Abstract

Background and aims: Current systemic therapies for neuroendocrine tumours (NETs) do not provide sufficient control of tumour growth. However, efficient evaluation of novel drugs is hindered by the lack of a suitable preclinical animal model. Here an orthotopic mouse model of pancreatic NET is established and used to study the action of ZK 304709, a first in class, oral multitarget tumour growth inhibitor. ZK 304709 is an inhibitor of cyclin-dependent kinases (Cdks) 1, 2, 4, 7 and 9, vascular endothelial growth factor receptor-type kinases (VEGF-RTKs) 1–3 and platelet-derived growth factor receptor-type kinase β (PDGF-RTKß).

Methods: BON and QGP-1 human NET cells were used to study proliferation, survival and cell cycle distribution in vitro. For induction of orthotopic NETs, BON cells were injected into the pancreas of NMRI^nu/nu mice. Primary tumour growth and metastatic spread were recorded after 9 weeks, and apoptosis, microvessel density and lymphatic vessel density were determined.

Results: ZK 304709 dose-dependently suppressed proliferation and colony formation of NET cells. Direct effects on NET cells were consistent with Cdk inhibition and involved G₂ cell cycle arrest and apoptosis induction, which was associated with reduced expression of MCL1 (myeloid cell leukaemia sequence 1), survivin and hypoxia-inducible factor 1α (HIF1α). Apoptosis similarly occurred in vivo in ZK 304709-treated orthotopic BON tumours, resulting in a 80% reduction of primary tumour growth. In contrast, treatment with lanreotide or 5-fluorouracil and streptozotocin failed to inhibit tumour gowth. ZK 304709 also reduced tumour microvessel density, implicating antiangiogenic mechanisms.

Conclusion: BON orthotopic tumours provide an informative model for preclinical drug evaluation in NETs. In this model, ZK 304709 achieved efficacious tumour growth control via induction of apoptosis and inhibition of tumour-induced angiogenesis.