Treatment with a cholecystokinin receptor antagonist, proglumide, improves efficacy of immune checkpoint antibodies in hepatocellular carcinoma

Abstract: Hepatocellular cancer (HCC) is the 3rd leading cause of cancer-associated deaths worldwide. Treatment with immune checkpoint antibodies has shown promise in advanced HCC, but the response is only 15-20% with monotherapy and 25-40% with combination therapy. We discovered a potential target for the treatment of HCC; the cholecystokinin-B receptor (CCK-BR). This receptor is over-expressed in murine and human HCC and not in normal liver tissue. Mice bearing syngeneic RIL-175 HCC tumors were treated with PBS (Control), proglumide (a CCK-receptor antagonist), an anti-PD1 antibody, or the combination of proglumide and the anti-PD1 antibody. In vitro, RNA was extracted from untreated or proglumide-treated murine Dt81Hepa1-6 HCC cells and analyzed for expression of fibrosis-associated genes. RNA was also extracted from human HepG2 HCC cells or HepG2 cells treated with proglumide and subjected to RNA sequencing. Results showed that proglumide decreased fibrosis in the tumor microenvironment and increased the number of intratumoral CD8+ T-cells in RIL-175 tumors. When proglumide was given in combination with the anti-PD1 antibody, there was a further significant increase in intratumoral CD8+ T-cells, improved survival, and alterations in genes regulating tumoral fibrosis and epithelial to mesenchymal transition. RNAseq results from human HepG2 HCC cells treated with proglumide showed significant changes in differentially expressed genes involved in tumorigenesis, fibrosis, and the tumor microenvironment. The use of the CCK receptor antagonist proglumide may improve efficacy of immune checkpoint antibodies and survival in those with advanced HCC.