Synergistic Highly Potent Targeted Drug Combinations in Different Pheochromocytoma Models Including Human Tumor Cultures

Abstract

There are no officially approved therapies for metastatic pheochromocytomas apart from ultratrace 131I-metaiodbenzylguanidine therapy, which is approved only in the United States. We have, therefore, investigated the antitumor potential of molecular-targeted approaches in murine pheochromocytoma cell lines [monocyte chemoattractant protein (MPC)/monocyte chemoattractant protein/3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT)], immortalized mouse chromaffin Sdhb−/− cells, three-dimensional pheochromocytoma tumor models (MPC/MTT spheroids), and human pheochromocytoma primary cultures. We identified the specific phosphatidylinositol-3-kinase α inhibitor BYL719 and the mammalian target of rapamycin inhibitor everolimus as the most effective combination in all models. Single treatment with clinically relevant doses of BYL719 and everolimus significantly decreased MPC/MTT and Sdhb−/− cell viability. A targeted combination of both inhibitors synergistically reduced MPC and Sdhb−/− cell viability and showed an additive effect on MTT cells. In MPC/MTT spheroids, treatment with clinically relevant doses of BYL719 alone or in combination with everolimus was highly effective, leading to a significant shrinkage or even a complete collapse of the spheroids. We confirmed the synergism of clinically relevant doses of BYL719 plus everolimus in human pheochromocytoma primary cultures of individual patient tumors with BYL719 attenuating everolimus-induced AKT activation. We have thus established a method to assess molecular-targeted therapies in human pheochromocytoma cultures and identified a highly effective combination therapy. Our data pave the way to customized combination therapy to target individual patient tumors.

Current Management of Pheochromocytoma/Paraganglioma: A Guide for the Practicing Clinician in the Era of Precision Medicine

“…Consistently, we have already shown in several in vitro and in vivo studies that targeted drug combinations show synergistic anti-tumor effects in PCCs/PGLs [159,164,165,166,167]. Moreover, very recently, we established a method to screen multiple targeted drug combinations—some are already in use for other types of cancers—ex vivo in human PCC/PGL primary cultures of individual patient tumors [159]. These data may then be correlated to the signaling pathway alterations and the individual genetic background of the tumor [159].…”

“…Another TKI, the c-Met inhibitor cabozantinib, which was more effective than sunitinib in renal cell carcinoma and in human PCC/PGL primary culture [157,158,159], is currently being investigated in a phase II clinical study in 11 metastatic PCC/PGL patients (initial dose: 60 mg, titrated down on the basis of tolerability) (NCT02302833). Preliminary data have shown tumor size reduction and disease stabilization in most patients, with a median PFS of 11.2 months [160].…”

“…Moreover, very recently, we established a method to screen multiple targeted drug combinations—some are already in use for other types of cancers—ex vivo in human PCC/PGL primary cultures of individual patient tumors [159]. These data may then be correlated to the signaling pathway alterations and the individual genetic background of the tumor [159]. This will hopefully pave the way to customized combination therapy to target individual patient tumors.…”

Anti-Tumor Activity vs. Normal Cell Toxicity: Therapeutic Potential of the Bromotyrosines Aerothionin and Homoaerothionin In Vitro

“…For non-metastatic pheochromocytomas and paragangliomas, surgery is the treatment of choice, but if metastases already occur treatment is challenging [39]. Combination therapy with BYL719, a phosphatidylinositol-3-kinase α inhibitor, and everolimus, a mammalian target of rapamycin inhibitor, showed synergistic effects on PPGLs in vitro [40]. The presence of different secondary metabolites in the sponge also implies that the extent of the chemical defense mechanism might be due to the combination of different metabolites.…”

Advances in paraganglioma–pheochromocytoma cell lines and xenografts

“…Nevertheless, imCCs were recently used together with MPC/MTT and primary pheochromocytoma tumor cultures to assess the efficacy of commonly used drug combinations. Fankhauser et al showed that the PI3Ka inhibitor BYL719 and the mTORC1 inhibitor everolimus were effective in decreasing MPC/MTT and imCC cell viability at clinically relevant doses (Fankhauser et al 2019). Despite the caveats attached to these models as discussed above, and the problem that primary pheochromocytoma cultures have an unknown vitality, complicating interpretation of any results, the comprehensive approach applied in this study was probably the best available at the time.…”