This population accumulates in the blood of cancer bearers (i.e. fibrosarcoma (MN/MCA1) and melanoma (B16/F10)) and preferentially localizes at the invasive tumor margins under the influence of NF-κB1/CSF1-R/C3a signaling axis, which converges on Nrf2 activation to support HO-1 expression. Here, HMOX1 is linked to melanoma.