mTOR Kinase Inhibition Effectively Decreases Progression of a Subset of Neuroendocrine Tumors that Progress on Rapalog Therapy and Delays Cardiac Impairment

• Published in: Molecular cancer therapeutics Vol. 16; no. 11; pp. 2432 - 2441
• Main Authors: Orr-Asman, Melissa A, Chu, Zhengtao, Jiang, Min, Worley, Mariah, LaSance, Kathleen, Koch, Sheryl E, Carreira, Vinicius S, Dahche, Hanan M, Plas, David R, Komurov, Kakajan, Qi, Xiaoyang, Mercer, Carol A, Anthony, Lowell B, Rubinstein, Jack, Thomas, Hala E
• Format: Journal Article
• Language: English
• Published: United States American Association for Cancer Research Inc 01.11.2017
• Subjects: Animals; Cancer; Carcinoid Heart Disease - complications; Carcinoid Heart Disease - drug therapy; Carcinoid Heart Disease - genetics; Carcinoid Heart Disease - pathology; Cell Line, Tumor; Coronary artery disease; Drug Resistance, Neoplasm - drug effects; Enzyme inhibitors; Everolimus - administration & dosage; Fibrosis; Gene Expression Regulation, Neoplastic - drug effects; Gene sequencing; Heart; Heart diseases; Humans; Inhibition; Lungs; Mice; Neuroendocrine tumors; Neuroendocrine Tumors - complications; Neuroendocrine Tumors - drug therapy; Neuroendocrine Tumors - genetics; Neuroendocrine Tumors - pathology; Pancreas; Pancreatic Neoplasms - complications; Pancreatic Neoplasms - drug therapy; Pancreatic Neoplasms - genetics; Pancreatic Neoplasms - pathology; Patients; Protein Kinase Inhibitors - administration & dosage; Pyrazines - administration & dosage; Rapamycin; Ribonucleic acid; RNA; Signaling; Sirolimus - administration & dosage; Therapy; Thickening; TOR protein; TOR Serine-Threonine Kinases - antagonists & inhibitors; TOR Serine-Threonine Kinases - genetics; Tumors; Xenograft Model Antitumor Assays
• ISSN: 1535-7163; 1538-8514
• DOI: 10.1158/1535-7163.MCT-17-0058

Inhibition of mTOR signaling using the rapalog everolimus is an FDA-approved targeted therapy for patients with lung and gastroenteropancreatic neuroendocrine tumors (NET). However, patients eventually progress on treatment, highlighting the need for additional therapies. We focused on pancreatic NETs (pNET) and reasoned that treatment of these tumors upon progression on rapalog therapy, with an mTOR kinase inhibitor (mTORKi), such as CC-223, could overcome a number of resistance mechanisms in tumors and delay cardiac carcinoid disease. We performed preclinical studies using human pNET cells and injected them subcutaneously or orthotopically to determine tumor progression and cardiac function in mice treated with either rapamycin alone or switched to CC-223 upon progression. Detailed signaling and RNA sequencing analyses were performed on tumors that were sensitive or progressed on mTOR treatment. Approximately 57% of mice bearing pNET tumors that progressed on rapalog therapy showed a significant decrease in tumor volume upon a switch to CC-223. Moreover, mice treated with an mTORKi exhibited decreased cardiac dilation and thickening of heart valves than those treated with placebo or rapamycin alone. In conclusion, in the majority of pNETs that progress on rapalogs, it is possible to reduce disease progression using an mTORKi, such as CC-223. Moreover, CC-223 had an additional transient cardiac benefit on valvular fibrosis compared with placebo- or rapalog-treated mice. These results provide the preclinical rationale to further develop mTORKi clinically upon progression on rapalog therapy and to further test their long-term cardioprotective benefit in those NET patients prone to carcinoid syndrome. .