Tag Archives: paclitaxel

Biochemical effects of combined action of γ-irradiation and paclitaxel on anaplastic thyroid cancer cells

V. M. Pushkarev, O. I. Kovzun, V. V. Pushkarev, M. D. Tronko

State Institution V. P. Komisarenko Institute of Endocrinology and Metabolism,
National Academy of Medical Sciences of Ukraine, Kyiv;
e-mail: pushkarev.vm@gmail.com

The aim of the paper was to describe the biochemical effects of Paclitaxel (Ptx), γ-irradiation (IR) and their combination in undifferentiated thyroid cancer cells (ATC). IR activated common DNA damage-induced signaling and manifested certain mitogenic effect by inactivation of retinoblastoma protein (pRb). There was clear antagonism between Ptx and IR relative to cell cycle regulators – tumor suppressor p53, pRb, CHK2 and c-Abl as well as proapoptotic Bax expression, but combined action of both agents enhanced caspase-3 and, especially, caspase-8 activation. The Ptx at low (1-25 nM) concentrations caused noticeable radioprotective effect.
Thus, in ATC cells the ionizing radiation and Ptx exhibited competitive effects upon phosphorylation of cell cycle controllers: p53, pRb, CHK2, cAbl and expression of Вах. At the same time, the combined effect of radiation and Ptx enhanced antiapoptotic Bcl-2 phosphorylation, caspases activation and survivin expression. The net effect of these events during the first 48-72 h of cells incubation can be considered as antiapoptotic – Ptx attenuated cytotoxic effect of IR.

Inhibitor of the transcription factor NF-κB, DHMEQ, enhances the effect of paclitaxel on cells of anaplastic thyroid carcinoma in vitro and in vivo

V. V. Pushkarev1, D. V. Starenki2, V. M. Pushkarev1,
O. I. Kovzun1, M. D. Tronko1

1State Institution V. P. Komisarenko Institute of Endocrinology and Metabolism,
National Academy of Medical Sciences of Ukraine, Kyiv;
e-mail: pushkarev.vm@gmail.com;
2Department of Biochemistry, Medical College of Wisconsin, USA;
e-mail: dstarenki@mcw.edu

Anticancer drug paclitaxel (Ptx) effect on biochemical mechanisms, regulating apoptosis in anaplastic thyroid carcinoma cells, was studied. It was shown that in addition to apoptotic cell death, Ptx induces signa­ling cascades that ensure cell survival. Paclitaxel-induced activation of nuclear factor kappa B (NF‑κВ) leads to an increase of some antiapoptotic proteins expression such as survivin, cIAP, XIAP. A novel NF‑κВ inhibitor, dehydroxymethylepoxyquinomicin (DHMEQ), was found to enhance cytotoxic effect of Ptx in anaplastic thyroid carcinoma cells. An enhancement of caspase-3 and -9 activation and PARP cleavage as well as the decreased levels of proteins-inhibitors of apoptosis were observed when cells were treated with a combination of both drugs. Mitochondria transmembrane potential (ΔΨm) loss was observed at higher concentrations of Ptx and DHMEQ. NF-κВ inhibition also potentiates paclitaxel effect at tumors formed by xenotransplantation of FRO cells into mice. Tumor mass reduction, significantly different from the effects of each of the compounds alone, was observed in animals, treated with paclitaxel and  NF-κВ inhibitor. Thus, the combined use of paclitaxel and NF-κВ inhibitor inhibits biochemical processes that contribute to the resistance of anaplastic thyroid carcinoma cells to paclitaxel action.