About this Research Topic
In normal hematopoiesis, myeloid cells are blood cells that arise from the common myeloid progenitor (CMP) cell, also known as “myeloid stem cell”. Terminally differentiated blood cells originating from this lineage, including macrophages, neutrophils, eosinophils, basophils, mast cells, myeloid dendritic cells and megakaryocytes, as well as various immature or undifferentiated myeloid cells, including monocytes, and myeloid-derived suppressor cells (MDSCs) among others, can be abundant in the tumor stroma of solid cancers. Myeloid cells display different functions in the tumor microenvironment, which may range from tumor-promoting to tumor-suppressive, and their presence may thus significantly influence patient outcome.
In recent years, it has become increasingly evident that solid tumors recruit myeloid cells to support most (if not all) cancer hallmarks, a process occurring in both primary and secondary (i.e. metastatic) sites of tumor development. The metastatic cascade represents a multi-step process, which includes local tumor cell invasion, entry into the vasculature, exit from the circulation and colonization at distal sites. Emerging literature now suggests that myeloid cells can favor or hamper each step of the metastatic cascade, and thus may have a central role in all therapeutic modalities, including chemotherapy, radiotherapy, immunotherapy, and targeted therapy.
The objective of this Research Topic is to review recent data on molecular and cellular mechanisms involved in the dialogue between myeloid cells and cancer cells, leading to cancer cell dissemination and metastasis. We thus welcome Original Research, Reviews and Mini-Reviews on non-hematological, epithelial malignancies, focusing on the following areas:
1) The emerging roles of monocytes/macrophages in extracellular proteolysis, epithelial-to-mesenchymal transition, cancer cell invasion, migration, and dissemination.
2) The role of neutrophils and other myeloid cells in the establishment and maintenance of the pre-metastatic niche and metastatic colonization.
3) The interactions of megakaryocytes with disseminated tumor cells in the metastatic bone marrow microenvironment.
4) The roles of platelets in cancer metastasis.
5) The role of myeloid cells in obfuscating/modifying tumor responses to treatment modalities (chemotherapy, radiotherapy, and targeted therapy).
6) The emerging roles of myeloid cells (with the main focus on macrophages and MDSCs) in the immunomodulation of the tumor microenvironment (immunosuppression and response to immunotherapy).
7) The roles of less-established myeloid cells (i.e. eosinophils, basophils, mast cells, myeloid dendritic cells) in cancer metastasis and therapeutic responses.
Keywords: myeloid cells, tumor microenvironment, metastatic niche, therapeutic response, immunomodulation
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