The NRF2-mediated oxidative stress response pathway is associated with tumor cell resistance to arsenic trioxide across the NCI-60 panel

<p>Abstract</p> <p>Background</p> <p>Drinking water contaminated with inorganic arsenic is associated with increased risk for different types of cancer. Paradoxically, arsenic trioxide can also be used to induce remission in patients with acute promyelocytic leukemia (APL) with a success rate of approximately 80%. A comprehensive study examining the mechanisms and potential signaling pathways contributing to the anti-tumor properties of arsenic trioxide has not been carried out.</p> <p>Methods</p> <p>Here we applied a systems biology approach to identify gene biomarkers that underlie tumor cell responses to arsenic-induced cytotoxicity. The baseline gene expression levels of 14,500 well characterized human genes were associated with the GI₅₀ data of the NCI-60 tumor cell line panel from the developmental therapeutics program (DTP) database. Selected biomarkers were tested <it>in vitro</it> for the ability to influence tumor susceptibility to arsenic trioxide.</p> <p>Results</p> <p>A significant association was found between the baseline expression levels of 209 human genes and the sensitivity of the tumor cell line panel upon exposure to arsenic trioxide. These genes were overlayed onto protein-protein network maps to identify transcriptional networks that modulate tumor cell responses to arsenic trioxide. The analysis revealed a significant enrichment for the oxidative stress response pathway mediated by nuclear factor erythroid 2-related factor 2 (NRF2) with high expression in arsenic resistant tumor cell lines. The role of the NRF2 pathway in protecting cells against arsenic-induced cell killing was validated in tumor cells using shRNA-mediated knock-down.</p> <p>Conclusions</p> <p>In this study, we show that the expression level of genes in the NRF2 pathway serve as potential gene biomarkers of tumor cell responses to arsenic trioxide. Importantly, we demonstrate that tumor cells that are deficient for NRF2 display increased sensitivity to arsenic trioxide. The results of our study will be useful in understanding the mechanism of arsenic-induced cytotoxicity in cells, as well as the increased applicability of arsenic trioxide as a chemotherapeutic agent in cancer treatment.</p

Modification of the Boyden chamber to improve uniformity of cell invasion of matrigel-coated membranes

The ability of cells to invade basement membranes is critical to a number of important biological processes, such as cell metastasis, embryo implantation and early development, and inflammation. Several in vitro invasion assays have been developed so that the invasiveness of cells can be measured.These assays are also used to monitor the altered cell response to stimuli or inhibitors, such as in the evaluation of potential inhibitors of metastasis and other chemotherapeutic drugs. One of the most rapid assays is performed in a modified blind-well Boyden chamber(1,4) containing a filter coated with Matrigel, which is a commercially available reconstituted basement ex-tract from the Engelbreth-Holm-Swarmmurine sarcoma (Becton Dickinson,Franklin Lakes, NJ, USA). The Matrigel acts as a barrier on the surface of a porous filter, separating cells in one compartment from a chemo attractant in another compartment..