The Damaged DNA binding protein 2 (DDB2), is involved in nucleotide excision repair as well as in other biological processes in normal cells, including transcription and cell cycle regulation. Loss of DDB2 function may be related to tumor susceptibility. However, hypothesis of this study was that DDB2 could play a role in breast cancer cell growth, resulting in its well known interaction with the proliferative marker E2F1 in breast neoplasia. DDB2 gene was overexpressed in estrogen receptor (ER)-positive (MCF-7 and T47D), but not in ER-negative breast cancer (MDA-MB231 and SKBR3) or normal mammary epithelial cell lines. In addition, DDB2 expression was significantly (3.0-fold) higher in ER-positive than in ER-negative tumor samples (P = 0.0208) from 16 patients with breast carcinoma. Knockdown of DDB2 by small interfering RNA in MCF-7 cells caused a decrease in cancer cell growth and colony formation. Inversely, introduction of the DDB2 gene into MDA-MB231 cells stimulated growth and colony formation. Cell cycle distribution and 5 Bromodeoxyuridine incorporation by flow cytometry analysis showed that the growth-inhibiting effect of DDB2 knockdown was the consequence of a delayed G1/S transition and a slowed progression through the S phase of MCF-7 cells. These results were supported by a strong decrease in the expression of S phase markers (Proliferating Cell Nuclear Antigen, cyclin E and dihydrofolate reductase). These findings demonstrate for the first time that DDB2 can play a role as oncogene and may become a promising candidate as a predictive marker in breast cancer.
Specific HPV genotypes have been recognized as risk factors inducing head and neck cancers (HNC). The aim of this study was to validate a real-time PCR assay to detect accurately High Risk HPV DNA in Formalin Fixed Paraffin Embedded (FFPE) and oral cytobrush samples and compare the results with conventional PCR. Repeatability, reproducibility and limit of detection of Cobas assay were estimated for oral cytobrush and FFPE samples of patients with HNC. 53 samples of patients with a HNC were then used for assay comparison with conventional PCR. Finally, 26 samples of patients with anogenital neoplasia cancer were analyzed as control and assays comparison. Among the 53 samples of patients with HNC, 12 (26.7%) were HPV positive, 33 (73.3%) were HPV negative and 8 (15.1%) were non contributive with the Cobas assay. Among the 26 samples of patients with anogenital neoplasia, 15 (57.7%) were HPV positive and 11 were HPV negative (42.3%). One sample was found with an HPV 16 and HPV 18 co-infection. Only 3 samples were found with discrepant results. Cobas assay was found suitable for routine HPV detection with a very good repeatability and reproducibility for all HPV genotypes (CV < 0.6% and <0.4% respectively). Sensitivity and specificity for Cobas assay were 91.7% [61.5%;99.8%] and 96.9% [83.8%;99.9%] respectively. Ten nanograms of DNA were sufficient for the detection of HPV 16, HPV 18 and HPV in FFPE and oral cytobrush samples. Cobas assay was found comparable to conventional PCR and can detect accurately and rapidly HPV DNA in FFPE and oral cytobrush samples for the management of HNC and other types of HPV-associated neoplasia.
The effect of chemoresistance induction in radiosensitivity and cellular behavior after irradiation remains misunderstood. This study was designed to understand the relationship between radiation-induced cell cycle arrest, apoptosis, and radiosensitivity in KB cell line and KB3 subline selected after 5-fluorouracil (5FU) exposure. Exposure of KB cells to 5FU led to an increase in radiosensitivity. G2/M cell cycle arrest was observed in the two cell lines after irradiation. The radioresistant KB cell line reached the maximum arrest two hours before KB3. The cellular exit from this arrest was found to be related to the wild type p53 protein expression induction. After irradiation, only KB3 cell line underwent apoptosis. This apoptosis induction seemed to be independent of G2/M arrest exit, which was carried out later. The difference in radiosensitivity between KB and KB3 subline may result therefore from both a difference in apoptosis induction and a difference in G2/M arrest maximum duration. Moreover, 5FU exposure has led to an increase in constitutive p53 protein expression, which may be associated with an increase in basal apoptosis cell fraction. Given the existing correlation between radiosensitivity and the percentage of basal apoptosis, the constitutive p53 protein expression may be related to intrinsic radiosensitivity in our cellular model.
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