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Background: The prognostic value of PKM2 and its correlation with tumour cell PD-L1 in lung adenocarcinoma (LUAD) is unclear., Methods: A total of 506 lung adenocarcinoma samples from The Cancer Genome Atlas (TCGA) dataset and 173 LUAD tumour tissues from Jiangxi Cancer Hospital were used to analyse the correlation between PKM2 and PD-L1 expression. We further established a stable LUAD cell line with PKM2 knockdown and confirmed the association via Western blotting and flow cytometry analysis. Moreover, the prognostic values of PKM2 and PD-L1 were evaluated by the Kaplan-Meier method and Cox proportional hazards models., Results: Based on the above two large cohorts, we found that PKM2 was significantly positively associated with PD-L1 expression (r = 0.132, P = 0.003 and r = 0.287, P < 0.001, respectively). Subsequently, we found that PKM2 knockdown substantially inhibited PD-L1 expression in the A549 LUAD cell line. Moreover, survival analysis showed that higher expression of PKM2 was correlated with significantly shorter overall survival (OS) and disease-free survival (DFS) in lung adenocarcinoma patients (P < 0.001 and P = 0.050, respectively). Subgroup analysis showed that lung adenocarcinoma patients who expressed high PKM2 and PD-L1 levels experienced the poorest OS and DFS. Additionally, multivariate analysis suggested that high PKM2 and PD-L1 expression was an independent prognostic indicator for worse OS and DFS (HR = 1.462, P < 0.001 and HR = 1.436, P = 0.004, respectively)., Conclusions: Our results demonstrated that PKM2 regulated PD-L1 expression and was associated with poor outcomes in lung adenocarcinoma patients.

Cancer cells express the M2 isoform of glycolytic enzyme pyruvate kinase (PKM2) for favoring the survival under a hypoxic condition. Considering the relative low oxygen microenvironment in stem cell niche, we hypothesized that an enhanced PKM2 expression associates with the biological properties of cancer stem cells. We used A549 human lung cancer cell line and surgical resected lung cancer tissue samples from patients for experiments. We confirmed the co-localization of PKM2 and CD44, a popular marker for cancer stem cells in lung cancer tissue samples from patients. The expression of PKM2 was clearly observed in approximately 80% of the A549 human lung cancer cells. Remarkably, enhanced expression of PKM2 was specially observed in these cells that also positively expressed CD44. Downregulation of PKM2 in CD44+ cancer stem cells by siRNA significantly impaired the potency for spheroid formation, decreased the cell survival under fetal bovine serum deprivation and hypoxic conditions, but increased their sensitivity to anti-cancer drug of cisplatin and γ-ray. The enhanced expression of PKM2 seems to associate with the biological properties of cancer stem cells from A549 human lung cancer cells. Selective targeting of PKM2 may provide a new strategy for cancer therapy, especially for patients with therapeutic resistance.