Synthesis and evaluation of fluoromycin : a novel fluorescence-labeled derivative of talisomycin S10b

• Published in: Cancer research (Chicago, Ill.) Ill.), 1992-02, Vol.52 (3), p.709-718
• Main Authors: MISTRY, J. S, JANI, J. P, MORRIS, G, MUJUMDAR, R. B, REYNOLDS, I. J, SEBTI, S. M, LAZO, J. S
• Format: Article
• Language: English
• Subjects: Antineoplastic agents; Antineoplastic Agents - chemical synthesis; Biological and medical sciences; Bleomycin - chemical synthesis; Bleomycin - chemistry; Bleomycin - metabolism; Bleomycin - pharmacology; Carcinoma, Squamous Cell; Cell Division - drug effects; Cell Line; Chromatography, High Pressure Liquid; Drug Screening Assays, Antitumor; Fluoresceins - chemical synthesis; Fluoresceins - chemistry; Fluoresceins - pharmacology; Fluorescent Dyes; General aspects; Head and Neck Neoplasms; Humans; Indicators and Reagents; Medical sciences; Molecular Structure; Pharmacology. Drug treatments; Plasmids - drug effects
• ISSN: 0008-5472; 1538-7445

We have synthesized fluoromycin (FLM), a novel fluorescein-labeled derivative of talisomycin S10b (TLM S10b), and used it to evaluate cellular drug accumulation and distribution in bleomycin (BLM)-sensitive and -resistant cell lines. The fluorescence intensity of FLM was 300- to 400-fold greater than that of BLM A2, TLM S10b, or the lipophilic BLM analogue, liblomycin. FLM possessed an antiproliferative potency similar to liblomycin in BLM-sensitive human A-253 squamous carcinoma cells but was less potent than BLM A2 or TLM S10b. C-10E cells, a clone of A-253 cells with 40- to 50-fold resistance to BLM A2 and TLM S10b, were 50-fold resistant to FLM. A partially revertant cell population (C-10E ND) regained sensitivity to BLM A2, TLM S10b, and FLM. FLM like BLM cleaved pGEM-3Z plasmid DNA in vitro in a concentration-dependent manner. Flow cytometric analysis of FLM content in C-10E and C-10E ND cell lines showed 4-fold and 2-fold lower fluorescence intensity, respectively, compared with A-253 cells. Similar results were seen by fluorescence spectrophotometry with cell extracts. Fluorescence microscopy indicated heterogeneous distribution among A-253 cells with at least 50% of the cells exhibiting marked nuclear fluorescence localization. In contrast, C-10E cells displayed lower cellular fluorescence and predominantly cytoplasmic localization. C-10E ND cells exhibited a mixed population of nuclear and cytoplasmic vesicular localization with fluorescence levels that were intermediate between A-253 and C-10E cells. Thus, BLM-resistant cells have reduced levels of FLM and appear to have a lower nuclear:cytoplasmic ratio of FLM. FLM may be useful in studying the intracellular fate of BLM-like drugs as well as providing a tool to detect and isolate BLM-resistant cells.