ARG1 and neoplasm: Moreover, PepO significantly switched TAM to the tumoricidal M1 macrophage as reflected by a reduction in the expression of M2 markers Arg-1, CD206, Fizz-1, Ym1 and IL-10 while increasing the expression of M1 markers iNOS, IL-12a and IL-1β and promoted apoptosis of the tumor cells.