Loss of dystroglycan function in oesophageal cancer

Oesophageal cancer is an increasingly common human malignancy, with its incidence in the West rapidly rising. It is associated with a very poor prognosis, and its exact pathogenesis is uncertain. Dystroglycan and E-cadherin are cell adhesion molecules, the loss of which is often related to tumour differentiation, aggressiveness and invasiveness. The aim was therefore to evaluate their roles in oesophageal carcinogenesis.

mRNA and protein levels of dystroglycan and E-cadherin were examined in oesophageal normal and tumour tissue samples, and in FLO-1 oesophageal adenocarcinoma cells, using immunohistochemistry, western blotting and reverse transcription polymerase chain reaction. E-cadherin,α-dystroglycan and β-dystroglycan levels were decreased in the oesophageal primary tumour samples, despite the presence of normal levels of dystroglycan mRNA. In FLO-1 cells, increasing cell density caused a decrease in protein levels of β-dystroglycan over time, despite the persistent presence of dystroglycan mRNA. Re-expression of dystroglycan in FLO-1 cells reduced the numbers and size of colonies formed in soft agar, indicative of a role for dystroglycan in suppressing the tumour phenotype.

The adenocarcinoma cells mirrored the in vivo situation with respect to dystroglycan function, making this a useful model of oesophageal carcinogenesis; moreover, loss of dystroglycan protein, despite the presence of dystroglycan mRNA, points to a post-translational mechanism of dystroglycan loss.