Integration of Downstream Signals of Insulin-like Growth Factor-1 Receptor by Endoplasmic Reticulum Stress for Estrogen-Induced Growth or Apoptosis in Breast Cancer Cells.

Abstract

UNLABELLED:

Estrogen (E2) exerts a dual function on E2-deprived breast cancer cells, with both initial proliferation and subsequent induction of stress responses to cause apoptosis. However, the mechanism by which E2 integrally regulates cell growth or apoptosis-associated pathways remains to be elucidated. Here, E2 deprivation results in many alterations in stress-responsive pathways. For instance, E2-deprived breast cancer cells had higher basal levels of stress-activated protein kinase, c-Jun N-terminal kinase (JNK), compared with wild-type MCF-7 cells. E2 treatment further constitutively activated JNK after 24 hours. However, inhibition of JNK (SP600125) was unable to abolish E2- induced apoptosis, whereas SP600125 alone arrested cells at the G2 phase of the cell cycle and increased apoptosis. Further examination showed that inhibition of JNK increased gene expression of TNFα and did not effectively attenuate expression of apoptosis-related genes induced by E2. A notable finding was that E2 regulated both JNK and Akt as the downstream signals of insulin-like growth factor-1 receptor (IGFIR)/PI3K, but with distinctive modulation patterns: JNK was constitutively activated, whereas Akt and Akt-associated proteins, such as PTEN and mTOR, were selectively degraded. Endoplasmic reticulum-associated degradation (ERAD) was involved in the selective protein degradation. These findings highlight a novel IGFIR/PI3K/JNK axis that plays a proliferative role during the prelude to E2-induced apoptosis and that the endoplasmic reticulum is a key regulatory site to decide cell fate after E2 treatment.

IMPLICATIONS:

This study provides a new rationale for further exploration of E2-induced apoptosis to improve clinical benefit.

• Authors: Ping Fan, Heather E Cunliffe, Philipp Y Maximov, Fadeke A Agboke, Russell E McDaniel, Xiaojun Zou, Pilar Ramos, Megan L Russell, V Craig Jordan
• Journal: Molecular cancer research : MCR (Mol Cancer Res) Vol. 13 Issue 10 Pg. 1367-76 (Oct 2015) ISSN: 1557-3125 [Electronic] United States
• PMID: 26116171 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)
• Copyright: ©2015 American Association for Cancer Research.

Chemical References

• Anthracenes
• Estrogens
• Protein Kinase Inhibitors
• pyrazolanthrone
• Receptor, IGF Type 1
• Proto-Oncogene Proteins c-akt
• MAP Kinase Kinase 4

Topics

• Anthracenes (pharmacology)
• Apoptosis (drug effects, physiology)
• Breast Neoplasms (enzymology, metabolism, pathology)
• Cell Growth Processes (drug effects, physiology)
• Endoplasmic Reticulum Stress (drug effects, physiology)
• Estrogens (deficiency, pharmacology)
• Female
• Humans
• MAP Kinase Kinase 4 (antagonists & inhibitors, metabolism)
• MAP Kinase Signaling System
• MCF-7 Cells
• Protein Kinase Inhibitors (pharmacology)
• Proto-Oncogene Proteins c-akt (metabolism)
• Receptor, IGF Type 1 (metabolism)