Potent killing of HBV-related hepatocellular carcinoma by a chimeric protein of anti-HBsAg single-chain antibody and truncated Bid

Fusion of apoptosis-related protein Cytochrome c with anti-HER-2 single-chain antibody targets the suppression of HER-2+ breast cancer

Cancer treatment has gradually developed from toxic chemotherapy to targeted therapy with fewer side effects. Approximately 30% of breast cancer patients overexpress human epidermal growth factor receptor 2 (HER-2). Previous studies have successfully produced single-chain antibodies (scFv) targeting HER-2+ breast cancer; however, scFv have poor stability, easy aggregation and a shorter half-life, which have no significant effect on targeting therapy. Moreover, scFv has been considered as a drug delivery platform that can kill target cells by effector molecules. However, the functional killing domains of immunotoxins are mainly derived from plant or bacterial toxins, which have a large molecular weight, low tissue permeability and severe side effects. To address these concerns, we designed several apoptotic immune molecules to replace exogenous toxins using endogenous apoptosis-related protein DNA fragmentation factor 40 (DFF40) and tandem-repeat Cytochrome c base on caspase-3 responsive peptide (DEVD). Our results suggest that DFF40 or Cytc fusion scFv specifically targets HER-2 overexpressing breast cancer cells (SK-BR-3 and BT-474) rather than HER-2 negative cells (MDA-MB-231 and MCF-7). Following cellular internalization, apoptosis-related proteins inhibited tumour activity by initiating endogenous apoptosis pathways, which significantly reduced immunogenicity and toxic side effects. Therefore, we suggest that immunoapoptotic molecules may become potential drugs for targeted immunotherapy of breast cancer.

Syngeneic homograft of framework regions enhances the affinity of the mouse anti-human epidermal receptor 2 single-chain antibody e23sFv

e23sFv is a HER2-targeted single-chain variable fragment (scFV) that was characterized as the targeting portion of a HER2-targeted tumour proapoptotic molecule in our previous study. In vitro antibody affinity maturation is a method to enhance antibody affinity either by complementarity-determining region (CDR) mutagenesis or by framework region (FR) engraftment. In the present study, the affinity of e23sFv was enhanced using two strategies. In one approach, site-directed mutations were introduced into the FRs of e23sFv (designated EMEY), and in the other approach e23sFv FRs were substituted with FRs from the most homologous screened antibodies (designated EX1 and EX2). Notably, EX1 derived from the FR engraftment strategy demonstrated a 4-fold higher affinity for HER2 compared with e23sFv and was internalized into HER2-overexpressing cells; however, EMEY and EX2 exhibited reduced affinity for HER2 and decreased internalization potential compared with EX1. The 3D structure of EX1 and the HER2-EX1 complex was acquired using molecular homology modelling and docking and the HER2 epitopes of EX1 and the molecular interaction energy of the EX1-HER2 complex were predicted. In the present study, it was demonstrated that scFv affinity improvement based on sequence alignment was feasible and effective. Moreover, the FR grafting strategy was indicated to be more effective and simple compared with site-directed mutagenesis to improve e23sFv affinity. In conclusion, it was indicated that the affinity-improved candidate EX1 may present a great potential for the diagnosis and treatment of HER2-overexpressing tumours.

Interaction with CD68 and Regulation of GAS6 Expression by Endosialin in Fibroblasts Drives Recruitment and Polarization of Macrophages in Hepatocellular Carcinoma

Fibroblasts and macrophages play key roles in the development of hepatocellular carcinoma (HCC). However, cross-talk between these two kinds of cells has not been well studied. Endosialin (CD248/TEM1) is a transmembrane glycoprotein that is expressed in certain cancer cells, tumor stromal cells, and pericytes. In this study, we found that endosialin is mainly expressed in cancer-associated fibroblasts (CAF) in HCC and its expression inversely correlates with patient prognosis. Endosialin interacted with CD68 to recruit macrophages and regulated expression of GAS6 in CAFs to mediate M2 polarization of macrophages. The fully human antibody IgG78 bound glycosylated endosialin and induced its internalization in CAFs, thus weakening the cross-talk between CAFs and macrophages. In subcutaneous and orthotopic xenograft models of HCC in nude mice, treatment with IgG78 significantly inhibited tumor growth. These results indicate that endosialin-positive CAFs promote HCC progression and highlight IgG78 as a promising therapeutic candidate for HCC treatment. SIGNIFICANCE: These findings highlight CAF-expressed endosialin as a primary regulator of macrophage recruitment and polarization and demonstrate endosialin inhibition as a potential treatment strategy for HCC. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/80/18/3892/F1.large.jpg.

Construction of humanized anti-HER2 single-chain variable fragments (husFvs) and achievement of potent tumor suppression with the reconstituted husFv-Fdt-tBid immunoapoptotin

As HER2 is frequently overexpressed in various malignancies, targeting HER2 is considered an efficient, highly selective antitumor therapy. HER2-targeted immunoconjugates are being developed and result in persistent remission of HER2-overexpressing tumors. However, many of the antibodies used as the targeting moiety are of murine origin and exhibit risk of inducing immunogenicity, limiting their antitumor therapeutic efficacy. Here, we humanized e23sFv, an HER2-targeting murine scFv with excellent affinity and specificity, using a human antibody consensus sequence engraftment strategy. The affinity of the initially humanized e23sFv was then rescued and improved by selective mutagenesis followed by phage-display-based affinity panning of the mutant pool. The resulting humanized e23sFv candidates (husFvs) exhibited up-to-94-fold increased affinity to recombinant HER2. The immunogenicity of e23sFv was dramatically alleviated after humanization, as indicated by the impaired production of cytokines by husFv-stimulated human PBMCs. Two internalizable husFvs with optimal affinity were applied to generate humanized immunoapoptotins by infusion with the translocation domain Fdt and the proapoptotic domain truncated Bid. The husFv-immunoapoptotins demonstrated improved HER2-targeting and tumor-killing capacities in vitro and in vivo compared with the e23sFv-immunoapoptotins and would enable the administration of multiple treatment cycles to patients, resulting in improved antitumor efficacy. Furthermore, the husFvs recognized distinct HER2 epitopes and could thus be used in combination with trastuzumab or pertuzumab to achieve robust synergistic antitumor effects in HER2-positive malignancies.

Combination treatment including targeted therapy for advanced hepatocellular carcinoma

Management of advanced hepatocellular carcinoma (HCC), one of the most lethal cancers worldwide, has presented a therapeutic challenge over past decades. Most patients with advanced HCC and a low possibility of surgical resection have limited treatment options and no alternative but to accept local or palliative treatment. In the new era of cancer therapy, increasing numbers of molecular targeted agents (MTAs) have been applied in the treatment of advanced HCC. However, mono-targeted therapy has shown disappointing outcomes in disease control, primarily because of tumor heterogeneity and complex cell signal transduction. Because incapacitation of a single target is insufficient for cancer suppression, combination treatment for targeted therapy has been proposed and experimentally tested in several clinical trials. In this article, we review research studies aimed to enhance the efficacy of targeted therapy for HCC through combination strategies. Combination treatments involving targeted therapy for advanced HCC are compared and discussed.

Immunoproapoptotic molecule scFv-Fdt-tBid modified mesenchymal stem cells for prostate cancer dual-targeted therapy

Highly efficient target therapy is urgently needed for prostate cancer with overexpression of γ-seminoprotein (γ-SM). Recent studies indicated that mesenchymal stem cells (MSCs) are attractive candidate for cell-based, targeted therapy due to their tumor tropism. Here we designed a dual-target therapeutic system in which MSCs were engineered to produce and deliver scFv-Fdt-tBid, a novel γ-SM-targeted immunoproapoptotic molecule. Such engineered MSCs (MSC.scFv-Fdt-tBid) would home to tumor sites and release the fusion protein to induce the apoptosis of prostate cancer cells. Our data demonstrated that scFv-Fdt-tBid showed a selective, potent and dose-dependent inhibition for γ-SM-positive cells (LNCaP, C4-2, 22Rv1) rather than γ-SM-negative cells and MSCs. Importantly, MSC.scFv-Fdt-tBid caused cell death through an apoptosis-dependent manner. Further, the tropism of MSC.scFv-Fdt-tBid to prostate cancer was verified both in vitro and in vivo. Finally, the in vivo experiments demonstrated that MSC.scFv-Fdt-tBid significantly inhibited γ-SM-positive tumor growth without toxic side effects. Collectively, this study represented a novel immunoproapoptotic molecule scFv-Fdt-tBid for γ-SM-positive tumors and demonstrated the therapeutic efficiency and safety of scFv-Fdt-tBid-modified MSCs against prostate cancers.

Dual targeting and enhanced cytotoxicity to HER2-overexpressing tumors by immunoapoptotin-armored mesenchymal stem cells

Mesenchymal stem cells (MSCs) are promising vehicles for the delivery of anticancer agents in cancer therapy. However, the tumor targeting of loaded therapeutics is essential. Here, we explored a dual-targeting strategy to incorporate tumor-tropic MSC delivery with HER2-specific killing by the immunoapoptotin e23sFv-Fdt-tBid generated in our previous studies. The MSC engineering allowed simultaneous immunoapoptotin secretion and bioluminescence detection of the modified MSCs. Systemic administration of the immunoapoptotin-engineered MSCs was investigated in human HER2-reconstituted syngeneic mouse models of orthotopic and metastatic breast cancer, as well as in a xenograft nude mouse model of orthotopic gastric cancer. In vivo dual tumor targeting was confirmed by local accumulation of the bioluminescence-imaged MSCs and persistence of His-immunostained immunoapoptotins in tumor sites. The added tumor preference of MSC-secreted immunoapoptotins resulted in a significantly stronger antitumor effect compared with purified immunoapoptotins and Jurkat-delivered immunoapoptotins. This immunoapoptotin-armored MSC strategy provides a rationale for its use in extended malignancies by combining MSC mobility with redirected immunoapoptotins against a given tumor antigen.