Id2 and Id3 maintain the regulatory T cell pool to suppress inflammatory disease.

Regulatory T (Treg) cells suppress the development of inflammatory disease, but our knowledge of transcriptional regulators that control this function remains incomplete. Here we show that expression of Id2 and Id3 in Treg cells was required to suppress development of fatal inflammatory disease. We found that T cell antigen receptor (TCR)-driven signaling initially decreased the abundance of Id3, which led to the activation of a follicular regulatory T (TFR) cell-specific transcription signature. However, sustained lower abundance of Id2 and Id3 interfered with proper development of TFR cells. Depletion of Id2 and Id3 expression in Treg cells resulted in compromised maintenance and localization of the Treg cell population. Thus, Id2 and Id3 enforce TFR cell checkpoints and control the maintenance and homing of Treg cells.

Regulation of lymphoid-myeloid lineage bias through regnase-1/3-mediated control of Nfkbiz.

ABSTRACT: Regulation of lineage biases in hematopoietic stem and progenitor cells (HSPCs) is pivotal for balanced hematopoietic output. However, little is known about the mechanism behind lineage choice in HSPCs. Here, we show that messenger RNA (mRNA) decay factors regnase-1 (Reg1; Zc3h12a) and regnase-3 (Reg3; Zc3h12c) are essential for determining lymphoid fate and restricting myeloid differentiation in HSPCs. Loss of Reg1 and Reg3 resulted in severe impairment of lymphopoiesis and a mild increase in myelopoiesis in the bone marrow. Single-cell RNA sequencing analysis revealed that Reg1 and Reg3 regulate lineage directions in HSPCs via the control of a set of myeloid-related genes. Reg1- and Reg3-mediated control of mRNA encoding Nfkbiz, a transcriptional and epigenetic regulator, was essential for balancing lymphoid/myeloid lineage output in HSPCs in vivo. Furthermore, single-cell assay for transposase-accessible chromatin sequencing analysis revealed that Reg1 and Reg3 control the epigenetic landscape on myeloid-related gene loci in early stage HSPCs via Nfkbiz. Consistently, an antisense oligonucleotide designed to inhibit Reg1- and Reg3-mediated Nfkbiz mRNA degradation primed hematopoietic stem cells toward myeloid lineages by enhancing Nfkbiz expression. Collectively, the collaboration between posttranscriptional control and chromatin remodeling by the Reg1/Reg3-Nfkbiz axis governs HSPC lineage biases, ultimately dictating the fate of lymphoid vs myeloid differentiation.

The E-Id Protein Axis Specifies Adaptive Lymphoid Cell Identity and Suppresses Thymic Innate Lymphoid Cell Development.

Innate and adaptive lymphoid development is orchestrated by the activities of E proteins and their antagonist Id proteins, but how these factors regulate early T cell progenitor (ETP) and innate lymphoid cell (ILC) development remains unclear. Using multiple genetic strategies, we demonstrated that E proteins E2A and HEB acted in synergy in the thymus to establish T cell identity and to suppress the aberrant development of ILCs, including ILC2s and lymphoid-tissue-inducer-like cells. E2A and HEB orchestrated T cell fate and suppressed the ILC transcription signature by activating the expression of genes associated with Notch receptors, T cell receptor (TCR) assembly, and TCR-mediated signaling. E2A and HEB acted in ETPs to establish and maintain a T-cell-lineage-specific enhancer repertoire, including regulatory elements associated with the Notch1, Rag1, and Rag2 loci. On the basis of these and previous observations, we propose that the E-Id protein axis specifies innate and adaptive lymphoid cell fate.

Global changes in the nuclear positioning of genes and intra- and interdomain genomic interactions that orchestrate B cell fate.

The genome is folded into domains located in compartments that are either transcriptionally inert or transcriptionally permissive. Here we used genome-wide strategies to characterize domains during B cell development. Structured interaction matrix analysis showed that occupancy by the architectural protein CTCF was associated mainly with intradomain interactions, whereas sites bound by the histone acetyltransferase p300 or the transcription factors E2A or PU.1 were associated with intra- and interdomain interactions that are developmentally regulated. We identified a spectrum of genes that switched nuclear location during early B cell development. In progenitor cells, the transcriptionally inactive locus encoding early B cell factor (Ebf1) was sequestered at the nuclear lamina, which thereby preserved their multipotency. After development into the pro-B cell stage, Ebf1 and other genes switched compartments to establish new intra- and interdomain interactions associated with a B lineage-specific transcription signature.

The Function of E2A in B-Cell Development.

Helix-loop-helix (HLH) transcription factors (TFs) play a key role in various cellular differentiation and function through the regulation of enhancer activity. E2A, a member of the mammalian E-protein family (class I HLH protein), is well known to play an important role in hematopoiesis, especially in adaptive lymphocyte development. E2A instructs B- and T-cell lineage development through the regulation of enhancer activity for B- or T-cell signature gene expression, including Rag1 and Rag2 (Rag1/2) genes. In this chapter, we mainly focus on the function of E2A in B-cell development and on the roles of E2A in establishing the enhancer landscape through the recruitment of EP300/KAT3B, chromatin remodeling complex, mediator, cohesion, and TET proteins. Finally, we demonstrate how E2A orchestrates the assembly of the Rag1/2 gene super-enhancer (SE) formation by changing the chromatin conformation across the Rag gene locus.

The opposing roles of the transcription factor E2A and its antagonist Id3 that orchestrate and enforce the naive fate of T cells.

It is established that the transcription factor E2A and its antagonist Id3 modulate the checkpoints consisting of the precursor to the T cell antigen receptor (pre-TCR) and the TCR. Here we demonstrate that Id3 expression was higher beyond the pre-TCR checkpoint, remained high in naive T cells and showed a bimodal pattern in the effector-memory population. We show how E2A promoted T lineage specification and how pre-TCR-mediated signaling affected E2A genome-wide occupancy. Thymi in Id3-deficient mice had aberrant development of effector-memory cells, higher expression of the chemokine receptor CXCR5 and the transcriptional repressor Bcl-6 and, unexpectedly, T cell-B cell conjugates and B cell follicles. Collectively, our data show how E2A acted globally to orchestrate development into the T lineage and that Id3 antagonized E2A activity beyond the pre-TCR checkpoint to enforce the naive fate of T cells.

The E-Id protein axis modulates the activities of the PI3K-AKT-mTORC1-Hif1a and c-myc/p19Arf pathways to suppress innate variant TFH cell development, thymocyte expansion, and lymphomagenesis.

It is now well established that the E and Id protein axis regulates multiple steps in lymphocyte development. However, it remains unknown how E and Id proteins mechanistically enforce and maintain the naïve T-cell fate. Here we show that Id2 and Id3 suppressed the development and expansion of innate variant follicular helper T (TFH) cells. Innate variant TFH cells required major histocompatibility complex (MHC) class I-like signaling and were associated with germinal center B cells. We found that Id2 and Id3 induced Foxo1 and Foxp1 expression to antagonize the activation of a TFH transcription signature. We show that Id2 and Id3 acted upstream of the Hif1a/Foxo/AKT/mTORC1 pathway as well as the c-myc/p19Arf module to control cellular expansion. We found that mice depleted for Id2 and Id3 expression developed colitis and αß T-cell lymphomas. Lymphomas depleted for Id2 and Id3 expression displayed elevated levels of c-myc, whereas p19Arf abundance declined. Transcription signatures of Id2- and Id3-depleted lymphomas revealed similarities to genetic deficiencies associated with Burkitt lymphoma. We propose that, in response to antigen receptor and/or cytokine signaling, the E-Id protein axis modulates the activities of the PI3K-AKT-mTORC1-Hif1a and c-myc/p19Arf pathways to control cellular expansion and homeostatic proliferation.

ß-Selection-induced proliferation is required for αß T cell differentiation.

Proliferation and differentiation are tightly coordinated to produce an appropriate number of differentiated cells and often exhibit an antagonistic relationship. Developing T cells, which arise in the thymus from a minute number of bone-marrow-derived progenitors, undergo a major expansion upon pre-T cell receptor (TCR) expression. The burst of proliferation coincides with differentiation toward the αß T cell lineage-but the two processes were previously thought to be independent from one another, although both were driven by signaling from pre-TCR and Notch receptors. Here we report that proliferation at this step was not only absolutely required for differentiation but also that its ectopic activation was sufficient to substantially rescue differentiation in the absence of Notch signaling. Consistently, pharmacological inhibition of the cell cycle machinery also blocked differentiation in vivo. Thus the proliferation step is strictly required prior to differentiation of immature thymocytes.

4-Pyridone-3-carboxylic acid as a benzoic acid bioisostere: Design, synthesis, and evaluation of EP300/CBP histone acetyltransferase inhibitors.

Histone acetyltransferases (HATs) play a crucial role in post-translational modification. Among them, overexpression, mutation, or hyperfunction of EP300/CBP has been associated with various cancers. In this study, we identified the novel compound 2-chloro-5-[5-[(E)-[1-(3-chlorophenyl)-3-methyl-5-oxo-pyrazol-4-ylidene]methyl]-2-furyl]benzoic acid (1) as an EP300 HAT inhibitor via virtual screening. Further research has been focused on the design, synthesis, and in vitro biological evaluation of virtual hit derivatives. The studies revealed that 4-pyridone-3-carboxylic acid derivatives exhibited bioisosterism of benzoic acid. Replacement proved effective, providing compounds with similar EP300 HAT-inhibitory activity and improved cell growth-inhibitory activity compared to the benzoic acid analogs. Through these studies, we identified a potent and selective EP300/CBP HAT inhibitor.

The Evolution of Rag Gene Enhancers and Transcription Factor E and Id Proteins in the Adaptive Immune System.

Adaptive immunity relies on the V(D)J DNA recombination of immunoglobulin (Ig) and T cell receptor (TCR) genes, which enables the recognition of highly diverse antigens and the elicitation of antigen-specific immune responses. This process is mediated by recombination-activating gene (Rag) 1 and Rag2 (Rag1/2), whose expression is strictly controlled in a cell type-specific manner; the expression of Rag1/2 genes represents a hallmark of lymphoid lineage commitment. Although Rag genes are known to be evolutionally conserved among jawed vertebrates, how Rag genes are regulated by lineage-specific transcription factors (TFs) and how their regulatory system evolved among vertebrates have not been fully elucidated. Here, we reviewed the current body of knowledge concerning the cis-regulatory elements (CREs) of Rag genes and the evolution of the basic helix-loop-helix TF E protein regulating Rag gene CREs, as well as the evolution of the antagonist of this protein, the Id protein. This may help to understand how the adaptive immune system develops along with the evolution of responsible TFs and enhancers.

Long non-coding RNA MANCR is a target of BET bromodomain protein BRD4 and plays a critical role in cellular migration and invasion abilities of prostate cancer.

Androgen receptor (AR)-negative castration-resistant prostate cancer (CRPC) is highly aggressive and is resistant to most of the current therapies. Bromodomain and extra terminal domain (BET) protein BRD4 binds to super-enhancers (SEs) that drive high expression of oncogenes in many cancers. A BET inhibitor, JQ1, has been found to suppress the malignant phenotypes of prostate cancer cells, however, the target genes of JQ1 remain largely unknown. Here we show that SE-associated genes specific for AR-negative CRPC PC3 cells include genes involved in migration and invasion, and that JQ1 impairs migration and invasion of PC3 cells. We identified a long non-coding RNA, MANCR, which was markedly down-regulated by JQ1, and found that BRD4 binds to the MANCR locus. MANCR knockdown led to a significant decrease in migration and invasion of PC3 cells. Furthermore, RNA sequencing analysis revealed that expression of the genes involved in migration and invasion was altered by MANCR knockdown. In summary, our data demonstrate that MANCR plays a critical role in migration and invasion of PC3 cells.

Erlotinib plus bevacizumab versus erlotinib alone in patients with EGFR-positive advanced non-squamous non-small-cell lung cancer (NEJ026): interim analysis of an open-label, randomised, multicentre, phase 3 trial.

BACKGROUND: Resistance to first-generation or second-generation EGFR tyrosine kinase inhibitor (TKI) monotherapy develops in almost half of patients with EGFR-positive non-small-cell lung cancer (NSCLC) after 1 year of treatment. The JO25567 phase 2 trial comparing erlotinib plus bevacizumab combination therapy with erlotinib monotherapy established the activity and manageable toxicity of erlotinib plus bevacizumab in patients with NSCLC. We did a phase 3 trial to validate the results of the JO25567 study and report here the results from the preplanned interim analysis. METHODS: In this prespecified interim analysis of the randomised, open-label, phase 3 NEJ026 trial, we recruited patients with stage IIIB-IV disease or recurrent, cytologically or histologically confirmed non-squamous NSCLC with activating EGFR genomic aberrations from 69 centres across Japan. Eligible patients were at least 20 years old, and had an Eastern Cooperative Oncology Group performance status of 2 or lower, no previous chemotherapy for advanced disease, and one or more measurable lesions based on Response Evaluation Criteria in Solid Tumours (1.1). Patients were randomly assigned (1:1) to receive oral erlotinib 150 mg per day plus intravenous bevacizumab 15 mg/kg once every 21 days, or erlotinib 150 mg per day monotherapy. Randomisation was done by minimisation, stratified by sex, smoking status, clinical stage, and EGFR mutation subtype. The primary endpoint was progression-free survival. This study is ongoing; the data cutoff for this prespecified interim analysis was Sept 21, 2017. Efficacy was analysed in the modified intention-to-treat population, which included all randomly assigned patients who received at least one dose of treatment and had at least one response evaluation. Safety was analysed in all patients who received at least one dose of study drug. The trial is registered with the University Hospital Medical Information Network Clinical Trials Registry, number UMIN000017069. FINDINGS: Between June 3, 2015, and Aug 31, 2016, 228 patients were randomly assigned to receive erlotinib plus bevacizumab (n=114) or erlotinib alone (n=114). 112 patients in each group were evaluable for efficacy, and safety was evaluated in 112 patients in the combination therapy group and 114 in the monotherapy group. Median follow-up was 12·4 months (IQR 7·0-15·7). At the time of interim analysis, median progression-free survival for patients in the erlotinib plus bevacizumab group was 16·9 months (95% CI 14·2-21·0) compared with 13·3 months (11·1-15·3) for patients in the erlotinib group (hazard ratio 0·605, 95% CI 0·417-0·877; p=0·016). 98 (88%) of 112 patients in the erlotinib plus bevacizumab group and 53 (46%) of 114 patients in the erlotinib alone group had grade 3 or worse adverse events. The most common grade 3-4 adverse event was rash (23 [21%] of 112 patients in the erlotinib plus bevacizumab group vs 24 [21%] of 114 patients in the erlotinib alone group). Nine (8%) of 112 patients in the erlotinib plus bevacizumab group and five (4%) of 114 patients in the erlotinib alone group had serious adverse events. The most common serious adverse events were grade 4 neutropenia (two [2%] of 112 patients in the erlotinib plus bevacizumab group) and grade 4 hepatic dysfunction (one [1%] of 112 patients in the erlotinib plus bevacizumab group and one [1%] of 114 patients in the erlotinib alone group). No treatment-related deaths occurred. INTERPRETATION: The results of this interim analysis showed that bevacizumab plus erlotinib combination therapy improves progression-free survival compared with erlotinib alone in patients with EGFR-positive NSCLC. Future studies with longer follow-up, and overall survival and quality-of-life data will be required to further assess the efficacy of this combination in this setting. FUNDING: Chugai Pharmaceutical.

Clinical Efficacy of Telemedicine Compared to Face-to-Face Clinic Visits for Smoking Cessation: Multicenter Open-Label Randomized Controlled Noninferiority Trial.

BACKGROUND: Tobacco is a major public health concern. A 12-week standard smoking cessation program is available in Japan; however, it requires face-to-face clinic visits, which has been one of the key obstacles to completing the program, leading to a low smoking cessation success rate. Telemedicine using internet-based video counseling instead of regular clinic visits could address this obstacle. OBJECTIVE: This study aimed to evaluate the efficacy and feasibility of an internet-based remote smoking cessation support program compared with the standard face-to-face clinical visit program among patients with nicotine dependence. METHODS: This study was a randomized, controlled, open-label, multicenter, noninferiority trial. We recruited nicotine-dependent adults from March to June 2018. Participants randomized to the telemedicine arm received internet-based video counseling, whereas control participants received standard face-to-face clinic visits at each time point in the smoking cessation program. Both arms received a CureApp Smoking Cessation smartphone app with a mobile exhaled carbon monoxide checker. The primary outcome was a continuous abstinence rate (CAR) from weeks 9 to 12. Full analysis set was used for data analysis. RESULTS: We randomized 115 participants with nicotine dependence: 58 were allocated to the telemedicine (internet-based video counseling) arm and 57, to the control (standard face-to-face clinical visit) arm. We analyzed all 115 participants for the primary outcome. Both telemedicine and control groups had similar CARs from weeks 9 to 12 (81.0% vs 78.9%; absolute difference, 2.1%; 95% CI -12.8 to 17.0), and the lower limit of the difference between groups (-12.8%) was greater than the prespecified limit (-15%). CONCLUSIONS: The application of telemedicine using internet-based video counseling as a smoking cessation program had a similar CAR from weeks 9 to 12 as that of the standard face-to-face clinical visit program. The efficacy of the telemedicine-based smoking cessation program was not inferior to that of the standard visit-based smoking cessation program. TRIAL REGISTRATION: University Hospital Medical Information Network Clinical Trials Registry: UMIN000031620; https://upload.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000035975.

Regional differences in the prevalence of sensitization to environmental allergens: Analysis on IgE antibody testing conducted at major clinical testing laboratories throughout Japan from 2002 to 2011.

BACKGROUND: Identification of sensitized allergens for patients with respiratory allergy is an important step in disease care and environmental allergen control. The Japanese archipelago belongs to various climate categories due to its length from north to south which transverse the subarctic in the north to the subtropical in the south, suggesting substantial regional differences in dominant environmental allergens. However, few studies have assessed the regional differences in the prevalence of sensitization to environmental allergens. METHODS: We requested three major clinical testing laboratories to provide us with summarized results of antigen-specific IgE-antibody (Ab) measurements. These measurements were collected for clinical purposes throughout Japan from 2002 through 2011. The prevalence of positivity for IgE-Ab against 19 environmental allergens was calculated for each prefecture in order to evaluate regional differences. RESULTS: Test data on specific IgE-Ab of 19,969,753 orders were analyzed. The prevalence of positivity for house dust mites was high and the regional difference was low, whereas apparent regional differences were found for pollen, insects, and fungi. The prevalence of positivity for Japanese cedar was low in Hokkaido and Okinawa, while those to alder was highest in Hokkaido. Higher prevalence for insects was observed in southern areas (Okinawa and prefectures in Kyusyu). CONCLUSIONS: Findings of this study clearly demonstrated regional differences in the prevalence of sensitization to environmental allergens in Japan and the study also provides useful information for the clinician when deciding which allergens should preferentially be measured for IgE-Ab after considering regional difference.

[Analysis of Post-Recurrence Survival of Resected Lung Cancer with Brain Metastasis].

METHODS: We retrospectively evaluated the post-recurrence survival of 37 cases with brain metastases out of 439 consecutive resected cases of primary lung cancer between 2001 and 2017. FINDINGS: There was no difference in survival according to tumor size but survival was significantly shorter in patients with larger numbers of tumors. Patients initially treated with stereotactic radiosurgery(SRS)or surgical resection survived longer than those with whole-brain irradiation(WBI)(median survival: 23 months for SRS, 17 months for surgical resection, and 4 months for WBI: p<0.001 between SRS and WBI). CONCLUSIONS: As SRS is recommended for 1-4 tumors with maximum diameters ofC3 cm and surgical resection is recommended for tumors larger than 3 cm, these effective locoregional therapies should be aggressively adopted for local control of brain metastases with the aim of improved QOL and prolonged survival. Due to the deterioration of neurocognitive function, WBI should be avoided as initial treatment for brain metastases when effective locoregional therapy or systemic chemotherapy is available and reserved for leptomeningeal dissemination or miliary metastases.

[Four Cases of Resected cN2 Stage III A Non-Small-Cell Lung Cancer after Induction Chemotherapy].

Four patients with non-small-cell lung cancer(NSCLC), diagnosed with cN2 stage III A disease, by using CT and FDG-PET/ CT imaging, received 2 or 3 courses of platinum-based combination chemotherapy.The patients achieved partial response after chemotherapy and underwent surgery.Complete tumor resection was performed via upper lobectomy for 3 patients, but in 1 patient, interlobar metastatic lymph nodes remained after middle and lower bilobectomy.Two courses of postoperative chemotherapy were administered to 3 patients, but 1 patient could not receive postoperative chemotherapy due to complications.One patient, in whom lymph node metastasis completely disappeared after induction chemotherapy, is still alive and without disease recurrence for 7 years.Another patient, with the presence of only one intralobar metastatic lymph node after chemotherapy, died of brain and meningeal metastases, 3 years after surgery.Two other patients, with multiple pN2 lymph nodes after chemotherapy, died of early intrathoracic local relapse, indicating that prognosis is influenced by response to chemotherapy, especially in patients with poor N-downstaging.Improvements in response to induction therapy by using intensive chemotherapeutic regimens, concurrent radiotherapy, and strict patient selection, limited to N-downstaged cases, are needed for successful surgery outcomes in patients with cN2 stage III A NSCLC who have received induction therapy.

The establishment of B versus T cell identity.

In B cell progenitors, E-proteins E2A and HEB (HeLa E-box binding protein) are crucial for the induction of a B lineage-specific program of gene expression and for orchestrating the assembly of the immunoglobulin loci. In the thymus E2A and HEB act differently, activating the expression of genes closely associated with the establishment of T cell identity and promoting the rearrangement of T cell receptor (TCR) loci. These findings have raised the question as to how E-proteins exert these different activities. We review here the distinct regulatory networks that establish B versus T cell identity, and how genomic architecture and location of genes is modulated in these lineage decisions. We conclude by proposing a model wherein stochasticity in the nuclear location of the early B cell factor 1 (Ebf1) locus in multipotent progenitors determines this lineage choice.

[Long-Term Local Control with Radiofrequency Ablation or Radiotherapy for Second, Third, and Fourth Lung Tumors after Lobectomy for Primary Lung Cancer].

A 78-year-old woman developed second, third, and fourth lung tumors at intervals of 1-3 years after left upper lobectomy for primary lung cancer. The tumors were controlled with radiofrequency ablation(RFA)or conventionalconformalradiotherapy for 9 years postoperatively. For the treatment of second primary lung cancer or lung metastasis after surgical resection of the primary lung cancer, reoperation is not recommended because of the impaired respiratory reserve. Thus, local therapy such as radiotherapy or RFA is applied in some cases. Among these, stereotactic body radiotherapy(SBRT)is a feasible option because of its good local control and safety, which is comparable with surgery. On the other hand, for cases of multiple lesions that are not suitable for radiotherapy or combination therapy, RFA could be an option because of its short-term local control, easiness, safety, and repeatability. After surgery for primary lung cancer, a second lung tumor could be controlled with highly effective and minimally invasive local therapy if it is recognized as a local disease but is medically inoperable. Therefore, longterm postoperative follow-up for primary lung cancer is beneficial.

Evaluation of cigarette smoke-induced emphysema in mice using quantitative micro-computed tomography.

Chronic cigarette smoke (CS) exposure provokes variable changes in the lungs, and emphysema is an important feature of chronic obstructive pulmonary disease. The usefulness of micro-computed tomography (CT) to assess emphysema in different mouse models has been investigated, but few studies evaluated the dynamic structural changes in a CS-induced emphysema mouse model. A novel micro-CT technique with respiratory and cardiac gating has resulted in high-quality images that enable processing for further quantitative and qualitative analyses. Adult female C57BL/6J mice were repeatedly exposed to mainstream CS, and micro-CT scans were performed at 0, 4, 12, and 20 wk. Emphysema was also histologically quantified at each time point. Air-exposed mice and mice treated with intratracheal elastase served as controls and comparisons, respectively. End-expiratory lung volume, corresponding to functional residual volume, was defined as the calculated volume at the phase of end-expiration, and it evaluated air trapping. The end-expiratory lung volumes of CS-exposed mice were significantly larger than those of air controls at 12 and 20 wk, which was in line with alveolar enlargement and destruction by histological quantification. However, CS exposure neither increased low attenuation volume nor decreased the average lung CT value at any time point, unlike the elastase-instilled emphysema model. CS-exposed mice had rather higher average lung CT values at 4 and 12 wk. This is the first study characterizing a CS-induced emphysema model on micro-CT over time in mice. Moreover, these findings extend our understanding of the distinct pathophysiology of CS-induced emphysema in mice.

Phase I study of weekly nab-paclitaxel combined with S-1 in patients with human epidermal growth factor receptor type 2-negative metastatic breast cancer.

We conducted a phase I study of a weekly nab-paclitaxel and S-1 combination therapy in patients with human epidermal growth factor receptor type 2-negative metastatic breast cancer. The primary objective was to estimate the maximum tolerated and recommended doses. Each treatment was repeated every 21 days. Levels 1, 2a, 2b, and 3 were set depending on the S-1 dose (65 or 80 mg/m(2) ) and nab-paclitaxel infusion schedule (days 1 and 8 or days 1, 8, and 15). Fifteen patients were enrolled. Dose-limiting toxicity was observed in one patient at Level 3 (100 mg/m(2) nab-paclitaxel on days 1, 8, and 15 with 80 mg/m(2) S-1 daily for 14 days, followed by 7 days of rest). Although the maximum tolerated dose was not reached, the recommended dose was determined to be Level 3. Neutropenia was the most frequent grade 3-4 treatment-related adverse event. For patients with measurable lesions, the response rate was 50.0% and the median time to treatment failure and median progression-free survival was 13.2 and 21.0 months, respectively. The present results show the feasibility and potential for long-term administration of this combination therapy.