The combined inhibition of SLC1A3 and glutaminase in osimertinib-resistant EGFR mutant cells.

BACKGROUND: We investigated the unknown mechanisms of osimertinib-resistant EGFR-mutant lung cancer. METHODS: An osimertinib-resistant cell line (PC-9/OsmR2) was established through continuous exposure to osimertinib using an EGFR exon 19 deletion (19Del) lung adenocarcinoma cell line (PC-9). EGFR 19Del (M1), L858R/T790M/C797S (M6), and L858R/C797S (M8) expression vectors were introduced into Ba/F3 cells. A second osimertinib-resistant line (M1/OsmR) was established through continuous exposure to osimertinib using M1 cells. RESULTS: SLC1A3 had the highest mRNA expression level in PC-9/OsmR2 compared to PC-9 cells by microarray analysis and SLC1A3 was increased by flow cytometry. In PC-9/OsmR2 cells, osimertinib sensitivity was significantly increased in combination with siSLC1A3. Because SLC1A3 functions in glutamic acid transport, osimertinib with a glutaminase inhibitor (CB-839) or an SLC1A3 inhibitor (TFB-TBOA) increased the sensitivity. Also, CB-839 plus TFB-TBOA without osimertinib resulted in greater susceptibility than did CB-839 or TFB-TBOA plus osimertinib. Comprehensive metabolome analysis showed that the M1/OsmR cells had significantly more glutamine and glutamic acid than M1 cells. CB-839 plus osimertinib exerted a synergistic effect on M6 cells and an additive effect on M8 cells. CONCLUSION: Targeting glutaminase and glutamic acid may overcome the osimertinib-resistant EGFR-mutant lung cancer.

Herpes zoster in lung cancer patients treated with PD-1/PD-L1 inhibitors.

Background: Herpes zoster (HZ) occurs mostly in elderly and immunocompromised individuals. Immune reconstitution may be associated with the pathogenesis of HZ. As immune checkpoint inhibitor (ICI) treatment amplifies the immune response, use of ICI may increase the incidence of HZ. There have been few studies of HZ in lung cancer patients treated with ICI. This study was performed to investigate the frequency of HZ in lung cancer patients who received ICI or cytotoxic chemotherapeutic agents. Methods: We searched the electronic medical records for lung cancer patients receiving anticancer drug therapy at our hospital, who developed HZ between April 2011 and June 2020. Results: The review identified 80 patients with a history of ICI treatment (ICI group) and 356 who had been treated with cytotoxic chemotherapeutic agents alone (non-ICI group). Among the 20 patients who developed HZ, 4 (5.0%) belonged to the ICI group and 16 (4.5%) to the non-ICI group (P=0.782). After exclusion of patients aged 65 years and older, to avoid effects of advanced age on the results, the ICI and non-ICI groups consisted of 24 and 81 patients, respectively. In total, 3 of the 24 patients (12.5%) in the ICI group and 1 of the 81 (1.2%) patients in the non-ICI group developed HZ (P=0.0365). Conclusions: There was no significant difference in the rate of HZ between lung cancer patients treated with ICI and those treated with cytotoxic chemotherapy alone. However, patients younger than 65 years treated with ICI might be at increased risk of HZ. Because this is a retrospective small study, further prospective observational studies are needed.