Cell growth-inhibition and cell cycle perturbations induced by a new synthetic iminoquinone, 5H-pyridophenoxazin-5-one, in human breast carcinoma cell lines.

5H-Pyridophenoxazin-5-one (PPH) is a new synthetic iminoquinone which has showed to be a potent cytotoxic agent on different cancer cell lines. PPH effects depend by the intercalation into the DNA double strand at the middle 5′-GC-3′ base pairs of the octamer [d(GAAGCTTC)2] and the production, under bio reductive conditions, of free oxygen radicals. The aim of the study was to analyse cell growth and cell cycle kinetics of MCF-7 (p53 wt) and MDA-MB-468 (p53 mut) human breast cancer cell lines after PPH exposure. Treatments were performed with different PPH concentrations (ranging from 0.5 μM up 8 μM) as pulsed (60 min/exposure) or continuous exposure. MCF-7 cells were more sensitive to pulsed treatment than MDA-MB-468 cell line. Cell cycle analysis by PI staining showed a G2M perturbation that was overcome after 72 hours in both cell lines. As expected, continuous treatment caused a strongest cell-growth inhibition and cell cycle perturbation in both cell lines. However, DNA-flow cytometry showed that MCF-7 cells cytotoxicity correlate with an accumulation of cells in the S phase, whereas an irreversible G2M block accompanied MDA-MB-468 cytotoxicity

Inhibition of NF-kB activity potentiates ionizing radiation and cisplatin induced cell killing of anaplastic thyroid carcinoma cells AACR Meeting Abstracts, Apr 2006; 2006: 1038.

Aim: Nuclear factor kB (NF-kB ) is a transcriptional factor found to be involved in inflammatory response regulation, apoptosis and carcinogenesis. Recently NF-kB activity has been implicated in drug and ionizing radiation resistance of different types of cancer cells. Anaplastic thyroid carcinoma is an aggressive neoplasm, usually refractory to conventional treatment and fatal, in which activation of NF-kB has been shown. Aim of this work was to evaluate the impact of NF-kB activity inhibition on sensitivity to ionizing radiation (IR) and cisplatin (CDDP) of FRO cell line, an in vitro model of anaplastic thyroid carcinoma. Materials and Methods: FRO cells were transfected with pcDNA3-flag-IkBaM vector in order to select a clone overexpressing a mutant super repressor ligand of NF-kB, IkBaM, to generate a cell line with constitutively suppressed NF-kB activity. The FRO wild type and the clone 14 of the cells overexpressing IkBaM, FRO14, were exposed to different doses of IR (1, 2 and 4Gy) and CDDP (1, 10 and 20 mcM) either in the presence or not of a 5 mcM concentration of curcumin, a natural compound showed to have NF-kB inhibitor property. Survival was assessed by clonogenic assay for the IR exposure and by MTT assay for CDDP treatment. The difference in sensitivity was evaluated for the end point of a growth inhibition of 50% by a gaining factor representing the ratio between the dose to obtain 50% survival inhibition (I.D.50) in FRO cell line and the dose to obtain the same end point in FRO14. Evaluation of cell cycle perturbation and apoptosis was assessed by cytofluorimetric evaluation. Results: The I.D.50 in the IR experiments resulted 2.4 Gy for FRO and 1.8 Gy for FRO14 with a gaining factor of 1.3 in the sensitivity of FRO14. The I.D.50 in the CDDP experiments resulted 17 mcM for FRO and 7 mcM for FRO14 with a gaining factor of 2.4 in the sensitivity of FRO14. Curcumin augmented IR and CDDP toxicity in both cell lines. No change was detected in the rate of apoptosis in the different cell lines. Accumulation in the fase S of the cell cycle was showed by radiation and curcumin treatment in the FRO 14 cell line. Conclusion: Constitutive inhibition of NF-kB activity resulted in augmentation of cell killing by both IR and CDDP that does not seem to be linked to change in apoptotic rate. Treatment with curcumin augments cytotoxicity of IR and CDDP in both the cell lines. The data of our experiments suggest that NF-kB targeting may be a useful clinical strategy to augment the effectiveness of conventional anticancer treatments in anaplastic thyroid carcinoma. Moreover there is a strong suggestion that curcumin may be a suitable complement to conventional anticancer therapies