The Disaccharide Moiety of Bleomycin Facilitates Uptake by Cancer Cells

Abstract

The disaccharide moiety is responsible for the tumor cell targeting properties of bleomycin (BLM). While the aglycon (deglycobleomycin) mediates DNA cleavage in much the same fashion as bleomycin, it exhibits diminished cytotoxicity in comparison to BLM. These findings suggested that BLM might be modular in nature, composed of tumor-seeking and tumoricidal domains. To explore this possibility, BLM analogues were prepared in which the disaccharide moiety was attached to deglycobleomycin at novel positions, namely, via the threonine moiety or C-terminal substituent. The analogues were compared with BLM and deglycoBLM for DNA cleavage, cancer cell uptake, and cytotoxic activity. BLM is more potent than deglycoBLM in supercoiled plasmid DNA relaxation, while the analogue having the disaccharide on threonine was less active than deglycoBLM and the analogue containing the C-terminal disaccharide was slightly more potent. While having unexceptional DNA cleavage potencies, both glycosylated analogues were more cytotoxic to cultured DU145 prostate cancer cells than deglycoBLM. Dye-labeled conjugates of the cytotoxic BLM aglycons were used in imaging experiments to determine the extent of cell uptake. The rank order of internalization efficiencies was the same as their order of cytotoxicities toward DU145 cells. These findings establish a role for the BLM disaccharide in tumor targeting/uptake and suggest that the disaccharide moiety may be capable of delivering other cytotoxins to cancer cells. While the mechanism responsible for uptake of the BLM disaccharide selectively by tumor cells has not yet been established, data are presented which suggest that the metabolic shift to glycolysis in cancer cells may provide the vehicle for selective internalization.

Facile synthesis of magnetic core–shell nanocomposites for MRI and CT bimodal imaging

“…4C and D) cell lines to perform cellular cytotoxicity experiments. 21 The HUVEC and HeLa cells were incubated with 7 mM ION@Bi 2 S 3 nanocomposites (iron concentration 4.3 mM) at 37 1C for 24 h. The cells were washed with phosphate-buffered saline (PBS) solution three times to remove residual PEG-ION@Bi 2 S 3 coreshell nanocomposites. They were then observed through optical microscopy.…”

Nanoscale TiO2 nanotubes govern the biological behavior of human glioma and osteosarcoma cells

“…The MTT assay was performed according to the previous report, with minor modifications. 31 Each sample (200 μL) was seeded in a 96-well plate in five duplicates. MTT (20 μL, 5 mg/mL; Sigma-Aldrich) was added to each well, and the mixture was incubated at 37°C for an additional 4 hours.…”

Structural Changes of Zn(II)bleomycin Complexes When Bound to DNA Hairpins Containing the 5′-GT-3′ and 5′-GC-3′ Binding Sites, Studied through NMR Spectroscopy

“…BLMs have been used as chemotherapeutic agents in the clinical treatment of a wide spectrum of cancers, and their antitumor activity is generally proposed to be related to destroying the structure of single-stranded or double-stranded DNA in carcinoma cells [2–4]. The overall structure of these agents can be thought of as containing four distinct regions (Figure 1): the metal binding domain (D1), which is responsible for metal binding [5,6], oxygen activation [5,7–9], and site-selective DNA cleavage [6,10]; the peptide linker (D2); the DNA binding domain (D3), containing a bithiazole moiety and the C-terminus, which provides the majority of the DNA binding affinity [11,12]; and the disaccharide moiety (D4), which influences metal ion binding [6,13–24] and is a tumor-targeting unit [25]. …”