Preclinical studies of bismuth-213 labeled plasminogen activator inhibitor type 2 (PAI2) in a prostate cancer nude mouse xenograft model.
OBJECTIVE
The key objective of the study was to determine the single and multiple dose toxicity and efficacy of Bismuth-213 labeled PAI2 based targeted alpha therapy by selectively targeting uPA and uPAR in regressing prostate cancer in a nude mouse model. Targeted alpha therapy (TAT) is an experimental therapeutic modality for cancer. Another objective was to compare the in vivo pharmacokinetics using two different chelators to form the radioisotope-protein construct.


METHODS
The single and multiple intra-peritoneal (IP) dose toxicity and efficacy of 213BiPAI2 was investigated in nude mice and its toxicity in rabbits. CD 31 staining for vasculature and uPA expression were measured at different stages of tumor growth. The pharmacokinetics of the chelators cDTPA and CHX-A'' were measured.


RESULTS
All TAT regimes were well tolerated in mice and rabbits on biochemical and haematological examination. Capillaries became evident at six days post-cell inoculation. uPA expression was positive at all stages of tumour growth. No significant differences were observed between cDTPA and CHX-A. '' Inhibition of tumour growth was observed at 947 and 1421 MBq/kg single dose injection at three days post-PC3 cell inoculation. The three day post-inoculation multiple dose regime gave complete tumour growth inhibition at a total dose of 947 MBq/kg given on five successive days. Mice treated at 6, 12 and 18 days post-inoculation showed significantly slower tumour growth compared to controls.


CONCLUSIONS
The efficacy of single and multiple dose TAT in mice was demonstrated within tolerance limits, the multiple dose regime being no more toxic than the single dose. Either of the two chelators could be used for 213Bi studies.
Abbas Rizvi
Syed M
SM
Center for Experimental Radiation Oncology (CERO), Division of Cancer Services, St. George Hospital, Gray Street, Kogarah, NSW 2217, Australia. syed.rizvi@sesiahs.health.nsw.gov.au
Li
Yong
Y
Song
Emma Yan Jun
EY
Qu
Chang Fa
CF
Raja
Chand
C
Morgenstern
Alfred
A
Apostolidis
Christos
C
Allen
Barry J
BJ
D000818:Animals; D001729:Bismuth / Q000494:pharmacology*; D002614:Chelating Agents / Q000494:pharmacology; D003513:Cycloheximide / Q000494:pharmacology; D006801:Humans; D008297:Male; D051379:Mice; D008819:Mice, Nude; D009362:Neoplasm Metastasis; D009368:Neoplasm Transplantation; D004369:Pentetic Acid / Q000494:pharmacology; D017396:Plasminogen Activator Inhibitor 2 / Q000737:chemistry / Q000378:metabolism*; D011471:Prostatic Neoplasms / Q000628:therapy*; D011817:Rabbits; D011868:Radioisotopes / Q000494:pharmacology*; D015842:Serine Proteinase Inhibitors / Q000494:pharmacology
D002614:Chelating Agents; D017396:Plasminogen Activator Inhibitor 2; D011868:Radioisotopes; D015842:Serine Proteinase Inhibitors; D004369:Pentetic Acid; D003513:Cycloheximide; D001729:Bismuth