Long-term outcomes of neoadjuvant trastuzumab emtansine + pertuzumab (T-DM1 + P) and docetaxel + carboplatin + trastuzumab + pertuzumab (TCbHP) for HER2-positive primary breast cancer: results of the randomized phase 2 JBCRG20 study (Neo-peaks).

PURPOSE: The randomized phase 2 Neo-peaks study examined usefulness of neoadjuvant trastuzumab emtansine + pertuzumab (T-DM1 + P) following docetaxel + carboplatin + trastuzumab + pertuzumab (TCbHP) as compared with the standard TCbHP regimen. We previously reported that pCR rate after neoadjuvant therapy tended to be higher with TCbHP followed by T-DM1 + P. We conducted an exploratory analysis of prognosis 5 years after surgery. METHODS: Neoadjuvant treatment with TCbHP (6 cycles; group A), TCbHP (4 cycles) followed by T-DM1 + P (4 cycles; group B), and T-DM1 + P (4 cycles; group C, + 2 cycles in responders) were compared. Group C non-responders after 4 cycles were switched to an anthracycline-based regimen. We evaluated 5-year disease-free survival (DFS), distant DFS (DDFS), and overall survival (OS). RESULTS: Data from 203 patients (50, 52, and 101 in groups A-C, respectively) were analyzed. No significant intergroup differences were found for DFS, DDFS, or OS. The 5-year DFS rates (95% CI) were 91.8% (79.6-96.8%), 92.3% (80.8-97.0%), and 88.0% (79.9-93.0%) in groups A-C, respectively. TCbHP followed by T-DM1 + P and T-DM1 + P with response-guided addition of anthracycline therapy resulted in similar long-term prognosis to that of TCbHP. CONCLUSIONS: In patients who achieved pCR after neoadjuvant therapy with T-DM1 + P, omission of adjuvant anthracycline may be considered, whereas treatment should be adjusted for non-pCR patients with residual disease. T-DM1 + P with response-guided treatment adjustment may be useful for minimizing toxicity. TRIAL REGISTRATION NUMBER AND DATE OF REGISTRATION: UMIN-CTR, UMIN000014649, prospectively registered July 25, 2014. Some of the study results were presented as a Mini Oral session at the ESMO Breast Cancer 2023 (Berlin, Germany, 11-13 May 2023).

A Novel Hemocyte-Derived Peptide and Its Possible Roles in Immune Response of Ciona intestinalis Type A.

A wide variety of bioactive peptides have been identified in the central nervous system and several peripheral tissues in the ascidian Ciona intestinalis type A (Ciona robusta). However, hemocyte endocrine peptides have yet to be explored. Here, we report a novel 14-amino-acid peptide, CiEMa, that is predominant in the granular hemocytes and unilocular refractile granulocytes of Ciona. RNA-seq and qRT-PCR revealed the high CiEma expression in the adult pharynx and stomach. Immunohistochemistry further revealed the highly concentrated CiEMa in the hemolymph of the pharynx and epithelial cells of the stomach, suggesting biological roles in the immune response. Notably, bacterial lipopolysaccharide stimulation of isolated hemocytes for 1-4 h resulted in 1.9- to 2.4-fold increased CiEMa secretion. Furthermore, CiEMa-stimulated pharynx exhibited mRNA upregulation of the growth factor (Fgf3/7/10/22), vanadium binding proteins (CiVanabin1 and CiVanabin3), and forkhead and homeobox transcription factors (Foxl2, Hox3, and Dbx) but not antimicrobial peptides (CrPap-a and CrMam-a) or immune-related genes (Tgfbtun3, Tnfa, and Il17-2). Collectively, these results suggest that CiEMa plays roles in signal transduction involving tissue development or repair in the immune response, rather than in the direct regulation of immune response genes. The present study identified a novel Ciona hemocyte peptide, CiEMa, which paves the way for research on the biological roles of hemocyte peptides in chordates.

Comparison of cisplatin-based versus standard preoperative chemotherapy in patients with operable triple-negative breast cancer: propensity score matching and inverse probability of treatment weighting analysis.

PURPOSE: The efficacy of carboplatin is non-equivalent to that of cisplatin (CDDP) for various tumor types in curative settings. However, the role of CDDP in operable triple-negative breast cancer (TNBC) patients remains unknown. We conducted a multicenter observational study to examine the effects of CDDP added to preoperative chemotherapy in patients with TNBC. METHODS: This retrospective study consecutively included previously untreated patients with stage I-III TNBC treated with preoperative chemotherapy with or without CDDP. The primary endpoint was distant disease-free survival (DDFS). Propensity score matching (PSM) and inverse probability of treatment weighting (IPTW) were used to minimize confounding biases in comparisons between the two groups. RESULTS: A total of 138 patients were enrolled in the study. Of these, 52 were in the CDDP group and 86 in the non-CDDP group. DDFS was significantly better in the CDDP group than in the non-CDDP group (unadjusted hazard ratio (HR) 0.127 and p < 0.001, PSM HR 0.141 and p < 0.003, IPTW HR 0.123 and p = < 0.001). Furthermore, among the patients with residual cancer burden (RCB) class II/III, DDFS was better in the CDDP group than in the non-CDDP group (unadjusted HR 0.192 and p = 0.013, PSM HR 0.237 and p = 0.051, IPTW HR 0.124 and p = 0.059). CONCLUSION: Our study showed that CDDP-containing regimens achieved favorable prognoses in patients with operable TNBC, especially for the RCB class II/III population. Confirmative studies are warranted to elucidate the role of CDDP in TNBC treatment.

Circularity of islets is a distinct marker for the pathological diagnosis of adult non-neoplastic hyperinsulinemic hypoglycemia using surgical specimens.

BACKGROUND: Adult non-neoplastic hyperinsulinemic hypoglycemia (ANHH), also known as adult-onset nesidioblastosis, is a rare cause of endogenous hyperinsulinemic hypoglycemia in adults. This disease is characterized by diffuse hyperplasia of pancreatic endocrine cells and is diagnosed by a pathological examination. While diagnostic criteria for this disease have already been proposed, we established more quantitative criteria for evaluating islet morphology. METHODS: We measured the number, maximum diameter, total area, and circularity (representing how closely islets resemble perfect spheres) of islets contained in representative sections of ANHH (n = 4) and control cases (n = 5) using the NIS-Elements software program. We also measured the average cell size, percentage of cells with enlarged nuclei, and percentage of cells with recognizable nucleoli for each of three representative islets. We also assessed the interobserver diagnostic concordance of ANHH between five experienced and seven less-experienced pathologists. RESULTS: There was no significant difference in the number, maximum diameter, or total area of islets between the two groups, even after correcting for these parameters per unit area. However, the number of islets with low circularity (< 0.71) per total area of the pancreatic parenchyma was significantly larger in ANHH specimens than in controls. We also found that the percentage of cells with recognizable nucleoli was significantly higher in the ANHH group than in the controls. There were no significant differences in the average cell size or the number of cells with enlarged nuclei between the groups. The correct diagnosis rate with the blind test was 47.5% ± 6.12% for experienced pathologists and 50.0% ± 8.63% for less-experienced pathologists, with no significant differences noted. CONCLUSIONS: Low circularity, which indicates an irregular islet shape, referred to as "irregular shape and occasional enlargement of islets" and "lobulated islet structure" in a previous report, is a useful marker for diagnosing ANHH. An increased percentage of recognizable nucleoli, corresponding to "macronucleoli in ß-cells," has potential diagnostic value.

Evolutionary histories of breast cancer and related clones.

Recent studies have documented frequent evolution of clones carrying common cancer mutations in apparently normal tissues, which are implicated in cancer development1-3. However, our knowledge is still missing with regard to what additional driver events take place in what order, before one or more of these clones in normal tissues ultimately evolve to cancer. Here, using phylogenetic analyses of multiple microdissected samples from both cancer and non-cancer lesions, we show unique evolutionary histories of breast cancers harbouring der(1;16), a common driver alteration found in roughly 20% of breast cancers. The approximate timing of early evolutionary events was estimated from the mutation rate measured in normal epithelial cells. In der(1;16)(+) cancers, the derivative chromosome was acquired from early puberty to late adolescence, followed by the emergence of a common ancestor by the patient's early 30s, from which both cancer and non-cancer clones evolved. Replacing the pre-existing mammary epithelium in the following years, these clones occupied a large area within the premenopausal breast tissues by the time of cancer diagnosis. Evolution of multiple independent cancer founders from the non-cancer ancestors was common, contributing to intratumour heterogeneity. The number of driver events did not correlate with histology, suggesting the role of local microenvironments and/or epigenetic driver events. A similar evolutionary pattern was also observed in another case evolving from an AKT1-mutated founder. Taken together, our findings provide new insight into how breast cancer evolves.

Possible roles of human mast cells in the formation of xanthelasma palpebrarum.

Cutaneous xanthoma consist of foam cells that originate from monocytes or macrophages and accumulate in perivascular areas of the skin. The main component of these cells is oxidized low-density lipoprotein (oxLDL). In this study, we show that mast cells surround the accumulated foam cells, suggesting their involvement in xanthoma formation. Coculture of THP-1 or U937 monocytes with the human mast cell line LUVA upregulated their uptake of oxLDL. Positive staining for intracellular cell adhesion molecule-1 (ICAM-1) at the borders between mast cells and foam cells was seen in pathological specimens of the most common cutaneous xanthoma, xanthelasma palpebrarum, and in cocultures. In the latter, ICAM1 messenger RNA levels were upregulated. The administration of anti-ICAM-1 blocking antibody inhibited the increase in oxLDL uptake by THP-1 or U937 monocytes cocultured with LUVA. Taken together, these results suggest a role for mast cells in the formation of xanthelasma palpebrarum and the involvement of ICAM-1 in this process.

RUNX1-Survivin Axis Is a Novel Therapeutic Target for Malignant Rhabdoid Tumors.

Malignant rhabdoid tumor (MRT) is a highly aggressive pediatric malignancy with no effective therapy. Therefore, it is necessary to identify a target for the development of novel molecule-targeting therapeutic agents. In this study, we report the importance of the runt-related transcription factor 1 (RUNX1) and RUNX1-Baculoviral IAP (inhibitor of apoptosis) Repeat-Containing 5 (BIRC5/survivin) axis in the proliferation of MRT cells, as it can be used as an ideal target for anti-tumor strategies. The mechanism of this reaction can be explained by the interaction of RUNX1 with the RUNX1-binding DNA sequence located in the survivin promoter and its positive regulation. Specific knockdown of RUNX1 led to decreased expression of survivin, which subsequently suppressed the proliferation of MRT cells in vitro and in vivo. We also found that our novel RUNX inhibitor, Chb-M, which switches off RUNX1 using alkylating agent-conjugated pyrrole-imidazole polyamides designed to specifically bind to consensus RUNX-binding sequences (5'-TGTGGT-3'), inhibited survivin expression in vivo. Taken together, we identified a novel interaction between RUNX1 and survivin in MRT. Therefore the negative regulation of RUNX1 activity may be a novel strategy for MRT treatment.

A RUNX-targeted gene switch-off approach modulates the BIRC5/PIF1-p21 pathway and reduces glioblastoma growth in mice.

Glioblastoma is the most common adult brain tumour, representing a high degree of malignancy. Transcription factors such as RUNX1 are believed to be involved in the malignancy of glioblastoma. RUNX1 functions as an oncogene or tumour suppressor gene with diverse target genes. Details of the effects of RUNX1 on the acquisition of malignancy in glioblastoma remain unclear. Here, we show that RUNX1 downregulates p21 by enhancing expressions of BIRC5 and PIF1, conferring anti-apoptotic properties on glioblastoma. A gene switch-off therapy using alkylating agent-conjugated pyrrole-imidazole polyamides, designed to fit the RUNX1 DNA groove, decreased expression levels of BIRC5 and PIF1 and induced apoptosis and cell cycle arrest via p21. The RUNX1-BIRC5/PIF1-p21 pathway appears to reflect refractory characteristics of glioblastoma and thus holds promise as a therapeutic target. RUNX gene switch-off therapy may represent a novel treatment for glioblastoma.

Case Report: A Case of Renal Cell Carcinoma Unclassified With Medullary Phenotype Exhibiting a Favorable Response to Combined Immune Checkpoint Blockade.

Renal cell carcinoma unclassified with medullary phenotype (RCCU-MP) is an extremely rare variant of kidney cancer with poor prognosis. Recently, immune checkpoint inhibitors (ICIs) have been the mainstay of treatment for advanced clear cell renal cell carcinoma (RCC). However, the efficacy of ICI in the treatment of RCCU-MP remains unclear. Here, we report about a 63-year-old Japanese man who was referred to our hospital with a diagnosis of RCC of the left kidney with multiple-lymph node involvement (cT3aN1M1). The patient underwent nephrectomy with lymph node biopsy, which was histopathologically diagnosed as RCCU-MP. Thereafter, he received combined immune checkpoint blockade with nivolumab and ipilimumab. After induction therapy, follow-up computed tomography revealed shrinkage of the metastatic lymph nodes. Moreover, the patient was relieved of his subjective symptoms and his performance status improved. However, after 15 months, maintenance ICI therapy was discontinued because of disease progression, and the patient died 28 months after diagnosis. Longitudinal analysis of peripheral blood mononuclear cells revealed increased stem cell memory and central memory CD8+ T-cell subsets during response to therapy and enhanced expression of exhaustion markers on CD8+ T cells upon treatment resistance. Combined immune checkpoint blockade could be effective in the treatment of metastatic RCCU-MP.

Decidualization of Stromal Cells Promotes Involvement of Mast Cells in Successful Human Pregnancy by Increasing Stem Cell Factor Expression.

Decidualization of endometrial stromal cells and the presence of immunocompetent cells, including human mast cells, play important roles in the establishment of pregnancy. In the present study, the effects of decidualization of endometrial stromal cells on the function of decidual mast cells were elucidated. The in vitro assay revealed that decidualization of an endometrial stromal cell line, T HESCs, increased stem cell factor (SCF) mRNA expression. Decidualization of T HESCs enhanced the production of leukemia inhibitory factor (LIF), and the migration of LAD2 cells when co-cultured with T HESCs and LAD2 cells. In addition, decidualization of T HESCs enhanced cell migration in a human trophoblast cell line, HTR-8/SVneo, increased CD9 expression, a marker for extravillous trophoblast (EVT) differentiation, and decreased the secretion of ß human chorionic gonadotropin (hCG), a marker for syncytiotrophoblast (ST) differentiation, when co-cultured with T HESCs, LAD2 cells, and HTR-8/SVneo cells, in a LIF-dependent manner. Histological samples from uterine pregnancies, including decidual stromal cells, showed increased SCF mRNA expression, mast cell numbers and LIF mRNA expression thereof compared with tubal pregnancy. SCF produced by decidual stromal cells enhanced the migration and LIF production of mast cells, and promoted the migration and differentiation of trophoblasts to increase the likelihood of successful human pregnancy.

CCL2‒CCR2 Signaling in the Skin Drives Surfactant-Induced Irritant Contact Dermatitis through IL-1ß‒Mediated Neutrophil Accumulation.

Surfactant-induced cumulative irritant contact dermatitis (ICD) is a common and clinically important skin disorder. CCL2 is known to mediate inflammation after tissue damage in various organs. Thus, we investigated whether and how CCL2 contributes to the development of murine cumulative ICD induced by a common surfactant, SDS. Wild-type mice treated topically with SDS for 6 consecutive days developed skin inflammation that recapitulated the features of human cumulative ICD, including barrier disruption, epidermal thickening, and neutrophil accumulation. CCL2 was upregulated in SDS-treated skin, and local CCL2 blockade attenuated SDS-induced ICD. SDS-induced ICD and neutrophil accumulation were also attenuated in mice deficient in CCR2, the receptor for CCL2. Neutrophil depletion alleviated SDS-induced ICD, suggesting that impaired neutrophil accumulation was responsible for the amelioration of ICD in CCR2-deficient mice. In RNA-sequencing analyses of SDS-treated skin, the expression levels of Il1b in Ccr2-deficient mice were highly downregulated compared with those in wild-type mice. Furthermore, the intradermal administration of IL-1ß in the SDS-treated skin of CCR2-deficient mice restored the local accumulation of neutrophils and the development of ICD. Collectively, our results suggest that CCL2‒CCR2 signaling in the skin critically promotes the development of SDS-induced ICD by inducing IL-1ß expression for neutrophil accumulation.

RUNX1 transactivates BCR-ABL1 expression in Philadelphia chromosome positive acute lymphoblastic leukemia.

The emergence of tyrosine kinase inhibitors as part of a front-line treatment has greatly improved the clinical outcome of the patients with Ph+ acute lymphoblastic leukemia (ALL). However, a portion of them still become refractory to the therapy mainly through acquiring mutations in the BCR-ABL1 gene, necessitating a novel strategy to treat tyrosine kinase inhibitor (TKI)-resistant Ph+ ALL cases. In this report, we show evidence that RUNX1 transcription factor stringently controls the expression of BCR-ABL1, which can strategically be targeted by our novel RUNX inhibitor, Chb-M'. Through a series of in vitro experiments, we identified that RUNX1 binds to the promoter of BCR and directly transactivates BCR-ABL1 expression in Ph+ ALL cell lines. These cells showed significantly reduced expression of BCR-ABL1 with suppressed proliferation upon RUNX1 knockdown. Moreover, treatment with Chb-M' consistently downregulated the expression of BCR-ABL1 in these cells and this drug was highly effective even in an imatinib-resistant Ph+ ALL cell line. In good agreement with these findings, forced expression of BCR-ABL1 in these cells conferred relative resistance to Chb-M'. In addition, in vivo experiments with the Ph+ ALL patient-derived xenograft cells showed similar results. In summary, targeting RUNX1 therapeutically in Ph+ ALL cells may lead to overcoming TKI resistance through the transcriptional regulation of BCR-ABL1. Chb-M' could be a novel drug for patients with TKI-resistant refractory Ph+ ALL.

The Expression of Insulin-Like Growth Factor 2 Messenger RNA-Binding Protein 3 in Langerhans Cell Histiocytosis and Langerhans Cell Sarcoma.

Langerhans cell neoplasms, which include Langerhans cell histiocytosis and Langerhans cell sarcoma, are tumors that originate from dendritic cells. Langerhans cell sarcoma is defined as a high-grade neoplasm with overtly malignant cytological features and the Langerhans cell-like phenotype, and generally has a poorer prognosis and more aggressive phenotype than Langerhans cell histiocytosis. Insulin-like growth factor 2 messenger RNA-binding protein 3 (IGF2BP3 or IMP3) is an oncofetal protein that is expressed in various cancer types; its expression is often associated with a poor prognosis and aggressive phenotype. Here, we used immunohistochemistry to evaluate IGF2BP3 expression in Langerhans cell neoplasms. IGF2BP3 expression was scored as negative (< 1%) or positive (≥ 1%) by immunohistochemistry. All 4 patients with Langerhans cell sarcoma (100%) and 6 of 22 pediatric (age < 18 years) patients with Langerhans cell histiocytosis (27.3%) had positive results for IGF2BP3; however, 16 of 22 pediatric patients with Langerhans cell histiocytosis (72.7%) and all 15 adult (age ≥ 18 years) patients with Langerhans cell histiocytosis (100%) had a negative result. Among patients with Langerhans cell histiocytosis, IGF2BP3 expression was independent of sex, location, prognosis, and BRAF V600E staining results. Taken together, these results indicate that IGF2BP3 expression may be a helpful marker for distinguishing Langerhans cell sarcoma from Langerhans cell histiocytosis in adult patients.

Kinetic information from dynamic contrast-enhanced MRI enables prediction of residual cancer burden and prognosis in triple-negative breast cancer: a retrospective study.

This study aimed to evaluate the predictions of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) for prognosis of triple-negative breast cancer (TNBC), especially with residual disease (RD) after preoperative chemotherapy. This retrospective analysis included 74 TNBC patients who received preoperative chemotherapy. DCE-MRI findings from three timepoints were examined: at diagnosis (MRIpre), at midpoint (MRImid) and after chemotherapy (MRIpost). These findings included cancer lesion size, washout index (WI) as a kinetic parameter using the difference in signal intensity between early and delayed phases, and time-signal intensity curve types. Distant disease-free survival was analysed using the log-rank test to compare RD group with and without a fast-washout curve. The diagnostic performance of DCE-MRI findings, including positive predictive value (PPV) for pathological responses, was also calculated. RD without fast washout curve was a significantly better prognostic factor, both at MRImid and MRIpost (hazard ratio = 0.092, 0.098, p < 0.05). PPV for pathological complete remission at MRImid was 76.7% by the cut-off point at negative WI value or lesion size = 0, and 66.7% at lesion size = 0. WI and curve types derived from DCE-MRI at the midpoint of preoperative chemotherapy can help not only assess tumour response but also predict prognosis.

Imaging findings of granulocyte colony-stimulating factor-producing tumors: a case series and review of the literature.

Granulocyte colony-stimulating factor (G-CSF)-producing tumors have an aggressive clinical course. Here, we report five cases of G-CSF-producing tumors and review the literature, focusing on imaging findings related to tumor-produced G-CSF. In addition to our cases, we identified 30 previous reports of G-CSF-producing tumors on which 18F-fluorodeoxyglucose positron emission tomography (FDG-PET)/CT, bone scintigraphy, or evaluation of bone marrow MR findings was performed. White blood cell count, serum C-reactive protein, and serum interleukin-6 were elevated in all cases for which these parameters were measured. G-CSF-producing tumors presented large necrotic masses (mean diameter 83.2 mm, range 17-195 mm) with marked FDG uptake (mean maximum standardized uptake value: 20.09). Diffuse FDG uptake into the bone marrow was shown in 28 of the 31 cases in which FDG-PET/CT was performed. The signal intensity of bone marrow suggested marrow reconversion in all seven MRI-assessable cases. Bone scintigraphy demonstrated no significant uptake, except in two cases with bone metastases. Splenic FDG uptake was increased in 8 of 10 cases in which it was evaluated. These imaging findings may reflect the effects of tumor-produced G-CSF. The presence of G-CSF-producing tumors should be considered in patients with cancer who show these imaging findings and marked inflammatory features of unknown origin.

Eribulin-based neoadjuvant chemotherapy for triple-negative breast cancer patients stratified by homologous recombination deficiency status: a multicenter randomized phase II clinical trial.

PURPOSE: To investigate clinical usefulness of eribulin-based neoadjuvant chemotherapy in triple-negative breast cancer (TNBC) patients. METHODS: Patients in group A (aged < 65 years with homologous recombination deficiency, HRD, score ≥ 42, or those at any age with germline BRCA mutation, gBRCAm) were randomized to 4 cycles of paclitaxel plus carboplatin (group A1) or eribulin plus carboplatin (group A2), followed by 4 cycles of anthracycline. Patients in group B (aged < 65 years with HRD score < 42, or aged ≥ 65 years without gBRCAm) were randomized to 6 cycles of eribulin plus cyclophosphamide (group B1) or eribulin plus capecitabine (group B2); non-responders to the first 4 cycles of the eribulin-based therapy received anthracycline. Primary endpoint was pCR rate (ypT0-is, ypN0; centrally confirmed). Main secondary endpoint was safety. RESULTS: The full analysis set comprised 99 patients. The pCR rate was 65% (90% CI, 46%-81%) and 45% (27%-65%) in groups A1 and A2, respectively, and 19% (8%-35%) in both groups B1 and B2. No major difference was seen in secondary endpoints, but peripheral neuropathy incidence was 74% in group A1, whereas it was 32%, 22%, and 26% in groups A2, B1, and B2, respectively. CONCLUSIONS: In patients aged < 65 years with high HRD score or gBRCAm, weekly paclitaxel plus carboplatin and eribulin plus carboplatin followed by anthracycline resulted in a pCR rate of > 60% and > 40%, respectively, suggesting potential usefulness of patient stratification using HRD; pCR tended to be low in patients with HRD-negative tumors. Neurotoxicity was less frequent with the eribulin-based regimen. TRIAL REGISTRATION: The study has been registered with the University Hospital Medical Information Network Clinical Trials Registry ( http://www.umin.ac.jp/ctr/index-j.htm ) with unique trial number UMIN000023162. The Japan Breast Cancer Research Group trial number is JBCRG-22.

PD-L1 on mast cells suppresses effector CD8+ T-cell activation in the skin in murine contact hypersensitivity.

BACKGROUND: The programmed cell death-1 (PD-1)/programmed death ligand 1 (PD-L1) pathway is known to inhibit the activation of effector CD8+ T cells. However, just how this regulatory pathway is involved in the pathophysiology of CD8+ T-cell-mediated inflammatory skin diseases remains unclear. OBJECTIVE: Our aim was to elucidate the mechanisms by which the PD-1/PD-L1 pathway exerts its regulatory roles in CD8+ T-cell-mediated cutaneous immune responses. METHODS: PD-L1-deficient (Pdl1-/-) mice were used for the murine contact hypersensitivity model. Inflammatory responses such as IFN-γ production from CD8+ T cells in the skin was evaluated by flow cytometry. RESULTS: Compared with wild-type mice, Pdl1-/- mice exhibited exacerbated ear swelling and increased numbers of IFN-γ+ CD8+ T cells in the skin. Adoptive T-cell transfer experiments revealed the involvement of the PD-1/PD-L1 pathway in the elicitation phase of contact hypersensitivity. Bone marrow chimera experiments showed that PD-L1 on radioresistant cells was responsible for this regulatory pathway. Flow cytometric analysis revealed that among the radioresistant cells in the skin, PD-L1 was most highly expressed on mast cells (MCs) before and after elicitation. Administration of anti-PD-L1 blocking antibody during the elicitation phase significantly enhanced ear swelling responses and increased the number of IFN-γ+CD8+ T cells in the skin of wild-type mice, whereas no significant effects were observed in MC-deficient (WBB6F1/J-KitW/KitW-v/J and C57BL/6-KitW-sh/W-sh) mice. The high level of expression of PD-L1 on human skin MCs was confirmed by database analysis and immunohistochemical analysis. CONCLUSION: PD-L1 on MCs negatively regulates CD8+ T-cell activation in the skin.

Neonatal Fc receptor induces intravenous immunoglobulin growth suppression in Langerhans cell histiocytosis.

The neonatal Fc receptor (FcRn) plays a role in trafficking IgG and albumin and is thought to mediate intravenous immunoglobulin (IVIG) therapy for certain diseases. IVIG can be used for the treatment of human Langerhans cell histiocytosis (LCH); however, the mechanism remains unclear. The expression and function of FcRn protein have not been studied in LCH, though the expression of FcRn messenger RNA (mRNA) have been reported. In this report, we confirmed the expression of FcRn in 26 of 30 pathological cases (86.7%) diagnosed immunohistochemically as LCH. The expression was independent of age, gender, location, multi- or single-system, and the status of BRAFV600E immunostaining. We also confirmed the expression of FcRn mRNA and protein in the human LCH-like cell line, ELD-1. FcRn suppressed albumin consumption and growth of IVIG preparation-treated ELD-1 cells, but not of IVIG preparation-untreated or FcRn-knockdown ELD-1 cells. In addition, FITC-conjugated albumin was taken into Rab11-positive recycle vesicles in mock ELD-1 cells but not in FcRn-knockdown ELD-1 cells. IVIG preparation prolonged this status in mock ELD-1 cells. Therefore, ELD-1 recycled albumin via FcRn and albumin was not used for metabolism. Our results increase our understanding of the molecular mechanism of IVIG treatment of LCH.