title: PET imaging of CCND1 mRNA in human MCF7 estrogen receptor positive breast cancer xenografts with oncogene-specific [64Cu]chelator-peptide nucleic acid-IGF1 analog radiohybridization probes.
abstract: Treatment of breast cancer is hampered by a large unmet need for rapid, sensitive, specific staging and stratification of palpable and nonpalpable abnormalities. Mammography and physical examination miss many early breast cancers, yet detect many benign lesions. Cyclin D1, encoded by CCND1 messenger RNA (mRNA), and insulin-like growth factor 1 receptor (IGF1R) are key regulators of cell proliferation that are overexpressed in most breast cancers. Therefore, we hypothesized that malignant breast masses could be imaged and quantitated externally by PET with a dual-specificity probe that targets both CCND1 mRNA and IGF1R.
  
  
  METHODS
  We designed a CCND1-specific peptide nucleic acid (PNA) hybridization sequence (CTGGTGTTCCAT), separated by a C-terminal spacer to a cyclized IGF1 peptide analog (d-Cys-Ser-Lys-Cys), for IGF1R-mediated endocytosis. On the N-terminus we attached a chelator (1,4,7-tris(carboxymethylaza)cyclododecane-10-azaacetyl [DO3A]) for the positron-emitting nuclide (64)Cu. We administered the [(64)Cu]CCND1-IGF1 analog radiohybridization probes, as well as sequence controls, by tail vein to immunocompromised female NCr mice bearing human MCF7 estrogen-dependent, receptor-positive xenografts. We imaged the mice by PET and CT 4 and 24 h later, and measured tissue distribution of the radiohybridization probes.
  
  
  RESULTS
  We observed 8 +/- 2-fold higher PET intensity in the center of the breast cancer xenografts than in the contralateral tissues at 24 h after injection of the [(64)Cu]CCND1-IGF1 analog radiohybridization probe. IGF1 blocking yielded significantly weaker images (P < 0.05) relative to the tumor-free side at 24 h after injection, as did a PNA mismatch probe, a peptide mismatch probe, and free (64)CuCl(2).
  
  
  CONCLUSIONS
  These results are consistent with our hypothesis for radiohybridization PET of overexpressed CCND1 mRNA, dependent on IGF1R-mediated endocytosis, in suspect masses. Early noninvasive detection of initial cancerous transformation, as well as invasive or recurrent breast cancer, with dual-specificity radiohybridization probes, might enable molecularly targeted staging, stratification, and choice of therapy.
authors.affiliation: Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, Pennsylvania, USA.
authors.forename: Xiaobing
authors.initials: X
authors.lastname: Tian
authors.forename: Mohan R
authors.initials: MR
authors.lastname: Aruva
authors.forename: Kaijun
authors.initials: K
authors.lastname: Zhang
authors.forename: Nylla
authors.initials: N
authors.lastname: Shanthly
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Cardi
authors.forename: Mathew L
authors.initials: ML
authors.lastname: Thakur
authors.forename: Eric
authors.initials: E
authors.lastname: Wickstrom
mesh_terms: D000818:Animals; D001943:Breast Neoplasms / Q000000981:diagnostic imaging* / Q000235:genetics / Q000378:metabolism*; D002614:Chelating Agents; D003301:Copper Radioisotopes / Q000493:pharmacokinetics; D056741:Cyclin D; D016213:Cyclins / Q000235:genetics / Q000378:metabolism*; D003947:Diagnostic Techniques, Radioisotope; D005260:Female; D018390:Gene Targeting / Q000379:methods; D006801:Humans; D006824:Hybridization, Genetic; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000493:pharmacokinetics*; D051379:Mice; D020135:Peptide Nucleic Acids / Q000493:pharmacokinetics; D049268:Positron-Emission Tomography / Q000379:methods; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D011960:Receptors, Estrogen / Q000378:metabolism*; D014018:Tissue Distribution
chemical_list: D002614:Chelating Agents; D003301:Copper Radioisotopes; D056741:Cyclin D; D016213:Cyclins; D020135:Peptide Nucleic Acids; D012333:RNA, Messenger; D019275:Radiopharmaceuticals; D011960:Receptors, Estrogen; D007334:Insulin-Like Growth Factor I