Related Experiment Videos
A decrease in ubiquitination and resulting prolonged life-span of KIT underlies the KIT overexpression-mediated
Masato Kobayashi1, Shiori Kuroki1, Sena Kurita1
1Department of Veterinary Clinical Pathology, Nippon Veterinary and Life Science University, Kyonan-cho, Musashino-shi, Tokyo 180-8602, Japan.
Abstract:
Overexpression of KIT is one of the mechanisms that contributes to imatinib resistance in KIT mutation-driven tumors. Here, the mechanism underlying this overexpression of KIT was investigated using an imatinib-sensitive canine mast cell tumor (MCT) line CoMS, which has an activating mutation in KIT exon 11. A KIT-overexpressing imatinib-resistant subline, rCoMS1, was generated from CoMS cells by their continuous exposure to increasing concentrations of imatinib. Neither a secondary mutation nor upregulated transcription of KIT was detected in rCoMS1 cells. A decrease in KIT ubiquitination, a prolonged KIT life-span, and KIT overexpression were found in rCoMS1 cells. These events were suppressed by withdrawal of imatinib and were re-induced by re‑treatment with imatinib. These findings suggest that imatinib elicited overexpression of KIT via suppression of its ubiquitination. These results also indicated that imatinib-induced overexpression of KIT in rCoMS1 cells was not a permanently acquired feature but was a reversible response of the cells. Moreover, the pan deubiquitinating enzyme inhibitor PR619 prevented imatinib induction of KIT overexpression, suggesting that the imatinib-induced decrease in KIT ubiquitination could be mediated by upregulation and/or activation of deubiquitinating enzyme(s). It may be possible that a similar mechanism of KIT overexpression underlies the acquisition of imatinib resistance in some human tumors that are driven by KIT mutation.
Insights
Imatinib resistance in KIT mutation-driven tumors can arise from KIT overexpression. This study found imatinib suppresses KIT ubiquitination, leading to reversible KIT overexpression and resistance in canine mast cell tumors.
Area of Science:
- Oncology
- Molecular Biology
- Pharmacology
Background:
- Overexpression of KIT is a key mechanism conferring imatinib resistance in KIT mutation-driven cancers.
- Understanding the molecular basis of KIT overexpression is crucial for overcoming therapeutic resistance.
Purpose of the Study:
- To investigate the mechanism by which imatinib induces KIT overexpression in canine mast cell tumors (MCTs).
- To determine if KIT overexpression is a reversible phenomenon and its potential role in imatinib resistance.
Main Methods:
- Generation of an imatinib-resistant canine mast cell tumor cell line (rCoMS1) from an imatinib-sensitive line (CoMS) through continuous imatinib exposure.
- Analysis of KIT expression, transcription, ubiquitination, and lifespan in sensitive and resistant cells.
- Assessment of the effects of imatinib withdrawal, re-treatment, and a deubiquitinating enzyme inhibitor (PR619).
Main Results:
- The imatinib-resistant rCoMS1 cells exhibited KIT overexpression, decreased KIT ubiquitination, and prolonged KIT lifespan, without secondary KIT mutations or transcriptional upregulation.
- Imatinib withdrawal reversed these changes, while re-treatment re-induced them, indicating a reversible mechanism.
- The pan deubiquitinating enzyme inhibitor PR619 blocked imatinib-induced KIT overexpression, suggesting deubiquitinating enzyme involvement.
Conclusions:
- Imatinib induces KIT overexpression by suppressing KIT ubiquitination, a reversible process contributing to imatinib resistance.
- This mechanism, involving deubiquitinating enzymes, may be relevant for imatinib resistance in human KIT-driven tumors.