Hypoxia differently regulates the proportion of ALDHhi cells in lung squamous carcinoma H520 and adenocarcinoma A549 cells via the Wnt/β‐catenin pathway

Abstract

Abstract Background Cancer stem cells (CSCs) are a specific subpopulation of cancer cells with the ability of self‐renewal, infinite proliferation, multidifferentiation and tumorigenicity, and play critical roles in cancer progression and treatment resistance. CSCs are tightly regulated by the tumor microenvironment, such as hypoxia; however, how hypoxia regulates CSCs in non‐small cell lung cancer (NSCLC) remains unclear. Methods The proportion of ALDHhi cells was examined using the Aldefluor assay. Tankyrase inhibitor XAV939 and siRNA were used to inhibit β‐catenin while pcDNA3‐β‐catenin (S33Y) plasmid enhanced the expression of β‐catenin. Western blot was administered for protein detection. The mRNA expression was measured by quantitative real‐time PCR. Results We found that hypoxia led to an increase in the proportion of ALDHhi cells in lung squamous carcinoma (LUSC) H520 cells, while causing a decrease in the ALDHhi cell proportion in lung adenocarcinoma (LUAD) A549 cells. Similarly, β‐catenin expression was upregulated in H520 cells but downregulated in A549 cells upon exposure to hypoxia. Mechanically, the proportion of ALDHhi cells in both cell lines was decreased by β‐catenin inhibitor or siRNA knockdown, whereas increased after β‐catenin overexpression. Furthermore, hypoxia treatment suppressed E‐cadherin expression in H520 cells and enhanced N‐cadherin and β‐catenin expression, while this effect was completely opposite in A549 cells. Conclusion The hypoxia‐EMT‐β‐catenin axis functions as an important regulator for the proportion of CSCs in NSCLC and could potentially be explored as therapeutic targets in the future.

Keywords

• ALDHhi cells
• hypoxia
• lung adenocarcinoma
• lung squamous carcinoma
• Wnt/β‐catenin pathway