01.08.2011 | Research article | Ausgabe 4/2011 Open Access
Tribbles homolog 3 denotes a poor prognosis in breast cancer and is involved in hypoxia response
- Zeitschrift:
- Breast Cancer Research > Ausgabe 4/2011
Wichtige Hinweise
Electronic supplementary material
The online version of this article (doi:10.1186/bcr2934) contains supplementary material, which is available to authorized users.
Competing interests
The authors declare that they have no competing interests.
Authors' contributions
MW performed laboratory experiments, data analysis and participated in the experimental design and drafting of the manuscript. JB participated in the design and coordination of the research and assisted in xenograft assays. BS contributed to the interpretation of the data and critical revised the manuscript. IDN participated in the immunohistochemical stainings and the interpretation of these data. HWML participated in the collection of the patient material and data. JAR and MAV participated in the collection of patient material containing pimonidazole. JJTMH participated in RT-qPCR experiments and interpretation of the results. KMR carried out the MCF-7 knockdown experiments and critically revised the manuscript. FCGJS participated in the design and coordination of the research and assisted in the patient material collection. PNS participated in the design and coordination of the research, performed the statistical analysis and helped to draft the manuscript. All authors read and approved the final manuscript.
Abstract
Introduction
Hypoxia in solid tumors is associated with treatment resistance, resulting in poor prognosis. Tribbles homolog 3 (TRIB3) is induced during hypoxia and is involved in multiple cellular pathways involved in cell survival. Here, we investigated the role of TRIB3 in breast cancer.
Methods
TRIB3 mRNA expression was measured in breast tumor tissue from 247 patients and correlated with clinicopathological parameters and clinical outcome. Furthermore, we studied TRIB3 expression regulation in cell lines, xenografts tissues and human breast cancer material using Reverse transcriptase, quantitative polymerase chain reaction (RT-qPCR) and immunohistochemical staining. Finally, the effect of small interfering RNA (siRNA) mediated TRIB3 knockdown on hypoxia tolerance was assessed.
Results
Breast cancer patients with low, intermediate or high TRIB3 expression exhibited a mean disease free survival (DFS) of 80 (95% confidence interval [CI] = 74 to 86), 74 (CI = 67 to 81), and 63 (CI = 55 to 71) months respectively (P = .002, Mantel-Cox log-rank). The prognostic value of TRIB3 was limited to those patients that had received radiotherapy as part of their primary treatment (n = 179, P = .005) and remained statistically significant after correction for other clinicopathological parameters (DFS, Hazard Ratio = 1.90, CI = 1.17 to 3.08, P = .009). In breast cell lines TRIB3 expression was induced by hypoxia, nutrient starvation, and endoplasmic reticulum stress in an hypoxia inducible factor 1 (HIF-1) independent manner. TRIB3 induction after hypoxia did not increase with decreasing oxygen levels. In breast tumor xenografts and human breast cancer tissues TRIB3 co-localized with the hypoxic cell marker pimonidazole. The induction of TRIB3 by hypoxia was shown to be regulated via the PERK/ATF4/CHOP pathway of the unfolded protein response and knockdown of TRIB3 resulted in a dose-dependent increase in hypoxia sensitivity.
Conclusions
TRIB3 is independently associated with poor prognosis of breast cancer patients, possibly through its association with tumor cell hypoxia.
