STK11 (LKB1) mutation suppresses ferroptosis in lung adenocarcinoma by facilitating monounsaturated fatty acid synthesis

Abstract

Serine/threonine kinase 11 (STK11), a tumor suppressor gene, exhibits frequent mutations in lung adenocarcinoma (LUAD). However, the specific molecular mechanisms by which STK11 mutations exert an influence on the biosynthesis of monounsaturated fatty acids (MUFAs) and subsequently affect ferroptosis in LUAD remain indistinct. In this study, bioinformatic analysis was employed to probe into the linkage between STK11 and key inhibitory genes of ferroptosis, namely SLC7A11 and SCD1, in LUAD tissues. Quantitative reverse transcription polymerase chain reaction was employed to assess the expression of STK11 in both wild-type and mutant STK11 LUAD cells, cell counting kit-8 to assess cell viability, and flow cytometry to detect apoptosis. A transmission electron microscope was utilized to observe mitochondrial morphology, and Western blot to ascertain the protein expression of STK11, ferroptosis-related proteins, and the enzyme SCD1 involved in MUFA synthesis. Oil red O staining was employed to test the distribution of lipid droplets in cancer cells, and a lipid quantification method to measure the content of MUFAs. Commercial kits were employed to assess the levels of lipid reactive oxygen species, malondialdehyde, glutathione, and Fe²⁺ in cells. The result revealed a negative correlation between STK11 and SLC7A11 as well as SCD1, with STK11 expression downregulated in mutant STK11 LUAD cells. Furthermore, STK11 mutations were found to suppress ferroptosis in LUAD cells by affecting MUFA synthesis. Subsequent rescue assays demonstrated that STK11 mutations hindered ferroptosis by impacting the synthesis of MUFAs in LUAD cells. This study provided evidence that STK11 mutations suppressed ferroptosis in LUAD cells by promoting MUFA synthesis, thus offering a novel research direction in the management of LUAD.

Keywords: STK11; ferroptosis; lung adenocarcinoma; monounsaturated fatty acid synthesis.

Figure 1

STK11 mutation causes aberrant gene expression and increased expression of ferroptosis inhibition-related proteins. (a) Correlation between STK11 and key ferroptosis inhibition genes; (b) qRT-PCR analysis of STK11 expression in different cell lines; and (c) WB analysis of STK11, SLC7A11, and GPX4 expression levels in cells; * indicates P < 0.05.

Figure 2

STK11 mutation suppresses ferroptosis in LUAD. (a) TEM observation of mitochondrial morphological changes; (b) CCK-8 analysis of cell viability; (c) flow cytometry analysis of cell apoptosis; (d) GSH assay kit analysis of GSH levels in cells; (e) MDA assay kit analysis of lipid peroxidation levels; (f) ROS assay kit analysis of ROS levels in cells; and (g) Fe²⁺ assay kit analysis of Fe²⁺ levels in cells; * indicates P < 0.05.

Figure 2

STK11 mutation suppresses ferroptosis in LUAD. (a) TEM observation of mitochondrial morphological changes; (b) CCK-8 analysis of cell viability; (c) flow cytometry analysis of cell apoptosis; (d) GSH assay kit analysis of GSH levels in cells; (e) MDA assay kit analysis of lipid peroxidation levels; (f) ROS assay kit analysis of ROS levels in cells; and (g) Fe²⁺ assay kit analysis of Fe²⁺ levels in cells; * indicates P < 0.05.

Figure 3

STK11 mutation affects MUFA synthesis to suppress cell ferroptosis. (a) Correlation between STK11 and SCD1; (b) oil red O staining to measure LD content; (c) MUFAs assay kit to quantify MUFA levels; (d) WB analysis of MUFA synthesis-related enzyme protein expression; (e) Flow cytometry analysis of cell apoptosis; (f) GSH assay kit to measure GSH levels in cells; (g) MDA assay kit to measure MDA levels; (h) ROS assay kit to measure ROS levels in cells; and (i) Fe²⁺ assay kit to measure Fe²⁺ levels in cells; * indicates P < 0.05.