ATF4-dependent induction of heme oxygenase 1 prevents anoikis and promotes metastasis
Souvik Dey, … , J. Alan Diehl, Constantinos Koumenis
Souvik Dey, … , J. Alan Diehl, Constantinos Koumenis
Published July 1, 2015; First published May 26, 2015
Citation Information: J Clin Invest. 2015;125(7):2592-2608. https://doi.org/10.1172/JCI78031.
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Research Article Oncology

ATF4-dependent induction of heme oxygenase 1 prevents anoikis and promotes metastasis

Abstract

The integrated stress response (ISR) is a critical mediator of cancer cell survival, and targeting the ISR inhibits tumor progression. Here, we have shown that activating transcription factor 4 (ATF4), a master transcriptional effector of the ISR, protects transformed cells against anoikis — a specialized form of apoptosis — following matrix detachment and also contributes to tumor metastatic properties. Upon loss of attachment, ATF4 activated a coordinated program of cytoprotective autophagy and antioxidant responses, including induced expression of the major antioxidant enzyme heme oxygenase 1 (HO-1). HO-1 upregulation was the result of simultaneous activation of ATF4 and the transcription factor NRF2, which converged on the HO1 promoter. Increased levels of HO-1 ameliorated oxidative stress and cell death. ATF4-deficient human fibrosarcoma cells were unable to colonize the lungs in a murine model, and reconstitution of ATF4 or HO-1 expression in ATF4-deficient cells blocked anoikis and rescued tumor lung colonization. HO-1 expression was higher in human primary and metastatic tumors compared with noncancerous tissue. Moreover, HO-1 expression correlated with reduced overall survival of patients with lung adenocarcinoma and glioblastoma. These results establish HO-1 as a mediator of ATF4-dependent anoikis resistance and tumor metastasis and suggest ATF4 and HO-1 as potential targets for therapeutic intervention in solid tumors.

Authors

Souvik Dey, Carly M. Sayers, Ioannis I. Verginadis, Stacey L. Lehman, Yi Cheng, George J. Cerniglia, Stephen W. Tuttle, Michael D. Feldman, Paul J.L. Zhang, Serge Y. Fuchs, J. Alan Diehl, Constantinos Koumenis

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Figure 4

Absence of ATF4 induces oxidative stress following matrix detachment.

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Absence of ATF4 induces oxidative stress following matrix detachment. (A...
(A) shNT and shATF4.HT1080 cells were treated with 50 μM Trolox (Tlx) in attached or suspension cultures for 48 hours. Immunoblots of indicated proteins as representative of 2 independent experiments are shown. (B) Mean cell survival of 3 independent experiments was measured in Trolox-treated cultures by Trypan blue exclusion and represented as mean ± SD (n = 3). *P < 0.05; **P < 0.01, Student’s t test. (C) DCF-DA fluorescence levels were measured in shNT and shATF4.HT1080 cells at indicated time points. (D) Measurement of nanomoles of 14CO2 (highlighted red in E) released at various time points from shNT and shATF4.HT1080 cells kept in suspension cultures or treated with 5 mM misonidazole (Miso) as positive control. Data for C and D are represented as the mean of 3 independent experiments (n = 3, mean ± SD). *P < 0.05; **P < 0.01, Student’s t test. (E) Schematic representation of the OPPC and measured 14CO2 (red).