Search

Supplemental Figure 3. Mean (SD) TIRA plasma concentration. Cycle 1 Day 8 data are shown in patients receiving TIRA monotherapy with A) TIRA/IDELA, and B) TIRA/ENTO*

Supplemental Table 1 summarizes study inclusion and exclusion criteria. Supplemental Table 2 shows the doses and dose-escalation strategy used in this study. Supplemental Table 3 defines the dose-limiting toxicities that guided dose escalation. Supplemental Table 4 lists the number of patients by disease in the dose expansion phase. Supplemental Table 5 summarizes study drug exposure. Supplemental Table 6 lists TEAEs and laboratory abnormalities of interest that occurred during the study. Supplemental Table 7 shows responders and nonresponders according to biomarker risk groups. Supplemental Table 8 shows best overall response and gene aberration status as measured by FISH and NGS. Supplemental Table 9 provides tirabrutinib peak plasma concentrations. Supplemental Table 10 summarizes tirabrutinib, idelalisib, and entospletinib plasma exposure (AUC) and maximum plasma concentrations (Cmax). Supplemental Table 11 shows patients with free BTK below the lower limit of quantitation. Supplemental Figure 1 graphically illustrates the design of the study. Supplemental Figure 2 illustrates the disposition of patients over the course of the study. Supplemental Figure 3 shows line graphs illustrating tirabrutinib plasma concentrations over time. Supplemental Figure 4 shows box plots representing BTK levels at baseline and trough tirabrutinib concentrations.

Acquired and intrinsic resistance still remains a limitation to the clinical use of 5-fluorouracil (5-FU). The contribution of epigenetic changes to the development of drug resistance remains to be elucidated. Several genes that are hypermethylated and silenced have been identified in colorectal cancer. Based on the findings described in the accompanying article, we hypothesized that acquired resistance to “pulse” 5-FU has an epigenetic origin and might be reversed. Here, we present a novel therapeutic approach to circumvent clinical resistance to bolus 5-FU, that is, treatment of bolus 5-FU-resistant colorectal cancer cells with low-dose 5-azadeoxycytidine (DAC), an inhibitor of DNA hypermethylation, restored sensitivity to 5-FU as well as 5-fluorouridine. Moreover, treatment of nude mice bearing a 5-FU-resistant tumor, characterized by decreased levels of UMP kinase (UMPK), with DAC overcame resistance to bolus 5-FU. DAC-mediated restoration of 5-FU sensitivity was associated with increases in UMPK levels. An increase in UMPK protein and mRNA levels following treatment with low-dose DAC was observed in cultured bolus 5-FU-resistant colorectal cancer cells (HCT-8) and in mice bearing these tumors. We conclude that DAC-mediated restoration of sensitivity to bolus 5-FU is mediated at least in part by increased UMPK levels and clinical resistance to 5-FU due to decreased UMPK in colorectal cancer may be overcome by including methylation inhibitors such as DAC. [Mol Cancer Ther 2009;8(5):1045–54]

5-Fluorouracil (5-FU) continues to be widely used for treatment of gastrointestinal cancers. Because many tumors show primary or acquired resistance, it is important to understand the molecular basis underlying the mechanism of resistance to 5-FU. In addition to its effect on thymidylate synthase inhibition and DNA synthesis, 5-FU may also influence RNA metabolism. Our previous studies revealed that colorectal cancer cells resistant to bolus 5-FU (HCT-8/4hFU) showed significantly decreased incorporation of the drug into RNA. Resistance to bolus 5-FU was associated with lower expression of UMP kinase (UMPK), an enzyme that plays an important role in the activation of 5-FU to 5-FUTP and its incorporation into RNA. Activities of other 5-FU–metabolizing enzymes (e.g., thymidine kinase, uridine phosphorylase, thymidine phosphorylase, and orotate phosphoribosyltransferase) remained unchanged between sensitive and resistant cell lines. Herein, we show that UMPK down-regulation in 5-FU–sensitive cells (HCT-8/P) induces resistance to bolus 5-FU treatment. Moreover, HCT-8/4hFU cells are even more cross-resistant to treatment with 5-fluorouridine, consistent with the current understanding of 5-fluorouridine as a RNA-directed drug. Importantly, colorectal cancer hepatic metastases isolated from patients clinically resistant to weekly bolus 5-FU/leucovorin treatment exhibited decreased mRNA expression of UMPK but not thymidylate synthase or dihydropyrimidine dehydrogenase compared with tumor samples of patients not previously exposed to 5-FU. Our findings provide new insights into the mechanisms of acquired resistance to 5-FU in colorectal cancer and implicate UMPK as an important mechanism of clinical resistance to pulse 5-FU treatment in some patients.[Mol Cancer Ther 2009;8(4):OF1–8]

Supplementary Fig. from Epigenetic reversal of acquired resistance to 5-fluorouracil treatment

Supplementary Fig. from Decreased levels of UMP kinase as a mechanism of fluoropyrimidine resistance

Supplemental Figure 2. Patient disposition

Purpose:Bruton tyrosine kinase (BTK) inhibition alone leads to incomplete responses in chronic lymphocytic leukemia (CLL). Combination therapy may reduce activation of escape pathways and deepen responses. This open-label, phase Ib, sequential dose-escalation and dose-expansion study evaluated the safety, tolerability, pharmacokinetics, and preliminary efficacy of the selective BTK inhibitor tirabrutinib alone, in combination with the PI3K delta (PI3Kδ) inhibitor idelalisib, or with the spleen tyrosine kinase (SYK) inhibitor entospletinib in patients with relapsed/refractory CLL.Patients and Methods:Patients received either tirabrutinib monotherapy (80 mg every day) or tirabrutinib 20–150 mg every day in combination with either idelalisib (50 mg twice a day or 100 mg every day) or entospletinib (200 mg or 400 mg every day).Results:Fifty-three patients were included. Systemic tirabrutinib exposure was comparable between monotherapy and combination therapy. No MTD was identified. Across all treatment groups, the most common adverse event was diarrhea (43%, 1 patient grade ≥3); discontinuation due to adverse events was uncommon (13%). Objective response rates were 83%, 93%, and 100%, and complete responses were 7%, 7%, and 10% in patients receiving tirabrutinib, tirabrutinib/idelalisib, and tirabrutinib/entospletinib, respectively. As of February 21, 2019, 46 of 53 patients continue to receive treatment on study.Conclusions:Tirabrutinib in combination with idelalisib or entospletinib was well tolerated in patients with CLL, establishing an acceptable safety profile for concurrent selective inhibition of BTK with either PI3Kδ or SYK. This small study did not establish a superior efficacy of the combinations over tirabrutinib alone. This trial is registered at www.clinicaltrials.gov (NCT02457598).

Supplementary Data from Carcinoma-Associated Fibroblast–Like Differentiation of Human Mesenchymal Stem Cells

Remdesivir (RDV, Veklury®) is a once-daily, nucleoside ribonucleic acid polymerase inhibitor of severe acute respiratory syndrome coronavirus 2 replication. Remdesivir has been granted approvals in several countries for use in adults and children hospitalized with severe coronavirus disease 2019 (COVID-19). Inside the cell, remdesivir undergoes metabolic activation to form the intracellular active triphosphate metabolite, GS-443902 (detected in peripheral blood mononuclear cells), and ultimately, the renally eliminated plasma metabolite GS-441524. This review discusses the pre-clinical pharmacology of RDV, clinical pharmacokinetics, pharmacodynamics/concentration-QT analysis, rationale for dose selection for treatment of patients with COVID-19, and drug–drug interaction potential based on available in vitro and clinical data in healthy volunteers. Following single-dose intravenous administration over 2 h of an RDV solution formulation across the dose range of 3–225 mg in healthy participants, RDV and its metabolites (GS-704277and GS-441524) exhibit linear pharmacokinetics. Following multiple doses of RDV 150 mg once daily for 7 or 14 days, major metabolite GS-441524 accumulates approximately 1.9-fold in plasma. Based on pharmacokinetic bridging from animal data and available human data in healthy volunteers, the RDV clinical dose regimen of a 200-mg loading dose on day 1 followed by 100-mg maintenance doses for 4 or 9 days was selected for further evaluation of pharmacokinetics and safety. Results showed high intracellular concentrations of GS-443902 suggestive of efficient conversion from RDV into the triphosphate form, and further supporting this clinical dosing regimen for the treatment of COVID-19. Mathematical drug–drug interaction liability predictions, based on in vitro and phase I data, suggest RDV has low potential for drug–drug interactions, as the impact of inducers or inhibitors on RDV disposition is minimized by the parenteral route of administration and extensive extraction. Using physiologically based pharmacokinetic modeling, RDV is not predicted to be a clinically significant inhibitor of drug-metabolizing enzymes or transporters in patients infected with COVID-19 at therapeutic RDV doses. Supplementary Information The online version contains supplementary material available at 10.1007/s40262-021-00984-5.

Remdesivir (RDV), a single diastereomeric monophosphoramidate prodrug that inhibits viral RNA polymerases, has potent in vitro antiviral activity against severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2). RDV received the US Food and Drug Administration (FDA)'s emergency use authorization in the United States and approval in Japan for treatment of patients with severe coronavirus disease 2019 (COVID-19). This report describes two phase I studies that evaluated the safety and pharmacokinetics (PKs) of single escalating and multiple i.v. doses of RDV (solution or lyophilized formulation) in healthy subjects. Lyophilized formulation was evaluated for potential future use in clinical trials due to its storage stability in resource-limited settings. All adverse events were grade 1 or 2 in severity. Overall, RDV exhibited a linear profile following single-dose i.v. administration over 2 hours of RDV solution formulation across the dose range of 3-225 mg. Both lyophilized and solution formulations provided comparable PK parameters. High intracellular concentrations of the active triphosphate (~ 220-fold to 370-fold higher than the in vitro half-maximal effective concentration against SARS-CoV-2 clinical isolate) were achieved following infusion of 75 mg or 150 mg lyophilized formulation over 30 minutes or 2 hours. Following multiple-doses of RDV 150 mg once daily for 7 or 14 days, RDV exhibited a PK profile similar to single-dose administration. Metabolite GS-441524 accumulated ~ 1.9-fold after daily dosing. Overall, RDV exhibited favorable safety and PK profiles that supported once-daily dosing.

Objective Idelalisib is an orally administered, highly selective inhibitor of phosphatidylinositol 3-kinase-δ. In this phase 1b study, the safety, tolerability and pharmacokinetics of idelalisib, an oral inhibitor of phosphatidylinositol 3-kinase-δ, were evaluated in Japanese patients with relapsed or refractory indolent B-cell non-Hodgkin lymphoma. Methods In total, six patients (follicular lymphoma: n = 3, chronic lymphocytic leukemia: n = 3) were enrolled to receive idelalisib 150 mg twice daily. Results No dose-limiting toxicities were reported. The most common adverse events were diarrhea (n = 5), gastritis (n = 3), insomnia (n = 3) and pyrexia (n = 3). The most common ≥grade 3 adverse events were diarrhea (n = 2), increased transaminase levels (n = 2) and decreased appetite (n = 2). The maximum idelalisib plasma concentrations (Cmax) were achieved at 2.50 h (range: 1.50–4.00 h). The mean idelalisib plasma concentrations decreased over time but remained detectable in most patients at 12 h. All enrolled patients underwent efficacy evaluation by investigators, and five patients (follicular lymphoma: n = 2, chronic lymphocytic leukemia: n = 3) achieved partial response. The median duration of partial response was 14.5 months (range: 3.7–31.3 months). Conclusion Idelalisib 150 mg twice daily was considered tolerable in Japanese patients with follicular lymphoma or chronic lymphocytic leukemia. (Clinical trial registration: NCT02242045)

SBECD (Captisol®) with an average degree of substitution of 6.5 sulfobutylether functional groups (SBE = 6.5), is a solubility enhancer for remdesivir (RDV) and a major component in Veklury, which was approved by FDA for the treatment of patients with COVID-19 over 12 years old and weighing over 40 kg who require hospitalization. SBECD is cleared mainly by renal filtration, thus, potential accumulation of SBECD in the human body is a concern for patients dosed with Veklury with compromised renal function. An LC-MS/MS method was developed and validated for specific, accurate, and precise determination of SBECD concentrations in human plasma. In this method, the hexa-substituted species, SBE6, was selected for SBECD quantification, and the mass transition from its dicharged molecular ion [(M-2H)/2]

In their commentary "Single-Cell RNA Sequencing Supports Preferential Bioactivation of Remdesivir in the Liver", Yan and Muller state that two key pieces of data were misrepresented in our recent article titled "Key Metabolic Enzymes in Remdesivir Activation in Human Lung Cells." We would like to thank Yan and Muller for careful review of our publication and would like to address their comments as follows.….

B-cell receptor (BCR) signaling pathway inhibitors (including Bruton’s tyrosine kinase [BTK] inhibitors, and phosphatidylinositol-3 kinase inhibitors [PI3Ki]) have shown clinical efficacy in non-Hodgkin lymphoma (NHL). However, responses to these agents have been limited in depth and duration. This may be due to resistance to PI3Kδ and BTK inhibitors as monotherapy [1,2,3,4,5]. The emergence of resistant clones may be addressed by combining these 2 classes of drugs. Furthermore, tolerability of these drug classes has been a concern. Combination therapy using lower doses of one or more classes of inhibitors may address some limitations.

Tirabrutinib is an irreversible, small-molecule Bruton's tyrosine kinase (BTK) inhibitor, which was approved in Japan (VELEXBRU) to treat B-cell malignancies and is in clinical development for inflammatory diseases. As an application of model-informed drug development, a semimechanistic pharmacokinetic/pharmacodynamic (PK/PD) model for irreversible BTK inhibition of tirabrutinib was developed to support dose selection in clinical development, based on clinical PK and BTK occupancy data from two phase I studies with a wide range of PK exposures in healthy volunteers and in subjects with rheumatoid arthritis. The developed model adequately described and predicted the PK and PD data. Overall, the model-based simulation supported a total daily dose of at least 40 mg, either q.d. or b.i.d., with adequate BTK occupancy (> 90%) for further development in inflammatory diseases. Following the PK/PD modeling and simulation, the relationship between model-predicted BTK occupancy and preliminary clinical efficacy data was also explored and a positive trend was identified between the increasing time above adequate BTK occupancy and better efficacy in treatment for RA by linear regression.

Toll-like receptor 7 (TLR7) agonists, in combination with other therapies, can induce sustained control of simian-human immunodeficiency virus (SHIV) or simian immunodeficiency virus (SIV) in nonhuman primates. Here, we report the results of a randomized, double-blind, placebo-controlled phase 1b clinical trial of an oral TLR7 agonist, vesatolimod, in HIV-1-infected controllers on antiretroviral therapy (ART). We randomized participants 2:1 to receive vesatolimod (n = 17) or placebo (n = 8) once every other week for a total of 10 doses while continuing on ART. ART was then interrupted, and the time to viral rebound was analyzed using the Kaplan-Meier method. Vesatolimod was associated with induction of immune cell activation, decreases in intact proviral DNA during ART, and a modest increase in time to rebound after ART was interrupted. The delayed viral rebound was predicted by the lower intact proviral DNA at the end of vesatolimod treatment (13 days after the final dose). Inferred pathway analysis suggested increased dendritic cell and natural killer cell cross-talk and an increase in cytotoxicity potential after vesatolimod dosing. Larger clinical studies will be necessary to assess the efficacy of vesatolimod-based combination therapies aimed at long-term control of HIV infection.

Remdesivir (RDV) is a phosphoramidate prodrug designed to have activity against a broad spectrum of viruses. Following IV administration, RDV is rapidly distributed into cells and tissues and simultaneously metabolized into GS-441524 and GS-704277 in plasma. LC-MS/MS methods were validated for determination of the 3 analytes in human plasma that involved two key aspects to guarantee their precision, accuracy and robustness. First, instability issues of the analytes were overcome by diluted formic acid (FA) treatment of the plasma samples. Secondly, a separate injection for each analyte was performed with different ESI modes and organic gradients to achieve sensitivity and minimize carryover. Chromatographic separation was achieved on an Acquity UPLC HSS T3 column (2.1 × 50 mm, 1.8 μm) with a run time of 3.4 min. The calibration ranges were 4–4000, 2–2000, and 2–2000 ng/mL, respectively for RDV, GS-441524 and GS-704277. The intraday and interday precision (%CV) across validation runs at 3 QC levels for all 3 analytes was less than 6.6%, and the accuracy was within ±11.5%. The long-term storage stability in FA-treated plasma was established to be 392, 392 and 257 days at −70 °C, respectively for RDV, GS-441524 and GS-704277. The validated method was successfully applied in COVID-19 related clinical studies.

Background Treatment with vesatolimod, an investigational, oral, toll-like receptor 7 (TLR7) agonist, leads to sustained viral remission in some non-human primates when combined with anti-envelope antibodies or therapeutic vaccines. We report results of a Phase Ib study evaluating safety, pharmacokinetics, and pharmacodynamics of vesatolimod in adults living with human immunodeficiency virus (HIV)–1. Methods In this double-blind, multicenter, placebo-controlled trial, participants on antiretroviral therapy with screening plasma HIV-1 RNA levels Results A total of 48 individuals were randomly assigned to vesatolimod (n = 36) or placebo (n = 12). Vesatolimod was generally well tolerated, with no study drug–related serious adverse events or adverse events leading to study drug discontinuation. There were no statistically significant changes from baseline in plasma HIV-1 RNA in the vesatolimod groups, compared to placebo. Vesatolimod plasma exposures increased dose proportionally; consistent responses in cytokines, interferon-stimulated gene expression, and lymphocyte activation were observed with increasing dose levels above 4 mg. Peak elevations 24 hours after receipt of a 6 mg dose were >3.9-fold higher for interferon gamma-induced protein 10 (IP-10), interleukin-1 receptor antagonist (IL-1RA), interferon–inducible T-cell alpha chemoattractant (ITAC) when compared to baseline values. Conclusions Vesatolimod was well tolerated at doses ranging from 1 to 12 mg. Immune stimulation was observed at doses above 4 mg, providing rationale for future combination trials in people living with HIV. Clinical Trials Registration NCT02858401.

© 2018 Elsevier Inc. We evaluated the multitargeted Janus kinase/TRAF family member associated NF-κβ activator (TANK)-binding kinase 1 (TBK1) inhibitor momelotinib combined with trametinib in 21 patients with Kirsten rat sarcoma viral oncogene homolog-mutated non–small-cell lung cancer. The maximum tolerated dose of momelotinib was 150 mg twice daily (insufficient to achieve significant TBK1 inhibition). No patients achieved objective response and the combination did not improve on the activity of single-agent trametinib on the basis of historic data. Introduction: Specific treatment options are lacking for Kirsten rat sarcoma viral oncogene homolog (KRAS)-mutated non–small-cell lung cancer (NSCLC) despite treatment advances in other mutation-driven subgroups. Patients and Methods: In this study we evaluated the multitargeted Janus kinase/TANK-binding kinase 1 (TBK1) inhibitor momelotinib combined with the mitogen/extracellular signal-related kinase (MEK)1/MEK2 inhibitor trametinib in patients with platinum-treated, refractory, metastatic, KRAS-mutated NSCLC. Dose escalations (3 + 3 design) were conducted with momelotinib in combination with trametinib 1.0 mg once daily, then with trametinib in combination with the maximum tolerated dose (MTD) of momelotinib. MTD was determined from dose-limiting toxicity (DLT) during patients' first 28-day cycle. Safety was the primary end point, and efficacy parameters, including disease control rate (DCR) at 8 weeks, were secondary end points. Results: Twenty-one patients were enrolled (median age: 68 years; 14 [66.7%] female). The MTD was momelotinib 150 mg twice daily in combination with trametinib 1.0 mg once daily. DLTs that determined the MTD were increased alanine aminotransferase and fatigue. The most common adverse events of any grade were nausea (n = 14 [66.7%]), diarrhea (n = 11 [52.4%]), and fatigue (n = 11 [52.4%]). The most common Grade ≥3 event was hypoxia (n = 3 [14.3%]). No patients achieved objective response. DCR at 8 weeks was 12 patients (57.1%) (90% confidence interval [CI], 37.2%-75.5%). Median progression-free and overall survival were 3.6 months (90% CI, 2.2-5.6 months) and 7.4 months (90% CI, 4.0-15.3 months), respectively. Maximum momelotinib plasma concentrations were reached 1 to 2 hours after dosing, but were insufficient to achieve significant TBK1 inhibition. Conclusion: The additional use of momelotinib with trametinib does not improve on the activity of single-agent trametinib in KRAS-mutated NSCLC on the basis of historic data.

Purpose: Bruton tyrosine kinase (BTK) inhibition alone leads to incomplete responses in chronic lymphocytic leukemia (CLL). Combination therapy may reduce activation of escape pathways and deepen responses. This open-label, phase Ib, sequential dose-escalation and dose-expansion study evaluated the safety, tolerability, pharmacokinetics, and preliminary efficacy of the selective BTK inhibitor tirabrutinib alone, in combination with the PI3K delta (PI3Kδ) inhibitor idelalisib, or with the spleen tyrosine kinase (SYK) inhibitor entospletinib in patients with relapsed/refractory CLL. Patients and Methods: Patients received either tirabrutinib monotherapy (80 mg every day) or tirabrutinib 20–150 mg every day in combination with either idelalisib (50 mg twice a day or 100 mg every day) or entospletinib (200 mg or 400 mg every day). Results: Fifty-three patients were included. Systemic tirabrutinib exposure was comparable between monotherapy and combination therapy. No MTD was identified. Across all treatment groups, the most common adverse event was diarrhea (43%, 1 patient grade ≥3); discontinuation due to adverse events was uncommon (13%). Objective response rates were 83%, 93%, and 100%, and complete responses were 7%, 7%, and 10% in patients receiving tirabrutinib, tirabrutinib/idelalisib, and tirabrutinib/entospletinib, respectively. As of February 21, 2019, 46 of 53 patients continue to receive treatment on study. Conclusions: Tirabrutinib in combination with idelalisib or entospletinib was well tolerated in patients with CLL, establishing an acceptable safety profile for concurrent selective inhibition of BTK with either PI3Kδ or SYK. This small study did not establish a superior efficacy of the combinations over tirabrutinib alone. This trial is registered at www.clinicaltrials.gov (NCT02457598).

As a nation, we remain vulnerable to threats posed by the intentional or unintentional use of chemical, biological, radiologic, and nuclear agents or emerging infectious diseases. Children represent an at-risk population and are particularly vulnerable to the effects of these agents because of their unique anatomical and physiologic features. Hence, it is imperative that their unique needs be considered and prioritized. In the current article, we highlight the status of medical countermeasure product development for children, with a specific emphasis on the neonatal population. The aim of this article is to discuss the evidence that has been used to support pediatric approval of medical countermeasure products by the US Food and Drug Administration under various regulatory pathways. Understanding the strengths and limitations of the data that support labeling of medical countermeasures for pediatric patients will help guide health care professionals providing care in the event of a chemical, biological, radiologic, and nuclear agent–related incident or emerging infectious disease outbreak.

Homeostasis of hematopoietic stem and progenitor cells is a tightly regulated process. The disturbance of the balance in the hematopoietic progenitor pool can result in favorable conditions for development of diseases such as myelodysplastic syndromes and leukemia. It has been shown recently that mice lacking p15Ink4b have skewed differentiation of common myeloid progenitors toward the myeloid lineage at the expense of erythroid progenitors. The lack of p15INK4B expression in human leukemic blasts has been linked to poor prognosis and increased risk of myelodysplastic syndromes transformation to acute myeloid leukemia. However, the role of p15Ink4b in disease development is just beginning to be elucidated. This study examines the collaboration of the loss of p15Ink4b with Nup98-HoxD13 translocation in the development of hematological malignancies in a mouse model. Here, we report that loss of p15Ink4b collaborates with Nup98-HoxD13 transgene in the development of predominantly myeloid neoplasms, namely acute myeloid leukemia, myeloproliferative disease, and myelodysplastic syndromes. This mouse model could be a very valuable tool for studying p15Ink4b function in tumorigenesis as well as preclinical drug testing.

Developmental processes, like blood formation, are orchestrated by transcriptional networks. Those transcriptional networks are highly responsive to various environmental stimuli and affect common precursors resulting in increased production of cells of the erythroid lineage or myeloid lineage (granulocytes, neutrophils, and macrophages). A significant body of knowledge has accumulated describing transcription factors that drive differentiation of these two major cellular pathways, in particular the antagonistic master regulators such as GATA-1 and PU.1. However, little is known about factors that work upstream of master regulators to enhance differentiation toward one lineage. These functions become especially important under various stress conditions like sudden loss of red blood cells or pathogen infection. This review describes recent studies that begin to provide evidence for such factors. An increased understanding of factors regulating cellular commitment will advance our understanding of the etiology of diseases like anemia, cancer, and possibly other blood related disorders.

5-Fluorouracil (5-FU) continues to be widely used for treatment of gastrointestinal cancers. Because many tumors show primary or acquired resistance, it is important to understand the molecular basis underlying the mechanism of resistance to 5-FU. In addition to its effect on thymidylate synthase inhibition and DNA synthesis, 5-FU may also influence RNA metabolism. Our previous studies revealed that colorectal cancer cells resistant to bolus 5-FU (HCT-8/4hFU) showed significantly decreased incorporation of the drug into RNA. Resistance to bolus 5-FU was associated with lower expression of UMP kinase (UMPK), an enzyme that plays an important role in the activation of 5-FU to 5-FUTP and its incorporation into RNA. Activities of other 5-FU–metabolizing enzymes (e.g., thymidine kinase, uridine phosphorylase, thymidine phosphorylase, and orotate phosphoribosyltransferase) remained unchanged between sensitive and resistant cell lines. Herein, we show that UMPK down-regulation in 5-FU–sensitive cells (HCT-8/P) induces resistance to bolus 5-FU treatment. Moreover, HCT-8/4hFU cells are even more cross-resistant to treatment with 5-fluorouridine, consistent with the current understanding of 5-fluorouridine as a RNA-directed drug. Importantly, colorectal cancer hepatic metastases isolated from patients clinically resistant to weekly bolus 5-FU/leucovorin treatment exhibited decreased mRNA expression of UMPK but not thymidylate synthase or dihydropyrimidine dehydrogenase compared with tumor samples of patients not previously exposed to 5-FU. Our findings provide new insights into the mechanisms of acquired resistance to 5-FU in colorectal cancer and implicate UMPK as an important mechanism of clinical resistance to pulse 5-FU treatment in some patients.[Mol Cancer Ther 2009;8(4):OF1–8]

Recent advances in cancer research showed that changes of the cell "epigenome" contribute significantly to the development and progression of cancer. Similar to genetic alterations, epigenetic modifications can be transmitted to the next generation and used to turn off and/or on certain genes or pathways that may confer survival benefit to a malignant cell. However, epigenetic changes are readily reversible raising the possibility of "epigenetic therapy". A potential problem in this therapeutic approach is the lack of specificity, as epigenetic modifications are used by both normal and cancer cells to regulate expression of various genes. Ongoing studies to identify genes that are differentially expressed in cancer cells vs. normal cells are providing valuable information about molecular targets for epigenetic therapy. The present article will focus on summarizing some of these studies and will discuss the differences between conventional chemotherapy and epigenetic therapy utilizing epigenetic drugs like DNA methyltransferase inhibitors or histone deacetylase inhibitors. Current perspectives on the future of epigenetic therapy are also discussed.

Aplidin (plitidepsin) is a novel marine-derived antitumor agent presently undergoing phase II clinical trials in hematological malignancies and solid tumors. Lack of bone marrow toxicity has encouraged further development of this drug for treatment of leukemia and lymphoma. Multiple signaling pathways have been shown to be involved in Aplidin-induced apoptosis and cell cycle arrest in G1 and G2 phase. However, the exact mechanism(s) of Aplidin action remains to be elucidated. Here we demonstrate that mitochondria-associated or -localized processes are the potential cellular targets of Aplidin. Whole genome gene-expression profiling (GEP) revealed that fatty acid metabolism, sterol biosynthesis and energy metabolism, including the tricarboxylic acid cycle and ATP synthesis are affected by Aplidin treatment. Moreover, mutant MOLT-4, human leukemia cells lacking functional mitochondria, were found to be resistant to Aplidin. Cytosine arabinoside (araC), which also generates oxidative stress but does not affect the ATP pool, showed synergism with Aplidin in our leukemia and lymphoma models in vitro and in vivo. These studies provide new insights into the mechanism of action of Aplidin. The efficacy of the combination of Aplidin and araC is currently being evaluated in clinical phase I/II program for the treatment of patients with relapsed leukemia and high-grade lymphoma.

MicroRNAs are predicted to regulate ≈30% of all human genes by targeting sequences in their 3′ UTR. Polymorphisms in 3′ UTR of several genes have been reported to affect gene expression, but the mechanism is not fully understood. Here, we demonstrate that 829C→T, a naturally occurring SNP, near the miR-24 binding site in the 3′ UTR of human dihydrofolate reductase (DHFR) affects DHFR expression by interfering with miR-24 function, resulting in DHFR overexpression and methotrexate resistance. miR-24 has a conserved binding site in DHFR 3′ UTR. DHFR with WT and 3′ UTR containing the 829C→T mutation were expressed in DG44 cells that lack DHFR. Overexpression of miR-24 in cells with WT DHFR resulted in down-regulation of DHFR protein, whereas no effect on DHFR protein expression was observed in the mutant 3′ UTR-expressing cells. Inhibition of endogenous miR-24 with a specific inhibitor led to up-regulation of DHFR in WT and not in mutant cells. Cells with the mutant 3′ UTR had a 2-fold increase in DHFR mRNA half-life, expressed higher DHFR mRNA and DHFR protein, and were 4-fold more resistant to methotrexate as compared with WT cells. SNP-829C→T, therefore, leads to a decrease in microRNA binding leading to overexpression of its target and results in resistance to methotrexate. We demonstrate that a naturally occurring miRSNP (a SNP located at or near a microRNA binding site in 3′ UTR of the target gene or in a microRNA) is associated with enzyme overproduction and drug resistance.

Cellular effects of novel indolo[2,3-b]quinoline derivatives were studied. These compounds are synthetic analogs of plant alkaloid neocryptolepine (5-methyl1-5H-indolo[2,3-b]quinoline) present in extracts from Cryptolepis sanguinolenta. They are traditionally used in natural medicine in Central and West Africa. Previous molecular and computational studies indicated that these compounds were DNA intercalators and inhibitors of topoisomerase II. We have extended our studies on their mode of action to the cellular level. Past experiments have shown that these compounds were active in vitro against cell lines derived from solid tumors, so for the present studies we selected leukemic cell lines. Jurkat acute T cell, CCRF-CEM T lymphoblastoid, THP-1 acute monocytic, HL-60 acute promyelocytic leukemias, and HL-60/MX2 subline with reduced expression of topoisomerase II were used. We evaluated the cytotoxicity and cell cycle effects of the indolo[2,3-b]quinoline compounds. We also tested if these compounds were able to induce apoptosis in the cells. Our studies revealed that novel indolo[2,3-b]quinoline derivatives were more cytotoxic to all cell lines than etoposide (used as a reference topoisomerase II inhibitor), and that their cytotoxicity depended on the substituents introduced to the indolo[2,3-b]quinoline core. Surprisingly, our studies have shown that HL-60/MX2 cell line and also THP-1 cell line, resistant to etoposide, were susceptible to methyl- and methoxy-substituted indolo[2,3-b]quinoline derivatives. In parallel to the evaluation of cytotoxicity we studied cell cycle effects of these compounds. Treatment of HL-60 cells with etoposide in subcytotoxic concentrations resulted in a massive accumulation of the cells in the G 2 /M phase of the cell cycle. When we used subcytotoxic concentrations of our novel indolo[2,3-b]quinoline derivatives the cell cycle progression of HL-60 cells was not affected. Moreover, the cell cycle of HL-60/MX2 cells was not influenced by any of the compounds studied. Indolo[2,3-b]quinoline derivatives induced apoptosis in HL-60 and HL-60/MX2 cells, but only in concentrations close to IC 50 determined in cytotoxic assays. Etoposide induced apoptosis in HL-60 parental cell line, but in a very broad range of concentrations. Our results suggest that topoisomerase II may not represent the main cellular target for novel indolo[2.3-b]quinoline derivatives. They show that the cells resistant to topoisomerase II poison, etoposide, were still sensitive to our compounds.

Epigenetic silencing of the tumor suppressor gene p15Ink4b (CDKN2B) is a frequent event in blood disorders like acute myeloid leukemia and myelodysplastic syndromes. The molecular function of p15Ink4b in hematopoietic differentiation still remains to be elucidated. Our previous study demonstrated that loss of p15Ink4b in mice results in skewing of the differentiation pattern of the common myeloid progenitor towards the myeloid lineage. Here, we investigated a function of p15Ink4b tumor suppressor gene in driving erythroid lineage commitment in hematopoietic progenitors. It was found that p15Ink4b is expressed more highly in committed megakaryocyte–erythroid progenitors than granulocyte–macrophage progenitors. More importantly, mice lacking p15Ink4b have lower numbers of primitive red cell progenitors and a severely impaired response to 5-fluorouracil- and phenylhydrazine-induced hematopoietic stress. Introduction of p15Ink4b into multipotential progenitors produced changes at the molecular level, including activation of mitogen-activated protein kinase\extracellular signal-regulated kinase (MEK/ERK) signaling, increase GATA-1, erythropoietin receptor (EpoR) and decrease Pu1, GATA-2 expression. These changes rendered cells more permissive to erythroid commitment and less permissive to myeloid commitment, as demonstrated by an increase in early burst-forming unit-erythroid formation with concomitant decrease in myeloid colonies. Our results indicate that p15Ink4b functions in hematopoiesis, by maintaining proper lineage commitment of progenitors and assisting in rapid red blood cells replenishment following stress.

The tumor suppressor p15Ink4b is frequently inactivated by methylation in acute myeloid leukemia and premalignant myeloid disorders. Dendritic cells (DCs) as potent APCs play critical regulatory roles in antileukemic immune responses. In the present study, we investigated whether p15Ink4b can function as modulator of DC development. The expression of p15Ink4b is induced strongly during differentiation and activation of DCs, and its loss resulted in significant quantitative and qualitative impairments of conventional DC (cDC) development. Accordingly, ex vivo–generated BM-derived DCs from p15Ink4b-knockout mice express significantly decreased levels of the antigen-presenting (MHC II) and costimulatory (CD80 and CD86) molecules and have impaired immunostimulatory functions, such as antigen uptake and T-cell stimulation. Reexpression of p15Ink4b in progenitors restored these defects, and confirmed a positive role for p15Ink4b during cDC differentiation and maturation. Furthermore, we have shown herein that p15Ink4b expression increases phosphorylation of Erk1/Erk2 kinases, which leads to an elevated activity of the PU.1 transcription factor. In conclusion, our results establish p15Ink4b as an important modulator of cDC development and implicate a novel function for this tumor suppressor in the regulation of adaptive immune responses.

MicroRNAs (miRNAs) are predicted to regulate approximately 30% of all human genes; however, only a few miRNAs have been assigned their targets and specific functions. Here we demonstrate that miR-24, a ubiquitously expressed miRNA, has an anti-proliferative effect independent of p53 function. Cell lines with differential p53 status were used as a model to study the effects of miR-24 on cell proliferation, cell cycle control, gene regulation and cellular transformation. Overexpression of miR-24 in six different cell lines, independent of p53 function, inhibited cell proliferation and resulted in G2/S cell cycle arrest. MiR-24 over expression in cells with wt-p53 upregulated TP53 and p21 protein; however, in p53-null cells miR-24 still induced cell cycle arrest without the involvement of p21. We show that miR-24 regulates p53-independent cellular proliferation by regulating an S-phase enzyme, dihydrofolate reductase (DHFR) a target of the chemotherapeutic drug methotrexate (MTX). Of interest, we found that a miR-24 target site polymorphism in DHFR 3′ UTR that results in loss of miR-24-function and high DHFR levels in the cell imparts a growth advantage to immortalized cells and induces neoplastic transformation. Of clinical significance, we found that miR-24 is deregulated in human colorectal cancer tumors and a subset of tumors has reduced levels of miR-24. A novel function for miR-24 as a p53-independent cell cycle inhibitory miRNA is proposed.

Acquired and intrinsic resistance still remains a limitation to the clinical use of 5-fluorouracil (5-FU). The contribution of epigenetic changes to the development of drug resistance remains to be elucidated. Several genes that are hypermethylated and silenced have been identified in colorectal cancer. Based on the findings described in the accompanying article, we hypothesized that acquired resistance to “pulse” 5-FU has an epigenetic origin and might be reversed. Here, we present a novel therapeutic approach to circumvent clinical resistance to bolus 5-FU, that is, treatment of bolus 5-FU-resistant colorectal cancer cells with low-dose 5-azadeoxycytidine (DAC), an inhibitor of DNA hypermethylation, restored sensitivity to 5-FU as well as 5-fluorouridine. Moreover, treatment of nude mice bearing a 5-FU-resistant tumor, characterized by decreased levels of UMP kinase (UMPK), with DAC overcame resistance to bolus 5-FU. DAC-mediated restoration of 5-FU sensitivity was associated with increases in UMPK levels. An increase in UMPK protein and mRNA levels following treatment with low-dose DAC was observed in cultured bolus 5-FU-resistant colorectal cancer cells (HCT-8) and in mice bearing these tumors. We conclude that DAC-mediated restoration of sensitivity to bolus 5-FU is mediated at least in part by increased UMPK levels and clinical resistance to 5-FU due to decreased UMPK in colorectal cancer may be overcome by including methylation inhibitors such as DAC. [Mol Cancer Ther 2009;8(5):1045–54]

Calcitriol, the hormonal form of vitamin D3, induces differentiation of monocytic leukemia cell lines in vitro, without inducing cytotoxicity of the cells. Besides this broad in vitro activity, a clinical implementation of calcitriol, or its analogs, as agents for differentiation therapy has been unsuccessful until now. A better understanding of cellular activities of calcitriol necessary for completion of cell differentiation program could help find better solutions for differentiation therapy of myeloid leukemias. In this paper we describe work carried on subline of acute monocytic leukemia, THP-1 resistant to calcitriol induced differentiation. This resistance correlates with impaired nuclear localization of vitamin D receptor, but not with its total expression in the cells. It also correlates with the resistance to calcitriol-induced growth inhibition, and to phorbol myristate acetate (PMA)-induced cell differentiation.

Red blood cells (RBCs) are a vital component of mammalian blood. Since they are short lived, they must be continuously replenished by erythropoiesis, a stepwise commitment of blood stem and progenitor cells to mature erythrocytes. The anemia due to the loss of RBC is a life threatening condition, often accompanying blood diseases such as leukemias and myelodysplastic syndromes (MDS). A striking 60-80% of these diseases have deleted or silenced expression of p15INK4B. An increased understanding of the factors that drive erythroid lineage commitment in progenitor cells is critical for developing new treatments for blood disorders. Previous examination of p15Ink4b knock-out mouse models, revealed skewing of hematopoietic progenitor differentiation towards myeloid lineage (granulocytes, macrophages). Here, we demonstrate a novel function for p15Ink4b in driving commitment to the erythroid lineage. Mice lacking p15Ink4b have lower numbers of primitive RBC progenitors and died shortly after induction of hemolytic anemia by phenylhydrazine injection. Expression of p15Ink4b in blood progenitors induced dynamic changes at the molecular level that rendered multi-lineage cells more permissive to erythroid commitment and less permissive to myeloid commitment. Noticeably, we found that p15Ink4b regulates a switch that controls the balance between myeloid and erythroid differentiation through activation of MEK/ERK signaling. In a time-coordinated manner expression of p15Ink4b induced rapid phosphorylation of MEK/ERK that led to rapid degradation of GATA-2 and activation of the GATA-1 transcription factors. Subsequently, the active GATA-1 executed lineage commitment through activation of the Erythropoietin receptor (EpoR), the “master regulator” of erythroid differentiation. The p15Ink4b mediated increase in GATA-1 expression, also resulted in decreased expression of the myeloid specific transcription factor PU.1, suppressing myeloid differentiation. In summary, we have defined a framework that determines how multipotent progenitors coordinate the balance between myeloid and erythroid differentiation. Central to this activity is p15Ink4b, which promotes erythroid fate while suppressing myeloid cell formation, a function that is particularly important in rapid RBC replenishment following stress. Our finding has implications not only for MDS and myeloid leukemia, where loss of tumor suppressor p15INK4B is a common event, but also for other forms of human refractory anemia. Citation Format: Rita Humeniuk, Michael Rosu-Myles, Linda Wolff. Tumor suppressor p15Ink4b determines cell fate of hematopoietic progenitors: Implications for development of human blood disorders. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1973. doi:10.1158/1538-7445.AM2013-1973