Activation of signal transducer and activator of transcription 3 (STAT3) signaling in EGFR mutant non-small-cell lung cancer (NSCLC)

Abstract

Gefitinib, erlotinib or afatinib are the current treatment for non-small-cell lung cancer (NSCLC) harboring an activating mutation of the epidermal growth factor receptor (EGFR), but less than 5% of patients achieve a complete response and the median progression-free survival is no longer than 12 months. Early adaptive resistance can occur as soon as two hours after starting treatment by activating signal transducer and activation of transcription 3 (STAT3) signaling. We investigated the activation of STAT3 in a panel of gefitinib-sensitive EGFR mutant cell lines, and gefitinib-resistant PC9 cell lines developed in our laboratory. Afatinib has great activity in gefitinib-sensitive as well as in gefitinib-resistant EGFR mutant NSCLC cell lines. However, afatinib therapy causes phosphorylation of STAT3 tyrosine 705 (pSTAT3Tyr705) and elevation of STAT3 and RANTES mRNA levels. The combination of afatinib with TPCA-1 (a STAT3 inhibitor) ablated pSTAT3Tyr705 and down-regulated STAT3 and RANTES mRNA levels with significant growth inhibitory effect in both gefitinib-sensitive and gefitinib-resistant EGFR mutant NSCLC cell lines. Aldehyde dehydrogenase positive (ALDH+) cells were still observed with the combination at the time that Hairy and Enhancer of Split 1 (HES1) mRNA expression was elevated following therapy. Although the combination of afatinib with STAT3 inhibition cannot eliminate the potential problem of a remnant cancer stem cell population, it represents a substantial advantage and opportunity to further prolong progression free survival and probably could increase the response rate in comparison to the current standard of single therapy.

PIM-1 inhibition with AZD1208 to prevent osimertinib-induced resistance in EGFR-mutation positive non-small cell lung cancer

“…Therefore, defining biomarkers of resistance and designing a truly personalized therapy is of great relevance. We have previously seen, and we confirm in the present work, that EGFR TKIs, including osimertinib, induce STAT3 and Src-YAP1 activation [6][7][8] . Rational double or triple combinations prevented this phenomenon and increased the efficacy of EGFR TKI monotherapy in EGFR-mutation positive models [6][7][8] .…”

“…To our positive surprise, the double combination reversed the osimertinib-induced STAT3 phosphorylation in both cell lines, and diminished paxillin and Src phosphorylation in PC9 and H1975 cells, respectively [ Figure 3B, right panel]. Overall these data reconfirm our previous findings that, even in oncogene addicted EGFR-mutation positive cancer cells, single EGFR TKIs are insufficient [6][7][8]34] . Concomitant PIM-1 inhibition may reverse some of the deleterious effects of osimertinib on the activation of oncogenic signaling pathways.…”

“…The third-generation EGFR TKI, osimertinib is now the standard first-line therapy of these patients [5] . However, although initially effective, monotherapy with EGFR TKIs, including osimertinib, triggers intrinsic or acquired resistance pathways [6][7][8] , and the patients eventually succumb to their disease.…”

“…We have demonstrated that simultaneous inhibition of EGFR, STAT3 and Src-YAP1 was highly synergistic in vitro and in vivo. Moreover, multiple RTKs and non-RTKs were up regulated at baseline or after treatment with EGFR TKIs, limiting their efficacy [6][7][8] . Proviral integration site for Moloney murine leukemia virus-1 (PIM-1) is a serine/threonine kinase, involved in cell cycle progression, cell growth, cell survival and therapy resistance.…”

“…Previous publications have shown that PIM inhibition augments the efficacy of targeted therapies in diverse tumor types. Therefore, dual PIM-1 and EGFR inhibition might modulate cell survival pathways and block progression and growth of cancer cells, by preventing the EGFR TKI-induced STAT3 and RTKs activation in EGFR-mutation positive NSCLC cell lines [6][7][8] . This research aims to evaluate whether the pan-PIM inhibitor AZD1208 improves the efficacy of osimertinib in EGFR-mutation positive cell lines.…”