No amplifications of hypoxiainducible factor1α gene in invasive breast cancer: A tissue microarray study

Objective: Hypoxia Inducible Factor1 HIF1 is an important transcription factor that stimulates tumour growth and metastases via several pathways, including angiogenesis and altered metabolism. Activation of HIF1 depends on the levels of its αsubunit, which increase during hypoxia. Recent studies showed that the HIF1α gene was amplified in prostate cancer, leading to overexpression of HIF1α at normoxia. The aim of this study was to evaluate the presence of HIF1α gene amplifications in invasive breast cancer as an explanation for HIF1α protein overexpression. Methods: Protein and gene expression of HIF1α were analyzed on a tissue microarray of 94 breast cancers by immunohistochemistry and fluorescent in situ hybridization FISH, respectively. Results: Overexpression of HIF1α protein was found in 5894 62 of patients. No amplifications of the HIF1α gene were detected. Conclusion: Increased protein levels of HIF1α are not associated with amplification of the HIF1α gene in human breast cancer. Therefore, other mechanisms than gene amplification must be responsible for HIFα overexpression at normoxia.