Melanoma Cell Intrinsic GABAA Receptor Enhancement Potentiates Radiation and Immune Checkpoint Inhibitor Response by Promoting Direct and T Cell-Mediated Antitumor Activity.

Abstract

PURPOSE:

Most patients with metastatic melanoma show variable responses to radiation therapy and do not benefit from immune checkpoint inhibitors. Improved strategies for combination therapy that leverage potential benefits from radiation therapy and immune checkpoint inhibitors are critical.

METHODS AND MATERIALS:

We analyzed metastatic melanoma tumors in the TCGA cohort for expression of genes coding for subunits of type A γ-aminobutyric acid (GABA) receptor (GABAAR), a chloride ion channel and major inhibitory neurotransmitter receptor. Electrophysiology was used to determine whether melanoma cells possess intrinsic GABAAR activity. Melanoma cell viability studies were conducted to test whether enhancing GABAAR mediated chloride transport using benzodiazepine-impaired viability. A syngeneic melanoma mouse model was used to assay the effect of benzodiazepine on tumor volume and its ability to potentiate radiation therapy or immunotherapy. Treated tumors were analyzed for changes in gene expression by RNA sequencing and presence of tumor-infiltrating lymphocytes by flow cytometry.

RESULTS:

Genes coding for subunits of GABAARs express functional GABAARs in melanoma cells. By enhancing GABAAR-mediated anion transport, benzodiazepines depolarize melanoma cells and impair their viability. In vivo, benzodiazepine alone reduces tumor growth and potentiates radiation therapy and α-PD-L1 antitumor activity. The combination of benzodiazepine, radiation therapy, and α-PD-L1 results in near complete regression of treated tumors and a potent abscopal effect, mediated by increased infiltration of polyfunctional CD8+ T cells. Treated tumors show expression of cytokine-cytokine receptor interactions and overrepresentation of p53 signaling.

CONCLUSIONS:

This study identifies an antitumor strategy combining radiation and/or an immune checkpoint inhibitor with modulation of GABAARs in melanoma using benzodiazepine.

• Authors: Daniel A Pomeranz Krummel, Tahseen H Nasti, Milota Kaluzova, Laura Kallay, Debanjan Bhattacharya, Johannes C Melms, Benjamin Izar, Maxwell Xu, Andre Burnham, Taukir Ahmed, Guanguan Li, David Lawson, Jeanne Kowalski, Yichun Cao, Jeffrey M Switchenko, Dan Ionascu, James M Cook, Mario Medvedovic, Andrew Jenkins, Mohammad K Khan, Soma Sengupta
• Journal: International journal of radiation oncology, biology, physics (Int J Radiat Oncol Biol Phys) Vol. 109 Issue 4 Pg. 1040-1053 (03 15 2021) ISSN: 1879-355X [Electronic] United States
• PMID: 33289666 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, Non-P.H.S.)
• Copyright: Copyright © 2020 Elsevier Inc. All rights reserved.

Chemical References

• CKAP4 protein, human
• Immune Checkpoint Inhibitors
• Membrane Proteins
• QH-II-66
• Radiation-Sensitizing Agents
• Receptors, GABA-A
• Benzodiazepines

Topics

• Animals
• Benzodiazepines (pharmacology, therapeutic use)
• Cell Proliferation (drug effects)
• Combined Modality Therapy
• Female
• Humans
• Immune Checkpoint Inhibitors (therapeutic use)
• Melanoma (pathology, therapy)
• Membrane Proteins (analysis)
• Mice
• Mice, Inbred C57BL
• Radiation-Sensitizing Agents (pharmacology)
• Receptors, GABA-A (analysis, physiology)
• T-Lymphocytes (immunology)