Probing the metabolic regulator and candidate tumor suppressor ALDH1L1 as a target for non-small cell lung cancer gene therapy.

ALDH1L1, a major cytosolic folate enzyme and key regulator of one-carbon metabolism, is strongly and ubiquitously downregulated in lung adenocarcinomas (LUADs) and silenced in LUAD cell lines. Analysis of publicly available databases indicates that ALDH1L1 expression is associated with better prognosis and overall survival in LUAD patients. Here we used lentiviral delivery of ALDH1L1 to target metabolism in ALDH1L1-deficient LUAD cell lines A549 and H460. In these cells, ALDH1L1 expression led to strong inhibition of proliferation, colony formation, and migration. Untargeted metabolomic analysis has shown that ALDH1L1 knockin produces a strong effect on the metabotype of A549 cells including alterations in the tricarboxylic acid cycle intermediates and acylcarnitines, indicative of the impairment of cellular energetics. We have further demonstrated that in mice ALDH1L1, lentiviral delivery dramatically inhibits growth of subcutaneous xenograft tumors derived from A549 cells and prevents lung colonization in a tail-vein model. These effects prolonged for the duration of the experiments (6 weeks) with no noticeable decrease in ALDH1L1 protein levels at the endpoint of the study. We did not observe side effects of ALDH1L1 delivery on animal health when compared with the control group. Our study suggests that ALDH1L1 delivery could be a promising gene therapy approach for treating LUAD.