Association between the unfolded protein response, induced by 2-deoxyglucose, and hypersensitivity to cisplatin: a mechanistic study employing molecular genomics.

BACKGROUND: The specific signaling that occurs between the endoplasmic reticulum (ER) and the nucleus in response to ER stress is known as the unfolded protein response (UPR). Specific induction of GRP78 (glucose-regulated protein of Mr 78 kDa) is an integral component of ER stress and the UPR. We first discovered that the up-regulation of GRP78 is associated with augmented sensitivity/apoptosis of cancer cells to clinically used alkylating/platinating agents.
OBJECTIVES: To decipher molecular mechanisms that associate induction of the UPR/GRP78 with augmented sensitivity/apoptosis to cisplatin.
MATERIALS AND METHODS: A549 cells were exposed to 2-deoxyglucose (2dG) to induce the UPR/GRP78, followed by cisplatin treatment. We used human cDNA microarray containing 42,000 ESTs as well as pathway-specific macroarrays for apoptosis, cell cycle, and MAP kinase signaling pathways containing 100-280 genes and subsequently examined the pertinent transcript levels. The results obtained from these studies were confirmed by examining relevant protein levels and the enzymatic activity.
RESULTS: We demonstrate that the induction of UPR/GRP78 alone causes a decrease in the transcript levels of DNA repair genes and DNA damage check point genes, and an increase in the transcript levels of apoptotic genes. Furthermore, we show that cisplatin treatment after the induction of UPR/GRP78 is facilitating the mitochondria-mediated apoptotic cascades through the initial activation of caspase-2 and down-regulation of genes involved in DNA repair.
CONCLUSIONS: Our study will shed new insight as to the increased understanding of the mechanisms of the UPR/GRP78 modulation of molecular and cellular responses to cisplatin that will allow strategies for transferring bench side results to the bed.