24P - Proviral integration site for Moloney murine leukemia virus-1 (PIM-1) inhibition with AZD1208 to prevent resistance to osimertinib in EGFR mutant NSCLC
- Jillian Bracht (ES)
- Niki Karachaliou (ES)
- Jordi Berenguer (ES)
- Ilaria Attili (IT)
- Masaoki Ito (JP)
- Carles Codony-Servat (ES)
- JORDI Codony-Servat (ES)
- Martyna Filipska (PL)
- Nuno Gil (PT)
- Rafael Rosell (ES)
- Jillian Bracht (ES)
Abstract
Background
Although treatment with EGFR tyrosine kinase inhibitors (TKIs) is initially effective in a subgroup of lung cancer patients, therapy resistance ultimately occurs. Resistance mechanisms consist of overexpression and co-expression of receptor tyrosine kinases (RTKs) and overexpression of STAT3. PIM1 was shown to be an important regulator of both RTKs and STAT3 expression, and inhibition of PIM1 with the pan-PIM inhibitor, AZD1208, might prevent STAT3 and RTK up-regulation after TKI treatment. This research focuses on combining TKI treatment with AZD1208 to prevent therapy resistance in different EGFR mutant NSCLC cell lines.
Methods
Using TaqMan quantitative-PCR we studied basal mRNA expression levels of PIM1 and PIM3 in 5 EGFR-mutant NSCLC cell lines. Cells were then exposed to single osimertinib or AZD1208 treatment, or the combination, to determine the combination index (CI) and changes in cell viability. Moreover, changes in protein expression of different RTKs, STAT3 and downstream effectors of STAT3 were studied in 2 cell lines using western blotting.
Results
The PC9 and H1975 cell lines were shown to have high PIM1 and STAT3 expression compared to the other EGFR mutant NSCLC cell lines. Combined osimertinib and AZD1208 treatment showed moderate synergism in all cell lines, with CIs ranging from 0.75 to 0.86 in triplicate experiments. Western blot experiments indicate that osimertinib treatment leads to upregulation of pCDCP1, pYAP1, pPaxillin and pSTAT3 in the PC9 and H1975 cell lines, suggesting initiation of resistance to single osimertinib treatment. In contrast, single AZD1208 treatment does not induce, or even lower expression of these proteins compared to baseline levels. When combining both treatments, the osimertinib-induced pSTAT3 up-regulation can be prevented with AZD1208. The effect of AZD1208 on RTK expression will be further explored.
Conclusions
Single TKI treatment in EGFR mutant NSCLC induces expression of RTKs and STAT3, ultimately leading to therapy resistance. Inhibition of PIM1 with AZD1208 can abolish the osimertinib-induced phosphorylation of STAT3, and thereby prevents activation of resistance pathways.
Legal entity responsible for the study
IGTP, Germans Trias i Pujol Research Institute, Badalona, Barcelona, Spain
Funding
Fundació Obra Social “La Caixa”
Disclosure
All authors have declared no conflicts of interest.
