Cytoplasmic location of factor-inhibiting hypoxia-inducible factor is associated with an enhanced hypoxic response and a shorter survival in invasive breast cancer

Ern Yu Tan,Kevin C Gatter,Francesco Pezzella,Stephen B Fox,Helen Turley,Cheng Han,Adrian L Harris,Leticia Campo

doi:10.1186/bcr1838

Abstract

IntroductionHypoxia-inducible factor (HIF)-1α levels in invasive breast carcinoma have been shown to be an adverse prognostic indicator. Cellular HIF-1α activity is regulated by factor-inhibiting hypoxia-inducible factor 1 (FIH-1). In hypoxia, FIH-1 hydroxylation of Asn803 within the C-terminal transactivation domain does not occur and HIF-1α forms a fully active transcriptional complex. The present study investigates the role of FIH-1 in invasive breast carcinoma and its correlation with hypoxia.MethodsMicroarrayed tissue cores from 295 invasive carcinomas were stained for FIH-1, for HIF-1α and for carbonic anhydrase 9. FIH-1 expression was correlated with standard clinicopathological parameters and with the expression of the surrogate hypoxic markers HIF-1α and carbonic anhydrase 9.ResultsFIH-1 was positive in 239/295 (81%) tumours, 42/295 (14%) exclusively in the nucleus and 54/295 (18%) exclusively in the cytoplasm. Exclusive nuclear FIH-1 expression was significantly inversely associated with tumour grade (P = 0.02) and risk of recurrence (P = 0.04), whereas exclusive cytoplasmic FIH-1 was significantly positively associated with tumour grade (P = 0.004) and carbonic anhydrase 9 expression (P = 0.02). Patients with tumours that excluded FIH-1 from the nucleus had a significantly shorter survival compared with those with exclusive nuclear expression (P = 0.02). Cytoplasmic FIH-1 expression was also an independent poor prognostic factor for disease-free survival.ConclusionFIH-1 is widely expressed in invasive breast carcinoma. As with other HIF regulators, its association between cellular compartmentalization and the hypoxic response and survival suggests that tumour regulation of FIH-1 is an additional important mechanism for HIF pathway activation.

Highlights

Hypoxia-inducible factor (HIF)-1α levels in invasive breast carcinoma have been shown to be an adverse prognostic indicator
To better understand the regulation of hypoxiainducible factor 1α (HIF-1α) in breast carcinoma, we have examined the expression of FIH-1 in a large characterized series of breast carcinomas and have correlated this with standard clinicopathological parameters and various markers of hypoxia
Factor-inhibiting hypoxia-inducible factor-1 expression in invasive breast carcinoma FIH-1 was widely expressed among the invasive breast carcinomas analysed (Figure 1)

Summary

Introduction

Hypoxia-inducible factor (HIF)-1α levels in invasive breast carcinoma have been shown to be an adverse prognostic indicator. The neoplastic cells can adapt to this hostile microenvironment using the activation of hypoxia-induced genes for angiogenesis, glycolysis and other processes advantageous to cell proliferation and survival. The activation of these hypoxia-induced genes centres on the levels of hypoxia-inducible factor (HIF) 1 within the tumour cell [3]. Tumour cells in perinecrotic regions of ductal carcinoma in situ lesions, where HIF-1α levels are high, exhibit a CA9 = carbonic anhydrase 9; CI = confidence interval; ER = oestrogen receptor; FIH-1 = factor-inhibiting hypoxia-inducible factor 1; H & E = haematoxylin and eosin; HER2 = human epidermal growth factor receptor 2; HIF = hypoxia-inducible factor; HR = hazard ratio; OR = odds ratio; PBS = phosphate-buffered saline; PHD = prolyl hydroxylase domain; TAD = transcriptional activation domain

Methods

Results

Discussion

Conclusion