Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (Apo2L/TRAIL) belongs to the TNF family known to transduce their death signals via cell membrane receptors. Because it has been shown that Apo2L/TRAIL induces apoptosis in tumor cells without or little toxicity to normal cells, this cytokine became of special interest for cancer research. Unfortunately, cancer cells are often resistant to Apo2L/TRAIL-induced apoptosis; however, this can be at least partially negotiated by parallel treatment with other substances, such as chemotherapeutic agents. Here, we report that cardiac glycosides, which have been used for the treatment of cardiac failure for many years, sensitize lung cancer cells but not normal human peripheral blood mononuclear cells to Apo2L/TRAIL-induced apoptosis. Sensitization to Apo2L/TRAIL mediated by cardiac glycosides was accompanied by up-regulation of death receptors 4 (DR4) and 5 (DR5) on both RNA and protein levels. The use of small interfering RNA revealed that up-regulation of death receptors is essential for the demonstrated augmentation of apoptosis. Blocking of up-regulation of DR4 and DR5 alone significantly reduced cell death after combined treatment with cardiac glycosides and Apo2L/TRAIL. Combined silencing of DR4 and DR5 abrogated the ability of cardiac glycosides and Apo2L/ TRAIL to induce apoptosis in an additive manner. To our knowledge, this is the first demonstration that glycosides upregulate DR4 and DR5, thereby reverting the resistance of lung cancer cells to Apo2/TRAIL-induced apoptosis. Our data suggest that the combination of Apo2L/TRAIL and cardiac glycosides may be a new interesting anticancer treatment strategy. (Cancer Res 2006; 66(11): 5867-74)

No abstract

Systemic lupus erythematosus is a chronic autoimmune disorder that predominantly affects women of childbearing age. Lupus-associated glomerulonephritis is a major cause of mortality in these patients. Current treatment protocols for systemic lupus erythematosus include cyclophosphamide, prednisolone, azathioprine, and mycophenolate mofetil. However, in mice none of these agents alone or in combination were shown to reverse established proteinuria. Using New Zealand Black × New Zealand White F1 mice, we report that administration of the topoisomerase I inhibitor irinotecan from week 13 completely prevented the onset of proteinuria and prolonged survival up to at least 90 wk without detectable side effects. Furthermore, application of irinotecan to mice with established lupus nephritis, as indicated by grade 3+ (≥300 mg/dl) and grade 4+ (≥2000 mg/dl) proteinuria and, according to a median age of 35 wk, resulted in remission rates of 75% and 55%, respectively. Survival was significantly prolonged with 73 wk (grade 3+ and 4+ combined) versus 40 wk for control animals. Although total IgG and anti-dsDNA Abs in the serum and mesangial IgG deposits in the kidneys were not reduced in irinotecan-treated mice, subendothelial immune deposits were considerably diminished, suggesting a prevention of glomerular basement membrane disruption. This effect was accompanied by increased rates of ssDNA breaks and inhibition of renal cell apoptosis being different to what is known about irinotecan in anticancer therapy. In conclusion, our data provide evidence that irinotecan might represent an entirely new strategy for the treatment of systemic lupus erythematosus.

Objective. Despite clear advances in the treatment of systemic lupus erythematosus (SLE), many patients still present with refractory lupus nephritis, requiring new treatment strategies for this disease. This study was undertaken to determine whether reduced doses of the topoisomerase I (topo I) inhibitor irinotecan, which is known as a chemotherapeutic agent, suppress SLE in (NZB ؋ NZW)F1 (NZB/NZW) mice, and to evaluate the potential mechanism by which irinotecan influences the course of SLE.Methods. NZB/NZW mice were treated with lowdose irinotecan beginning at either 24 weeks of age or established glomerulonephritis, defined as proteinuria of grade >3؉. Binding of anti-double-stranded DNA (anti-dsDNA) antibodies was measured by enzymelinked immunosorbent assay (ELISA), and DNA relaxation was visualized by gel electrophoresis.Results. Significantly reduced irinotecan doses improved lupus nephritis and prolonged survival in NZB/NZW mice. The lowest dose successfully used for the treatment of established murine lupus nephritis was >50 times lower than the dose usually used for chemotherapy in humans. As a mechanism, low-dose irinotecan reduced B cell activity. However, the levels of B cell activity in irinotecan-treated mice were similar to those in BALB/c mice of the same age, suggesting that irinotecan did not induce clear immunosuppression. In addition, incubation of dsDNA with topo I increased binding of murine and human anti-dsDNA antibodies, showing for the first time that relaxed DNA is more susceptible to anti-dsDNA antibody binding. This effect was reversed by addition of the topo I inhibitor camptothecin.Conclusion. Our findings indicate that topo I inhibition may be a novel and targeted therapy for SLE.

No abstract