Neutralization of the autophagy-repressive tissue hormone DBI/ACBP (diazepam binding inhibitor, acyl-CoA binding protein) enhances anticancer immunosurveillance

The plasma concentration of the macroautophagy/autophagy inhibitor DBI/ACBP (diazepam binding inhibitor, acyl-CoA binding protein) increases with aging and body mass index (BMI). Both advanced age and obesity are among the most important risk factors for the development of cancer. We observed that patients with cancer predisposition syndromes due to mutations in <i>BRCA1</i>, <i>BRCA2</i> and <i>TP53</i> exhibit abnormally high plasma DBI/ACBP levels. Additionally, patients without known cancer predisposition syndromes also manifest higher DBI/ACBP levels before imminent cancer diagnosis (within 0-3 years) as compared to age and BMI-matched controls who remain cancer-free. Thus, supranormal plasma DBI/ACBP constitutes a risk factor for later cancer development. Mouse experimentation revealed that genetic or antibody-mediated DBI/ACBP inhibition can delay the development or progression of cancers. In the context of chemoimmunotherapy, DBI/ACBP neutralization enhances tumor infiltration by non-exhausted effector T cells but reduces infiltration by regulatory T cells. This resulted in better cancer control in models of breast cancer, non-small cell lung cancer and sarcoma. We conclude that DBI/ACBP constitutes an actionable autophagy checkpoint for improving cancer immunosurveillance. <b>Abbreviation</b>: BMI, body mass index; CTL, cytotoxic T lymphocyte; DBI, diazepam binding inhibitor, acyl-CoA binding protein; mAb, monoclonal antibody; NSCLC, non-small cell lung cancer; PDCD1/PD-1, programmed cell death 1; scRNA-seq, single-cell RNA sequencing; T_reg, regulatory T cell.