(212)Pb-radioimmunotherapy induces G(2) cell-cycle arrest and delays DNA damage repair in tumor xenografts in a model for disseminated intraperitoneal disease

Mol Cancer Ther. 2012 Mar;11(3):639-48. doi: 10.1158/1535-7163.MCT-11-0671. Epub 2012 Jan 11.


In preclinical studies, targeted radioimmunotherapy using (212)Pb-TCMC-trastuzumab as an in vivo generator of the high-energy α-particle emitting radionuclide (212)Bi is proving an efficacious modality for the treatment of disseminated peritoneal cancers. To elucidate mechanisms associated with this therapy, mice bearing human colon cancer LS-174T intraperitoneal xenografts were treated with (212)Pb-TCMC-trastuzumab and compared with the nonspecific control (212)Pb-TCMC-HuIgG, unlabeled trastuzumab, and HuIgG, as well as untreated controls. (212)Pb-TCMC-trastuzumab treatment induced significantly more apoptosis and DNA double-strand breaks (DSB) at 24 hours. Rad51 protein expression was downregulated, indicating delayed DNA double-strand damage repair compared with (212)Pb-TCMC-HuIgG, the nonspecific control. (212)Pb-TCMC-trastuzumab treatment also caused G(2)-M arrest, depression of the S phase fraction, and depressed DNA synthesis that persisted beyond 120 hours. In contrast, the effects produced by (212)Pb-TCMC-HuIgG seemed to rebound by 120 hours. In addition, (212)Pb-TCMC-trastuzumab treatment delayed open chromatin structure and expression of p21 until 72 hours, suggesting a correlation between induction of p21 protein and modification in chromatin structure of p21 in response to (212)Pb-TCMC-trastuzumab treatment. Taken together, increased DNA DSBs, impaired DNA damage repair, persistent G(2)-M arrest, and chromatin remodeling were associated with (212)Pb-TCMC-trastuzumab treatment and may explain its increased cell killing efficacy in the LS-174T intraperitoneal xenograft model for disseminated intraperitoneal disease.

Publication types

  • Research Support, N.I.H., Intramural

MeSH terms

  • Animals
  • Antibodies, Monoclonal, Humanized / chemistry
  • Antibodies, Monoclonal, Humanized / therapeutic use*
  • Antineoplastic Agents / chemistry
  • Antineoplastic Agents / therapeutic use
  • Apoptosis / drug effects
  • Apoptosis / radiation effects
  • Blotting, Western
  • Cell Cycle Checkpoints / drug effects
  • Cell Cycle Checkpoints / radiation effects
  • Cell Line, Tumor
  • Cell Proliferation / drug effects
  • Cell Proliferation / radiation effects
  • Colonic Neoplasms / genetics
  • Colonic Neoplasms / metabolism
  • Colonic Neoplasms / radiotherapy*
  • Cyclin-Dependent Kinase Inhibitor p21 / metabolism
  • DNA Breaks, Double-Stranded / drug effects
  • DNA Breaks, Double-Stranded / radiation effects
  • DNA Repair / drug effects
  • DNA Repair / radiation effects
  • Female
  • Flow Cytometry
  • G2 Phase / drug effects
  • G2 Phase / radiation effects
  • Heterocyclic Compounds / chemistry
  • Humans
  • Immunoglobulin G / chemistry
  • Immunoglobulin G / therapeutic use
  • Isothiocyanates / chemistry
  • Lead Radioisotopes / chemistry
  • Mice
  • Mice, Nude
  • Peritoneal Neoplasms / genetics
  • Peritoneal Neoplasms / metabolism
  • Peritoneal Neoplasms / radiotherapy
  • Radioimmunotherapy / methods*
  • Time Factors
  • Trastuzumab
  • Xenograft Model Antitumor Assays*


  • 2-(4-isothiocyanatobenzyl)-1,4,7,10--tetraaza-1,4,7,10-tetra-(2-carbamoylmethyl)cyclododecane
  • Antibodies, Monoclonal, Humanized
  • Antineoplastic Agents
  • Cyclin-Dependent Kinase Inhibitor p21
  • Heterocyclic Compounds
  • Immunoglobulin G
  • Isothiocyanates
  • Lead Radioisotopes
  • Trastuzumab