Leukemias harboring the ETV6-ABL1 fusion represent a rare subset of hematological malignancies with unfavorable outcomes. The constitutively active chimeric Etv6-Abl1 tyrosine kinase can be specifically inhibited by tyrosine kinase inhibitors (TKIs). Although TKIs represent an important therapeutic tool, so far, the mechanism underlying the potential TKI resistance in ETV6-ABL1-positive malignancies has not been studied in detail. To address this issue, we established a TKI-resistant ETV6-ABL1-positive leukemic cell line through long-term exposure to imatinib. ETV6-ABL1-dependent mechanisms (including fusion gene/protein mutation, amplification, enhanced expression or phosphorylation) and increased TKI efflux were excluded as potential causes of resistance. We showed that TKI effectively inhibited the Etv6-Abl1 kinase activity in resistant cells, and using short hairpin RNA (shRNA)-mediated silencing, we confirmed that the resistant cells became independent from the ETV6-ABL1 oncogene. Through analysis of the genomic and proteomic profiles of resistant cells, we identified an acquired mutation in the GNB1 gene, K89M, as the most likely cause of the resistance. We showed that cells harboring mutated GNB1 were capable of restoring signaling through the phosphoinositide-3-kinase (PI3K)/Akt/mTOR and mitogen-activated protein kinase (MAPK) pathways, whose activation is inhibited by TKI. This alternative GNB1K89M-mediated pro-survival signaling rendered ETV6-ABL1-positive leukemic cells resistant to TKI therapy. The mechanism of TKI resistance is independent of the targeted chimeric kinase and thus is potentially relevant not only to ETV6-ABL1-positive leukemias but also to a wider spectrum of malignancies treated by kinase inhibitors.
- MeSH
- chemorezistence účinky léků MeSH
- fúzní onkogenní proteiny genetika MeSH
- imatinib mesylát aplikace a dávkování MeSH
- inhibitory proteinkinas aplikace a dávkování MeSH
- leukemie farmakoterapie genetika patologie MeSH
- lidé MeSH
- malá interferující RNA genetika MeSH
- mutace MeSH
- nádorové buněčné linie MeSH
- proteiny vázající GTP - beta-podjednotky genetika MeSH
- signální transdukce účinky léků MeSH
- tyrosinkinasy genetika MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
PURPOSE: Wilms tumor gene 1 (WT1), a zinc-finger transcription factor essential for testis development and function, along with other genes, was investigated for their role in the pathogenesis of testicular germ cell tumors (TGCT). METHODS: In total, 284 TGCT and 100 control samples were investigated, including qPCR for WT1 expression and BRAF mutation, p53 immunohistochemistry detection, and massively parallel amplicon sequencing. RESULTS: WT1 was significantly (p < 0.0001) under-expressed in TGCT, with an increased ratio of exon 5-lacking isoforms, reaching low levels in chemo-naïve relapsed TGCT patients vs. high levels in chemotherapy-pretreated relapsed patients. BRAF V600E mutation was identified in 1% of patients only. p53 protein was lowly expressed in TGCT metastases compared to the matched primary tumors. Of 9 selected TGCT-linked genes, RAS/BRAF and WT1 mutations were frequent while significant TP53 and KIT variants were not detected (p = 0.0003). CONCLUSIONS: WT1 has been identified as a novel factor involved in TGCT pathogenesis, with a potential prognostic impact. Distinct biologic nature of the two types of relapses occurring in TGCT has been demonstrated. Differential mutation rate of the key TGCT-related genes has been documented.
- MeSH
- down regulace MeSH
- fenotyp MeSH
- genetická predispozice k nemoci MeSH
- geny ras * MeSH
- germinální a embryonální nádory enzymologie genetika patologie MeSH
- imunohistochemie MeSH
- kvantitativní polymerázová řetězová reakce MeSH
- lidé MeSH
- mutace * MeSH
- mutační analýza DNA metody MeSH
- nádorové biomarkery genetika MeSH
- nádorové buněčné linie MeSH
- nádorový supresorový protein p53 genetika MeSH
- prospektivní studie MeSH
- proteiny WT1 genetika MeSH
- protoonkogenní proteiny B-raf genetika MeSH
- protoonkogenní proteiny c-kit genetika MeSH
- retrospektivní studie MeSH
- studie proveditelnosti MeSH
- testikulární nádory enzymologie genetika patologie MeSH
- vysoce účinné nukleotidové sekvenování MeSH
- Check Tag
- lidé MeSH
- mužské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
