The paper discusses the role of peritoneal macrophages in uptake and metabolic degradation of high-density proteins of lipoproteins in mice with Ehrlich ascites carcinoma. These processes were found to be influenced by cortisol. Distinctions in spectra of endocellular proteins in tumor-associated macrophages and peritoneal ones in intact mice were identified and, in particular, relative to apolipoprotein E level. Our study demonstrated participation of macrophages in tumor cell-mediated regulation of protein biosynthesis rate under the influence of high-density lipoproteins and cortisol. Apolipoprotein E may play a role of mediator of negative feedback in the mechanism of accelerating protein biosynthesis in tumor cells.