14P - EED inhibition renders vulnerability to immunotherapy by rewiring ceramide metabolism in pancreatic cancer

Background

Pancreatic cancer has a poor prognosis and is primary resistant to immune checkpoint inhibitors (ICIs) partially due to the inhibitory immune microenvironment. Efforts to augment the sensitivity of pancreatic cancer to ICIs have focused on combinatorial therapies, including epigenetic inhibitors. EED is the regulatory subunit of the histone modification complex PRC2. The aim of this study was to explore the potential effects of EED inhibition combined with PD-1 blockade in pancreatic cancer.

Methods

Allograft models of murine pancreatic cancer lines KPC and Panc02 were used to assess the synergistic effects of PD-1 antibody and APG-5918, a novel EED inhibitor. RNA-sequencing analysis and flow cytometry were performed on the in vivo murine tumors to evaluate the immune cell infiltrations and transcriptomic alterations. The macrophage polarization phenotypes were evaluated by RT-qPCR and flow cytometry in THP1 and Raw264.7 human monocyte lines.

Results

Our study revealed that EED inhibitor APG-5918 synergized with PD-1 antibody in pancreatic cancer in the immune-competent allograft mouse models in vivo. Subsequent flow cytometry and CIBERSORT analysis demonstrated a significant increase of M1 macrophages infiltrated in tumors of the combo group compared with other groups. RNA-sequencing of APG-5918-treated tumor cells showed that EED inhibition significantly upregulated SPMD3 expression, which encoded ceramide-producing enzyme nSMase2, and enriched glycosphingolipid metabolic pathway. Upregulation of ceramide level after treatment of APG-5918 or SPMD3 inhibitor GW4869 in KPC cells was confirmed by ELISA. Furthermore, ceramide production induced by EED knockdown or exogenous administration dramatically promoted macrophage polarization toward M1 phenotype in human monocytes in vitro.

Conclusions

Our results indicate the promising roles of the novel EED inhibitor APG-5918 in reshaping the tumor immune microenvironment, mechanistically through upregulating nSMase2-ceramide pathway, and overcoming the immunotherapy resistance in pancreatic cancer. The new therapeutic strategy of EED inhibitor combining with PD-1 antibody will be tested in further translational and clinical studies.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding

Disclosure

D. Yang: Financial Interests, Personal, Officer: Ascentage Pharma. All other authors have declared no conflicts of interest.