Early growth response 4 is involved in cell proliferation of small cell lung cancer through transcriptional activation of its downstream genes

Taisuke Matsuo; Le Tan Dat; Masato Komatsu; Tetsuro Yoshimaru; Kei Daizumoto; Saburo Sone; Yasuhiko Nishioka; Toyomasa Katagiri

doi:10.1371/journal.pone.0113606

Early growth response 4 is involved in cell proliferation of small cell lung cancer through transcriptional activation of its downstream genes

PLoS One. 2014 Nov 20;9(11):e113606. doi: 10.1371/journal.pone.0113606. eCollection 2014.

Authors

Taisuke Matsuo¹, Le Tan Dat², Masato Komatsu¹, Tetsuro Yoshimaru¹, Kei Daizumoto¹, Saburo Sone³, Yasuhiko Nishioka³, Toyomasa Katagiri¹

Affiliations

¹ Division of Genome Medicine, Institute for Genome Research, The University of Tokushima, Tokushima, Japan.
² Division of Genome Medicine, Institute for Genome Research, The University of Tokushima, Tokushima, Japan; Department of Medical Oncology, Institute of Health Biosciences, The University of Tokushima, Tokushima, Japan.
³ Department of Medical Oncology, Institute of Health Biosciences, The University of Tokushima, Tokushima, Japan.

Abstract

Small cell lung cancer (SCLC) is aggressive, with rapid growth and frequent bone metastasis; however, its detailed molecular mechanism remains poorly understood. Here, we report the critical role of early growth factor 4 (EGR4), a DNA-binding, zinc-finger transcription factor, in cell proliferation of SCLC. EGR4 overexpression in HEK293T cells conferred significant upregulation of specific splice variants of the parathyroid hormone-related protein (PTHrP) gene, resulting in enhancement of the secretion of PTHrP protein, a known mediator of osteolytic bone metastasis. More importantly, depletion of EGR4 expression by siRNA significantly suppressed growth of the SCLC cell lines, SBC-5, SBC-3 and NCI-H1048. On the other hand, introduction of EGR4 into NIH3T3 cells significantly enhanced cell growth. We identified four EGR4 target genes, SAMD5, RAB15, SYNPO and DLX5, which were the most significantly downregulated genes upon depletion of EGR4 expression in all of the SCLC cells examined, and demonstrated the direct recruitment of EGR4 to their promoters by ChIP and luciferase reporter analysis. Notably, knockdown of the expression of these genes by siRNA remarkably suppressed the growth of all the SCLC cells. Taken together, our findings suggest that EGR4 likely regulates the bone metastasis and proliferation of SCLC cells via transcriptional regulation of several target genes, and may therefore be a promising target for the development of anticancer drugs for SCLC patients.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Animals
Cell Line, Tumor
Cell Proliferation
Chromatin Immunoprecipitation
Early Growth Response Transcription Factors / antagonists & inhibitors
Early Growth Response Transcription Factors / genetics
Early Growth Response Transcription Factors / metabolism*
HEK293 Cells
Homeodomain Proteins / antagonists & inhibitors
Homeodomain Proteins / genetics
Homeodomain Proteins / metabolism
Humans
Interleukin-6 / genetics
Interleukin-6 / metabolism
Interleukin-8 / genetics
Interleukin-8 / metabolism
Lung Neoplasms / metabolism
Lung Neoplasms / pathology
Mice
Microfilament Proteins / antagonists & inhibitors
Microfilament Proteins / genetics
Microfilament Proteins / metabolism
NIH 3T3 Cells
Paracrine Communication
Parathyroid Hormone-Related Protein / genetics
Parathyroid Hormone-Related Protein / metabolism*
RANK Ligand / genetics
RANK Ligand / metabolism
Small Cell Lung Carcinoma / metabolism
Small Cell Lung Carcinoma / pathology
Transcription Factors / antagonists & inhibitors
Transcription Factors / genetics
Transcription Factors / metabolism
Transcriptional Activation
Up-Regulation
rab GTP-Binding Proteins / antagonists & inhibitors
rab GTP-Binding Proteins / genetics
rab GTP-Binding Proteins / metabolism

Substances

DLX5 protein, human
EGR4 protein, human
Early Growth Response Transcription Factors
Homeodomain Proteins
Interleukin-6
Interleukin-8
Microfilament Proteins
Parathyroid Hormone-Related Protein
RANK Ligand
SYNPO protein, human
TNFSF11 protein, human
Transcription Factors
Rab15 protein, human
rab GTP-Binding Proteins

Grants and funding

This study was supported by future advanced research from the University of Tokushima. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.