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Therapeutic Efficacy of Seliciclib in Combination with Ionizing Radiation for Human Nasopharyngeal Carcinoma
Ist Teil von
Clinical cancer research, 2009-06, Vol.15 (11), p.3716-3724
Ort / Verlag
Philadelphia, PA: American Association for Cancer Research
Erscheinungsjahr
2009
Quelle
MEDLINE
Beschreibungen/Notizen
Purpose: Seliciclib is a small-molecule cyclin-dependent kinase inhibitor, which has been reported to induce apoptosis and cell cycle
arrest in EBV-negative nasopharyngeal carcinoma cell lines. Because most nasopharyngeal carcinoma patients harbor EBV, we
proceeded to evaluate the cytotoxic effects of seliciclib in EBV-positive nasopharyngeal carcinoma models.
Experimental Design: Cytotoxicity of seliciclib was investigated in the EBV-positive cell line C666-1 and the C666-1 and C15 xenograft models.
Caspase activities and cell cycle analyses were measured by flow cytometry. Efficacy of combined treatment of seliciclib with
radiation therapy was also evaluated.
Results: Seliciclib caused significant cytotoxicity in the C666-1 cells in a time- and dose-dependent manner, with accumulation of
cells in both sub-G 1 and G 2 -M phases, indicative of apoptosis and cell cycle arrest, respectively. Caspase-2, -3, -8, and -9 activities were all increased,
with caspase-3 being the most significantly activated at 48 h after treatment. These cells also showed a reduction of Mcl-1
mRNA and protein levels. Combined treatment of seliciclib with radiation therapy showed a synergistic interaction with enhanced
cytotoxicity in C666-1 cells and delayed repair of double-strand DNA breaks. For in vivo models, significant delays in tumor growth were observed for both C666-1 and C15 tumors, which were associated with enhanced
apoptosis as determined by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling and immunohistochemistry
analyses.
Conclusions: Seliciclib enhanced the antitumor efficacy of radiation therapy in EBV-positive nasopharyngeal carcinoma, characterized by
G 2 -M arrest, and apoptosis, associated with an induction in caspase activity. This process is mediated by reduction in Mcl-1
expression and by attenuation of double-strand DNA break repair.