Investigating the role of PLK4 and GDF15 in NSCLC tumorigenicity and EGFR-TKI resistance

Background : Non-small cell lung cancer (NSCLC) accounts for nearly 85% of all lung cancers, and the development of resistance to Epidermal Growth Factor Receptor (EGFR) Tyrosine Kinase Inhibitors (TKIs) remains a major clinical challenge, limiting long-term therapeutic success. Emerging evidence shows that PI3K/Akt and TGF-beta-signaling are key drivers of EGFR-TKI resistance. Polo-like kinase 4 (PLK4), a serine/threonine kinase, regulates centriole duplication and maintains genomic stability, while its overexpression can promote oncogenic transformation and tumor progression through PI3K/Akt activation. Notably, PLK4-driven signaling intersects with stress-responsive pathways, creating a cellular environment conducive to survival and therapeutic resistance. Within this context, Growth differentiation factor 15 (GDF15), a stress-responsive cytokine and member of the TGF-beta superfamily, is significantly upregulated in NSCLC, particularly in patients with a history of smoking. GDF15 promotes metastasis, epithelial-mesenchymal transition (EMT), and therapy resistance through TGF-beta and ErbB crosstalk. Moreover, GDF15 is also emerging as a novel biomarker and potential therapeutic target in NSCLC, playing a key role in EGFR-TKI resistance and enhancing tumorigenicity. Hypothesis/Aims : We hypothesize that overexpression of PLK4 and GDF15 drives tumorigenesis and EGFR-TKI resistance through PI3K-Akt-mTOR, TGF-beta and ErbB signaling in NSCLC, and that modulating these key biomarkers may help reduce tumorigenicity and overcome resistance. Study Design : We examined PLK4 and GDF15 expressions in drug-resistant - Osimertinib-resistant (OR) and Erlotinib-resistant (ER) and drug-sensitive (parental) NSCLC cell lines after 24- and 48-hour CSE treatment using qPCR, western blotting, and immunofluorescence. Results : Immunoblot analyses revealed that PLK4 protein expression levels were upregulated by ~2.0- to 4.0-fold in both OR and ER NSCLC cell lines compared with parental controls (p < 0.05) also supported by strong immunofluorescence signals. Quantitative PCR further showed significant GDF15 upregulation from 1.4- to 3.4-fold in both Osimertinib and Erlotinib resistant cells particularly after 48 h of cigarette-smoke-extract exposure, suggesting that smoking-related stress may further enhance its expression. These findings indicate that both PLK4 and GDF15 contribute to enhanced proliferative capacity, survival signaling, and the maintenance of resistant phenotypes. Conclusion : Collectively, our data suggests that overexpression of PLK4 and GDF15 activates PI3K/Akt/mTOR, TGF-beta, and ErbB pathways, promoting EGFR-TKI resistance and NSCLC progression. Targeting these key biomarkers may help overcome resistance and limit tumor growth, particularly in smoking-associated NSCLC cases.