LAUSR

Osimertinib (OSI) resistance commonly occurs during the treatment of non-small-cell lung cancer (NSCLC). This study aims to investigate whether the thermal effects of radiofrequency ablation (RFA) can increase the sensitivity of OSI-resistant NSCLC to OSI treatment and whether OSI effectively inhibits the recurrence of OSI-resistant NSCLC following RFA treatment and improve survival of NSCLC patients. In vitro, OSI-resistant NCI-H1975 (NCI-H1975/OSIR) cells and thermotolerant NCI-H1975/OSIR (NCI-H1975/OSIR-a-h) cells were established using human NSCLC cell line NCI-H1975. Cell viability, apoptosis, sensitivity to OSI, threonine-methionine amino acid substitution at position 790 (T790M) mutation levels, and protein expression of epidermal growth factor receptor (EGFR), phosphatidylinositol 3-kinase (PI3K), protein kinase B (AKT), hypoxia-inducible factor-1 alpha (HIF-1a) were detected using different methods. In vivo, a nude mouse model of metastatic human lung cancer was constructed and subjected to RFA treatment. The tumor growth, apoptosis, sensitivity to OSI, expression of EGFR/PI3K/AKT/HIF-1a, and CD34 levels were detected in the micrometastases of the transition zone (TZ) around the central ablation zone, and the reference zone (RZ) far from central ablation zone. NCI-H1975/OSIR and thermotolerant NCI-H1975/OSIR cell models were successfully established. Thermotolerant NCI-H1975/OSIR cells show higher sensitivity to OSI than NCI-H1975/OSIR cells and NCI-H1975 cells. OSI treatment can inhibit the EGFR/PI3K/AKT pathway and induce apoptosis in both NCI-H1975 cells and thermotolerant NCI-H1975/OSIR cells, but not in NCI-H1975/OSIR cells. In vivo, RFA treatment increases sensitivity to OSI in NCI-H1975/OSIR cell micrometastases in the TZ but not in the RZ. OSI intervention effectively inhibits the over-proliferation of micrometastases and activation of the EGFR/PI3K/AKT pathway, and induces apoptosis of micrometastases in the TZ, but shows little effects on the micrometastases in the RZ. The thermal effects can increase the sensitivity of OSI-resistant NSCLC cells to OSI through the EGFR/PI3K/AKT/HIF-1a signaling pathway, indicating that RFA combined with OSI might be a clinically effective and comprehensive therapy for the treatment of OSI-resistant NSCLC.