Preclinical characterization of mitochondria-targeted small molecule hsp90 inhibitors, gamitrinibs, in advanced prostate cancer.
OBJECTIVE
This study aimed to characterize the preclinical activity of the first class of combinatorial, mitochondria-targeted, small molecule heat shock protein-90 (Hsp90) inhibitors, gamitrinibs, in models of hormone-refractory, drug-resistant, localized, and bone metastatic prostate cancer in vivo.


METHODS
Mitochondrial permeability transition, apoptosis, and changes in metabolic activity were examined by time-lapse videomicroscopy, multiparametric flow cytometry, MTT, and analysis of isolated mitochondria. Drug-resistant prostate cancer cells were generated by chronic exposure of hormone-refractory PC3 cells to the Hsp90 inhibitor 17-allylaminogeldanamycin (17-AAG). The effect of gamitrinibs on s.c. or intratibial prostate cancer growth was studied in xenograft models. Bone metastatic tumor growth and bone parameters were quantified by micro-computed tomography imaging.


RESULTS
In the NCI 60-cell line screening, gamitrinibs were active against all tumor cell types tested, and efficiently killed metastatic, hormone-refractory, and multidrug-resistant prostate cancer cells characterized by overexpression of the ATP binding cassette transporter P-glycoprotein. Mechanistically, gamitrinibs, but not 17-AAG, induced acute mitochondrial dysfunction in prostate cancer cells with loss of organelle membrane potential, release of cytochrome c, and caspase activity, independently of proapoptotic Bcl-2 proteins Bax and Bak. Systemic administration of gamitrinibs to mice was well tolerated, and inhibited s.c. or bone metastatic prostate cancer growth in vivo.


CONCLUSIONS
Gamitrinibs have preclinical activity and favorable safety in models of drug-resistant and bone metastatic prostate cancer in vivo.
Kang
Byoung Heon
BH
Department of Cancer Biology, University of Massachusetts Medical School, Worcester, USA.
Siegelin
Markus D
MD
Plescia
Janet
J
Raskett
Christopher M
CM
Garlick
David S
DS
Dohi
Takehiko
T
Lian
Jane B
JB
Stein
Gary S
GS
Languino
Lucia R
LR
Altieri
Dario C
DC
D000818:Animals; D000970:Antineoplastic Agents / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D016227:Benzoquinones / Q000494:pharmacology; D049109:Cell Proliferation / Q000187:drug effects; D018450:Disease Progression; D004305:Dose-Response Relationship, Drug; D004354:Drug Screening Assays, Antitumor; D018841:HSP90 Heat-Shock Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D006801:Humans; D007769:Lactams / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D047029:Lactams, Macrocyclic / Q000494:pharmacology; D008297:Male; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D051379:Mice; D016513:Mice, SCID; D008928:Mitochondria / Q000187:drug effects*; D008970:Molecular Weight; D011471:Prostatic Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D011743:Pyrimidines / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D011809:Quinones / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D014407:Tumor Cells, Cultured; D055114:X-Ray Microtomography
D000970:Antineoplastic Agents; D016227:Benzoquinones; D018841:HSP90 Heat-Shock Proteins; D007769:Lactams; D047029:Lactams, Macrocyclic; D011743:Pyrimidines; D011809:Quinones; C112765:tanespimycin