G9a Inhibition Enhances Checkpoint Inhibitor Blockade Response in Melanoma.

Abstract

PURPOSE:

G9a histone methyltransferase exerts oncogenic effects in several tumor types and its inhibition promotes anticancer effects. However, the impact on checkpoint inhibitor blockade response and the utility of G9a or its target genes as a biomarker is poorly studied. We aimed to examine whether G9a inhibition can augment the efficacy of checkpoint inhibitor blockade and whether LC3B, a G9a target gene, can predict treatment response.

EXPERIMENTAL DESIGN:

Clinical potential of LC3B as a biomarker of checkpoint inhibitor blockade was assessed using patient samples including tumor biopsies and circulating tumor cells from liquid biopsies. Efficacy of G9a inhibition to enhance checkpoint inhibitor blockade was examined using a mouse model.

RESULTS:

Patients with melanoma who responded to checkpoint inhibitor blockade were associated with not only a higher level of tumor LC3B but also a higher proportion of cells expressing LC3B. A higher expression of MAP1LC3B or LC3B protein was associated with longer survival and lower incidence of acquired resistance to checkpoint inhibitor blockade, suggesting LC3B as a potential predictive biomarker. We demonstrate that G9a histone methyltransferase inhibition is able to not only robustly induce LC3B level to augment the efficacy of checkpoint inhibitor blockade, but also induces melanoma cell death.

CONCLUSIONS:

Checkpoint inhibitor blockade response is limited to a subset of the patient population. These results have implications for the development of LC3B as a predictive biomarker of checkpoint inhibitor blockade to guide patient selection, as well as G9a inhibition as a strategy to extend the proportion of patients responding to immunotherapy.

• Authors: Gregory M Kelly, Fares Al-Ejeh, Robert McCuaig, Francesco Casciello, Nabilah Ahmad Kamal, Blake Ferguson, Antonia L Pritchard, Sayed Ali, Ines P Silva, James S Wilmott, Georgina V Long, Richard A Scolyer, Sudha Rao, Nicholas K Hayward, Frank Gannon, Jason S Lee
• Journal: Clinical cancer research : an official journal of the American Association for Cancer Research (Clin Cancer Res) Vol. 27 Issue 9 Pg. 2624-2635 (05 01 2021) ISSN: 1557-3265 [Electronic] United States
• PMID: 33589432 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: ©2021 American Association for Cancer Research.

Chemical References

• Biomarkers, Tumor
• Enzyme Inhibitors
• Histocompatibility Antigens
• Immune Checkpoint Inhibitors
• MAP1LC3B protein, human
• Microtubule-Associated Proteins
• EHMT2 protein, human
• Histone-Lysine N-Methyltransferase

Topics

• Animals
• Biomarkers, Tumor
• Cell Line, Tumor
• Disease Models, Animal
• Drug Synergism
• Enzyme Inhibitors (pharmacology)
• Gene Expression Profiling
• Gene Expression Regulation, Neoplastic
• Histocompatibility Antigens (genetics, metabolism)
• Histone-Lysine N-Methyltransferase (antagonists & inhibitors, genetics, metabolism)
• Humans
• Immune Checkpoint Inhibitors (pharmacology, therapeutic use)
• Melanoma (diagnosis, drug therapy, genetics, metabolism)
• Mice
• Microtubule-Associated Proteins (genetics, metabolism)
• Neoplastic Cells, Circulating
• Prognosis
• Xenograft Model Antitumor Assays