Abstract
Cabozantinib (CBZ) is a small molecule tyrosine kinase receptor inhibitor, which could also inhibit the ABCG2 transporter function. Therefore, CBZ could re-sensitize cancer cells that are resistant to ABCG2 substrate drugs including topotecan (TPT). However, its reversal effect against TPT resistance has not been tested in a TPT-induced resistant cancer model. In this study, a new TPT selected human non-small cell lung cancer (NSCLC)-resistant cell model NCI-H460/TPT10 with ABCG2 overexpression and its parental NCI-H460 cells were utilized to investigate the role of CBZ in drug resistance. The in vitro study showed that CBZ, at a non-toxic concentration, could re-sensitize NCI-H460/TPT10 cells to TPT by restoring intracellular TPT accumulation via inhibiting ABCG2 function. In addition, the increased cytotoxicity by co-administration of CBZ and TPT may be contributed by the synergistic effect on downregulating ABCG2 expression in NCI-H460/TPT10 cells. To further verify the applicability of the NCI-H460/TPT10 cell line to test multidrug resistance (MDR) reversal agents in vivo and to evaluate the in vivo efficacy of CBZ on reversing TPT resistance, a tumor xenograft mouse model was established by implanting NCI-H460 and NCI-H460/TPT10 into nude mice. The NCI-H460/TPT10 xenograft tumors treated with the combination of TPT and CBZ dramatically reduced in size compared to tumors treated with TPT or CBZ alone. The TPT-resistant phenotype of NCI-H460/TPT10 cell line and the reversal capability of CBZ in NCI-H460/TPT10 cells could be extended from in vitro cell model to in vivo xenograft model. Collectively, CBZ is considered to be a potential approach in overcoming ABCG2-mediated MDR in NSCLC. The established NCI-H460/TPT10 xenograft model could be a sound clinically relevant resource for future drug screening to eradicate ABCG2-mediated MDR in NSCLC.
Highlights
MATERIALS AND METHODSLung cancer remains a leading cause of cancer-related death worldwide (Bray et al, 2018; Siegel et al, 2020)
CBZ could restore TPT accumulation in ABCG2 overexpressing NCIH460/TPT10 cells (Figures 1D,E). These observations indicated that the CBZ can alleviate TPT resistance most likely by increasing intracellular TPT level, which could be a result from the ABCG2 inhibitory effect of CBZ
ABCG2 is overexpressed on the plasma membrane of various types of cancer cells functioning as an efflux pump to excrete a broad spectrum of chemotherapeutic drugs (Khunweeraphong et al, 2019)
Summary
Lung cancer remains a leading cause of cancer-related death worldwide (Bray et al, 2018; Siegel et al, 2020). The present study aims to validate the NCI-H460/TPT10 cell line as a clinically relevant model in vivo by establishing an NCIH460/TPT10 tumor xenograft mouse model and to verify the in vivo efficacy of CBZ on reversing TPT resistance using the established animal model. Its TPT-resistant cell line NCI-H460/TPT10 was maintained in the same culture media supplemented with 10 μM TPT (Lei et al, 2020) and switched into a drug-free medium for more than 2 weeks prior to their use. The effect of CBZ on the intracellular accumulation and efflux of [3H]-mitoxantrone was determined in NCI-H460, NCIH460/TPT10, HEK293, and HEK293/ABCG2 cells. Two-way ANOVA followed by Tukey’s post hoc test was performed for comparing multiple groups with repeated tumor volume measurements in the animal study. Statistical significance was set at p < 0.05, and statistical analysis was carried out using GraphPad Prism 8 for macOS (GraphPad Software, La Jolla, CA, United States)
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