Figure 4.

The effects of combined osimertinib and pterostilbene¹ treatment in NSCLC cell lines. A: Two EGFR-mutation positive NSCLC cell lines (PC9 and H1975) were treated with single osimertinib (0.02 μM), single pterostilbene¹ (10 μM) or with the combination. Untreated cells received an equivalent dose of vehicle (DMSO). Cell lysates were used for immunoblotting and changes in RTKs and non-RTKs upon the different treatments were investigated in the two cell lines. Experiments were performed in biological triplicates with similar results, and a representative blot is shown. B: Our model: osimertinib blocks the signaling of the EGFR receptor and its downstream pathways. Our previous research has shown that this process causes hyperactivation of compensatory signaling nodes, including STAT3 and Src-YAP1. This leads to an up-regulation of RTKs and non-RTKs (e.g. MET, CDCP1), and ultimately to therapy resistance. The combination of pterostilbene with osimertinib abrogates the osimertinib-induced activation of STAT3, YAP1, CDCP1 and moderately abrogates Src activation. MET expression is also inhibited with the double combination in the H1975 cell line. CDCP1: CUB domain-containing protein-1; DMSO: dimethylsulfoxide; EGFR: epidermal growth factor receptor; NSCLC: non-small cell lung cancer; RTKs: receptor tyrosine kinases; STAT3: signal transducer and activator of transcription 3; YAP1: Src-yes-associated protein 1.