The present invention provides erythrocytes or nucleated erythrocyte precursors from animals or patients with at least one S hemoglobin allele which are capable of selectively localizing in tumor vasculature resulting in vaso-occlusion, hemolysis and heme release. A tumoricidal effect is achieved when these cells are administered in before during or after administration of (i) an agent(s) that interferes with degradation of reactive oxygen species, (ii) impairs glucose uptake and/or (iii) chemotherapy. These cells also carry oncolytic viruses, antitumor proteins, multidrug resistant proteins, chemotherapy, monoclonal antibodies, superantigens, superantigen conjugates and fusion proteins, siRNAs, plasmids and non-protein toxins and attenuated tumoricidal bacterial cells specifically into the tumors and induce a tumoricidal effect.
