FOXO1 cooperates with C/EBPδ and ATF4 to regulate skeletal muscle atrophy transcriptional program during fasting.

Catabolic conditions, such as starvation, inactivity, and cancer cachexia, induce Forkhead box O (FOXO) transcription factor(s) expression and severe muscle atrophy via the induction of ubiquitin-proteasome system-mediated muscle proteolysis, resulting in frailty and poor quality of life. Although FOXOs are clearly essential for the induction of muscle atrophy, it is unclear whether there are other factors involved in the FOXO-mediated transcriptional regulation. As such, we identified FOXO-CCAAT/enhancer-binding protein δ (C/EBPδ) signaling pathway as a novel proteolytic pathway. By comparing the gene expression profiles of FOXO1-transgenic (gain-of-function model) and FOXO1,3a,4-/- (loss-of-function model) mice, we identified several novel FOXO1-target genes in skeletal muscle including Redd1, Sestrin1, Castor2, Chac1, Depp1, Lat3, as well as C/EBPδ. During starvation, C/EBPδ abundance was increased in a FOXOs-dependent manner. Notably, knockdown of C/EBPδ prevented the induction of the ubiquitin-proteasome system and decrease of myofibers in FOXO1-activated myotubes. Conversely, C/EBPδ overexpression in primary myotubes induced myotube atrophy. Furthermore, we demonstrated that FOXO1 enhances the promoter activity of target genes in cooperation with C/EBPδ and ATF4. This research comprehensively identifies novel FOXO1 target genes in skeletal muscle and clarifies the pathophysiological role of FOXO1, a master regulator of skeletal muscle atrophy.

A combination of exercise and calorie restriction improves the development of obesity-related type 2 diabetes mellitus in KKAy mice.

We observed that exercise and calorie restriction reduced the body weight and blood glucose levels, concurrently improving insulin resistance and glucose tolerance in obese/diabetic model KKAy mice. Analysis of gene expression in the skeletal muscle showed enhanced mRNA levels of GLUT4 (glucose uptake), ATGL (lipolytic enzyme), and slow-twitch myosin heavy chain, which may contribute to the antiobesity and antidiabetic effects.

A Polyimide Film-Based Simple Force Plate for Measuring the Body Mass of Tiny Insects.

Insects exhibit excellent maneuvers such as running and flying despite their small bodies; therefore, their locomotion mechanism is expected to provide a design guideline for micromachines. Numerical simulations have been performed to elucidate this mechanism, whereby it is important to develop a model that is physically identical to the target insect's parts to reproduce kinematic dynamics. In particular, in flight, the shape and mass of wings, which flap at high frequencies, are significant parameters. However, small insects such as fruit flies have small, thin, and light wings; thus, their mass cannot be easily measured. In this study, we proposed a high-resolution and simple force plate to measure the mass of each part of a tiny insect. The device consists of a circular plate supported by flat spiral springs made of polyimide film, and a laser displacement meter that detects the displacement of the center of the plate. The simple plate fabrication process requires only a couple of minutes. A fabricated force plate with a sub-N/m spring constant achieved a resolution of less than 2 µg. As a demonstration, the wing mass of the fruit flies was measured. The experimental results suggest that the wings accounted for approximately 0.4% of the body mass.

Metabolomic analysis on blood of transgenic mice overexpressing PGC-1α in skeletal muscle.

PGC-1α expression increases in skeletal muscles during exercise and regulates the transcription of many target genes. In this study, we conducted a metabolomic analysis on the blood of transgenic mice overexpressing PGC-1α in its skeletal muscle (PGC-1α-Tg mice) using CE-TOFMS. The blood level of homovanillic acid (dopamine metabolite) and the gene expression of dopamine metabolic enzyme in the skeletal muscle of PGC-1α-Tg mice were high. The blood level of 5-methoxyindoleacetic acid was also high in PGC-1α-Tg mice. The blood levels of branched-chain α-keto acids and ß-alanine were low in PGC-1α-Tg mice. These metabolites in the skeletal muscle were present in low concentration. The changes in these metabolites may reflect the skeletal muscle condition with increasing PGC-1α, such as exercise.

Osimertinib-Associated Toxic Epidermal Necrolysis in a Lung Cancer Patient Harboring an EGFR Mutation-A Case Report and a Review of the Literature.

Toxic epidermal necrolysis (TEN) and Stevens-Johnson syndrome (SJS) are life-threatening dermatologic adverse events in the same category, caused by a delayed-type drug hypersensitivity reaction. Although skin toxicity is common during treatment with epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs), osimertinib-associated TEN is quite rare-thus far, only one report has been published from China. We report a case of an 80-year-old Japanese woman with lung adenocarcinoma harboring an EGFR-sensitizing mutation who was treated with osimertinib as the first-line treatment. Forty-six days after osimertinib induction, diffuse erythematous rash rapidly spread over the patient's trunk along with vesicles and purpuric macules; furthermore, she developed targetoid erythema on the face. Despite osimertinib discontinuation and corticosteroid treatment, diffuse erythema with Nikolsky's sign, general epidermal detachment, erosion and loose blisters developed over her entire body including the face. Based on her symptoms, TEN was diagnosed and thus, intravenous immunoglobulin was immediately administered for 4 days. The treatment ameliorated TEN-associated skin toxicity and caused epithelialization. Reports on osimertinib-associated SJS/TEN are scarce and only one report each on SJS and TEN from China is available. This is the first report of osimertinib-associated TEN from Japan. Cases of EGFR-TKI-associated SJS/TEN have been reported predominantly from Asian countries, suggesting ethnicity and genetic linkage play a role in the underlying mechanism.

Carboxylated phytosterol derivative-introduced liposomes for skin environment-responsive transdermal drug delivery system.

Transdermal drug delivery systems are a key technology for skin-related diseases and for cosmetics development. The delivery of active ingredients to an appropriate site or target cells can greatly improve the efficacy of medical and cosmetic agents. For this study, liposome-based transdermal delivery systems were developed using pH-responsive phytosterol derivatives as liposome components. Succinylated phytosterol (Suc-PS) and 2-carboxy-cyclohexane-1-carboxylated phytosterol (CHex-PS) were synthesized by esterification of hydroxy groups of phytosterol. Modification of phytosterol derivatives on 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) liposomes was confirmed by negatively zeta potentials at alkaline pH and the change of zeta potentials with decreasing pH. In response to acidic pH and temperatures higher than body temperature, Suc-PS-containing and CHex-PS-containing liposomes exhibited content release at intracellular acidic compartments of the melanocytes at the basement membrane of the skin. Phytosterol-derivative-containing liposomes were taken up by murine melanoma-derived B16-F10 cells. These liposomes delivered their contents into endosomes and cytosol of B16-F10 cells. Furthermore, phytosterol-derivative-containing liposomes penetrated the 3 D skin models and reached the basement membrane. Results show that pH-responsive phytosterol-derivative-containing DMPC liposomes are promising for use in transdermal medical or cosmetic agent delivery to melanocytes.

Effective chemomobilization with etoposide and cytarabine (EC regimen) in lymphoma patients: a single-center, retrospective, observational study.

Objective: Autologous stem cell transplantation is an important strategy for patients with relapsed or refractory lymphoma. Although various regimens for peripheral blood stem cell collection have been used, the optimal regimen has not yet been established. We aimed to evaluate the mobilization efficacy and safety of the regimen consisted of etoposide and cytarabine (EC regimen). Methods: We retrospectively analyzed the clinical data of 46 lymphoma patients who received peripheral blood stem cell mobilization with the EC regimen [etoposide (100 mg/m2/day, days 1-4) and cytarabine (100 mg/m2/day, days 1-4)] at Toyohashi municipal hospital from 2004 to 2013. Results: The median age of the patients was 55 years. The most common underlying diseases were diffuse large B-cell lymphoma (46%) and follicular lymphoma (26%). Three-quarters of patients were in their second complete or partial remission. The median total number of collected CD34+ cells was 10.6 × 106 kg-1. Forty-two patients (91%) yielded at least 2 × 106 kg-1 CD34+ cells within a median of 2 apheresis days, and 33 patients (72%) achieved it with only one apheresis. Successful mobilization was observed in five of six patients who failed to mobilize previously. Although febrile neutropenia occurred in 22 patients (48%), no fatal infection was observed. Conclusion: The EC regimen was highly effective in lymphoma patients, including patients who mobilized poorly with other regimens.

PAMAM Dendron Lipid Assemblies That Undergo Structural Transition in Response to Weakly Acidic pH and Their Cytoplasmic Delivery Capability.

Dendron lipids designed to consist of amine-terminated polyamidoamine G1 dendron and two octadecyl chains were used for the preparation of pH-responsive molecular assemblies having phase structures that are changed through their dynamic molecular shape. The dendron lipid contains two primary amines and two tertiary amines in the dendron moiety, changing its charged state in the pH region between pH 10 and pH 4. The assemblies were shown to take a vesicle structure at neutral and alkaline pHs, but their structure changed to a micelle-like structure below pH 6.4. Because this pH region corresponds to one in which tertiary amines of the dendron lipid became protonated, protonation of tertiary amines in addition to primary amines in the dendron moiety might affect its dynamic molecular shape, resulting in a sharp pH response of the assemblies. The assemblies tended to form aggregates when taking on a vesicle form with a gel phase, but incorporation of a poly(ethylene glycol)-lipid provided dendron lipid vesicles with both sharp pH response and high colloidal stability. The poly(ethylene glycol)-incorporated dendron lipid vesicles tightly retained ovalbumin molecules in their internal aqueous space but released them almost completely at pH 6.0. In addition, the vesicles were shown to achieve efficient ovalbumin delivery into cytosol of DC2.4 cells (mouse dendritic cell line) after internalization through endocytosis.

Peroxisome proliferator-activated receptor γ coactivator 1α regulates downstream of tyrosine kinase-7 (Dok-7) expression important for neuromuscular junction formation.

The neuromuscular junction (NMJ)-formed between a motor nerve terminal and skeletal muscle fiber-plays an important role in muscle contraction and other muscle functions. Aging and neurodegeneration worsen NMJ formation and impair muscle function. Downstream of tyrosine kinase-7 (Dok-7), expressed in skeletal muscle fibers, is essential for the formation of NMJ. Exercise increases the expression of the transcriptional coactivator peroxisome proliferator-activated receptor γ coactivator 1α (PGC1α) in skeletal muscles and restores NMJ formation. In this study, we used skeletal muscle-specific PGC1α knockout or overexpression mice to examine the role of PGC1α in regulating Dok-7 expression and NMJ formation. Our findings revealed that Dok-7 expression is regulated by PGC1α, and luciferase activity of the Dok-7 promoter is greatly increased by coexpressing PGC1α and estrogen receptor-related receptor α. Thus, we suggest PGC1α is involved in exercise-mediated restoration of NMJ formation.

Recurrence of Large-Vessel Vasculitis Induced by Multiple Types of Granulocyte Colony-Stimulating Factor Preparation in Patient with Large-Cell Neuroendocrine Lung Carcinoma: A Case Report.

With the increased use of granulocyte colony-stimulating factor (G-CSF) preparations, there is concern about the increase in G-CSF-associated large-vessel vasculitis; however, there have been no previous reports of vasculitis caused by multiple types of G-CSF preparations. We experienced a case of drug-induced large-vessel vasculitis caused by two different G-CSF products, which was difficult to diagnose. When treating patients with a history of large-vessel vasculitis caused by pegfilgrastim, we need to pay attention to its recurrence when using other G-CSF preparations.

Regulation of Skeletal Muscle Function by Amino Acids, Especially Non-Proteinogenic Amino Acids.

Amino acids are compounds that contain an amino group (-NH2) and a carboxyl group (-COOH) and are components of proteins and materials for various bioactive molecules. The skeletal muscle, which is the largest organ in the human body, representing ~40% of the total body weight, plays important roles in exercise, energy expenditure, and glucose/amino acid usage-processes that are modulated by various amino acids and their metabolites. In this review, we address the metabolism and function of amino acids, especially non-proteinogenic amino acids, in the skeletal muscle. Leucine, a BCAA, and its metabolite, ß-hydroxy-ß-methylbutyrate (HMB), both activate mammalian target of rapamycin complex 1 (mTORC1) and increase protein synthesis, but the mechanisms of activation appear to be different. The metabolite of valine (another BCAA), ß-aminoisobutyric acid (BAIBA), is increased by exercise, is secreted by the skeletal muscle, and acts on other tissues, such as white adipose tissue, to increase energy expenditure. In addition, several amino acid-related molecules reportedly activate skeletal muscle function. Oral 5-aminolevulinic acid (ALA) supplementation can protect against mild hyperglycemia and help prevent type 2 diabetes. ß-alanine levels are decreased in the skeletal muscles of aged mice. ß-alanine supplementation increased the physical performance and improved the executive function induced by endurance exercise in middle-aged individuals. Further studies focusing on the effects of amino acids and their metabolites on skeletal muscle function will provide data essential for the production of food supplements for older adults, athletes, and individuals with metabolic diseases.

A case of adult multisystem Langerhans histiocytosis successfully treated by smoking cessation and radiotherapy for bone lesion.

An adult patient was diagnosed with multisystem Langerhans cell histiocytosis with lung and bone lesions. Her lung lesions improved after smoking cessation. Radiotherapy was performed for the bone lesions. Follow-up assessment at 2 years after diagnosis showed no recurrence. Our case shows that remission is possible even without systemic treatment.

Vitamin D Activates Various Gene Expressions, Including Lipid Metabolism, in C2C12 Cells.

Vitamin D is a fat-soluble molecule, well known for its role in regulating calcium homeostasis in bone. It has become increasingly clear that it also has important effects in many other organs, including the skeletal muscle. In order to gain insight into the role of vitamin D in the skeletal muscle, we performed microarray analysis using C2C12 myoblasts treated with 1,25-dihydroxyvitamin D (1,25(OH)2D), active form of vitamin D. We found multiple genes upregulated by 1,25(OH)2D. Some of them, i.e., vitamin D receptor (Vdr), diacylglycerol O-acyltransferase (Dgat1 and Dgat2, the rate limiting steps of triacylglycerol acylation), and vascular endothelial growth factor A (Vegfa), were previously reported to be upregulated by 1,25(OH)2D in C2C12 cells. RT-qPCR analysis confirmed increased mRNA levels of Rarres2, Dio2, Tgm2, Lpl, Mdfi, Igfbp3, Dgat1, Crabp2, Gadd45a, Vagfa, Dgat2, C3, Ldhb, Cebpa, Igfbp5, Mrc2, Vdr. Thus, many genes, including lipid metabolism genes as well as genes related to muscle functions, appear to be upregulated by 1,25(OH)2D in muscle cells.

Sichuan dark tea improves lipid metabolism and prevents aortic lipid deposition in diet-induced atherosclerosis model rats.

Background and aims: Sichuan dark tea (ST), Zangcha, is a traditional fermented Chinese tea found in Sichuan and Tibet and claimed for beneficial effects against lifestyle-related metabolic disorders. We examined the effects of ST on lipid metabolism and atherosclerosis. Methods and results: Sichuan dark tea was given to fat-rich diet-induced atherosclerosis model rats in comparison with dark-fermented Chinese Pu-erh tea (PT) and Japanese green tea (GT). After 8 weeks of feeding, ST and PT induced an increase in high-density lipoprotein (HDL)-cholesterol and a decrease in glucose, and ST decreased triglyceride in plasma. ST also induced low pH in the cecum. There was no significant change in their body weight among the fat-feeding groups but a decrease was found in the visceral fat and liver weight in the ST group. Accordingly, ST reduced lipid deposition in the aorta in comparison with PT and GT. ST increased mRNA of LXRα, PPARα, PPARγ, and ABCA1 in the rat liver. The extract of ST stimulated the AMPK pathway to increase the expression of ABCA1 in J774 cells and increased expression of lipoprotein lipase and hormone-sensitive lipase in 3T3L1 cells, consistent with its anti-atherogenic effects in rats. High-performance liquid chromatography analysis showed unique spectra of original specific compounds of caffeine and catechins in each tea extract, but none of them was likely responsible for these effects. Conclusion: Sichuan dark tea increases plasma HDL and reduces plasma triglyceride to decrease atherosclerosis through AMPK activation. Further study is required to identify specific components for the effects of this tea preparation.

Down-regulation of CD20 expression in B-cell lymphoma cells after treatment with rituximab-containing combination chemotherapies: its prevalence and clinical significance.

Although rituximab is a key molecular targeting drug for CD20-positive B-cell lymphomas, resistance to rituximab has recently been recognized as a considerable problem. Here, we report that a CD20-negative phenotypic change after chemotherapies with rituximab occurs in a certain number of CD20-positive B-cell lymphoma patients. For 5 years, 124 patients with B-cell malignancies were treated with rituximab-containing chemotherapies in Nagoya University Hospital. Relapse or progression was confirmed in 36 patients (29.0%), and a rebiopsy was performed in 19 patients. Of those 19, 5 (26.3%; diffuse large B-cell lymphoma [DLBCL], 3 cases; DLBCL transformed from follicular lymphoma, 2 cases) indicated CD20 protein-negative transformation. Despite salvage chemotherapies without rituximab, all 5 patients died within 1 year of the CD20-negative transformation. Quantitative reverse-transcription-polymerase chain reaction (RT-PCR) showed that CD20 mRNA expression was significantly lower in CD20-negative cells than in CD20-positive cells obtained from the same patient. Interestingly, when CD20-negative cells were treated with 5-aza-2'-deoxycytidine in vitro, the expression of CD20 mRNA was stimulated within 3 days, resulting in the restoration of both cell surface expression of the CD20 protein and rituximab sensitivity. These findings suggest that some epigenetic mechanisms may be partly related to the down-regulation of CD20 expression after rituximab treatment.

Early responders within seven days of dupilumab treatment for severe asthma evaluated by patient-reported outcome: a pilot study.

BACKGROUND: The management of severe asthma-associated symptoms is essential since they are distressing to the affected patients, and also greatly impair their quality of life. Dupilumab, a monoclonal antibody, blocks interleukin (IL)-4 and IL-13 signaling, both of which are crucial in acquired and innate immunity pathways through fast signal transduction, leading to an early response to treatment. Although rapid improvement within 1-3 days after dupilumab treatment was observed in moderate-to-severe atopic dermatitis, an early response within 7 days of dupilumab treatment in severe asthma has not been reported. METHODS: Twelve consecutive patients with severe asthma who were newly treated with dupilumab between July 2019 and April 2020 were retrospectively investigated. We evaluated the early response (within 7 days) of patients with severe asthma receiving dupilumab therapy. Asthma control test (ACT) and the daily ACT, which was modified from the ACT to evaluate daily symptoms associated with asthma, were adopted as patient-reported outcomes (PROs) at week 8 and within 7 days, respectively. Patients were stratified into early responders (7 days), late responders (week 8), and non-responders without significant improvement in PROs. Descriptive statistics were adopted due to the limited number of patients. RESULTS: Four of these 12 patients were early responders, with the following baseline characteristics: body mass index, <25 kg/m2; without depression; baseline forced expiratory volume in 1 second, <1.50 L; and more than one exacerbation in 1 year. On the other hand, five were late responders, and 44.4% of the nine responders were early responders. The higher the eosinophilic count and/or FeNO did not show any relationship between the early responder and nonresponder. CONCLUSIONS: The effect of dupilumab on severe asthma in patients with atopic features could be started earlier than 2 weeks, similar to atopic dermatitis. Daily ACT may be useful in monitoring the early efficacy of dupilumab in treating severe asthma.

Predictors of survival among Japanese patients receiving first-line chemoimmunotherapy for advanced non-small cell lung cancer.

BACKGROUND: First-line chemoimmunotherapy (CIT) has improved overall survival (OS) and progression-free survival (PFS) outcomes among patients with non-small cell lung cancer (NSCLC). The immunological and nutritional statuses of patients fluctuate during treatment using immune checkpoint inhibitors, and are closely related to treatment outcomes. However, it is unclear whether these markers are significant in patients who are receiving CIT. METHODS: This retrospective single-center study evaluated 34 consecutive Japanese patients with NSCLC who were treated using first-line CIT. Previously reported markers that reflect immunological and nutritional statuses were evaluated at three time points: at the start of CIT, after three weeks, and at the end of induction therapy. RESULTS: The median PFS was 7.2 months (95% confidence interval: 6.3 months-not reached) and the median OS was not reached (95% confidence interval: 9.6 months-not reached). The PFS duration was significantly associated with the baseline neutrophil-to-lymphocyte ratio and the three-week values for the modified Glasgow prognostic score, C-reactive protein-albumin ratio, prognostic nutrition index, and advanced lung cancer inflammation index. The OS duration was significantly associated with the pre-treatment values for the neutrophil-to-lymphocyte ratio and advanced lung cancer inflammation index, as well as the prognostic nutrition index at the end of induction therapy. CONCLUSIONS: Immunological and nutritional markers could be useful for predicting the outcomes of CIT for Japanese patients with advanced non-small cell lung cancer. The timing of their evaluation may also be important. KEY POINTS: SIGNIFICANT FINDINGS OF THE STUDY: Overall survival in patients receiving first-line chemoimmunotherapy for advanced lung cancer were associated with pretreatment values of neutrophil-to-lymphocyte ratio, advanced lung cancer inflammation index, and the prognostic nutrition index at the end of induction therapy. WHAT THIS STUDY ADDS: Repetitive evaluation of immunological and nutritional markers may be useful for guiding prognostication and treatment selection for Japanese patients with advanced lung cancer.

[Analysis of high-risk multiple myeloma patients treated with high-dose chemotherapy].

Although high-dose chemotherapy supported by autologous peripheral blood stem cell transplantation (auto-PBSCT) is the standard approach for younger patients with multiple myeloma, some of them still show a poor prognosis. We attempted to define a high-risk group among 32 patients who received auto-PBSCT between August 2000 and July 2007 in our hospital. In conventional metaphase cytogenetics (G-banding), chromosome abnormalities (CA), hypodiploidy, and 13 or 13q deletion (Gd13) were noted in 27.6, 17.2, and 19.4% of patients, respectively. In a FISH study, del(17p) (Fd17p) and t(4;14) were noted in 12.5 and 9.4% of patients, respectively. Prognostic analyses of patients with these abnormal chromosomes revealed that those with CA, hypodiploidy, Gd13, and t(4;14) showed a poorer survival at 3 years compared to those without them: 42.9 vs. 95.2% (p=0.0072), 25.0 vs. 91.5% (p=0.0056), and 40.0 vs. 91.8% (p=0.0245), 0 vs. 89.3% (p<.0001), respectively. When we defined patients showing at least one of CA, hypodiploidy, Gd13, Fd17p, and t(4;14) as a "high-risk group", they showed a poorer overall (23.9 vs. 106.1 mo., p=0.0011) and progression-free (13.5 vs. 25.6 mo., p=0.0095) survival compared to a non-high-risk group. This study indicated that chromosome analysis has a prognostic value in patients with multiple myeloma receiving auto-PBSCT.

Atezolizumab in combination with carboplatin and etoposide for heavily treated small cell lung cancer.

Atezolizumab was the first immune checkpoint inhibitor (ICI) to be introduced as a first-line treatment option for extensive-stage small cell lung cancer (ES-SCLC), in combination with carboplatin and etoposide (CE) chemotherapy. However, SCLC treatment options after progression to first-line chemotherapy are limited, warranting the readministration of previously used drugs. In combination with atezolizumab, CE readministration may theoretically be effective, based on two tentative mechanisms: its additive and synergistic effects on cytotoxic chemotherapy. The additive effect is based on the IFCT-1603 trial in which the Kaplan-Meier estimates of both progression-free survival (PFS) and overall survival (OS) in the atezolizumab group exhibited a tail plateau in the selected population. Conversely, an anti-PD-L1 antibody synergistic effect on platinum compounds was assessed in a preclinical study, which was reinforced by clinical data. Thus, atezolizumab in combination with CE may be a treatment option in heavily treated patients. Here, we describe the first case of a heavily treated ES-SCLC patient treated with chemoimmunotherapy, resulting in a partial response and a durable PFS. KEY POINTS: SIGNIFICANT FINDINGS OF THE STUDY AND WHAT THIS STUDY ADDS: CE readministration with atezolizumab may be effective based on two tentative mechanisms. Additive and synergistic effects of atezolizumab on CE have been previously suggested via a clinical trial and preclinical study, respectively. This is reflected in the current case in clinical settings.

Escape mechanisms from antibody therapy to lymphoma cells: downregulation of CD20 mRNA by recruitment of the HDAC complex and not by DNA methylation.

Although rituximab is a critical monoclonal antibody therapy for CD20-positive B-cell lymphomas, rituximab resistance showing a CD20-negative phenotypic change has been a considerable clinical problem. Here we demonstrate that CD20 mRNA and protein expression is repressed by recruitment of a histone deacetylase protein complex to the MS4A1 (CD20) gene promoter in CD20-negative transformed cells after treatment with rituximab. CD20 mRNA and protein expression were stimulated by decitabine (5-Aza-dC) in CD20-negative transformed cells, and was enhanced by trichostation A (TSA). Immunoblotting indicated that DNMT1 expression was first downregulated 1 day after treatment with 5-Aza-dC, but IRF4 and Pu.1, the transcriptional regulators of MS4A1, were still expressed with or without 5-Aza-dC. Interestingly, CpG methylation of the MS4A1 promoter was not observed in CD20-negative transformed cells without 5-Aza-dC. A chromatin immunoprecipitation (ChIP) assay indicated that the Sin3A-HDAC1 co-repressor complex was recruited to the promoter and dissociated from the promoter with 5-Aza-dC and TSA, resulting in histone acetylation. Under these conditions, IRF4 and Pu.1 were continually recruited to the promoter with or without 5-Aza-dC and TSA. These results suggest that recruitment of the Sin3A-HDAC1 complex is related to downregulation of CD20 expression in CD20-negative B-cells after treatment with rituximab.