24% (P = .001). Furthermore, this 4-gene signature was independently prognostic in a multivariable model together with the existing clinical TNM staging system (P = .013). CONCLUSIONS: This study has generated a clinically applicable prognostic gene signature that independently predicts survival in an external validation cohort and may inform management decisions.

Preclinical Evaluation of 89Zr-Df-IAB22M2C PET as an Imaging Biomarker for the Development of the GUCY2C-CD3 Bispecific PF-07062119 as a T Cell Engaging Therapy.

PURPOSE: A sensitive and specific imaging biomarker to monitor immune activation and quantify pharmacodynamic responses would be useful for development of immunomodulating anti-cancer agents. PF-07062119 is a T cell engaging bispecific antibody that binds to CD3 and guanylyl cyclase C, a protein that is over-expressed by colorectal cancers. Here, we used 89Zr-Df-IAB22M2C (89Zr-Df-Crefmirlimab), a human CD8-specific minibody to monitor CD8+ T cell infiltration into tumors by positron emission tomography. We investigated the ability of 89Zr-Df-IAB22M2C to track anti-tumor activity induced by PF-07062119 in a human CRC adoptive transfer mouse model (with injected activated/expanded human T cells), as well as the correlation of tumor radiotracer uptake with CD8+ immunohistochemical staining. PROCEDURES: NOD SCID gamma mice bearing human CRC LS1034 tumors were treated with four different doses of PF-07062119, or a non-targeted CD3 BsAb control, and imaged with 89Zr-Df-IAB22M2C PET at days 4 and 9. Following PET/CT imaging, mice were euthanized and dissected for ex vivo distribution analysis of 89Zr-Df-IAB22M2C in tissues on days 4 and 9, with additional data collected on day 6 (supplementary). Data were analyzed and reported as standard uptake value and %ID/g for in vivo imaging and ex vivo tissue distribution. In addition, tumor tissues were evaluated by immunohistochemistry for CD8+ T cells. RESULTS: The results demonstrated substantial mean uptake of 89Zr-Df-IAB22M2C (%ID/g) in PF-07062119-treated tumors, with significant increases in comparison to non-targeted BsAb-treated controls, as well as PF-07062119 dose-dependent responses over time of treatment. A moderate correlation was observed between tumor tissue radioactivity uptake and CD8+ cell density, demonstrating the value of the imaging agent for non-invasive assessment of intra-tumoral CD8+ T cells and the mechanism of action for PF-07062119. CONCLUSION: Immune-imaging technologies for quantitative cellular measures would be a valuable biomarker in immunotherapeutic clinical development. We demonstrated a qualification of 89Zr-IAB22M2C PET to evaluate PD responses (mice) to a novel immunotherapeutic.

Aprepitant for the prevention of chemotherapy-induced nausea and vomiting associated with a broad range of moderately emetogenic chemotherapies and tumor types: a randomized, double-blind study.

PURPOSE: Aprepitant was shown previously to be effective for prevention of chemotherapy-induced nausea and vomiting (CINV) with moderately emetogenic chemotherapy (MEC) in breast cancer patients receiving an anthracycline and cyclophosphamide (AC)-based regimen. This study assessed aprepitant in patients receiving a broad range of MEC regimens with a variety of tumor types. METHODS: This phase III, randomized, gender-stratified, double-blind trial enrolled patients with confirmed malignancies, naïve to MEC or highly emetogenic chemotherapy, who were scheduled to receive a single dose of at least one MEC agent. Patients received an aprepitant triple-therapy regimen (aprepitant, ondansetron, and dexamethasone) or a control regimen (ondansetron and dexamethasone) administered orally. Primary and key secondary efficacy endpoints were proportions of patients with no vomiting and complete response (no vomiting and no rescue medication), respectively, during the 120 h post-chemotherapy. RESULTS: Of 848 randomized patients, 77% were female, and 52% received non-AC-based antineoplastic regimens. Significantly, more patients in the aprepitant group achieved no vomiting and complete response, regardless of whether they received AC or non-AC regimens, in the 120 h after chemotherapy. Overall, the incidences of adverse events were generally similar in the aprepitant (62.8%) and control groups (67.2%). CONCLUSIONS: The aprepitant regimen provided superior efficacy in the treatment of CINV in a broad range of patients receiving MEC (non-AC or AC) in both no vomiting and complete response endpoints. Aprepitant was generally well tolerated. These results show the benefit of including aprepitant as part of the standard antiemetic regimen for cancer patients receiving MEC.

Phase I and pharmacokinetic study of vorinostat (suberoylanilide hydroxamic acid) in Japanese patients with solid tumors.

Vorinostat (suberoylanilide hydroxamic acid), a potent, oral histone deacetylase inhibitor, has demonstrated clinical activity in non-Japanese patients with various hematological and solid tumors. We sought to determine the maximum tolerated dose and a recommended phase II dose for 18 Japanese patients with solid tumors (median age, 58 years; range, 25-72 years) who failed standard therapy. Patients received vorinostat for 14 days followed by a 7-day rest. The initial dose was 100 mg twice daily escalating by 100 mg twice daily. Once-daily dosing was tested at 400 and 500 mg. A maximum tolerated dose could not be identified. Dose-limiting toxicities (thrombocytopenia, anorexia, and fatigue) were observed in two of six patients receiving 200 mg twice daily and in one of six patients receiving 500 mg once daily. In the 100-500 mg dose range, vorinostat area under the concentration-time curve increased in proportion to dose with a pharmacokinetic profile similar to that established in non-Japanese patients. Vorinostat doses of 200 mg twice daily or 500 mg once daily for 14 days followed by a 7-day rest were well tolerated and are candidate doses for phase II trials, although a maximum tolerated dose for vorinostat was not reached.

Combining CDK4/6 inhibition with taxanes enhances anti-tumor efficacy by sustained impairment of pRB-E2F pathways in squamous cell lung cancer.

The CDK4/6 inhibitor palbociclib reduces tumor growth by decreasing retinoblastoma (RB) protein phosphorylation and inducing cell cycle arrest at the G1/S phase transition. Palbociclib in combination with anti-hormonal therapy brings significant benefit to breast cancer patients. In this study, novel combination approaches and underlying molecular/cellular mechanisms for palbociclib were explored in squamous cell lung cancer (SqCLC), the second most common subtype of non-small cell lung cancer. While approximate 20% lung patients benefit from immunotherapy, most SqCLC patients who receive platinum-doublet chemotherapy as first-line treatment, which often includes a taxane, are still in need of more effective combination therapies. Our results demonstrated enhanced cytotoxicity and anti-tumor effect with palbociclib plus taxanes at clinically achievable doses in multiple SqCLC models with diverse cancer genetic backgrounds. Comprehensive gene expression analysis revealed a sustained disruption of pRB-E2F signaling by combination that was accompanied with enhanced regulation of pleiotropic biological effects. These included several novel mechanisms such as abrogation of G2/M and mitotic spindle assembly checkpoints, as well as impaired induction of hypoxia-inducible factor 1 alpha (HIF-1α). The decrease in HIF-1α modulated a couple key angiogenic and anti-angiogenic factors, resulting in an enhanced anti-angiogenic effect. This preclinical work suggests a new therapeutic opportunity for palbociclib in lung and other cancers currently treated with taxane based chemotherapy as standard of care.

Identification of biomarkers for tumor endothelial cell proliferation through gene expression profiling.

Extensive efforts are under way to identify antiangiogenic therapies for the treatment of human cancers. Many proposed therapeutics target vascular endothelial growth factor (VEGF) or the kinase insert domain receptor (KDR/VEGF receptor-2/FLK-1), the mitogenic VEGF receptor tyrosine kinase expressed by endothelial cells. Inhibition of KDR catalytic activity blocks tumor neoangiogenesis, reduces vascular permeability, and, in animal models, inhibits tumor growth and metastasis. Using a gene expression profiling strategy in rat tumor models, we identified a set of six genes that are selectively overexpressed in tumor endothelial cells relative to tumor cells and whose pattern of expression correlates with the rate of tumor endothelial cell proliferation. In addition to being potential targets for antiangiogenesis tumor therapy, the expression patterns of these genes or their protein products may aid the development of pharmacodynamic assays for small molecule inhibitors of the KDR kinase in human tumors.

Downregulation of MHC-I expression is prevalent but reversible in Merkel cell carcinoma.

Merkel cell carcinoma (MCC) is an aggressive, polyomavirus-associated skin cancer. Robust cellular immune responses are associated with excellent outcomes in patients with MCC, but these responses are typically absent. We determined the prevalence and reversibility of major histocompatibility complex class I (MHC-I) downregulation in MCC, a potentially reversible immune-evasion mechanism. Cell-surface MHC-I expression was assessed on five MCC cell lines using flow cytometry as well as immunohistochemistry on tissue microarrays representing 114 patients. Three additional patients were included who had received intralesional IFN treatment and had evaluable specimens before and after treatment. mRNA expression analysis of antigen presentation pathway genes from 35 MCC tumors was used to examine the mechanisms of downregulation. Of note, 84% of MCCs (total n = 114) showed reduced MHC-I expression as compared with surrounding tissues, and 51% had poor or undetectable MHC-I expression. Expression of MHC-I was lower in polyomavirus-positive MCCs than in polyomavirus-negative MCCs (P < 0.01). The MHC-I downregulation mechanism was multifactorial and did not depend solely on HLA gene expression. Treatment of MCC cell lines with ionizing radiation, etoposide, or IFN resulted in MHC-I upregulation, with IFNs strongly upregulating MHC-I expression in vitro, and in 3 of 3 patients treated with intralesional IFNs. MCC tumors may be amenable to immunotherapy, but downregulation of MHC-I is frequently present in these tumors, particularly those that are positive for polyomavirus. This downregulation is reversible with any of several clinically available treatments that may thus promote the effectiveness of immune-stimulating therapies for MCC.

Phase I trial of vorinostat combined with bortezomib for the treatment of relapsing and/or refractory multiple myeloma.

UNLABELLED: Preclinical studies have shown that targeted combination therapy consisting of vorinostat and bortezomib has antitumor activity in multiple myeloma (MM). We examined this drug combination in advanced relapsing and/or refractory MM patients (n = 34). Although the maximum tolerated dose was not reached, the study found this combination regimen generally well tolerated and clinically active in relapsed and/or refractory MM patients. BACKGROUND: Development of targeted therapies for MM has improved response rates and increased patient survival, but ultimately the disease becomes refractory and progresses. Vorinostat combined with bortezomib has demonstrated synergistic antiproliferative and proapoptotic activity in preclinical models of MM. The objectives of this study were to determine the maximum tolerated dose for vorinostat with bortezomib in patients with advanced MM and to evaluate the clinical benefit of this new drug combination. PATIENTS AND METHODS: Patients ≥ 18 years old with relapsed and/or refractory MM were enrolled into escalating dose cohorts of vorinostat and bortezomib combination therapy. Thirty-four patients were enrolled and were evaluable for safety and efficacy analyses. RESULTS: All patients reported adverse events, 89% of which were mild to moderate in severity. Thirteen patients experienced 29 serious adverse events, 12 (41%) of which were considered drug-related. The maximum tolerated dose was not reached. Partial responses were observed in 9 (27%) patients. Minimal responses were observed in 2 additional patients (6%), and another 20 patients (59%) experienced disease stabilization. CONCLUSION: Vorinostat with bortezomib is generally well-tolerated and has clinical activity in patients with relapsed and/or refractory MM. Response rates were similar in patients previously exposed to bortezomib and patients who were naive to bortezomib therapy.

Vorinostat combined with bexarotene for treatment of cutaneous T-cell lymphoma: in vitro and phase I clinical evidence supporting augmentation of retinoic acid receptor/retinoid X receptor activation by histone deacetylase inhibition.

The retinoid X receptor (RXR)-agonist bexarotene and the histone deacetylase inhibitor (HDACI) vorinostat are each established monotherapies for cutaneous T-cell lymphomas (CTCLs). We investigated the combination of HDACI and retinoic acid receptor (RAR)/RXR agonists in vitro and in a phase I, multicenter, open-label, two-part dose-escalation study. The combination of bexarotene with a HDACI in vitro leads to cooperative activation of gene transcription and reduction of cell viability in human tumor cell lines. The primary clinical objective was to determine the maximum tolerated dose (MTD) of bexarotene plus vorinostat in 23 patients with CTCLs. The MTD for part I was established at vorinostat 200 mg/day plus bexarotene 300 mg/m(2)/day. The MTD for part II was not reached. Four patients had an objective response and seven patients experienced pruritus relief. We conclude that concomitant administration of vorinostat and bexarotene is feasible only if lower doses of each drug are administered relative to the product label monotherapy doses.

Single-dose fosaprepitant for the prevention of chemotherapy-induced nausea and vomiting associated with cisplatin therapy: randomized, double-blind study protocol--EASE.

PURPOSE: Addition of aprepitant, a neurokinin-1 receptor antagonist (NK1RA), to an ondansetron and dexamethasone regimen improves prevention of chemotherapy-induced nausea/vomiting (CINV), particularly during the delayed phase (DP; 25 to 120 hours). Therefore, recommended antiemetic regimens include multiple-day NK1RA administration. Preliminary data suggested that single-dose aprepitant before chemotherapy could provide CINV protection throughout the overall risk phase (OP; 0 to 120 hours). This study compared a 3-day oral aprepitant schedule to a regimen containing a single dose of the intravenous NK1RA fosaprepitant. PATIENTS AND METHODS: A randomized, double-blind, active-control design was used to test whether fosaprepitant is noninferior to aprepitant. Patients receiving cisplatin ≥ 70 mg/m(2) for the first time received ondansetron and dexamethasone with a standard aprepitant regimen (125 mg on day 1, 80 mg on day 2, 80 mg on day 3) or a single-dose fosaprepitant regimen (150 mg on day 1). The primary end point was complete response (CR; no vomiting, no rescue medication) during OP. Secondary end points were CR during DP and no vomiting during OP. Accrual of 1,113 evaluable patients per treatment arm was planned to confirm noninferiority with expected CR of 67.7% and noninferiority margin of minus 7 percentage points. RESULTS: A total of 2,322 patients were randomly assigned, and 2,247 were evaluable for efficacy. Antiemetic protection with aprepitant and fosaprepitant was equivalent within predefined bounds for noninferiority. Both regimens were well tolerated, although more frequent infusion site pain/erythema/thrombophlebitis was seen with fosaprepitant relative to aprepitant (2.7% v 0.3%, respectively). CONCLUSION: Given with ondansetron and dexamethasone, single-dose intravenous fosaprepitant (150 mg) was noninferior to standard 3-day oral aprepitant in preventing CINV during OP and DP.

A phase I pharmacokinetic and pharmacodynamic study of dalotuzumab (MK-0646), an anti-insulin-like growth factor-1 receptor monoclonal antibody, in patients with advanced solid tumors.

PURPOSE: Insulin-like growth factor-1 receptor (IGF-1R) mediates cellular processes in cancer and has been proposed as a therapeutic target. Dalotuzumab (MK-0646) is a humanized IgG1 monoclonal antibody that binds to IGF-1R preventing receptor activation. This study was designed to evaluate the safety and tolerability of dalotuzumab, determine the pharmacokinetic (PK) and pharmacodynamic (PD) profiles, and identify a recommended phase II dose. EXPERIMENTAL DESIGN: Patients with tumors expressing IGF-1R protein were allocated to dose-escalating cohorts of three or more patients each and received intravenous dalotuzumab weekly, every 2 or 3 weeks. Plasma was collected for PK analysis. Paired baseline and on-treatment skin and tumor biopsy samples were collected for PD analyses. RESULTS: Eighty patients with chemotherapy-refractory solid tumors were enrolled. One dose-limiting toxicity was noted, but a maximum-tolerated dose was not identified. Grade 1 to 3 hyperglycemia, responsive to metformin, occurred in 15 (19%) patients. At dose levels or more than 5 mg/kg, dalotuzumab mean terminal half-life was 95 hours or more, mean C(min) was more than 25 µg/mL, clearance was constant, and serum exposures were approximately dose proportional. Decreases in tumor IGF-1R, downstream receptor signaling, and Ki67 expression were observed. (18)F-Fluorodeoxy-glucose positron emission tomography metabolic responses occurred in three patients. One patient with Ewing's sarcoma showed a mixed radiologic response. The recommended phase II doses were 10, 20, and 30 mg/kg for the weekly, every other week, and every third week schedules, respectively. CONCLUSIONS: Dalotuzumab was generally well-tolerated, exhibited dose-proportional PK, inhibited IGF-1R pathway signaling and cell proliferation in treated tumors, and showed clinical activity. The low clearance rate and long terminal half-life support more extended dosing intervals.

Development of vorinostat: current applications and future perspectives for cancer therapy.

Vorinostat is a potent histone deacetylase inhibitor that blocks the catalytic site of these enzymes. A large number of cellular proteins are modified post-translationally by acetylation, leading to altered structure and/or function. Many of these proteins, such as core nucleosomal histones and transcription factors, function in key cellular processes and signal transduction pathways that regulate cell growth, migration, and differentiation. At concentrations that are non-toxic to normal cells, vorinostat dramatically alters cellular acetylation patterns and causes growth arrest and death and in a wide range of transformed cells, both in vitro and in animal tumor models. Vorinostat has shown promising clinical activity against hematologic and solid tumors at doses that have been well tolerated by patients. Recent non-clinical experiments that explored the effects of vorinostat in combination with other chemotherapeutic agents have begun to illuminate potential mechanisms of action for this histone deacetylase inhibitor and are providing guidance for new avenues of clinical investigation.

Inhibition of NOTCH signaling by gamma secretase inhibitor engages the RB pathway and elicits cell cycle exit in T-cell acute lymphoblastic leukemia cells.

NOTCH signaling is deregulated in the majority of T-cell acute lymphoblastic leukemias (T-ALL) as a result of activating mutations in NOTCH1. Gamma secretase inhibitors (GSI) block proteolytic activation of NOTCH receptors and may provide a targeted therapy for T-ALL. We have investigated the mechanisms of GSI sensitivity across a panel of T-ALL cell lines, yielding an approach for patient stratification based on pathway activity and also providing a rational combination strategy for enhanced response to GSI. Whereas the NOTCH1 mutation status does not serve as a predictor of GSI sensitivity, a gene expression signature of NOTCH pathway activity does correlate with response, and may be useful in the selection of patients more likely to respond to GSI. Furthermore, inhibition of the NOTCH pathway activity signature correlates with the induction of the cyclin-dependent kinase inhibitors CDKN2D (p19(INK4d)) and CDKN1B (p27(Kip1)), leading to derepression of RB and subsequent exit from the cell cycle. Consistent with this evidence of cell cycle exit, short-term exposure of GSI resulted in sustained molecular and phenotypic effects after withdrawal of the compound. Combination treatment with GSI and a small molecule inhibitor of CDK4 produced synergistic growth inhibition, providing evidence that GSI engagement of the CDK4/RB pathway is an important mechanism of GSI action and supports further investigation of this combination for improved efficacy in treating T-ALL.

Phase II trial of vorinostat in recurrent glioblastoma multiforme: a north central cancer treatment group study.

PURPOSE: Vorinostat, a histone deacetylase inhibitor, represents a rational therapeutic target in glioblastoma multiforme (GBM). PATIENTS AND METHODS: Patients with recurrent GBM who had received one or fewer chemotherapy regimens for progressive disease were eligible. Vorinostat was administered at a dose of 200 mg orally twice a day for 14 days, followed by a 7-day rest period. RESULTS: A total of 66 patients were treated. Grade 3 or worse nonhematologic toxicity occurred in 26% of patients and consisted mainly of fatigue (17%), dehydration (6%), and hypernatremia (5%); grade 3 or worse hematologic toxicity occurred in 26% of patients and consisted mainly of thrombocytopenia (22%). Pharmacokinetic analysis showed lower vorinostat maximum concentration and area under the curve (0 to 24 hours) values in patients treated with enzyme-inducing anticonvulsants, although this did not reach statistical significance. The trial met the prospectively defined primary efficacy end point, with nine of the first 52 patients being progression-free at 6 months. Median overall survival from study entry was 5.7 months (range, 0.7 to 28+ months). Immunohistochemical analysis performed in paired baseline and post-vorinostat treatment samples in a separate surgical subgroup of five patients with recurrent GBM showed post treatment increase in acetylation of histones H2B and H4 (four of five patients) and of histone H3 (three of five patients). Microarray RNA analysis in the same samples showed changes in genes regulated by vorinostat, such as upregulation of E-cadherin (P = .02). CONCLUSION: Vorinostat monotherapy is well tolerated in patients with recurrent GBM and has modest single-agent activity. Histone acetylation analysis and RNA expression profiling indicate that vorinostat in this dose and schedule affects target pathways in GBM. Additional testing of vorinostat in combination regimens is warranted.

Phase 1 study of the histone deacetylase inhibitor vorinostat (suberoylanilide hydroxamic acid [SAHA]) in patients with advanced leukemias and myelodysplastic syndromes.

Vorinostat (suberoylanilide hydroxamic acid, SAHA) is a histone deacetylase inhibitor active clinically in cutaneous T-cell lymphoma and preclinically in leukemia. A phase 1 study was conducted to evaluate the safety and activity of oral vorinostat 100 to 300 mg twice or thrice daily for 14 days followed by 1-week rest. Patients with relapsed or refractory leukemias or myelodysplastic syndromes (MDS) and untreated patients who were not candidates for chemotherapy were eligible. Of 41 patients, 31 had acute myeloid leukemia (AML), 4 chronic lymphocytic leukemia, 3 MDS, 2 acute lymphoblastic leukemia, and 1 chronic myelocytic leukemia. The maximum tolerated dose (MTD) was 200 mg twice daily or 250 mg thrice daily. Dose-limiting toxicities were fatigue, nausea, vomiting, and diarrhea. Common drug-related adverse experiences were diarrhea, nausea, fatigue, and anorexia and were mild/moderate in severity. Grade 3/4 drug-related adverse experiences included fatigue (27%), thrombocytopenia (12%), and diarrhea (10%). There were no drug-related deaths; 7 patients had hematologic improvement response, including 2 complete responses and 2 complete responses with incomplete blood count recovery (all with AML treated at/below MTD). Increased histone acetylation was observed at all doses. Antioxidant gene expression may confer vorinostat resistance. Further evaluation of vorinostat in AML/MDS is warranted.