# The BRD4 Inhibitor I-BET-762 Reduces HO-1 Expression in Macrophages and the Pancreas of Mice

## TL;DR

This study shows that the drug I-BET-762 reduces HO-1 levels in macrophages and mouse pancreas, potentially preventing inflammation-driven cancer development.

## Contribution

The novel finding is that the bromodomain inhibitor I-BET-762 reduces HO-1 expression in macrophages and pancreas during inflammation.

## Key findings

- HO-1 levels in macrophages correlate with nuclear NRF2 expression in pancreatic cancer models.
- I-BET-762 treatment reduces HO-1 expression in mice with pancreatitis.
- Bromodomain inhibitors may prevent inflammation-driven tumorigenesis by modulating macrophage activity.

## Abstract

In pancreatic cancer, the tumor microenvironment (TME) accounts for up to 90% of the tumor mass. Pancreatitis, characterized by the increased infiltration of macrophages into the pancreas, is a known risk factor for pancreatic cancer. The NRF2 (nuclear factor erythroid 2-related factor 2) transcription factor regulates responses to oxidative stress and can promote cancer and chemoresistance. NRF2 also attenuates inflammation through the regulation of macrophage-specific genes. Heme oxygenase 1 (HO-1) is expressed by anti-inflammatory macrophages to degrade heme, and its expression is dependent on NRF2 translocation to the nucleus. In macrophages stimulated with conditioned media from pancreatic cancer cells, HO-1 protein levels increased, which correlated with higher NRF2 expression in the nuclear fraction. Significant differences in macrophage infiltration and HO-1 expression were detected in LSL-KrasG12D/+; Pdx-1-Cre (KC) mice, Nrf2 whole-body knockout (KO) mice and wildtype mice with pancreatitis. Since epigenetic modulation is a mechanism used by tumors to regulate the TME, using small molecules as epigenetic modulators to activate immune recognition is therapeutically desirable. When the bromodomain inhibitor I-BET-762 was used to treat macrophages or mice with pancreatitis, high levels of HO-1 were reduced. This study shows that bromodomain inhibitors can be used to prevent physiological responses to inflammation that promote tumorigenesis.