Steatohepatitis Impairs T-cell-Directed Immunotherapies Against Liver Tumors in Mice.

Background & Aims: Nonalcoholic steatohepatitis causes loss of hepatic CD4 T cells and promotes tumor growth. The liver is the most common site of distant metastases from a variety of malignancies, many of which respond to immunotherapy. We investigated the effects of steatohepatitis on the efficacy of immunotherapeutic agents against liver tumors in mice.

Methods: Steatohepatitis was induced by feeding C57BL/6NCrl or BALB/c AnNCr mice a methionine and choline-deficient diet or a choline-deficient l-amino acid-defined diet. Mice were given intrahepatic or subcutaneous injections of B16 melanoma and CT26 colon cancer cells, followed by intravenous injections of M30-RNA vaccine (M30) or intraperitoneal injections of an antibody against OX40 (aOX40) on days 3, 7, and 10 after injection of the tumor cells. We measured tumor growth and analyzed immune cells in tumor tissues by flow cytometry. Mice were given N-acetylcysteine to prevent loss of CD4 T cells from liver.

Results: Administration of M30 and aOX40 inhibited growth of tumors from intrahepatic injections of B16 or CT26 cells in mice on regular diet. However, M30 and/or aOX40 did not slow growth of liver tumors from B16 or CT26 cells in mice with diet-induced steatohepatitis (methionine and choline-deficient diet or choline-deficient l-amino acid-defined diet). Steatohepatitis did not affect the ability of M30 to slow growth of subcutaneous B16 tumors. In mice with steatohepatitis given N-acetylcysteine, which prevents loss of CD4 T cells, M30 and aOX40 were able slow growth of hepatic tumors. Flow cytometry analysis of liver tumors revealed reduced CD4 T cells and effector memory cells in mice with vs without steatohepatitis.

Conclusions: Steatohepatitis reduces the abilities of immunotherapeutic agents, such as M30 and aOX40, to inhibit tumor liver growth by reducing tumor infiltration by CD4 T cells and effector memory cells. N-acetylcysteine restores T-cell numbers in tumors and increases the ability of M30 and aOX40 to slow tumor growth in mice.