Abstract 6329: Carfilzomib: A potential drug against cisplatin-resistant lung adenocarcinoma
Authors: Nam Arin , Mohanty Atish , Bhattacharya Supriyo , Srivastava Saumya , Pangeni Rajendra , Raz Dan , Orban John , Kulkarni Prakash , Salgia Ravi 
Published: September 2020

Recent advances in the treatment of lung cancer, such as small molecule inhibitors and immunotherapy, have transformed care. However, platinum-based chemotherapy, such as cisplatin, is the recommended treatment option for those that do not express markers that respond to targeted therapy. In most cases, prolonged exposure to cisplatin eventually renders cancer cells resistant to therapy and patients progress on this line of care. Our study has shown that integrin beta 4 (ITGB4) and paxillin (PXN) in the focal adhesion complex are highly expressed in lung adenocarcinoma (LUAD) and their interaction plays an important role in mediating cisplatin resistance. Disrupting this axis with an FDA-approved compound can potentially alleviate cisplatin resistance in non-small cell lung cancer. Upon screening 10 LUAD cell lines, we determined one KRAS mutant (H2009) and one KRAS wild-type cell line (H1993) with highest resistance to cisplatin using a cell viability assay. Proximity ligation assay and co-immunoprecipitation results confirmed interaction between ITGB4 and PXN in H2009 cells. By virtually screening a library of 1440 FDA-approved compounds that bind to the N-terminal region of PXN, the top 40 hits were screened using a cell-based assay with H358 cells. These results determined the top 11 compounds with the lowest IC50 values (0.8 nM to 1.54 μM). Drug sensitivity to these 11 compounds was tested again using the cisplatin-resistant cell line H2009. Carfilzomib, a proteasome inhibitor, was identified to be the most effective (IC50 = 193.4 nM). This compound was further tested in 3D cell line-derived spheroids and patient cancer tissue-derived organoids that were allowed to form in multi-well ultra-low attachment plates. These cultures were monitored in real-time using the IncuCyte S3 Live-Cell Analysis System. In cisplatin-resistant cell lines H2009 and H1993, carfilzomib was the most effective (IC50 = 193.4 nM, 1.77 μM, respectively), irrespective of KRAS status. Wound healing was impeded by 20% in H2009 with a submicromolar dose (200 nM). In both H2009 and H1993 cells, a sublethal dose of carfilzomib decreased expression of ITGB4 and phospho-Rb (S807/811) and increased expression of p27, γH2AX, and cleaved PARP, indicating cell cycle inhibition and cell death. In H2009 spheroids, carfilzomib (600 nM) was highly effective in decreasing spheroid viability by 60% and inducing a 2.5-fold increase in caspase-3/7-mediated apoptosis. Also in patient-derived organoids, carfilzomib induced an increase in apoptosis by 5-fold in one case and 50-fold in a second case compared to cisplatin. Another proteasome inhibitor ixazomib was among the top 11 compounds tested in H2009 cells but had a higher IC50 (2.93 μM) compared to carfilzomib, indicating greater efficacy of carfilzomib against cisplatin-resistant LUAD. These results impart a potential therapeutic approach for overcoming chemoresistance in LUAD by targeting the focal adhesion complex through repurposing carfilzomib, an FDA-approved compound.

Citation Format: Arin Nam, Atish Mohanty, Supriyo Bhattacharya, Saumya Srivastava, Rajendra Pangeni, Dan Raz, John Orban, Prakash Kulkarni, Ravi Salgia. Carfilzomib: A potential drug against cisplatin-resistant lung adenocarcinoma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6329.