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

Matsuo T, Dat le T, Komatsu M, Yoshimaru T, Daizumoto K, Sone S, Nishioka Y, Katagiri T - PLoS ONE (2014)

Bottom Line: Small cell lung cancer (SCLC) is aggressive, with rapid growth and frequent bone metastasis; however, its detailed molecular mechanism remains poorly understood.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.On the other hand, introduction of EGR4 into NIH3T3 cells significantly enhanced cell growth.

View Article: PubMed Central - PubMed

Affiliation: Division of Genome Medicine, Institute for Genome Research, 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.

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PTHrP secretion leads to transactivation of specific PTHrP splice variants.A: Secretion of the PTHrP protein from EGR4-overexpressing HEK293T cells (n = 3, *P<0.05). B: Measurement scheme for the paracrine effects of conditioned media from EGR4-overexpressing cells. C: Real-time PCR analysis of the paracrine effects on the expression of the RANKL, IL-6 and IL-8 genes when medium from EGR4-overexpressing HEK293T cells was cultured with mouse MC3T3-E1 osteoblast cells (n = 2, *, P<0.05, **, P<0.01).
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pone-0113606-g002: PTHrP secretion leads to transactivation of specific PTHrP splice variants.A: Secretion of the PTHrP protein from EGR4-overexpressing HEK293T cells (n = 3, *P<0.05). B: Measurement scheme for the paracrine effects of conditioned media from EGR4-overexpressing cells. C: Real-time PCR analysis of the paracrine effects on the expression of the RANKL, IL-6 and IL-8 genes when medium from EGR4-overexpressing HEK293T cells was cultured with mouse MC3T3-E1 osteoblast cells (n = 2, *, P<0.05, **, P<0.01).

Mentions: It has been reported that PTHrP protein secreted from cancer cells regulates the expression of the RANKL, IL-6 and IL-8 genes, which have been implicated as factors that enhance osteoclast formation and bone destruction in malignant diseases [28]–[30] in osteoblast cells. According to these data and our findings as shown in Figure 1, we hypothesized that PTHrP protein is secreted from EGR4-overexpressing cells. Our results showed that the PTHrP protein concentration was significantly increased in media conditioned from EGR4-overexpressing HEK293T cells (14.43±1.04 pmol/L) compared with conditioned media from mock-transfected cells (11.83±0.15 pmol/L, P<0.05; Figure 2A).


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

Matsuo T, Dat le T, Komatsu M, Yoshimaru T, Daizumoto K, Sone S, Nishioka Y, Katagiri T - PLoS ONE (2014)

PTHrP secretion leads to transactivation of specific PTHrP splice variants.A: Secretion of the PTHrP protein from EGR4-overexpressing HEK293T cells (n = 3, *P<0.05). B: Measurement scheme for the paracrine effects of conditioned media from EGR4-overexpressing cells. C: Real-time PCR analysis of the paracrine effects on the expression of the RANKL, IL-6 and IL-8 genes when medium from EGR4-overexpressing HEK293T cells was cultured with mouse MC3T3-E1 osteoblast cells (n = 2, *, P<0.05, **, P<0.01).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4239076&req=5

pone-0113606-g002: PTHrP secretion leads to transactivation of specific PTHrP splice variants.A: Secretion of the PTHrP protein from EGR4-overexpressing HEK293T cells (n = 3, *P<0.05). B: Measurement scheme for the paracrine effects of conditioned media from EGR4-overexpressing cells. C: Real-time PCR analysis of the paracrine effects on the expression of the RANKL, IL-6 and IL-8 genes when medium from EGR4-overexpressing HEK293T cells was cultured with mouse MC3T3-E1 osteoblast cells (n = 2, *, P<0.05, **, P<0.01).
Mentions: It has been reported that PTHrP protein secreted from cancer cells regulates the expression of the RANKL, IL-6 and IL-8 genes, which have been implicated as factors that enhance osteoclast formation and bone destruction in malignant diseases [28]–[30] in osteoblast cells. According to these data and our findings as shown in Figure 1, we hypothesized that PTHrP protein is secreted from EGR4-overexpressing cells. Our results showed that the PTHrP protein concentration was significantly increased in media conditioned from EGR4-overexpressing HEK293T cells (14.43±1.04 pmol/L) compared with conditioned media from mock-transfected cells (11.83±0.15 pmol/L, P<0.05; Figure 2A).

Bottom Line: Small cell lung cancer (SCLC) is aggressive, with rapid growth and frequent bone metastasis; however, its detailed molecular mechanism remains poorly understood.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.On the other hand, introduction of EGR4 into NIH3T3 cells significantly enhanced cell growth.

View Article: PubMed Central - PubMed

Affiliation: Division of Genome Medicine, Institute for Genome Research, 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.

Show MeSH
Related in: MedlinePlus