Efficient CAR T cell targeting of the CA125 extracellular repeat domain of MUC16.

BACKGROUND: Ovarian cancer (OC) is the leading cause of death from gynecologic malignancies in the Western world. Contributing factors include a high frequency of late-stage diagnosis, the development of chemoresistance, and the evasion of host immune responses. Currently, debulking surgery and platinum-based chemotherapy are the treatment cornerstones, although recurrence is common. As the clinical efficacy of immune checkpoint blockade is low, new immunotherapeutic strategies are needed. Chimeric antigen receptor (CAR) T cell therapy empowers patients' own T cells to fight and eradicate cancer, and has been tested against various targets in OC. A promising candidate is the MUC16 ectodomain. This ectodomain remains on the cell surface after cleavage of cancer antigen 125 (CA125), the domain distal from the membrane, which is currently used as a serum biomarker for OC. CA125 itself has not been tested as a possible CAR target. In this study, we examined the suitability of the CA125 as a target for CAR T cell therapy. METHODS: We tested a series of antibodies raised against the CA125 extracellular repeat domain of MUC16 and adapted them to the CAR format. Comparisons between these candidates, and against an existing CAR targeting the MUC16 ectodomain, identified K101 as having high potency and specificity. The K101CAR was subjected to further biochemical and functional tests, including examination of the effect of soluble CA125 on its activity. Finally, we used cell lines and advanced orthotopic patient-derived xenograft (PDX) models to validate, in vivo, the efficiency of our K101CAR construct. RESULTS: We observed a high efficacy of K101CAR T cells against cell lines and patient-derived tumors, in vitro and in vivo. We also demonstrated that K101CAR functionality was not impaired by the soluble antigen. Finally, in direct comparisons, K101CAR, which targets the CA125 extracellular repeat domains, was shown to have similar efficacy to the previously validated 4H11CAR, which targets the MUC16 ectodomain. CONCLUSIONS: Our in vitro and in vivo results, including PDX studies, demonstrate that the CA125 domain of MUC16 represents an excellent target for treating MUC16-positive malignancies.

Structural basis for antibody recognition of the proximal MUC16 ectodomain.

BACKGROUND: Mucin 16 (MUC16) overexpression is linked with cancer progression, metastasis, and therapy resistance in high grade serous ovarian cancer and other malignancies. The cleavage of MUC16 forms independent bimodular fragments, the shed tandem repeat sequence which circulates as a protein bearing the ovarian cancer biomarker (CA125) and a proximal membrane-bound component which is critical in MUC16 oncogenic behavior. A humanized, high affinity antibody targeting the proximal ectodomain represents a potential therapeutic agent against MUC16 with lower antigenic potential and restricted human tissue expression. RESULTS: Here, we demonstrate the potential therapeutic versatility of the humanized antibody as a monoclonal antibody, antibody drug conjugate, and chimeric antigen receptor. We report the crystal structures of 4H11-scFv, derived from an antibody specifically targeting the MUC16 C-terminal region, alone and in complex with a 26-amino acid MUC16 segment resolved at 2.36 Å and 2.47 Å resolution, respectively. The scFv forms a robust interaction with an epitope consisting of two consecutive ß-turns and a ß-hairpin stabilized by 2 hydrogen bonds. The VH-VL interface within the 4H11-scFv is stabilized through an intricate network of 11 hydrogen bonds and a cation-π interaction. CONCLUSIONS: Together, our studies offer insight into antibody-MUC16 ectodomain interaction and advance our ability to design agents with potentially improved therapeutic properties over anti-CA125 moiety antibodies.

Regional Conjunctival Differences in Glycocalyx Mucin Expression in Dry Eye and Normal Subjects.

Purpose: To compare regional conjunctival expression of membrane-associated mucins (MAMs) MUC1, MUC4, and MUC16 in normal and dry eye (DE) subjects. Methods: Adults with and without signs and symptoms of DE were recruited. Impression cytology was performed to collect MAMs from four bulbar and upper eyelid palpebral conjunctival regions of both eyes. After protein extraction, samples from both eyes of a single subject were pooled by region, and expression was analyzed using a capillary electrophoresis nano-immunoassay system. The chemiluminescence intensity of each antigen binding signal was calculated after normalization to the total protein amount. Statistical analyses were conducted using GraphPad Prime 9. Results: Samples from thirteen to sixteen DE and seven to eleven normal subjects were analyzed. In normal samples, MUC1 expression from the nasal bulbar conjunctiva was significantly greater than superior (P = 0.004) and inferior (P = 0.005). In DE samples, MUC1 expression was highest superiorly. Significant differences in MUC4 and MUC16 expression were not seen in normal samples. MUC4 and MUC16 expression was upregulated superiorly (P < 0.0001) and inferiorly (P < 0.0001) in DE compared with those regions in normal samples. Conclusions: Although MAMs form a hydrophilic barrier called the glycocalyx, each mucin may have unique functions that are currently unexplored. All MAMs were expressed in the upper palpebral conjunctiva. Increased MUC1 expression nasally in healthy subjects suggests a functional need for increased protection. When comparing DE with normal eyes, upregulation of MUC1 superiorly, and in both MUC4 and MUC16 both superiorly and inferiorly, may indicate a need to decrease eyelid friction during blinking, especially in DE.

MUC1 and MUC16: critical for immune modulation in cancer therapeutics.

The Mucin (MUC) family, a range of highly glycosylated macromolecules, is ubiquitously expressed in mammalian epithelial cells. Such molecules are pivotal in establishing protective mucosal barriers, serving as defenses against pathogenic assaults. Intriguingly, the aberrant expression of specific MUC proteins, notably Mucin 1 (MUC1) and Mucin 16 (MUC16), within tumor cells, is intimately associated with oncogenesis, proliferation, and metastasis. This association involves various mechanisms, including cellular proliferation, viability, apoptosis resistance, chemotherapeutic resilience, metabolic shifts, and immune surveillance evasion. Due to their distinctive biological roles and structural features in oncology, MUC proteins have attracted considerable attention as prospective targets and biomarkers in cancer therapy. The current review offers an exhaustive exploration of the roles of MUC1 and MUC16 in the context of cancer biomarkers, elucidating their critical contributions to the mechanisms of cellular signal transduction, regulation of immune responses, and the modulation of the tumor microenvironment. Additionally, the article evaluates the latest advances in therapeutic strategies targeting these mucins, focusing on innovations in immunotherapies and targeted drugs, aiming to enhance customization and accuracy in cancer treatments.

Tumour-associated antigens in systemic lupus erythematosus: association with clinical manifestations and serological indicators.

OBJECTIVES: To explore the relationship of tumour-associated antigens (TAAs) with the clinical manifestations and serological markers of SLE. METHODS: This was a retrospective study. Clinical data of SLE patients were extracted from the electronic medical records, including serum levels of TAAs such as alpha-fetoprotein (AFP), carcinoembryonic antigen (CEA), cancer antigen (CA) 19-9, CA125, CA15-3 and cytokeratin 19-fragments (CYFRA21-1). TAA positivity was defined as serum level exceeding the upper limit of the corresponding reference range. RESULTS: A total of 149 SLE patients (SLE group) and 149 age- and sex-matched healthy subjects (control group) were enrolled. Compared with healthy controls, the SLE group had higher positivity rates for CA19-9 and CYFRA21-1, and elevated serum levels of CA125, CA15-3 and CYFRA21-1. SLE patients with TAA positivity were older, had a higher prevalence of serous effusion, pericardial effusion, albuminuria and thrombocytopenia, and lower positivity rate for anti-dsDNA than patients without TAA positivity. The levels of serum creatinine (SCR), blood urea nitrogen, glutamic oxalate transaminase and 24-h urinary protein were also higher in SLE patients with TAA positivity, but platelet count and serum albumin levels were lower. On logistic regression, thrombocytopenia and SCR levels were identified as independent risk factors for TAA positivity. CA125 positivity rate and serum levels of CA125 were associated with SLE disease activity. CONCLUSION: The positivity rates and serum levels of some TAAs were elevated in SLE, and thrombocytopenia and SCR levels were independent risk factors for TAA positivity.

Glycosylated extracellular mucin domains protect against SARS-CoV-2 infection at the respiratory surface.

Mucins play an essential role in protecting the respiratory tract against microbial infections while also acting as binding sites for bacterial and viral adhesins. The heavily O-glycosylated gel-forming mucins MUC5AC and MUC5B eliminate pathogens by mucociliary clearance. Transmembrane mucins MUC1, MUC4, and MUC16 can restrict microbial invasion at the apical surface of the epithelium. In this study, we determined the impact of host mucins and mucin glycans on epithelial entry of SARS-CoV-2. Human lung epithelial Calu-3 cells express the SARS-CoV-2 entry receptor ACE2 and high levels of glycosylated MUC1, but not MUC4 and MUC16, on their cell surface. The O-glycan-specific mucinase StcE specifically removed the glycosylated part of the MUC1 extracellular domain while leaving the underlying SEA domain and cytoplasmic tail intact. StcE treatment of Calu-3 cells significantly enhanced infection with SARS-CoV-2 pseudovirus and authentic virus, while removal of terminal mucin glycans sialic acid and fucose from the epithelial surface did not impact viral entry. In Calu-3 cells, the transmembrane mucin MUC1 and ACE2 are located to the apical surface in close proximity and StcE treatment results in enhanced binding of purified spike protein. Both MUC1 and MUC16 are expressed on the surface of human organoid-derived air-liquid interface (ALI) differentiated airway cultures and StcE treatment led to mucin removal and increased levels of SARS-CoV-2 replication. In these cultures, MUC1 was highly expressed in non-ciliated cells while MUC16 was enriched in goblet cells. In conclusion, the glycosylated extracellular domains of different transmembrane mucins might have similar protective functions in different respiratory cell types by restricting SARS-CoV-2 binding and entry.

Radiologically enlarged cardiophrenic lymph nodes and CA-125 in relation to diaphragmatic carcinomatosis, surgical outcome, and overall survival in advanced ovarian cancer.

BACKGROUND: We primarily aimed to determine whether the presence of enlarged cardiophrenic lymph nodes (CPLNs), visualized by computed tomography (CT), and CA-125 can be used to assess diaphragmatic carcinomatosis and residual disease (RD) in advanced ovarian cancer (AOC) patients treated with upfront surgery. The secondary aim was to determine the prognostic role of CT-CPLNs in overall survival (OS). MATERIAL AND METHODS: A single-center, retrospective, population-based study was conducted of patients who underwent surgery for AOC from January 1, 2014-December 31, 2018. Suspicious CT-CPLNs were defined as having a short axis ≥5 mm. The median survival and rate of survival were calculated with the Kaplan-Meier method using multivariate Cox regression analyses, including comparisons of complete cytoreductive surgery (CCS; defined as the complete removal of all intra-abdominal tumor) versus noncomplete cytoreductive surgery (non-CCS) and analyses related to CT-CPLN status and preoperative CA-125 values. RESULTS: We included 208 patients. CT-CPLNs correlated with both diaphragmatic carcinomatosis (OR 3.59, 95% CI 1.81-7.16, p < 0.01) and RD (OR 2.54, 95% CI 1.38-4.6, p = 0.003). When CCS was achieved, no differences in survival between patients with suspicious or nonsuspicious CT-CPLNs were found. The relationships between CA-125 ≥ 500 U/ml and diaphragmatic carcinomatosis (OR 3.51, 95% CI 1.86-6.64, p < 0.01) and RD (OR 2.41, 95% CI 1.33-4.38, p = 0.004) were positive. All data were adjusted for age and ECOG performance status. Survival analyses were also adjusted for RD. CONCLUSION: Enlarged CPLNs on CT scans and CA-125 levels correlate with diaphragmatic carcinomatosis and RD at the end of the surgery. The strongest prognostic factor for OS remains CCS, regardless of the CT-CPLN status.

NAV-001, a high-efficacy antibody-drug conjugate targeting mesothelin with improved delivery of a potent payload by counteracting MUC16/CA125 inhibitory effects.

Subsets of tumor-produced cell surface and secreted proteins can bind to IgG1 type antibodies and suppress their immune-effector activities. As they affect antibody and complement-mediated immunity, we call these proteins humoral immuno-oncology (HIO) factors. Antibody-drug conjugates (ADCs) use antibody targeting to bind cell surface antigens, internalize into the cell, then kill target cells upon liberation of the cytotoxic payload. Binding of the ADC antibody component by a HIO factor may potentially hamper ADC efficacy due to reduced internalization. To determine the potential effects of HIO factor ADC suppression, we evaluated the efficacy of a HIO-refractory, mesothelin-directed ADC (NAV-001) and a HIO-bound, mesothelin-directed ADC (SS1). The HIO factor MUC16/CA125 binding to SS1 ADC was shown to have a negative effect on internalization and tumor cell killing. The MUC16/CA125 refractory NAV-001 ADC was shown to have robust killing of MUC16/CA125 expressing and non-expressing tumor cells in vitro and in vivo at single, sub-mg/kg dosing. Moreover, NAV-001-PNU, which contains the PNU-159682 topoisomerase II inhibitor, demonstrated good stability in vitro and in vivo as well as robust bystander activity of resident cells while maintaining a tolerable safety profile in vivo. Single-dose NAV-001-PNU demonstrated robust tumor regression of a number of patient-derived xenografts from different tumor types regardless of MUC16/CA125 expression. These findings suggest that identification of HIO-refractory antibodies to be used in ADC format may improve therapeutic efficacy as observed by NAV-001 and warrants NAV-001-PNU's advancement to human clinical trials as a monotherapy to treat mesothelin-positive cancers.

Modulation of mucin secretion using combined polyethylene glycol-propylene glycol topical formulation in a hyperosmotic stress-based explant model.

Purpose: Ocular surface discomfort and dry eye disease are caused by a dysfunctional tear film. The efficacy of lubricating eye drops on the human eye is known, but the compositions may show differential effects on rescuing the tear film. Mucins form a critical layer of the tear film, a reduction of which may be causative for ocular surface conditions. Therefore, it is essential to develop relevant human-derived models to test mucin production. Methods: Human corneoscleral rims were obtained from a healthy donor (n = 8) post-corneal keratoplasty and cultured in DMEM/F12 media. Hyperosmolar stress mimicking dry eye disease was induced by exposing the corneoscleral rim tissues to +200 mOsml NaCl-containing media. The corneoscleral rims were treated with polyethylene glycol-propylene glycol (PEG-PG)-based topical formulation. Gene expression analysis was performed for NFAT5, MUC5AC, and MUC16. Secreted mucins were measured by enzyme-linked immunosorbent assay (ELISA) (Elabscience, Houston, TX, USA) for MUC5AC and MUC16. Results: The corneoscleral rims responded to hyperosmolar stress by upregulating NFAT5, a marker for increased osmolarity, as observed in the case of dry eye disease. The expression of MUC5AC and MUC16 was reduced upon an increase in hyperosmotic stress. The corneoscleral rim tissues showed induction of MUC5AC and MUC16 expression upon treatment with PEG-PG topical formulation but did not show significant changes in the presence of hyperosmolar treatments. Conclusion: Our findings showed that PEG-PG-based topical formulation slightly alleviated hyperosmolar stress-induced decrease in MUC5AC and MUC16 gene expression that is encountered in DED.

Pathological Implications of Mucin Signaling in Metastasis.

The dynamic mucosal layer provides a selective protective barrier for the epithelial cells lining the body cavities. Diverse human malignancies exploit their intrinsic role to protect and repair epithelia for promoting growth and survival. Aberrant expression of mucin has been known to be associated with poor prognosis of many cancers. However, the emergence of new paradigms in the study of metastasis recognizes the involvement of MUC1, MUC4, MUC5AC, MUC5B, and MUC16 during metastasis initiation and progression. Hence mucins can be used as an attractive target in future diagnostic and therapeutic strategies. In this review, we discuss in detail about mucin family and its domains and the role of different mucins in regulating cancer progression and metastasis. In addition, we briefly discuss insights into mucins as a therapeutic agent.

MUC16 promotes triple-negative breast cancer lung metastasis by modulating RNA-binding protein ELAVL1/HUR.

BACKGROUND: Triple-negative breast cancer (TNBC) is highly aggressive with an increased metastatic incidence compared to other breast cancer subtypes. However, due to the absence of clinically reliable biomarkers and targeted therapy in TNBC, outcomes are suboptimal. Hence, there is an urgent need to understand biological mechanisms that lead to identifying novel therapeutic targets for managing metastatic TNBC. METHODS: The clinical significance of MUC16 and ELAVL1 or Hu antigen R (HuR) was examined using breast cancer TCGA data. Microarray was performed on MUC16 knockdown and scramble TNBC cells and MUC16-associated genes were identified using RNA immunoprecipitation and metastatic cDNA array. Metastatic properties of MUC16 were evaluated using tail vein experiment. MUC16 and HuR downstream pathways were confirmed by ectopic overexpression of MUC16-carboxyl-terminal (MUC16-Cter), HuR and cMyc as well as HuR inhibitors (MS-444 and CMLD-2) in TNBC cells. RESULTS: MUC16 was highly expressed in TNBC and correlated with its target HuR. Depletion of MUC16 showed decreased invasion, migration, and colony formation abilities of human and mouse TNBC cells. Mice injected with MUC16 depleted cells were less likely to develop lung metastasis (P = 0.001). Notably, MUC16 and HuR were highly expressed in the lung tropic TNBC cells and lung metastases. Mechanistically, we identified cMyc as a HuR target in TNBC using RNA immunoprecipitation and metastatic cDNA array. Furthermore, MUC16 knockdown and pharmacological inhibition of HuR (MS-444 and CMLD-2) in TNBC cells showed a reduction in cMyc expression. MUC16-Cter or HuR overexpression models indicated MUC16/HuR/cMyc axis in TNBC cell migration. CONCLUSIONS: Our study identified MUC16 as a TNBC lung metastasis promoter that acts through HuR/cMyc axis. This study will form the basis of future studies to evaluate the targeting of both MUC16 and HuR in TNBC patients.

Cancer Antigen 125 Expression Enhances the Gemcitabine/Cisplatin-Resistant Tumor Microenvironment in Bladder Cancer.

Cancer antigen 125 (CA125) is one of the mucin family proteins and is a serum tumor marker for various tumors, such as ovarian cancer, endometrial cancer, pancreatic cancer, and bladder cancer. CA125 is used to distinguish between benign and malignant tumors, monitor the response to chemotherapy, and detect relapse after initial treatment. Recently, CA125 was reported to be involved in chemoresistance through the physical characteristics of mucin or by modifying the immune tumor-microenvironment. However, the relationship between CA125 expression and chemoresistance in bladder cancer is still unclear. In this study, the clinicopathologic features of bladder cancer with CA125 expression and the status of the tumor-microenvironment related to gemcitabine/cisplatin resistance were investigated using publicly available data sets (Cancer Genome Atlas Expression, GSE169455 data set) from the cBioPortal website, the National Center for Biotechnology Information website, and an in-house case collection of bladder cancer. The cases with CA125 expression had poorer disease-free and overall survival rates than those without CA125 expression. A mucinous area surrounding cancer cells was frequently detected in cases with CA125 expression (81%; 13/16 cases). CA125 expression was also related to the immunosuppressive tumor-microenvironment through the infiltration of immunosuppressive immune cells, such as regulatory T cells and M2 macrophages. These results suggest that the status of tumor-microenvironment associated with CA125 is involved in gemcitabine/cisplatin resistance in bladder cancer.

[MUC16: The Novel Target for Tumor Therapy].

Mucin16 (MUC16), also known as carbohydrate antigen 125 (CA125), is a glycoprotein antigen that can be recognized by the monoclonal antibody OC125 detected from epithelial ovarian carcinoma antigen by Bast et al in 1981. CA125 is not present in normal ovarian tissue but is usually elevated in the serum of epithelial ovarian carcinoma patients. CA125 is the most commonly used serologic biomarker for the diagnosis and recurrence monitoring of epithelial ovarian carcinoma. MUC16 is highly expressed in varieties of tumors. MUC16 can interact with galectin-1/3, mesothelin, sialic acid-binding immunoglobulin-type lectins-9 (Siglec-9), and other ligands. MUC16 plays an important role in tumor genesis, proliferation, migration, invasion, and tumor immunity through various signaling pathways. Besides, therapies targeting MUC16 have some significant achievements. Related preclinical studies and clinical trials are in progress. MUC16 may be a potential novel target for tumor therapy. This article will review the mechanism of MUC16 in tumor genesis and progression, and focus on the research actuality of MUC16 in tumor therapy. This article also provides references for subsequent tumor therapy studies targeting MUC16.
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Oncolytic adenovirus with MUC16-BiTE shows enhanced antitumor immune response by reversing the tumor microenvironment in PDX model of ovarian cancer.

The improved survival rate of ovarian cancer (OC) is related to the action of infiltrating cytotoxic T lymphocytes (CTLs). Recently, oncolytic adenoviruses (OAds) have emerged as a key player in treating solid tumors; however, the immunosuppressive tumor microenvironment (TME) and the body-mediated antiviral immune response limit their therapeutic effect. In this study, we tested the hypothesis that bispecific T-cell engagers (BiTEs) could activate and redirect CTLs to increase the anti-tumor effect of OAds. We modified the parental OAd to express a MUC16-targeting BiTE antibody (OAd-MUC16-BiTE), which retained its oncolytic properties and replication ability in vitro. This BiTE secreted from infected tumor cells into the microenvironment binds to MUC16 on target cells and cross-links them to CD3 on T cells, leading to activation, proliferation, and toxicity of T cells against MUC16+ tumor cells. In cell coculture assays, OAd-MUC16-BiTE-mediated oncolysis enhanced T-cell-mediated tumor cell killing and bystander effect. In ex vivo tumor cultures freshly derived from OC patients, OAd-MUC16-BiTE overcame the suppressed immune TME, achieving stronger toxicity than the parental virus. Moreover, in the cell-derived xenograft and patient-derived xenograft model, OAd-MUC16-BiTE showed stronger antitumor activity and increased the number of CTLs, compared with the parental virus. Further, we demonstrated that the OAd-MUC16-BiTE-mediated anti-tumor activity is related to the reversal of the TME and improved MHC I antigen presentation. Overall, our results show how arming OAds with BiTE can overcome limitations in oncolytic virotherapy, yielding a potent therapy that is ready for clinical assessment.

Circulating miR-141 as a potential biomarker for diagnosis, prognosis and therapeutic targets in gallbladder cancer.

MicroRNA-141(miR-141) has been reported to play vital roles in the regulation of carcinogenesis and cancer progression. However, the biological function of miR-141 in GBC has received less attention. The aim of this study was to estimate the potential value of the expression level of miR-141 as a diagnostic and prognostic blood-based biomarker in gallbladder cancer (GBC) patients. Meanwhile, to explore its biological role in GBC cells. RT-PCR was employed to confirm the expression of miR-141 in ten paired tissue samples (10 GBC tissues and 10 adjacent normal gallbladder tissues), GBC cell lines and peripheral blood specimens from 98 GBC patients and 60 healthy controls. MTT assay was used to evaluate the GBC cells proliferation and flow cytometry was used to detect the cell apoptosis. Receiver operating characteristic curve analysis and the area under the curve (AUC) were used to evaluate the value of miR-141 plasma levels for GBC diagnosis. Finally, clinicopathological and survival data of all GBC patients were collected and analyzed. Here, we confirmed that the expression of miR-141 were upregulated in primary gallbladder cancer cells and tissues compared with human gallbladder epithelial cells and adjacent normal tissues (P < 0.0001). Meanwhile, we found that downregulated expression of miR-141 by miR-141 inhibitor could induce apoptosis and inhibit proliferation of GBC cells. Additionally, elevated plasma miR-141 expression was also detected in the peripheral blood of GBC patients compared with healthy controls (P < 0.0001). The AUC value of miR-141 for GBC diagnosis was 0.894 (95% CI 0.843-0.945), which was more valuable than those including carcinoembryonic antigen (CEA) (0.713, 95% CI 0.633-0.793), carbohydrate antigen 125 (CA125) (0.837, 95% CI 0.776-0.899) and carbohydrate antigen 19-9 (CA19-9) (0.869, 95% CI 0.813-0.924). The high expression level of miR-141 in plasma was significantly associated with tumor invasion (P = 0.008), lymph node metastasis (P < 0.0001) and advanced pathologic tumor/node/metastasis (pTNM) stage (P = 0.009). More importantly, high plasma miR-141 expression was an independent prognostic factor for predicting poorer long-term survival in GBC patients. Elevated expression of circulating miR-141 in peripheral blood might be a potential novel biomarker for diagnosis and prognosis of GBC patients. Downregulated expression of miR-141 could inhibit proliferation and induce apoptosis of GBC cells, that provide a potential therapeutic target for GBC.

MUC16 Promotes Liver Metastasis of Pancreatic Ductal Adenocarcinoma by Upregulating NRP2-Associated Cell Adhesion.

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal types of cancer, as it commonly metastasizes to the liver resulting in an overall poor prognosis. However, the molecular mechanism involved in liver metastasis remains poorly understood. Here, we aimed to identify the MUC16-mediated molecular mechanism of PDAC-liver metastasis. Previous studies demonstrated that MUC16 and its C-terminal (Cter) domain are involved in the aggressiveness of PDAC. In this study, we observed MUC16 and its Cter expression significantly high in human PDAC tissues, PDAC organoids, and metastatic liver tissues, while no expression was observed in normal pancreatic tissues using IHC and immunofluorescence (IFC) analyses. MUC16 knockdown in SW1990 and CD18/HPAF PDAC cells significantly decreased the colony formation, migration, and endothelial/p-selectin binding. In contrast, MUC16-Cter ectopic overexpression showed significantly increased colony formation and motility in MiaPaCa2 pancreatic cancer cells. Interestingly, MUC16 promoted cell survival and colonization in the liver, mimicking an ex vivo environment. Furthermore, MUC16 enhanced liver metastasis in the in vivo mouse model. Our integrated analyses of RNA-sequencing suggested that MUC16 alters Neuropilin-2 (NRP2) and cell adhesion molecules in pancreatic cancer cells. Furthermore, we identified that MUC16 regulated NRP2 via JAK2/STAT1 signaling in PDAC. NRP2 knockdown in MUC16-overexpressed PDAC cells showed significantly decreased cell adhesion and migration. Overall, the findings indicate that MUC16 regulates NRP2 and induces metastasis in PDAC. IMPLICATIONS: This study shows that MUC16 plays a critical role in PDAC liver metastasis by mediating NRP2 regulation by JAK2/STAT1 axis, thereby paving the way for future therapy efforts for metastatic PDAC.

Preclinical Evaluation of a Humanized, Near-Infrared Fluorescent Antibody for Fluorescence-Guided Surgery of MUC16-Expressing Pancreatic Cancer.

Surgery remains the only potentially curative treatment option for pancreatic cancer, but resections are made more difficult by infiltrative disease, proximity of critical vasculature, peritumoral inflammation, and dense stroma. Surgeons are limited to tactile and visual cues to differentiate cancerous tissue from normal tissue. Furthermore, translating preoperative images to the intraoperative setting poses additional challenges for tumor detection, and can result in undetected and unresected lesions. Thus, pancreatic ductal adenocarcinoma (PDAC) has high rates of incomplete resections, and subsequently, disease recurrence. Fluorescence-guided surgery (FGS) has emerged as a method to improve intraoperative detection of cancer and ultimately improve surgical outcomes. Initial clinical trials have demonstrated feasibility of FGS for PDAC, but there are limited targeted probes under investigation for this disease, highlighting the need for development of additional novel biomarkers to reflect the PDAC heterogeneity. MUCIN16 (MUC16) is a glycoprotein that is overexpressed in 60-80% of PDAC. In our previous work, we developed a MUC16-targeted murine antibody near-infrared conjugate, termed AR9.6-IRDye800, that showed efficacy in detecting pancreatic cancer. To build on the translational potential of this imaging probe, a humanized variant of the AR9.6 fluorescent conjugate was developed and investigated herein. This conjugate, termed huAR9.6-IRDye800, showed equivalent binding properties to its murine counterpart. Using an optimized dye:protein ratio of 1:1, in vivo studies demonstrated high tumor to background ratios in MUC16-expressing tumor models, and delineation of tumors in a patient-derived xenograft model. Safety, biodistribution, and toxicity studies were conducted. These studies demonstrated that huAR9.6-IRDye800 was safe, did not yield evidence of histological toxicity, and was well tolerated in vivo. The results from this work suggest that AR9.6-IRDye800 is an efficacious and safe imaging agent for identifying pancreatic cancer intraoperatively through fluorescence-guided surgery.

Truncated O-Glycan-Bearing MUC16 Enhances Pancreatic Cancer Cells Aggressiveness via α4ß1 Integrin Complexes and FAK Signaling.

Elevated levels of Mucin-16 (MUC16) in conjunction with a high expression of truncated O-glycans is implicated in playing crucial roles in the malignancy of pancreatic ductal adenocarcinoma (PDAC). However, the mechanisms by which such aberrant glycoforms present on MUC16 itself promote an increased disease burden in PDAC are yet to be elucidated. This study demonstrates that the CRISPR/Cas9-mediated genetic deletion of MUC16 in PDAC cells decreases tumor cell migration. We found that MUC16 enhances tumor malignancy by activating the integrin-linked kinase and focal adhesion kinase (ILK/FAK)-signaling axis. These findings are especially noteworthy in truncated O-glycan (Tn and STn antigen)-expressing PDAC cells. Activation of these oncogenic-signaling pathways resulted in part from interactions between MUC16 and integrin complexes (α4ß1), which showed a stronger association with aberrant glycoforms of MUC16. Using a monoclonal antibody to functionally hinder MUC16 significantly reduced the migratory cascades in our model. Together, these findings suggest that truncated O-glycan containing MUC16 exacerbates malignancy in PDAC by activating FAK signaling through specific interactions with α4 and ß1 integrin complexes on cancer cell membranes. Targeting these aberrant glycoforms of MUC16 can aid in the development of a novel platform to study and treat metastatic pancreatic cancer.

BRAK and APRIL as novel biomarkers for ovarian tumors.

Aims: To evaluate BRAK and APRIL in serum samples from healthy patients and an ovarian tumor group and analyze their effective value as biomarkers. Materials & methods: BRAK and APRIL were measured in 197 serum samples including 34 healthy controls, 48 patients with benign ovarian cysts and 115 patients with ovarian cancer, and the best statistical cut-off values were calculated. Then, the sensitivity, specificity, accuracy, positive predictive value and negative predictive value for selected cut-off points were assessed. Results: The healthy control group had statistically significant higher BRAK and lower APRIL than the ovarian tumor group. BRAK was excellent for differentiating healthy patients from patients with ovarian tumors, showing area under the receiver operating characteristic curve 0.983, 98.16% sensitivity and 100% specificity. When BRAK was combined with APRIL and CA-125, it also played a role in distinguishing benign cysts from malignancies with area under the curve 0.864, 81.74% sensitivity and 79.17% specificity. Conclusions: BRAK and APRIL are good candidates for ovarian tumor biomarkers.

Ovarian Cancer Ascites Inhibits Transcriptional Activation of NK Cells Partly through CA125.

Malignant ascites is a common clinical problem in ovarian cancer. NK cells are present in the ascites, but their antitumor activity is inhibited. The underlying mechanisms of the inhibition have yet to be fully elucidated. Using an Fcγ receptor-mediated NK cell activation assay, we show that ascites from ovarian cancer patients potently inhibits NK cell activation. Part of the inhibitory activity is mediated by CA125, a mucin 16 fragment shed from ovarian cancer tumors. Moreover, transcriptional analyses by RNA sequencing reveal upregulation of genes involved in multiple metabolic pathways but downregulation of genes involved in cytotoxicity and signaling pathways in NK cells purified from ovarian cancer patient ascites. Transcription of genes involved in cytotoxicity pathways are also downregulated in NK cells from healthy donors after in vitro treatment with ascites or with a CA125-enriched protein fraction. These results show that ascites and CA125 inhibit antitumor activity of NK cells at transcriptional levels by suppressing expression of genes involved in NK cell activation and cytotoxicity. Our findings shed light on the molecular mechanisms by which ascites inhibits the activity of NK cells and suggest possible approaches to reactivate NK cells for ovarian cancer immunotherapy.