Roles of macrophages in tumor development: a spatiotemporalperspective

摘要

Macrophages are critical regulators of tissue homeostasis but are also abundant in the tumor microenvironment (TME). In bothprimary tumors and metastases, such tumor-associated macrophages (TAMs) seem to support tumor development. While we knowthat TAMs are the dominant immune cells in the TME, their vast heterogeneity and associated functions are only just beingunraveled. In this review, we outline the various known TAM populations found thus far and delineate their specialized rolesassociated with the main stages of cancer progression. We discuss how macrophages may prime the premetastatic niche to enablethe growth of a metastasis and then how subsequent metastasis-associated macrophages can support secondary tumor growth.Finally, we speculate on the challenges that remain to be overcome in TAM research.