SIRPA and neoplasm: Other mechanisms have been published emphasizing monocyte’s role in tumor-promoting activity through i) abundantly expressing SIRP-α, PD-L1 and other immune-regulatory receptors that suppress the antitumor immune response, ii) priming the premetastatic site, and iii) promoting tumor cell metastasis by producing matrix metalloproteinase and regulating epithelial-mesenchymal transition (23–25).