PHF5A Contributes to the Maintenance of the Cancer Stem-like Phenotype in Non-Small Cell Lung Cancer by Regulating Histone Deacetylase 8

Objective: Cancer stem-like cells (CSLCs) are closely associated with tumor recurrence, metastasis, and drug-resistance. PHD-finger domain protein 5A (PHF5A) is related to tumorigenesis and development of non-small cell lung cancer (NSCLC). The role and regulatory mechanism of PHF5A in CSLCs of NSCLC remain unclear. This study aimed to identify the biological characteristics of CSLCs and the role of PHF5A in maintaining stemness of NSCLC.

Methods: H1299-spheres and A549-spheres were obtained by oncosphere-forming assay and CSLCs by flow cytometry. Expression of CD133, aldehyde dehydrogenase isoform 1, E-cadherin, vimentin, PHF5A, and histone deacetylase 8 (HDAC8) was tested using immunofluorescence staining, qRT-PCR, and Western blotting. CCK-8 and Transwell assays were employed to determine proliferation, migration, and invasion ability of CSLCs and adherent monolayer cells in NSCLC. We regulated PHF5A expression and HDAC activity in CSLCs to explore the mechanism of PHF5A in stemness maintenance and analyzed expression of target proteins in NSCLC tissues.

Results: Compared with monolayer cells, CSLCs showed a decreased response to cisplatin-mediated inhibition of proliferation, increased migration and invasion, and high expression of PHF5A and HDAC8, accompanied by EMT marker alterations. Targeted knockdown of PHF5A in CSLCs of NSCLC resulted in diminished stemness phenotypes and HDAC8 expression, whereas inhibition of HDAC activity affected stemness maintenance. Moreover, the expression of target proteins showed consistent changes in NSCLC tissues.

Conclusions: Compared with monolayer cells, cancer stem-like phenotype properties of NSCLC were altered, PHF5A was involved in stemness maintenance of CSLCs, and this process may be related to the activation of HDAC8.