Expression of the BRCA1 complex member BRE predicts disease free survival in breast cancer.

Breast cancer is one of the leading causes of cancer mortality in women. Recent advances in gene expression profiling have indicated that breast cancer is a heterogeneous disease and the current prognostication using clinico-pathological features is not sufficient to fully predict therapy response and disease outcome. In this retrospective study, we show that expression levels of BRE, which encodes a member of the BRCA1 DNA damage repair complex, predicted disease-free survival (DFS) in non-familial breast cancer patients. The predictive value of BRE expression depended on whether patients received radiotherapy as a part of their primary treatment. In radiotherapy-treated patients, high BRE expression predicted a favorable DFS (hazard ratio (HR) = 0.47, 95 % confidence interval (CI) = 0.28-0.78, p = 0.004), while in non-treated patients, high BRE expression predicted an adverse prognosis (HR = 2.59, 95 % CI = 1.00-6.75, p = 0.05). Among radiotherapy-treated patients, the prognostic impact of BRE expression was confined to patients with smaller tumors (HR = 0.23, 95 % CI = 0.068-0.75, p = 0.015) and it remained an independent factor after correction for the other prognostic factors age, tumor size, lymph node involvement, and histological grade (HR = 0.50, CI = 0.27-0.90, p = 0.021). In addition, high BRE expression predicted a favorable relapse-free survival in a publicly available dataset of 2,324 breast cancer patients (HR = 0.59, CI = 0.51-0.68, p < 0.001). These data indicate that BRE is an interesting candidate for future functional studies aimed at developing targeted therapies.

Tribbles homolog 3 denotes a poor prognosis in breast cancer and is involved in hypoxia response.

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.

Hypoxia regulation of phosphokinases and the prognostic value of pAKT in breast cancer.

Tumor hypoxia results in poor treatment response and is an indicator of poor outcome in cancer patients. TRIB3 is a hypoxia-upregulated protein involved in the ability of breast cancer cells to survive in hypoxic conditions. It is also involved in the prognosis of cancer patients, possibly by affecting several kinase-signaling pathways. We set out to establish which kinase-signaling pathways are regulated by hypoxia and whether these kinases are relevant for breast cancer prognosis. Using a phosphokinase antibody array comparing cells cultured under hypoxic conditions with those cultured during normoxia, we found that the phosphorylation status of ERK1/2, AKT, p70 S6 kinase, Lck and STAT3 was altered in both MCF7 and MDA-MB-231 breast cancer cells. Using Western blotting, we found that phosphorylated AKT (pAKT) increased in hypoxic conditions. Knockdown of TRIB3 attenuated this effect of hypoxia on AKT activation. Both pAKT and TRIB3 were expressed in pimonidazole-positive, hypoxic areas of human breast cancer tumors. In breast cancer patients significantly lower 5-year disease-free survival was observed for the pAKT-positive compared to the pAKT-negative group (64.6% vs 86.1%, p=0.03). In conclusion, the phosphorylation status of AKT is increased in hypoxic conditions and TRIB3 knockdown attenuates this response. Furthermore, pAKT expression denotes a worse prognosis in breast cancer patients. The hypoxia-related activation of AKT could explain the resistance to various treatments including chemotherapy and radiotherapy.

Regulation of TRIB3 mRNA and protein in breast cancer.

Tribbles homolog 3 (TRIB3) is a scaffold protein activated under hypoxic conditions and involved in several cell survival and proliferation pathways. Recently, we reported opposite associations of TRIB3 mRNA and protein with breast cancer prognosis. In this study, we investigated this discrepancy between TRIB3 mRNA and protein in human breast cancer. We provide several lines of evidence demonstrating that TRIB3 is a stabile protein which levels are not controlled by rapid protein breakdown. Interestingly, we were able to show that during anoxia TRIB3 mRNA translation was profoundly inhibited. Hypoxia induced micro RNA 24 was not responsible for the translational repression of TRIB3. Furthermore miRNA-24 expression levels in breast cancer patient specimens showed no correlation with TRIB3 mRNA or TRIB3 protein levels, or with prognosis. Thus, the expression of miRNA-24 does not explain the difference between mRNA and protein expression of TRIB3 in this cohort of breast cancer patients. In conclusion, TRIB3 protein is a stable protein which levels are predominantly regulated by translational control of TRIB3 mRNA transcript.

TRIB3 protein denotes a good prognosis in breast cancer patients and is associated with hypoxia sensitivity.

BACKGROUND: Tribbles homolog 3 (TRIB3) is a pseudokinase involved in the regulation of several signaling pathways involved in cell survival and/or cell stress. Here, we determined the correlation between breast cancer prognosis and TRIB3 protein levels and established the role of TRIB3 in cell survival after hypoxia and/or radiotherapy. MATERIAL AND METHODS: TRIB3 mRNA and protein were quantified in a new independent breast cancer patient cohort using QPCR and a new specific avian antibody against TRIB3. In addition, we used siRNA-mediated knockdown of TRIB3 in a colony-forming assay after hypoxia and radiotherapy. RESULTS: TRIB3 mRNA and protein levels did not correlate in breast cancer cell lines or human breast cancer material. We validated our earlier finding that high TRIB3 mRNA denotes a poor prognosis, but found that high TRIB3 protein levels were associated with a good prognosis in breast cancer patients. We also show that knockdown of TRIB3 resulted in an increased survival under hypoxic conditions. CONCLUSION: Whereas mRNA levels of TRIB3 are related with a poor prognosis, TRIB3 protein is associated with a good prognosis in human breast cancer patients, possibly due to the fact that TRIB3 is involved in hypoxia tolerance.