ABCG1 and neoplasm: In the present studies, inhibiting cholesterol efflux pathways globally with SR-B1, or more specifically in myeloid cells by alternative approaches, including targeted deletion of the transporters ABCA1 alone, or ABCA1 in combination with ABCG1, resulted in significant reduction in tumor growth, and accompanying reduction in frequency of the immunosuppressive and tumor-promoting MDSCs.