Role of macrophages in tumor progression and therapy (Review)

Abstract

The number and phenotype of macrophages are closely related to tumor growth and prognosis. Macrophages are recruited to (and polarized at) the tumor site thereby promoting tumor growth, stimulating tumor angiogenesis, facilitating tumor cell migration, and creating a favorable environment for subsequent colonization by (and survival of) tumor cells. These phenomena contribute to the formation of an immunosuppressive tumor microenvironment (TME) and therefore speed up tumor cell proliferation and metastasis and reduce the efficacy of antitumor factors and therapies. The ability of macrophages to remodel the TME through interactions with other cells and corresponding changes in their number, activity, and phenotype during conventional therapies, as well as the association between these changes and drug resistance, make tumor-associated macrophages a new target for antitumor therapies. In this review, advantages and limitations of the existing antitumor strategies targeting macrophages in Traditional Chinese and Western medicine were analyzed, starting with the effect of macrophages on tumors and their interactions with other cells and then the role of macrophages in conventional treatments was explored. Possible directions of future developments in this field from an all-around multitarget standpoint were also examined.

Nocardia rubra cell wall skeleton regulates tumour‐associated macrophage polarization by reprogramming M2 macrophages into M1 macrophages via STAT1/STAT6 pathways

“…M1 macrophages can switch to an M2 phenotype and vice versa based on environmental changes, such as secretion of cytokines and growth factors, as well as other conditions 17 . It is generally considered that M1 macrophages play an antitumor role in the early stage of tumour progression 22 . As the tumour progresses, influencing factors, such as abundant immune‐suppressive cytokines and low‐oxygen levels, gradually skew the polarization of TAMs into phenotypically M2 macrophages 23 .…”

“…As the tumour progresses, influencing factors, such as abundant immune‐suppressive cytokines and low‐oxygen levels, gradually skew the polarization of TAMs into phenotypically M2 macrophages 23 . Many studies have shown that macrophages mainly exhibit an M2 phenotype in malignant tumours 22 . The tumour‐associated M2 macrophages then secrete immune‐suppressive cytokines and recruit immune‐suppressive cells, such as regulatory T cells (Tregs), subsequently promoting tumour growth and survival, and they also stimulate angiogenesis and metastasis 23 …”

Real-World Evidence of Traditional Chinese Medicine (TCM) Treatment on Cancer: A Literature-Based Review

“…In addition, traditional Chinese medicine also exhibit a certain alleviation effect on the side effects caused by surgery, chemotherapy, and other treatments and some precancerous lesions [ 43 , 44 ]. A large number of studies have also proved that traditional Chinese medicine including Chinese herbal medicine, acupuncture, and moxibustion as well as other treatments exert their antitumor effects from multiple perspectives and multiple targets [ 44 – 52 ]. The antitumor mechanism of Chinese herbal medicine is shown in Figure 1 .…”

Immunosuppressive tumor microenvironment in extraskeletal myxoid chondrosarcoma: A case of pleural metastases

“…Both TGF‐β1 and VEGF typically promote the polarization of macrophages to an immunosuppressive M2 phenotype. M2 macrophages themselves potentially secrete TGF‐β1 and VEGF and inhibit the recruitment and cytotoxic function of CD8 + T cells 7,8 . VEGF may be involved in hypervascularity in the tumor stroma, which could prevent CD8 + T cells from trafficking into the tumor 9 .…”

“…M2 macrophages themselves potentially secrete TGF‐β1 and VEGF and inhibit the recruitment and cytotoxic function of CD8 + T cells. 7 , 8 VEGF may be involved in hypervascularity in the tumor stroma, which could prevent CD8 + T cells from trafficking into the tumor. 9 Furthermore, HIF‐1α‐positive stromal vessels may participate partially in hypervascularity.…”