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The host immune system generally serves as a barrier against tumor formation. Programmed death-ligand 1 (PD-L1) is a critical “don't find me” signal to the adaptive immune system, whereas CD47 transmits an anti-phagocytic signal, known as the “don't eat me” signal, to the innate immune system. These and similar immune checkpoints are often overexpressed on human tumors. Thus, dual targeting both innate and adaptive immune checkpoints would likely maximize anti-tumor therapeutic effect and elicit more durable responses. Herein, based on the variable region of atezolizumab and consensus variant 1 (CV1) monomer, we constructed a dual-targeting fusion protein targeting both CD47 and PD-L1 using “Knobs-into-holes” technology, denoted as IAB. It was effective in inducing phagocytosis of tumor cells, stimulating T-cell activation and mediating antibody-dependent cell-mediated cytotoxicity in vitro. No obvious sign of hematological toxicity was observed in mice administered IAB at a dose of 100 mg/kg, and IAB exhibited potent antitumor activity in an immune-competent mouse model of MC38. Additionally, the anti-tumor effect of IAB was impaired by anti-CD8 antibody or clodronate liposomes, which implied that both CD8+ T cells and macrophages were required for the anti-tumor efficacy of IAB and IAB plays an essential role in the engagement of innate and adaptive immune responses. Collectively, these results demonstrate the capacity of an elicited endogenous immune response against tumors and elucidate essential characteristics of synergistic innate and adaptive immune response, and indicate dual blockade of CD47 and PD-L1 by IAB may be a synergistic therapy that activates both innate and adaptive immune response against tumors.

Background Infliximab (Remicade), a chimeric monoclonal antibody against human TNFα, will inevitably face competition from biosimilar products, because of its effectiveness in autoimmune diseases and rapidly increasing market demand. According to guidelines for biosimilar development, the “biosimilar-expression system” may differ from that of the innovator, but more appropriate studies should be carried out to demonstrate the comparability between biosimilar and innovator. CMAB008 is an infliximab biosimilar candidate developed by the State Key Laboratory of Antibody Medicine and Targeted Therapy of China. Infliximab was expressed in SP2/0 cells, while CMAB008 was produced in a CHO-expression system. Methods In this study, infliximab and CMAB008 were compared on physicochemical and biological characterizations, including protein content, activity, physiochemical integrity, impurities, additives, and immunogenicity. Results The results showed that they were highly similar and comparable, except some differences in glycosylation. As glycosylation profiles can influence immunogenicity and occurrence of allergy or other adverse reactions of antibody therapeutics, primary tolerability and pharmacokinetics of CMAB008 were evaluated. In the phase I clinical trial, plasma concentration of CMAB008 and antidrug antibodies were also measured using ELISA and bridging ELISA, respectively. CMAB008 exhibited favorable clinical tolerability, no adverse events in the 3 mg/kg single-dose group (recommended therapeutic dosage), and no serious adverse events in the multiple-dose group. Also, no injection-site reactions were observed in the experiment. Conclusion In summary, CMAB008 might have the potential to be an effective drug compared with infliximab.

Cancer initiating cells (CIC) are tumorigenic cancer cells that have properties similar to normal stem cells. CD20 is a phenotype of melanoma CIC that is responsible for melanoma drug resistance. Vincristine (VCR) is commonly used in melanoma therapy; however, it has been found ineffective against CIC. To target CD20+ melanoma CIC, we prepared VCR-containing immunoliposomes that were conjugated to CD20 antibodies (VCR-Lip-CD20). The drug release profile and the antibody-mediated targeting of the immunoliposomes were optimized to target CD20+ melanoma CIC. The immunoliposomes had desirable particle size (163 nm), drug encapsulation efficiency (91.8%), and drug release profile. We demonstrated that these immunoliposomes could successfully target more than 55% of CD20+ Chinese Hamster Ovary cells (CHO-CD20) even when the CHO-CD20 cells accounted for only 0.1% of a mixed population of CHO-CD20 and CHO cells. After treating WM266-4 melanoma mammospheres for 96 h, the ICo values of the drug delivered in VCR-Lip-CD20, VCR-Lip (VCR liposomes), and VCR were found to be 53.42, 98.99, and 99.09 μg/mL, respectively, suggesting that VCR-Lip-CD20 was 1.85 times more effective than VCR-Lip and VCR. VCR-Lip-CD20 could almost completely remove the tumorigenic ability of WM266-4 mammospheres in vivo, and showed the best therapeutic effect in WM266-4 melanoma xenograft mice. Significantly, VCR-Lip-CD20 could selectively kill CD20+ melanoma CIC in populations of WM266-4 cells both in vitro and in vivo. We demonstrated that VCR-Lip-CD20 has the potential to efficiently target and kill CD20+ melanoma CIC.

Although rituximab has revolutionized the treatment of hematological malignancies, the acquired resistance is one of the prime obstacles for cancer treatment, and development of novel CD20-targeting antibodies with potent anti-tumor activities and specificities is urgently needed. Emerging evidence has indicated that lysosomes can be considered as an "Achilles heel" for cancer cells, and might serve as an effective way to kill resistant cancer cells. HLA-DR antibody L243 has been recently reported to elicit potent lysosome-mediated cell death in lymphoma and leukemia cells, suggesting that HLA-DR could be used as a potential target against lymphoma. In this study, we generated a bispecific immunoglobulin G-like antibody targeting both CD20 and HLA-DR (CD20-243 CrossMab) through CrossMab technology. We found that the CrossMab could induce remarkably high levels of complement-dependent cytotoxicity, antibody-dependent cell-mediated cytotoxicity and anti-proliferative activity. Notably, although HLA-DR is expressed on normal and malignant cells, the CrossMab exhibited highly anti-tumor specificity, showing efficient eradication of hematological malignancies both in vitro and in vivo. Our data indicated that combined targeting of CD20 and HLA-DR could be an effective approach against malignancies, suggesting that CD20-243 CrossMab would be a promising therapeutic agent against lymphoma.

The anti-ErbB2 antibody trastuzumab has shown significant clinical benefits in metastatic breast cancer. However, resistance to trastuzumab is common. Heterodimerization between ErbB2 and other ErbBs may redundantly trigger cell proliferation signals and confer trastuzumab resistance. Here, we developed a bispecific anti-ErbB2 antibody using trastuzumab and pertuzumab, another ErbB2-specific humanized antibody that binds to a distinct epitope from trastuzumab. This bispecific antibody, denoted as TPL, retained the full binding activities of both parental antibodies and exhibited pharmacokinetic properties similar to those of a conventional immunoglobulin G molecule. Unexpectedly, TPL showed superior ErbB2 heterodimerization-blocking activity over the combination of both parental monoclonal antibodies, possibly through steric hindrance and/or inducing ErbB2 conformational change. Further data indicated that TPL potently abrogated ErbB2 signaling in trastuzumab-resistant breast cancer cell lines. In addition, we showed that TPL was far more effective than trastuzumab plus pertuzumab in inhibiting the growth of trastuzumab-resistant breast cancer cell lines, both in vitro and in vivo. Importantly, TPL treatment eradicated established trastuzumab-resistant tumors in tumor-bearing nude mice. Our results suggest that trastuzumab-resistant breast tumors remain dependent on ErbB2 signaling and that comprehensive blockade of ErbB2 heterodimerization may be an effective therapeutic avenue. The unique potential of TPL to overcome trastuzumab resistance warrants its consideration as a promising treatment in the clinic. Cancer Res; 73(21); 6471–83. ©2013 AACR.

Antibody-drug conjugates (ADCs) have exhibited potent clinical benefits in cancer therapy. However, development of ADCs against epidermal growth factor receptor (EGFR) has limitations because of wide expression of EGFR in both normal and tumor tissues. Previously, we developed an anti-EGFR protease-activated antibody (pro-antibody), termed as PanP, which remains inert against EGFR until activated by tumor-specific protease. Herein, we for the first time report a new class of pro-antibody-drug conjugate (PDC) against EGFR, denoted as PanP-DM1. It has been designed to selectively target the EGFR-overexpressing tumor cells and exert greater anti-tumor activity compared with PanP. Our data showed that PanP-DM1 also could be selectively activated by tumor-specific protease 'uPA'. Furthermore, activated PanP-DM1 was potently cytotoxic against EGFR-overexpressing tumor cell lines in vitro. Crucially, our data indicated that PanP-DM1 was significantly more effective in eradicating EGFR-overexpressing tumors in vivo. Additionally, toxicity was preliminarily evaluated in mice as measured by body weight loss. In summary, our study suggests that PanP-DM1, a novel pro-antibody-drug conjugate, has cancer-selectivity, efficacy and safety profile that supports its potential use for EGFR-overexpressing tumors.

The development of immunoliposomes for systemic siRNA (small interfering RNA) delivery is highly desired. We reported previously the development of targeted LPD (liposome–polycation–DNA complex) conjugated with anti-EGFR (epidermal growth factor receptor) Fab′ (TLPD-FCC) for siRNA delivery, which showed superior gene silencing activity in EGFR-overexpressing breast cancers. However, TLPD-FCC did not achieve satisfactory gene silencing activity in EGFR-overexpressing hepatocellular carcinoma (HCC). In this study, some modifications including increased antibody conjugation efficiency and reduced PEGylation degree were made to TLPD-FCC to increase gene silencing activity in HCC. The resultant optimized liposomes denoted as TLPD-FP75 efficiently bound and delivered to EGFR-overexpressing HCC, resulting in enhanced gene silencing activity compared to untargeted LPD (NTLPD-FP75). Tissue distribution in vivo revealed that the accumulation of TLPD-FP75 was higher than NTLPD-FP75 in orthotopic HCC model of mice. The promoted uptake of TLPD-FP75 in HCC cells was confirmed by confocal microscopy. To investigate the in vivo gene silencing activity, we administered TLPD-FP75 by intravenous injections into mice bearing orthotopic HCC. The results showed TLPD-FP75 potently suppressed luciferase expression, while little silencing was observed in NTLPD-FP75. TLPD-FP75 was demonstrated to possess potent gene silencing activity in HCC and will potentially increase the feasibility of HCC gene therapy.

Osteopontin (OPN) is a cytokine with multiple functions, including the regulation of innate immune response. However, the detailed function and mechanism of OPN in host defense against invaded microorganisms remain unclear. In this report, we revealed that OPN could affect the clearance of Propionibacterium acnes in kupffer cells. In a murine model of P. acnes induced hepatic granuloma, OPN-deficient mice or wild-type (WT) mice treated with anti-OPN mAb exhibited more hepatic granuloma formation than WT mice. Increased infiltration of intrahepatic leukocytes, higher expression of TLRs, and significantly upregulated level of proinflammatory cytokines of liver tissue were observed in OPN-deficient mice after P. acnes challenge. Moreover, in vitro assay showed that kupffer cells isolated from OPN(-/-) mice exhibited impairment in clearance of P. acnes. Kupffer cells isolated from OPN(-/-) mice showed reduced level of NADPH oxidase-mediated reactive oxygen species (ROS) in response to P. acnes, which was regulated by NADPH oxidase subunit p47phox. Further investigation revealed that OPN interaction with αvβ3 integrin activated PI3K and ERK signal pathways, leading to the expression of p47phox. Taken together, these data demonstrated an important role of OPN in enhancing the antimicrobial innate immune response by modulation of bacterium clearance activity in kupffer cells.

The LPD (liposome-polycation-DNA complex) is an effective nanovector for systemically small interfering RNA (siRNA) delivery which was well characterized previously. However, little effort was spend on the development of targeted LPD conjugated with tumor specific antibody (TLPD) which would be potent in promoting siRNA delivery in tumor. Here, we prepared TLPD through a self-assembling process followed by anti-EGFR antibody conjugation. The effect of antibody type, conjugation strategy and amount on the physicochemical and biological properties of TLPD was investigated. We obtained optimized TLPD conjugated with anti-EGFR Fab' by conventional conjugation (TLPD-FCC), which possessed a small size around 150nm and superior in vitro stability. Compared with nontargeted LPD (NTLPD), TLPD-FCC showed significantly enhanced binding affinity and luciferase gene silencing activity in EGFR overexpressing MDA-MB-231 breast cancer cells in vitro. Moreover, the in vivo accumulation of TLPD-FCC was obviously higher than that of NTLPD in MDA-MB-231 tumor 24h post intravenous injection. The promoted uptake of TLPD-FCC in MDA-MB-231 tumor was further confirmed by confocal microscopy. Notably, three intravenous injections of siRNA in TLPD-FCC significantly silenced luciferase expression by ∼20%, whereas NTLPD showed little effect. All these results suggested that our TLPD-FCC have a great potential in delivering siRNA to EGFR overexpressing breast cancers.

Osteopontin has been implicated in various inflammatory diseases including rheumatoid arthritis, multiple sclerosis, Crohn's disease, and fulminant hepatitis. Increased expression of osteopontin has been detected in pathological foci of these diseases. RA and fulminant hepatitis have been successfully treated by administration of neutralizing anti-osteopontin antibody in mice. However, rodent antibodies are highly immunogenic in humans and therefore limited in their clinical application. Here, a murine monoclonal antibody 23C3 against human osteopontin, was humanized by complementarity-determining region grafting method based on computer-assisted molecular modeling. The humanized version of 23C3, denoted as Hu23C3, was shown to possess affinity comparable to that of its parental antibody. Hu23C3 could also inhibit monocyte migration in response to osteopontin in vitro. Furthermore, in vivo data showed that Hu23C3 significantly protects mice from Concanavalin A (Con A) induced-liver injury in association with the reduction of transaminase activities and improvement of liver injury. Mechanistic studies demonstrated that Hu23C3 inhibited T and NKT cell infiltration, and activation of nuclear factor κB (NF-κB) in the liver, resulting in reduction of TNF-α and IFN-γ production. Thus, our data strongly support that the humanized anti-osteopontin antibody, Hu23C3, may have a potential for the treatment of T cell mediated-hepatitis in human.

The major cause of cancer mortality is the metastatic spread of tumor cells that can occur via multiple routes, including the vascular system and the lymphatic system. In this study, we developed an IgG-like fusion protein molecule [vascular endothelial growth factor (VEGF) receptor 31–immunoglobulin (VEGFR31-Ig)] which could simultaneously bind the angiogenic growth factor VEGF-A and the lymphangiogenic growth factor VEGF-C. Importantly, VEGFR31-Ig exhibited VEGF-A–binding affinity similar to that of VEGFTrap, the most potent VEGF-A binder, and VEGF-C–binding affinity comparable with that of the soluble fusion protein VEGFR3-Ig (sVEGFR3). Pharmacokinetic analysis in mice showed that VEGFR31-Ig had improved pharmacokinetic properties compared with either VEGFTrap or sVEGFR3. In a highly metastatic human hepatocellular carcinoma (HCCLM3) model in severe combined immunodeficient mice, VEGFR31-Ig potently blocked both tumor angiogenesis and lymphangiogenesis, effectively inhibiting primary tumor growth and metastasis to lungs and lymph nodes. In contrast, VEGFTrap only suppressed primary tumor growth and metastasis to lungs by inhibiting tumor angiogenesis, whereas VEGFR3 was only effective in suppressing tumor metastasis to lymph nodes by blocking tumor lymphangiogenesis. Although a combination of VEGFTrap (25 mg/kg twice weekly) and sVEGFR3 (25 mg/kg twice weekly) can achieve the same therapeutic effect as VEGFR31-Ig (25 mg/kg twice weekly) in the HCCLM3 xenograft mouse model, developing two separate receptor-Ig fusion proteins for clinical use as combination therapy is impractical, mainly owing to regulatory hurdles and cost. Taken together, the VEGFR31-Ig fusion protein presented here has been suggested to have great potential for the treatment of metastatic cancer. Cancer Res; 70(6); 2495–503

Despite widespread use of the anti-CD20 monoclonal antibody (mAb), rituximab, in treating B-cell lymphomas, its efficacy remains variable and often modest. A better understanding of rituximab-mediated killing mechanisms is essential to develop more effective therapeutic agents. In this study, we modulated the binding property of rituximab by introducing several point mutations in its complementarity-determining regions. The data showed that changing the binding avidity of rituximab in the range from 10−8 to 10−10 M could regulate its antibody-dependent cellular cytotoxicity but not affect its complement-dependent cytotoxicity and apoptosis-inducing activity in B-lymphoma cells. Contradictory to previous findings, we found that the complement-dependent cytotoxicity potency of CD20 mAb was independent of the off-rate. Despite still being a type I CD20 mAb, a rituximab triple mutant (H57DE/H102YK/L93NR), which had a similar binding avidity to a double mutant (H57DE/H102YK), was unexpectedly found to have extremely potent apoptosis-inducing activity. Moreover, this triple mutant, which was demonstrated to efficiently initiate both caspase-dependent and -independent apoptosis, exhibited potent in vivo therapeutic efficacy, even in the rituximab-resistant lymphoma model, suggesting that it might be a promising therapeutic agent for B-cell lymphomas.

Osteopontin (OPN) has been implicated as an important mediator of breast cancer progression and metastasis and has been investigated for use as a potential therapeutic target in the treatment of breast cancer. However, the in vivo antitumor effect of anti-OPN antibodies on breast cancer has not been reported. In this study, a mouse anti-human OPN antibody (1A12) was humanized by complementarity-determining region grafting method based on computer-assisted molecular modeling. A humanized version of 1A12, denoted as hu1A12, was shown to possess affinity comparable to that of its parental antibody. The ability of hu1A12 to inhibit cell migration, adhesion, invasion and colony formation was assessed in a highly metastatic human breast cancer cell line MDA-MB-435S. The results indicated that hu1A12 was effective in inhibiting the cell adhesion, migration, invasion and colony formation of MDA-MB-435S cells in vitro. hu1A12 also showed significant efficacy in suppressing primary tumor growth and spontaneous metastasis in a mouse lung metastasis model of human breast cancer. The specific epitope recognized by hu1A12 was identified to be (212)NAPSD(216), adjacent to the calcium binding domain of OPN. Our data strongly support that OPN is a potential target for the antibody-based therapies of breast cancer. The humanized anti-OPN antibody hu1A12 may be a promising therapeutic agent for the treatment of human breast cancer.

Objective To test the effects of a novel monoclonal antibody (mAb) against human osteopontin (OPN) in the prevention and treatment of collagen-induced arthritis (CIA) and to elucidate the underlying mechanisms of these effects. Methods DBA/1J mice immunized with type II collagen to induce CIA were monitored to assess the effects of anti-OPN mAb on the clinical severity of the disease, and pathologic changes in the joints were examined histologically. The effects of anti-OPN mAb on survival of activated T cells from arthritic mice and from the synovial fluid of patients with rheumatoid arthritis (RA) were determined by TUNEL assay or annexin V assay. The levels of apoptosis-related proteins (Bim, Bax, and Bcl-2) and NF-κB were detected by immunoblot analysis. Results One anti-OPN mAb, 23C3, was effective in inhibiting the development of CIA and even reversing established disease in DBA/1J mice. Monoclonal antibody 23C3 reduced the levels of serum type II collagen–specific autoantibodies and proinflammatory cytokines, and suppressed T cell recall responses to type II collagen. Mechanistic studies demonstrated that OPN prevented the death of type II collagen–activated murine T cells and synovial T cells from RA patients. Monoclonal antibody 23C3 promoted apoptosis of the activated T cells, particularly CD4+ T cells, by inhibiting activation of NF-κB and by altering the balance among the proapoptotic proteins Bim and Bax and the antiapoptotic protein Bcl-2. Screening of a phage display peptide library led to identification of the epitope ATWLNPDPSQKQ as being recognized by this novel antibody. Conclusion Because of its ability to effectively promote apoptosis of activated T cells, mAb 23C3 may be a novel therapeutic agent for the treatment of RA.

Modest clinical outcomes of dendritic cell (DC) vaccine trials call for novel strategies. In this study, we have created a chimeric CD40 molecule that incorporates a single chain Fv (scFv) molecule specific for human ErbB2 antigen and fusing to the membrane spanning and cytosolic domains of murine CD40. After adenoviral transfer to bone marrow–derived DC, this chimeric receptor (CR) induced nuclear factor-κB (NF-κB)–dependent DC activation and effector function when cultured with immobilized ErbB2 protein or ErbB2-positive tumor cells in vitro. In vivo migration assays showed that ∼40% injected CR-modified DC (scFv-CD40-DC) effectively migrated to ErbB2-positive tumors, where they were activated after ErbB2 antigen stimulation, and sequentially homed into the draining lymph nodes. In murine ErbB2-positive D2F2/E2 breast tumor (BALB/c) and EL4/E2 thymoma (C57BL/6) models, i.v. injection of 1 × 106 scFv-CD40-DC significantly inhibited tumor growth and cured established tumors. Importantly, the cured mice treated by injection of scFv-CD40-DC were effective in preventing both ErbB2-positive and parental ErbB2-negative tumor rechallenge. Analysis of the underlying mechanism revealed that i.v. infusion of scFv-CD40-DC elicited tumor-specific CTL responses, and the transfer of CTLs from scFv-CD40-DC–treated mice protected naive mice against a subsequent tumor challenge. These results support the concept that genetic modification of DC with tumor-associated antigen-specific CD40 chimeric receptor might be a useful strategy for treatment of human cancers. [Cancer Res 2008;68(10):3854–62]

Despite the effectiveness of the anti-CD20 monoclonal antibody (mAb) Rituximab (C2B8) in the treatment of B-cell lymphoma, its efficacy remains variable and often modest. It seems likely that a combination of multiple mechanisms, such as complement-dependent cytotoxicity (CDC) and apoptotic signaling, underlies the therapeutic success of anti-CD20 mAbs. Unfortunately, all the current anti-CD20 mAbs effective in CDC are relatively inactive in signaling cell death and vice versa. In this study, we developed two genetically engineered tetravalent antibodies (TetraMcAb) respectively derived from the anti-CD20 mAbs C2B8 and 2F2. TetraMcAbs, with a molecular mass only 25 kDa higher than native divalent antibodies (DiMcAb), were shown not only to be as effective in mediating CDC and antibody-dependent cellular cytotoxicity against B-lymphoma cells as DiMcAbs but also to have antiproliferative and apoptosis-inducing activity markedly superior to that of DiMcAbs. Interestingly, whereas 2F2 and C2B8 were equally effective in inducing cell growth arrest and apoptosis, the functions of their tetravalent versions, 2F2(ScFvHL)4-Fc and C2B8(ScFvHL)4-Fc, were significantly different. 2F2(ScFvHL)4-Fc exhibited exceptionally more potent antiproliferative and apoptosis-inducing activity than that of C2B8(ScFvHL)4-Fc. Immunotherapeutic studies further showed that 2F2(ScFvHL)4-Fc was far more effective in prolonging the survival of severe combined immunodeficient mice bearing systemic Daudi or Raji tumors than C2B8, 2F2, and C2B8(ScFvHL)4-Fc, suggesting that it might be a promising therapeutic agent for B-cell lymphoma. [Cancer Res 2008;68(7):2400–8]

cSM5-1 is a mouse-human chimeric antibody which has a high specificity for hepatocellular carcinoma, melanoma and breast cancer. In this study, cSM5-1 was found to be able to inhibit cell growth and induce apoptosis in hepatocellular carcinoma cells. The antitumor activity of cSM5-1 was closely correlated with the expression level of the SM5-1 binding protein in the cancer cells. The role of caspases in cSM5-1-induced apoptosis was also investigated, indicating that cSM5-1-induced apoptosis was partially caspase-dependent and caspase-10 played a critical role. These in vitro data indicate that cSM5-1 has the potential to be a promising candidate for cancer treatment.

BACKGROUND Previous studies have shown that blockade of LIGHT, a T-cell costimulatory molecule belonging to the tumor necrosis factor (TNF) superfamily, by soluble lymphotoxin beta receptor-Ig (LTbetaR-Ig) inhibited the development of graft-versus-host disease. The cardiac allografts were significantly prolonged in LIGHT deficient mice. No data are yet available regarding the role of the LIGHT/HVEM pathway in more stringent fully allogeneic models such as skin and islet transplantation models. METHODS Streptozotocin-induced chemical diabetic BALB/C mice underwent transplantation with allogeneic C57BL/6 islets and were treated with LTbetaR-Ig, CTLA4-Ig or a combination of both in the early peritransplant period. RESULTS Administration of CTLA4-Ig or LTbeta R-Ig alone only increased graft survival to 55 days and 27 days respectively, whereas simultaneous blockade of both pathways significantly prolonged the islet allograft survival for more than 100 days. Long-term survivors were retransplanted with donor-specific (C57BL/6) islets and the grafted islets remained functional for more than 100 days. All of islet allografts were protected against rejection when the mixtures of 1x10(6) CD4+ T cells from tolerant mice and islet allografts were cotransplanted under the renal capsule of the naive BALB/c recipients. CONCLUSIONS These data indicate that: 1) a synergistic effect for prolonged graft survival can be obtained by simultaneously blocking LIGHT and CD28 signaling in the stringent model of islet allotransplantation; 2) development of donor-specific immunological tolerance is associated with the presence of regulatory T-cell activity; and 3) local cotransplantation of the allografts with the regulatory T cells can effectively prevent allograft rejection and induce donor-specific tolerance in lymphocytes-sufficient recipients.

FOXP3 is a member of the forkhead/winged-helix family of transcriptional regulators which plays a key role in CD4+CD25+ regulatory T-cell (Tregs) function and represents a specific marker for these cells. In order to understand the functional role of FOXP3 and identify Tregs both in normal development and relevant diseases, protein-DNA and protein-protein interaction studies involving this factor are essentially required. Such investigations would be facilitated by the availability of significant amounts of purified FOXP3 protein and specific McAb against FOXP3. Here, we report the purification of human FOXP3 (HFOXP3) expressed in Escherichia coli as a soluble and functional glutathione-S-transferase (GST) fusion protein. Through a single purification procedure, 4 mg of GST-HFOXP3 recombinant protein was obtained per litre of bacterial culture. The biological activity of the recombinant protein was verified by EMSA assay. The yield of folded FOXP3 in the purified GST-FOXP3 was determined by reverse phase HPLC. Besides, we generated and obtained two specific monoclonal antibodies by immunizing BALB/c mouse with the purified GST-HFOXP3 protein. The resulting HFOXP3 protein and anti-HFOXP3 McAbs might provide a useful tool in studying Tregs development and immune regulations.

Panitumumab, as a commercially available antibody, is an effective anticancer therapeutic against epidermal growth factor receptor (EGFR), although it exerts weak antibody-dependent cell-mediated cytotoxicity (ADCC) activity owing to its IgG2 nature. Here, we firstly engineered panitumumab by grafting its variable region into an IgG1 backbone. The engineered panitumumab (denoted as Pan) retained binding activity identical to the parental antibody while exhibiting stronger ADCC activity in vitro and more potent antitumor effect in vivo. To further enhance the target selectivity of Pan, we generated Pan-P by tethering an epitope-blocking peptide to Pan via a tumor-specific protease selective linker. Pan-P showed almost 40-fold weaker affinity compared with Pan, but functional activity was restored to a similar extent as Pan when Pan-P was selectively activated by urokinase-type plasminogen activator (uPA). More importantly, targeted localization of Pan-P was observed in tumor samples from colorectal cancer (CRC) patients and tumor-bearing nude mice, strongly indicating that specific activation also existed ex vivo and in vivo. Furthermore, Pan-P also exhibited effective in vivo antitumor potency similar to Pan. Taken together, our data evidence the enhanced antitumor potency and excellent target selectivity of Pan-P, suggesting its potential use for minimizing on-target toxicity in anti-EGFR therapy.

Fms-like tyrosine kinase 3 ligand (Flt3L) plays an important role in development and activation of dendritic cells (DCs) and natural killer cells (NK). It has been shown that administration of either tumor cells transfected in vitro with Flt3L vectors or soluble Flt3L fusion protein in a high dose can enhance host antitumor immunity in animal model systems. In this study, we developed a recombinant defective adenovirus with an insert of gene encoding extracellular domain of mouse Flt3L (Ad-mFlt3L) under control of cytomegalovirus promoter and investigated its biological efficacy in eliciting tumor-specific immune response against hepatocellular carcinoma in mouse hepatoma model. The constructed Ad-mFlt3L efficiently infected hepa 1-6 hepatoma cells both in vitro and in vivo, leading to a high production of mFlt3L proteins in association with accumulation of DCsNK cells and lymphocytes in local tumor tissues. Tumor cells infected with Ad-mFlt3L lost tumorigenicity and became more immunogenic in syngeniec animal models. Intratumoral injection of Ad-mFlt3L (10(9) expression-forming unit) x 3 significantly inhibited tumor growth with elicitation of long-lasting antitumor immunity, which is both preventive and curative. The tumor-specific immunity can be partially abrogated by depletion of either CD3+CD4+ T cells or NK cells and can be also re-established in naïve animals by adoptive transfer of splenocytes from treated mice. The results suggest that adenovirus-mediated Flt3L gene therapy may provide a useful strategy for treatment of cancers.

Although monoclonal antibodies, including CD20 antibody rituximab, are standard therapeutics for several cancers, their efficacy remains variable and often modest. There is an urgent need to enhance the efficacy of the current generation of anticancer antibodies. Flt3 ligand, a soluble protein, has the ability to induce substantial expansion of dendritic cells (DCs). In this study, we constructed a bispecific immunoglobulin G-like bispecific fusion protein (BiFP) targeting both CD20 and Flt3 (CD20-Flex) by using CrossMab technology. We found that the BiFP exhibited stabilities that were comparable with the parental antibody rituximab and were able to bind to both targets with unaltered binding affinity. Notably, our data indicated that CD20-Flex BiFP could not only eliminate lymphoma temporarily but also potentiate tumor-specific T-cell immunity, which affords a long-lasting protection from tumor recurrence. The results showed that the expansion and infiltration of DCs into tumor tissues by CD20-Flex BiFP could be an effective way to generate protective immune responses against cancer, suggesting that the CD20-Flex BiFP could be a promising therapeutic agent against B-cell lymphomas.

The chemotherapy combined with gene therapy has received great attention. We developed targeted LPD (liposome-polycation-DNA complex) conjugated with anti-EGFR (epidermal growth factor receptor) Fab' co-delivering adriamycin (ADR) and ribonucleotide reductase M2 (RRM2) siRNA (ADR-RRM2-TLPD), to achieve combined therapeutic effects in human hepatocellular carcinoma (HCC) overexpressing EGFR. The antitumor activity and mechanisms of ADR-RRM2-TLPD were investigated. The results showed that RRM2 expression was higher in HCC than in non-HCC tissue, and RRM2 siRNA inhibited HCC cell proliferation, suggesting that RRM2 is a candidate target for HCC therapy. ADR-RRM2-TLPD delivered ADR and RRM2 siRNA to EGFR overexpressing HCC cells specifically and efficiently both in vitro and in vivo, resulting in enhanced therapeutic effects (cytotoxicity, apoptosis and senescence-inducing activity) compared with single-drug loaded or non-targeted controls, including ADR-NC-TLPD (targeted LPD co-delivering ADR and negative control siRNA), RRM2-TLPD (targeted LPD delivering RRM2 siRNA) and ADR-RRM2-NTLPD (non-targeted LPD co-delivering ADR and RRM2 siRNA). Mechanism studies showed that p21 is involved in the combined therapeutic effect of ADR-RRM2-TLPD. The average weight of the orthotopic HCC in mice treated with ADR-RRM2-TLPD was significantly lighter than that of mice treated with other controls. Thus, ADR-RRM2-TLPD represents a potential strategy for combined therapy of HCC overexpressing EGFR.

There is an urgent need for improved therapy for advanced ovarian carcinoma, which may be met by administering immune-modulatory monoclonal antibodies (mAbs) to generate a tumor-destructive immune response. Using the ID8 mouse ovarian cancer model, we investigated the therapeutic efficacy of various mAb combinations in mice with intraperitoneal (i.p.) tumor established by transplanting 3 × 10(6) ID8 cells 10 days previously. While most of the tested mAbs were ineffective when given individually or together, the data confirm our previous finding that 2 i.p. injections of a combination of anti-CD137 with anti-PD-1 mAbs doubles overall survival. Mice treated with this mAb combination have a significantly increased frequency and total number of CD8(+) T cells both in the peritoneal lavage and spleens, and these cells are functional as demonstrated by antigen-specific cytolytic activity and IFN-γ production. While administration of anti-CD137 mAb as a single agent similarly increases CD8(+) T cells, these have no functional activity, which may be attributed to up-regulation of co-inhibitory PD-1 and TIM-3 molecules induced by CD137. Addition of the anti-cancer drug cisplatin to the 2 mAb combination increased overall survival >90 days (and was probably curative) by a mechanism which included a systemic CD8(+) T cell response with tumor specificity and immunological memory. Strikingly, combined treatment of cisplatin and CD137/PD-1 mAb also gave rise to the long-term survival of mice with established TC1 lung tumors. A similar combination of the 2 mAbs and cisplatin should be considered for clinical 'translation'.

Micelles with high in vivo serum stability and intratumor accumulation post intravenous (i.v.) injection are highly desired for promoting chemotherapy. Herein, we finely synthesized and tailored well-defined anti-Her2 antibody Fab fragment conjugated immunomicelles (FCIMs), which showed interesting dual targeting function. The thermosensitive poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide)(118) (PID(118)) shell with volume phase transition temperature (VPTT: 39 °C) and the anchored anti-Her2 Fab moiety contributed to the passive and active targeting, respectively. The doxorubicin (DOX) loading capacity of such FCIMs was successfully increased about 2 times by physically enhanced hydrophobicity of inner reservoir without structural deformation. The cellular uptake and intracellular accumulation of DOX by temperature regulated passive and antibody navigated active targeting was 4 times of Doxil. The cytotoxicity assay against Her2 overexpression gastric cancer cells (N87s) showed that the IC50 of the FCIMs was ≈ 9 times lower than that of Doxil under cooperatively targeting by Fab at T > VPTT. FCIMs showed high serum stability by increasing the corona PID(118) chain density (S(corona)/N(agg)). In vivo tissue distribution was evaluated in Balb/c nude mice bearing gastric cancer. As observed by the IVIS(®) imaging system, the intratumor accumulation of such finely tailored FCIMs system was obviously promoted 24 h post i.v. administration. Due to the high stability and super-targeting, the in vivo xenografted gastric tumor growth was significantly inhibited with relative tumor volume

To develop more effective anti-CD20 reagents for B-cell lymphoma, we designed and constructed a bispecific tetravalent anti-CD20 antibody, 11B8/2F2(ScFvHL)4-Fc, derived from two fully human monoclonal antibodies (mAb), 2F2 and 11B8. 2F2 is a type I CD20 mAb, which is potent in complement-dependent cytotoxicity (CDC) assays but poor at inducing apoptosis, whereas 11B8 is a type II CD20 mAb, which is effective in induction of apoptosis but ineffective in CDC. Our results showed that 11B8/2F2(ScFvHL)4-Fc possessed apoptosis-inducing activity markedly superior to that of 2F2, and even 11B8, 11B8 plus 2F2, and 2F2(ScFvHL)4-Fc, a 2F2-derived monospecific tetravalent antibody developed previously. Interestingly, 11B8/2F2(ScFvHL)4-Fc displayed a similar ability to mediate CDC as 2F2(ScFvHL)4-Fc, although two of its four antigen-binding arms originated from 11B8. To explore why 11B8/2F2(ScFvHL)4-Fc was so potent in both CDC and apoptotic activity, a bispecific divalent antibody composed of 2F2 and 11B8, denoted as 11B8/2F2-ScFvFc, was constructed and characterized. Our results partially explained the reason for the potent CDC and apoptosis-inducing activity of 11B8/2F2(ScFvHL)4-Fc. Further in vivo therapy studies showed that 11B8/2F2(ScFvHL)4-Fc had a significantly more potent antitumor activity compared with 2F2, 11B8, 2F2 plus 11B8, and 2F2(ScFvHL)4-Fc. These data suggest that 11B8/2F2(ScFvHL)4-Fc may serve as a potential therapeutic agent for B-cell lymphoma. Cancer Res; 70(15); 6293–302. ©2010 AACR.

Despite the effectiveness of the anti-CD20 chimeric antibody (mAb), rituximab, in treating B-cell lymphomas, its efficacy remains variable and often modest. In this study, a humanized anti-CD20 antibody, hu8E4, was generated by complementarity-determining region grafting method. Hu8E4 was as effective as rituximab in mediating antibody-dependent cellular cytotoxicity and inducing apoptosis in B-lymphoma cells, but it exhibited much more potent complement-dependent cytotoxicity than rituximab. Immunotherapeutic studies showed that hu8E4 was significantly more effective than rituximab in prolonging the survival of severe combined immunodeficient mice bearing human B-cell lymphomas, suggesting that it might be a promising therapeutic agent for B-cell lymphomas.

Purpose: CD11c is an antigen receptor predominantly expressed on dendritic cells (DC), to which antigen targeting has been shown to induce robust antigen-specific immune responses. To facilitate targeted delivery of tumor antigens to DCs, we generated fusion proteins consisting of the extracellular domain of human HER or its rat homologue neu, fused to the single-chain fragment variable specific for CD11c (scFvCD11c-HER2/neu). Experimental Design: Induction of cellular and humoral immune responses and antitumoral activity of the fusion proteins admixed with DC-activating CpG oligonucleotides (scFvCD11c-HER2/neuCpG) were tested in transplantable HER2/neu-expressing murine tumor models and in transgenic BALB-neuT mice developing spontaneous neu-driven mammary carcinomas. Results: Vaccination of BALB/c mice with scFvCD11c-HER2CpG protected mice from subsequent challenge with HER2-positive, but not HER2-negative, murine breast tumor cells, accompanied by induction of strong HER2-specific T-cell and antibody responses. In a therapeutic setting, injection of scFvCD11c-HER2CpG caused rejection of established HER2-positive tumors. Importantly, antitumoral activity of such a fusion protein vaccine could be reproduced in immunotolerant BALB-neuT mice, where scFvCD11c-neuCpG vaccination significantly protected against a subsequent challenge with neu-expressing murine breast tumor cells and markedly delayed the onset of spontaneous mammary carcinomas. Conclusions: CD11c-targeted protein vaccines for in vivo delivery of tumor antigens to DCs induce potent immune responses and antitumoral activities and provide a rationale for further development of this approach for cancer immunotherapy.

HuCD25mAb is a humanized anti-CD25 antibody which has the same amino acid sequence as daclizumab (Zenapax, Roche). HuCD25mAb is expressed in Chinese hamster ovary (CHO) cells while daclizumab is expressed in the NSO myeloma cell line. A comparative study was performed to evaluate the pharmacokinetics and pharmacodynamics between huCD25mAb and daclizumab in a two-dose regimen incorporating triple immunosuppressant treatment regimens (MMF, CsA and steroids). Fifteen patients were enrolled and randomized to receive intravenous infusion of either huCD25mAb (n = 10) or daclizumab (n = 5) at a dosage of 1 mg.kg(-1) on operation day 0 and post-operation day 14. Serum concentrations of huCD25mAb and daclizumab were measured by a validated competitive ELISA. Subgroups of CD3(+), CD25(+), CD4(+) and CD8(+) lymphocytes were monitored periodically by flow cytometry. The concentration-time curves of huCD25mAb and daclizumab were found to fit well to a one-compartment model. A significant decline of proportion (%) of CD3-CD25(+) and CD3(+)CD25(+) lymphocytes was observed 30 min after first infusion on day 0 (3.40 +/- 1.83 to 0.03 +/- 0.07, 3.35 +/- 2.02 to 0.37 +/- 0.49), and these levels remained low for at least 70 days (0.03 +/- 0.05, 0.31 +/- 0.47). All pharmacokinetic parameters of huCD25mAb seemed similar to those of daclizumab. The two-dose huCD25mAb regimen was as effective as daclizumab in rapidly achieving high therapeutic concentration in the treated patients, and a significant decrease of CD3(-)CD25(+) and CD3(+)CD25(+) lymphocytes was demonstrated. This suggests that two-dose regimen is feasible in maintaining host immunosuppression and may provide an effective and economical strategy for reducing incidence of acute graft rejection.

We reported previously the development of SMFv-PE38KDEL type I mutant (PE38KDEL-I; Mut-I), a recombinant immunotoxin in which a single-chain antibody derived from mouse SM5-1 monoclonal antibody is genetically fused to PE38KDEL-I. In comparison with the SMFv-PE38KDEL wild-type, Mut-I showed improved therapeutic efficacy and reduced toxicity. To overcome the problems associated with the immune response to the Pseudomonas exotoxin A (PE) component of Mut-I, we have constructed PE38KDEL-I-loaded poly(lactic-co-glycolic acid) nanoparticles conjugated with F(ab′) fragments of a humanized SM5-1 monoclonal antibody (PE-NP-S). PE-NP-S specifically bound to SM5-1 binding protein-expressing hepatocellular carcinoma cell lines and was then internalized by these cells, resulting in significant cytotoxic effect. In SM5-1 binding protein-overexpressing tumor xenograft model, administration of PE-NP-S significantly inhibited tumor development and induced tumor regression. Moreover, PE-NP-S was shown to be much weaker in inducing vascular leakage syndrome in mice than Mut-I. The LD50 of PE-NP-S was about 4-fold higher than that of Mut-I. Remarkably, PE-NP-S was of low immunogenicity in development of anti-PE neutralizing antibodies in vivo and was less susceptible to inactivation by anti-PE neutralizing antibodies compared with Mut-I. In conclusion, the resultant PE-NP-S possessed increased cancer therapeutic efficacy and had reduced nonspecific toxicity and immunogenicity, suggesting that it is a potential candidate in cancer therapy. [Mol Cancer Ther 2008;7(10):3399–407]

4C8 is a new mouse anti-human CD34 monoclonal antibody (mAb), which recognizes class II CD34 epitopes and can be used for clinical hematopoietic stem/progenitor cell selection. In an attempt to improve its safety profiles, we have developed a humanized antibody of 4C8 by complementarity-determining region (CDR) grafting method in this study. Using a molecular model of 4C8 built by computer-assisted homology modelling, framework region (FR) residues of potential importance to the antigen binding were identified. A humanized version of 4C8, denoted as h4C8, was generated by transferring these key murine FR residues onto a human antibody framework that was selected based on homology to the mouse antibody framework, together with the mouse CDR residues. The resultant humanized antibody was shown to possess antigen-binding affinity and specificity similar to that of the original murine antibody, suggesting that it might be an alternative to mouse anti-CD34 antibodies routinely used clinically.

Despite the widespread clinical use of CD34 antibodies for the purification of human hematopoietic stem/progenitor cells, all the current anti-human CD34 monoclonal antibodies (mAbs) are murine, which have the potential to elicit human antimouse antibody (HAMA) immune response. In the present study, we developed three new mouse anti-human CD34 mAbs which, respectively, belonged to class I, class II and class III CD34 epitope antibodies. In an attempt to reduce the immunogenicity of these three murine mAbs, their chimeric antibodies, which consisted of mouse antibody variable regions fused genetically to human antibody constant regions, were constructed and characterized. The anti-CD34 chimeric antibodies were shown to possess affinity and specificity similar to that of their respective parental murine antibodies. Due to the potentially better safety profiles, these chimeric antibodies might become alternatives to mouse anti-CD34 antibodies routinely used for clinical application.

The clinical use of Pseudomonas exotoxin A (PE)-based immunotoxins is limited by the toxicity and immunogenicity of PE. To overcome the limitations, we have developed PE38KDEL-loaded poly(lactic-co-glycolic acid) (PLGA) nanoparticles conjugated with Fab' fragments of a humanized anti-HER2 monoclonal antibody (rhuMAbHER2). The PE38KDEL-loaded nanoparticles-anti-HER2 Fab' bioconjugates (PE-NP-HER) were constructed modularly with Fab' fragments of rhuMAbHER2 covalently linked to PLGA nanoparticles containing PE38KDEL. Compared with nontargeted nanoparticles that lack anti-HER2 Fab', PE-NP-HER specifically bound to and were sequentially internalized into HER2 overexpressing breast cancer cells, which result in significant cytotoxicity in vitro. In HER2 overexpressing tumor xenograft model system, administration of PE-NP-HER showed a superior efficacy in inhibiting tumor growth compared with PE-HER referring to PE38KDEL conjugated directly to rhuMAbHER2. Moreover, PE-NP-HER was well tolerated in mice with a higher LD(50) (LD(50) of 6.86 +/- 0.47 mg/kg vs. 2.21 +/- 0.32 mg/kg for PE-NP-HER vs. PE-HER (mean +/- SD); n = 3), and had no influence on the plasma level of plasma alanine aminotransferase (ALT) of animals when injected at a dose of 1 mg/kg where PE-HER caused significant increase of serum ALT in the treated mice. Notably, PE-NP-HER was of low immunogenicity in development of anti-PE38KDEL neutralizing antibodies and was less susceptible to inactivation by anti-PE38KDEL antibodies compared with PE-HER. This novel bioconjugate, PE-NP-HER, may represent a useful strategy for cancer treatment.

Vascular leak syndrome (VLS) is the major dose-limiting toxicity of immunotoxin therapy. In our previous study, a modified PE38KDEL, denoted PE38KDELKQK, was engineered to eliminate VLS. The PE38KDELKQK-based immunotoxin has been proved to retain potent anti-tumor activity but with a remarkable attenuation in VLS. In the present study, we have constructed and expressed a recombinant immunotoxin CD25-PE38KDELKQK containing humanized anti-CD25 single-chain antibody (scFv) genetically fused to PE38KDELKQK in Escherichia coli. After washing with buffer containing 2 M urea, the purity of inclusion body was about 82%. The denatured inclusion bodies were refolded on-column in Tris buffer (pH 8.0) containing 4mM of GSH and 1 mM of GSSG using a gradient of decreasing urea. We found that the presence of GSH/GSSG (4:1) in the on-column refolding buffer was important for efficient refolding. In addition, slow flow rate was another important factor could increase refolding. Under these conditions, the activity of the refolded protein could reach about 90% of that of the native protein. The refolded proteins were purified to homogeneity ( approximately 95% purity) by a combination of His-Ni(2+) metal affinity chromatography and gel filtration chromatography. The in vitro cytotoxicity assay indicated the purified immunotoxin CD25-PE38KDELKQK had specific cytotoxicity to CD25-positive leukemic cells comparable to wild-type CD25-PE38KDEL (wt). In contrast, CD25-PE38KDELKQK was shown to be much weaker in inducing VLS in mice than wt. The protein expression, purification, and refolding system established in this paper is important for further study on immunotoxin CD25-PE38KDELKQK.

SM5-1 is a mouse monoclonal antibody which has a high specificity for melanoma, hepatocellular carcinoma, and breast cancer, making it a promising candidate for cancer targeting therapy. We have therefore attempted to construct a humanized antibody of SM5-1 to minimize its immunogenicity for potential clinical use. Using a molecular model of SM5-1 built by computer-assisted homology modeling, framework region (FR) residues of potential importance to the antigen binding were identified. Then, a humanized version of SM5-1 was generated by transferring these mouse key FR residues onto a human framework that was selected based on homology to the mouse framework, together with the mouse complementarity-determining region (CDR) residues. This humanized antibody retained only six murine residues outside of the CDRs but was shown to possess affinity and specificity comparable to that of the parental antibody, suggesting that it might have the potential to be developed for future clinical use.

Vascular leak syndrome (VLS) is the major dose-limiting toxicity of immunotoxin and interleukin-2 therapy. It has been evidenced that VLS-inducing molecules share a three-amino acid consensus motif, (x)D(y), which may be responsible for initiating VLS. Here we have constructed a recombinant immunotoxin (SMFv-PE38KDEL) by genetically fusing PE38KDEL to a single-chain antibody derived from SM5-1 monoclonal antibody, which has a high specificity for melanoma, hepatocellular carcinoma and breast cancer. In order to eliminate VLS induced by this PE38KDEL-based immunotoxin, a panel of mutants were generated by changing amino acid residues adjacent to its three (x)D(y) motifs in the three-dimensional structure. One of the SMFv-PE38KDEL mutants, denoted as mut1, displayed a similar protein synthesis inhibitory in a reticulocyte lysate translation assay compared to the wild-type SMFv-PE38KDEL (wt). The in vitro cytotoxicity assay indicated that mut1 specifically killed SM5-1 binding protein-positive tumor cells, although its cytotoxicity was slightly less than wt. In contrast, mut1 was shown to be much weaker in inducing VLS in mice than wt. The LD(50) values of wt and mut1 in mice were investigated with the result that the LD(50) of mut1 was about tenfold higher than that of wt. The in vivo antitumor activity of wt and mut1 were also compared in tumor-bearing nude mice. Both wt and mut1 were effective in inhibiting the tumor growth but mut1 showed improved therapeutic efficacy. These studies suggest mut1 may be a novel PE-based immunotoxin with much less toxicity for clinical use.

We developed a recombinant defective adenovirus with an insert of gene encoding extracellular domain of mouse Flt3L (Ad-mFlt3L) under control of cytomegalovirus promoter to investigate the biological efficacy of Flt3L in combination with chemotherapeutical drug, 5-FU, in eliciting an effective anti-cancer immunity in mouse hepatoma and colon cancer model systems. The constructed Ad-mFlt3L efficiently infected hepatoma and colon cancer cells both in vitro and in vivo, leading to a high production of mFlt3L proteins in association with accumulation of DCs, NK cells and lymphocytes in local tumor tissues. Administration of Ad-mFlt3L can protect bone marrow injury caused by 5-Fu and stimulates proliferation and maturation of lymphocytes, APCs and NKs. Intratumoral injection of Ad-mFlt3L followed by an intraperitoneal administration of 5-Fu significantly inhibited tumor growth and cured established tumors. Adenovirus mediated Flt3L gene therapy synergies with chemotherapeutic drug, 5-Fu, in elicitation of long-lasting antitumor immunity. The tumor specific immunity can be adoptively transferred into naive animals successfully by transfusion of CD3+CD8+ T cells from the treated mice. The data suggests that adenovirus mediated Flt3L gene therapy in combination with 5-Fu chemotherapy may open a new avenue for development of anti-cancer chemogenetherapy.

Dendritic cells (DCs)-based immunotherapy represents an approach to the prevention and treatment of cancers. Targeting antigens to receptors on DCs can be expected to enhance immune response. We have constructed an expression vector pET32a(+)-ScFv(CD11c)-TRP2 based on a single-chain antibody fragment (ScFv) that targets the high affinity receptor CD11c which is expressed on murine DCs. The 3'-terminal end of the ScFv was ligated to the gene for MHC class I molecule-recognized peptide from mouse tyrosine-related protein 2 (TRP2). Using this vector, we have expressed and purified ScFv(CD11c)-TRP2, a fusion protein that could target TRP2 peptide to CD11c on DCs in vivo to elicit anti-tumor responses. This fusion protein was expressed in inclusion bodies in Escherichia coli BL21(DE3) and was refolded and purified on-column effectively by immobilized metal affinity chromatography using His-tag. Flow cytometry assays showed the specific binding ability of ScFv(CD11c)-TRP2 to DCs, which could be blocked by a hamster anti-mouse CD11c produced by N418 hybridoma. Further studies demonstrated that ScFv(CD11c)-targeted TRP2 peptide processed by DCs was capable of stimulating T cells proliferation. Thus, this fusion protein provides a basis for further research in cancer therapy in vivo.

12F6 is a murine anti-human CD3 monoclonal antibody, which competes with OKT3 for binding to human T cells and possesses more effective T-cell suppression and activation properties compared to OKT3. It thus exhibits the potential to be developed as an immunoregulation agent for manipulating T-cell functions and preventing acute allograft rejection. In an attempt to minimize the immunogenicity of murine 12F6 (m12F6) for potential clinical application, a humanized version of 12F6, denoted as hu12F6, was successfully constructed by complementary determining region (CDR) grafting and shown to maintain both T-cell activation and suppression activities similar to m12F6. Furthermore, in order to reduce the first dose reaction syndrome caused by T-cell activation following the first administration of anti-CD3 antibodies, two amino acid mutations were introduced into the Fc region of hu12F6, resulting in the Fc-mutated 12F6 humanized antibody (hu12F6mu). This Fc-mutated version displayed a similar antigen-binding affinity and specificity compared with hu12F6 and m12F6 but with much weaker FcR binding activity. hu12F6mu was shown to be much less potent in the induction of T-cell proliferation, cytokine release (tumour necrosis factor-alpha, interferon-gamma and interleukin-10) and early activation marker expression on the cell surface (CD69 and CD25) than parental 12F6 and OKT3 did. In contrast, hu12F6mu was effective in modulating T-cell receptor/CD3 and inhibiting mixed lymphocyte reaction with a similarity as compared to m12F6 and OKT3. In conclusion, the resultant hu12F6mu was much less mitogenic to T cells but retained potent immunosuppression, suggesting it might be an alternative to OKT3 as an immunosuppressive drug with less immunogenicity and toxicity for clinical application.