Expression of Jun family members in human colorectal adenocarcinoma

The products of the Jun family genes, c-Jun, JunB and JunD, are essential c omponents of the activating protein-1 transcription factor complexes that a re critically important in the control of cell growth, differentiation and neoplastic transformation. Although increased c-Jun expression has been rep orted in human colorectal tumors, expression of JunB and JunD in these tumo rs has not previously been characterized. In the current study, we examined 24 cases of human colorectal adenocarcinoma by western immunoblotting anal ysis and immunohistochemical staining for the expression of c-Jun, JunB and JunD proteins, Normal-appearing colonic mucosa distant from the tumors in the same colectomy specimens were used as a reference for comparison. The r esults showed that both c-Jun and JunB proteins were undetectable or barely detectable in normal mucosa but their expression levels were significantly increased in human colorectal adenocarcinomas, In contrast, JunD protein w as present at high levels in normal mucosa and only showed a minimal increa se in adenocarcinomas. These observations suggest that different Jun protei ns may serve different roles in regulating colonic epithelial cell growth a nd in colorectal tumorigenesis.