Epigenetic inactivation of IRX4 is responsible for acceleration of cell growth in human pancreatic cancer

Kanchan Chakma, Zhaodi Gu, Yakefujiang Abudurexiti, Tatsuo Hata, Fuyuhiko Motoi, Michiaki Unno, Akira Horii, Shinichi Fukushige

Research output: Contribution to journalArticlepeer-review


Epigenetic gene silencing by aberrant DNA methylation is one of the important mechanisms leading to loss of key cellular pathways in tumorigenesis. Methyl-CpG-targeted transcriptional activation (MeTA) reactivates hypermethylation-mediated silenced genes in a different way from DNA-demethylating agents. Microarray coupled with MeTA (MeTA-array) identified seven commonly hypermethylation-mediated silenced genes in 12 pancreatic ductal adenocarcinoma (PDAC) cell lines. Among these, we focused on IRX4 (Iroquois homeobox 4) because IRX4 is located at chromosome 5p15.33 where PDAC susceptibility loci have been identified through genome-wide association study. IRX4 was greatly downregulated in all of the analyzed 12 PDAC cell lines by promoter hypermethylation. In addition, the IRX4 promoter region was found to be frequently and specifically hypermethylated in primary resected PDACs (18/28: 64%). Reexpression of IRX4 inhibited colony formation and proliferation in two PDAC cell lines, PK-1 and PK-9. In contrast, knockdown of IRX4 accelerated cell proliferation in an IRX4-expressing normal pancreatic ductal epithelial cell line, HPDE-1. Because IRX4 is a sequence-specific transcription factor, downstream molecules of IRX4 were pursued by microarray analyses utilizing tetracycline-mediated IRX4 inducible PK-1 and PK-9 cells; CRYAB, CD69, and IL32 were identified as IRX4 downstream candidate genes. Forced expression of these genes suppressed colony formation abilities for both PK-1 and PK-9. These results suggest that DNA methylation-mediated silencing of IRX4 contributes to pancreatic tumorigenesis through aberrant transcriptional regulation of several cancer-related genes.

Original languageEnglish
Pages (from-to)4594-4604
Number of pages11
JournalCancer science
Issue number12
Publication statusPublished - 2020 Dec


  • IRX4
  • MeTA
  • epigenetic gene silencing
  • methyl-CpG binding domain
  • pancreatic ductal adenocarcinoma

ASJC Scopus subject areas

  • Oncology
  • Cancer Research


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