Receptor tyrosine kinase target validation and combinatorial strategies to circumvent small molecule therapeutic resistance in canine metastatic insulinoma

Canine insulinoma is a malignant and metastatic tumor of the endocrine pancreas. Clinical evidence suggests that toceranib phosphate (Palladia), a small molecule receptor tyrosine kinase (RTK) inhibitor of c-kit, VEGFR, and PDGFR, might improve outcomes in dogs with insulinoma; yet some affected dogs do not derive benefit. Surprisingly, validating the expression and functionality of toceranib molecular targets has not been confirmed in canine insulinoma, nor have combinatorial strategies explored for overcoming resistance mechanisms. Provocatively, Phase I human trials have identified PAC-1, a small molecule activator of procaspase-3 (PC3), to exert not only single-agent activity in neuroendocrine tumors, but also to circumvent resistance mechanisms employed by cancer in response to RTK inhibitors. Herein, we determine if molecular targets of toceranib and PAC-1 are expressed in canine insulinoma, and if combination treatments can generate synergistic killing and unique gene transcriptional responses, along with how they affect survival and proliferation pathways. A canine insulinoma cell line (canINS), outcome-linked insulinoma tissue microarray, and 20 canine paired primary and metastatic insulinoma tissues were evaluated for PC3, c-kit, VEGFR, and PDGFR expression. Sensitivity and transcriptional responses of canINS to toceranib and PAC-1 were evaluated via viability assays, western blot, and RNAseq. Insulinomas express c-kit and VEGFR, but not PDGFRβ in meaningful amounts. Expression of PC3 was identified in most samples, with expressions being highest in metastatic lesions and correlated with prognosis. In culture, canINS was resistant to Palladia alone, but combination with PAC-1 resulted in sensitization. RNAseq identified putative drug resistance responses and unique cell death induction pathways. Members of the MAPK and AKT pathway were affected by treatments. Canine insulinomas express molecular targets that are druggable with oral therapeutics (toceranib/PAC-1), and when combined, exert synergistic anticancer activities. Given these additive properties, toceranib and PAC-1 would be predicted to improve treatment responses in dogs with metastatic insulinoma.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

VMS-Veterinary Clinical Medcne

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2024

Author dc:creator

• Seelman, Amanda

Contributors dc:contributor

• Fan, Timothy
• Gal, Arnon
• McCoy, Anne

• Insulinoma
• Toceranib Phosphate

Statement dc:rights

• Copyright 2024 Amanda Seelman

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/124207

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F124207