Silencing of β-TrCP2 Suppresses Growth and G ₁ /S Cell Cycle Progression in Non-small Cell Lung Carcinoma Cells

Background/Aim: Aberrant cell cycle progression is a hallmark of non-small cell lung cancer (NSCLC) and remains a major driver of uncontrolled tumor growth. β-Transducin repeat-containing protein 2 (β-TrCP2), a substrate-recognition component of an E3 ubiquitin ligase complex, has been implicated in diverse cellular processes; however, its role in NSCLC progression is not fully understood. This study aimed to investigate the functional significance of β-TrCP2 in NSCLC cell proliferation and cell cycle regulation. Materials and Methods: β-TrCP2 was silenced using small interfering RNA (siRNA) in human non-small cell lung cancer (NSCLC) cell lines (A549, H1299, and H460). Cell proliferation was assessed by CCK-8 and colony formation assays. Cell-cycle distribution was analyzed by BrdU/7-AAD flow cytometry. Cell migration was evaluated using wound-healing and Transwell assays. Expression of cell cycle–related genes and proteins was examined by quantitative real-time PCR and western blotting. Subcellular localization of E2F transcription factor 4 (E2F4) was assessed by nuclear fractionation and immunofluorescence. Results: Silencing of β-TrCP2 significantly suppressed proliferation in A549 and H1299 cell lines and reduced migratory capacity in A549 cells. β-TrCP2 depletion induced a pronounced G₁/S cell cycle arrest, accompanied by downregulation of S-phase kinase-associated protein 2 (Skp2), accumulation of the cyclin-dependent kinase (CDK) inhibitors p21 (CDKN1A) and p27 (CDKN1B), and reduced phosphorylation of retinoblastoma protein (Rb). These changes were indicative of attenuated CDK activity. In parallel, β-TrCP2 knockdown led to increased accumulation of E2F4 in both cytoplasmic and nuclear fractions. Conclusion: These findings identify β-TrCP2 as a critical regulator of NSCLC cell lines, A549 and H1299 proliferation by coordinating G₁/S cell cycle progression. Targeting β-TrCP2 may represent a potential therapeutic strategy for NSCLC by disrupting cancer cell cycle control mechanisms.