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Immune checkpoints limit the activation of the immune system and serve an important homeostatic function but can also restrict immune responses against tumors. Inhibition of specific immune checkpoint proteins such as the B7:CD28 family members programmed cell death protein-1 (PD-1) and cytotoxic T-lymphocyte antigen-4 (CTLA-4) has transformed the treatment of various cancers by promoting the anti-tumor activation of immune cells. In contrast to these effects, the V-domain immunoglobulin suppressor of T-cell activation (VISTA) regulates the steady state of the resting immune system and promotes homeostasis by mechanisms distinct from PD-1 and CTLA-4. The effects of VISTA blockade have been shown to include a decrease in myeloid suppression coupled with proinflammatory changes by mechanisms that are separate and distinct from other immune checkpoint proteins; in some preclinical studies these immune effects appear synergistic. Given the potential benefits of VISTA blockade in the context of cancer therapy, the second Annual VISTA Symposium was convened virtually on September 23, 2022, to review new research from investigators and immuno-oncology experts. Discussions in the meeting extended the knowledge of VISTA biology and the effects of VISTA inhibition, particularly on cells of the myeloid lineage and resting T cells, as three candidate anti-VISTA antibodies are in, or nearing, clinical development., Competing Interests: JB-K is the Chief Scientific Officer at, and has ownership interest including patents in, Hummingbird Bioscience. TG is the Chief Scientific Officer at, and has ownership interest including patents in, Kineta Inc. SL receives research support from the NIH. LL has served on advisory boards and as a consultant for Curis, Inc. and has received research support from Curis, Inc; and reports additional research support from AbbVie, AstraZeneca, and Bristol Myers Squibb, has served on a data safety monitoring board for G1 Therapeutics, and is the vice chair of the pharmacogenomics and population pharmacology committee of the Alliance for Clinical Trials in Oncology. JLL has patents issued and licensed to Curis, Inc. through ImmuNext. KM has received research support from the United States Department of Defense, Kidney Cancer Association, NextPoint Therapeutics, and Bristol Myers Squibb. RM is Head of Research and Development and has ownership interest at Curis, Inc. DN receives research support from the NCI and NIDCR. RN is employed by ImmuNext, has served on advisory boards and as a consultant for Curis, Inc, and reports research support from the NIH. AS has received research support to his institution from Curis, Inc.; and additional research support to his institution from Medimmune, AVID, Telix Pharmaceuticals, ITM, Fusion, Cyclotek, Adalta, TheraMyc, Humanigen, Antengene, National Health and Medical Research Council, National Imaging Facility, National Breast Cancer Foundation, Medical Research Future Fund, Australian Cancer Research Foundation, Victorian Cancer Agency. The remaining author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Noelle, Lines, Lewis, Martell, Guillaudeux, Lee, Mahoney, Vesely, Boyd-Kirkup, Nambiar and Scott.)

V-domain Ig suppressor of T-cell activation (VISTA) is a B7 family member that plays key roles in maintaining T cell quiescence and regulation of myeloid cell populations, which together establish it as a novel immunotherapy target for solid tumors. Here we review the growing literature on VISTA expression in relation to various malignancies to better understand the role of VISTA and its interactions with both tumor cells and immune cells expressing other checkpoint molecules within the tumor microenvironment (TME). The biology of VISTA creates several mechanisms to maintain the TME, including supporting the function of myeloid-derived suppressor cells, regulating natural killer cell activation, supporting the survival of regulatory T cells, limiting antigen presentation on antigen-presenting cells and maintaining T cells in a quiescent state. Understanding these mechanisms is an important foundation of rational patient selection for anti-VISTA therapy. We provide a general framework to describe distinct patterns of VISTA expression in correlation with other known predictive immunotherapy biomarkers (programmed cell death ligand 1 and tumor-infiltrating lymphocytes) across solid tumors to facilitate investigation of the most efficacious TMEs for VISTA-targeted treatment as a single agent and/or in combination with anti-programmed death 1/anti-cytotoxic T lymphocyte antigen-4 therapies., Competing Interests: AM reports research support from the NIH. MM has served on advisory boards and as a consultant for Curis, Inc. and for ImmuNext, and has intellectual property for VISTA antibodies. AU was employed by Curis, Inc. RR is employed by Curis, Inc. RN employed by ImmuNext, and has served on advisory boards and as a consultant for Curis, Inc, and reports research support from the NIH. LL has served on advisory boards and as a consultant for Curis, Inc. and has received research support from Curis, Inc; and reports additional research support from AbbVie, AstraZeneca, and Bristol Meyers Squibb, has served on a data safety monitoring board for G1 Therapeutics, and is the vice chair of the pharmacogenomics and population pharmacology committee of the Alliance for Clinical Trials in Oncology. MJ has received research support from Curis, Inc.; and reports additional research support to institution from AbbVie, Acerta, Adaptimmune, Amgen, Apexigen, Arcus Biosciences, Array BioPharma, Artios Pharma, AstraZeneca, Atreca, BeiGene, BerGenBio, BioAtla, Boehringer Ingeheim, Calithera Biosciences, Checkpoint Therapeutics, Corvus Pharmaceuticals, Cytomx, Daiichi Sankyo, Dracen Pharmaceuticals, Dynavax, Lilly, EMD Serono, Erasca, Exelixis, Fate Therapeutics, Genentech/Roche, Genmab, Genocea Biosciences, GlaxoSmithKline, Gritstone Oncology, Guardant Health, Harpoon, Helsinn Healthcare, Hengrui Therapeutics, Hutchison MediPharma, IDEAYA Biosciences, IGM Biosciences, Immunocore, Incyte, Janssen, Jounce Therapeutics, Kadmon Pharmaceuticals, Loxo Oncology, Lycera, Memorial Sloan-Kettering, Merck, Merus, NeoImmune Tech, Neovia Oncology, Novartis, Numab Therapeutics, Nuvalent, OncoMed Pharmaceuticals, Pfizer, PMV Pharmaceuticals, RasCal Therapeutics, Regeneron Pharmaceuticals, Relay Therapeutics, Revolution Medicine, Ribon Therapeutics, Rubius Therapeutics, Sanofi, Seven and Eight Biopharmaceuticals / Birdie Biopharmaceuticals, Shattuck Labs, Silicon Therapeutics, Stem CentRx, Syndax Pharmaceuticals, Takeda Pharmaceuticals, Tarveda, TCR2 Therapeutics, Tempest Therapeutics, Tizona Therapeutics, TMUNITY Therapeutics, Turning Point Therapeutics, University of Michigan, Vyriad, WindMIL, Y-mAbs Therapeutics, Black Diamond, Carisma Therapeutics, Elicio Therapeutics, EQRx, Impact, Kartos Therapeutics, Mirati Therapeutics, Palleon Pharmaceuticals, and Rain Therapeutics, and has served as a consultant for AbbVie, Amgen, Astellas, AstraZeneca, Axelia Oncology, Black Diamond, Calithera Biosciences, Checkpoint Therapeutics, CytomX Therapeutics, Daiichi Sankyo, EcoR1, Editas Medicine, Eisai, EMD Serono, G1 Therapeutics, Genentech/Roche, Genmab, Genocea Biosciences, GlaxoSmithKline, Gritstone Oncology, Ideaya Biosciences, iTeos, Janssen, Lilly, Merck, Mirati Therapeutics, Molecular Axiom, Novartis, Oncorus, Regeneron Pharmaceuticals, Ribon Therapeutics, Sanofi-Aventis, Turning Point Therapeutics, and VBL Therapeutics. LR has served on advisory boards and as a consultant for Curis, Inc. RM is employed by Curis, Inc. This manuscript received medical writing support funded by Curis, Inc. The funder was not involved in the study design, collection, analysis, interpretation of data, the writing of this article or the decision to submit it for publication. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Martin, Molloy, Ugolkov, von Roemeling, Noelle, Lewis, Johnson, Radvanyi and Martell.)

Objectives: To explore the association between hormone therapy (HT) adherence and non-drug healthcare utilisation and healthcare costs among patients with breast cancer., Design: Retrospective longitudinal cohort study., Setting: The US Medicare beneficiaries in the SEER-Medicare-linked database PARTICIPANTS: Women aged ≥ 65 with hormone-receptor positive breast cancer from 2007 through mid-2009 in the USA., Interventions: We examined the relationship between HT and adherence and outcomes of our interests., Primary and Secondary Outcome Measures: Our study cohort's HT adherence, non-drug healthcare utilisation and healthcare costs for the first year of HT and each year, thereafter, for a total of 5 years., Results: 6045 eligible Medicare beneficiaries that met our selection criteria were included. We found that patients who were adherent to HT were associated with lower healthcare utilisation of all kinds (inpatient (0.35 vs 0.43, p<0.001), length of study during hospitalisation (4.19 vs 4.89, p<0.01), physician office visits (25.16 vs 26.17, p<0.001)), and significant reductions in many types of medical costs and neutral total healthcare costs despite the increased pharmacy costs. Half of the total medical cost reduction came from savings in hospitalisation costs., Conclusions: Our study suggests that the added cost of HT adherence was all but offset by the reduced cost for other medical care. Our study provides evidence on the potential success of implementing value-based insurance design (VBID) plans among patients with breast cancer to improve their long-term oral medication adherence. Policymakers should consider adherence improvement strategies such as VBID plans, given that the costs likely will not surpass the total savings., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2021. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Fimepinostat (CUDC-907), a first-in-class oral small-molecule inhibitor of histone deacetylase and phosphatidylinositol 3-kinase, demonstrated efficacy in a phase 1 study of patients with relapsed/refractory (R/R) diffuse large and high-grade B-cell lymphomas (DLBCL/HGBL), particularly those with increased MYC protein expression and/or MYC gene rearrangement/copy number gain (MYC-altered disease). Therefore, a phase 2 study of fimepinostat was conducted in this patient population with 66 eligible patients treated. The primary end-point of overall response (OR) rate for patients with MYC-IHC ≥40% (n = 46) was 15%. Subsequently, exploratory pooled analyses were performed including patients treated on both the phase 1 and 2 studies based upon the presence of MYC-altered disease as well as a biomarker identified by Virtual Inference of Protein activity by Enriched Regulon analysis (VIPER). For these patients with MYC-altered disease (n = 63), the overall response (OR) rate was 22% with seven responding patients remaining on treatment for approximately two years or longer, and VIPER yielded a three-protein biomarker classification with positive and negative predictive values of ≥85%. Prolonged durations of response were achieved by patients with MYC-altered R/R DLBCL/HGBL treated with single-agent fimepinostat. Combination therapies and/or biomarker-based patient selection strategies may lead to higher response rates in future clinical trials., (© 2021 British Society for Haematology and John Wiley & Sons Ltd.)

Objective: To examine the different levels of copayment assistance and treatment adherence among Medicare and Medicaid dual eligible beneficiaries with breast cancer in the U.S., Research Design: Propensity Score methodology was adopted to minimize potential selection bias from the nonrandom allocation of the treatment group (i.e., full Medicaid beneficiaries) and control group (i.e., Medicare Savings Programs [MSPs] beneficiaries). Longitudinal hierarchical model and Cox proportional-hazard model were adopted to examine patients' adherence over their full five-year course of adjuvant hormone therapy., Results: Our study cohort consisted of 1,133 dual eligible beneficiaries diagnosed with hormone receptor-positive early stage breast cancer in years 2007 -mid 2009. About 80.5% of them received MSPs benefits, while the rest received full Medicaid benefits. On average for a standardized 30-day hormone therapy medication, full Medicaid beneficiaries spent $0.5-$2.0 and MSP beneficiaries spent $1.4-$4.8 in copayment. After adjusting for other factors, this copayment reduction wasn't associated with a significantly better adherence. However, when the catastrophic coverage threshold was reached (copayments reduced to zero), significant improvement in adherence was found in both groups., Conclusions: Our study found that small amount of cost-sharing reduction did not affect Medicare and Medicaid dual eligible patients' medication treatment adherence, however, the elimination of cost-sharing (even a minimal amount) was associated with improved adherence. Future legislative and advocacy efforts should be paid on eliminating cost sharing for dual eligibles, and possibly even a broader group of financially vulnerable patients., Competing Interests: S. Ma, C. Thomas, G. Ritter, and R. Martell and have no conflicts of interest. D. Shepard reports grants from Sanofi Pasteur, grants from Takeda Vaccines, Inc, outside the submitted work. These relate to grants to studying the economics of other viral diseases, with no relation to cancer. This does not alter our adherence to PLOS ONE policies on sharing data and materials.

Background: High out-of-pocket costs (OOPCs) often are found to be inversely associated with adherence to medical treatment. The introduction of generic aromatase inhibitors (GAIs) significantly reduced the OOPCs of patients. The objective of the current study was to explore the impact of the introduction of GAIs on adjuvant hormone therapy (AHT) adherence over the full course of breast cancer treatment., Methods: Women aged ≥65 years who were diagnosed with hormone receptor-positive breast cancer from 2007 through mid-2009 were identified from the Surveillance, Epidemiology, and End Results (SEER)-Medicare-linked database. Multivariate logistic regression was used to estimate the likelihood of AHT initiation and an interrupted time series model was used to predict the association between the introduction of GAIs and AHT adherence. The model was stratified further using Medicare low-income subsidy (LIS) status., Results: A total of 10,905 women were included, approximately 62.8% of whom initiated AHT within the first year of their breast cancer diagnosis. Adjusted adherence among LIS beneficiaries was 11.4% higher than among non-LIS beneficiaries (P < .001). Non-LIS beneficiaries had an overall decreasing trend of adherence (-0.035; P < .001) prior to the introduction of GAIs. They experienced a 3.4% increase in the slope 6 months after the first GAI, anastrozole, entered the market, and an additional 0.8% increase in the slope 6 months after letrozole and exemestane were introduced (P < .001). Adherence change among LIS patients was small and statistically insignificant., Conclusions: With the introduction of GAIs, the decrease trend of adherence to therapy atteunated over the course of treatment. Although the successful implementation of the Medicare LIS program minimized the OOPCs for financially vulnerable patients, policymakers should be cautious not to introduce disparities for those who may be of low income but ineligible for such a program., (© 2020 American Cancer Society.)

Background: Observational studies have demonstrated association of metformin with reduced cancer incidence and mortality in multiple cancer types, including gastrointestinal (GI) malignancies. Anti-neoplastic effects of metformin are believed through many mechanisms including activation of AMP-activated protein kinase, which controls mammalian target of rapamycin (mTOR) growth regulatory pathway., Methods: In a pilot, delayed-start randomized study, non-diabetic patients with GI cancers were randomized to 2 arms, Stage 1: concurrent metformin (500mg twice daily) plus chemotherapy vs. chemotherapy alone followed by cross over to metformin plus chemotherapy arm in Stage 2, while adverse events (DLT) were assessed by CTCAE v.3.0. As a translational correlate, we used phosphorylation of AMPKα at Thr172 to measure AMPK activation by western blot technique in PBMCs isolated from patients before and after receiving M. These levels were correlated with radiological (RECIST 1.1) and tumor marker outcomes by descriptive analysis. In this study, we present the sub-group analysis of patients with GI cancers., Results: 41 patients with GI cancers (colorectal: 22, pancreatic: 12, gastroesophageal: 4, biliary: 2, others: 1) were treated in this trial. Mean duration of metformin therapy was 85 days (range: 9-443). There was no significant difference in grade 3 or above DLT in metformin plus chemotherapy vs. chemotherapy arm (14% vs. 12% respectively). Gel band density analysis on 19 patients showed that 63% patients had increased phosphorylation of AMPKα after metformin (ratio of phospho-AMPKα after and before metformin > 1) with mean = 1.227 (± 0.134). RECIST 1.1 restaging showed disease control in 55% patients and 45% patients had decline in tumor markers. Of note, 60% of patients with disease control also showed increase in phosphorylation of AMKα., Conclusions: This group of patients treated with metformin prospectively demonstrates the impact of metformin on AMPKα phosphorylation, and correlates with clinical benefit in patients with GI cancers when metformin was added to systemic chemotherapy of varying types. We aim to perform a dose-escalation of metformin in our next study with additional metabolomics correlates.

Background: Metformin has been associated with improved colorectal cancer survival, but investigations are limited by small numbers of patients and confounding by diabetic severity. We examined the association between metformin use and overall survival (OS) in patients with diabetes and colorectal cancer in a large population of U.S. veterans, while adjusting for measures of diabetic severity., Methods: Patients diagnosed with colorectal cancer from January 2001 to December 2008 were identified from the Veterans Affairs Central Cancer Registry. Multivariable models were used to examine the adjusted association of OS with diabetes and use of antidiabetic medications., Results: There were 21,352 patients diagnosed with colorectal cancer identified (n = 16,355 nondiabetic patients, n = 2,038 diabetic patients on metformin, n = 2,136 diabetic patients on medications other than metformin, n = 823 diabetic patients not on antidiabetic medication). Diabetic patients had a significantly worse OS than nondiabetic patients, but metformin users had only a 10% increase in death (HR adj 1.10; 95% CI, 1.03-1.17, P = 0.004), as compared with 22% for users of other antidiabetic medications (HR adj 1.22; 95% CI, 1.15-1.29, P < 0.0001). Among colorectal cancer patients with diabetes, metformin users had a 13% improved OS versus patients taking other antidiabetic medications (HR adj 0.87; 95% CI, 0.79-0.95, P = 0.003), while diabetic patients not on any antidiabetic medications did not differ with respect to OS (HR adj 1.02; 95% CI, 0.90-1.15, P = 0.76)., Conclusions: Among diabetics with colorectal cancer, metformin use is associated with improved survival, despite adjustments for diabetes severity and other risk factors., Impact: These data lend further support to the conduct of randomized studies of possible anticancer effects of metformin among patients with colorectal cancer. Cancer Epidemiol Biomarkers Prev; 25(10); 1418-25. ©2016 AACR., (©2016 American Association for Cancer Research.)

Background: Observational studies have associated metformin use with lower colorectal cancer (CRC) incidence but few studies have examined metformin's influence on CRC survival. We examined the relationships among metformin use, diabetes, and survival in postmenopausal women with CRC in the Women's Health Initiative (WHI) clinical trials and observational study., Methods: 2066 postmenopausal women with CRC were followed for a median of 4.1 years, with 589 deaths after CRC diagnosis from all causes and 414 deaths directly attributed to CRC. CRC-specific survival was compared among women with diabetes with metformin use (n=84); women with diabetes with no metformin use (n=128); and women without diabetes (n=1854). Cox proportional hazard models were used to estimate associations among metformin use, diabetes and survival after CRC. Strategies to adjust for potential confounders included: multivariate adjustment with known predictors of colorectal cancer survival and construction of a propensity score for the likelihood of receiving metformin, with model stratification by propensity score quintile., Results: After adjusting for age and stage, CRC specific survival in women with diabetes with metformin use was not significantly different compared to that in women with diabetes with no metformin use (HR 0.75; 95% CI 0.40-1.38, p=0.67) and to women without diabetes (HR 1.00; 95% CI 0.61-1.66, p=0.99). Following propensity score adjustment, the HR for CRC-specific survival in women with diabetes with metformin use compared to non-users was 0.78 (95% CI 0.38-1.55, p=0.47) and for overall survival was 0.86 (95% CI 0.49-1.52; p=0.60)., Conclusions: In postmenopausal women with CRC and DM, no statistically significant difference was seen in CRC specific survival in those who used metformin compared to non-users. Analyses in larger populations of colorectal cancer patients are warranted., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Background: Once a promising drug target is identified, the steps to actually discover and optimize a drug are diverse and challenging., Objective: The goal of this study was to provide a road map to navigate drug discovery., Methods: Review general steps for drug discovery and provide illustrating references., Results: A number of approaches are available to enhance and accelerate target identification and validation. Consideration of a variety of potential mechanisms of action of potential drugs can guide discovery efforts. The hit to lead stage may involve techniques such as high-throughput screening, fragment-based screening, and structure-based design, with informatics playing an ever-increasing role. Biologically relevant screening models are discussed, including cell lines, 3-dimensional culture, and in vivo screening. The process of enabling human studies for an investigational drug is also discussed., Conclusions: Drug discovery is a complex process that has significantly evolved in recent years., (© 2013 Elsevier HS Journals, Inc. All rights reserved.)

Background: Regulatory approval of oncology drugs is the cornerstone of the development process and approval characteristics shape eventual utilization. Approval trends and characteristics provide valuable information for drug developers and regulators and ultimately affect clinicians and patients., Methods: Indication characteristics were tabulated for drugs approved by the U.S. Food and Drug Administration (FDA) for systemic therapy of malignancies from 1949 through October 2011. Variables included time to approval, initial/supplemental indication, tumor type, stage of disease, specification of protein expression or genetic information, drug class, trial design, concomitant agent, trial size, and endpoint., Results: A total of 121 unique anticancer agents, including 242 unique indications, were approved. The number of trials for each indication has decreased; however, trial size has increased and more randomized controlled trials have been performed. Trial designs have increasingly used time-to-event endpoints and rarely have used symptom-based primary endpoints. Approvals have been primarily single agent, with less emphasis on palliative treatments and increasing emphasis on advanced disease stages and requirements for prior therapy. Molecular specifications in labels have increased, but they are present in less than 30% of recent indications and are not associated with shorter approval times., Conclusion: Approval of oncology agents is occurring in increasingly more challenging settings, suggesting gaps between eventual practice and development in potentially suboptimal indications. Molecular specifications promise to enhance development, yet widespread use in label indications has not yet been achieved.

Background: In carcinogenesis, methylation of DNA promoter regions results in inactivation of tumor-suppressing genes. MG98 was designed to inhibit DNA methyltransferases enzyme 1 production., Methods: This multicenter study explored two schedules of MG98 with Interferon-α-2β to identify schedule and dose for patients with metastatic RCC., Results: Doses of IFN 9 MIU/MG98 125 mg/m(2) for a continuous schedule and IFN 9 MIU/MG98 200 mg/m(2) for an intermittent schedule were considered the MTDs. Treatment resulted in one PR and eight SD., Conclusion: MG98 combined with IFN was safe and resulted in clinical activity.

Purpose: We studied the safety, tolerability, and recommended dose of BMS-599626, an orally bioavailable inhibitor of the human epidermal growth factor receptor (HER) family of receptor tyrosine kinases., Patients and Methods: Patients with advanced solid tumors that expressed epidermal growth factor receptor (EGFR) and/or HER-2 were recruited and enrolled in a phase I, open-label, dose escalation trial of oral BMS-599626 starting at 100 mg/day given once daily for at least 28 days., Results: Forty-five patients received BMS-599626 (100-660 mg/day). Dose-limiting toxic effects were reported at 660 mg/day (grade 3 elevation of hepatic transaminases [two patients] and QTc interval prolongation [one patient]), therefore the recommended maximum tolerated dose was 600 mg/day. The most frequent drug-related toxic effects were diarrhea (30% of patients), anorexia (13%), asthenia (30%), and cutaneous toxic effects, including skin rash (30%). Pharmacokinetic analysis demonstrated C(max) and exposure to BMS-599626 in patients increased with dose. Eleven patients had stable disease and received BMS-599626 for ≥ 4 months. Serial skin and tumor biopsies taken before and after treatment revealed expected changes in pharmacodynamic biomarkers, indicating that the EGFR and HER-2 pathways were affected. Positron emission tomography imaging showed a metabolic response in 2 of 10 patients evaluated., Conclusion: BMS-599626 was generally well tolerated, with disease stabilization across a range of tumor types and doses.

Background: The prognosis of patients with relapsed Hodgkin's lymphoma, especially those who relapse after stem-cell transplantation, is poor, and the development of new agents for this patient population is an unmet medical need. We tested the safety and efficacy of mocetinostat, an oral isotype-selective histone deacetylase inhibitor, in patients with relapsed classical Hodgkin's lymphoma., Methods: Patients with relapsed or refractory classical Hodgkin's lymphoma aged 18 years or older were treated with mocetinostat administered orally three times per week, in 28-day cycles. Two doses were assessed (85 mg and 110 mg). Patients were treated until disease progression or prohibitive toxicity. The primary outcome was disease control rate, defined as complete response, partial response, or stable disease (for at least six cycles), analysed by intention to treat. This trial has been completed and is registered with ClinicalTrials.gov, number NCT00358982., Findings: 51 patients were enrolled. Initially, 23 patients were enrolled in the 110 mg cohort. Subsequently, because toxicity-related dose reductions were necessary in the 110 mg cohort, we treated 28 additional patients with a dose of 85 mg. On the basis of intent-to-treat analysis, the disease control rate was 35% (eight of 23 patients) in the 110 mg group and 25% (seven of 28) in the 85 mg group. 12 patients (24%) discontinued treatment because of adverse events, nine (32%) in the 85 mg cohort and three (13%) in the 110 mg cohort. The most frequent treatment-related grade 3 and 4 adverse events were neutropenia (four patients [17%] in the 110 mg group, three [11%] in the 85 mg group); fatigue (five patients [22%] in the 110 mg group, three [11%] in the 85 mg group); and pneumonia (four patients [17%] in the 110 mg group, two [7%] in the 85 mg group). Four patients, all in the 110 mg cohort, died during the study, of which two might have been related to treatment., Interpretation: Mocetinostat, 85 mg three times per week, has promising single-agent clinical activity with manageable toxicity in patients with relapsed classical Hodgkin's lymphoma., Funding: MethylGene Inc, Montreal, Canada; Celgene Corporation, Summit, NJ, USA; Tufts Medical Center, Boston, MA, USA., Competing Interests: AY received consulting fees in relation to this study from Methylgene. He also provided consultancy to Celgene, Seattle Genetics, Novartis, Syndax, and Sanofi. JB, ZL, MD, and TP are employees of Methylgene. RW is an employee of Celgene. REM is a previous employee of Methylgene and has stock ownership in the company. YO, GB, JK, MF, SN, AC, DB, AG, YJ, JKP and LJM dclare that they have no conflict of interest, (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Inhibition of histone deacetylase 6 (HDAC6)-dependent aggresome function by pan HDAC inhibitors was recently reported to be a key mechanism underlying the synergistic activity between proteasome inhibitors and HDAC inhibitors in a variety of tumour types. Because these combinations induce significant thrombocytopenia in vivo, we examined whether less toxic, isotype-selective HDAC inhibitors may still synergize with proteasome inhibitors, and if so, by what mechanisms. Here, we showed that the class I HDAC inhibitor, MGCD0103, has a potent antiproliferative activity in Hodgkin lymphoma (HL) cell lines. Furthermore, MGCD0103 induced tumour necrosis factor α (TNF-α) expression and secretion, which was associated with nuclear factor (NF)-κB activation. Selective inhibition of TNF-α expression by short interfering mRNA, or inhibition of MGCD0103-induced NF-kB activation by proteasome inhibitors enhanced MGCD0103-induced cell death. Thus, our results demonstrate that MGCD0103 may synergize with proteasome inhibitors by HDAC6-independent mechanisms, providing mechanistic rationale for exploring this potentially less toxic combination for the treatment of lymphoma., (© 2010 Blackwell Publishing Ltd.)

MGCD0103, an orally available class I histone deacetylase (HDAC) inhibitor, was examined for pre-clinical activity in chronic lymphocytic leukaemia (CLL). A phase II clinical trial was performed, starting at a dose of 85 mg/d, three times per week. Dose escalation to 110 mg or the addition of rituximab was permitted in patients without a response after two or more cycles. MGCD0103 demonstrated pre-clinical activity against CLL cells with a LC(50) (concentration lethal to 50%) of 0.23 micromol/l and increased acetylation of the HDAC class I specific target histone H3. Twenty-one patients received a median of two cycles of MGCD0103 (range, 0-12). All patients had previously received fludarabine, 33% were fludarabine refractory, and 71% had del(11q22.3) or del(17p13.1). No responses according to the National Cancer Institutes 1996 criteria were observed. Three patients received 110 mg and four patients received concomitant rituximab, with no improvement in response. Grade 3-4 toxicity consisted of infections, thrombocytopenia, anaemia, diarrhoea, and fatigue. HDAC inhibition was observed in six out of nine patients on day 8. Limited activity was observed with single agent MGCD0103 in high risk patients with CLL. Future investigations in CLL should focus on broad HDAC inhibition, combination strategies, and approaches to diminish constitutional symptoms associated with this class of drugs.

MGCD0103 is an isotype-selective inhibitor of histone deacetylases (HDACs) targeted to isoforms 1, 2, 3, and 11. In a phase 1 study in patients with leukemia or myelodysplastic syndromes (MDS), MGCD0103 was administered orally 3 times weekly without interruption. Twenty-nine patients with a median age of 62 years (range, 32-84 years) were enrolled at planned dose levels (20, 40, and 80 mg/m(2)). The majority of patients (76%) had acute myelogenous leukemia (AML). In all, 24 (83%) of 29 patients had received 1 or more prior chemotherapies (range, 0-5), and 18 (62%) of 29 patients had abnormal cytogenetics. The maximum tolerated dose was determined to be 60 mg/m(2), with dose-limiting toxicities (DLTs) of fatigue, nausea, vomiting, and diarrhea observed at higher doses. Three patients achieved a complete bone marrow response (blasts

Purpose: The pharmacodynamic properties of MGCD0103, an isotype-selective inhibitor of histone deacetylase (HDAC), were evaluated in preclinical models and patients with a novel whole-cell HDAC enzyme assay., Experimental Design: Boc-Lys(epsilon-Ac)-AMC, a HDAC substrate with fluorescent readout, was found to be cell permeable and was used to monitor MGCD0103-mediated HDAC inhibition in cultured cancer cells in vitro, in peripheral WBC ex vivo, in mice in vivo, and in human patients., Results: MGCD0103 inhibited HDAC activity in several human cancer cell lines in vitro and in human peripheral WBC ex vivo in a dose-dependent manner. Unlike suberoylanilide hydroxamic acid, the HDAC inhibitory activity of MGCD0103 was time dependent and sustained for at least 24 hours following drug removal in peripheral WBC ex vivo. Inhibitory activity of MGCD0103 was sustained for at least 8 hours in vivo in mice and 48 hours in patients with solid tumors. HDAC inhibitory activity of MGCD0103 in peripheral WBC correlated with induction of histone acetylation in blood and in implanted tumors in mice. In cancer patients, sustained pharmacodynamic effect of MGCD0103 was visualized only by dose-dependent enzyme inhibition in peripheral WBC but not by histone acetylation analysis., Conclusions: This study shows that MGCD0103 has sustained pharmacodynamic effects that can be monitored both in vitro and in vivo with a cell-based HDAC enzyme assay.

Purpose: SNS-032, (formerly BMS-387032) is a potent and selective inhibitor of cyclin-dependent kinases (CDK) 2, 7 and 9. The primary objective of the study was to establish the maximum tolerated dose (MTD), the maximum administered dose (MAD), dose limiting toxicity (DLT), and the recommended phase 2 dose for SNS-032 when administered as a weekly 1-h infusion. The secondary objective was to assess the safety and tolerability of SNS-032 and to evaluate its bioavailability as an oral solution., Methods: Patients with metastatic solid tumors or refractory lymphoma were treated with a starting dose of 4 mg/m2 intravenously administered over 1-h with a cycle defined as 3 weekly doses of SNS-032 every 21 days. Three patient cohorts were utilized in the dose-escalation schema. Pharmacokinetic studies were performed. For the 13 and 16 mg/m2 dose cohorts, the first dose of cycle 2 was given as an oral solution to estimate the oral bioavailability of the drug in humans., Results: A total of 21 patients were enrolled. Twenty treated patients received a total of 39 cycles of treatment. The most common treatment-related adverse events occurring with greater than 20% incidence were fatigue (25%) and nausea (20%). Following intravenous administration, plasma concentrations declined in a biphasic manner, resulting in mean terminal half-lives between 5 and 10 hours. The mean Cmax and AUC0-inf increased nearly linearly with dose, ranging from 0.067 to 0.287 microg/ml and 0.103 to 0.553 microg h/ml, respectively. The CL and Vss remained unchanged with increasing dose levels, averaging 38 l/h/m2 and 212 l/m2, respectively. Average oral bioavailability was 19% (range: 4-33%). Three (15%) patients experienced a best response of stable disease. Study enrollment was terminated during dose-escalation due to a change in the development strategy for the study drug., Conclusions: SNS-032 administered as a weekly 1-h infusion was well tolerated, although study enrollment was terminated during dose-escalation and the MTD of SNS-032 administered intravenously on days 1, 8, and 15 of each treatment cycle was not reached. Tumor progression or stable disease was determined to be the best response in all evaluable patients. At the dose levels tested, the oral bioavailability of SNS-032 ranged from 4-33%. The data suggest that oral administration of SNS-032 may be feasible, though the tolerability and bioavailability of the oral formulation would have to be formally assessed.

Histone deacetylase (HDAC) inhibitors constitute a novel and growing class of anticancer agents that function by altering intracellular patterns of histone acetylation, the so-called epigenetic "histone code," thereby producing changes in cell cycle arrest, differentiation, and/or apoptosis in tumor cells. This overview describes the chemistry and preliminary characterization of recently disclosed molecules in three major classes of HDAC inhibitors: hydroxamic acids, 2-amino- benzanilides, and cyclic peptides. In addition, results from recent clinical trials on isotype-selective HDAC inhibitors are reviewed. It is clear from the plethora of new molecules and the encouraging results from clinical trials that HDAC inhibitors hold a great deal of promise, particularly as add-on therapy, for the treatment of a variety of solid and hematologic cancers.

Purpose: To assess the maximum tolerated dose (MTD), dose-limiting toxicity (DLT), pharmacodynamics, and antitumor activity of continuous weekly-administered paclitaxel and BMS-214662, a novel farnesyl transferase inhibitor., Experimental Design: Patients were treated every week as tolerated with i.v. paclitaxel (fixed dose, 80 mg/m(2)/wk) administered over 1 h followed by i.v. BMS-214662 (escalating doses, 80-245 mg/m(2)/wk) over 1 h starting 30 min after completion of paclitaxel., Results: Twenty-six patients received 94 courses (one course, 21 days) of study treatment. Two patients received five courses of BMS-214662 as a weekly 24-h infusion (209 mg/m(2)/wk). The most common toxicities were grade 1 to 2 nausea/vomiting and/or diarrhea. DLTs observed at or near the MTD (200 mg/m(2)/wk) were grade 4 febrile neutropenia with sepsis occurring on day 2 of course 1 (245 mg/m(2)/wk), reversible grade 3 to 4 serum transaminase increases on day 2, and grade 3 diarrhea (200 and 245 mg/m(2)/wk). Objective partial responses were observed in patients with pretreated head and neck, ovarian, and hormone-refractory prostate carcinomas, and leiomyosarcoma. The observed pharmacokinetics of paclitaxel and BMS-214662 imply no interaction between the two. Significant inhibition (>80%) of farnesyl transferase activity in peripheral mononuclear cells was observed at the end of BMS-214662 infusion., Conclusions: Pretreated patients with advanced malignancies can tolerate weekly paclitaxel and BMS-214662 at doses that achieve objective clinical benefit. Due to multiple DLTs occurring at the expanded MTD, the recommended phase 2 dose and schedule is paclitaxel (80 mg/m(2) over 1 h) and BMS-214662 (160 mg/m(2) over 1 h) administered weekly.

Purpose: This phase I study was conducted to determine the toxicities, pharmacokinetics, and pharmacodynamics of BMS-214662, a farnesyl transferase inhibitor, in combination with paclitaxel and carboplatin, in patients with advanced solid tumors., Experimental Design: Patients with solid tumors received one of six escalating dose levels of BMS-214662 infused over 1 hour given following paclitaxel and carboplatin on the first day of a 21-day cycle. Toxicities were graded by the National Cancer Institute common toxicity criteria and recorded as maximum grade per patient for each treatment cycle. Inhibition of farnesyl transferase activity in peripheral blood mononuclear cells (PBMCs) was evaluated. Accumulation of unfarnesylated HDJ-2 in PBMCs of patients was evaluated as a marker of farnesyl transferase inhibition by BMS-214662., Results: Thirty patients received 141 cycles of treatment through six dose levels. Dose-limiting toxicities were neutropenia, thrombocytopenia, nausea, and vomiting. There was no pharmacokinetic interaction between BMS-214662 and paclitaxel. The maximum tolerated dose was established as BMS-214662 (160 mg/m(2)), paclitaxel (225 mg/m(2)) and carboplatin (area under the curve = 6 on day 1), every 21 days. Inhibition of HDJ-2 farnesylation in PBMCs of patients was shown. One measurable partial response was observed in a patient with taxane-resistant esophageal cancer. There was partial regression of evaluable disease in two other patients (endometrial and ovarian cancer). Stable disease (> 4 cycles) occurred in eight other patients., Conclusions: The combination of BMS-214662 with paclitaxel and carboplatin was well tolerated, with broad activity in solid tumors. There was no correlation between dose level and accumulation of unfarnesylated HDJ-2 in PBMCs nor tumor response.

RNA aptamers against a variety of clinically relevant target proteins have been generated. For example, we previously isolated an RNA aptamer that inhibits the function of the E2F family of transcription factors that play a critical role in the control of cell proliferation. However, the development of this and other aptamers for gene therapy applications has been complicated by the fact that expression of RNA aptamers in the context of flanking sequences can inhibit the ability of an aptamer to fold into its functional conformation. Insertion of the E2F aptamer into a tRNA expression cassette resulted in the production of high levels of chimeric tRNA that contains a misfolded and inactive aptamer in transfected mammalian cells. To overcome this problem, we randomized the sequence flanking the aptamer and selected for chimeric tRNAs that retained high affinity binding to E2F1. This expression cassette SELEX strategy yielded RNAs that bind E2F with high affinity (IC50 of 15 nM) and which can be expressed at high levels in mammalian cells. Moreover, these chimeric tRNA-E2F aptamers are functional and can inhibit E2F-mediated transactivation by up to 80% in human 293 cells. Expression cassette SELEX should greatly facilitate the use of aptamers for a variety of gene therapy applications.

Purpose: Fludarabine is a renally excreted agent that is an effective treatment for chronic lymphocytic leukemia (CLL), a disease predominantly of the elderly. We sought to determine whether age, renal function or pretreatment hematologic status predicted toxicity of fludarabine treatment for CLL., Methods: We evaluated 192 patients with previously untreated B-cell CLL who were entered onto the fludarabine treatment arm (25 mg/m(2) daily for 5 days every 28 days) of CALGB study 9011, an intergroup study with participation from SWOG, CTG/NCI-C and ECOG. Patients were required to have serum creatinine within 1.5 times normal. Hematologic indices and infections were recorded during the first 28-day cycle of treatment. A time-to-toxicity endpoint was evaluated over the entire course of fludarabine treatment. Creatinine clearance (CrCl(est)) was estimated using serum creatinine, age and body mass index., Results: The median age was 64 years (range 37-87 years) and median CrCl(est) was 62 ml/min (range 27-162 ml/min, interquartile range 52-79 ml/min). We found no association between age and incidence of hematologic toxicity or infection during the first cycle of treatment. There was a strong association between CrCl(est) and the time-to-toxicity endpoint. Patients with CrCl(est) below 80 ml/min had increased incidence of toxicity during their treatment course ( P<0.0001). Pretreatment anemia, thrombocytopenia and Rai stage were highly associated with the incidence of neutrophil toxicity and grade III/IV hematologic toxicities during the first cycle of treatment ( P<0.0001)., Conclusions: Patient age was not an independent risk factor for fludarabine-related toxicity, but CrCl(est) was associated with time to toxicity.

Purpose: Comprehensive geriatric assessment (CGA) has aided the medical community greatly in understanding the quality-of-life issues and functional needs of older patients. With its professional team assessment approach, however, CGA may be time consuming and costly. The goal of the present study was to assess the ability of cancer patients to complete a self-administered CGA and then to characterize cancer patients across multiple domains and age groups., Patients and Methods: Two hundred sixty-six male outpatient oncology patients at the Durham Veterans Affairs Medical Center were asked to fill out a survey assessing 10 domains (demographics, comorbid conditions, activities of daily living, functional status, pain, financial well being, social support, emotional state, spiritual well-being, and quality of life)., Results: Seventy-six percent of the patients who received their surveys and kept their appointments returned the assessment tool. Older oncology patients had significantly less education (P <.0001), income (P =.05), frequent exercise (P =.01), and chance of being disease free (P =.003) than younger patients. Other findings in older patients were a higher rate of marriage (P =.02), more difficulty in taking medications (P =.05), and less cigarette (P =.03) and alcohol (P =.03) use. Members of all age cohorts reported a sense of social support, with younger patients deriving this more from family and friends than older patients, and older patients deriving social support more from membership in religious communities than younger patients. No differences were found across age groups for number and impact of comorbid illnesses, number of medications, basic and instrumental activities of daily living, pain, overall health rating, financial adequacy, anxiety, depression, and quality of life., Conclusion: CGA can be conducted in an outpatient cancer community using a self-report format. Despite the fact that this population varied demographically across age groups and is limited to veterans, this study demonstrated remarkable similarities between younger and older cancer patients in terms of functional status, health states, and quality of life.

A recombinant human IL-2 analog (rIL-2, Proleukin) is currently being evaluated for clinical benefit in HIV infected patients. It is approved for therapy of patients with metastatic melanoma and renal cell carcinoma. Treatment of cancer patients with rIL-2 results in durable responses but is associated with life-threatening toxicity, which limits its use to patients in relatively good health. Antitumor efficacy associated with rIL-2 therapy are hypothesized to be mediated by distinct types of cells that express structurally different forms of the IL-2 receptor. This hypothesis suggests that it might be possible to engineer an IL-2 variant addressing the risks associated with the therapeutic use of IL-2. In this article, we review the clinical experience with IL-2 and its analogs, the evidence that different IL-2 receptors may dissociate efficacy and toxicity, and describe the generation of a novel IL-2 variant with the potential for a superior therapeutic index.

Unraveling the mechanisms underlying cellular senescence will contribute to the understanding of processes involved in aging and cancer. We sought to determine whether expression of cellular factors in senescent WI-38 human fibroblasts was sufficient to induce nuclear DNA synthesis. Expression by recombinant adenovirus of E2F1, E2F2, E2F3, cyclin E/cdk2, and Mdm2 individually resulted in DNA synthesis in 10-30% of cells. However, combination of Mdm2 with E2F or cyclin E/cdk2 resulted in 50 to 75% of cells synthesizing DNA. DNA synthesis occurred approximately 30 h following infection. We conclude that expression of normal cellular factors is sufficient to induce DNA synthesis in senescent normal human fibroblasts., (Copyright 2001 Academic Press.)

Purpose: We sought to determine whether therapy with single-agent fludarabine compared with chlorambucil alone or the combination of both agents had an impact on the incidence and spectrum of infections among a series of previously untreated patients with B-cell chronic lymphocytic leukemia (CLL)., Patients and Methods: Five hundred fifty-four previously untreated CLL patients with intermediate/high-risk Rai-stage disease were enrolled onto an intergroup protocol. Patients were randomized to therapy with chlorambucil, fludarabine, or fludarabine plus chlorambucil. Data pertaining to infection were available on 518 patients. Differences in infections among treatment arms were tested with the Kruskal-Wallis, Wilcoxon, and chi(2) tests., Results: A total of 1,107 infections (241 major infections) occurred in 518 patients over the infection follow-up period (interval from study entry until either reinstitution of initial therapy, therapy with a second agent, or death). Patients treated with fludarabine plus chlorambucil had more infections than those receiving either single agent (P <.0001). Comparing the two single-agent arms, there were more infections on the fludarabine arm (P =.055) per month of follow-up. Fludarabine therapy was associated with more major infections and more herpesvirus infections compared with chlorambucil (P =.008 and P =.004, respectively). Rai stage and best response to therapy were not associated with infection. A low serum immunoglobulin G was associated with number of infections (P =.02). Age was associated with incidence of major infection in the combination arm (P =.004)., Conclusion: Combination therapy with fludarabine plus chlorambucil resulted in significantly more infections than treatment with either single agent. Patients receiving single-agent fludarabine had more major infections and herpesvirus infections compared with chlorambucil-treated patients.

The OVX1 tumor marker promises to complement CA125 for detection of early stage ovarian carcinoma. OVX1 has also been shown to be elevated in colon cancer patients. This study is designed to assess serum OVX1 levels in patients with specific stages of colon cancer, colon polyps or other GI disorders. Serum OVX1 and CEA were measured by radioimmunoassay or enzyme immunoassay for 206 patients at the time of colonoscopy or staging for colon carcinoma. In patients with stage I, II, III, or IV colon carcinoma, serum OVX1 was positive in 37%, 48%, 74% and 63%, respectively. Fifty-three percent of patients with colon polyps had elevated OVX1 levels, while OVX1 levels were positive in only 7% of healthy controls. If both OVX1 and CEA were considered, at least one of these markers was elevated in 36%, 60%, 79% or 89% of patients with stage I, II, III or IV colon carcinoma, respectively. The majority of patients with inflammatory bowel disease or diverticulosis also had elevated OVX1 levels. Both markers were positive in 27% of patients with colon carcinoma, and not in any patients with a normal colonoscopy or with a diagnosis of diverticulosis or hemorrhoids. In conclusion, serum OVX1 improves the sensitivity of CEA for detecting colon polyps and colon cancer; however, the use of OVX1 in this setting is hindered by its elevation in non-malignant colonic processes.

The steroid hormone 1,25-dihydroxyvitamin D3[1,25-(OH)2D3] induces maturation of many cells, including HL-60 promyelocytic leukemia cells that are differentiated to monocytes/macrophages. This process involves changes in transcription of genes such as c-myc. We investigated the effects of 1,25-(OH)2D3 on nuclear protein binding to the c-myc intron element (MIE), a region of DNA within the c-myc gene. A mutation in this MIE sequence has been shown to be associated with uncontrolled expression of the c-myc gene in various cell lines. In this report, we demonstrate for the first time that 1,25-(OH)2D3 induces increased binding of nuclear proteins to this MIE in HL-60 cells. The major MIE-binding proteins were approximately 32 kDa in size. Interestingly, phorbol 12-myristate 13-acetate induced a similar increase in binding of the 32-kDa doublet protein to the MIE. In addition, we showed that the level of 138-kDa MIE-binding protein was increased by 1,25-(OH)2D3 and phorbol 12-myristate 13-acetate. However, the extent of MIE binding by the 138-kDa protein is significantly less than that of the 32-kDa doublet binding species. MIE binding by the 32-kDa doublet protein was significantly increased within 12 h of 1,25-(OH)2D3 treatment. The time course of this increase was similar to that of 1,25-(OH)2D3-induced inhibition of c-myc gene transcription. We also demonstrated that dephosphorylation of the 32-kDa doublet protein inhibited its binding to the MIE. Thus, this study shows that the mechanism employed by 1,25-(OH)2D3 for regulation of c-myc expression may involve an increase in protein binding to the MIE, which has been shown to be the site for control of c-myc gene expression.

1,25-Dihydroxyvitamin D3 (1,25-(OH)2D3)-induced differentiation of HL-60 leukemia cells is accompanied by a number of cellular changes including regulation of oncogene expression and induction of terminal differentiation. We investigated the mechanism by which 1,25-(OH)2D3 induces these changes. We detected 10 nuclear phosphoproteins, designated p66, p45, p36, p33, p32, p27, p22, p19, p18 and p17, that show alterations in phosphorylation within 6-40 h of 1,25-(OH)2D3 treatment. When phosphorylation reactions were performed with isolated nuclei (in vitro), three of these proteins were phosphorylated in a calcium and phospholipid dependent manner: p66, p36, and p19 P66 was phosphorylated in response to 1,25-(OH)2D3 and purified in a manner similar to that used for nuclear lamins. Western blot analysis of 2-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) gels confirmed its identity as lamin B. Phosphorylation of p17 and p18 decreased following 1,25-(OH)2D3 treatment. We separated p17 and p18 by SDS-PAGE and obtained N-terminal amino acid sequence to identify these phosphorproteins as histones H2b and H3, respectively. P19 and p22 were both DNA-cellulose binding proteins whose phosphorylation was altered by 1,25-(OH)2D3 treatment. Increased phosphorylation of p27 was detected using 2-dimensional SDS-PAGE. Phosphorylation of nuclear proteins in the intact cell (in vivo), revealed increases in p66, p45, p36, and p33 phosphorylation and a decrease in p17 phosphorylation following 1,25-(OH)2D3 treatment. We detected an increase in phosphorylation of p32, which was extracted with salt from nuclei and migrated on SDS-PAGE similar to histone H1. Thus, we have identified 1,25-(OH)2D3-sensitive nuclear phosphoproteins, including lamin B and several histones. We have also detected and characterized several less abundant nuclear DNA binding phosphoproteins whose phosphorylation was affected by 1,25-(OH)2D3.

Although the biosynthesis and secretion of hCG by both normal and neoplastic trophoblasts have been documented, the regulation of these events is not well understood. We have used the JAR choriocarcinoma cell line to study the biosynthesis and secretion of this hormone. Using immunofluorescence, we have determined that less than 5% of cells expressed detectable hCG at a given time, and about 30% of hCG-producing cells were morphologically differentiated. Treatment of the cells with 8-bromoadenosine produced a 2- to 5-fold increase in hCG synthesis and secretion and increased the number of cells expressing hCG by 4- to 6-fold, without altering the percentage of morphologically differentiated cells expressing hCG. The effect on hCG biosynthesis was dose dependent and was induced maximally with a 24-h exposure to 8-bromoadenosine. However, exposure of JAR cells to 8-bromoadenosine for 2 to 6 h was sufficient to initiate a response. Treatment of JAR cells with the adenosine A2-receptor agonist N-ethylcarboxamidoadenosine did not induce hCG biosynthesis. The effect of 8-bromoadenosine on hCG synthesis did, however, parallel the dose-effect curve for inhibition of thymidine incorporation and for decreased cell proliferation. We conclude that induction of hCG biosynthesis by 8-bromoadenosine occurs by inhibiting trophoblast cell proliferation, rather than by an adenosine receptor-mediated event. The observed increase in hCG production may be due to induction of an intermediate differentiated cell type or an increase in the number of cells in an hCG-producing cell cycle phase.

Analogues of diacylglycerol containing a 3-(3-amino-2,4,6-triiodophenyl)-2-ethylpropanoyl or 3-(3-amino-2,4,6-triiodophenyl)propanoyl group in the 2-position (1a and 1b, respectively) were synthesized and shown to compete with [3H]phorbol dibutyrate [( 3H]PDBu) for binding in a crude rat brain preparation. Phorbol diesters have been shown to bind specifically to protein kinase C and the PDBu receptor has been copurified with protein kinase C activity. The four diastereomers of 1a (1c-f) were synthesized from chiral starting material and studied in the same assay. The affinities for the [3H]PDBu binding site of 1a, 1b, and two isomers of 1a with naturally occurring L configuration were comparable to that of 1-oleoyl-2-acetyl-rac-glycerol (OAG), but the D isomers of 1a were essentially inactive. The chirality of the side chain did not influence the binding affinity. Activation of protein kinase C by 1a, 1c, and 1e demonstrated the same stereochemical requirements, but none were as active as OAG. For the 1,3-isomers 2, 2a, and 2b, the competitive binding studies gave different results. The racemic mixture and the D isomer, 2b, were able to compete for binding, but the L isomer, 2a, did not compete. These studies demonstrate that diacylglycerol binding to and activation of protein kinase C is stereospecific for the glycerol backbone, but not the side chain. Furthermore, the D-1,3-isomer must exist in a conformation such that the acyl and hydroxyl oxygens assume a spatial relationship similar to that in the L-1,2-isomers.

Analogues of dioctanoylglycerol (diC8) and 1-oleoyl-2-acetylglycerol (OAG) containing an iodoaryl group have been synthesized and shown to compete with [3H]phorbol dibutyrate [( ([3H]PDBu) for binding to protein kinase C in a crude rat brain preparation. Phorbol diesters have been shown to bind specifically to protein kinase C and the PDBu receptor has been copurified with protein kinase C activity. All three diacylglycerol analogues were comparable to OAG in binding affinity. In an assay of protein kinase C activation, the diC8 analogue was more active than the OAG analogues, thus demonstrating greater structural specificity under the conditions of this assay.

In this study the relationship between cell binding of phorbol 12,13-dibutyrate (PDBu) and induction of differentiation by 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) was examined. Binding of [3H]PDBu increased within 12 h of 1,25-(OH)2D3 treatment, and a 60-130% increase in [3H]PDBu receptor levels was observed within 24 h. By 48 h, however, [3H]PDBu binding was not different from control. Scatchard analysis of [3H]PDBu binding showed no statistical differences in Kd value (Kd approximately equal to 30 nM) between 1,25-(OH)2D3-treated and control cells 22 h post-treatment; however, a 2-fold increase in Bmax was observed in treated (338 +/- 24 pmol/10(9) cells) compared to control cultures (170 +/- 14 pmol/10(9) cells). Stimulation of [3H]PDBu binding was dependent on 1,25-(OH)2D3 concentrations over a range of 1-100 nM. Homogenates from 1,25-(OH)2D3-treated HL-60 cells also demonstrated an increase (70%) in [3H]PDBu binding to the Ca2+/phospholipid-dependent enzyme protein kinase C as assessed by incubation of cell homogenates with [3H]PDBu in the presence of saturating phosphatidylserine and calcium concentrations. This suggests that the increase in [3H]PDBu binding cannot be entirely explained by modulation of the latter two agents. Cycloheximide (5 microM), an inhibitor of protein synthesis, ablated the 1,25-(OH)2D3-stimulated increase in [3H]PDBu binding to intact HL-60 cells. These data demonstrate that an increase in [3H]PDBu binding occurs early in the course of 1,25-(OH)2D3-induced differentiation, results from an increased number of [3H]PDBu-binding site, and is dependent on protein synthesis.

HL-60 promyelocytic leukemia cells were induced to differentiate by 1,25-dihydroxyvitamin D3 (calcitriol) into mature monocytes. Differentiation was assessed by nitro blue tetrazolium dye reduction, nonspecific esterase activity, and DNA synthesis. Terminal differentiation of cultures induced by calcitriol (10 nM) was inhibited by 80% when cells were treated simultaneously with protein kinase inhibitors 1-(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride (H-7) (32 microM) and N-[2-guanidinoethyl]-5-isoquinolinesulfonamide hydrochloride (HA1004) (320 microM). The IC50 for inhibition of calcitriol-induced differentiation was approximately 15 microM for H-7 and 170 microM for HA1004. The IC50 values for H-7 and HA1004 antagonism of calcitriol-induced differentiation are quantitatively and relatively correlated to their known action to inhibit protein kinase C activity. Treatment of cells with concentrations of 0-32 microM H-7 or 0-320 microM HA1004 alone did not affect cell growth, differentiation, or trypan blue exclusion. However, higher concentrations of H7 (greater than 32 microM) and HA1004 (greater than 320 microM) were found to be cytotoxic. The data presented suggest that calcitriol-induced differentiation is antagonized by inhibitors of protein kinase and are consistent with the hypothesis that kinase C activity is required for HL-60 cell differentiation.