Integrating Murine and Clinical Trials with Cabozantinib to Understand Roles of MET and VEGFR2 as Targets for Growth Inhibition of Prostate Cancer.
OBJECTIVE
We performed parallel investigations in cabozantinib-treated patients in a phase II trial and simultaneously in patient-derived xenograft (PDX) models to better understand the roles of MET and VEGFR2 as targets for prostate cancer therapy.


METHODS
In the clinical trial, radiographic imaging and serum markers were examined, as well as molecular markers in tumors from bone biopsies. In mice harboring PDX intrafemurally or subcutaneously, cabozantinib effects on tumor growth, MET, PDX in which MET was silenced, VEGFR2, bone turnover, angiogenesis, and resistance were examined.


RESULTS
In responsive patients and PDX, islets of viable pMET-positive tumor cells persisted, which rapidly regrew after drug withdrawal. Knockdown of MET in PDX did not affect tumor growth in mice nor did it affect cabozantinib-induced growth inhibition but did lead to induction of FGFR1. Inhibition of VEGFR2 and MET in endothelial cells reduced the vasculature, leading to necrosis. However, each islet of viable cells surrounded a VEGFR2-negative vessel. Reduction of bone turnover was observed in both cohorts.


CONCLUSIONS
Our studies demonstrate that MET in tumor cells is not a persistent therapeutic target for metastatic castrate-resistant prostate cancer (CRPC), but inhibition of VEGFR2 and MET in endothelial cells and direct effects on osteoblasts are responsible for cabozantinib-induced tumor inhibition. However, vascular heterogeneity represents one source of primary therapy resistance, whereas induction of FGFR1 in tumor cells suggests a potential mechanism of acquired resistance. Thus, integrated cross-species investigations demonstrate the power of combining preclinical models with clinical trials to understand mechanisms of activity and resistance of investigational agents.
Department of Genitourinary Medical Oncology, David H. Koch Center for Applied Research of Genitourinary Cancers, The University of Texas MD Anderson Cancer Center, Houston, Texas.
Andreas
A
Varkaris
Department of Genitourinary Medical Oncology, David H. Koch Center for Applied Research of Genitourinary Cancers, The University of Texas MD Anderson Cancer Center, Houston, Texas.
Paul G
PG
Corn
Department of Genitourinary Medical Oncology, David H. Koch Center for Applied Research of Genitourinary Cancers, The University of Texas MD Anderson Cancer Center, Houston, Texas.
Nila U
NU
Parikh
Department of Genitourinary Medical Oncology, David H. Koch Center for Applied Research of Genitourinary Cancers, The University of Texas MD Anderson Cancer Center, Houston, Texas.
Eleni
E
Efstathiou
Department of Genitourinary Medical Oncology, David H. Koch Center for Applied Research of Genitourinary Cancers, The University of Texas MD Anderson Cancer Center, Houston, Texas.
Jian H
JH
Song
Department of Genitourinary Medical Oncology, David H. Koch Center for Applied Research of Genitourinary Cancers, The University of Texas MD Anderson Cancer Center, Houston, Texas. Department of Translational Molecular Pathology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
Yu-Chen
YC
Lee
Department of Genitourinary Medical Oncology, David H. Koch Center for Applied Research of Genitourinary Cancers, The University of Texas MD Anderson Cancer Center, Houston, Texas.
Ana
A
Aparicio
Department of Genitourinary Medical Oncology, David H. Koch Center for Applied Research of Genitourinary Cancers, The University of Texas MD Anderson Cancer Center, Houston, Texas.
Anh G
AG
Hoang
Department of Genitourinary Medical Oncology, David H. Koch Center for Applied Research of Genitourinary Cancers, The University of Texas MD Anderson Cancer Center, Houston, Texas. Programs in Cancer Biology and Cancer Metastasis, The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, Texas.
Sanchaika
S
Gaur
Department of Genitourinary Medical Oncology, David H. Koch Center for Applied Research of Genitourinary Cancers, The University of Texas MD Anderson Cancer Center, Houston, Texas. Programs in Cancer Biology and Cancer Metastasis, The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, Texas.
Lynnelle
L
Thorpe
Department of Genitourinary Medical Oncology, David H. Koch Center for Applied Research of Genitourinary Cancers, The University of Texas MD Anderson Cancer Center, Houston, Texas.
Sankar N
SN
Maity
Programs in Cancer Biology and Cancer Metastasis, The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, Texas. Department of Cancer Biology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
Menashe
M
Bar Eli
Department of Pathology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
Bogdan A
BA
Czerniak
Department of Imaging Physics-Research, The University of Texas MD Anderson Cancer Center, Houston, Texas.
Yiping
Y
Shao
Department of Cancer Systems Imaging, The University of Texas MD Anderson Cancer Center, Houston, Texas.
Mian
M
Alauddin
Department of Genitourinary Medical Oncology, David H. Koch Center for Applied Research of Genitourinary Cancers, The University of Texas MD Anderson Cancer Center, Houston, Texas. Department of Translational Molecular Pathology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
Sue-Hwa
SH
Lin
Department of Genitourinary Medical Oncology, David H. Koch Center for Applied Research of Genitourinary Cancers, The University of Texas MD Anderson Cancer Center, Houston, Texas.
Christopher J
CJ
Logothetis
Department of Genitourinary Medical Oncology, David H. Koch Center for Applied Research of Genitourinary Cancers, The University of Texas MD Anderson Cancer Center, Houston, Texas. Programs in Cancer Biology and Cancer Metastasis, The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, Texas. ggallick@mdanderson.org.
Gary E
GE
Gallick
D000813:Anilides / Q000494:pharmacology* / Q000627:therapeutic use; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology* / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects; D001859:Bone Neoplasms / Q000175:diagnosis / Q000556:secondary; D045744:Cell Line, Tumor; D017322:Clinical Trials, Phase II as Topic; D004195:Disease Models, Animal; D019008:Drug Resistance, Neoplasm; D055785:Gene Knockdown Techniques; D006801:Humans; D008297:Male; D051379:Mice; D015337:Multicenter Studies as Topic; D009367:Neoplasm Staging; D010766:Phosphorylation; D049268:Positron-Emission Tomography; D011471:Prostatic Neoplasms / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology* / Q000627:therapeutic use; D019859:Proto-Oncogene Proteins c-met / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011725:Pyridines / Q000494:pharmacology* / Q000627:therapeutic use; D051496:Receptor, Fibroblast Growth Factor, Type 1 / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D016896:Treatment Outcome; D047368:Tumor Burden / Q000187:drug effects; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D023041:Xenograft Model Antitumor Assays
D000813:Anilides; D000970:Antineoplastic Agents; D047428:Protein Kinase Inhibitors; D011725:Pyridines; C558660:cabozantinib; D019859:Proto-Oncogene Proteins c-met; D051496:Receptor, Fibroblast Growth Factor, Type 1; D040301:Vascular Endothelial Growth Factor Receptor-2