Zhenyu Ding

A gene therapy for cancer based on the angiogenesis inhibitor, vasostatin

The growth and persistence of solid tumors and their metastasis are angiogenesis-dependent. Vasostatin, the N-terminal domain of calreticulin inclusive of amino acids 1–180, is a potent angiogenesis inhibitor. To investigate whether intramuscular administration of vasostatin gene has the antitumor activity in mouse tumor models, we constructed a plasmid DNA encoding vasostatin and a control vector. Production and secretion of vasostatin protein by COS cells transfected with the plasmid DNA encoding vasostatin (pSecTag2B-vaso) were confirmed by Western blot analysis and ELISA. Conditioned medium from vasostatin-transfected COS cells apparently inhibited human umbilical vein endothelial cell (HUVEC) and mouse endothelial cell (SVEC4-10) proliferation, compared with conditioned medium from the COS cells transfected with control vector or non-transfected cells. Treatment with pSecTag2B-vaso twice weekly for 4 weeks resulted in the inhibition of tumor growth and the prolongation of the survival of tumor-bearing mice. The sustained high level of vasostatin protein in serum could be identified in ELISA. Angiogenesis was apparently inhibited in tumor by immunohistochemical analysis. Angiogenesis was also inhibited in the chicken embryo CAM assay and mouse corneal micropocket assay. The increased apoptotic cells were found within the tumor tissues from the mice treated with plasmid DNA encoding vasostatin. Taken together, the data in the present study indicate that the cancer gene therapy by the intramuscular delivery of plasmid DNA encoding vasostatin, is effective in the inhibition of the systemic angiogenesis and tumor growth in murine models. The present findings also provide further evidence of the anti-tumor effects of the vasostatin, and may be of importance for the further exploration of the application of this molecule in the treatment of cancer.

Improved Therapeutic Effectiveness by Combining Recombinant CXC Chemokine Ligand 10 with Cisplatin in Solid Tumors

Purpose: CXC chemokine ligand 10 (CXCL10) is a potent inhibitor of angiogenesis. We wonder whether the combination of CXCL10 with cisplatin would improve the therapeutic antitumor efficacy. Experiment Design: We evaluated the antitumor activity of the combination therapy in the immunocompetent C57BL/6 and BALB/c mice bearing LL/2 Lewis lung cancer and CT26 colon adenocarcinoma, respectively. Mice were treated with either CXCL10 s.c. at 25 μg per kg per day once daily for 30 days, cisplatin cycled twice (5 mg/kg i.p. on days 14 and 21 after the initiation of CXCL10), or both agents together. Tumor volume and survival time were observed. Antiangiogenesis of CXCL10 in vivo were determined by alginate capsule models and CD31 immunohistochemistry. Histologic analysis and assessment of apoptotic cells were also conducted in tumor tissues. Results: CXCL10 + cisplatin reduced tumor growth in LL/2 and CT26 tumor model, respectively, more effectively, although cisplatin or CXCL10 individually resulted in suppression of tumor growth and improved survival time of tumor-bearing mice. CXCL10 successfully inhibited angiogenesis as assessed by alginate model and CD31 (P < 0.05). Histologic analysis of tumors exhibited that CXCL10 in combination with cisplatin led to the increased rate of apoptosis, tumor necrosis, and elevated lymphocyte infiltration. Conclusions: Our data suggest that the combination of CXCL10, a well-tolerated angiogenesis inhibitor, with cisplatin can enhance the antitumor activity. The present findings may be of importance to the further exploration of the potential application of this combined approach in the treatment of lung and colon carcinoma.

Active immunotherapy of tumors with a recombinant xenogeneic endoglin as a model antigen

Angiogenesis play a critical role in tumor growth and metastasis. Increasing evidence suggests that endoglin is a powerful marker of angiogenesis in solid malignancies. Thus, breaking of immune tolerance of self‐endoglin‐associated angiogenesis is an attractive approach to cancer therapy. To test this concept, we recombined the extracellular domains of porcine endoglin, and used it as a xenogeneic vaccine. We found that immunotherapy with porcine endoglin was effective at both protective and therapeutic anti‐tumor immunity in several mouse tumor models. Autoantibodies against mouseendoglin were identified by Western blot and ELISA. IgG1 and IgG2b were substantially increased. Anti‐endoglin antibody‐producing B cells were detectable by ELISPOT assay. There was endothelial deposition of immunoglobulins within tumors. The anti‐tumor activity was also induced by the adoptive transfer of the purified immunoglobulins. Angiogenesis was apparently inhibited within the tumor tissues and on the alginate beads. The increased apoptotic cells were found within the tumor tissues from the mice treated with porcine endoglin. The anti‐tumor activity and production of autoantibodies againstmouse endoglin could be abrogated by depletion of CD4+ T lymphocytes. Remarkably, no marked toxicity was found in the immunized mice. These observations may provide an alternative rationalstrategy for active cancer immunotherapy.

Combination of low‐dose cisplatin and recombinant xenogeneic endoglin as a vaccine induces synergistic antitumor activities

Angiogenesis is critical to the growth and metastasis of solid tumors, and acquired drug resistance is one of the major hindrances to chemotherapy. Thus, we sought a rational strategy using the combination of antiangiogenic biotherapy and chemotherapy for cancer therapy. We explored the efficacy of a strategy combining low‐dose cisplatin and a recombinant xenogeneic endoglin as a protein vaccine, which we previously demonstrated to have effective antiangiogenic effects in several mouse models. We found that both low‐dosage cisplatin and xenogeneic endoglin vaccine individually resulted in effective suppression of tumor growth in 2 tumor models via inhibition of tumor angiogenesis. Remarkably, the combination therapy resulted in not only significant antiangiogenic effects but also additional promotion of tumor cell apoptosis and inhibition of tumor cell proliferation, without any ensuing increase in host toxicity during the course of treatment, which lasted for 6 months. In addition, the combination demonstrated a synergistic relationship, which was shown in all of the synergistic indexes, i.e., tumor volume, angiogenesis, apoptosis and proliferation. Both antibodies and antibody‐producing B cells against mouse self‐endoglin were observed in all mice immunized by the xenogeneic endoglin vaccine (alone and combination), which suggested that low‐dose cisplatin did not suppress the host immune response but potentiated the antitumor activity of the xenogeneic endoglin vaccine. These observations may provide the basis for an effective alternative strategy for cancer therapy in the near future.

Synergistic anti-tumor effect of recombinant human endostatin adenovirus combined with gemcitabine.

Endostatin is an important endogenous inhibitor of neovascularization, which has been widely used in anti-angiogenesis therapy for cancer. To fully explore the potential of endostatin, we evaluated the anti-tumor efficacy of the combination of recombinant human endostatin adenovirus and low-dose gemcitabine in nude mice. We injected recombinant human endostatin adenovirus intratumorally plus a low dose of gemcitabine i.p. routinely. The combination treatment produced no side-effects, and resulted in marked suppression in tumor formation and growth of established human lung carcinoma xenografts in nude mice, with decreased microvessel density and increased apoptosis percentage. Our data support the idea of synergistic anti-tumor properties of endostatin plus low-dose chemotherapy against human lung cancer in vivo.

Induction of apoptosis and tumor regression by vesicular stomatitis virus in the presence of gemcitabine in lung cancer

Vesicular stomatitis virus (VSV) has been shown to replicate rapidly in vitro and kill selectively a variety of tumor cell lines. The present study was designed to determine whether gemcitabine potentiates the antitumor activity of VSV in vitro and in vivo. A549 human lung adenocarcinoma cells and LLC Lewis lung carcinoma cells were treated with VSV (0.1–10 plaque‐forming units per cell) plus gemcitabine (20 nM to 20 μM). Mice bearing A549 or LLC were treated with VSV (5 × 104 to 1 × 108 plaque‐forming units) daily for 5 days plus gemcitabine (5–125 mg/kg/day) once every 3 days for 4 times. Induction of apoptosis and effects on growth inhibition were assessed. The lung cancer cells treated with VSV plus gemcitabine displayed the apparently increased apoptotic cells compared with treatment with VSV or gemcitabine alone. The combined treatment with VSV plus gemcitabine induced the apparent antitumor activity with complete regression of the established lung cancer in both A549 and LLC lung cancer models and augmented the induction of apoptosis in lung cancer cells in vivo as well. This study suggests that the combined treatment with VSV plus gemcitabine may augment the induction of apoptosis in lung cancer cells in vitro and in vivo, and that the augmented antitumor activity in vivo may result from the increased induction of apoptosis in lung cancer cells. The present findings may be of importance to the further exploration of the potential application of this combined approach in the treatment of lung cancer.

A promising cancer gene therapy agent based on the matrix protein of vesicular stomatitis virus

The matrix (M) protein of vesicular stomatitis virus (VSV) plays a key role in inducing cell apoptosis during infection. To investigate whether M protein‐mediated apoptosis could be used in cancer therapy, its cDNA was amplified and cloned into eukaryotic expression vector pcDNA3.1(+). The recombinant plasmid or the control empty plasmid pcDNA3.1(+) was mixed with cationic liposome and introduced into various tumor cell lines in vitro, including lung cancer cell LLC, A549, colon cancer cell CT26 and fibrosarcoma cell MethA. Our data showed that the M protein induced remarkable apoptosis of cancer cells in vitro compared with controls. Fifty micrograms of plasmid in a complex with 250 μg cationic liposome was injected intratumorally into mice bearing LLC or MethA tumor model every 3 days for 6 times. It was found that the tumors treated with M protein plasmid grew much more slowly, and the survival of the mice was significantly prolonged compared with the mice treated with the control plasmid. In MethA fibrosarcoma, the tumors treated with M protein plasmid were even completely regressed, and the mice acquired longtime protection against the same tumor cell in rechallenge experiments. Both apoptotic cells and CD8+ T cells were widely distributed in M protein plasmid‐treated tumor tissue. Activated cytotoxic T lymphocytes (CTLs) were further detected by means of 51Cr release assay in the spleen of the treated mice. These results showed that M protein of VSV can act as both apoptosis inducer and immune response initiator, which may account for its extraordinary antitumor effect and warrant its further development in cancer gene therapy.— Zhao, J., Wen, Y., Li, Q., Wang, Y., Wu, H., Xu, J., Chen, X., Wu, Y., Fan, L., Yang, H., Liu, T., Ding, Z., Du, X., Diao, P., Li, J., Wu, H., Kan, B., Lei, S., Deng, H., Mao, Y., Zhao, X., Wei, Y. A promising cancer gene therapy agent based on the matrix protein of vesicular stomatitis virus. FASEB J. 22, 4272–4280 (2008)

Immunotherapy of Tumors with Protein Vaccine Based on Chicken Homologous Tie-2

Purpose: Tie-2 is an endothelium-specific receptor tyrosine kinase known to play a key role in tumor angiogenesis. The present study explores the feasibility of immunotherapy of tumors by using a protein vaccine based on chicken Tie-2 as a model antigen to break the immune tolerance against Tie-2 in a cross-reaction between the xenogeneic homologous and self-Tie-2. Experimental Design and Results: In this study, a chicken homologous Tie-2 protein vaccine (chTie-2) and a corresponding mouse Tie-2 vaccine as a control were prepared and the antitumor effect of these vaccines was tested in two tumor models (murine B16F10 melanoma and murine H22 hepatoma). Immunotherapy with chTie-2 was found effective in two tumor models. Autoantibodies against mouse Tie-2 were detected in sera of mice immunized with chTie-2 through Western blot analysis and ELISA assay. Anti-Tie-2 antibody-producing B cells were detectable by ELISPOT. Histologic examination revealed that autoantibodies were deposited on the endothelial cells of tumor tissues. Purified immunoglobulins from chTie-2-immunized mice could induce the apoptosis of human umbilical vein endothelial cells in vitro. Importantly, adoptive transfer of purified immunoglobulins led to antitumor effect in vivo; apparently, angiogenesis was significantly inhibited in these tumors. Furthermore, the antitumor activity and production of autoantibodies could be abrogated by depletion of CD4+ T lymphocytes. Conclusions: Our findings may provide a vaccine strategy for cancer therapy and show the potential utilization of interference with Tie-2 pathway.

Improved therapeutic efficacy against murine carcinoma by combining honokiol with gene therapy of PNAS-4, a novel pro-apoptotic gene.

PNAS‐4, a novel pro‐apoptotic gene activated during the early response to DNA damage, can inhibit proliferation via apoptosis when overexpressed in some tumor cells. Recent studies have indicated that honokiol can induce apoptosis, inhibit angiogenesis, and suppress tumor growth. In the present study, we investigated whether mouse PNAS‐4 (mPNAS‐4) could augment the apoptosis of tumor cells induced by honokiol in vitro, and whether the antiangiogenic activity of honokiol and induction of apoptosis by mPNAS‐4 could work cooperatively to improve the antitumor efficacy in vivo. In vitro, mPNAS‐4 inhibited proliferation of murine colorectal carcinoma CT26 and Lewis lung carcinoma LL2 cells through induction of apoptosis, and significantly augmented the apoptosis of CT26 and LL2 cells induced by honokiol. Compared with treatment with mPNAS‐4 or honokiol alone, in vivo systemic administration of an expression plasmid encoding mPNAS‐4 and low‐dose honokiol significantly suppressed tumor growth through the enhanced induction of apoptosis and the augmented inhibition of angiogenesis. Our data suggest that the combined treatment with mPNAS‐4 plus honokiol augments antitumor effects in vitro and in vivo, and that the improved antitumor activity in vivo may be associated with enhanced induction of apoptosis and augmented inhibition of angiogenesis. The present study may provide a novel and effective method for the treatment of cancer. (Cancer Sci 2009; 100: 1757–1766)

Vesicular stomatitis virus matrix protein gene enhances the antitumor effects of radiation via induction of apoptosis

Vesicular stomatitis virus (VSV) matrix (M) protein can directly induce apoptosis by inhibiting host gene expression when it is expressed in the absence of other viral components. Previously, we found that the M protein gene complexed to DOTAP-cholesterol liposome (Lip-MP) can suppress malignant tumor growth in vitro and in vivo; however, little is known regarding the biological effect of Lip-MP combined with radiation. The present study was designed to determine whether Lip-MP could enhance the antitumor activity of radiation. LLC cells treated with a combination of Lip-MP and radiation displayed apparently increased apoptosis compared with those treated with Lip-MP or radiation alone. Mice bearing LLC or Meth A tumors were treated with intratumoral or intravenous injections of Lip-MP and radiation. The combined treatment significantly reduced mean tumor volumes compared with either treatment alone in both tumor models and prolonged the survival time in Meth A tumor models and the intravenous injection group of LLC tumor models. Moreover, the antitumor effects of Lip-MP combined with radiation were greater than their additive effects when compared with the expected effects of the combined treatment in vivo. This study suggests that Lip-MP enhanced the antitumor activity of radiation by increasing the induction of apoptosis.