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

Efficacy and Safety of Sacituzumab Govitecan in Patients With Advanced Solid Tumors (TROPiCS-03): Analysis in Patients With Advanced Endometrial Cancer

PURPOSE

Patients with advanced endometrial cancer (EC) who progress on or after platinum-based therapy and immunotherapy have poor prognosis. We report efficacy and safety of sacituzumab govitecan (SG), a trophoblast cell-surface antigen 2 (Trop-2)-directed antibody-drug conjugate, in patients with advanced EC.

METHODS

TROPiCS-03 (ClinicalTrials.gov identifier: NCT03964727) is a multicohort, open-label, phase II basket study in patients with metastatic solid tumors. Eligible patients in the EC cohort received SG 10 mg/kg once on days 1 and 8 every 3 weeks. Primary end point was objective response rate (ORR) by investigator's assessment per RECIST v1.1. Secondary end points included clinical benefit rate (CBR; complete and partial response, and stable disease ≥6 months), duration of response (DOR), and progression-free survival (PFS) per investigator assessment, overall survival, and safety. Trop-2 expression of archival or baseline tumor specimens was analyzed by immunohistochemistry.

RESULTS

At data extraction date, 41 patients were enrolled. Median follow-up was 5.8 months (range, 0.7-19.3); median previous therapies was three (range, 1-6); and 85% of patients received previous chemotherapy and immunotherapy. ORR was 22% (95% CI, 11 to 38); CBR was 32% (95% CI, 18 to 48). Median DOR was 8.8 months (95% CI, 2.8 to not estimable); median PFS was 4.8 months (95% CI, 2.8 to 9.8). Trop-2 exploratory analysis was conducted retrospectively for 39 patients. Tumor Trop-2 protein was highly expressed in EC, showing limited correlation with efficacy. Grade ≥3 treatment-related adverse events (TRAEs) occurred in 73% of patients. Study drug discontinuation due to TRAEs was 5%. Two deaths occurred, deemed unrelated to SG.

CONCLUSION

Findings from TROPiCS-03 showed encouraging efficacy of SG with a manageable toxicity profile in a heavily pretreated population with advanced EC. Safety findings were consistent with the known SG safety profile.

Unsolved Issues in the Integrated Histo-Molecular Classification of Endometrial Carcinoma and Therapeutic Implications

Endometrial carcinoma (EC) is the most frequent gynecological cancer, with an increasing incidence and mortality in recent times. The last decade has represented a true revolution with the development of the integrated histo-molecular classification of EC, which allows for the stratification of patients with morphologically indistinguishable disease into groups with different prognoses. Particularly, the POLE-mutated subgroup exhibits outstanding survival. Nevertheless, the indiscriminate application of molecular classification appears premature. Its prognostic significance has been proven mainly in endometrioid EC, the most common histotype, but it has yet to be convincingly confirmed in the other minor histotypes, which indeed account for a relevant proportion of EC mortality. Moreover, its daily use both requires a mindful pathologist who is able to correctly evaluate and unambiguously report immunohistochemical staining used as a surrogated diagnostic tool and is hampered by the unavailability of POLE mutation analysis. Further molecular characterization of ECs is needed to allow for the identification of better-tailored therapies in different settings, as well as the safe avoidance of surgery for fertility preservation. Hopefully, the numerous ongoing clinical trials in the adjuvant and metastatic settings of EC will likely produce evidence to refine the histo-molecular classification and therapeutic guidelines. Our review aims to retrace the origin and evolution of the molecular classification for EC, reveal its strengths and limitations, show clinical relevance, and uncover the desired future developments.

Comparison of Anti-Trop2 Extracellular Domain Antibodies Generated Against Peptide and Protein Immunogens for Targeting Trop2-Positive Tumour Cells

Trophoblast antigen 2 (Trop2) is a transmembrane glycoprotein upregulated in multiple solid tumours. Trop2-based passive immunotherapies are in clinical trials, while Trop2 targeting CAR-T cell-based therapies are also reported. Information about its T- and B-cell epitopes is needed for it to be pursued as an active immunotherapeutic target. This study focused on identification of immunodominant epitopes in the Trop2 extracellular domain (ECD) that can mount an efficient anti-Trop2 antibody response. In silico analysis using various B-cell epitope prediction tools was carried out to identify linear and conformational B-cell epitopes in the ECD of Trop2. Three linear peptide immunogens were shortlisted and synthesized. Along with linear peptides, truncated Trop2 ECD that possesses combination of linear and conformational epitopes was also selected. Recombinant protein immunogen was produced in 293-F suspension culture system and affinity purified. Antisera against different immunogens were characterized by ELISA and Western blotting. Two anti-peptide antisera detected recombinant and ectopically expressed Trop2 protein; however, they were unable to recognize the endogenous Trop2 protein expressed by cancer cells. Antibodies against truncated Trop2 ECD could bind to the endogenous Trop2 expressed on the surface of cancer cells. In addition to their high avidity, these polyclonal anti-sera against truncated Trop2 protein also mediated antibody-dependent cell-mediated cytotoxicity (ADCC). In summary, our comparative analysis demonstrated the utility of truncated Trop2 ECD as a promising candidate to be pursued as an active immunotherapeutic molecule against Trop2-positive cancer cells.

Value of Antibody Drug Conjugates for Gynecological Cancers: A Modern Appraisal Following Recent FDA Approvals

Antibody drug conjugates (ADCs) are a new class of targeted anti-cancer therapies that combine a monoclonal tumor surface receptor-targeting antibody with a highly cytotoxic molecule payload. They enable delivery of cytotoxic therapy more directly to tumor cells and minimize delivery to healthy tissues. This review summarizes the existing literature about ADC therapies approved for use in gynecologic malignancies, relevant preclinical studies, as well as ongoing clinical trials.

Targeting Trop-2 in cancer: Recent research progress and clinical application

The development of new antitumor drugs depends mainly upon targeting tumor cells precisely. Trophoblast surface antigen 2 (Trop-2) is a type I transmembrane glycoprotein involved in Ca2+ signaling in tumor cells. It is highly expressed in various tumor tissues than in normal tissues and represents a novel and promising molecular target for caner targeted therapy. Up to now, the mechanisms and functions associated with Trop-2 have been extensively studied in a variety of solid tumors. According to these findings, Trop-2 plays an important role in cell proliferation, apoptosis, cell adhesion, epithelial-mesenchymal transition, as well as tumorigenesis and tumor progression. In addition, Trop-2 related drugs are also being developed widely. There are a number of Trop-2 related ADC drugs that have demonstrated potent antitumor activity and are currently been studied, such as Sacituzumab Govitecan (SG) and Datopotamab Deruxtecan (Dato-Dxd). In this study, we reviewed the progress of Trop-2 research in solid tumors. We also sorted out the composition and rationale of Trop-2 related drugs and summarized the related clinical trials. Finally, we discussed the current status of Trop-2 research and expanded our perspectives on its future research directions. Importantly, we found that Trop-2 targeted ADCs have great potential for combination with other antitumor therapies. Trop-2 targeted ADCs can reprogramme tumor microenvironment through multiple signaling pathways, ultimately activating antitumor immunity.

Construction of a novel TROP2/CD3 bispecific antibody with potent antitumor activity and reduced induction of Th1 cytokines

Many cancers, including triple-negative breast cancer, overexpress TROP2 on the surface of tumor cells. TROP2 has become a promising tumor associated antigen for the development of novel antibody-based targeted therapy. Herein, we constructed a novel bispecific antibody with the ability to simultaneously target TROP2 on the tumor surface and bind to CD3 to activate T cells. Given that the excessive production of Th1 cytokines induced by CD3-mediated T-cell overactivation may lead to toxicity in the clinic, we devised a strategy to modify this CD3-induced T cell activation by a two-step reduction in the bispecific antibody binding affinity for CD3 to a level that retained the ability of the bispecific antibody to effectively inhibit tumor growth while greatly reducing the amount of Th1 cytokines secreted by T cells. Thus, we provide insight into the design of T cell engagers that exhibit a promising toxicity profile while retaining inhibitory effects on tumor growth.

Antibody-Drug Conjugates in Gynecologic Cancer

The present article reviews the current evidence for antibody-drug conjugates (ADCs) in gynecologic cancer. ADCs consist of a highly selective monoclonal antibody for a tumor-associated antigen and a potent cytotoxic payload conjugated through a linker. Overall, the toxicity profiles of ADCs are manageable. Ocular toxicity is a known class effect of some ADCs and is managed with prophylactic corticosteroid and vasoconstrictor eye drops as well as dose interruptions/holds and dose modifications. In ovarian cancer, mirvetuximab soravtansine, an ADC targeting alpha-folate receptor (FRα), received US Food and Drug Administration (FDA) accelerated approval in November 2022 after data from the single-arm phase III SORAYA trial. A second ADC targeting FRα, STRO-002, received FDA fast track designation in August 2021. Multiple studies with upifitamab rilsodotin, an ADC comprising a NaPi2B-binding antibody, are underway. In cervical cancer, tisotumab vedotin, an ADC-targeting tissue factor, received FDA accelerated approval in September 2021 after the phase II innovaTV 204 trial. Tisotumab vedotin in combination with chemotherapy and other targeted agents is currently being evaluated. Although there are no currently approved ADCs for endometrial cancer, there are many under active evaluation, including mirvetuximab soravtansine. Trastuzumab-deruxtecan (T-DXd), an ADC targeting human epidermal growth factor receptor 2 (HER2), is currently approved for HER2-positive and HER2-low breast cancer and shows promise in endometrial cancer. Like all anticancer treatments, the decision for a patient to undergo therapy with an ADC is a personal choice that balances the potential benefits with the side effects and requires thorough and compassionate support of their physician and care team and shared decision making.

A literature review of the promising future of TROP2: a potential drug therapy target

Background and Objective

Previous studies have demonstrated that the oncogene trophoblast cell surface antigen 2 (TROP2) has great application prospects as a therapeutic target. However, few literature reviews have systematically summarized and evaluated its role in cancer therapy. This study aims to summarize the molecular structure, functions, signal transduction pathways, and prognostic value of TROP2, and explore therapeutic agents that target TROP2.

Methods

A total of 1,376 published literatures from PubMed and 614 published literatures from EMBASE were retrieved by searching "TROP2" or "Trophoblast cell surface antigen 2". The search was conducted on December 12, 2020, and updated on November 20, 2022. The cBioportal and GEPIA (Gene Expression Profiling Interactive Analysis) databases were used to analyze the expression, mutation, and prognostic value of TROP2 in different types of cancer.

Key Content and Findings

TROP2 is overexpressed in different tumor tissues and plays roles in cell proliferation, invasion, migration, apoptosis, and treatment resistance by binding to or interacting with several molecules. As a therapeutic target, TROP2 is particularly suitable for antibody-based therapies. Monoclonal antibodies, bispecific antibodies, antibody-drug conjugates (ADCs), virus-like particles, and antibody drugs in combination with traditional chemotherapy, immunotherapy, radioimmunotherapy, photoimmunotherapy, and nanoparticles that target TROP2 have thus far been rapidly developed. For example, sacituzumab govitecan (IMMU-132), a TROP2-targeting ADC, was granted accelerated approval for the treatment of metastatic triple-negative breast cancer (TNBC). Anti-TROP2 antibody-conjugated nanoparticles (ST-NPs) are a promising vehicle for delivering doxorubicin in targeted TNBC therapy.

Conclusions

The availability of TROP2-targeting ADCs makes TROP2 an accessible and promising therapeutic target for advanced metastatic cancers. The present review describes the important role of TROP2 in tumorigenesis and its potential applications as a promising biomarker and therapeutic target that is capable of reversing resistance.

CAR T cells equipped with a fully human scFv targeting Trop2 can be used to treat pancreatic cancer

PURPOSE

Chimeric antigen receptor (CAR) T cell therapy has demonstrated clinical success in treating haematologic malignancies but has not been effective against solid tumours thus far. Trop2 is a tumour-related antigen broadly overexpressed on a variety of tumours and has been reported as a promising target for pancreatic cancers. Our study aimed to determine whether CAR T cells designed with a fully human Trop2-specific single-chain fragment variable (scFv) can be used in the treatment of Trop2-positive pancreatic tumours.

METHODS

We designed Trop2-targeted chimeric antigen receptor engineered T cells with a novel human anti-Trop2 scFv (2F11) and then investigated the cytotoxicity, degranulation, and cytokine secretion profiles of the anti-Trop2 CAR T cells when they were exposed to Trop2 + cancer cells in vitro. We also studied the antitumour efficacy and toxicity of Trop2-specific CAR T cells in vivo using a BxPC-3 pancreatic xenograft model.

RESULTS

Trop2-targeted CAR T cells designed with 2F11 effectively killed Trop2-positive pancreatic cancer cells and produced high levels of cytotoxic cytokines in vitro. In addition, Trop2-targeted CAR T cells, which persistently circulate in vivo and efficiently infiltrate into tumour tissues, significantly blocked and even eliminated BxPC-3 pancreatic xenograft tumour growth without obvious deleterious effects observed after intravenous injection into NSG mice. Moreover, disease-free survival was efficiently prolonged.

CONCLUSION

These results show that Trop2-targeted CAR T cells equipped with a fully human anti-Trop2 scFv could be a potential treatment strategy for pancreatic cancer and could be useful for clinical evaluation.

Recent advances in trophoblast cell-surface antigen 2 targeted therapy for solid tumors

Trophoblast cell-surface antigen 2 (Trop 2) is a transmembrane glycoprotein that is highly expressed in various cancer types with relatively low or no baseline expression in most normal tissues. Its overexpression is associated with tumor growth and poor prognosis; Trop 2 is, therefore, an ideal therapeutic target for epithelial cancers. Several Trop 2 targeted therapeutics have recently been developed for the treatment of cancers, such as anti-Trop 2 antibodies and antibody-drug conjugates (ADCs), as well as Trop 2-specific cell therapy. In particular, the safety and clinical benefit of Trop 2-based ADCs have been demonstrated in clinical trials across multiple tumor types, including those with limited treatment options, such as triple-negative breast cancer, platinum-resistant urothelial cancer, and heavily pretreated non-small cell lung cancer. In this review, we elaborate on recent advances in Trop 2 targeted modalities and provide an overview of novel insights for future developments in this field.

Can TROP2 be used as a prognostic marker in endometrioid endometrial carcinoma?

Background

Endometrioid-type endometrial carcinoma is the most common malignancy of the female genital tract in developed countries. The prognosis greatly depends on the grade and stage of the disease.

Aims

In some patients, the disease recurs in a short time after the surgical/medical therapy. Hence, it is important to predict the patients who will have worse prognosis at the beginning, to choose the appropriate treatment; resuming the search of new prognostic markers. Therefore, our study aimed to detect trophoblast cell surface antigen 2 (TROP2) as a new prognostic marker.

Settings and Design

The patients who underwent a hysterectomy and diagnosed with endometrioid-type endometrial carcinoma were evaluated retrospectively and TROP2 immunostain was performed to their tumoral slides.

Materials and Methods

We evaluated TROP2 expressions in 102 patients immunohistochemically who underwent hysterectomy with the diagnosis of endometrioid-type endometrial carcinoma histopathologically and correlated them with the other generally accepted prognostic parameters.

Statistical Analysis

The Kolmogorov-Smirnov test and Q-Q plot test were used to verify the normality of the distribution of continuous variables. The Chi-square/Fisher's exact tests were used for categorical variables. Analyses were performed with SPSS Statistics for Windows, Version 20.

Results

High overexpression of TROP2 was seen in larger, higher-grade, deeper-invasive tumors, tumors with vascular invasion, and pelvic-lymph-node metastasis. These results were statistically significant (P ≤ 0.05).

Conclusion

Overexpression of TROP2 in endometrioid-type endometrial carcinoma seems to be a poor prognostic factor; it may be useful in determining the biologically more aggressive tumors before the treatment. This early determination is very important to choose the appropriate surgery, adjuvant-treatments, and follow-up.

Characterizing the Invasive Tumor Front of Aggressive Uterine Adenocarcinoma and Leiomyosarcoma

The invasive tumor front (the tumor–host interface) is vitally important in malignant cell progression and metastasis. Tumor cell interactions with resident and infiltrating host cells and with the surrounding extracellular matrix and secreted factors ultimately determine the fate of the tumor. Herein we focus on the invasive tumor front, making an in-depth characterization of reticular fiber scaffolding, infiltrating immune cells, gene expression, and epigenetic profiles of classified aggressive primary uterine adenocarcinomas (24 patients) and leiomyosarcomas (11 patients). Sections of formalin-fixed samples before and after microdissection were scanned and studied. Reticular fiber architecture and immune cell infiltration were analyzed by automatized algorithms in colocalized regions of interest. Despite morphometric resemblance between reticular fibers and high presence of macrophages, we found some variance in other immune cell populations and distinctive gene expression and cell adhesion-related methylation signatures. Although no evident overall differences in immune response were detected at the gene expression and methylation level, impaired antimicrobial humoral response might be involved in uterine leiomyosarcoma spread. Similarities found at the invasive tumor front of uterine adenocarcinomas and leiomyosarcomas could facilitate the use of common biomarkers and therapies. Furthermore, molecular and architectural characterization of the invasive front of uterine malignancies may provide additional prognostic information beyond established prognostic factors.

Trop2: Jack of All Trades, Master of None

Trophoblast cell surface antigen 2 (Trop2) is a widely expressed glycoprotein and an epithelial cell adhesion molecule (EpCAM) family member. Although initially identified as a transmembrane protein, other subcellular localizations and processed forms were described. Its congenital mutations cause a gelatinous drop-like corneal dystrophy, a disease characterized by loss of barrier function in corneal epithelial cells. Trop2 is considered a stem cell marker and its expression associates with regenerative capacity in various tissues. Trop2 overexpression was described in tumors of different origins; however, functional studies revealed both oncogenic and tumor suppressor roles. Nevertheless, therapeutic potential of Trop2 was recognized and clinical studies with drug-antibody conjugates have been initiated in various cancer types. One of these agents, sacituzumab govitecan, has been recently granted an accelerated approval for therapy of metastatic triple-negative breast cancer. In this article, we review the current knowledge about the yet controversial function of Trop2 in homeostasis and pathology.

Sacituzumab govitecan, a novel, third-generation, antibody-drug conjugate (ADC) for cancer therapy

INTRODUCTION

We describe a new, third-generation of antibody-drug conjugates (ADCs) having a high drug payload against topoisomerase I, important for DNA function, and targeting selective tumor antigens, predominantly TROP-2.

AREAS COVERED

The historical development of ADCs is reviewed before presenting the current line of improved, third-generation ADCs targeting topoisomerase I, thus affecting DNA and causing double-stranded DNA breaks. Emphasis is given to explaining why sacituzumab govitecan represents a paradigm change in ADCs by achieving a high therapeutic index due to its novel target, TROP-2, an internalizing antigen/antibody, proprietary linker chemistry, and high drug payload, resulting in a high tumor concentration of the drug given in repeated doses with acceptable tolerability, particularly evidencing a lower percentage of 'late' diarrhea than its prodrug, irinotecan. PubMed was used for the primary search conducted.

EXPERT OPINION

The properties and clinical results of third-generation ADCs, based on sacituzumab govitecan, are discussed, including prospects for future applications, particularly combination therapies with PARP inhibitors and immune checkpoint inhibitors. Since one topoisomerase I ADC has just received regulatory approval for HER2⁺ breast cancer, and sacituzumab govitecan is under FDA review for accelerated approval in the therapy of triple-negative breast cancer, the prospects for these novel ADCs are discussed.

Preclinical activity of sacituzumab govitecan (IMMU-132) in uterine and ovarian carcinosarcomas

Background

Uterine and ovarian carcinosarcomas (CS) are rare cancers with poor prognosis. Sacituzumab-govitecan (SG) is a new class of antibody-drug-conjugate (ADC) targeting the human-trophoblast-cell-surface marker (Trop-2) conjugated with the active metabolite of irinotecan (SN-38). We evaluated the efficacy of SG against biologically aggressive CS.

Methods

Trop-2 expression was evaluated in 10 formalin-fixed-paraffined-embedded (FFPE) CS by immunohistochemistry and 9 primary CS cell-lines by flow-cytometry. One Trop-2 low/negative (SARARK14) and two Trop-2 positive (SARARK4, SARARK9) cell-lines were tested in cell-viability assays . The in vivo antitumor activity of SG was tested in xenografts models (ie, SARARK9) with strong Trop-2 expression.

Results

Strong/diffuse staining was seen in 30% (3/10) of FFPE tumors and 33% (3/9) of primary CS cell lines. Trop-2 positive cell-lines (SARARK4, SARARK9) showed higher sensitivity to SG in vitro when compared to Trop-2 low/negative (SARARK14) cell lines. In xenografts, twice-weekly intravenous administration of SG for three weeks showed a significant tumor growth inhibition when compared to control, to ADC control and to the naked AB (p=0.004, p=0.007 and p=0.0007, respectively). SG significantly improved overall survival at 90 days when compared to control groups (p<0.0001).

Conclusion

SG may represent a novel class of active drugs for carcinosarcomas patients overexpressing Trop-2.

In vitro and in vivo activity of sacituzumab govitecan, an antibody-drug conjugate targeting trophoblast cell-surface antigen 2 (Trop-2) in uterine serous carcinoma

OBJECTIVE

Uterine serous carcinoma (USC) is an aggressive variant of endometrial cancer with poor prognosis. Sacituzumab govitecan (SG) is a novel antibody-drug-conjugate (ADC) targeting trophoblast cell-surface antigen 2 (Trop-2), a transmembrane-calcium-signal-transducer, to deliver SN-38, the active metabolite of irinotecan. The objective of this study was to evaluate the expression of Trop-2 in USC and the preclinical activity of SG against primary USC cell-lines and xenografts.

METHODS

We used immunohistochemistry (IHC) and flow-cytometry-based assays to evaluate Trop-2 expression and cell-viability in USC tissue and primary tumor-cell-lines after exposure to SG, non-targeting control ADC, and naked antibody hRS7-IgG. Antibody-dependent-cell-cytotoxicity (ADCC) against Trop-2+ and Trop-2- USC cell-lines was evaluated in vitro using 4-hr-Chromium-release-assays. In vivo activity of SG was tested against Trop-2+ USC xenografts by intravenous administration of SG, control ADC, and hRS7.

RESULTS

Trop-2 expression by IHC was detected in 95.1% of USC samples (99/104). Primary tumor cell-lines overexpressing Trop-2 were significantly more sensitive to SG when compared to control ADC (p <0.05). Both SG and hRS7 mediated ADCC in Trop2+ USC cell-lines while no cytotoxicity was detected against Trop-2- cells. SG induced significant bystander killing of Trop-2- tumors when admixed with Trop-2+ tumors. SG caused growth-inhibition and increased survival in SG treated mice harboring Trop-2+ xenografts when compared to controls (p <0.05).

CONCLUSIONS

SG is remarkably active against USC overexpressing Trop-2 in vitro and in vivo. Our results combined with SG clinical responses recently reported against multiple chemotherapy resistant human tumors further support clinical development of SG in USC patients with advanced/recurrent disease.

Antibody-drug conjugates targeting TROP-2 and incorporating SN-38: A case study of anti-TROP-2 sacituzumab govitecan

Antibody-drug conjugates (ADCs) that exploit the active metabolite SN-38, which is derived from the popular anticancer drug, irinotecan (a camptothecin that inhibits the nuclear topoisomerase I enzyme, inducing double-stranded DNA breaks during the mitotic S-phase of affected cells), represent a substantial advance in the ADC field. SN-38 has been conjugated to a humanized antibody against trophoblast cell surface antigen 2 (TROP-2), which is involved in cancer signaling pathways and has increased expression by many cancer cell types, yielding the ADC sacituzumab govitecan. By conjugating a higher number of SN-38 molecules to the immunoglobulin (drug-to-antibody ratio = 7-8:1), and giving higher (10 mg/kg) and repeated therapy cycles (Days 1 and 8 of 21-day cycles), enhanced drug uptake by the targeted cancer cells is achieved. Based on a unique conjugation method, the lactone ring of the SN-38 molecule is stabilized and the molecule is protected from glucuronidation, a process that contributes to the untoward late diarrhea experienced with irinotecan. Finally, while the ADC is internalized, the use of a moderately stable linker permits release of SN-38 in an acidic environment of the tumor cell and its microenvironment, contributing to a bystander effect on neighboring cancer cells. Here, we discuss the development of sacituzumab govitecan and clinical results obtained using it for the management of patients with advanced, refractive breast, lung, and urinary bladder cancers. Sacituzumab govitecan, which is undergoing accelerated approval review by the US Food and Drug Administration while also being studied in Phase 3 clinical studies, was granted Breakthrough Therapy status from the FDA for advanced, refractory, metastatic triple-negative breast cancer patients.

A novel human monoclonal Trop2-IgG antibody inhibits ovarian cancer growth in vitro and in vivo

Trop2 is a tumor-related antigen closely related to the development of a variety of tumors and has been identified as a promising target for cancer immunotherapy. In this study, a Trop2-IgG antibody was constructed by a eukaryotic expression system based on our previously constructed Trop2-Fab antibody. SDS-PAGE, cell ELISA, affinity assays, fluorescence staining and FACS analyses were performed to characterize Trop2-IgG. Then, CCK-8, wound healing, Transwell and annexin V-PI assays were employed to evaluate the tumor inhibitory effects of Trop2-IgG on OC in vitro, while tumor-bearing mice were constructed to examine the tumor inhibitory effects of Trop2-IgG on OC in vivo. Trop2-IgG was successfully constructed by a eukaryotic expression system and maintained recognition characteristics to Trop2 antigen. In vitro, Trop2-IgG could inhibited tumor cell growth, migration, and invasion compared to those of control cells and induced tumor cell apoptosis. In vivo, Trop2-IgG exerted critical tumor inhibitory effects in OC xenografts. Our data suggest that the use of Trop2-IgG provides a potential therapeutic strategy for the immunotherapy of Trop2-expressing OC.

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.

Sacituzumab Govitecan (IMMU-132) in treatment-resistant uterine serous carcinoma: A case report

Background

Uterine serous carcinoma (USC) is a biologically aggressive variant of uterine cancer. Effective treatment options for recurrent, chemotherapy-resistant USC are extremely limited.

Case

We describe a 74-year-old woman with recurrent and widespread treatment-resistant disease, who experienced a dramatic response to sacituzumab govitecan, a novel antibody-drug conjugate (ADC) targeting human trophoblast-cell-surface antigen (TROP-2), after failing multiple chemotherapy and immunotherapy. The impressive clinical response (66% reduction of target lesions by RECIST 1.1 with a duration response of over 10 months) was confirmed with serial CT scans in the absence of significant adverse events.

Conclusion

Sacituzumab govitecan may present a new treatment option for recurrent USC patients harboring Trop-2+ tumors resistant to chemotherapy. Clinical trials with sacituzumab govitecan are warranted.

•

Uterine serous carcinoma (USC) is a rare but aggressive variant of uterine cancer.

•

Sacituzumab-govitecan (IMMU-132) is an antibody-drug conjugate targeting TROP-2.

•

IMMU-132 may represent a new treatment option for USC overexpressing TROP-2.

The Potential Diagnostic Utility of TROP-2 in Thyroid Neoplasms

Objectives:

Human trophoblast cell-surface marker (TROP-2) has been reported to be overexpressed in various human carcinomas (CAs) and suggested to be a prognostic marker for some CAs. The diagnostic utility of TROP-2 in CAs has not been explored.

Methods:

Immunohistochemical evaluation of TROP-2 expression on tissue microarray sections of 136 thyroid neoplasms, surgical specimens of 61 atypical thyroid follicular-patterned lesions [including 33 papillary thyroid carcinomas (PTCs), 17 atypical follicular neoplasms (AFNs), and 11 adenomatoid nodules with focal nuclear atypia (ANFNA)], and 20 benign thyroid lesions, as well as 10 cytology specimens of PTCs was performed. For comparison, immunoassay for Hector Battifora mesothelial-1 (HBME-1), galectin-3, and cytokeratin 19 was performed on the 61 atypical thyroid follicular-patterned lesions.

Results:

Strong membranous staining with TROP-2 was seen in 94% (33/35) of classic PTCs and 81% (30/37) of confirmed follicular variant PTCs on tissue microarray and routine surgical sections, as well as 100% (10/10) of PTCs on cytology specimens; it was not observed in follicular adenomas (n=51) or CAs (n=37), AFNs or ANFNA (n=28), benign (n=20) or normal (n=15) thyroid tissue. In contrast, the expression of HBME-1 and galectin-3 was identified in 100% (33/33) of surgical cases of PTCs and in 57% (16/28) and 50% (14/28) of AFNs and ANFNA, respectively.

Conclusions:

Our findings demonstrate that a membranous TROP-2 staining pattern is highly specific for PTC, which may serve as a potential diagnostic marker aiding in the accurate classification of morphologically equivocal thyroid follicular-patterned lesions.

Overexpression of TROP2 promotes proliferation and invasion of ovarian cancer cells

Human trophoblastic cell-surface marker, tumor-associated calcium signal transducer 2 (TROP2), is a newly identified marker that has a vital role in the proliferation and invasion of various tumors. However, its specific function in ovarian cancer has not been researched. The purpose of the present study was to investigate the role of TROP2 in the formation of ovarian cancer and its possible mechanism. TROP2 was knocked down by small interfering (si)RNA in ovarian cancer cell line, A2780. The expression of TROP2 protein following transfection was detected by western blot analysis. Cell viability was determined using a Cell Counting kit-8. Cancer cell migration and invasion were examined by wound healing and cell invasion assays, respectively. Apoptosis-related proteins, such as B-cell lymphoma 2 (Bcl-2) and Bcl-2-associated X protein (Bax), were measured by western blotting. Results demonstrated that the expression levels of TROP2 were markedly downregulated by siRNA in A2780 cells compared with the control groups, which led to strong inhibition of proliferation and invasion. Furthermore, TROP2 downregulation also reduced cell migratory ability. Additionally, in the TROP2-knockout group, Bcl-2 was downregulated and Bax was upregulated compared with the control. The present study suggested that the expression of TROP2 was related to cellular proliferation, migration and invasion. TROP2 may disrupt the balance in the Bax family to participate in apoptosis regulation in A2780 cells. Therefore, the overexpression of TROP2 may have a crucial role in tumorigenesis and tumor progression by disturbing the Bax/Bcl-2 balance in ovarian cancer.

Sacituzumab Govitecan (IMMU-132), an Anti-Trop-2/SN-38 Antibody-Drug Conjugate: Characterization and Efficacy in Pancreatic, Gastric, and Other Cancers

Sacituzumab govitecan (IMMU-132) is an antibody-drug conjugate (ADC) made from a humanized anti-Trop-2 monoclonal antibody (hRS7) conjugated with the active metabolite of irinotecan, SN-38. In addition to its further characterization, as the clinical utility of IMMU-132 expands to an ever-widening range of Trop-2-expressing solid tumor types, its efficacy in new disease models needs to be explored in a nonclinical setting. Unlike most ADCs that use ultratoxic drugs and stable linkers, IMMU-132 uses a moderately toxic drug with a moderately stable carbonate bond between SN-38 and the linker. Flow cytometry and immunohistochemistry disclosed that Trop-2 is expressed in a wide range of tumor types, including gastric, pancreatic, triple-negative breast (TNBC), colonic, prostate, and lung. While cell-binding experiments reveal no significant differences between IMMU-132 and parental hRS7 antibody, surface plasmon resonance analysis using a Trop-2 CM5 chip shows a significant binding advantage for IMMU-132 over hRS7. The conjugate retained binding to the neonatal receptor, but it lost greater than 60% of the antibody-dependent cell-mediated cytotoxicity activity compared to that of hRS7. Exposure of tumor cells to either free SN-38 or IMMU-132 demonstrated the same signaling pathways, with pJNK1/2 and p21(WAF1/Cip1) upregulation followed by cleavage of caspases 9, 7, and 3, ultimately leading to poly-ADP-ribose polymerase cleavage and double-stranded DNA breaks. Pharmacokinetics of the intact ADC in mice reveals a mean residence time (MRT) of 15.4 h, while the carrier hRS7 antibody cleared at a similar rate as that of the unconjugated antibody (MRT ∼ 300 h). IMMU-132 treatment of mice bearing human gastric cancer xenografts (17.5 mg/kg; twice weekly × 4 weeks) resulted in significant antitumor effects compared to that of mice treated with a nonspecific control. Clinically relevant dosing schemes of IMMU-132 administered either every other week, weekly, or twice weekly in mice bearing human pancreatic or gastric cancer xenografts demonstrate similar, significant antitumor effects in both models. Current Phase I/II clinical trials ( ClinicalTrials.gov , NCT01631552) confirm anticancer activity of IMMU-132 in cancers expressing Trop-2, including gastric and pancreatic cancer patients.

Trop2: from development to disease

BACKGROUND

Trop2 was first discovered as a biomarker of invasive trophoblast cells. Since then most research has focused on its role in tumourigenesis because it is highly expressed in the vast majority of human tumours and animal models of cancer. It is also highly expressed in stem cells and in many organs during development.

RESULTS

We review the multifaceted role of Trop2 during development and tumourigenesis, including its role in regulating cell proliferation and migration, self-renewal, and maintenance of basement membrane integrity. We discuss the evolution of Trop2 and its related protein Epcam (Trop1), including their distinct roles. Mutation of Trop2 leads to gelatinous drop-like corneal dystrophy, whereas over-expression of Trop2 in human tumours promotes tumour aggressiveness and increases mortality. Although Trop2 expression is sufficient to promote tumour growth, the surprising discovery that Trop2-null mice have an increased risk of tumour development has highlighted the complexity of Trop2 signaling. Recently, studies have begun to identify the mechanisms underlying TROP2’s functions, including regulated intramembrane proteolysis or specific interactions with integrin b1 and claudin proteins.

CONCLUSIONS

Understanding the mechanisms underlying TROP2 signaling will clarify its role during development, aid in the development of better cancer treatments and unlock a promising new direction in regenerative medicine.

Expression of tumor-associated calcium signal transducer 2 in patients with salivary adenoid cystic carcinoma: Correlation with clinicopathological features and prognosis

Salivary adenoid cystic carcinoma (SACC) is a common salivary malignancy. The current treatment option for SACC is complete surgical excision with postoperative radiotherapy. The prognosis remains unsatisfactory, due to frequent local recurrence and distant metastases that directly reduce the overall survival time. Previous studies have shown that overexpression of tumor-associated calcium signal transducer 2 (TACSTD2) is associated with poor prognosis in various human epithelial cancers. The expression of TACSTD2 in SACC is currently unknown. The present study therefore aimed to retrospectively investigate TACSTD2 protein expression by immunohistochemistry on paraffin-embedded primary tumor tissue samples from a series of consecutive SACC patients (n=81). The correlation of TACSTD2 expression with clinicopathological variables was evaluated using either the Kruskal-Wallis or Mann-Whitney statistical tests. The survival curves were plotted using the Kaplan-Meier method. The parameters of prognostic significance found by univariate analysis were verified in a multivariate Cox regression model. Overexpression of TACSTD2 was detected in 35/81 (44%) SACC patients and was significantly associated with a decreased overall survival (P<0.01). Univariate analysis showed that TACSTD2 overexpression was correlated with TNM stage (P=0.020), local recurrence (P=0.002) and distant metastasis (P=0.001). Multivariate analyses further revealed that TACSTD2 may be an independent prognostic indicator. In conclusion, TACTSD2 could be recognized as an independent prognostic indicator for SACC. Gene therapy targeting TACSTD2 may be a possible treatment approach for patients with SACC overexpressing this cell-surface marker.

Trop2 gene: a novel target for cervical cancer treatment

OBJECT

Trop2 plays an important role in proliferation and invasion of tumors. Extensive research has shown that the expression level of Trop2 is closely related to the progress of cervical diseases. This study was to explore the effects of Trop2 on cell proliferation and apoptosis in cervical cancer.

METHODS

Trop2 was knocked down by shRNA in CaSki cells. The expression level of mRNA and protein was detected by real-time PCR and western blot, respectively. Cell proliferation was determined by CCK-8 and clone formation assay; apoptosis was measured by flow cytometry; cell cycle and apoptosis-related proteins cyclinD1, P53, bcl-2, bax, caspase 3, 8 and 9 were analyzed as well to investigate possible mechanism.

RESULTS

Trop2 expression was effectively repressed in CaSki cells by Trop2 shRNA, which resulted in inhibition of proliferation and colony formation, whereas apoptosis rate was significantly increased. Furthermore, in Trop2 knockdown CaSki cells, the expression of cyclinD1 and bcl-2 was significantly down-regulated, while that of P53 and bax was up-regulated accompanied by increased activities of caspase 9 and 3 but not caspase 8.

CONCLUSIONS

Trop2 is important in proliferation and apoptosis regulation in CaSki cells, which may become a novel target for cervical cancer treatment.

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.