Figure 2: Distinctive behaviour of aqp9. Normal expression exhibited by rat progenitors and differentiated derivatives can be compared to that of tumour stem cells and derivatives. Whilst aqp4 expression does not markedly increase from tumour progenitor to differentiated cell, its expression increases markedly in rat differentiated cells. The situation for aqp9 is clearly different. Aqp9 is highly increased in both progenitor and differentiated derivatives when compared to normal rat tissue-derived cells.