CD44 and neoplasm: Moreover, it has been observed that the changes in the tumour microenvironment of PC cells, including the prevalence of hypoxic zones in primary PCs, and more particularly at the invasive front, may induce HIF-1α and HIF-2α and the reprogramming of PC cells to re-express high levels of some stemness gene products such as CD44, Oct-3/4 and Nanog (Figs 2 and 3) [4].