Expression of NRG1 and its receptors in human bladder cancer

Background:

Therapies targeting ERBB2 have shown success in the clinic. However, response is not determined solely by expression of ERBB2. Levels of ERBB3, its preferred heterodimerisation partner and ERBB ligands may also have a role.

Methods:

We measured NRG1 expression by real-time quantitative RT–PCR and ERBB receptors by western blotting and immunohistochemistry in bladder tumours and cell lines.

Results:

NRG1α and NRG1β showed significant coordinate expression. NRG1β was upregulated in 78% of cell lines. In tumours, there was a greater range of expression with a trend towards increased NRG1α with higher stage and grade. Increased expression of ERBB proteins was detected in 15% (EGFR), 20% (ERBB2), 41% (ERBB3) and 0% (ERBB4) of cell lines. High EGFR expression was detected in 28% of tumours, associated with grade and stage (P=0.05; P=0.04). Moderate or high expression of ERBB2 was detected in 22% and was associated with stage (P=0.025). Cytoplasmic ERBB3 was associated with high tumour grade (P=0.01) and with ERBB2 positivity. In cell lines, NRG1β expression was significantly inversely related to ERBB3, but this was not confirmed in tumours.

Conclusion:

There is a wide spectrum of NRG1 and ERBB receptor expression in bladder cancer. In advanced tumours, EGFR, ERBB2 and ERBB3 upregulation is common and there is a relationship between expression of ERBB2 and ERBB3 but not the NRG1 ligand.