[Frontiers in Bioscience S4, 787-798, January 1, 2012]

The Role of tumor-associated macrophage in tumor progression

Koji Fukuda1, Aya Kobayashi1 , Kounosuke Watabe1

1Department of Medical Microbiology, Immunology and Cell Biology, Southern Illinois University, School of Medicine, 751 N Rutledge St. PO Box 19626, Springfield, IL 627794-9626, USA


1. Abstract
2. Introduction
3. Monocyte recruitment and M1/M2 polarization
3.1. Monocyte recruitment
3.2 .Differential functions of M1 and M2 macrophages
3.3. TAM resemble M2 macrophage
4. How does TAM stimulate tumor progression?
4.1. TAM promote both angiogenesis and lymphangiogenesis
4.2. TAM suppress anti-tumor immune responses
4.3. TAM promote invasion and metastasis of tumor
5. The role of TAM in tumor stem cells
6. Clinical implication
7. Conclusions and future directions
8. Acknowledgement
9. References


The tumor progression is not only regulated by metastasis promoting and suppressing genes in cancer cells but it is also strongly influenced by the interaction between cancer cells and the stromal cells. An abundance of inflammatory mediators and leukocytes has been known to promote cancer metastasis, and tumor associated macrophages (TAM) are the key players in the link between inflammation and cancer. TAM are derived from peripheral blood monocytes that are recruited into the tumor by inflammatory chemokines. Upon activation by cancer cells, TAM gain the ability of pro-tumoral functions including expression of various growth factors, promotion of angiogenesis and suppression of adaptive immunity, and many of these factors also play critical roles in cancer metastasis. In this review, we will summarize the recent information about the function of TAM in the inflammatory micro-environment of solid tumors and discuss the potential targets for future therapeutic approaches.