thapsigargin and Kidney-Neoplasms

Interleukin-2 plays a crucial role in enhancing the antitumor immune response. Clinical trials, mainly in renal cell carcinoma and melanoma patients, have been carried out with encouraging results. Recent reports demonstrated that interleukin-2 therapy may depress the immune response either in vitro or in vivo. We decided to monitor, in nine renal cancer patients, the proliferative responses and the parallel variations in Ca2+ homeostasis of peripheral blood lymphocytes collected before, during and after the first cycle of a 3-day interleukin-2 systemic administration. The proliferative response to phytohemagglutinin or concanavalin A significantly dropped early during interleukin-2 infusion. Consistently, an impairment in mobilizing Ca2+, either from internal stores or via influx from outside, was observed. Results obtained with a mAb-alpha CD3 molecular complex strongly suggested that the TCR/CD3 signal transduction pathway was defective. In contrast, no major variations were observed in the general machinery controlling Ca2+ homeostasis nor in the total Ca(2+)-releasable pool. Patients' lymphocytes, cultured in vitro for 3 days in medium alone, showed an almost complete recovery in their ability to respond to mitogens. In conclusion, we show that interleukin-2 administration in cancer patients induces a reversible state of anergy in circulating lymphocytes, assessed both by the reduction in the proliferative response and the block of the mitogen-activated intracellular Ca2+ signalling.

Topics: Calcium; Carcinoma, Renal Cell; Cells, Cultured; Concanavalin A; Homeostasis; Humans; Immunotherapy; Interleukin-2; Ionomycin; Kidney Neoplasms; Lymphocyte Activation; Lymphocytes; Muromonab-CD3; Phytohemagglutinins; Recombinant Proteins; Second Messenger Systems; Signal Transduction; Stimulation, Chemical; Terpenes; Thapsigargin

Melatonin (N-acetyl-5-methoxytryptamine) has differentiated the effects on apoptosis in normal and cancer cells. The mechanisms that account for the opposite effects on these cells are not adequately understood. In this study, we investigated the combined effect of melatonin and thapsigargin (TG) on apoptosis of renal cancer cells. Cotreatment with melatonin (1mm) and TG (50nm) induced approximately 10-fold expression levels of CCAAT-enhancer-binding proteins homologous protein (CHOP) compared with that of TG (50nm) alone. Downregulation of CHOP expression using small interfering RNAs markedly attenuated melatonin plus TG-mediated apoptosis. In addition, cotreatment with TG- and melatonin-induced CHOP upregulation likely relates to melatonin's antioxidant capacity because we proved that this CHOP upregulation is melatonin receptor independent. Our results collectively demonstrate that the upregulation of CHOP contributes to the enhancing effect of melatonin plus TG on apoptosis in cancer cells.

Topics: Antioxidants; Apoptosis; Cell Line, Tumor; Enzyme Inhibitors; Gene Expression Regulation, Neoplastic; Humans; Kidney Neoplasms; Melatonin; Reactive Oxygen Species; Thapsigargin; Transcription Factor CHOP; Up-Regulation

The prostate-apoptosis-response-gene-4 (Par-4) protein has been shown to function as an effector of cell death in response to various apoptotic stimuli that trigger mitochondria and membrane receptor-mediated cell death pathways. We found that overexpressing Par-4 by stable transfection sensitizes Caki cells to induction of apoptosis by TRAIL and drugs that induce endoplasmic reticulum (ER) stress [thapsigargin (TG), tunicamycin (TU) and etoposide]. Ectopic expression of Par-4 is associated with decreased levels of XIAP protein in TG-treated cells, caused in part by XIAP protein instability and caspase activation. Levels of phospho-Akt are decreased in Caki/Par-4 cells to a significantly greater extent than in Caki/Vector cells by treatment with TG, and this is in turn associated with decreased levels of phospho-PDK1, the kinase upstream of Akt. In conclusion, we provide evidence that ectopic expression of Par-4 sensitizes Caki cells to TG and that XIAP protein instability and inactivation of Akt are important in cellular pathways affected by Par-4.

Topics: Adenocarcinoma, Clear Cell; Amino Acid Chloromethyl Ketones; Apoptosis; Apoptosis Regulatory Proteins; Caspases; Cell Division; Cell Line, Tumor; Endoplasmic Reticulum; Enzyme Activation; Etoposide; Gene Expression Regulation, Neoplastic; Humans; Kidney Neoplasms; Phosphorylation; Protein Processing, Post-Translational; Protein Serine-Threonine Kinases; Proto-Oncogene Proteins c-akt; Pyruvate Dehydrogenase Acetyl-Transferring Kinase; Recombinant Fusion Proteins; Thapsigargin; TNF-Related Apoptosis-Inducing Ligand; Transfection; X-Linked Inhibitor of Apoptosis Protein