Differential prognostic impact of hypoxia induced and diffuse HIF-1alpha expression in invasive breast cancer

Abstract

Background: Intratumorous hypoxia triggers a broad cellular response mediated by the transcription factor hypoxia inducible factor 1 (HIF-1). HIF-1alpha concentrations increase during breast carcinogenesis, and are associated with poor prognosis. An earlier study noted two HIF-1alpha overexpression patterns: diffuse scattered throughout the tissue and confined to perinecrotic cells.

Aims: To investigate the prognostic impact of these different HIF-1alpha overexpression patterns in relation to its downstream effectors carbonic anhydrase (CA) IX and glucose transporter 1 (GLUT-1).

Methods: HIF-1alpha, CA IX, and GLUT-1 expression was studied by immunohistochemistry, including double staining for CA IX and HIF-1alpha. Clinical data included disease free survival, lymph node status, and tumour size.

Results: HIF-1alpha overexpression (44% of cases) had a perinecrotic (13.5%) or diffuse staining pattern (30.5%). CA IX expression was detectable in 12.5% of breast cancers, whereas GLUT-1 expression was seen in 29%, with both showing perinecrotic membrane staining. Perinecrotic HIF-1alpha overexpression was highly associated with CA IX and GLUT-1 overexpression, and double staining for HIF-1alpha and CA IX showed strong expression in the same cells. Diffusely overexpressed HIF-1alpha was not associated with CA IX or GLUT-1 expression. Patients with diffuse HIF-1alpha staining had a significantly better prognosis than patients with perinecrotically overexpressed HIF-1alpha.

Conclusions: Different regulation pathways of HIF-1alpha overexpression exist in breast cancer: (1) hypoxia induced, perinecrotic HIF-1alpha overexpression with strong expression of hypoxia associated genes (CA IX and GLUT-1), which is associated with a poor prognosis; and (2) diffuse HIF-1alpha overexpression lacking major hypoxia associated downstream effects, resulting in a more favourable prognosis.

Figure 1

Immunohistochemical analysis of hypoxia inducible factor 1α (HIF-1α) and carbonic anhydrase IX (CA IX) in human breast cancer. (A) HIF-1α nuclear expression around necrotic (N) areas. (B) Diffuse nuclear HIF-1α expression, not related to necrosis. (C) CA IX membrane expression around necrotic areas. (D) Glucose transporter 1 (GLUT-1) membrane expression around necrotic areas. (E, F) Double staining revealing strong staining of HIF-1α and CA IX around necrotic areas (original magnification, ×200).

Figure 2

Kaplan–Meier recurrence free survival curves for 166 patients with breast cancer. (A) Recurrence free survival curves for patients with (⩾ 1%) (n  =  66) or without hypoxia inducible factor 1α (HIF-1α) expression (n  =  100); log rank p value, 0.01. (B) Recurrence free survival curves for patients without (< 1%) HIF-1α expression (n  =  100) versus diffuse HIF-1α expression (n  =  51) or necrosis related HIF-1α expression (n  =  15); global log rank p value, 0.02.