Epithelial Antigen Research Articles

Six-transmembrane epithelial antigen of the prostate 1 accelerates cell proliferation by targeting c-Myc in liver cancer cells.

Six-transmembrane epithelial antigen of the prostate 1 (STEAP1) has emerged as an ideal target in cancer therapeutics. However, the functions of STEAP1 in liver cancer remain unexplored. The current study aimed to characterize the biological roles of STEAP1 in liver cancer. STEAP1 expression was upregulated in tumor tissues, and high STEAP1 expression was associated with poor clinical outcomes in patients with liver cancer, according to several publicly available datasets. STEAP1 silencing using small interfering RNA inhibited cell proliferation and was accompanied by G1 arrest induced by the suppression of cyclin D1 and the promotion of p27. STEAP1 silencing suppressed c-Myc expression, which was identified as a component in STEAP1 signal transduction by mining publicly available datasets and was then confirmed by PCR array. In conclusion, the knockdown of STEAP1 in liver cancer cell lines led to inhibition of cell proliferation involving G1 arrest by suppressing c-Myc. The present study provides a preclinical concept for STEAP1 as a druggable target in liver cancer.

A study of various diagnostic tests to identify offending allergens in patients of allergic rhinitis in a tertiary care centre in northern India

Background and Objectives: Allergic rhinitis, a global health issue, if left untreated cause serious conditions like asthma, sinusitis or ear infections. Precise identification of allergens is worthwhile since it may lead to improvement in therapy. Therefore, this study was undertaken to determine the common inhalant allergens causing allergy in and around Saharanpur by skin prick test, serum IgE levels, nasal smear eosinphilia and AEC levels. Materials and Methods: 50 patients diagnosed clinically to have allergic rhinitis were included in the study. Absolute eosinophil count, nasal smear for eosinophils, and total IgE levels (wherever possible) were determined. Skin prick tests using 46 common inhalant allergens were done and results analysed. Results: Increased absolute eosinophil count, nasal smear positive for eosinophil and raised total IgE levels were found to be present in 56%, 22% and 97% of the patients respectively. Frequency of positive skin prick test response to various group of allergens were — Pollen (80%), Dust (70%), Mite (52%), Insects (50%), Fungi (48%) and Epithelial antigens (20%). Overall, pollen of Parthenium (in 70%) followed by House dust (in 64%) were found to be the most common offending allergens. Conclusion: It can be concluded that skin prick test along with serum IgE levels used to identify the causative allergens is useful in the patients of allergic rhinitis. Keywords: Allergic rhinitis, Skin prick test, Aeroallergens, Nasal smear eosinophils, IgE.

Epithelial antigen presentation regulates CD4+ TRM cell locations, functions and activities

Abstract Barrier tissues are sentinelled by CD4+ TRM cells with potent anti-microbial activities and considerable lineage plasticity. We hypothesized that local antigen presentation by lung epithelial cells (LECs) instruct CD4+ TRM cell activities. Pneumococcal infections in transgenic mice, flow- and spectral-cytometry, computational biology, and immunofluorescence were used to study this biology. All LECs including a novel alveolar surfactant protein C (SPC)low LEC were adept at antigen presentation. Temporal analysis of LECs for MHC-II and costimulatory/coinhibitory molecules revealed that airway club cells were T-cell stimulatory via CD40 while alveolar LECs expressed T-cell inhibitory PD-L1. This anatomical segregation of LEC antigen presentation correlated with deposition of CD4+ TRM cells around airways such that ablation of LEC MHC-II disrupted CD4+ TRM niches and blockade of CD40 signals prevented accumulation of CD4+ TRM cells. Recurrent memory recalls in absence of LEC MHC-II led to expansion of unconventional CD4+ TRM cells co-expressing classically incompatible lineage-defining transcription factors, changing their cytokine repertoire and leading to dysregulated immunity that phenocopied clinical features of checkpoint blockade therapy. Consequently, a tight correlation between MHC-II and PD-L1 was confirmed in mouse and human LECs. We discovered that LEC MHC-II functions in post-translational trafficking lockstep with PD-L1 to exert its restraints on TRM cell activities. Our results identify epithelial antigen presentation as critical instructors of CD4+ TRM cell locations, phenotypes and activities and establish epithelial-CD4+ TRM cell immunological synapses as key components of barrier immunity.

Recent insights into the role of the microbiome in malignant and benign hematologic diseases.

Growing evidence suggests the impact of microbiome alteration, named dysbiosis, on the development of neoplasms, infections, inflammatory diseases, and immuno-mediated disorders. Regarding hematologic diseases, most data regard hematopoietic stem cell transplant (HSCT). In this review, we systematically evaluate the studies concerning microbiome in malignant and benign hematologic disorders beyond HSCT. A permissive microbiota is associated to the development of hematologic malignancies (including acute leukemia, lymphoma, and multiple myeloma), as well as of iron deficiency anemia, autoimmune cytopenias, and aplastic anemia. This happens through various mechanisms; chronic inflammatory triggering, epithelial barrier alteration, antigen dissequestration, and molecular mimicry. Hematologic therapies (chemo and immunosuppression) may induce/worsen dysbiosis and favour disease progression and infectious complications. Antibiotics may also induce dysbiosis with possible long-term consequences. Finally, novel target therapies are likely to alter microbiome, inducing gut inflammation (i.e. small molecules such as tyrosine-kinase-inhibitors) or enhancing host's immune system (as observed with CAR-T cells and checkpoint inhibitors).

Phase I study of AMG 509, a STEAP1 x CD3 T-cell recruiting XmAb 2+1 immune therapy, in patients with metastatic castration-resistant prostate cancer (mCRPC).

TPS183 Background: Six transmembrane epithelial antigen of the prostate 1 (STEAP1) is a cell surface antigen that is highly expressed in prostate cancer. AMG 509 is a potent bispecific XmAb 2+1 immune therapy designed to direct T effector cells to STEAP1-expressing cells. AMG 509 contains two identical humanized anti-STEAP1 Fab domains that bind STEAP1-expressing cells, an anti-CD3 scFv domain that binds T cells, and an Fc domain, engineered to lack effector function, that extends serum half-life. In preclinical studies, AMG 509 induced potent and specific T-cell-mediated lysis of STEAP1-expressing cancer models. Methods: This open-label, phase 1, first-in-human study will evaluate the safety, tolerability, pharmacokinetics (PK), and efficacy of AMG 509 in patients with relapsed/refractory mCRPC. The dose exploration phase (n=40) will estimate the maximum tolerated dose (MTD) or recommended phase 2 dose (RP2D) using a Bayesian logistic regression model. The dose expansion phase (n=30) will confirm safety, PK, and pharmacodynamics at the MTD or RP2D and collect further safety, efficacy, and biomarker data. Efficacy will be assessed by prostate-specific antigen response, circulating tumor cell response, and objective tumor response per RECIST 1.1 with Prostate Cancer Working Group 3 modifications. Key inclusion criteria: men ≥18 years with histologically/cytologically confirmed mCRPC who are refractory to novel hormonal therapy (e.g., abiraterone and/or enzalutamide) and have failed 1–2 taxane regimens or are medically unsuitable for or have refused taxanes; ongoing castration with total serum testosterone ≤50 ng/dL; evidence of progressive disease; ECOG performance status 0–1; life expectancy ≥3 months; and adequate hematologic, renal, hepatic, and cardiac function. In the dose exploration phase, novel antiandrogen therapy must have been given in the metastatic setting. Key exclusion criteria: pure small cell or neuroendocrine carcinoma of the prostate; untreated CNS metastases or leptomeningeal disease; any anticancer therapy or immunotherapy, radiation therapy, or major surgery <4 weeks from first dose; history of or current autoimmune disease or any disease requiring immunosuppressive therapy (≤10 mg/d prednisone permitted); prior STEAP1-targeted therapy; infection requiring IV antimicrobials <7 days from first dose. The study opened in January 2020 and is recruiting patients. ClinicalTrials.gov: NCT04221542. 2020 American Society of Clinical Oncology, Inc. Reused with permission. This abstract was accepted and previously presented at the 2020 ASCO Annual Meeting. All rights reserved. Clinical trial information: NCT04221542.

MicroRNA-301a-3p promotes diabetic retinopathy via regulation of six-transmembrane epithelial antigen of prostate 4.

Diabetic retinopathy (DR) is one of the most serious microvascular complications of diabetes mellitus (DM). MicroRNAs (miRNAs) have been discovered to play a crucial role in DR, but the mechanisms underlying the effects of miR-301a-3p on DR are poorly understood. This paper was designed to explore the possible role of miR-301a-3p in DR. The diabetic rat model was established by a single intraperitoneal injection of streptozotocin (STZ). The effects of miR-301a-3p on the biological functions of HRECs were determined through a series of experiments in vitro/vivo. The results revealed that interference with miR-301a-3p could decrease the expressions of inflammatory factors and apoptosis in the retinal tissue of DR. Furthermore, it can alleviate the oxidative stress in DR serum, reduce VEGF expression, increase endothelial cell marker expression, and inhibit (High Glucose) HG-induced apoptosis of HRECs. Six-transmembrane epithelial antigen of prostate 4 (STEAP4) was the target of miR-301a-3p. All the effects of miR-301a-3p in DR model were reversed by STEAP4 inhibitor. miR-301a-3p promotes diabetic retinopathy via regulation of STEAP4. The findings in this study may provide a vital reference for the drug research and development in DR treatment.

Clinical significance of STEAP1 extracellular vesicles in prostate cancer

BackgroundExtracellular vesicles (EVs) are cell-derived lipid bilayer enclosed structures shed from the plasma membrane by all cell types. Evidence of EV presence in biological fluids has led to considerable efforts focused on identifying their cargo and determining their utility as a non-invasive diagnostic platform for cancer. In this study, we identify circulating STEAP1 (six-transmembrane epithelial antigen of the prostate 1)-positive EVs in the plasma of healthy males and prostate cancer patients and evaluate its diagnostic and prognostic significance.MethodsSTEAP1 was identified on EVs in prostate cancer patient plasma. EVs were validated using electron microscopy, Western blot, nanoparticle tracking analysis, and nanoscale flow cytometry. STEAP1-positive EVs were quantified for 121 males with prostate cancer and 55 healthy age-matched control males. An evaluation of STEAP1 in prostate cancer tissue was also performed using established prostate cancer cohort data (TCGA, MSKCC, and SU2C/PCF Dream Team).ResultsEvaluation of STEAP1-positive EVs by nanoscale flow cytometry identified a significant increase in prostate cancer patient plasma compared to healthy males. However, no association was found between total STEAP1 EV levels and disease recurrence or overall survival. Cohort data from prostate cancer tissue also found STEAP1 to be elevated in prostate cancer while no significant association with recurrence or overall survival was identified.ConclusionsSTEAP1 is known to be enriched on the cells of the prostate with potential clinical significance in prostate cancer. Our results identify and quantitate STEAP1-positive EVs in plasma and provide rationale for a STEAP1 EV-based liquid biopsy as a diagnostic strategy in prostate cancer.

MAb Das-1 identifies pancreatic ductal adenocarcinoma and high-grade pancreatic intraepithelial neoplasia with high accuracy

Pancreatic intraepithelial neoplasia (PanIN) is a microscopic precursor lesion to pancreatic ductal adenocarcinoma (PDAC); however, there are few biomarkers that segregate high-grade PanIN/PDAC from low-grade PanIN lesions. mAb Das-1 is a monoclonal antibody against a colonic epithelial antigen that is reactive to premalignant conditions of the upper gastrointestinal tract including Barrett's esophagus, incomplete-type gastric intestinal metaplasia, and intraductal papillary mucinous neoplasm of the pancreas at high risk of malignancy. We sought to examine a role for Das-1 expression in differentiating high-grade PanIN/PDAC from low-grade PanIN lesions. We examined surgical specimens from 86 patients and 2 autopsied pancreata (74 with and 14 without PDAC) with 107 distinct PanIN lesions, 74 PDAC cases, and 32 associated lymph node metastases, with internal controls of normal pancreatic ducts observed in 56 cases. All of the normal pancreatic duct controls (0/56) and low-grade PanIN (0/95) lesions were nonreactive to Das-1. Das-1 expression amonghigh-grade PanIN (7/12, 58%), PDAC (55/74, 74%), and lymph node metastasis (21/32, 66%) cases was significantly higher (p<0.0001). Clinicopathologically, Das-1 reactivity was significantly correlated with nodal metastasis (p=0.021). Overall, the sensitivity, specificity, and accuracy of Das-1 in segregating high-grade PanIN/PDAC from low-grade PanIN lesions and normal ducts were 72%, 100%, and 90%, respectively. Thus, mAb Das-1 reacts with high specificity with high-grade PanIN and PDAC and may help in preoperative diagnosis and/or clinical risk stratification.

Inflammation accelerates copper-mediated cytotoxicity through induction of six-transmembrane epithelial antigens of prostate 4 expression.

Copper is an essential trace metal, but imbalance in copper homeostasis can induce oxidative damage. Inflammation is a fundamental element of various pulmonary diseases. Although a positive relationship between copper and chronic pulmonary diseases has been reported, the underlying reasons are still not clear. The copper level in the sputum of patients with various pulmonary diseases was measured. An inflammatory model was established to evaluate the impact of inflammation on copper uptake in the lung. We found that the level of sputum copper was increased in patients with various pulmonary diseases, especially chronic obstructive pulmonary disease and asthma. Then, we confirmed that mice with pulmonary inflammation were susceptible to copper-mediated oxidative damage because of copper overload in lung tissue. Further investigation demonstrated that interleukin (IL)-17 and tumor necrosis factor (TNF)-α exerted synergistic effects in airway epithelial cells by upregulating the expression of six-transmembrane epithelial antigens of prostate 4 (STEAP4), a metalloreductase that reduces extracellular copper ions from the cupric state to the cuprous state and facilitates copper uptake. Inhibition of STEAP4 decreased the copper uptake of cells and inhibited copper-mediated oxidative damage. Moreover, we demonstrated that the upregulation of STEAP4 by IL-17 and TNF-α was largely dependent on TNF receptor-associated factor 4 (TRAF4). Traf4-/- mice were resistant to copper-mediated oxidative damage. Our data suggest a novel IL-17/TNF-α-TRAF4-STEAP4 axis that regulates copper homeostasis.

SIRT1 alleviates hepatic ischemia-reperfusion injury via the miR-182-mediated XBP1/NLRP3 pathway

The hepatoprotection of histone deacetylase sirtuin 1 (SIRT1) has been identified to attenuate ischemia-reperfusion (IR)-triggered inflammation and liver damage. This study was performed to characterize the function of SIRT1 in hepatic IR injury. In in vivo assays on liver-specific knockout mice of SIRT1, we first validated the effect of SIRT1 knockout on liver damage and XBP1/NLRP3 inflammasome activation. Next, we examined whether knockdown of XBP1/NLRP3 or miR-182 agomir could reverse the effect of SIRT1 knockout. In in vitro assays, NCTC1469 cells subjected to hypoxia/reoxygenation (H/R) were transduced with small interfering RNA (siRNA)/activator of SIRT1 or miR-182 agomir to confirm the effect of SIRT1 on NCTC1469 cell behaviors as well as the regulation of miR-182 and the XBP1/NLRP3 signaling pathway. Hepatic IR injury was appreciably aggravated in SIRT1 knockout mice, and SIRT1 knockdown abolished the inhibition of XBP1/NLRP3 inflammasome activation, which was reversed by NLRP3 knockdown, XBP1 knockdown, or miR-182 agomir. Mechanistically, miR-182 expression was positively regulated by SIRT1 in hepatic IR injury in mice, and miR-182 inhibited the expression of XBP1 by binding to the 3′ untranslated region (UTR) of XBP1. The histone deacetylase SIRT1 inhibits the downstream XBP1/NLRP3 inflammatory pathway by activating miR-182, thus alleviating hepatic IR injury in mice.

A research of STEAP1 regulated gastric cancer cell proliferation, migration and invasion in vitro and in vivos.

Six‐Transmembrane Epithelial Antigene of the Prostate 1 (STEAP1) is associated with the occurrence and development of cancer. This study aimed to clarify the role of STEAP1 in gastric cancer tumour growth and metastasis, as well as its molecular mechanism of action.Statistical methods were used for clinical data analysis. Protein expression was detected using immunohistochemistry(IHC). The mRNA and protein expression in the cell cultures were detected using reverse transcription‐polymerase chain reaction(RT‐PCR) and western blot analysis. Overexpression and silencing models were constructed using plasmid and lentivirus transfection. To detect cell proliferation in vitro, Cell Counting Kit‐8(CCK‐8), flow cytometry and colony formation assays were used; transwell and wound healing assays were used to detect cell migration and invasion;For in vivo experiments, nude BALB/c mice were used for detecting subcutaneous tumorigenesis and intraperitoneal implantation. In the results,we found STEAP1 was overexpressed in gastric cancer tissues and cell lines. Single‐factor and Cox analyses showed that STEAP1 gene expression level correlated with poor prognosis. Up‐regulation of STEAP1 increased cell proliferation, migration and invasion, which decreased after STEAP1 was knocked down. These changes were achieved via the activation of the AKT/FoxO1 pathway and epithelial‐mesenchymal transformation (EMT). The in vivo animal experiments showed that STEAP1 knock down, resulted in a decrease in the subcutaneous tumour and peritoneal tumour formation.

S1930 Lisinopril-Induced Oroesophageal Pemphigus Vulgaris: A Previously Unreported Side Effect

INTRODUCTION: Pemphigoid diseases (PD) are a group of blistering autoimmune pathologies including pemphigus vulgaris (PV) and pemphigus foliaceous (PF), which affect mucocutaneous tissues. NSAIDs, penicillamine, and angiotensin-converting enzyme inhibitors (ACEI) such as captopril and enalapril are associated with drug-induced pemphigoid (DIP). We present a case of lisinopril-associated PV which has not been previously reported. CASE DESCRIPTION/METHODS: A 35-year-old male with essential hypertension presented with multiple oral ulcers associated with dysphagia, odynophagia, and a 20-lb weight loss in six weeks since starting lisinopril. Multiple white-colored lesions were noted along the buccal mucosa (Figure 1) and posterior pharynx. Tests for ANA, HIV, and a chronic hepatitis panel were negative. Fluconazole, Nystatin, and Valganciclovir were initiated without improvement. As such, he subsequently underwent an intralesional incisional biopsy of the buccal mucosa which revealed changes compatible with PV (Figure 2). On EGD, two blood-filled blisters in the mid-esophagus were noted (Figure 3). Considering a pre-established diagnosis of PV, they were not biopsied. Lisinopril was discontinued and the patient was started on prednisone and mycophenolate with a subsequent resolution of symptoms. DISCUSSION: PD are characterized by IgG antibodies directed against epithelial antigens, desmoglein 1 and 3, leading to separation of keratinocytes (acantholysis) and formation of intraepidermal bullae. ACEI such as captopril, enalapril, and cilazapril have been associated with DIP. One case report of lisinopril induced PF has been reported. However, mucinous nor cutaneous PV secondary to its use has not been previously detailed. The etiology of lisinopril-induced DIP is not fully understood. All ACEI contain an amide-group which is noted to modify keratinocyte proteins to make neoantigens and can stimulate acantholysis. Patients on ACEI are also noted to have circulating autoantibodies against keratinocyte surface antigens which can be contributory. Cessation of ACEI is essential to halt progression while immunotherapy with steroids and other immunomodulators such as rituximab, azathioprine, or mycophenolate are the mainstay of management. A thorough drug reconciliation should be performed on presentation to allow for possibly early discontinuation of the offending agent(s), limit duration, and decrease side-effects of subsequent immunomodulatory therapy.Figure 1.: Well circumscribed, whitish ulceration of the buccal mucosa with adjacent erythema and swelling.Figure 2.: Hematoxylin-eosin (HE) stain of the buccal mucosa showing mucosal epithelium exhibiting a suprabasal split and associated acanthloysis with an underlying relatively brisk perivascular and interstitial lymphoplasmacytic infiltrate; with 40X (A) and 100X (B) magnification.Figure 3.: Two blood-filled blisters of the mucosa in the mid-esophagus, each measuring 6-7 mm in length.

Comprehensive landscape of STEAP family functions and prognostic prediction value in glioblastoma.

Glioblastoma (GBM) is the most common, malignant, and deadly primary glioma. Six-transmembrane epithelial antigen of prostate (STEAP) family isinvolvedin tumorigenesis;here, we haveexploredthe biological function and the prognostic value of the STEAP family in GBM. Differentially expressed STEAP genes in tumor and normal samples were screened by usingThe Cancer Genome Atlas (TCGA) database. Univariate and multivariate Cox regression identified the prognosis-related genes: STEAP2 and STEAP3, which were involved in the regulation of immune response and cell cycle. Finally, a prognostic nomogram combining age, gender, chemotherapy, radiotherapy, IDH1 status, and the risk score model based on STEAP2 and STEAP3 was built and further validated in TCGA and Chinese Glioma Genome Atlas (CGGA) cohorts via concordance index and calibration plot, which suggested a favorable value for prognosis prediction. In conclusion, our results provided a comprehensive analysis of the STEAP family and a model for the prognosis prediction of GBM.

ADENOID CYSTIC CARCINOMA ON THE BASIS OF TONGUE: A RARE CASE REPORT

A 55-year-old male patient attended a dermatology center because of dysarthria and dysphagia. The clinical examination showed swelling in the base of the tongue extending bilaterally to the borders preserving the median longitudinal groove. The patient underwent punch biopsy, and the specimen was referred for anatomopathologic examination with clinical suspicion of hypertrophy of tongue. Histopathologic examination revealed malignant neoplasm of glandular origin composed of cells with scarce eosinophilic cytoplasm and large hyperchromatic nuclei, organized in nests and cords sometimes with cribriform pattern and luminal formation filled with homogeneous eosinophilic material. The morphologic characteristics suggested a diagnosis of adenoid cystic carcinoma (ACC) or metastatic tumor. The immunohistochemical study demonstrated that epithelial/ductal cells were positive for cytokeratins and basal cells for p63 protein revealing their myoepithelial origin, with membrane epithelial antigen being focally positive, which led to the diagnosis of ACC. The patient was referred to an oncologic reference center.

STEAP3 (Six-Transmembrane Epithelial Antigen of Prostate 3) Inhibits Pathological Cardiac Hypertrophy.

Pathological cardiac hypertrophy is one of the major predictors and inducers of heart failure, the end stage of various cardiovascular diseases. However, the molecular mechanisms underlying pathogenesis of pathological cardiac hypertrophy remain largely unknown. Here, we provided the first evidence that STEAP3 (Six-Transmembrane Epithelial Antigen of Prostate 3) is a key negative regulator of this disease. We found that the expression of STEAP3 was reduced in pressure overload-induced hypertrophic hearts and phenylephrine-induced hypertrophic cardiomyocytes. In a transverse aortic constriction-triggered mouse cardiac hypertrophy model, STEAP3 deficiency remarkably deteriorated cardiac hypertrophy and fibrosis, whereas the opposite phenotype was observed in the cardiomyocyte-specific STEAP3 overexpressing mice. Accordingly, STEAP3 significantly mitigated phenylephrine-induced cell enlargement in primary neonatal rat cardiomyocytes. Mechanistically, via RNA-seq and immunoprecipitation-mass screening, we demonstrated that STEAP3 directly bond to Rho family small GTPase 1 and suppressed the activation of downstream mitogen-activated protein kinase-extracellular signal-regulated kinase signaling cascade. Remarkably, the antihypertrophic effect of STEAP3 was largely blocked by overexpression of constitutively active mutant Rac1 (G12V). Our study indicates that STEAP3 serves as a novel negative regulator of pathological cardiac hypertrophy by blocking the activation of the Rac1-dependent signaling cascade and may contribute to exploring effective therapeutic strategies of pathological cardiac hypertrophy treatment.

Abstract CT166: TRX-E-002-1 in treatment-refractory ovarian cancer - 3-month follow-up results from a phase I study dose escalation phase

Abstract Introduction: The poor outcomes associated with current therapies for recurrent epithelial ovarian cancer (EOC) are thought to reflect the existence of drug-resistant ovarian cancer stem cells (OCSCs). The introduction of emerging therapies such as anti-angiogenic monoclonal antibodies and PARP inhibitors have added to the treatment armamentarium but have generated new resistance mechanisms to contend with. TRX-E-002-1 is a novel, 3rd generation benzopyran molecule that induces caspase-dependent and -independent apoptosis in CD44 +ve ovarian cancer stem-like cells and CD44 -ve ovarian somatic cancer cells. The dose escalation phase of a progressive design trial investigating intraperitoneal (IP)-administered TRX-E-002-1 monotherapy and in combination with standard of care for recurrent EOC (NCT02903771) has been completed with a Maximum Tolerated Dose (MTD) of 5 mg/kg established. Methods: Women with platinum-resistant relapsed disease, platinum refractory disease, or documented intolerance to platinum therapy were enrolled into the study. Patients had completed at least 2 or more prior regimens (including adjuvant therapy) prior to enrolment. Patients were dosed weekly with single agent TRX-E-002-1 IP for the first 2 cycles after which addition of pre-defined standard intravenous chemotherapy regimens was allowed cycles 3-8. Patients were followed up for 3 months after the end of treatment. Assessments included disease response, based on CA-125 and Response Evaluation Criteria in Solid Tumours or GCIG criteria along with circulating epithelial tumour cells (CETC) and stem cell markers. Results: For the 11 evaluable patients, on average, 4 prior lines of therapy, across a range of current and emerging treatments were completed. A total of 9 subjects were evaluable for MTD analysis with 5 patients showing stable disease on monotherapy per RECIST 1.1 criteria and 4 completing 8 cycles (6 months) of treatment; 2 remained progression-free at the 3-month endpoint post-treatment. Preliminary data on activity includes 2 partial responses (PR) per RECIST 1.1 criteria observed at follow-up. With no measurable disease per RECIST 1.1 criteria, 1 patient demonstrated a complete response (CR) during combination treatment which was maintained through-out follow-up, as per GCIG criteria in patients without initial measurable disease. Median progression free survival shown to be 5.5 months. CETC data for responders shows growth of circulating cancer stem cells no longer detected during cultivation of epithelial-antigen +ve cells indicating that the epithelial antigen cells present are not capable of clonal expansion. Conclusion: IP administered TRX-E-002-1 as a first-in-class, dual acting, anti-cancer therapy has preliminary activity for the treatment of platinum resistant ovarian cancer for patients who have demonstrated resistance to a range of prior treatments. Citation Format: Jermaine Coward, Ganessan Kichenadasse, Paul Harnett, Kathleen Moore, Minal Barve, Daniel Berg, James Garner, Don Dizon. TRX-E-002-1 in treatment-refractory ovarian cancer - 3-month follow-up results from a phase I study dose escalation phase [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr CT166.

Abstract DDT02-03: AMG 509: A novel, humanized, half-Life extended, bispecific STEAP1 × CD3 T cell recruiting XmAb® 2+1 antibody

Abstract AMG509, a novel STEAP1 x CD3 T cell-recruiting XmAb® 2+1 bispecific immune therapy for the treatment of prostate cancer and Ewing sarcoma. Metastatic castration resistant prostate cancer (mCRPC) and Ewing sarcoma (EWS) are both diseases with unmet medical needs. Six Transmembrane Epithelial Antigen of the Prostate 1 (STEAP1) is a cell surface antigen that is induced by androgens and highly expressed in prostate cancer. STEAP1 is also highly expressed in EWS, and it is a target of the EWS/FLI1 fusion, the primary oncogenic driver in this pediatric malignancy. AMG 509 is a novel, half-life extended, cynomolgus monkey cross-reactive, STEAP1 x CD3 T cell-recruiting XmAb® 2+1 bispecific antibody designed to treat STEAP1-expressing cancers. AMG 509 contains two identical humanized anti-STEAP1 Fab domains that bind STEAP1-expressing cells, an anti-CD3 scFv domain that binds T cells, and an Fc domain engineered to lack effector function and extend serum half-life. We found that membranous STEAP1 expression, as measured by IHC, was absent from most normal tissues (FDA normal organ tissue array, n = 72) except the prostate epithelium and a subset of lung macrophages. In contrast, we found membranous STEAP1 expression by IHC in 80% of primary prostate cancer tumors (n = 80) and moderate to high expression in 83% of metastatic prostate cancer lesions (n = 181) and 77% of bone metastases (n = 31). In addition, we found STEAP1 expression by IHC in all EWS cell lines (n=13) and xenograft models tested (n=12). AMG 509 bound to recombinant human and cynomolgus monkey CD3ϵ with a KD of 27.6 nM and 25.8 nM, respectively, and to 293T cells transfected with human or cynomolgus monkey STEAP1 with an EC50 of 3.8 nM and 3.1 nM, respectively. AMG 509 triggered potent T cell-redirected lysis of STEAP1-positive cancer cells, with a median EC50 of 18.9 pM across 17 different STEAP1-expressing prostate, EWS, gastric, and melanoma cancer cell lines. AMG 509 was 50-fold more potent in inducing the redirected lysis of C4-2B prostate cancer cells in vitro than an XmAb® molecule with a single anti-STEAP1 Fab domain. AMG 509 was also specific, as it showed no activity against C4-2B cancer cells engineered to lack STEAP1 expression. AMG 509 exhibited hallmarks of T-cell engagement in vitro, including T-cell proliferation and cytokine release. It also induced robust in vivo anti-tumor activity in prostate cancer and EWS xenograft models, with concomitant CD8+ T-cell activation and expansion in tumors. Data from a nonclinical safety study conducted in the cynomolgus monkey suggest that AMG 509 can be administered safely at doses that are predicted to be clinically active. AMG 509 is a potent and specific first-in-class T cell-recruiting antibody for the treatment of STEAP1-positive malignancies. We are currently evaluating the safety, tolerability, pharmacokinetics, and efficacy of AMG 509 in a phase 1, first-in-human study in patients with mCRPC (NCT04221542). Citation Format: Olivier Nolan-Stevaux. AMG 509: A novel, humanized, half-Life extended, bispecific STEAP1 × CD3 T cell recruiting XmAb® 2+1 antibody [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr DDT02-03.

Abstract 3750: STEAP2 is upregulated and necessary for hepatocellular carcinoma progression via increased copper levels and stress-activated MAP kinase activity

Abstract To understand potential molecular mechanisms that drive hepatocellular carcinoma (HCC) progression, we performed RNA sequencing from paired adjacent non-tumor liver and HCC tumor tissues of nine local HCC patients which revealed significant involvement of a gene coding for Six Transmembrane Epithelial Antigen of Prostate 2 (STEAP2) protein. STEAP2 is a metalloreductase involved in the reduction and indirectly, uptake, of iron and copper ions. We found significantly higher levels of total copper in HCC tissues than those in paired adjacent non-tumor tissues. The upregulation of STEAP2 expression in HCC was confirmed at its protein level and in TCGA and other published HCC gene expression datasets. Hepatic copper overload is associated with Wilson's disease and a known risk factor for HCC, therefore, we hypothesize that STEAP2 upregulation and copper accumulation contribute to HCC progression. Paired HCC and adjacent non-tumor tissues were collected for RNA sequencing, metal ion measurement, and measurements of STEAP2 levels with RT-qPCR and Western blot. Public HCC datasets were queried for STEAP2 expression in HCC and non-tumor tissues. HCC cell lines with knockdown (KD) and overexpression (OE) of STEAP2 were created to perform mechanistic studies including measurements of copper levels and MAP kinase activities, cell proliferation, migration, and anchorage independent growth in vitro and tumor growth in vivo. STEAP2 is significantly upregulated in various HCC gene expression datasets; its expression is positively associated with tumor grade. STEAP2 KD in HCC cell lines decreased cell growth, migration, invasion, and xenograft tumor growth, while STEAP2 OE showed opposite effects. STEAP2 KD in HCC cells also reduced intracellular copper levels and activation of stress-activated MAP kinases including p38 and JNK. Treatment with copper rescued the reduced HCC cell migration due to STEATP2 KD and activated p38 and JNK. Furthermore, treatment with p38 or JNK inhibitors significantly inhibited cell migration. Thus, STEAP2 appears to play a malignant-promoting role in HCC cells by driving migration/invasion via increased copper levels and MAP kinase activities. Our study uncovered a novel molecular mechanism contributing to HCC malignancy and a potential therapeutic target for HCC treatment. Citation Format: Carla R. Zeballos, Acarizia Easley, Hakim Bouamar, Guixi Zheng, Xiang Gu, Yang Junhua, Yidong Chen, Francisco Cigarroa, LuZhe Sun. STEAP2 is upregulated and necessary for hepatocellular carcinoma progression via increased copper levels and stress-activated MAP kinase activity [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3750.

Coeliac Disease Pathogenesis: The Uncertainties of a Well-Known Immune Mediated Disorder.

Coeliac disease is a common small bowel enteropathy arising in genetically predisposed individuals and caused by ingestion of gluten in the diet. Great advances have been made in understanding the role of the adaptive immune system in response to gluten peptides. Despite detailed knowledge of these adaptive immune mechanisms, the complete series of pathogenic events responsible for development of the tissue lesion remains less certain. This review contributes to the field by discussing additional mechanisms which may also contribute to pathogenesis. These include the production of cytokines such as interleukin-15 by intestinal epithelial cells and local antigen presenting cells as a pivotal event in the disease process. A subset of unconventional T cells called gamma/delta T cells are also persistently expanded in the coeliac disease (CD) small intestinal epithelium and recent analysis has shown that these cells contribute to pathogenic inflammation. Other unconventional T cell subsets may play a local immunoregulatory role and require further study. It has also been suggested that, in addition to activation of pathogenic T helper cells by gluten peptides, other peptides may directly interact with the intestinal mucosa, further contributing to the disease process. We also discuss how myofibroblasts, a major source of tissue transglutaminase and metalloproteases, may play a key role in intestinal tissue remodeling. Contribution of each of these factors to pathogenesis is discussed to enhance our view of this complex disorder and to contribute to a wider understanding of chronic immune-mediated disease.

Cryo-electron microscopy structure and potential enzymatic function of human six-transmembrane epithelial antigen of the prostate 1 (STEAP1)

Six-transmembrane epithelial antigen of the prostate 1 (STEAP1) is an integral membrane protein that is highly up-regulated on the cell surface of several human cancers, making it a promising therapeutic target to manage these diseases. It shares sequence homology with three enzymes (STEAP2–STEAP4) that catalyze the NADPH-dependent reduction of iron(III). However, STEAP1 lacks an intracellular NADPH-binding domain and does not exhibit cellular ferric reductase activity. Thus, both the molecular function of STEAP1 and its role in cancer progression remain elusive. Here, we present a ∼3.0-Å cryo-EM structure of trimeric human STEAP1 bound to three antigen-binding fragments (Fabs) of the clinically used antibody mAb120.545. The structure revealed that STEAP1 adopts a reductase-like conformation and interacts with the Fabs through its extracellular helices. Enzymatic assays in human cells revealed that STEAP1 promotes iron(III) reduction when fused to the intracellular NADPH-binding domain of its family member STEAP4, suggesting that STEAP1 functions as a ferric reductase in STEAP heterotrimers. Our work provides a foundation for deciphering the molecular mechanisms of STEAP1 and may be useful in the design of new therapeutic strategies to target STEAP1 in cancer.