Tumor vascular homing endgolin-targeted radioimmunotherapy in hepatocellular carcinoma

Novel antigens for targeted radioimmunotherapy in hepatocellular carcinoma

Liver cancer is the sixth common cancer and forth cause of cancer-related death worldwide. Based on usually advanced stages of hepatocellular carcinoma (HCC) at the time of diagnosis, therapeutic options are limited and, in many cases, not effective, and typically result in the tumor recurrence with a poor prognosis. Radioimmunotherapy (RIT) offers a selective internal radiation therapy approach using beta or alpha emitting radionuclides conjugated with tumor-specific monoclonal antibodies (mAbs), or specific selective peptides. When compared to chemotherapy or radiotherapy, radiolabeled mAbs against cancer-associated antigens could provide a high therapeutic and exclusive radiation dose for cancerous cells while decreasing the exposure-induced side effects to healthy tissues. The recent advances in cancer immunotherapy, such as blockade of immune-checkpoint inhibitors (ICIs), has changed the landscape of cancer therapy, and the efficacy of different classes of immunotherapy has been tested in many clinical trials. Taking into account the use of ICIs in the liver tumor microenvironment, combined therapies with different approaches may enhance the outcome in the future clinical studies. With the development of novel immunotherapy treatment options in the recent years, there has been a great deal of information about combining the diverse treatment modalities to boost the effectiveness of immunomodulatory drugs. In this opinion review, we will discuss the recent advancements in RIT. The current status of immunotherapy and internal radiotherapy will be updated, and we will propose novel approaches for the combination of both techniques. Potential target antigens for radioimmunotherapy in Hepatocellular carcinoma (HCC). HCC radioimmunotherapy target antigens are the most specific and commonly accessible antigens on the surface of HCC cells. CTLA-4 ligand and receptor, TAMs, PD-1/PD-L, TIM-3, specific IEXs/TEXs, ROBO1, and cluster of differentiation antigens CD105, CD147 could all be used in HCC radioimmunotherapy. Abbreviations: TAMs, tumor-associated macrophages; CTLA-4, cytotoxic T-lymphocyte associated antigen-4; PD-1, Programmed cell death protein 1; PD-L, programmed death-ligand1; TIM-3, T-cell immunoglobulin (Ig) and mucin-domain containing protein-3; IEXs, immune cell-derived exosomes; TEXs, tumor-derived exosomes.

The Role of Endoglin in Hepatocellular Carcinoma

Endoglin (CD105) is a type-1 integral transmembrane glycoprotein and coreceptor for transforming growth factor-β (TGF-β) ligands. The endoglin/TGF-β signaling pathway regulates hemostasis, cell proliferation/migration, extracellular matrix (ECM) synthesis and angiogenesis. Angiogenesis contributes to early progression, invasion, postoperative recurrence, and metastasis in hepatocellular carcinoma (HCC), one of the most widespread malignancies globally. Endoglin is overexpressed in newly formed HCC microvessels. It increases microvessel density in cirrhotic and regenerative HCC nodules. In addition, circulating endoglin is present in HCC patients, suggesting potential for use as a diagnostic or prognostic factor. HCC angiogenesis is dynamic and endoglin expression varies by stage. TRC105 (carotuximab) is an antibody against endoglin, and three of its clinical trials were related to liver diseases. A partial response was achieved when combining TRC105 with sorafenib. Although antiangiogenic therapy still carries some risks, combination therapy with endoglin inhibitors or other targeted therapies holds promise.

Role of Endoglin (CD105) in the Progression of Hepatocellular Carcinoma and Anti-Angiogenic Therapy

The liver is perfused by both arterial and venous blood, with a resulting abnormal microenvironment selecting for more-aggressive malignancies. Hepatocellular carcinoma (HCC) is the most frequent primary liver cancer, the sixth most common cancer globally, and the third leading cause of cancer-related mortality worldwide. HCC is characterized by its hypervascularization. Improving the efficiency of anti-angiogenic treatment and mitigation of anti-angiogenic drug resistance are the top priorities in the development of non-surgical HCC therapies. Endoglin (CD105), a transmembrane glycoprotein, is one of the transforming growth factor β (TGF-β) co-receptors. Involvement of that protein in angiogenesis of solid tumours is well documented. Endoglin is a marker of activated endothelial cells (ECs), and is preferentially expressed in the angiogenic endothelium of solid tumours, including HCC. HCC is associated with changes in CD105-positive ECs within and around the tumour. The large spectrum of endoglin effects in the liver is cell-type- and HCC- stage-specific. High expression of endoglin in non-tumour tissue suggests that this microenvironment might play an especially important role in the progression of HCC. Evaluation of tissue expression, as well as serum concentrations of this glycoprotein in HCC, tends to confirm its role as an important biomarker in HCC diagnosis and prognosis. The role of endoglin in liver fibrosis and HCC progression also makes it an attractive therapeutic target. Despite these facts, the exact molecular mechanisms of endoglin functioning in hepatocarcinogenesis are still poorly understood. This review summarizes the current data concerning the role and signalling pathways of endoglin in hepatocellular carcinoma development and progression, and provides an overview of the strategies available for a specific targeting of CD105 in anti-angiogenic therapy in HCC.

Transcatheter Arterial Chemoembolization Plus 131I-Labelled Metuximab versus Transcatheter Arterial Chemoembolization Alone in Intermediate/Advanced Stage Hepatocellular Carcinoma: A Systematic Review and Meta-Analysis

Objective

The aim of the study was to compare transcatheter arterial chemoembolization (TACE) plus ¹³¹I-labelled metuximab with TACE alone for hepatocellular carcinoma (HCC).

Materials and Methods

A comprehensive search was conducted in PubMed, Embase, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, and Chinese BioMedical Literature Database with published date from the earliest to February 29th, 2016. No language restrictions were applied, but only prospective randomized controlled trials (RCTs) or non-RCTs were eligible for a full-text review. The primary outcome was the overall survival (OS) and effective rate (the rate of partial atrophy or complete clearance of the tumor lesion). The odds ratios (ORs) were combined using either the fixed-effects model or random-effects model.

Results

Eight trials (3 RCTs and 5 non-RCTs) were included, involving a total of 1121 patients. Patients receiving combined therapy of TACE plus ¹³¹I-labelled metuximab showed significant improvement in effective rate {OR = 4.00, (95% confidence interval [CI]: 2.40–6.66), p < 0.001}, 1-year OS (OR = 2.03 [95% CI: 1.55–2.67], p < 0.001) and 2-year OS (OR = 2.57 [95% CI: 1.41–4.66], p = 0.002].

Conclusion

TACE plus ¹³¹I-labelled metuximab is more beneficial for treating advanced HCCs than TACE alone in terms of tumor response and OS. Large, multi-center, and blinded randomized trials are required to confirm these findings.

Anti-Human Endoglin (hCD105) Immunotoxin-Containing Recombinant Single Chain Ribosome-Inactivating Protein Musarmin 1

Endoglin (CD105) is an accessory component of the TGF-β receptor complex, which is expressed in a number of tissues and over-expressed in the endothelial cells of tumor neovasculature. Targeting endoglin with immunotoxins containing type 2 ribosome-inactivating proteins has proved an effective tool to reduce blood supply to B16 mice tumor xenografts. We prepared anti-endoglin immunotoxin (IT)-containing recombinant musarmin 1 (single chain ribosome-inactivating proteins) linked to the mouse anti-human CD105 44G4 mouse monoclonal antibody via N-succinimidyl 3-(2-pyridyldithio) propionate (SPDP). The immunotoxin specifically killed L929 fibroblast mouse cells transfected with the short form of human endoglin with IC50 values in the range of 5 × 10(-10) to 10(-9) M.