Endocrine Abstracts

Background: Olfactory neuroblastoma (ONB), a neuroendocrine nasal tumour, exhibits a range of phenotypes from indolent to very aggressive. Even early disease is associated with high (60%) recurrence rates, while advanced disease has 1.5y disease-free and 2.5y overall mean survival. Medical treatments against primary and recurrent disease as well as prognostic biomarkers are urgently required. The few studies available suggest that mTOR/MAPK and Sonic Hedgehog signalling has a role in tumorigenesis in ONB. As cross-talk between pathways leads to drug resistance when single agent inhibitors are used, combined pathway inhibition makes rational sense.

Methods: The human ONB cell line TC268 was treated with IGF-1-inhibitor NVP-AEW541, dual PI3K/mTORC1/2-inhibitor NVP-BEZ235, VEGFR-inhibitor sunitinib, dual AKT/ERK-inhibitor lovastatin, sonic hedgehog-inhibitor itraconazole and novel S6K1-inhibitors FS115/147 alone and in combinations. Western blot and RT-qPCR are used to demonstrate altered pathway components for mTOR/MAPK and Hedgehog signalling respectively.

Results: Most effective inhibition occurred with vertical pathway blockade using AEW541&FS114 (P<0.0001). Similar results were obtained using sunitinib&FS115 (P<0.0001). Combined treatments were more effective than single drugs and at 10x lower doses. Further addition of itraconazole significantly reduced cell viability in combination with S6K1-inhibitors alone and S6K1-inhibitors with AEW541 (P<0.0001). BEZ235 was not as effective at reducing cell viability either alone or in combination, and when this was explored at the protein level we demonstrated unexpected increases in both AKT and ERK phosphorylation post treatment, which may represent a resistance mechanism. Lovastatin did not result in a statistically significant change to viability in any combination.

Establishment of a safe, effective, targeted, combined therapy could be validated on primary culture and a nude mouse xenograft model and then proposed for clinical trials, ultimately aiming at treating both primary and recurrent/inoperable disease.