GLP overexpression is associated with poor prognosis in Chronic Lymphocytic Leukemia and its inhibition induces leukemic cell death

Summary

Background Heterodimeric methyltransferases GLP (EHMT1/KMT1D) and G9a (EHMT2/KMT1C) are two closely related enzymes that promote the monomethylation and dimethylation of histone H3 lysine 9. Dysregulation of their activity has been implicated in several types of human cancer. Patients and methods Here, in order to investigate whether GLP/G9a exerts any impact on Chronic Lymphocytic Leukemia (CLL), GLP/G9a expression levels were assessed in a cohort of 50 patients and the effects of their inhibition were verified for the viability of CLL cells. Also, qRT-PCR was used to investigate the transcriptional levels of GLP/G9a in CLL patients. In addition, patient samples were classified according to ZAP-70 protein expression by flow cytometry and according to karyotype integrity by cytogenetics analysis. Finally, a selective small molecule inhibitor for GLP/G9a was used to ascertain whether these methyltransferases influenced the viability of MEC-1 CLL cell lineage. Results mRNA analysis revealed that CLL samples had higher levels of GLP, but not G9a, when compared to non-leukemic controls. Interestingly, patients with unfavorable cytogenetics showed higher expression levels of GLP compared to patients with favorable karyotypes. More importantly, GLP/G9a inhibition markedly induced cell death in CLL cells. Conclusion Taken together, these results indicate that GLP is associated with a worse prognosis in CLL, and that the inhibition of GLP/G9a influences CLL cell viability. Altogether, the present data demonstrate that these methyltransferases can be potential markers for disease progression, as well as a promising epigenetic target for CLL treatment and the prevention of disease evolution.

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Fig. 1: Expression analysis of GLP and G9a genes in CLL patients.
Fig. 2: Influence of GLP and G9a gene expressions according to CLL patient’s karyotype.
Fig. 3: Effects of G9a/GLP inhibition in MEC-1 viability.

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Acknowledgments

This study was supported by Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) and Fundação de Amparo à Pesquisa do Distrito Federal (FAPDF).

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Correspondence to Felipe Saldanha-Araujo.

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All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Declaration of Helsinki and its later amendments or comparable ethical standards.

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Alves-Silva, J.C., de Carvalho, J.L., Rabello, D.A. et al. GLP overexpression is associated with poor prognosis in Chronic Lymphocytic Leukemia and its inhibition induces leukemic cell death. Invest New Drugs 36, 955–960 (2018). https://doi.org/10.1007/s10637-018-0613-x

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Keywords

  • Chronic lymphocytic leukemia
  • GLP
  • G9a
  • UNC0646
  • Prognostic marker, cytogenetic abnormalities