In vitro co-culture of PC3 cell with macrophages expressing HO-1 (Hmox1flfl)) or lacking HO-1 (LyzM-Cre-Hmox1flfl) demonstrated that HO-1 expressing macrophages significantly suppressed tumor growth after 24 h compared to PC3 control, however macrophages lacking HO-1 failed to significantly alter growth of PC3 cells (Figure 2E). Here, HMOX1 is linked to neoplasm.