HA117 endows HL60 cells with a stem-like signature by inhibiting the degradation of DNMT1 via its ability to down-regulate expression of the GGL domain of RGS6

PLoS One. 2017 Jun 30;12(6):e0180142. doi: 10.1371/journal.pone.0180142. eCollection 2017.

Abstract

All-trans retinoic acid (ATRA) induces complete remission in almost all patients with acute promyelocytic leukemia (APL) via its ability to induce the in vivo differentiation of APL blasts. However, prolonged ATRA treatment can result in drug resistance. In previous studies, we generated a multi-drug-resistant HL60/ATRA cell line and found it to contain a new drug resistance-related gene segment, HA117. In this study, we demonstrate that ATRA induces multi-drug-resistant subpopulations of HL60 cells with a putative stem-like signature by up-regulating the expression of the new gene segment HA117. Western blot analysis and quantitative real-time PCR demonstrated that HA117 causes alternative splicing of regulator of G-protein signaling 6 (RGS6) and down-regulation of the expression of the GGL domain of RGS6, which plays an important role in DNA methyltransferase 1 (DNMT1) degradation. Moreover, DNMT1 expression was increased in multi-drug resistance HL60/ATRA cells. Knockdown of HA117 restored expression of the GGL domain and blocked DNMT1 expression. Moreover, resistant cells displayed a putative stem-like signature with increased expression of cancer steam cell markers CD133 and CD123. The stem cell marker, Nanog, was significantly up-regulated. In conclusion, our study shows that HA117 potentially promotes the stem-like signature of the HL60/ATRA cell line by inhibiting by the ubiquitination and degradation of DNMT1 and by down-regulating the expression of the GGL domain of RGS6. These results throw light on the cellular events associated with the ATRA-induced multi-drug resistance phenotype in acute leukemia.

MeSH terms

  • Down-Regulation*
  • Drug Resistance, Neoplasm
  • HL-60 Cells
  • Humans
  • Leukemia, Promyelocytic, Acute / drug therapy
  • Leukemia, Promyelocytic, Acute / pathology
  • Neoplasm Proteins / physiology*
  • Neoplastic Stem Cells / metabolism
  • Neoplastic Stem Cells / pathology*
  • Proteolysis
  • RGS Proteins / chemistry
  • RGS Proteins / metabolism*
  • Repressor Proteins / metabolism*
  • Tretinoin / pharmacology
  • Tretinoin / therapeutic use

Substances

  • DMAP1 protein, human
  • HA117 protein, human
  • Neoplasm Proteins
  • RGS Proteins
  • RGS6 protein, human
  • Repressor Proteins
  • Tretinoin

Grants and funding

JXQ received The National Natural Science Foundation of China (http://www.nsfc.gov.cn/) (NSFC 81370474) for this work. This found had roles in study design, reagent and matieral providing, data collection and analysis, decision to publish, and preparation of the manuscript.