title: Apoptosis-related gene and protein expression in human lymphoma xenografts (Raji) after low dose rate radiation using 67Cu-2IT-BAT-Lym-1 radioimmunotherapy.
abstract: Despite low radiation dose rates, radioimmunotherapy (RIT) has proven particularly effective in the treatment of malignancies, such as lymphoma. Apoptosis has been suggested to be a major mechanism for cell death from continuous low-dose rate radiation from radioimmunotherapy. The goal of this study was to examine Raji lymphoma xenografts for induction of apoptosis and modulation of apoptosis-related gene and protein expression in response to 67Cu-2IT-BAT-Lym-1 RIT. In preclinical and clinical trials, 67Cu-2IT-BAT-Lym-1 has shown an exceptionally long tumor residence time associated with substantial cumulated radiation doses. The Raji model mirrors human lymphomas that have mutant p53 and increased BCL2 expression. Untreated athymic BALB/c nu/nu mice and mice treated with 400 micrograms Lym-1, or 335-500 microCi 67Cu on less than 400 micrograms Lym-1 antibody, were observed for toxicity and response over 84 days. Subgroups of 4-5 mice were sacrificed at 3, 6 and 24 h after therapy so that tumors could be examined for poly(ADP-ribose) polymerase (PARP) and DNA ladder evidence for apoptosis and for BCL2, p53, p21, GADD45, TGF-beta 1 and c-MYC gene and protein expression. Untreated tumors had little evidence of apoptosis and Lym-1 had no effect on apoptosis or gene expression. 67Cu-2IT-BAT-Lym-1 RIT induced an overall response rate of 50% with tolerable toxicity, and 29% of the tumors were cured at cumulated tumor radiation doses of about 1800 cGy. Apoptosis was greatly increased in the RIT treated Raji xenografts as evidenced by cleavage of PARP to the characteristic 85 kD fragment at 3 and 6 h and by the DNA cleavage pattern. BCL2 gene and protein expression were substantially decreased at 3 and 24 h, respectively, after 67Cu-2IT-BAT-Lym-1 RIT despite only modest cumulated radiation doses (56 cGy at 3 h). Evidence for apoptosis preceded tumor regression by 4-6 days. In these therapy-resistant, human lymphoma tumors treated with 67Cu-2IT-BAT-Lym-1, apoptosis was convincingly demonstrated to be a major mechanism for the effectiveness of RIT and occurred by p53-independent mechanisms.
authors.affiliation: Division of Hematology/Oncology, University of California Davis Medical Center, Sacramento, CA, USA.
authors.forename: L A
authors.initials: LA
authors.lastname: Kroger
authors.forename: G L
authors.initials: GL
authors.lastname: DeNardo
authors.forename: P H
authors.initials: PH
authors.lastname: Gumerlock
authors.forename: C Y
authors.initials: CY
authors.lastname: Xiong
authors.forename: M D
authors.initials: MD
authors.lastname: Winthrop
authors.forename: X B
authors.initials: XB
authors.lastname: Shi
authors.forename: P C
authors.initials: PC
authors.lastname: Mack
authors.forename: T
authors.initials: T
authors.lastname: Leshchinsky
authors.forename: S J
authors.initials: SJ
authors.lastname: DeNardo
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000627:therapeutic use*; D017209:Apoptosis / Q000235:genetics*; D015153:Blotting, Western; D002051:Burkitt Lymphoma / Q000378:metabolism / Q000532:radiotherapy*; D003301:Copper Radioisotopes / Q000627:therapeutic use*; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000235:genetics / Q000378:metabolism; D005260:Female; D015870:Gene Expression; D006571:Heterocyclic Compounds / Q000627:therapeutic use*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D009363:Neoplasm Proteins / Q000235:genetics* / Q000378:metabolism; D009942:Organometallic Compounds / Q000627:therapeutic use*; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D011471:Prostatic Neoplasms / Q000378:metabolism / Q000628:therapy; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics; D012313:RNA / Q000302:isolation & purification / Q000378:metabolism; D016499:Radioimmunotherapy; D019275:Radiopharmaceuticals / Q000627:therapeutic use*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016212:Transforming Growth Factor beta / Q000235:genetics; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000235:genetics; D000097642:GADD45 Proteins
chemical_list: D000911:Antibodies, Monoclonal; D003301:Copper Radioisotopes; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D006571:Heterocyclic Compounds; D047908:Intracellular Signaling Peptides and Proteins; D009363:Neoplasm Proteins; D009942:Organometallic Compounds; D011065:Poly(ADP-ribose) Polymerases; D011506:Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D016271:Proto-Oncogene Proteins c-myc; D012313:RNA; D019275:Radiopharmaceuticals; D016212:Transforming Growth Factor beta; D016159:Tumor Suppressor Protein p53; D000097642:GADD45 Proteins; C493956:CDKN1A protein, human; C493957:Cdkn1a protein, mouse; C097568:copper-67-2IT-BAT-Lym-1