The effect of combining Endostar with radiotherapy on blood vessels, tumor-associated macrophages, and T cells in brain metastases of Lewis lung cancer.

Background: Combining Endostar (ES) with radiotherapy (RT) has shown a promising therapeutic effect on non-small cell lung carcinoma with brain metastases (BMs) in clinical practice. However, the specific mechanism is not yet fully understood. The present study aimed to investigate the effects of ES on blood vessels, tumor-associated macrophages (TAMs), and T cells in a tumor microenvironment treated with RT. Methods: BM models were established by stereotactic and intracarotid injection of luciferase-Lewis lung cancer (LLC) cells into female C57BL mice. The animals were randomly divided into 4 groups: normal saline (NS), ES, RT, and ES plus radiotherapy (ES + RT) groups. Tumor size was determined with the IVIS imaging system. Tumor specimens were stained with CD34 and a-SMA to investigate tumor vascular changes. The proportions of TAMs, CD4(+) T cells, and CD8(+) T cells in tumor tissues were determined by flow cytometry and immunofluorescence. The expressions of hypoxia-inducible factor 1 alpha (HIF-1 alpha) and CXCR4 were deduced using western blotting and immunohistochemistry (IHC). Results: ES + RT significantly suppressed tumor growth compared to the other 3 groups. RT decreased M1 and increased M2 in microglial cells and bone marrow-derived macrophages (BMDMs) relative to NS, while ES had the opposite effect. The ratio of CD8(+)T/CD4(+)T was increased in the ES + RT group compared to the other 3 groups. Tumor vascular maturity (alpha-SMA(+)/CD34(+)) was increased while HIF-1a was significantly suppressed in the ES + RT group. CXCR4 expression, which is involved in TAM recruitment, increased following RT, whereas, ES attenuated its expression. Conclusions: Our findings suggest that ES can promote the normalization of tumor blood vessels and increase the anti-tumor immune-related immune cells infiltrating the tumor following RT treatment.