Myeloid cells represent a major component of the tumor microenvironment,
where they play divergent dual roles. They can
induce antitumor immune responses, but mostly they promote
immune evasion, tumor progression, and metastasis formation.
Thus, strategies aiming at reprogramming the tumor microenvironment
represent a promising immunotherapy approach. Myeloid
cells respond to environmental factors including signals
derived from commensal microbes. In this Cancer Immunology
at the Crossroads overview, we discuss recent advances on the
effects of the commensal microbiota on myeloid-cell functions
and how they affect the response to cancer therapy.