CD44 and neoplasm: HIF-1α was closely associated with indicators of aggressive phenotype, such as high histological grade, lymph node metastasis, large tumour size, high proliferation rate, negativity of hormone receptors, HER2 positivity and increased VEGF expression; elevated levels of HIF-1α expression were associated independently with shorter disease-free and overall survival [33]; hypoxia and HIF-1α might be related to the worse prognosis found in CD44 + CD24-/low positive breast tumors [35].