carbocyanines and Medulloblastoma

Bioconjugates composed of chlorotoxin and near-infrared fluorescent (NIRF) moieties are being advanced toward human clinical trials as intraoperative imaging agents that will enable surgeons to visualize small foci of cancer. In previous studies, the NIRF molecules were conjugated to chlorotoxin, which results in a mixture of mono-, di-, and trilabeled peptide. Here we report a new chemical entity that bound only a single NIRF molecule. The lysines at positions 15 and 23 were substituted with either alanine or arginine, which resulted in only monolabeled peptide that was functionally equivalent to native chlorotoxin/Cy5.5. We also analyzed the serum stability and serum half-life of cyclized chlorotoxin, which showed an 11 h serum half-life and resulted in a monolabeled product. Based on these data, we propose to advance a monolabeled chlorotoxin to human clinical trials.

Topics: Alanine; Amino Acid Sequence; Amino Acid Substitution; Animals; Arginine; Brain Neoplasms; Carbocyanines; Fluorescent Dyes; Half-Life; Lysine; Medulloblastoma; Mice; Mice, Inbred C57BL; Models, Molecular; Molecular Sequence Data; Peptides; Peptides, Cyclic; Scorpion Venoms

The search for improved photosensitizers for laser phototherapy of malignancies has led to the examination of a new group of carbocyanine dyes as effective fluorochromes. In this study, four carbocyanine dyes with different absorption maxima of 483 nm [DiOC6(3)], 545.5 nm (DiIC5(3)], 556.6 nm [DiSC5(3)], and 651.0 nm [DiSC3(5)] were tested in vitro. The kinetics of uptake and toxicity of these four dyes were assessed for P3 human squamous cell carcinoma, HT29 colon carcinoma, M26 melanoma, and TE671 fibrosarcoma cell lines at 15, 30, 45, 60, and 180 minutes after exposure with each dye. After sensitization with DiOC6(3), the P3 and M26 cell lines were also tested for phototherapy by treatment with 488-nm light from an argon laser. The results showed that these four carbocyanine dyes had rapid and significant uptake by the carcinoma cell lines with no toxicity at concentrations < 0.1 micrograms/mL. Nontoxic DiOC6(3) levels in sensitized tumor cells after laser phototherapy resulted in approximately 85% inhibition of P3 and approximately 95% inhibition of M26 cell lines by MTT assays. The results suggest that these carbocyanine dyes can be used for tumor photosensitization and wavelength-matched laser photodynamic therapy. Further in vivo studies will be necessary to define the clinical potential of carbocyanine dyes as tumor-targeting agents for phototherapy of cancer.

Topics: Adenocarcinoma; Argon; Benzothiazoles; Carbocyanines; Carcinoma, Squamous Cell; Cell Survival; Colonic Neoplasms; Fibrosarcoma; Fluorescent Dyes; Humans; Laser Therapy; Lung Neoplasms; Medulloblastoma; Melanoma; Neoplasms; Photochemotherapy; Tetrazolium Salts; Tumor Cells, Cultured