Radiation and Endostatin Gene Therapy in a Lung Carcinoma Model: Pilot Data on Cells and Cytokines that Affect Angiogenesis and Immune Status

Recombinant human endostatin combined with radiotherapy inhibits colorectal cancer growth

BACKGROUND

To examine the effects of recombinant human endostatin combined with radiotherapy on colorectal cancer HCT-116 cell xenografts in nude mice.

METHODS

Forty male BALB/c nude mice were injected with human colorectal cancer HCT-116 cells to form xenografts and then randomized into the following 4 groups (each group comprised ten mice): a control group, an endostatin group (20 mg/kg endostatin once a day for 10 days), a radiotherapy group (a 6-Gy dose was administered via a 6-MV X-ray on day 5 post-inoculation), and a combination therapy group (radiotherapy with endostatin treatment). The tumor growth inhibition rate were detected. CD31, vascular endothelial growth factor (VEGF), and hypoxia inducible factor-1α (HIF-1α) expression and microvascular density (MVD) were evaluated by immunohistochemistry. The expression of VEGF protein was also detected by western blotting.

RESULTS

The tumor growth inhibition rate in the radiotherapy with endostatin treatment group was significantly higher than those in endostatin group or radiotherapy group (77.67% vs 12.31% and 38.59%; n = 8 per group, P < 0.05). The results of immunohistochemistry showed that treatment with radiotherapy induced significant increases in CD31, VEGF, and HIF-1α expression and MVD compared with treatment with saline, while treatment with endostatin or radiotherapy with endostatin induced reductions in CD31, VEGF, and HIF-1α expression and MVD compared with treatment with saline (n = 8 per group, P < 0.05). The results of western blotting showed that VEGF protein expression in radiotherapy group was significantly increased compared with that in the control group. However, VEGF protein expression in the endostatin or radiotherapy with endostatin groups was significantly decreased compared with that in the control group (n = 8 per group, P < 0.05).

CONCLUSIONS

Endostatin combined with radiotherapy can significantly inhibit HCT-116 cell xenograft growth, possibly by inhibiting angiogenesis and attenuating tumor cell hypoxia.

Inhibitory effect of endostatin gene therapy combined with phosphorus-32 colloid on tumour growth in Wistar rats

Eighty healthy male Wistar rats, aged 5 weeks, weighing 100–120 g, were utilized for establishing tumour-bearing models by immediate Walker-256 cancerous ascites injection and randomly divided to four groups (n=20) treated with 0.2 ml solution containing saline, ³²P-colloid (0.3 mCi), endostatin gene (20 μg), endostatin gene combined with colloid ³²P. The effect of endostatin combined with a small dose of ³²P-colloidal on tumour growth in vivo was evaluated and the potential mechanism underlying the combined therapy was explored. We found that ³²P-colloid combined with endostatin exhibited higher inhibitory effect upon tumour growth compared with application of ³²P-colloid or endostatin alone, although three therapies all significantly inhibited tumour growth compared with saline control group. The higher inhibitory effect of ³²P-colloid combined with endostatin upon tumour growth might be attributed to a synergistic effect of inhibiting angiogenesis by endostatin and inducing apoptosis by ³²P-colloid, as demonstrated by microvessel density (MVD) and apoptotic index (AI) measurement. Combined therapy of ³²P-colloid and endostatin probably serves as a novel and efficacious therapy of tumour growth.

Antitumor activity of Endostar combined with radiation against human nasopharyngeal carcinoma in mouse xenograft models

Radiation treatment for nasopharyngeal carcinoma (NPC) is common and effective. However, local recurrence occurs frequently. Endostar, a novel recombinant human endostatin, is an antiangiogenic drug with a potent antitumor effect. The present study aimed to observe and explore the radiosensitization effects of Endostar on NPC and its underlying mechanism. The NPC subcutaneous transplantation tumor animal model was established to evaluate the antitumor activity of Endostar combined with radiation (Endostar + radiation) treatment compared with monotherapy (Endostar or radiation). Tumor growth and tumor weight were measured to evaluate the antitumor effect. The level of vascular endothelial growth factor (VEGF) and microvessel density (MVD) were measured using immunohistochemical staining of the tumor tissues. Significant antitumor activity was found in the Endostar + radiation group. The tumor inhibition rates of Endostar, radiation and Endostar + radiation were 27.12, 60.45 and 86.11%, respectively. The VEGF levels in the tumor tissue in the Endostar + radiation group were lower than those in the radiation and control groups. The MVD in the tumor tissues in the Endostar + radiation group was 12.2±2.5, lower than that in the Endostar (29.3±3.4), radiation (23.5±3.6) and control (44.7±5.1) groups. These results suggest that Endostar increases the radiation sensitivity of NPC-transplanted tumors in nude mice by lowering VEGF expression. In this study, the NPC animal model was established, which reflects the efficacy of clinical combination therapies and the combination of Endostar and radiation. The mechanisms of the combination therapies should be further investigated using this model.

Inhibitory effect of endostar in combination with radiotherapy in a mouse model of human CNE2 nasopharyngeal carcinoma

The inhibitory effects of Endostar in combination with radiotherapy in BALB/c nude mice model of human CNE2 nasopharyngeal carcinoma and the mechanism were investigated. In nude mice model of CNE2 nasopharyngeal carcinoma, the inhibitory rate and the sensitizing enhancement ratio (E/O) were calculated according to the tumor volumes in different groups. The expression of microvascular density (MVD) in tumor tissues was examined by using immunohistochemistry staining. The transcription of VEGF gene was detected by using RT-PCR. The inhibitory rate in Endostar+ radiotherapy group was higher than in other groups. In Endostar+radiotherapy group, the tumor volume was significantly decreased and the E/O ratio was 2.335, suggesting that Endostar could be a radiosensitizer. The expression of MVD of tumor tissues in Endostar+radiotherapy group was reduced significantly. The expression of the MVD in treatment groups was significantly different from that in control group (P<0.05). Compared to other groups, VEGF mRNA expression in Endostar+radiotherapy group was decreased remarkably. Endostar in combination with radiotherapy significantly inhibited the growth of CNE2 tumor. The combination therapy decreased the expression of VEGF, and inhibited tumor angiogenesis and proliferation. When combined with radiotherapy, Endostar acted as a radiosensitizer.

Future prospects and challenges of antiangiogenic cancer gene therapy

In 1971 Judah Folkman proposed the concept of antiangiogenesis as a therapeutic target for cancer. More than 30 years later, concept became reality with the approval of the antivascular endothelial growth factor (VEGF) monoclonal antibody bevacizumab as a first-line treatment for metastatic colorectal cancer. Monoclonal antibodies and small molecular drugs are the most widely applied methods for inhibition of angiogenesis. The efficacy of these antiangiogenic modalities has been proven, in both preclinical and clinical settings. Although angiogenesis plays a major role in wound healing, hypoxia, and in the female reproductive cycle, inhibition of angiogenesis seems to be a relatively safe therapeutic option against cancers, and has therefore become a logical arena for a wide range of experimentation. The twentieth century has shown the boom of gene therapy and thus it has been applied also in the antiangiogenic setting. This review summarizes methods to induce antiangiogenic responses with gene therapy and discusses the obstacles and future prospects of antiangiogenic cancer gene therapy.