Characterization of human ovarian carcinoma-associated antigens defined by novel monoclonal antibodies with tumor-restricted specificity

Overview of Trop-2 in Cancer: From Pre-Clinical Studies to Future Directions in Clinical Settings

Trophoblast cell surface antigen-2 (Trop-2) is a glycoprotein that was first described as a membrane marker of trophoblast cells and was associated with regenerative abilities. Trop-2 overexpression was also described in several tumour types. Nevertheless, the therapeutic potential of Trop-2 was widely recognized and clinical studies with drug–antibody conjugates have been initiated in various cancer types. Recently, these efforts have been rewarded with the approval of sacituzumab govitecan from both the Food and Drug Administration (FDA) and European Medicines Agency (EMA), for metastatic triple-negative breast cancer patients. In our work, we briefly summarize the various characteristics of cancer cells overexpressing Trop-2, the pre-clinical activities of specific inhibitors, and the role of anti-Trop-2 therapy in current clinical practice. We also review the ongoing clinical trials to provide a snapshot of the future developments of these therapies.

The affinity of antigen-binding domain on the antitumor efficacy of CAR T cells: Moderate is better

The overall efficacy of chimeric antigen receptor modified T cells (CARTs) remain limited in solid tumors despite intensive studies that aim at targeting multiple antigens, enhancing migration, reducing tonic signaling, and improving tumor microenvironment. On the other hand, how the affinity and engaging kinetics of antigen-binding domain (ABD) affects the CART's efficacy has not been carefully investigated. In this article, we first analyzed 38 published solid tumor CART trials and correlated the response rate to their ABD affinity. Not surprisingly, majority (25 trials) of the CARTs utilized high-affinity ABDs, but generated merely 5.7% response rate. In contrast, 35% of the patients treated with the CARTs built from moderate-affinity ABDs had clinical responses. Thus, CARTs with moderate-affinity ABDs not only have less off-target toxicity, but also are more effective. We then reviewed the effects of ABD affinity on the biology and function of CARTs, providing further evidence that moderate-affinity ABDs may be better in CART development. In the end, we propose that a fast-on/fast-off (high Kon and Koff ) kinetics of CART-target engagement in solid tumor allow CARTs to generate sufficient signaling to kill tumor cells without being driven to exhaustion. We believe that studying the ABD affinity and the kinetics of CART-tumor interaction may hold a key to designing effective CARTs for solid tumors.

Role of antibody engineering in generation of derivatives starting from MOv19 MAb: 40 years of biological/therapeutic tools against folate receptor alfa

In the 1980s, we developed and characterized numerous murine monoclonal antibodies (MAbs) directed against human tumor-associated antigens. This mini review is focused on the generation of derivatives of an anti-folate receptor α (FRα) MAbs, named MOv19, exploiting the antibody-engineering progresses in the last 40 years. The FRα location on the luminal surface of proliferating epithelial cells, inaccessible to circulation, versus its over-expression in the entire surface of numerous carcinomas suggested a role for anti-FRα MAbs in the diagnosis and/or treatment of solid tumors. Presently, two MOv19 derivatives are in clinical trials: a chimeric resurfaced version in an antibody-drug conjugate format (SORAYA trial, 2022) and the murine scFv in a second generation chimeric antigen receptor, CAR-T (Phase Ia, 2021). MOv19 and its derivatives could be considered a relevant example that well-characterized anti-tumor murine Mabs and antibody engineering could be combined to generate useful therapeutic tools.

Tandem CAR-T cells targeting FOLR1 and MSLN enhance the antitumor effects in ovarian cancer

Given the heterogeneity of solid tumors, single-target CAR-T cell therapy often leads to recurrence, especially in ovarian cancer (OV). Here, we constructed a Tandem-CAR targeting two antigens with secretory activity (IL-12) to improve the effects of CAR-T cell therapy. Twenty coexpressed upregulated genes were identified from the GEO database, and we found FOLR1 (folate receptor 1) and MSLN (mesothelin) were specifically and highly expressed in cancer tissues and only 11.25% of samples were negative for both antigens. We observed an increased proliferation rate for these three CAR-T cells, and Tandem CAR-T cells could efficiently lyse antigen-positive OV cells in vitro and secrete higher levels of cytokines than single-target CAR-T cells. More importantly, in vivo experiments indicated that Tandem CAR-T cells markedly decreased tumor volume, exhibited enhanced antitumor activity, and prolonged mouse survival. Furthermore, the infiltration and persistence of T cells in the Tandem-CAR group were higher than those in the MSLN-CAR and Control-T groups but comparable to those in the FOLR1-CAR group. Collectively, this study demonstrated that Tandem CAR-T cells secreting IL-12 could enhance immunotherapeutic effects by reducing tumor antigen escape and increasing T cell functionality, which could be a promising therapeutic strategy for OV and other solid tumors.

To Conjugate or to Package? A Look at Targeted siRNA Delivery Through Folate Receptors

RNA interference (RNAi) applications have evolved from experimental tools to study gene function to the development of a novel class of gene-silencing therapeutics. Despite decades of research, it was not until August 2018 that the US FDA approved the first-ever RNAi drug, marking a new era for RNAi therapeutics. Although there are many limitations associated with the inherent structure of RNA, delivery to target cells and tissues remains the most challenging. RNAs are unable to diffuse across cellular membranes due to their large size and polyanionic backbone and, therefore, require a delivery vector. RNAi molecules can be conjugated to a targeting ligand or packaged into a delivery vehicle. Alnylam has used both strategies in their FDA-approved formulations to achieve efficient delivery to the liver. To harness the full potential of RNAi therapeutics, however, we must be able to target additional cells and tissues. One promising target is the folate receptor α, which is overexpressed in a variety of tumors despite having limited expression and distribution in normal tissues. Folate can be conjugated directly to the RNAi molecule or used to functionalize delivery vehicles. In this review, we compare both delivery strategies and discuss the current state of research in the area of folate-mediated delivery of RNAi molecules.

Cancer immunotherapy: dawn of the death of cancer?

Cancer is one of the proficient evaders of the immune system which claims millions of lives every year. Developing therapeutics against cancer is extremely challenging as cancer involves aberrations in self, most of which are not detected by the immune system. Conventional therapeutics like chemotherapy, radiotherapy are not only toxic but they significantly lower the quality of life. Immunotherapy, which gained momentum in the 20th century, is emerging as one of the alternatives to the conventional therapies and is relatively less harmful but more costly. This review explores the modern advances in an array of such therapies and try to compare them along with a limited analysis of concerns associated with them.

Exploiting the folate receptor α in oncology

Folate receptor α (FRα) came into focus as an anticancer target many decades after the successful development of drugs targeting intracellular folate metabolism, such as methotrexate and pemetrexed. Binding to FRα is one of several methods by which folate is taken up by cells; however, this receptor is an attractive anticancer drug target owing to the overexpression of FRα in a range of solid tumours, including ovarian, lung and breast cancers. Furthermore, using FRα to better localize effective anticancer therapies to their target tumours using platforms such as antibody-drug conjugates, small-molecule drug conjugates, radioimmunoconjugates and, more recently, chimeric antigen receptor T cells could further improve the outcomes of patients with FRα-overexpressing cancers. FRα can also be harnessed for predictive biomarker research. Moreover, imaging FRα radiologically or in real time during surgery can lead to improved functional imaging and surgical outcomes, respectively. In this Review, we describe the current status of research into FRα in cancer, including data from several late-phase clinical trials involving FRα-targeted therapies, and the use of new technologies to develop FRα-targeted agents with improved therapeutic indices.

IgE Antibodies: From Structure to Function and Clinical Translation

Immunoglobulin E (IgE) antibodies are well known for their role in mediating allergic reactions, and their powerful effector functions activated through binding to Fc receptors FcεRI and FcεRII/CD23. Structural studies of IgE-Fc alone, and when bound to these receptors, surprisingly revealed not only an acutely bent Fc conformation, but also subtle allosteric communication between the two distant receptor-binding sites. The ability of IgE-Fc to undergo more extreme conformational changes emerged from structures of complexes with anti-IgE antibodies, including omalizumab, in clinical use for allergic disease; flexibility is clearly critical for IgE function, but may also be exploited by allosteric interference to inhibit IgE activity for therapeutic benefit. In contrast, the power of IgE may be harnessed to target cancer. Efforts to improve the effector functions of therapeutic antibodies for cancer have almost exclusively focussed on IgG1 and IgG4 subclasses, but IgE offers an extremely high affinity for FcεRI receptors on immune effector cells known to infiltrate solid tumours. Furthermore, while tumour-resident inhibitory Fc receptors can modulate the effector functions of IgG antibodies, no inhibitory IgE Fc receptors are known to exist. The development of tumour antigen-specific IgE antibodies may therefore provide an improved immune functional profile and enhanced anti-cancer efficacy. We describe proof-of-concept studies of IgE immunotherapies against solid tumours, including a range of in vitro and in vivo evaluations of efficacy and mechanisms of action, as well as ex vivo and in vivo safety studies. The first anti-cancer IgE antibody, MOv18, the clinical translation of which we discuss herein, has now reached clinical testing, offering great potential to direct this novel therapeutic modality against many other tumour-specific antigens. This review highlights how our understanding of IgE structure and function underpins these exciting clinical developments.

Folate-targeted immunotherapies: Passive and active strategies for cancer

The glycoprotein FRα is a membrane-attached transport protein that is shielded from the immune system in healthy cells. However, it is upregulated in various malignancies, involved in cancer development and is also immunogenic. Furthermore, FRα is a tumor-associated antigen endowed with unique properties, thus rendering it a suitable target for immunotherapeutic development in cancer. Various anti- FRα immunotherapeutic strategies are thus currently being developed and clinically assessed for the treatment of various solid tumors. These approaches include passive anti-FRα immunotherapies, such as monoclonal antibodies, or active immunotherapies, such as CART, folate haptens and vaccines. In this review, we will explore the advances in the field of FRα-based immune therapies and discuss both their successes and shortcomings in the clinical setting.

Lymphocytes in Cellular Therapy: Functional Regulation of CAR T Cells

Lymphocytes especially autologous T cells have been used for the treatment of numerous indications including cancers, autoimmune disorders and infectious diseases. Very recently, FDA approved Chimeric Antigen Receptor T cells (CAR T cells) therapy for relapse and refractory CD19+ B cell acute lymphoblastic leukemia (r/r B-ALL) and r/r diffuse large B cell lymphoma (r/r DLBCL) upon their remarkable success in multiple Phase I-II clinical trials. While CAR T cells are considered as major breakthrough in the field of cancer immunotherapy, the regulation of CAR T cells remains poorly understood. In this review we will discuss the strategies that regulate the CAR T cells efficacy and persistence with focus on roles of different structural component of CAR construct. Different domains of CAR construct, for example, antigen binding domain, hinge, transmembrane, and signaling domain as well as immune-regulatory cytokines have significant impact on CAR T cell efficacy. Finally, this review will highlight the strategies that will promote CAR T cells efficacy and will reduce the toxicity.

An immunologically relevant rodent model demonstrates safety of therapy using a tumour-specific IgE

BACKGROUND

Designing biologically informative models for assessing the safety of novel agents, especially for cancer immunotherapy, carries substantial challenges. The choice of an in vivo system for studies on IgE antibodies represents a major impediment to their clinical translation, especially with respect to class-specific immunological functions and safety. Fcε receptor expression and structure are different in humans and mice, so that the murine system is not informative when studying human IgE biology. By contrast, FcεRI expression and cellular distribution in rats mirror that of humans.

METHODS

We are developing MOv18 IgE, a human chimeric antibody recognizing the tumour-associated antigen folate receptor alpha. We created an immunologically congruent surrogate rat model likely to recapitulate human IgE-FcεR interactions and engineered a surrogate rat IgE equivalent to MOv18. Employing this model, we examined in vivo safety and efficacy of antitumour IgE antibodies.

RESULTS

In immunocompetent rats, rodent IgE restricted growth of syngeneic tumours in the absence of clinical, histopathological or metabolic signs associated with obvious toxicity. No physiological or immunological evidence of a "cytokine storm" or allergic response was seen, even at 50 mg/kg weekly doses. IgE treatment was associated with elevated serum concentrations of TNFα, a mediator previously linked with IgE-mediated antitumour and antiparasitic functions, alongside evidence of substantially elevated tumoural immune cell infiltration and immunological pathway activation in tumour-bearing lungs.

CONCLUSION

Our findings indicate safety of MOv18 IgE, in conjunction with efficacy and immune activation, supporting the translation of this therapeutic approach to the clinical arena.

The Monoclonal Antibody-defined CAR-3 Antigen is a Serological Marker Associated with Pancreatic Carcinoma

The monoclonal antibody-defined CARS antigen is a new carcinoma associated marker which is expressed on a mucin-like molecule. Serum concentrations of CARS were assayed in 181 patients with carcinomas of different organs, 20 patients with non-carcinomatous malignancies, 123 patients with inflammatory diseases and 150 healthy controls. Serum levels of CARS were significantly increased in 51% of the patients with pancreatic carcinomas, in 60% of patients with biliary tract carcinomas and in about 15% of the patients with carcinomas of the digestive apparatus. Sera from patients with breast carcinomas were negative, as well as sera from patients with melanomas or sarcomas. CAR-3 values in samples from patients with chronic pancreatitis were constantly negative, as were samples from healthy donors. Significant concentrations of CAR-3 were detected in 20% of the sera from patients with acute pancreatitis and in 15% of the sera from patients with cirrhosis. Because of its high specificity for pancreatic carcinomas compared to chronic pancreatitis, CARS seems a promising marker for distinguishing between neoplastic and chronic inflammatory diseases of the pancreas, whose differential diagnosis is difficult.

One-Carbon Metabolism: Biological Players in Epithelial Ovarian Cancer

Metabolism is deeply involved in cell behavior and homeostasis maintenance, with metabolites acting as molecular intermediates to modulate cellular functions. In particular, one-carbon metabolism is a key biochemical pathway necessary to provide carbon units required for critical processes, including nucleotide biosynthesis, epigenetic methylation, and cell redox-status regulation. It is, therefore, not surprising that alterations in this pathway may acquire fundamental importance in cancer onset and progression. Two of the major actors in one-carbon metabolism, folate and choline, play a key role in the pathobiology of epithelial ovarian cancer (EOC), the deadliest gynecological malignancy. EOC is characterized by a cholinic phenotype sustained via increased activity of choline kinase alpha, and via membrane overexpression of the alpha isoform of the folate receptor (FRα), both of which are known to contribute to generating regulatory signals that support EOC cell aggressiveness and proliferation. Here, we describe in detail the main biological processes associated with one-carbon metabolism, and the current knowledge about its role in EOC. Moreover, since the cholinic phenotype and FRα overexpression are unique properties of tumor cells, but not of normal cells, they can be considered attractive targets for the development of therapeutic approaches.

The emergence of trophoblast cell-surface antigen 2 (TROP-2) as a novel cancer target

TROP-2 is a glycoprotein first described as a surface marker of trophoblast cells, but subsequently shown to be increased in many solid cancers, with lower expression in certain normal tissues. It regulates cancer growth, invasion and spread by several signaling pathways, and has a role in stem cell biology and other diseases. This review summarizes TROP-2's properties, especially in cancer, and particularly its role as a target for antibody-drug conjugates (ADC) or immunotherapy. When the irinotecan metabolite, SN-38, is conjugated to a humanized anti-TROP-2 antibody (sacituzumab govitecan), it shows potent broad anticancer activity in human cancer xenografts and in patients with advanced triple-negative breast, non-small cell and small-cell lung, as well as urothelial cancers.

Production and Characterization of two Monoclonal Antibodies Directed against the Integrin β1 Chain

The production and characterization of two new monoclonal antibodies (MAbs), designated MAR4 and MAR5, raised against the partially purified α5β1 integrin, are described. The reactivity of these 2 MAbs on tumor cell lines indicated that they reacted on all the cells expressing the β1 subunit independently of the α5 expression. Both MAbs were found to immunoprecipitate on 3 cell lines, a protein of 120 KD corresponding to the molecular weight be the β1 chain, in addition to proteins of other MW corresponding to the α subunits differentially expressed by these cells. The cross-competition experiments showed that MAR4 and MAR5 recognize the same epitope. These 2 MAbs seem to be useful reagents for the characterization of the VLA expression in tumor cells.

Immunohistochemical Reactivity of a Monoclonal Antibody Prepared against Human Ovarian Carcinoma on Normal and Pathological Female Genital Tissues

The reactivity profile of the monoclonal antibody (MAb) MOv18, raised against a poorly differentiated ovarian carcinoma specimen, was studied on normal tissues and tumors from the female reproductive system and on the kidney, which like the oviducts, vagina and uterus, also derives from the intermediate mesoderm. The obtained results indicate that MOv18 recognizes an epitope present on the normal epithelium of the oviducts, on 14-week old fetal kidney and, focally, on proximal and distal tubules of normal adult kidney. A strong reactivity was found on ovarian carcinomas, on invasive squamous carcinomas of the cervix and on endometrial carcinomas and hyperplasias. The antigen recognized by MOv18 (CaMOv18) therefore seems to be an epithelial cell marker associated with intermediate mesoderm differentiation, which can be derepressed during the neoplastic transformation of the ovary and the uterus.

MOv18 Monoclonal Antibody in Diagnostic Applications: Capability to Recognize the Histotype of the Original Tumor

Cells from 52 ascitic fluids and 28 abdominopelvic cavity washings, obtained from 46 ovarian cancer patients, 17 patients bearing malignancies of non ovarian sites and 17 patients with non-malignant ovarian diseases, were tested using 2 methods: traditional cytology and monoclonal antibody immunofluorescence. The immunologic test using the MOv18 MAb, raised against ovarian carcinoma, revealed immunoreactive cells in 83 % of the 36 cytologically positive fluids and in one of the 8 negative fluids from ovarian carcinoma patients and in 18% of the 17 fluids from patients with non-malignant ovarian disease. Forty six cytologically positive ascitic fluids from malignant patients were analyzed in order to evaluate the ability of this MAb to identify the histotype of metastatic cells. Ninety-three percent (26/28) of the effusions from non-mucinous ovarian carcinomas contained MOv18-positive cells, whereas no reactive cells were found in cytologically malignant fluids from patients with ovarian tumors of other oncotypes or with carcinomas of non-ovarian origin. The MOv18 reagent, used as an adjuvant in cytological analysis, can help in the identification of the histotype of metastatic cells of unknown origin.

Radioimmunotherapy of Ovarian Cancer

Radioimmunotherapy (RIT) is a new therapeutical approach where radiolabeled monoclonal antibodies (MAb) against tumor-associated antigens are administered to treat tumor lesions. Ovarian cancer is one of the most promising fields for RIT. This paper gives an overview of some biodistribution studies in animal models and in patients with radiolabeled anti-ovarian cancer MAbs, and defines the main criteria which should be considered to plan a clinical trial of RIT in ovarian cancer. As regards the clinical results, the published outcome of various trials and the experience of the National Cancer Institute of Milan are summarized. Even if the number of patients involved in these clinical studies of RIT is too small to provide conclusive indications about its role in the management of ovarian cancer, the preliminary results from qualified groups show its potential in this disease despite the current problems that limit clinical application (above all, the instability of the radiolabeled linkage, the immunogenicity of murine antibodies, the poor absolute tumor radiolabel uptake and the bone marrow toxicity).

In Vitro and In Vivo Activity of IMGN853, an Antibody-Drug Conjugate Targeting Folate Receptor Alpha Linked to DM4, in Biologically Aggressive Endometrial Cancers

Grade 3 endometrioid and uterine serous carcinomas (USC) account for the vast majority of endometrial cancer deaths. The purpose of this study was to determine folic acid receptor alpha (FRα) expression in these biologically aggressive (type II) endometrial cancers and evaluate FRα as a targetable receptor for IMGN853 (mirvetuximab soravtansine). The expression of FRα was evaluated by immunohistochemistry (IHC) and flow cytometry in 90 endometrioid and USC samples. The in vitro cytotoxic activity and bystander effect were studied in primary uterine cancer cell lines expressing differential levels of FRα. In vivo antitumor efficacy of IMGN853 was evaluated in xenograft/patient-derived xenograft (PDX) models. Semiquantitative IHC analysis indicated that 41% of the USC patients overexpress FRα. Further, overexpression of FRα (i.e., 2+) was detected via flow cytometry in 22% (2/9) of primary endometrioid and in 27% (3/11) of primary USC cell lines. Increased cytotoxicity was seen with IMGN853 treatment compared with control in 2+ expressing uterine tumor cell lines. In contrast, tumor cell lines with low FRα showed no difference when exposed to IMGN853 versus control. IMGN853 induced bystander killing of FRα = 0 tumor cells. In an endometrioid xenograft model (END(K)265), harboring 2+ FRα, IMGN853 treatment showed complete resolution of tumors (P < 0.001). Treatment with IMGN853 in the USC PDX model (BIO(K)1), expressing 2+ FRα, induced twofold increase in median survival (P < 0.001). IMGN853 shows impressive antitumor activity in biologically aggressive FRα 2+ uterine cancers. These preclinical data suggest that patients with chemotherapy resistant/recurrent endometrial cancer overexpressing FRα may benefit from this treatment. Mol Cancer Ther; 17(5); 1003-11. ©2018 AACR.

Targeting folate receptor alpha for cancer treatment

Promising targeted treatments and immunotherapy strategies in oncology and advancements in our understanding of molecular pathways that underpin cancer development have reignited interest in the tumor-associated antigen Folate Receptor alpha (FRα). FRα is a glycosylphosphatidylinositol (GPI)-anchored membrane protein. Its overexpression in tumors such as ovarian, breast and lung cancers, low and restricted distribution in normal tissues, alongside emerging insights into tumor-promoting functions and association of expression with patient prognosis, together render FRα an attractive therapeutic target. In this review, we summarize the role of FRα in cancer development, we consider FRα as a potential diagnostic and prognostic tool, and we discuss different targeted treatment approaches with a specific focus on monoclonal antibodies. Renewed attention to FRα may point to novel individualized treatment approaches to improve the clinical management of patient groups that do not adequately benefit from current conventional therapies.

Carbon nanotubes functionalized with folic acid attached via biomimetic peptide linker

AIM

Anchoring folic acid (FA) with a biomimetic peptidic linker resistant to proteolytic degradation to act as a homing device on functionalized carbon nanotubes.

MATERIALS & METHODS

Ethylenediamine was attached to oxidized multiwalled carbon nanotubes (MWNTs) using 4-(4,6-dimethoxy-[1,3,5]triazin-2-yl)-4-methylmorpholinium tetrafluoroborate. FA was coupled with 6-aminohexanoic acid and derivatives of β-alanine, affording four intermediates, which connected to the MWNTs via peptidic linkers of various lengths.

RESULTS

Biomimetic nanomaterials were produced with FA as a homing molecule. The structure and properties of the nanomaterials were analyzed, confirming the versatility of the peptides used as linkers.

CONCLUSION

Conjugates of FA attached to MWNTs via peptide linkers prepared from β-alanine residues are resistant to proteolytic degradation. Viability in colon cancer cells and normal colonocytes confirmed their lack of cytotoxicity.

Modification of cytokine-induced killer cells with folate receptor alpha (FRα)-specific chimeric antigen receptors enhances their antitumor immunity toward FRα-positive ovarian cancers

Folate receptor alpha (FRα) is aberrantly expressed in ovarian cancers but largely absent in normal tissues, and therefore represents an attractive target for immunotherapy. In recent years, modification of T cells with chimeric antigen receptor (CAR) targeting FRα has been reported to improve antitumor immunity of T cells. However, there are limited data regarding CAR-modified cytokine-induced killer (CAR-CIK) cells. In the present study, we modified CIK cells with FRα-specific CARs and investigated their antitumor immunity against ovarian cancers. We found that both non-transduced and mock CAR-transduced CIK cells showed only low antitumor activity against either FRα-positive (FRα⁺) or FRα-negative (FRα^-) targets. However, all three generations of CAR-modified CIK cells showed enhanced antitumor activity against FRα⁺ targets, but not FRα^- targets. First-generation ζ-CAR-CIK cells increased production of IFN-γ, enhanced short-term cytotoxicity against FRα⁺ ovarian cancer cells, and showed modest and short-term suppression of established tumors; while second-generation 28ζ- and third-generation 28BBζ-CAR-CIK cells showed significant proliferation, enhanced secretion of IL-2, eliminated the FRα⁺ ovarian cancer cells in long-term co-culture, and showed dramatic and long-term inhibition of tumor growth and prolonged survival of xenograft-bearing mice. It is noteworthy that the 28BBζ-CAR was more potent in the modification of CIK cells than 28ζ-CAR both in vitro and in vivo. Moreover, CAR-CIK cells showed more efficient anticancer activity compared with CAR-T cells in vitro, but less efficient than CAR-T cells in vivo. According to these results, we conclude that modification of CIK cells with FRα-specific CARs enhances their antitumor immunity to FRα⁺ ovarian cancers. The third-generation 28BB-ζ CAR containing 4-1BB co-stimulation was more efficient in modification of CIK cells than either first-generation ζ-CAR or second-generation CD28-ζ-CAR.

From therapeutic antibodies to chimeric antigen receptors (CARs): making better CARs based on antigen-binding domain

INTRODUCTION

A variety of approaches are being pursued to improve the safety and antitumor potency of chimeric antigen receptor (CAR) T-cell therapy. However, most engineering efforts have thus far been focused on its intracellular signaling domain, while its extracellular antigen-binding domain has received less attention. Areas covered: Herein, the authors summarize the current knowledge of CAR T-cell therapy. Accordingly, they focus on its antigen-binding domain, discuss key considerations for selecting an optimal single-chain variable fragment (scFv) when designing a CAR, and suggest potential directions aimed at developing the next-generation CARs. Expert opinion: The extracellular region of CARs can play a decisive role in their safety and efficacy. Instead of directly translating an available therapeutic mAb to a scFv-based CAR construct, the authors suggest that various CAR-displayed scFvs with different affinity, specificity and binding epitopes against an individual target molecule should be generated and evaluated side-by-side. Incorporating new antibody formats that possess characteristics superior to those of scFvs may be one way to engineer safer and more effective CARs. The authors expect that further CAR engineering will enable us to target more antigens involved in hematological and solid malignancies with minimal side effects to serve unmet clinical needs.

Tumor Regression and Delayed Onset Toxicity Following B7-H4 CAR T Cell Therapy

B7-H4 protein is frequently overexpressed in ovarian cancer. Here, we engineered T cells with novel B7-H4-specific chimeric antigen receptors (CARs) that recognized both human and murine B7-H4 to test the hypothesis that B7-H4 CAR T cell therapy can be applied safely in preclinical models. B7-H4 CAR T cells specifically secreted IFN-γ and lysed B7-H4(+) targets. In vivo, B7-H4 CAR T cells displayed antitumor reactivity against B7-H4(+) human ovarian tumor xenografts. Unexpectedly, B7-H4 CAR T cell treatment reproducibly showed delayed, lethal toxicity 6-8 weeks after therapy. Comprehensive assessment of murine B7-H4 protein distribution uncovered expression in ductal and mucosal epithelial cells in normal tissues. Postmortem analysis revealed the presence of widespread histologic lesions that correlated with B7-H4(+) expression, and were inconsistent with graft versus host disease. Lastly, expression patterns of B7-H4 protein in normal human tissue were comparable to distribution in mice, advancing our understanding of B7-H4. We conclude that B7-H4 CAR therapy mediates control of cancer outgrowth. However, long-term engraftment of B7-H4 CAR T cells mediates lethal, off-tumor toxicity that is likely due to wide expression of B7-H4 in healthy mouse organs. This model system provides a unique opportunity for preclinical evaluation of safety approaches that limit CAR-mediated toxicity after tumor destruction in vivo.

Trop-2 is a novel target for solid cancer therapy with sacituzumab govitecan (IMMU-132), an antibody-drug conjugate (ADC)

Trop-2 is a novel target for ADC therapy because of its high expression by many solid cancers. The rational development of IMMU-132 represents a paradigm shift as an ADC that binds a well-known moderately-cytotoxic drug, SN-38, to the anti-Trop-2 antibody. In vitro and in vivo studies show enhanced efficacy, while there is a gradual release of SN-38 that contributes to the overall effect. IMMU-132 is most efficacious at a high drug:antibody ratio (DAR) of 7.6:1, which does not affect binding and pharmacokinetics. It targets up to 136-fold more SN-38 to a human cancer xenograft than irinotecan, SN-38's prodrug. IMMU-132 delivers SN-38 in its most active, non-glucuronidated form, which may explain the lower frequency of severe diarrhea than with irinotecan. Thus, this ADC, carrying a moderately-toxic drug targeting Trop-2 represents a novel cancer therapeutic that is showing promising activity in patients with several metastatic cancer types, including triple-negative breast cancer, non-small-cell and small-cell lung cancers.

IMGN853, a Folate Receptor-α (FRα)-Targeting Antibody-Drug Conjugate, Exhibits Potent Targeted Antitumor Activity against FRα-Expressing Tumors

A majority of ovarian and non-small cell lung adenocarcinoma cancers overexpress folate receptor α (FRα). Here, we report the development of an anti-FRα antibody-drug conjugate (ADC), consisting of a FRα-binding antibody attached to a highly potent maytansinoid that induces cell-cycle arrest and cell death by targeting microtubules. From screening a large panel of anti-FRα monoclonal antibodies, we selected the humanized antibody M9346A as the best antibody for targeted delivery of a maytansinoid payload into FRα-positive cells. We compared M9346A conjugates with various linker/maytansinoid combinations, and found that a conjugate, now denoted as IMGN853, with the N-succinimidyl 4-(2-pyridyldithio)-2-sulfobutanoate (sulfo-SPDB) linker and N(2')-deacetyl-N(2')-(4-mercapto-4-methyl-1-oxopentyl)-maytansine (DM4) exhibited the most potent antitumor activity in several FRα-expressing xenograft tumor models. The level of expression of FRα on the surface of cells was a major determinant in the sensitivity of tumor cells to the cytotoxic effect of the conjugate. Efficacy studies of IMGN853 in xenografts of ovarian cancer and non-small cell lung cancer cell lines and of a patient tumor-derived xenograft model demonstrated that the ADC was highly active against tumors that expressed FRα at levels similar to those found on a large fraction of ovarian and non-small cell lung cancer patient tumors, as assessed by immunohistochemistry. IMGN853 displayed cytotoxic activity against FRα-negative cells situated near FRα-positive cells (bystander cytotoxic activity), indicating its ability to eradicate tumors with heterogeneous expression of FRα. Together, these findings support the clinical development of IMGN853 as a novel targeted therapy for patients with FRα-expressing tumors.

New perspectives on targeted therapy in ovarian cancer

Epithelial ovarian cancer remains the most lethal gynecologic malignancy. During the last 15 years, there has been only marginal improvement in 5 year overall survival. These daunting statistics are compounded by the fact that despite all subtypes exhibiting striking heterogeneity, their systemic management remains identical. Although changes to the scheduling and administration of chemotherapy have improved outcomes to a degree, a therapeutic ceiling is being reached with this approach, resulting in a number of trials investigating the efficacy of targeted therapies alongside standard treatment algorithms. Furthermore, there is an urge to develop subtype-specific studies in an attempt to improve outcomes, which currently remain poor. This review summarizes the key studies with antiangiogenic agents, poly(adenosine diphosphate [ADP]-ribose) inhibitors, and epidermal growth factor receptor/human epidermal growth factor receptor family targeting, in addition to folate receptor antagonists and insulin growth factor receptor inhibitors. The efficacy of treatment paradigms used in non-ovarian malignancies for type I tumors is also highlighted, in addition to recent advances in appropriate patient stratification for targeted therapies in epithelial ovarian cancer.

Targeted drug delivery via folate receptors in recurrent ovarian cancer: a review

Ovarian cancer is the most common cause of gynecological cancer-related mortality, with the majority of women presenting with advanced disease; although chemotherapeutic advances have improved progression-free survival, conventional treatments offer limited results in terms of long-term responses and survival. Research has recently focused on targeted therapies, which represent a new, promising therapeutic approach, aimed to maximize tumor kill and minimize toxicity. Besides antiangiogenetic agents and poly (ADP-ribose) polymerase inhibitors, the folate, with its membrane-bound receptor, is currently one of the most investigated alternatives. In particular, folate receptor (FR) has been shown to be frequently overexpressed on the surface of almost all epithelial ovarian cancers, making this receptor an excellent tumor-associated antigen. There are two basic strategies to targeting FRs with therapeutic intent: the first is based on anti-FR antibody (ie, farletuzumab) and the second is based on folate–chemotherapy conjugates (ie, vintafolide/etarfolatide). Both strategies have been investigated in Phase III clinical trials. The aim of this review is to analyze the research regarding the activity of these promising anti-FR agents in patients affected by ovarian cancer, including anti-FR antibodies and folate–chemotherapy conjugates.

Targeted treatment of folate receptor-positive platinum-resistant ovarian cancer and companion diagnostics, with specific focus on vintafolide and etarfolatide

Among the gynecological malignancies, ovarian cancer is the leading cause of mortality in developed countries. Treatment of ovarian cancer is based on surgery integrated with chemotherapy. Platinum-based drugs (cisplatin and carboplatin) comprise the core of first-line chemotherapy for patients with advanced ovarian cancer. Platinum-resistant ovarian cancer can be treated with cytotoxic chemotherapeutics such as paclitaxel, topotecan, PEGylated liposomal doxorubicin, or gemcitabine, but many patients eventually relapse on treatment. Targeted therapies based on agents specifically directed to overexpressed receptors, or to selected molecular targets, may be the future of clinical treatment. In this regard, overexpression of folate receptor-α on the surface of almost all epithelial ovarian cancers makes this receptor an excellent "tumor-associated antigen". With appropriate use of spacers/linkers, folate-targeted drugs can be distributed within the body, where they preferentially bind to ovarian cancer cells and are released inside their target cells. Here they can exert their desired cytotoxic function. Based on this strategy, 12 years after it was first described, a folate-targeted vinblastine derivative has now reached Phase III clinical trials in ovarian cancer. This review examines the importance of folate targeting, the state of the art of a vinblastine folate-targeted agent (vintafolide) for treating platinum-resistant ovarian cancer, and its diagnostic companion (etarfolatide) as a prognostic agent. Etarfolatide is a valuable noninvasive diagnostic imaging agent with which to select ovarian cancer patient populations that may benefit from this specific targeted therapy.

Trop-2 protein overexpression is an independent marker for predicting disease recurrence in endometrioid endometrial carcinoma

Background

Endometrial cancer is the most common gynecologic malignancy in developed countries. Trop-2 is a glycoprotein involved in cellular signal transduction and is differentially overexpressed relative to normal tissue in a variety of human adenocarcinomas, including endometrioid endometrial carcinomas (EEC). Trop-2 overexpression has been proposed as a marker for biologically aggressive tumor phenotypes.

Methods

Trop-2 protein expression was quantified using tissue microarrays consisting of formalin-fixed paraffin-embedded specimens from 118 patients who underwent surgical staging from 2001–9 by laparotomy for EEC. Clinicopathologic characteristics including age, stage, grade, lymphovascular space invasion, and medical comorbidities were correlated with immunostaining score. Univariate and multivariate analyses were performed for overall survival, disease-free survival, and progression-free survival in relation to clinical parameters and Trop-2 protein expression.

Results

Clinical outcome data were available for 103 patients. Strong Trop-2 immunostaining was significantly associated with higher tumor grade (p=0.02) and cervical involvement (p<0.01). Univariate analyses showed a significant association with reduced disease-free survival (DFS) (p=0.01), and a trend towards significance for overall and progression-free survival (p=0.06 and p=0.05, respectively). Multivariate analyses revealed Trop-2 overexpression and advanced FIGO stage to be independent prognostic factors for poor DFS (p=0.04 and p <0.001, respectively).

Conclusions

Trop-2 protein overexpression is significantly associated with higher tumor grade and serves as an independent prognostic factor for DFS in endometrioid endometrial cancer.

Co-localisation of advanced glycation end products and D-β-aspartic acid-containing proteins in gelatinous drop-like corneal dystrophy

PURPOSE

Gelatinous drop-like corneal dystrophy (GDLD), also known as familial subepithelial corneal amyloidosis, is an autosomal recessive disorder that causes progressive corneal opacity due to accumulation of amyloid fibrils in the corneal stroma. Genetic analyses have revealed that a mutation in membrane component chromosome 1 surface marker 1 gene is responsible for GDLD. However, the mechanism of amyloid formation in the corneal stroma remains unclear. The present study attempted to reveal the role of advanced glycation end products (AGE) and d-amino acids in amyloid formation in GDLD.

METHODS

Informed consent was obtained from five patients with GDLD, three patients with bullous keratopathy and three patients with interstitial keratitis and all the specimens were analysed. Localisation of amyloid fibrils was analysed using Congo-red and thioflavin T staining. In addition, the localisation of AGE (N(ε)-carboxy(methyl)-L-lysine, pyrraline and pentosidine) and D-β-aspartic acid-containing proteins, a major form of d-amino acid-containing proteins, was analysed immunohistochemically.

RESULTS

In all GDLD specimens, strong immunoreactivity to AGE and D-β-aspartic acid-containing proteins was detected in the subepithelial amyloid-rich region. In contrast, amyloid fibrils, AGE, or D-amino acid-containing proteins were slightly detected in the corneal stroma of patients with bullous keratopathy and interstitial keratitis.

CONCLUSIONS

Abnormally accumulated proteins rich in AGE and D-β-aspartic acid co-localise in the amyloid lesions in GDLD. These results indicate that non-enzymatic post-translational modifications of proteins, including AGE formation and isomerisation of aspartyl residues, will be the cause as well as the result of amyloid fibril formations in GDLD.

Trop-2 overexpression in poorly differentiated endometrial endometrioid carcinoma: implications for immunotherapy with hRS7, a humanized anti-trop-2 monoclonal antibody

OBJECTIVE

We evaluated the expression of human trophoblast cell surface marker (Trop-2) in endometrial endometrioid carcinoma (EEC) and the potential application of hRS7, a humanized monoclonal anti-Trop-2 antibody, as a therapeutic agent against poorly differentiated EEC.

METHODS

Trop-2 expression was evaluated by immunohistochemistry in 131 EEC with different degrees of differentiation and 32 normal endometrial controls (NEC). Trop-2 expression was also evaluated by quantitative real-time polymerase chain reaction and flow cytometry in 3 primary EEC cell lines derived from patients harboring poorly differentiated EEC. Finally, the sensitivity of grade 3 EEC cell lines to hRS7 antibody-dependent cellular cytotoxicity was tested in standard 5-hour Cr release assays.

RESULTS

Trop-2 expression was detected in 126 (96.2%) of 131 EEC samples. Tumor tissues showed markedly increased Trop-2 positivity compared with NEC (P = 0.001). Trop-2 expression was significantly higher in all grades of EEC versus NEC. Grade 3 tumors displayed significantly stronger Trop-2 immunostaining compared with grade 1 EEC (P = 0.01). High Trop-2 expression by quantitative real-time polymerase chain reaction and flow cytometry was found in 1 grade 3 EEC primary cell line (EEC-ARK-1). Unlike Trop-2-negative EEC cell lines, EEC-ARK-1 was found highly sensitive to hRS7-mediated antibody-dependent cellular cytotoxicity in vitro (range of killing, 33.9%-50.6%; P = 0.004). Human serum did not significantly inhibit hRS7-mediated cytotoxicity against EEC-ARK-1 (P = 0.773).

CONCLUSIONS

Trop-2 is highly expressed in EEC, and its expression is significantly higher in poorly differentiated EEC when compared with well-differentiated EEC. Primary grade 3 EECs overexpressing Trop-2 are highly sensitive to hRS7-mediated cytotoxicity in vitro. hRS7 may represent a novel therapeutic agent for the treatment of high-grade EEC refractory to standard treatment modalities.

Cervical carcinomas overexpress human trophoblast cell-surface marker (Trop-2) and are highly sensitive to immunotherapy with hRS7, a humanized monoclonal anti-Trop-2 antibody

OBJECTIVE

We evaluated the expression of human trophoblast cell-surface marker (Trop-2) and the potential of hRS7, a humanized monoclonal anti-Trop-2 antibody, against treatment-refractory cervical cancer.

STUDY DESIGN

Trop-2 expression was evaluated by immunohistochemistry, real-time polymerase chain reaction, and flow cytometry. Sensitivity to hRS7 antibody-dependent cell-mediated cytotoxicity (ADCC) and complement-dependent cytotoxicity was tested in 5-hour chromium release assays. The effect of interleukin (IL)-2 on hRS7 ADCC was also investigated.

RESULTS

Membrane Trop-2 expression was observed in 8 of 8 (100%) of the cancer samples tested by immunohistochemistry, but not in normal cervix. High messenger RNA expression by real-time polymerase chain reaction and high Trop-2 surface expression by flow cytometry were detected in 80% of cervical cancers (4 of 5 cell lines). Although these tumors were resistant to natural killer cell-dependent cytotoxicity in vitro (mean killing, 6.0%), Trop-2-positive cell lines showed high sensitivity to hRS7 ADCC (range of killing, 30.6-73.2%). Incubation with IL-2 further increased the level of cytotoxicity against Trop-2-positive tumors.

CONCLUSION

hRS7 may represent a novel treatment option for patients with cervical cancer refractory to conventional treatment modalities.

CD27 costimulation augments the survival and antitumor activity of redirected human T cells in vivo

The costimulatory effects of CD27 on T lymphocyte effector function and memory formation has been confined to evaluations in mouse models, in vitro human cell culture systems, and clinical observations. Here, we tested whether CD27 costimulation actively enhances human T-cell function, expansion, and survival in vitro and in vivo. Human T cells transduced to express an antigen-specific chimeric antigen receptor (CAR-T) containing an intracellular CD3 zeta (CD3ζ) chain signaling module with the CD27 costimulatory motif in tandem exerted increased antigen-stimulated effector functions in vitro, including cytokine secretion and cytotoxicity, compared with CAR-T with CD3ζ alone. After antigen stimulation in vitro, CD27-bearing CAR-T cells also proliferated, up-regulated Bcl-X(L) protein expression, resisted apoptosis, and underwent increased numerical expansion. The greatest impact of CD27 was noted in vivo, where transferred CAR-T cells with CD27 demonstrated heightened persistence after infusion, facilitating improved regression of human cancer in a xenogeneic allograft model. This tumor regression was similar to that achieved with CD28- or 4-1BB-costimulated CARs, and heightened persistence was similar to 4-1BB but greater than CD28. Thus, CD27 costimulation enhances expansion, effector function, and survival of human CAR-T cells in vitro and augments human T-cell persistence and antitumor activity in vivo.

Antitumor effects of a human dimeric antibody fragment 131I-AFRA-DFM5.3 in a mouse model for ovarian cancer

AFRA-DMF5.3 is a human antibody fragment that, as a dimer, specifically binds to the α-folate receptor (FR) on ovary cancer cells. Pharmacokinetic and biodistribution parameters of (131)I-AFRA-DFM5.3 after intravenous administration in animal models support its potential therapeutic use. We evaluated its preclinical specificity and therapeutic efficacy in tumor models.

METHODS

A negative control, AFRA-DFM6.1, was obtained by protein engineering. The activity and specificity of (131)I-AFRA-DFMs were evaluated by systemic administration (intravenous) in subcutaneous tumor xenograft-bearing nude mice. Pharmacokinetics, biodistribution, and efficacy were assessed by intraperitoneal administration of (131)I-AFRA-DFM5.3 in nude mice bearing 2 different intraperitoneal ovarian carcinoma xenografts. Treatments were tested at different doses and as single or double administrations 1 wk apart.

RESULTS

In subcutaneous models, (131)I-AFRA-DFM5.3, but not the negative control, was found to reside on FR-positive tumor masses and significantly reduced tumor growth. In intraperitoneal models, early accumulation on free-floating clumps of ovarian cancer cells and solid peritoneal masses was evident after 1 h, and tumor uptake was stable for up to 3 h. The high tumor uptake determined the efficacy of (131)I-AFRA-DFM5.3. The best antitumor activity, with more than 50% of treated animals cured, was achieved with 2 locoregional treatments of intraperitoneally growing tumors on days 2 and 9.

CONCLUSION

These results suggest that radioimmunotherapy with (131)I-AFRA-DFM5.3 is feasible and leads to significantly prolonged survival. These preclinical data provide the basis for the rationale design of therapeutic treatments of ovarian cancer patients with a radiolabeled anti-FR antibody fragment.

In vivo persistence, tumor localization, and antitumor activity of CAR-engineered T cells is enhanced by costimulatory signaling through CD137 (4-1BB)

Human T cells engineered to express a chimeric antigen receptor (CAR) specific for folate receptor-α (FRα) have shown robust antitumor activity against epithelial cancers in vitro but not in the clinic because of their inability to persist and home to tumor in vivo. In this study, CARs were constructed containing a FRα-specific scFv (MOv19) coupled to the T-cell receptor CD3ζ chain signaling module alone (MOv19-ζ) or in combination with the CD137 (4-1BB) costimulatory motif in tandem (MOv19-BBζ). Primary human T cells transduced to express conventional MOv19-ζ or costimulated MOv19-BBζ CARs secreted various proinflammatory cytokines, and exerted cytotoxic function when cocultured with FRα(+) tumor cells in vitro. However, only transfer of human T cells expressing the costimulated MOv19-BBζ CAR mediated tumor regression in immunodeficient mice bearing large, established FRα(+) human cancer. MOv19-BBζ CAR T-cell infusion mediated tumor regression in models of metastatic intraperitoneal, subcutaneous, and lung-involved human ovarian cancer. Importantly, tumor response was associated with the selective survival and tumor localization of human T cells in vivo and was only observed in mice receiving costimulated MOv19-BBζ CAR T cells. T-cell persistence and antitumor activity were primarily antigen-driven; however, antigen-independent CD137 signaling by CAR improved T-cell persistence but not antitumor activity in vivo. Our results show that anti-FRα CAR outfitted with CD137 costimulatory signaling in tandem overcome issues of T-cell persistence and tumor localization that limit the conventional FRα T-cell targeting strategy to provide potent antitumor activity in vivo.

Expression of Trop2 cell surface glycoprotein in normal and tumor tissues: potential implications as a cancer therapeutic target

Trop2 is a cell-surface glycoprotein reported to be overexpressed in various types of adenocarcinomas with minimal expression in normal tissues. Recent findings that Trop2 expression correlates with tumor aggressiveness have increased interest in Trop2 as a potential target for cancer immunotherapy. The goal of this study was to extensively evaluate Trop2 expression at the transcript and protein levels in normal and tumor tissues. It was determined that Trop2 is overexpressed on some carcinomas relative to the corresponding normal tissue. However, in human and mouse, Trop2 is highly expressed at both the transcript and protein levels on several essential normal tissues. The findings suggest that the development of therapeutic agents to target Trop2 may require strategies that target Trop2 on malignant tissues in order to minimize potential toxicities to essential normal tissues that also express high levels of Trop2.

High-grade, chemotherapy-resistant primary ovarian carcinoma cell lines overexpress human trophoblast cell-surface marker (Trop-2) and are highly sensitive to immunotherapy with hRS7, a humanized monoclonal anti-Trop-2 antibody

OBJECTIVE

We evaluated the expression of human trophoblast cell-surface marker (Trop-2) and the potential of hRS7, a humanized monoclonal anti-Trop-2 antibody, as a therapeutic agent against chemotherapy-resistant ovarian disease.

METHODS

Trop-2 expression was evaluated by immunohistochemistry (IHC) in 50 ovarian serous papillary carcinoma specimens. Trop-2 expression was also evaluated by real-time PCR (qRT-PCR) and flow cytometry in a total of 6 primary ovarian cancer cell lines derived from patients with chemotherapy-resistant disease. Sensitivity to hRS7 antibody-dependent cellular cytotoxicity (ADCC) was tested in standard 5-hour ⁵¹Cr-release assays. The effect of serum and interleukin-2 (IL-2) on hRS7-mediated ADCC was also studied.

RESULTS

Trop-2 expression was found in 41 of 50 (82%) tumor tissues tested by IHC. 83% (5 of 6) of the ovarian cancer cell lines tested by qRT-PCR and flow cytometry demonstrated high Trop-2 expression. All primary ovarian cancer cell lines expressing Trop-2 were highly sensitive to hRS7-mediated ADCC in vitro (range of killing: 19.3% to 40.8%) (p<0.001). Negligible cytotoxicity against chemotherapy-resistant ovarian cancers was seen in the absence of hRS7 or in the presence of rituximab control antibody (range of killing: 1.1% to 8.9%). Human serum did not significantly inhibit hRS7-mediated cytotoxicity while incubation with IL-2 in addition to hRS7 further increased the cytotoxic activity (p=0.04).

CONCLUSIONS

Trop-2 is highly expressed in chemotherapy-resistant ovarian cancer cell lines at mRNA and protein levels. Primary ovarian carcinoma cell lines are highly sensitive to hRS7-mediated cytotoxicity in vitro. hRS7 may represent a novel therapeutic agent for the treatment of high-grade, chemotherapy-resistant ovarian cancer.

Uterine serous papillary carcinomas overexpress human trophoblast-cell-surface marker (Trop-2) and are highly sensitive to immunotherapy with hRS7, a humanized anti-Trop-2 monoclonal antibody

BACKGROUND

Uterine serous papillary carcinoma (USPC) was an aggressive and chemotherapy resistant variant of endometrial cancer. The authors evaluated the expression of human trophoblast-cell-surface-marker (Trop-2) and the potential of hRS7, a humanized anti-Trop-2 monoclonal antibody, as a novel therapeutic strategy against USPC.

METHODS

Trop-2 expression was evaluated by immunohistochemistry (IHC) in a total of 23 USPC. Six primary USPC cell lines were assessed by flow cytometry and real-time polymerase chain reaction (PCR) for Trop-2 expression. Sensitivity to hRS7 (Immunomedics, Inc.) antibody-dependent cellular cytotoxicity (ADCC) and complement-dependent cytotoxicity was tested in standard 5-hour ⁵¹Cr-release assays against primary USPC cell lines.

RESULTS

Expression of Trop-2 was found in 15 of 23 (65%) of the tumor tissues tested by IHC and in 50% (3 of 6) of the USPC cell lines tested by real-time PCR and flow-cytometry (Trop-2 expression in USPC versus normal endometrial cells; P < .005). USPC cell lines overexpressing Trop-2, regardless of their intrinsic resistance to natural killer cytotoxicity, were highly sensitive to hRS7-mediated ADCC in vitro (range of killing, 28.2% to 64.4%) (P < .001). Negligible cytotoxicity against USPC was seen in the absence of hRS7 or in the presence of rituximab control antibody (range of killing, 1.1% to 12.4%). Incubation with interleukin-2 (50 IU/mL) in addition to hRS7 further increased the cytotoxic activity against USPC cell lines overexpressing Trop-2 (P = .008).

CONCLUSIONS

Trop-2 was highly expressed in uterine serous carcinoma at mRNA and protein levels. Primary USPC cell lines are highly sensitivity to hRS7-mediated cytotoxicity in vitro. hRS7 may represent a novel therapeutic agent for USPC refractory to standard treatment modalities.

Tumor-associated calcium signal transducer 2 is required for the proper subcellular localization of claudin 1 and 7: implications in the pathogenesis of gelatinous drop-like corneal dystrophy

Gelatinous drop-like dystrophy (GDLD) is a rare autosomal recessive form of corneal dystrophy characterized by subepithelial amyloid depositions on the cornea. Previous clinical and laboratory observations have strongly suggested that epithelial barrier function is significantly decreased in GDLD. Despite the decade-old identification of the tumor-associated calcium signal transducer 2 (TACSTD2) gene as a causative gene for GDLD, the mechanism by which the loss of function of this causative gene leads to the pathological consequence of this disease remains unknown. In this study, we investigated the functional relationship between the TACSTD2 gene and epithelial barrier function. Through the use of immunoprecipitation and a proximity ligation assay, we obtained evidence that the TACSTD2 protein directly binds to claudin 1 and 7 proteins. In addition, the loss of function of the TACSTD2 gene leads to decreased expression and change in the subcellular localization of tight junction-related proteins, including claudin 1, 4, 7, and ZO1 and occludin, both in diseased cornea and cultured corneal epithelial cells. These results indicate that loss of function of the TACSTD2 gene impairs epithelial barrier function through decreased expression and altered subcellular localization of tight junction-related proteins in GDLD corneas.

BRCA1 16 years later: risk-associated BRCA1 mutations and their functional implications

Mutations in the tumor suppressor breast cancer susceptibility gene 1 (BRCA1), an important player in the DNA damage response, apoptosis, cell cycle regulation and transcription, confer a significantly elevated lifetime risk for breast and ovarian cancer. Although the loss of wild-type BRCA1 function is an important mechanism by which mutations confer increased cancer risk, multiple studies suggest mutant BRCA1 proteins may confer functions independent of the loss of wild-type BRCA1 through dominant negative inhibition of remaining wild-type BRCA1, or through novel interactions and pathways. These functions impact various cellular processes and have the potential to significantly influence cancer initiation and progression. In this review, we discuss the functional classifications of risk-associated BRCA1 mutations and their molecular, cellular and clinical impact for mutation carriers.