Endocrine Abstracts

Neurosurgery is the treatment of choice of non-functioning pituitary tumors (NFPAs), but its success is strongly affected by local invasion. Medical therapy is still under debate, although the use of cabergoline results in tumor shrinkage in a subset of patients. We recently demonstrated that dopamine receptor DRD2 agonist BIM53097 exerts cytostatic and cytotoxic effects in cultured cells from NFPAs, but no data are present in literature about DRD2 mediated effects on pituitary cell migration and invasion.

A key protein involved in cell migration and invasion is the actin binding protein cofilin, whose activity is negatively regulated by phoshorylation at Ser3 by LIM kinases (LIMK), and LIMK is upstream regulated by ROCK.

The aim of this study was to evaluate the effect of BIM53097 on migration and invasion of the non-functioning human pituitary tumor-derived cell line HP75, and to investigate the molecular mechanism involved focusing on the role of cofilin.

To test cell migration, we performed wound healing assays and images taken immediately and 24 h after scratch were analyzed with image analysis software.

Our data demonstrated that 1 μM BIM53097 incubation reduced HP75 cell migration (54% migration vs 65% in control cells, expressed as a % reduction of the free area at 24 h vs 0 h, P<0.05 vs control).

Western blot analysis revealed that BIM53097 treatment induced a 2.4-fold increase cofilin phoshorylation, this effect being reversed by ROCK inhibitor, Y27632.

To evaluate the role of cofilin phosphorylation on cell migration, we used phospho-mimiking or phospho-deficient mutants of cofilin (S3D or S3A, respectively). We observed decrease or increase in S3D or S3A expressing cell migration, respectively (9 and 42% respectively, vs 29% migration of mock transfected cells).

In conclusion, our data showed that DRD2 agonist reduced HP75 cells migration through a molecular mechanism that involves the ROCK-dependent phosphorylation of cofilin.