Cell migration plays an important role in tumor cell invasion and metastasis. Previously, we reported that caspase-8 contributes to cell migration and adhesion, a novel nonapoptotic function of an established apoptotic factor. Herein, we report that pro-caspase-8 is capable of restoring cell migration/ adhesion to caspase-8-null cells, establishing the first biological function of a pro-caspase. The catalytic activity of caspase-8 was not required for cell motility. Stimulation of motility with epidermal growth factor induced the phosphorylation of caspase-8 on tyrosine-380 and the interaction of caspase-8 with the p85A subunit of phosphatidylinositol 3-kinase. Tyrosine-380 was required for the restoration of cell motility and cell adhesion in caspase-8-null cells, demonstrating the importance of the caspase-8-p85 interaction for these nonapoptotic functions. These results suggest that caspase-8 phosphorylation converts it from a proapoptotic factor to a cell motility factor that, through tyrosine-380, interacts with p85, an established cell migration component. [Cancer Res 2007;67(24):11505-9]
Two established cancer cell lines, MCF-7 and Ishikawa, were both obtained directly from a cell repository and through another laboratory. The karyotypes from the two MCF-7 cell lines had up to 83 chromosomes and similarities for chromosomal gain and structural abnormalities. The two Ishikawa cell lines had up to 60 chromosomes with only a missing X as the common chromosome abnormality. CGH studies were performed by co-hybridizing the two Ishikawa or MCF-7 cell lines to normal metaphases. The differences seen between the two MCF-7 cell cultures reflect changes due to passage number and culture conditions. For Ishikawa, DNA polymorphic data and mutation studies suggest that the two cell lines are not derived from the same established tumor cell line. Our study shows the utilization of CGH in comparing cell lines originating from the same specimen. Our study also demonstrates the necessity for periodically evaluating cell lines to confirm their origin.
Tumor suppressor gene BRCA1 is frequently mutated in familial breast and ovarian cancer. BRCA1 plays pivotal roles in maintaining genomic stability by interacting with numerous proteins in cell cycle control and DNA repair. Irofulven (6-hydroxymethylacylfulvene, HMAF, MGI 114, NSC 683863) is one of a new class of anticancer agents that are analogs of mushroomderived illudin toxins. Preclinical studies and clinical trials have demonstrated that irofulven is effective against several tumor cell types. The exact nature of irofulven-induced DNA damage is not completely understood. We demonstrated previously that irofulven activates ATM and its targets, NBS1, SMC1, CHK2, and p53. In this study, we hypothesize that irofulven induces DNA double-strand breaks and that BRCA1 may affect chemosensitivity by controlling cell cycle checkpoints, DNA repair, and genomic stability in response to irofulven treatment. We observed that irofulven induces the formation of chromosome breaks and radials and the activation and foci formation of ␥-H2AX, BRCA1, and RAD51. We also provided evidence that irofulven induces the generation of DNA double-strand breaks. By using BRCA1-deficient or -proficient cells, we demonstrated that in response to irofulven, BRCA1 contributes to the control of S and G 2 /M cell cycle arrest and is critical for repairing DNA double-strand breaks and for RAD51-dependent homologous recombination. Furthermore, we found that BRCA1 deficiency results in increased chromosome damage and chemosensitivity after irofulven treatment.
Translocations and unique chromosome break points in melanoma will aid in the identification of the genes that are important in the neoplastic process. We have previously shown a unique translocation in malignant melanoma cells der(12)t(12;20). The transcription factor E2F1 maps to 20q11. Increased expression of E2F has been associated with the autonomous growth of melanoma cells, however, the molecular basis has not yet been elucidated. To this end, we investigated E2F1 gene copy number and structure in human melanoma cell lines and metastatic melanoma cases. Fluorescent in situ hybridization (FISH) analysis using a specific E2F1 probe indicated increased E2F1 gene copies in melanoma cell lines compared to normal melanocytes. We also observed increased copies of the E2F1 gene in lymph node metastases of melanoma. In addition, Western blot analysis demonstrated increased E2F1 protein levels in 8 out of 9 melanoma cell lines relative to normal melanocytes. Inhibition of E2F1 expression with RNAi also reduced melanoma cell growth. Our results suggest that the release of E2F activity by elevated E2F1 gene copy numbers may play a functional role in melanoma growth.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.