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Targeting protein lysine methyltransferase G9A impairs self-renewal of chronic myelogenous leukemia stem cells via upregulation of SOX6

Abstract

The application of tyrosine kinase inhibitors (TKIs) in clinic has revolutionized chronic myelogenous leukemia (CML) treatment, but fails to eliminate leukemia stem cells (LSCs), which are considered as roots of drug resistance and disease relapse. Thus, eradication of LSCs may be a promising strategy for curing CML. In this study, we found that protein lysine methyltransferase G9A was overexpressed in CML LSCs. The upregulation of G9A by BCR-ABL was independent on its tyrosine kinase activity. Knockdown of G9A by shRNAs or pharmacological inhibition of G9A by UNC0642 significantly suppressed survival and impaired self-renewal capacity of CML LSCs. Inhibition of G9a eradicated LSCs in CML mice driven by BCR-ABL gene and dramatically prolonged survival of the mice. Ex vivo treatment with G9A inhibitor inhibited long-term engraftment of CML CD34+ cells in immunodeficient mice. Mechanically, tumor suppressor SOX6 was identified as a direct target of G9A in CML LSCs by RNA-seq analysis. Silencing Sox6 at least partially rescued G9a knockdown-mediated LSCs elimination in vivo. Our findings improve the understanding of LSC regulation network and validate G9A as a therapeutic target in CML LSCs. Targeting G9A may be considered as an additional strategy for the treatment of patients with CML.

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Fig. 1: G9A is highly expressed in human CML stem/progenitor cells and suppression of G9A reduces survival and self-renewal capacity in primary CML CD34+ cells.
Fig. 2: Knockdown of G9a eliminates LSCs and prolongs the survival of CML mice.
Fig. 3: Pharmacological inhibition of G9A induces apoptosis and inhibits self-renewal in human CML CD34+ cells while sparing normal CD34+ cells.
Fig. 4: Pharmacological inhibition of G9A eradicates LSCs and prolongs survival of CML mice.
Fig. 5: Knockdown of G9A impairs LSCs function by upregulating the expression of SOX6.
Fig. 6: Silencing SOX6 restores the in vitro loss of self-renewal capacity and the in vivo elimination of LSCs mediated by G9A knockdown.

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Acknowledgements

This study was supported by grants from the National Natural Science Funds (Nos. 81922069 and 81974505 to YJ; No. 82003778 to CL); the Natural Science Funds of Guangdong Province for Distinguished Young Scholars (Grant No. 2016A030306036 to YJ); the Young Scholar of Science and Technology of Guangdong Province (2016TQ03R926 to YJ).

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MZ, XZ, CL, and YJ designed the research. MZ, XZ, CL, SL, and YJ performed the experiments, analyzed, and interpreted the data. DN and PL provided CML patient samples and information. YJ advised on experiments and provided reagents. MZ and YJ wrote the manuscript. YJ supervised the entire study. All authors reviewed the manuscript.

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Correspondence to Yanli Jin.

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Zhou, M., Zhang, X., Liu, C. et al. Targeting protein lysine methyltransferase G9A impairs self-renewal of chronic myelogenous leukemia stem cells via upregulation of SOX6. Oncogene (2021). https://doi.org/10.1038/s41388-021-01799-1

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