CA125 suppresses amatuximab immune-effector function and elevated serum levels are associated with reduced clinical response in first line mesothelioma patients

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.

NAV-003, a bispecific antibody targeting a unique mesothelin epitope and CD3ε with improved cytotoxicity against humoral immunosuppressed tumors

Mesothelin (MSLN) is a cell surface protein overexpressed in a number of cancer types. Several antibody- and cellular-based MSLN targeting agents have been tested in clinical trials where their therapeutic efficacy has been moderate at best. Previous studies using antibody and Chimeric Antigen Receptor-T cells (CAR-T) strategies have shown the importance of particular MSLN epitopes for optimal therapeutic response, while other studies have found that certain MSLN-positive tumors can produce proteins that can bind to subsets of IgG1-type antibodies and suppress their immune effector activities. In an attempt to develop an improved anti-MSLN targeting agent, we engineered a humanized divalent anti-MSLN/anti-CD3ε bispecific antibody that avoids suppressive factors, can target a MSLN epitope proximal to the tumor cell surface, and is capable of effectively binding, activating, and redirecting T cells to the surface of MSLN-positive tumor cells. NAV-003 has shown significantly improved tumor cell killing against lines producing immunosuppressive proteins in vitro and in vivo. Moreover, NAV-003 demonstrated good tolerability in mice and efficacy against patient-derived mesothelioma xenografts co-engrafted with human peripheral blood mononuclear cells. Together these data support the potential for NAV-003 clinical development and human proof-of-concept studies in patients with MSLN-expressing cancers.

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.

Prognostic Value of Elevated Pre-treatment Serum CA-125 in Epithelial Ovarian Cancer: A Meta-Analysis

Background

CA-125 is a clinical biomarker with predictive effect on the prognosis of different cancers. Numerous clinical trials have been conducted to investigate the possibility of using the pretreatment level of CA-125 to predict the prognosis of epithelial ovarian cancer (EOC). However, its value in predicting prognosis remains controversial. The purpose of this meta-analysis was to assess the predictive value of pretreatment CA-125 levels for prognosis in EOC patients.

Methods

We searched the EMBASE, Cochrane library, PubMed and Web of Science databases for studies published up to 3 December 2021, according to specific inclusion and exclusion criteria. The clinical studies that were included investigated the relationship between pretreatment CA-125 levels and ovarian cancer prognosis. Combined hazard ratios (HR) of overall survival (OS) and progression-free survival (PFS) reported in the studies were compared and analyzed using fixed-effects/random-effects models. Sensitivity analysis was used to assess study stability, while Egger’s and Begg’s tests were used to assess publication bias.

Results

This meta-analysis included 23 studies published in 2004 - 2021 with a total of 10,594 EOC patients. Comprehensive analysis demonstrated that the serum level of CA-125 before treatment was significantly correlated with overall survival (OS: HR=1.62, 95%CI=1.270-2.060, p<0.001) and progression-free survival (PFS: HR=1.59, PFS: HR=1.59, 95%CI=1.44~1.76, p<0.001). After comparing data from different FIGO stages and treatments, we discovered that a high pre-treatment serum CA-125 level was associated with a low survival rate.

Conclusion

According to the results of this study, a higher pre-treatment serum CA-125 level is associated with poor survival outcomes, which can be utilized to predict the prognosis of EOC patients. Pre-treatment serum CA-125 level might provide reliable basis for predicting the risk of EOC disease progression. This study is registered with the International Prospective Register of Systematic Reviews (CRD42022300545).

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=300545, identifier [CRD42022300545].

Block-Removed Immunoglobulin Technology to enhance rituximab effector function by counteracting CA125-mediated immunosuppression

Rituximab (RTX) is a CD20-targeting antibody that is the standard-of-care for patients with non-Hodgkin Lymphoma (NHL) cases. RTX's mechanism of action includes complement-dependent cytotoxicity (CDC) and antibody-dependent cellular cytotoxicity (ADCC). Recent clinical evidence suggests that high serum levels of the tumor-produced mucin 16 (MUC16) and cancer antigen 125 (CA125) have a negative impact on the effectiveness of RTX clinical activity in up to 40% of patients with follicular lymphoma. The present study sought to understand the possible mechanism underlying these results; therefore, cellular and molecular analyses of RTX and CA125 interaction were peformed, and a library of RTX variants was generated using a proprietary technology called Block-Removed Immunoglobulin Technology that combines randomized amino acid substitutions and high-throughput functional screenings to identify CA125-refractory RTX variants. The present study demonstrated that CA125 could bind to RTX and reduce its tumor cell killing activity. Furthermore, the study characterized an RTX variant, named NAV-006 (RTX-N109D), which was more refractory to the immunosuppressive effects mediated by CA125 as evidenced by its reduced CA125 interaction and increased activity of ADCC and CDC when compared with parent RTX. Taken together, these findings warranted further investigation on NAV-006 as a next generation anti-CD20 antibody that could improve the efficacy of parent RTX in NHL patients with high levels of CA125.

Hitting the Bull's-Eye: Mesothelin's Role as a Biomarker and Therapeutic Target for Malignant Pleural Mesothelioma

Malignant pleural mesothelioma (MPM) is an aggressive cancer with limited treatment options and poor prognosis. MPM originates from the mesothelial lining of the pleura. Mesothelin (MSLN) is a glycoprotein expressed at low levels in normal tissues and at high levels in MPM. Many other solid cancers overexpress MSLN, and this is associated with worse survival rates. However, this association has not been found in MPM, and the exact biological role of MSLN in MPM requires further exploration. Here, we discuss the current research on the diagnostic and prognostic value of MSLN in MPM patients. Furthermore, MSLN has become an attractive immunotherapy target in MPM, where better treatment strategies are urgently needed. Several MSLN-targeted monoclonal antibodies, antibody-drug conjugates, immunotoxins, cancer vaccines, and cellular therapies have been tested in the clinical setting. The biological rationale underpinning MSLN-targeted immunotherapies and their potential to improve MPM patient outcomes are reviewed.

Roles of CA125 in diagnosis, prediction, and oncogenesis of ovarian cancer

After it was discovered approximately 40 years ago, carbohydrate antigen 125 (CA125) became the most widely used and concerning biomarker in ovarian cancer screening. However, there is still controversy about its role in clinical practice. CA125 is not sufficiently reliable in diagnosis to screen for early-stage ovarian cancer. On the other hand, CA125 has been a valuable indicator for evaluating chemotherapeutic efficacy and prognosis. We still do not know much about its biological role, and several studies have indicated that this marker participates in the occurrence and development of ovarian cancer. Currently, an increasing number of scholars have begun to pay attention to CA125-targeted treatment strategies. In the interest of better design and development of anticancer therapies, a renewed and systematic understanding of the roles of CA125 in diagnosis, prediction, and tumorigenesis is warranted.

Combined Preoperative LMR and CA125 for Prognostic Assessment of Ovarian Cancer

Objectives: To investigate the role of inflammation-related factors, lymphocyte-to-monocyte ratio (LMR) alone and combined detection with cancer antigen 125 (CA125), in the prognostic assessment of ovarian cancer (OC). Methods: A retrospective clinicopathologic review was performed. The receiver-operating characteristic (ROC) curves of LMR, CA125, and COLC predicting mortality in OC patients were constructed. Besides, Kaplan-Meier and Cox logistic regression models were used to plot the survival curves and determine the independent prognostic factors. Results: A total of 214 OC patients were identified in this cohort. The mean duration of follow-up was 64 months (minimum 8 months, maximum 116 months). In this cohort, 135 cases died (63.1%), and the median progression-free survival (PFS) and overall survival (OS) were 20 and 39.5 months, respectively. Results of the multivariate Cox regression model showed that LMR≤3.8 (HR = 0.494, 95% CI: 0.329-0.742, P = 0.001) and CA125>34 U/ml (HR = 1.641, 95% CI: 1.057-2.550, P = 0.027) were significantly associated with poor PFS; and LMR≤3.8 (HR = 0.459, 95% CI: 0.306-0.688, P = <0.001) and CA125>34 U/ml (HR = 1.946, 95% CI: 1.256-3.015, P = 0.003) were significantly associated with OS. Furthermore, the area under the curve of COLC was higher (0.713) than that of LMR (0.709) or CA125 (0.583), the specificity of COLC was higher (75.9%) than that of LMR (62%) or CA125 (40.5%) in predicting mortality in OC patients. Conclusions: LMR alone and combined with CA125 might be used as predictive markers in OC. Furthermore, as a prognostic factor, COLC might have a higher specificity to predict the outcome.

MUC16 suppresses human and murine innate immune responses

OBJECTIVE

MUC16, the mucin that contains the CA125 epitopes, suppresses the cytolytic responses of human NK cells and inhibits the efficacy of therapeutic antibodies. Here, we provide further evidence of the regulatory role of MUC16 on human and murine NK cells and macrophages.

METHODS

Target cell cytolysis and doublet formation assays were performed to assess effects of MUC16 on human NK cells. The effect of MUC16 on ovarian tumor growth was determined in a mouse model by monitoring survival and ascites formation. Innate immune cells from spleens and peritoneal cavities of mice were isolated and stimulated in vitro with anti-CD40 antibody, lipopolysaccharide and IFN-γ and their ability to cytolyse MUC16 expressing and non-expressing cells was determined.

RESULTS

We confirm that MUC16 inhibits cytolysis by human NK cells as well as the formation of NK-tumor conjugates. Mice implanted with MUC16-knockdown OVCAR-3 show >2-fold increase in survival compared to controls. Murine NK cells and macrophages are more efficient at lysing MUC16-knockdown cells. In vitro cytotoxicity assays with NK cells and macrophages isolated from mice stimulated with anti-CD40 antibody showed 2-3-fold increased activity against the MUC16-knockdown cells as compared to matching target cells expressing this mucin. Finally, knockdown of MUC16 increased the susceptibility of cancer cells to ADCC by murine splenocytes.

CONCLUSIONS

For the first time, we demonstrate the immunoregulatory effects of MUC16 on murine NK cells and macrophages. Our study implies that the immunoregulatory role of MUC16 on murine NK cells and macrophages should be considered when examining the biology of MUC16 in mouse models.