The main results of the present work, are (i) ATL-1 has systemic effects in vivo, selectively acting on LY6Chi monocytes, precursors of TAMs; (ii) this cell population is decreased in the bone marrow, in the spleen and in the blood of tumor-bearing mice treated with ATL-1; (iii) ATL-1 treatment modified the phenotype of macrophages present in tumors, down modulating the M2-like cells toward a cytotoxic M1-like profile and iv) one single dose of ATL-1 substantially increased survival rate of tumor-bearing mice. This evidence concerns the gene ATL1 and neoplasm.