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[Tumor-associated macrophages in tumor neovascularization--in situ ultrastructural cytochemical and quantitative
1Department of Ultrastructural Pathology, Nanjing General Hospital, PLA.
Abstract:
Relation of tumor-associated macrophages to tumor neovascularization in murine transplanted tumor, sarcoma 180(S180), was quantitatively analysed in situ on days 3, 6 and 9 after tumor implantation. Infiltrating macrophages in tumor were identified in paraffin section by alpha-naphthyl butyrate esterase stain and subdivided by electron microscopy according to the peroxidase activity. Simultaneously, the structure of newly formed microvessels was quantitated under light microscope by stereological morphometry. The results showed that, as the tumor grew and blood vessels proliferated, the number of infiltrating macrophages in tumor increased obviously but the ratio of peroxidase (PO) positive mononuclear phagocytes tended to decrease in contrast to the increase of PO-negative phagocytes. Microvasculature volume was found to be positively correlated to the proportion of PO-negative macrophages but negatively correlated to the proportion of PO-positive mononuclear phagocytes. It was indicated that tumor angiogenesis was related to the mature macrophages in the tumor.
Insights
Tumor-associated macrophages influence new blood vessel growth in sarcoma. Mature macrophages correlate with increased tumor vascularization, suggesting a role in tumor angiogenesis.
Area of Science:
- Immunology
- Oncology
- Cell Biology
Context:
- Tumor growth relies on neovascularization, the formation of new blood vessels.
- Tumor-associated macrophages (TAMs) are immune cells found in tumors that can influence various aspects of cancer progression.
- Understanding the specific roles of different TAM subsets in neovascularization is crucial for developing targeted therapies.
Purpose:
- To quantitatively analyze the relationship between tumor-associated macrophages and tumor neovascularization in a murine sarcoma model.
- To investigate how different subsets of macrophages, distinguished by peroxidase activity, correlate with microvessel formation.
Summary:
- Infiltrating macrophages and microvessel structures were analyzed in sarcoma 180 tumors at different time points.
- The study found an increase in total macrophages as tumors grew, but a decrease in peroxidase-positive (PO+) macrophages and an increase in peroxidase-negative (PO-) macrophages.
- Microvasculature volume was positively correlated with PO-macrophages and negatively correlated with PO+ macrophages, indicating mature macrophages promote angiogenesis.
Impact:
- This research suggests that mature macrophages (PO-) play a significant role in promoting tumor angiogenesis.
- The findings could inform the development of novel anti-cancer strategies targeting macrophage subsets to inhibit tumor vascularization.
