Background: Molecularly-targeted therapy has significantly improved the therapeutic efficiency and clinical outcome in a subgroup of NSCLC patients. However, drug resistance inevitably emerges, such as resistance to EGFR TKIs in EGFR-mutated NSCLC. RICTOR is a key component of the mTORC2 complex and plays important roles in cell survival, proliferation, migration and invasion. RICTOR has also been suggested to play a part in the regulation of drug resistance to HER2-targeted therapy in HER2-amplified breast cancer, a niche close to EGFR-targeted therapy. In our current study, we hypothesize that RICTOR modulates the activity of EGFR TKIs in EGFR-mutated NSCLC. Co-targeting RICTOR and EGFR signaling pathways could be a new therapeutic strategy for patients with EGFR-mutated lung cancer.

Results: Genetically modified EGFR-mutated NSCLC cell lines with different RICTOR expression levels have been developed. RICTOR knockdown significantly increases the sensitivity to all three generations of TKI inhibitors (erlotinib, afatinib and osimertinib), whereas overexpression of RICTOR renders the cells more resistant to EGFR TKIs. In addition, RICTOR knockdown restores the sensitivity of erlotinib-resistant HCC827 cells due to AXL overexpression (IC50: 216µM vs. 0.256 µM with RICTOR knockdown, P<0.001). Pharmacological inhibition of the RICTOR signaling pathway with the mTOR1/2 inhibitor (sapanisertib) also improves EGFR TKI sensitivity. Taken together, RICTOR signaling modulates the efficacy of EGFR TKIs in the EGFR-mutated lung cancer models.

Conclusion: Our study provides a new insight into the role of RICTOR signaling modulation in increasing efficacy of EGFR TKI therapy in EGFR-mutated NSCLC. The combination of mTOR1/2 inhibitor and EGFR inhibitor could be a potential novel strategy leading to better therapeutic efficacy.

Note: This abstract was not presented at the meeting.

Citation Format: Ni Fan, Yiyu Zou, Balazs Halmos, Roman Perez-Soler, Haiying Cheng. RICTOR signaling modulates the activity of EGFR tyrosine kinase inhibitors (TKI) in EGFR-mutated non-small cell lung cancer (NSCLC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4748.