Sphingosine kinase 2 may be a promising clinical target for overcoming EGFR-TKI resistance and NSCLC tumor progression.

“Blocking epidermal growth factor receptor (EGFR) with drugs such as erlontinib and osimertinib can prevent non-small lung cancer cells from growing—but only for a while,” explain Neelu Puri, PhD, and colleagues. “Eventually, resistance to these EGFR tyrosine kinase inhibitors (TKIs) occurs. Our team wanted to see if sphingosine kinase 2 (SphK2), a molecule that regulates many cell processes, contributed to this resistance. If so, we wanted to find out if  it was possible to inhibit it so that the drugs will continue to prevent tumor growth.”

The drugs erlotinib and osimertinib, the study authors point out, are commonly used to treat patients with lung cancer with EGFR mutations. However, patients typically develop resistance to these drugs within 10-18 months.

The researchers hypothesized that SphK2 would reverse epithelial-mesenchymal transition (EMT), reduce tumorigenicity, and overcome erlontinib and osimertinib resistance. For a study presented at the 2023 annual meeting of the American Association for Cancer Research, Dr. Puri and colleagues tested their hypothesis by analyzing the expression of SphK2 in both drug-resistant and drug-sensitive (parental) cell lines. “EGFR-TKI resistance may be mediated by EMT, which causes a motile and invasive phenotype similar to mesenchymal cells,” the study authors wrote.

SphK2 Expression Analyzed in Both Drug-Resistant & Drug-Sensitive Cell Lines

To determine if SphK2 was involved in drug resistance, the study team compared parental non-small cell lung cancer (NSCLC) cells with the drug-resistant cells. “We created cell lines that were resistant to erlontinib and osimertinib and used tumor samples from patients with both early-stage and late-stage lung cancer,” Dr. Puri says. “We then conducted a series of tests that included quantitative PCR, immunoblotting, immunofluorescence studies, and immunohistochemistry on both parental and resistant cells to determine the difference in the expression of SphK2 and other related proteins.”

SphK2 Was Higher in Drug-Resistant Cells Vs Parental Cells

Dr. Puri and colleagues observed that levels of SphK2 were higher in the drug-resistant cells compared with the parental cells. “This correlated with our hypothesis that SphK2 was involved in erlotinib and osimertinib resistance,” Dr. Puri notes. “When inhibiting SphK2 in combination with osimertinib, we found an additive effect, which means such inhibitors have the potential to overcome resistance to that chemotherapy drug. In addition, our research showed that SphK2 was higher in late-stage cancer than in early-stage tumors, which indicates it could be a potential biomarker for a patient’s prognosis.”

Since SphK2 decreased cancer cell proliferation, tumor survival, and expression of EMT markers, the study authors wrote, “SphK2 may be a promising clinical target for overcoming EGFR-TKI resistance and NSCLC tumor progression.”

The study team agrees that it would be beneficial to study expression of SphK2 in a larger sample of lung tumors. “We are also working to further understand the mechanism behind SphK2 modulated drug resistance and how it induces tumor metastasis,” Dr. Puri says. “Further studies on in vivo mouse models are also needed to determine the efficacy of SphK2 inhibitors in treating lung cancer tumors.”