AQP9 and neoplasm: Furthermore, the high level of aqp9 transcription detected in the tumour-derived progenitor cells not evident yet at protein level—we show that it is lowly expressed using immunofluorescent staining and moderately expressed as assessed for cell lysates using Western blot—is a prelude for high expression of both mRNA and protein of this gene in the “differentiated” cells arising from them.