SR‐B1 knockdown improved the immune microenvironment by affecting the level of tumor‐associated macrophage (TAM), mononuclear myeloid‐derived suppressor cells (M‐MDSCs), granulocytic myeloid‐derived suppressor cells (G‐MDSCs), programmed cell death‐ligand 1 (PD‐L1), and human leukocyte antigen class I‐B (HLA‐B), and also reduced the level of low‐density lipoprotein receptor (LDL‐R), and increased the level of ATP binding cassette transporter A1 (ABCA1) to regulate the cholesterol metabolism, and regulated the expression of related genes and intestinal microbiota. Here, ABCA1 is linked to neoplasm.