Long glucocorticoid-induced leucine zipper regulates human thyroid cancer cell proliferation

Long glucocorticoid-induced leucine zipper regulates human thyroid cancer cell proliferation Long glucocorticoid-induced leucine zipper (L-GILZ) has recently been implicated in cancer cell proliferation. Here, we investigated its role in human thyroid cancer cells. L-GILZ protein was highly expressed in well-differentiated cancer cells from thyroid cancer patients and differentiated thyroid cancer cell lines, but poorly expressed in anaplastic tumors. A fusion protein containing L-GILZ, when overexpressed in an L-GILZ-deficient 8505C cell line derived from undifferentiated human thyroid cancer tissue, inhibited cellular proliferation in vitro. In addition, when this protein was injected into nude mice, in which cells from line 8505C had been transplanted, xenograft growth was reduced. Since the mitogen-activated protein kinase (MAPK) pathway is frequently hyperactivated in thyroid cancer cells as a result of the BRAFV600E or Ras mutation, we sought to further investigate the role of L-GILZ in the MAPK pathway. To this end, we analyzed L-GILZ expression and function in cells treated with MAPK inhibitors. We used 8505C cells, which have the BRAFV600E mutation, or the CAL-62 cell line, which harbors a Ras mutation. The cells were treated with the BRAF-specific drug vemurafenib (PLX4032) or the MEK1/2 inhibitor, U0126, respectively. Treatment with these agents inhibited MAPK activation, reduced cell proliferation, and upregulated L-GILZ expression. L-GILZ silencing reversed the antiproliferative activity of the MAPK inhibitors, consistent with an antiproliferative role. Treatment with MAPK inhibitors led to the phosphorylation of the cAMP/response element-binding protein (CREB), and active CREB bound to the L-GILZ promoter, contributing to its transcription. We suggest that the CREB signaling pathway, frequently deregulated in thyroid tumors, is involved in L-GILZ upregulation and that L-GILZ regulates thyroid cancer cell proliferation, which may have potential in cancer treatment. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Cell Death & Disease Springer Journals

Long glucocorticoid-induced leucine zipper regulates human thyroid cancer cell proliferation

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Publisher
Springer Journals
Copyright
Copyright © 2018 by The Author(s)
Subject
Life Sciences; Life Sciences, general; Biochemistry, general; Cell Biology; Immunology; Cell Culture; Antibodies
eISSN
2041-4889
D.O.I.
10.1038/s41419-018-0346-y
Publisher site
See Article on Publisher Site

Abstract

Long glucocorticoid-induced leucine zipper (L-GILZ) has recently been implicated in cancer cell proliferation. Here, we investigated its role in human thyroid cancer cells. L-GILZ protein was highly expressed in well-differentiated cancer cells from thyroid cancer patients and differentiated thyroid cancer cell lines, but poorly expressed in anaplastic tumors. A fusion protein containing L-GILZ, when overexpressed in an L-GILZ-deficient 8505C cell line derived from undifferentiated human thyroid cancer tissue, inhibited cellular proliferation in vitro. In addition, when this protein was injected into nude mice, in which cells from line 8505C had been transplanted, xenograft growth was reduced. Since the mitogen-activated protein kinase (MAPK) pathway is frequently hyperactivated in thyroid cancer cells as a result of the BRAFV600E or Ras mutation, we sought to further investigate the role of L-GILZ in the MAPK pathway. To this end, we analyzed L-GILZ expression and function in cells treated with MAPK inhibitors. We used 8505C cells, which have the BRAFV600E mutation, or the CAL-62 cell line, which harbors a Ras mutation. The cells were treated with the BRAF-specific drug vemurafenib (PLX4032) or the MEK1/2 inhibitor, U0126, respectively. Treatment with these agents inhibited MAPK activation, reduced cell proliferation, and upregulated L-GILZ expression. L-GILZ silencing reversed the antiproliferative activity of the MAPK inhibitors, consistent with an antiproliferative role. Treatment with MAPK inhibitors led to the phosphorylation of the cAMP/response element-binding protein (CREB), and active CREB bound to the L-GILZ promoter, contributing to its transcription. We suggest that the CREB signaling pathway, frequently deregulated in thyroid tumors, is involved in L-GILZ upregulation and that L-GILZ regulates thyroid cancer cell proliferation, which may have potential in cancer treatment.

Journal

Cell Death & DiseaseSpringer Journals

Published: Feb 21, 2018

References

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