To investigate the effect of HO-1 expression in host cells on growth of primary tumors, C57BL/6 x FvB males and females of different HO-1 genotypes (HO-1+/+, HO-1+/−, HO-1−/−) were injected intracutaneously with B16(F10) melanoma cells (2 × 105 cells/mouse). Here, HMOX1 is linked to melanoma.