Oridonin inhibits tumor angiogenesis and induces vessel normalization in experimental colon cancer

Purpose: Tumor blood vessels exhibit morphological and functional aberrancies. Its maturity and functionality are closely associated with colon cancer progression and therapeutic efficacy. The direct evidence proving whether oridonin (ORI) has vascular normalization promoting effect from which combination therapies will benefit is still lacking. Methods: We established a subcutaneous xenograft model of human colon cancer. The animals were divided into the Control and ORI-treated groups. Immunohistochemical analysis and TUNEL staining was applied to evaluate the proliferation, apoptosis and angiogenesis. Western blot analysis was employed to characterize the angiogenesis-related factors and JAK2/STAT3 signaling. Then, vascular normalization and macrophage reprogramming were assessed by immunofluorescence analysis. Results: The results showed that ORI obviously reduced tumor growth, diminished the numbers of Ki67⁺ cells and CD31⁺ microvessel density, while increased the numbers of TUNEL⁺ cells. The expression levels of VEGF and bFGF proteins were dramatically down-regulated while the angiostatin and endostatin levels were increased in the ORI-treated group. Moreover, ORI therapy remarkably promoted the pericyte coverage of tumor vessels from days 5 to 10, with the highest pericyte coverage rate occurred at day 7. In the time window of vascular normalization, hypoxia of the tumor microenvironment was improved by ORI, the expression of HIF-1a was downregulated. Moreover, CD206⁺ macrophage cells were diminished in the ORI-treated group. These anticancer effects of ORI maybe partly mediated by suppressing JAK2/STAT3 signaling pathway. Conclusions: These results highlight the potential effect of ORI on anti-angiogenesis and inducing vessel normalization roles of ORI, and probably provide optimum time point for the ORI therapy in conjunction with the chemoradiotherapy or immunotherapy.