Change in cell death markers during (177)Lu-mAb radioimmunotherapy-induced rejection of syngeneic rat colon carcinoma.
OBJECTIVE
To monitor cell death in tumors during the rejection process after treatment with an antibody radiolabeled with a β-emitter.


METHODS
Tumors during rejection after treatment with (177)Lu-labeled antibody BR96 and after administration of unlabeled BR96 were compared with untreated tumors from the same immunocompetent syngeneic rat tumor model. Cell death was monitored with the terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay and immunohistochemical staining of activated caspase-3 and γH2AX. These data were evaluated together with histopathological morphology, BR96-binding antigen expression, and (177)Lu radioactivity distribution imaged by digital autoradiography.


RESULTS
The untreated tumors showed staining for all the markers, mainly in and around the necrotic areas. One to 2 days p.i. large areas were stained with anti-γH2AX, followed by a slight decrease. Staining of activated caspase-3 was intense and extensive 1-2 days p.i., while found in and around necrotic areas 3-8 days p.i. TUNEL staining was similar to activated caspase-3 staining 1-2 days p.i. but more extensive than activated caspase-3 staining 3-4 days p.i. Digital autoradiography revealed activity concentration in granulation tissue from 1 day p.i.


CONCLUSIONS
Following radioimmunotherapy in an immunocompetent syngeneic colon carcinoma model, tumor cells did not only die through caspase-3-dependent apoptosis, but also by other mechanisms.
1 Division of Oncology, Department of Clinical Sciences, Lund University , Lund, Sweden .
Erika
E
Elgström
Otto
O
Ljungberg
Sophie E
SE
Eriksson
Anders
A
Orbom
Sven-Erik
SE
Strand
Tomas G
TG
Ohlsson
Rune
R
Nilsson
Jan
J
Tennvall
D000818:Animals; D017209:Apoptosis / Q000502:physiology / Q000528:radiation effects*; D053148:Caspase 3 / Q000378:metabolism; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000276:immunology / Q000473:pathology* / Q000532:radiotherapy*; D006801:Humans; D000922:Immunotoxins / Q000276:immunology / Q000494:pharmacology*; D008187:Lutetium / Q000008:administration & dosage*; D008297:Male; D016499:Radioimmunotherapy / Q000379:methods*; D011868:Radioisotopes / Q000008:administration & dosage*; D051381:Rats
D000922:Immunotoxins; D011868:Radioisotopes; D008187:Lutetium; D053148:Caspase 3
177Lu; TUNEL; autoradiography; caspase-3; cell death; radioimmunotherapy; syngeneic model; γH2AX