Abstract
The transcription factor CEBPA is a master regulator of liver homeostasis, myeloid cell differentiation and is downregulated in several oncogenic diseases. MTL-CEBPA is a small activating RNA drug which upregulates gene expression of CEBPA for treatment of hepatocellular carcinoma (HCC). We investigate whether MTL-CEBPA has immune modulatory effects by combining MTL-CEBPA with an anti-PD-1 checkpoint inhibitor (CPI) and/or radiofrequency ablation (RFA) in two preclinical models. First, mice with two flanks of HCC tumors (BNL) were treated with combinations of RFA (right flank), anti-PD-1 or MTL-CEBPA. The reduction of the left flank tumors was most pronounced in the group treated with RFA+anti-PD1+MTL-CEBPA and 7/8 animals responded. This was the only group with a significant increase in CD8+ and CD49b+/CD45+ tumor infiltrating lymphocytes (TIL). Second, a combination of anti-PD-1+MTL-CEBPA was tested in a CT26 colon cancer model and this treatment significantly reduced tumor size, modulated the tumor immune microenvironment and increased TILs. These data suggest a clinical role for combination treatment with CPIs, RFA and MTL-CEBPA through synergistic priming of the immune tumor response, enabling RFA and CPIs to have a pronounced anti-tumor effect including activity in non-treated tumors in the case of RFA.
Highlights
The transcription factor CEBPA (CCAAT/enhancer-binding protein alpha) is a leucine zipper protein which acts as a master regulator of liver homeostasis, including albumin production, and multiple oncogenic processes including cell cycle control, proliferation and angiogenesis
In a hepatocellular carcinoma (HCC) cell line transfected with MTLCEBPA, increased levels of both CEBPA and albumin mRNA in addition to a 3-fold increase in albumin secretion and 50% decrease in cell proliferation was observed [6,7]
We investigated whether the combination of radiofrequency ablation (RFA), MTL-CEBPA and anti-PD-1 antibody could have enhanced efficacy in the treatment of hepatocellular carcinoma model (BNL 1ME A.7R1)
Summary
The transcription factor CEBPA (CCAAT/enhancer-binding protein alpha) is a leucine zipper protein which acts as a master regulator of liver homeostasis, including albumin production, and multiple oncogenic processes including cell cycle control, proliferation and angiogenesis. It is a master regulator of the hematopoietic myeloid cell lineage, in which it primes and activates the myeloid gene expression program by binding to promoters or enhancers of myeloid-related genes [1,2]. In a cirrhotic rat model with multifocal HCC, the i.v. injection of a formulated small activating RNA (saRNA) to CEBPA decreased the tumor burden by 80%, as well as increasing circulating albumin up to 30% [8,9,10].
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