Abstract 4012: EGFR inhibition in combination with PI3K/AKT/mTOR and/or Bcl-2 inhibition is a promising novel therapeutic approach for inverted sinonasal papillomas and associated sinonasal carcinomas
Authors: Apfel Athena M. , Qin Zhaoping , Liu Albert , Soellner Matthew B. , Merajver Sofia D. , Udager Aaron M. , Merrill Nathan M. 
Published: June 2022

Introduction: Activating EGFR mutations are characteristic of inverted sinonasal papillomas (ISP) and ISP-associated sinonasal carcinomas (SNC). Using standard 2D culture models, our group has shown that targeting EGFR activity in ISP-associated SNC effectively inhibits cellular proliferation in vitro. Targeting EGFR in pre-clinical models that are more representative of in vivo patient responses is a critical next step.

Methods: High-throughput drug screening was conducted using a 3D in vitro culture model for two ISP-associated SNC cell lines (SCCNC4 and UM-SCC-112) using a library of &gt;800 curated small molecule inhibitors including inhibitors of EGFR, PI3K/AKT/mTOR (P/A/M), and Bcl-2. Viability was assessed and drug sensitivity scores were calculated. Dual combinations (inhibition of EGFR and P/A/M or Bcl-2) and triple combinations (inhibition of EGFR, P/A/M, and Bcl-2) for select drugs were tested for synergistic killing using the Chou-Talalay and Bliss methods. Treatment-associated transcriptomic changes were monitored using whole-transcriptome RNAseq. Finally, patient-derived organoids (PDOs) from primary sinonasal papilloma or carcinoma tissue were utilized ex vivo for short-term drug screening with EGFR, P/A/M, and/or Bcl-2 inhibitors at maximum human plasma concentration (Cmax) format.

Results: Drug screening demonstrated that ISP-associated SNC cell lines are highly resistant to a diversity of standard and targeted therapeutic agents. Indeed, these cell lines demonstrated poorer responses than other highly resistant tumor types previously analyzed by our group, including triple-negative breast cancer and bladder cancer. Our data demonstrated that EGFR inhibition alone does not effectively kill ISP-associated SNC cells in 3D culture; however, dual and triple combinations of EGFR and P/A/M and/or Bcl-2 inhibitors showed synergistic killing. Finally, sinonasal papilloma and carcinoma PDOs showed partial responses to selected EGFR inhibitors in 3D ex vivo culture.

Conclusions: While EGFR inhibitors effectively inhibit cellular proliferation in ISP-associated SNC cell lines in 2D culture, drug screening in 3D culture and using PDO material - more representative models of in vivo patient responses - show that EGFR inhibition alone is insufficient to completely eliminate these tumor cells, suggesting that EGFR inhibitors alone are unlikely to generate significant clinical responses for patients with ISP or associated SNCs. However, combining targeting of the P/A/M and/or Bcl-2 pathways revealed synergistic killing of ISP-associated SNC cell lines. Taken together, these data demonstrate that compensatory oncogenic and/or anti-apoptotic pathways must be targeted to potentiate EGFR inhibition for successful treatment of ISP and associated SNCs.

Citation Format: Athena M. Apfel, Zhaoping Qin, Albert Liu, Matthew B. Soellner, Sofia D. Merajver, Aaron M. Udager, Nathan M. Merrill. EGFR inhibition in combination with PI3K/AKT/mTOR and/or Bcl-2 inhibition is a promising novel therapeutic approach for inverted sinonasal papillomas and associated sinonasal carcinomas [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 4012.