Apoptosis is the most efficient death-pathway in tumor cells after topoisomerase II inhibition

To compare the efficiency of apoptosis and other modes of cell death in killing tumor cells after the induction of DNA damage by topoisomerase inhibitors like etoposide. This study was carried out in the Tumor Biology Department, National Cancer Institute, Cairo University, Cairo, Egypt, from September 2005 to August 2007. The breast cancer MCF7, the cervix carcinoma, human cervical adenocarcinoma [Hela], and the brain tumor U251 cell lines were exposed to etoposide. Apoptosis was detected using the flow cytometry and the DNA ladder formation methods. Cell viability was determined by a colorimetric assay, and the residual DNA double-strand breaks [dsb] were measured by gel electrophoresis. The Hela cells were the most, the MCF7's were moderately, whereas the U251's were the least sensitive to etoposide. Apoptosis was detected only in Hela cells whereas the other 2 cell lines showed a very low level of apoptosis [only 3% increase above the control cells]. At equitoxic drug concentrations [namely IC50], the Hela cells showed the lowest amount of non-repaired DNA dsb, and the MCF7's showed the highest amount, whereas the U251 cells showed a moderate amount. These results indicate that although other modes of cell death exist, apoptosis is the most efficient and requires lower drug concentrations and fewer numbers of non-repaired dsb to give the same killing effect. Clinically, this means that tumors that can execute apoptosis may require lower doses of topoisomerase inhibitors than those that lost the ability to exercise apoptosis

Loss of heterozygosity at BRCA1, TP53, nm-23 and other loci on chromosome 17q in human breast carcinoma

In Egypt, breast cancer ranks number one among the female malignancies. Activation of oncogenes and inactivation of tumor suppressor genes are thought to play an important role in the development and progression of breast cancer. The present study is a trial to investigate the role of chromosome 17 in sporadic invasive ductal carcinoma of the breast through detection of LOH for 6 highly polymorphic microsatellite loci, two of which are located at BRCA1 gene [D17S855 and D17S856], one at TP53 gene, one at nm 23 gene and finally two at 17q12-12.3 [D17S183 and D17S250]. Tissue samples and their corresponding safety margin normal tissues were collected from 25 patients with invasive ductal carcinoma of the breast of grades 2 and 3. LOH was detected for the 6 highly polymorphic microsatellite markers mentioned previously using PCR assay. The percentage of overall LOH recorded was 68% of the cases examined. The highest LOH was recorded in D17S855 and D17S856 [43% and 32% respectively], both markers are located at BRCA1 gene, followed by 32% LOH in nm-23 gene. D17S183 and D17S250, which are localized telomeric and centromeric to BRCA1 gene, showed 24% and 28% LOH, respectively. The lowest percentage of LOH was observed in the TP53 gene [14%]. No significant correlation was found between each of the six markers used and lymph node status, grade, or menopause status. LOH at the nm-32 marker exhibited a significant association with lymph node involvement. It can be concluded from the present study that BRCA1 gene may be involved in carcinogenesis of some sporadic breast cancer cases. Deletion in nm-23 gene is associated with the advanced stage of the disease. Finally, another gene located at 17q 12- 12.3 region may be involved in some sporadic breast cancer cases