Plasma cell differentiation is regulated by the expression of histone variant H3.3.

The differentiation of B cells into plasma cells is associated with substantial transcriptional and epigenetic remodeling. H3.3 histone variant marks active chromatin via replication-independent nucleosome assembly. However, its role in plasma cell development remains elusive. Herein, we show that during plasma cell differentiation, H3.3 is downregulated, and the deposition of H3.3 and chromatin accessibility are dynamically changed. Blockade of H3.3 downregulation by enforced H3.3 expression impairs plasma cell differentiation in an H3.3-specific sequence-dependent manner. Mechanistically, enforced H3.3 expression inhibits the upregulation of plasma cell-associated genes such as Irf4, Prdm1, and Xbp1 and maintains the expression of B cell-associated genes, Pax5, Bach2, and Bcl6. Concomitantly, sustained H3.3 expression prevents the structure of chromatin accessibility characteristic for plasma cells. Our findings suggest that appropriate H3.3 expression and deposition control plasma cell differentiation.

Oxidative stress in peroxisomes induced by androgen receptor inhibition through peroxisome proliferator-activated receptor promotes enzalutamide resistance in prostate cancer.

Androgen receptor (AR)-targeting therapy induces oxidative stress in prostate cancer. However, the mechanism of oxidative stress induction by AR-targeting therapy remains unclear. This study investigated the mechanism of oxidative stress induction by AR-targeting therapy, with the aim to develop novel therapeutics targeting oxidative stress induced by AR-targeting therapy. Intracellular reactive oxygen species (ROS) was examined by fluorescence microscopy and flow cytometry analysis. The effects of silencing gene expression and small molecule inhibitors on gene expression and cytotoxic effects were examined by quantitative real-time PCR and cell proliferation assay. ROS induced by androgen depletion co-localized with peroxisomes in prostate cancer cells. Among peroxisome-related genes, PPARA was commonly induced by AR inhibition and involved in ROS production via PKC signaling. Inhibition of PPARα by specific siRNA and a small molecule inhibitor suppressed cell proliferation and increased cellular sensitivity to the antiandrogen enzalutamide in prostate cancer cells. This study revealed a novel pathway by which AR inhibition induced intracellular ROS mainly in peroxisomes through PPARα activation in prostate cancer. This pathway is a promising target for the development of novel therapeutics for prostate cancer in combination with AR-targeting therapy such as antiandrogen enzalutamide.

NR5A2/HSD3B1 pathway promotes cellular resistance to second-generation antiandrogen darolutamide.

This study investigated cellular mechanisms in steroidogenesis responsible for treatment resistance to the novel antiandrogen agent darolutamide in prostate cancer. HSD3B1 was overexpressed in darolutamide-resistant cells and induced by darolutamide treatment and AR knockdown. Inversely, HSD3B1 knockdown increased cellular sensitivity to darolutamide. Similarly, its upstream regulator NR5A2 was up-regulated in darolutamide-resistant cells and induced by darolutamide treatment and AR knockdown. Inversely, NR5A2 knockdown and NR5A2 inhibitor ML180 decreased expression of various steroidogenic enzymes including HSD3B1, leading to increased cellular sensitivity to darolutamide. The NR5A2/HSD3B1 pathway promoted cellular resistance to darolutamide and targeting NR5A2/HSD3B1 pathway is a promising therapeutic strategy to overcome darolutamide resistance.

Correlation between extended pelvic lymph node dissection and urinary incontinence at early phase after robot-assisted radical prostatectomy.

OBJECTIVES: To investigate the impact of extended pelvic lymph node dissection (ePLND) on urinary incontinence (UI) at early post-surgery robot-assisted radical prostatectomy (RARP). METHODS: Patients who underwent RARP without cavernous nerve sparing were included between 2014 and 2019. Patient data were obtained prospectively. The associations between ePLND and postoperative urinary continence were defined as a maximum of one daily pad use. International prostate symptom score (IPSS) was examined. Expression of synaptophysin and tyrosine hydroxylase (TH) in perilymph node adipose tissue (PLA) was evaluated by immunohistochemistry. RESULTS: In total, 186 and 163 patients underwent RARP with and without ePLND. Urinary continence rate at 1 month postoperatively among patients with ePLND was lower than those without ePLND (24.1% vs. 35.1%, p < 0.05), however, not significantly different at 3, 6, and 12 months after RARP (57.4 vs. 62.6%, 73.1 vs. 74.2%, and 83.0 vs. 81.2%, respectively). Total and voiding plus postvoiding IPSS scores at 1 month were higher in patients with ePLND than in those without ePLND (14.5 ± 0.5 vs. 13.6 ± 0.6, 7.0 ± 0.3 vs. 6.2 ± 0.4, respectively, p < 0.05). In univariate and multivariate analyses, larger prostate volume and ePLND were factors associated with an increased UI rate. Among patients who underwent ePLND, synaptophysin and TH-positive nerve fibers were detected in PLA. CONCLUSIONS: Detection of synaptophysin and TH-immunopositive nerves suggested denervation of sympathetic and peripheral nerves caused by ePLND might be associated with a higher UI rate and poor urinary symptoms at an early stage after RARP.

An oral first-in-class small molecule RSK inhibitor suppresses AR variants and tumor growth in prostate cancer.

Ribosomal S6 kinase has been shown to play a key role in cellular resistance to endocrine therapy in prostate cancer through its regulation of YB-1/androgen receptor (AR) signaling. PMD-026, an oral first-in-class small molecule kinase inhibitor, is the first identified ribosomal S6 kinase inhibitor. This study investigated the effect of PMD-026 on YB-1/AR signaling and its antitumor effect in prostate cancer in vitro and in vivo. Castration-resistant prostate cancer 22Rv1 cells that express high-level AR variants were used in this study. The effect of PMD-026 on YB-1/AR signaling was investigated by quantitative real-time PCR and western blot analysis. The effects of PMD-026 on prostate cancer cells were investigated by cytotoxicity analysis, apoptosis assay, and cell cycle assay in vitro and a mouse castration model in vivo. PMD-026 decreased YB-1 phosphorylation as well as AR V7 mRNA and AR variant expressions in 22Rv1 cells. PMD-026 suppressed cell proliferation alone and in combination with the second-generation antiandrogens enzalutamide and darolutamide by inducing cellular apoptosis and G2/M arrest. In a mouse xenograft model, PMD-026 suppressed tumor growth, and the combination of PMD-026 and enzalutamide inhibited tumor growth more prominently than single treatments. Our results demonstrate an excellent antitumor effect of the novel ribosomal S6 kinase inhibitor PMD-026 and the combination effect with the antiandrogen enzalutamide in castration-resistant prostate cancer. These findings warrant a clinical trial of PMD-026 in prostate cancer patients.

Clinical impact of HSD3B1 polymorphism by metastatic volume and somatic HSD3B1 alterations in advanced prostate cancer.

This study aimed to investigate the significance of HSD3B1 gene status including germline polymorphism and somatic alterations in prostate cancer. Patients with prostate cancer treated with androgen-deprivation therapy, as well as tissues from metastatic prostate cancer, were included. Genomic DNA was extracted from cancer tissues and whole blood samples, and HSD3B1 (rs1047303, 1245C) was genotyped by Sanger sequencing. The association of HSD3B1 genotype with progression-free survival according to metastatic volume was examined. Copy number alteration and gene expression of HSD3B1 were examined in prostate cancer cells and public datasets. Among 194 patients, 121 and 73 patients were categorized into low- and high-volume diseases respectively. In multivariate analysis, the adrenal-permissive genotype (AC/CC) was significantly associated with increased risk of progression compared with the adrenal-restrictive genotype (AA) in low volume, but not high-volume diseases. Somatic mutation in HSD3B1 was detected at least in two cases of castration-resistant prostate cancer tissues. HSD3B1 amplification and overexpression were detected in castration-resistant prostate cancer cells and tissues. The current findings suggest that both germline and somatic alterations of HSD3B1 may cooperatively promote castration resistance in prostate cancer and HSD3B1 as a promising biomarker for precision medicine, warranting further investigations.

Differential Impact of TGFB1 Variation by Metastatic Status in Androgen-Deprivation Therapy for Prostate Cancer.

Transforming growth factor-ß1 (TGF-ß1) plays a dual role in cancer, acting as a tumor suppressor in the early stage of cancer development and as a tumor promoter in the later stage of cancer progression in various cancers. In this study, we investigated the association between genetic polymorphisms in TGFB1 and clinicopathological characteristics or oncological outcome in prostate cancer cases treated with androgen-deprivation therapy (ADT) according to metastasis status. Japanese male patients with hormone-sensitive prostate cancer treated with ADT from 1993 to 2005 were included in this study. Genomic DNA was obtained from whole blood samples, and genotyping of TGFB1 (rs2241716 and rs4803455) was performed by PCR-based technique. No significant association between genetic polymorphisms in TGFB1 (rs2241716 and rs4803455) and clinicopathological parameters or prognosis was observed in patients with non-metastatic disease. In patients with metastatic disease, Gleason score in CT/TT carriers (rs2241716) and CA/AA carriers (rs4803455) was unfavorable compared with CC carriers. In addition, the CT/TT alleles in rs2241716 (hazard ratio, 1.82; 95% confidence interval, 1.12-2.94; P = 0.015) and the CA/AA alleles in rs4803455 (hazard ratio, 1.75; 95% confidence interval, 1.03-2.98; P = 0.040) were associated with a higher risk of progression during ADT compared with the CC allele in patients with metastatic disease. TGFB1 genetic variations were associated with adverse characteristics and progression risk in ADT among patients with metastatic disease, but not those with non-metastatic disease, supporting a distinct role of TGF-ß signaling between non-metastatic and metastatic prostate cancer.

Gene amplification of YB-1 in castration-resistant prostate cancer in association with aberrant androgen receptor expression.

Although Y-box binding protein-1 (YB-1) is known to be overexpressed in prostate cancer, especially castration-resistant prostate cancer (CRPC), the mechanism of its overexpression remains unclear. We aimed to elucidate the mechanism of YB-1 overexpression in CRPC. Gene amplification in CRPC cells and tissues was examined by public database analysis, and digital PCR. The significance of YB-1 amplification for the YB-1/androgen receptor (AR) axis and prognosis was examined by public database analysis and immunohistochemistry. YB-1 amplification was mainly observed in CRPC tissues by public database analysis and confirmed in CRPC cells and tissues by digital PCR. Expression of YB-1 was increased in CRPC tissues compared with treatment-naïve tissues. Furthermore, YB-1 and phosphorylated YB-1 levels were associated with AR and AR V7 expression levels. Finally, YB-1 amplification was associated with poor outcomes in CRPC. Taken together, the present findings suggest that YB-1 amplification contributes to progression to CRPC through regulation of AR and AR V7 expressions, and that YB-1 is a promising therapeutic target in CRPC.

New mouse model of underactive bladder developed by placement of a metal ring around the bladder neck.

OBJECTIVE: To develop a new mouse model of underactive bladder (UAB) caused by chronic bladder outlet obstruction (BOO). METHODS: BOO was created in 6-week-old male C57BL/6 mice using surgery to loosely place a silver jump ring around the bladder neck of each mouse. Micturition behavior (assessed with a metabolic cage) and cystometry were used to evaluate bladder function at 8 and 16 weeks after BOO. Following completion of the functional studies, the bladders of the mice were excised, weighed, and subjected to histological analysis. RESULTS: Micturition behavior analysis showed that mice subjected to BOO for 16 weeks had a lower frequency of micturition (7.3 ± 1.1 vs 12.5 ± 3.0 times/d, P < .05) and volume per void (106.0 ± 0.1 vs 133.9 ± 3.2 µL, P < .05) than mice subjected to BOO for 8 weeks. Cystometry revealed that mice subjected to BOO for 16 weeks had lower baseline pressure (8.4 ± 0.6 vs 14.0 ± 0.7 cmH2 O, P < .01) and micturition pressure (13.9 ± 1.1 vs 42.8 ± 1.7 cmH2 O, P < .05) than mice subjected to BOO for 8 weeks. BOO caused progressive increases in bladder mass and collagen deposition over time. CONCLUSIONS: We successfully established a novel mouse model of UAB using surgery to place a silver jump ring loosely on the bladder neck. BOO initially induced bladder overactivity but subsequently resulted in UAB due to deterioration of detrusor smooth muscle contractility and progressive deposition of collagen in the bladder wall.

The role of adipocytokines and their receptors in bladder cancer: expression of adiponectin or leptin is an independent prognosticator.

Adipocytokines such as leptin and adiponectin have functions in metabolism as well as the development and progression of various types of malignancies. However, little is known about their role in bladder cancer. In this study, we investigated whether leptin, adiponectin, and their receptors have an impact on bladder cancer outgrowth and the mechanisms involved. We performed immunohistochemistry for leptin, leptin receptor (Ob-R), adiponectin, and adiponectin receptors (AdipoR1, AdipoR2) in bladder cancer tissue microarrays. Wound healing assay and western blot were then performed in human bladder cancer lines. The positive rates (0 vs 1+/2+/3+) of Ob-R (P=0.004), adiponectin (P<0.001), AdipoR1 (P=0.016), and AdipoR2 (P<0.001) expression were significantly higher in bladder tumors than in benign urothelial tissues. Strong (3+) leptin expression tended to be present more often in tumors (10.2%; P=0.079) than in benign tissues (3.2%). Multivariate analysis revealed a lower risk of recurrence (hazard ratio [HR]=0.432; 95% confidence interval [CI]=0.198-0.942; P=0.034) in patients with an adiponectin-positive non-muscle-invasive tumor and a higher risk of progression (HR=5.148, 95% CI=1.190-22.273; P=0.028) in patients with a leptin-positive muscle-invasive tumor. Treatment of two bladder cancer cell lines with a synthetic adiponectin inhibited their migration and the expressions of phospho-NF-κB, NF-κB, snail, slug, Y-box-binding protein 1, and COX-2, whereas leptin showed reverse effects. Downregulation of adiponectin expression and upregulation of leptin expression were independent predictors for the recurrence of non-muscle-invasive bladder tumors and progression of muscle-invasive bladder tumors, respectively. In summary, synthetic adiponectin might exhibit antitumor activity against bladder cancer.

Polymorphisms in androgen metabolism genes with serum testosterone levels and prognosis in androgen-deprivation therapy.

OBJECTIVE: Androgen metabolism is a key component in therapeutic resistance to androgen deprivation therapy (ADT). This study aimed to reveal the significance of genetic polymorphisms in genes involved in androgen metabolism, including CYP17A1, AKR1C3, and HSD17B, on serum testosterone levels during ADT, as well as the prognosis of men undergoing ADT for metastatic prostate cancer (CaP). MATERIALS AND METHODS: This study included 104 Japanese patients with metastatic CaP, for whom serum testosterone data during ADT were available for 80 patients. The association of CYP17A1 (rs743572), AKR1C3 (rs12529), HSD17B1 (rs605059), HSD17B3 (rs2066479), and HSD17B4 (rs7737181) with serum testosterone levels during ADT and prognosis (progression-free survival and overall survival) was examined. Enzymatic activity in AKR1C3 H5Q was examined using recombinant protein. RESULTS: Homozygous wild-type (GG allele; median [interquartile range], 12.0 ng/ml [8.0-19.0 ng/ml]) AKR1C3 rs12529 was associated with higher serum testosterone levels during ADT compared with variant-type (GC/CC alleles; median [interquartile range], 9.0 ng/ml [6.4-10.8 ng/ml]). Consistently, variant-type (GC/CC alleles) AKR1C3 rs12529 showed significantly lower risk of progression (hazard ratio [95% confidence interval], 0.47 [0.24-0.96], P = 0.039) compared with homozygous wild-type (GG allele) on multivariate analysis. Meanwhile, other genetic variations were associated with neither serum testosterone during ADT nor prognosis. Enzyme activity of wild-type AKR1C3 was comparable to the H5Q mutant. CONCLUSIONS: Taken together, this study demonstrated that AKR1C3 polymorphism, which was associated with serum testosterone levels during ADT, may be a prognostic factor of the progression to castration-resistant prostate cancer in Japanese men with metastatic CaP.

High-throughput screen identifies 5-HT receptor as a modulator of AR and a therapeutic target for prostate cancer.

BACKGROUND: Eradication of persistent androgen receptor (AR) activity in castration-resistant prostate cancer may be a promising strategy to overcome castration resistance. We aimed to identify novel compounds that inhibit AR activity and could be potential therapeutic agents for prostate cancer. METHODS: A high-throughput screening system involving cell lines stably expressing AR protein and AR-responsive luciferase was employed for the 1260 compound library. Molecular and antitumor effects on candidate pathways that interacted with AR signaling were examined in prostate cancer cells expressing AR. RESULTS: The high-throughput screening identified various potential compounds that interfered with AR signaling through known and novel pathways. Among them, a 5-hydroxytryptamine 5A (5-HT5A) receptor antagonist suppressed AR activity through protein kinase A signaling, which was confirmed by 5-HT5A receptor knockdown. Consistently, 5-HT5A receptor inhibitors showed cytotoxic effects toward prostate cancer cells. CONCLUSIONS: Taken together, this study identifies 5-HT5A receptor as a promising therapeutic target for prostate cancer via its interaction with AR signaling.

S100A4 Protein Is Essential for the Development of Mature Microfold Cells in Peyer's Patches.

Intestinal microfold cells (M cells) in Peyer's patches are a special subset of epithelial cells that initiate mucosal immune responses through uptake of luminal antigens. Although the cytokine receptor activator of nuclear factor-κB ligand (RANKL) expressed on mesenchymal cells triggers differentiation into M cells, other environmental cues remain unknown. Here, we show that the metastasis-promoting protein S100A4 is required for development of mature M cells. S100A4-producing cells are a heterogenous cell population including lysozyme-expressing dendritic cells and group 3 innate lymphoid cells. We found that in the absence of DOCK8, a Cdc42 activator critical for interstitial leukocyte migration, S100A4-producing cells are reduced in the subepithelial dome, resulting in a maturation defect of M cells. While S100A4 promotes differentiation into mature M cells in organoid culture, genetic inactivation of S100a4 prevents the development of mature M cells in mice. Thus, S100A4 is a key environmental cue that regulates M cell differentiation in collaboration with RANKL.

Genetic Polymorphism in Sex Hormone-binding Globulin With a Prognosis of Androgen Deprivation Therapy in Metastatic Prostate Cancer Among Japanese Men.

INTRODUCTION: Testosterone suppression in serum during androgen deprivation therapy (ADT) can affect the oncologic outcome of ADT. Although genetic variants in sex hormone-binding globulin (SHBG) were reported to be correlated with serum testosterone level, the association with serum testosterone during ADT remains unclear. Therefore, this study investigated the impact of a missense polymorphism in the SHBG gene among men treated with primary ADT for metastatic prostate cancer. PATIENTS AND METHODS: This study included 104 Japanese men with metastatic prostate cancer. The association of SHBG gene polymorphism (rs6259, D356N) with clinicopathologic parameters including serum testosterone levels during ADT, as well as prognosis, including progression-free survival and overall survival, was examined. RESULTS: The serum testosterone levels during ADT were comparable between men carrying the homozygous wild-type (GG) and heterozygous/homozygous variant (GA/AA) in the SHBG gene. When adjusted for age, Gleason score, initial prostate-specific antigen, and clinical T-stage, the heterozygous/homozygous variant (GA/AA) in the SHBG gene was associated with a higher risk of progression (hazard ratio, 2.20; 95% confidence interval, 1.10-4.18; P = .027) and any-cause death (hazard ratio, 3.21; 95% confidence interval, 1.31-7.35; P = .012). CONCLUSIONS: This study suggested genetic variation in SHBG (rs6259) might be an independent prognostic biomarker among men treated with primary ADT for metastatic prostate cancer.

Cigarette smoking augments androgen receptor activity and promotes resistance to antiandrogen therapy.

BACKGROUND: Cigarette smoking is associated with worse outcomes in prostate cancer, whose growth is dependent on androgen receptor (AR) signaling. We aimed to elucidate the biological effect of cigarette smoking on AR signaling and its clinical influence on oncological outcome. METHODS: Gene expression levels after exposure to tobacco smoke condensate (TSC) were evaluated by quantitative real-time polymerase chain reaction and Western blot analysis in prostate cancer cells. Cellular sensitivities to enzalutamide and docetaxel after TSC exposure were evaluated using a prostate cancer cell proliferation assay. Prognosis was compared between current smokers and nonsmokers when treated with AR-axis-targeting (ARAT) agent enzalutamide and docetaxel. RESULTS: Expression of AR variants as well as prostate-specific antigen was augmented after TSC exposure, which occurred after Akt phosphorylation. These inductions were suppressed by Akt inhibitor LY294002 as well as antioxidant N-acetylcysteine. Consistently, TSC exposure augmented cellular resistance to enzalutamide. In clinical data, cigarette smoking was associated with worse progression-free survival and cancer-specific survival when patients with prostate cancer were treated with ARAT agents but not docetaxel. CONCLUSIONS: It was suggested that cigarette smoking leads to detrimental oncological outcome when prostate cancer patients are treated with ARAT agents through induction of aberrant AR signaling. Accordingly, we recommend that patients with advanced prostate cancer should refrain from cigarette smoking.

The impact of genetic polymorphism on CYP19A1 in androgen-deprivation therapy among Japanese men.

PURPOSE: Inadequate suppression of testosterone during androgen-deprivation therapy impairs its efficacy. This study investigated the significance of genetic polymorphism in CYP19A1, which encodes aromatase that catalyzes androgens into estrogens, among men treated with primary ADT for metastatic prostate cancer. METHODS: This study included 80 Japanese patients with metastatic prostate cancer whose serum testosterone levels during ADT were available. The association of CYP19A1 gene polymorphism (rs1870050) with clinicopathological parameters including serum testosterone levels during ADT as well as progression-free survival and overall survival was examined. RESULTS: Serum testosterone levels during ADT of men carrying homozygous wild-type (AA) in the CYP19A1 gene [median (interquartile range); 11.6 (8.3-20.3) ng/dl] were higher than those in men carrying the heterozygous/homozygous variant (AC/CC) [median (interquartile range); 10.0 (6.4-12.8) ng/dl]. When adjusted by Gleason score, initial PSA, M-stage and serum testosterone level during ADT, heterozygous/homozygous variant (AC/CC) in the CYP19A1 gene was associated with a lower risk of progression to castration resistance [hazard ratio (95% confidence interval), 0.53 [0.29-0.92], p = 0.025], but not to any-cause death [hazard ratio (95% confidence interval), 0.74 [0.36-1.49], p = 0.40]. CONCLUSIONS: These findings suggest that genetic variation in CYP19A1 (rs1870050) might affect the prognosis of patients with metastatic prostate cancer when treated with ADT by regulating serum testosterone levels.

Cholesterol sulfate is a DOCK2 inhibitor that mediates tissue-specific immune evasion in the eye.

Although immune responses are essential to protect the body from infection, they can also harm tissues. Certain tissues and organs, including the eye, constitute specialized microenvironments that locally inhibit immune reactivity. Dedicator of cytokinesis protein 2 (DOCK2) is a Rac-specific guanine nucleotide exchange factor (GEF) that is predominantly found in hematopoietic cells. DOCK2 plays a key role in immune surveillance because it is essential for the activation and migration of leukocytes. DOCK2 mutations cause severe immunodeficiency in humans. We found that DOCK2-mediated Rac activation and leukocyte migration were effectively inhibited by cholesterol sulfate (CS), but not by cholesterol or other sulfated steroids. CS bound to the catalytic domain of DOCK2 and suppressed its GEF activity. Mass spectrometric quantification revealed that CS was most abundantly produced in the Harderian gland, which provides the lipids that form the oily layer of the tear film. Sulfation of cholesterol is mediated by the sulfotransferases SULT2B1b and, to a lesser extent, SULT2B1a, which are produced from the same gene through alternative splicing. By genetically inactivating Sult2b1, we showed that the lack of CS in mice augmented ultraviolet- and antigen-induced ocular surface inflammation, which was suppressed by administration of eye drops containing CS. Thus, CS is a naturally occurring DOCK2 inhibitor and contributes to the generation of the immunosuppressive microenvironment in the eye.

The Rac Activator DOCK2 Mediates Plasma Cell Differentiation and IgG Antibody Production.

A hallmark of humoral immune responses is the production of antibodies. This process involves a complex cascade of molecular and cellular interactions, including recognition of specific antigen by the B cell receptor (BCR), which triggers activation of B cells and differentiation into plasma cells (PCs). Although activation of the small GTPase Rac has been implicated in BCR-mediated antigen recognition, its precise role in humoral immunity and the upstream regulator remain elusive. DOCK2 is a Rac-specific guanine nucleotide exchange factor predominantly expressed in hematopoietic cells. We found that BCR-mediated Rac activation was almost completely lost in DOCK2-deficient B cells, resulting in defects in B cell spreading over the target cell-membrane and sustained growth of BCR microclusters at the interface. When wild-type B cells were stimulated in vitro with anti-IgM F(ab')2 antibody in the presence of IL-4 and IL-5, they differentiated efficiently into PCs. However, BCR-mediated PC differentiation was severely impaired in the case of DOCK2-deficient B cells. Similar results were obtained in vivo when DOCK2-deficient B cells expressing a defined BCR specificity were adoptively transferred into mice and challenged with the cognate antigen. In addition, by generating the conditional knockout mice, we found that DOCK2 expression in B-cell lineage is required to mount antigen-specific IgG antibody. These results highlight important role of the DOCK2-Rac axis in PC differentiation and IgG antibody responses.

Targeting Ras-Driven Cancer Cell Survival and Invasion through Selective Inhibition of DOCK1.

Oncogenic Ras plays a key role in cancer initiation but also contributes to malignant phenotypes by stimulating nutrient uptake and promoting invasive migration. Because these latter cellular responses require Rac-mediated remodeling of the actin cytoskeleton, we hypothesized that molecules involved in Rac activation may be valuable targets for cancer therapy. We report that genetic inactivation of the Rac-specific guanine nucleotide exchange factor DOCK1 ablates both macropinocytosis-dependent nutrient uptake and cellular invasion in Ras-transformed cells. By screening chemical libraries, we have identified 1-(2-(3'-(trifluoromethyl)-[1,1'-biphenyl]-4-yl)-2-oxoethyl)-5-pyrrolidinylsulfonyl-2(1H)-pyridone (TBOPP) as a selective inhibitor of DOCK1. TBOPP dampened DOCK1-mediated invasion, macropinocytosis, and survival under the condition of glutamine deprivation without impairing the biological functions of the closely related DOCK2 and DOCK5 proteins. Furthermore, TBOPP treatment suppressed cancer metastasis and growth in vivo in mice. Our results demonstrate that selective pharmacological inhibition of DOCK1 could be a therapeutic approach to target cancer cell survival and invasion.

The transcription factor EPAS1 links DOCK8 deficiency to atopic skin inflammation via IL-31 induction.

Mutations of DOCK8 in humans cause a combined immunodeficiency characterized by atopic dermatitis with high serum IgE levels. However, the molecular link between DOCK8 deficiency and atopic skin inflammation is unknown. Here we show that CD4+ T cells from DOCK8-deficient mice produce large amounts of IL-31, a major pruritogen associated with atopic dermatitis. IL-31 induction critically depends on the transcription factor EPAS1, and its conditional deletion in CD4+ T cells abrogates skin disease development in DOCK8-deficient mice. Although EPAS1 is known to form a complex with aryl hydrocarbon receptor nuclear translocator (ARNT) and control hypoxic responses, EPAS1-mediated Il31 promoter activation is independent of ARNT, but in collaboration with SP1. On the other hand, we find that DOCK8 is an adaptor and negative regulator of nuclear translocation of EPAS1. Thus, EPAS1 links DOCK8 deficiency to atopic skin inflammation via IL-31 induction in CD4+ T cells.