Whereas the transcription factors thyroid transcription tactor (TTF1), caudal type homeobox 2 (CDX2) and islet-1 (ISL1) were detectable on mRNA levels in NEC-DUE1 cells, NEC-DUE2 expressed only CDX2 transcripts (Figure 4 D). Here, ISL1 is linked to neuroendocrine carcinoma.