Abstract 1088: Therapeutic targeting of sphingosine kinase 2 in tyrosine kinase inhibitor resistance and non-small cell lung cancer tumorigenicity
Authors: Dube Namrata Umeshchandra , Lam Katie , Puri Neelu 
Published: June 2022

Abstract
It is anticipated that there will be 235,760 cases and 131,880 deaths due to lung cancer in the US in 2021. Tyrosine Kinase Inhibitors (TKIs) such as Erlotinib (ER) and Osimertinib (OR) are currently being used to treat lung cancer patients with EGFR mutations; however, patients develop resistance to these drugs within 10-18 months. Sphingosine kinase 2 (SK2), which is upregulated in Non-Small Cell Lung Cancer (NSCLC), phosphorylates sphingosine to sphingosine-1-phosphate (S1P), promoting cancer cell proliferation. The sphingolipid rheostat controls the cell fate by maintaining a balance between pro-survival and pro-apoptotic sphingolipids, which is regulated by SK2. However, the role of SK2 in TKI resistance is not established. To determine if SK2 causes TKI resistance, we have studied its role in NSCLC and TKI resistance. We hypothesize that SK2 may be involved in inducing TKI- resistance in NSCLC cells and is positively correlated with tumor progression. We studied SK2 in both drug resistant (OR and ER) and drug sensitive (parental) H358, H2170, H3255 and PC9 NSCLC cell lines. Our study investigated SK2 expression in drug resistant cells versus parental cells using qPCR and Western Blotting. The effects of SK2 inhibitor, Opaganib, on NSCLC cell proliferation was studied through an MTT assay. We have also studied its expression in early- and late-stage tumors using Immunohistochemistry (IHC). In drug resistant cells, qPCR studies showed that SK2 was upregulated in H2170 by 1.30-fold (ER) and 1.5-fold (OR); in H358 by 1.36-fold (ER) and 1.17-fold (OR); in PC9 by 3.3-fold (ER) and 1.8-fold (OR) and in H3255 by 4.3-fold (OR) compared to parental cells. A western blotting experiment demonstrated that SK2 was upregulated significantly by 1.7-fold and 1.5-fold in H358OR and H2170OR cells, respectively, compared to parental cells. These results suggest that SK2 may play a role in TKI resistance, as displayed by SK2 upregulation in TKI-resistant cells. MTT assay data showed 71% inhibition of cell growth by Osimertinib and SK2 inhibitor in H2170OR. The inhibition due to the combination of the drug and inhibitor was more than additive by 9% compared to the drug and inhibitor individually. This indicates SK2s potential to overcome TKI- Resistance. To analyze SK2 expression in cancer progression, IHC experiments were performed on 63 early and 48 late stage lung cancer patient sections. We observed upregulation of SK2 in late- stage lung cancer (p&lt;0.05), indicating its role in cancer progression. In conclusion, SK2 may be a key biomarker in combating TKI-resistance and play a role in cancer progression in NSCLC. Thus, SK2 may be a promising candidate for molecular targeted therapy against NSCLC.
Citation Format: Namrata Umeshchandra Dube, Katie Lam, Neelu Puri. Therapeutic targeting of sphingosine kinase 2 in tyrosine kinase inhibitor resistance and non-small cell lung cancer tumorigenicity [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 1088.