| Summary: | 碩士 === 國立臺灣大學 === 醫學檢驗暨生物技術學研究所 === 106 === Acute myeloid leukemia (AML) is a hematological malignancy characterized by the aberrant proliferation and differentiation block of precursor myeloid cells. Approximately one third of AML patients harbor FLT3 mutations. Internal tandem duplications mutations in FLT3 (FLT3-ITD) is the most common form and usually correlated with poor prognosis. FLT3 has been considered as a promising therapeutic target for AML, therefore, several FLT3 inhibitors have been used in clinical trials, including cabozantinib (XL184).
Our previous studies demonstrated that cabozantinib selectively inhibited the viability of AML cell lines with FLT3-ITD mutations, including Molm13 cell line (also known as Molm13-P), both in vitro and in vivo. Since drug resistance of FLT3 inhibitors has emerged in clinical, our lab established cabozantinib resistant Molm13 cell line (also known as Molm13-XR) to investigate the mechanisms underlying the drug resistance.
Recent studies indicated that pyrvinium pamoate (PP), an FDA-approved anthelmintic drug, had a potent anticancer activity against various cancer cells. The mechanisms of PP are currently under extensive investigation. However, the anticancer effects and mechanisms of PP toward AML cells still remain unknown.
We revealed that PP caused cytotoxicity toward Molm13-P by inducing cell apoptosis. The IC50 for Molm13-P was 18.43 ± 6.45 nM. Our studies demonstrated that PP slightly inhibited STAT5, WNT/β-catenin and STAT3 signaling pathway in Molm13-P. However, the protein levels of β-catenin and p-STAT3 in nucleus were not decreased, consistent with the unaffected downstream target genes transcription. In addition, PP blocked autophagy without inhibiting autophagy-associated gene transcription. We also found that PP localized on mitochondria and inhibit mitochondrial oxidative phosphorylation, resulting in reduced ATP production in Molm13-P. As a result of impaired mitochondrial function, our studies showed that the mitochondria mass decreased and ROS level increased after PP treatment.
In turn, we also revealed that PP also caused cytotoxicity toward Molm13-XR by inducing cell apoptosis. The IC50 for Molm13-XR was 6.63 ± 4.32 nM. Our studies indicated that PP inhibited STAT5, AKT and ERK activation, and also suppressed WNT/β-catenin and STAT3 signaling pathway in Molm13-XR. However, the protein levels of β-catenin and p-STAT3 in nucleus, as well as the downstream target genes transcription, were not decreased by PP treatment in Molm13-XR,. In addition, PP blocked autophagy without disturbing autophagy-associated gene transcription. PP also localized on mitochondria and inhibited mitochondria oxidative phosphorylation, resulting in decreased ATP production in Molm13-XR. Decreased mitochondria mass and increased ROS level in PP-treated Molm13-XR also implied the mitochondria dysfunction caused by PP. Moreover, we showed that PP and cabozantinib have synergistic effect on Molm13-P and Molm13-XR.
In conclusion, this study supports that PP potently inhibited the viability of Molm13 cell lines with or without cabozantinib resistance through cell apoptosis. Our results demonstrated that PP inhibited mitochondrial function and autophagy both in Molm13-P and Molm13-XR. Although some signaling molecules inactivated by PP, the target gene transcription was not subsequently inhibited. These evidences implied that the effects of PP might primarily change the interaction between signaling pathway and mitochondria, instead of altering the nuclear function.
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