Investigation of cytotoxic/toxic and anticancer potential of new fluoroquinolone
Michaela Janošková 1
Viktor Milata 2
Soňa Jantová 1
1 Ústav biochémie a mikrobiológie, Fakulta chemickej a potravinárskej technológie STU v Bratislave, Bratislava, Slovenská republika 2 Oddelenie organickej chémie, Fakulta chemickej a potravinárskej technológie STU v Bratislave, Bratislava, Slovenská republika
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Fluoroquinolones are known as synthetic quinolone anti-bacterial agents which have been the subject of many research interests. Recent reports have shown the importance of fluoroquinolones as anti-tumor agents. Previous reports focusing on the ability of fluoroquinolones to induce apoptosis and cell cycle arrest in various cancer cell lines alone or in combination with other chemotherapeutic agents have rendered them unique among other antibiotic family members.
Ciprofloxacin and other fluoroquinolone derivatives like ofloxacin, levofloxacin, enoxacin and fleroxacin were shown to inhibit the growth of many cancer cells. Also, some of ciprofloxacin derivatives, analogues and complexes showed potent in vitro anti-tumor activity against several cancer cell lines – leukemia, colon cancer, CNS cancer, melanoma, ovarian cancer, renal cancer, prostate cancer, breast cancer (1-3).
Based on the reported effects of fluoroquinolone derivatives, a new series of 1,4-dihydro-4-oxoquinoline substituted at 4-pyridone or/and benzene moieties were prepared and screened for photochemical, cytotoxic and phototoxic activities in vitro. The highest cytotoxic/anti-proliferative activity on human promyelocytic leukemia cell line HL-60 in MTT test exhibited fluoroquinolone ethyl 6-fluoro-8-nitro-4-oxo-1,4-dihydroquinoline-3-carboxylate (6FN) (4).
The aim of the present study was to determine cytotoxicity of 6FN on cancer cell line B16, non-cancer fibroblast NIH-3T3 cells and reconstructed human epidermis tissues EpiDermTM. Further we investigated the ability of 6FN to induce apoptosis in cancer cells.
Fluoroquinolone engendered cytotoxic effects depending on concentration and time of exposure. The highest derivative concentrations (100 and 50 µM) induced an acute cytotoxic effect on cancer cells which was displayed by the immediate 100% cell growth inhibition or degeneration of cell population. After 72 h of treatment, the degeneration of the entire cell population was found. On the other hand, the cell degeneration/inhibition of non-cancer NIH-3T3 cells during the whole experiment caused only derivative concentration of 100 µM. The concentration of 50 µM evocated total cell growth inhibition only at 48 h of influence, in the next 24 h, the cell proliferation was observed. After 72 h of exposure with derivative concentrations of 40 and 25 µM, the cell proliferation was 10.8% and 17.3%. The proliferation of NIH-3T3 cells treated with the other tested concentrations (1, 5 and 10 µM) was in the range 28.2%–81.6%. Comparison of IC100 values showed that the senstivity of cancer cells was higher in comparison to non-cancer cells.
The actions of some quinolones against skin cancer and cutaneous metastases were studied. For example, Imiquimod is a topical quinolone immunomodulator with antineoplastic action, its cream is an effective and safe for melanoma metastese treatment (5,6). Therefore we used skin model EpiDermTM for toxicity observation of 6FN, which could be topical administered in connection with melanoma treatment. Viability test, morphological and histological studies showed that only derivative concentration of 100 µM induced the massive toxicity on human three-dimensional skin constructs EpiDerm™ and significant structural and morphologic damage in tissue. This toxic effect was accompanied by 45.5% decrease of tissue viability and deficit of layer stratum granulosum in EpiDermTM structure. The fluoroquinolone concentration of 50 µM caused weaker effect, only 25.8% tissue toxicity was found after 72 of treatment.
Aberrant regulation of apoptosis mechanism is an important pathological factor in a variety of major human diseases. Failure to appropriately engage of this pathway is one of the hallmarks of cancer development, and many cancer cells exhibit significant resistance to apoptosis signalling. Therefore new apoptosis-inductive agents are required for better efficacy and side effects reduction.
Such, the ability to induce apoptosis in cancer cells B16 treated with 6FN was further examined. Agarose gel electrophoresis shown that all tested concentrations induced the formation of apoptotic DNA fragments during the whole experiment. The DNA fragmentation observed in B16 cells was concentration-dependent. Analysis of the stained cells showed, that 6FN-treated B16 cells had a typical apoptotic morphological changes in the nuclear chromatin (condensed and fragmented nuclei) and stained with Hoechst 33258.
Based on these results, it could be assumed, that 6FN may have a potential use as a novel chemotherapeutic agent. Nevertheless, further studies are needed.
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