CYP11A1 and neoplasm: The best evidence for the cellular source of glucocorticoids in tumors was provided by showing that mice with targeted deletion of Cyp11a1, which generates pregnenolone, a precursor of all steroids (Figure 1A), in myeloid cells (Cyp11a1LysM–Cre mice) had reduced tumor growth and increased CD8+ tumor-infiltrating lymphocytes (TILs) inflammatory cytokine production.