Recent work in several model organisms has revealed that apoptotic cells are able to stimulate neighboring surviving cells to undergo additional proliferation, a phenomenon termed apoptosis-induced proliferation. This process depends critically on apoptotic caspases such as Dronc, the Caspase-9 ortholog in Drosophila, and may have important implications for tumorigenesis. While it is known that Dronc can induce the activity of Jun N-terminal kinase (JNK) for apoptosis-induced proliferation, the mechanistic details of this activation are largely unknown. It is also controversial if JNK activity occurs in dying or in surviving cells. Signaling molecules of the Wnt and BMP families have been implicated in apoptosis-induced proliferation, but it is unclear if they are the only ones. To address these questions, we have developed an efficient assay for screening and identification of genes that regulate or mediate apoptosis-induced proliferation. We have identified a subset of genes acting upstream of JNK activity including Rho1. We also demonstrate that JNK activation occurs both in apoptotic cells as well as in neighboring surviving cells. In a genetic screen, we identified signaling by the EGFR pathway as important for apoptosis-induced proliferation acting downstream of JNK signaling. These data underscore the importance of genetic screening and promise an improved understanding of the mechanisms of apoptosis-induced proliferation.

Rhodopsin recycling via the retromer, rather than degradation through lysosomes, can alleviate light-induced photoreceptor degeneration in Drosophila.

Classic signaling by the proinflammatory cytokine interleukin 6 (IL-6) involves its binding to target cells that express the membrane-bound IL-6 receptor a. However, an alternate signaling pathway exists in which soluble IL-6 receptor (sIL-6Ra) can bind IL-6 and activate target cells that lack mIL-6Ra, such as endothelial cells. This alternate pathway, also termed trans-signaling, serves as the major IL-6 signaling pathway in various pathologic proinflammatory conditions including cancer. Here we report that sIL-6Ra is elevated in malignant ascites from ovarian cancer patients, where it is associated with poor prognosis. IL-6 trans-signaling on endothelial cells prevented chemotherapy-induced apoptosis, induced endothelial hyperpermeability, and increased transendothelial migration of ovarian cancer cells. Selective blockade of the MAPK pathway with ERK inhibitor PD98059 reduced IL-6/sIL-6Ra-mediated endothelial hyperpermeability. ERK activation by the IL-6/sIL-6Ra complex increased endothelial integrity via Src kinase activation and Y685 phosphorylation of VE-cadherin. Selective targeting of IL-6 trans-signaling in vivo reduced ascites formation and enhanced the taxane sensitivity of intraperitoneal human ovarian tumor xenografts in mice. Collectively, our results show that increased levels of sIL-6Ra found in ovarian cancer ascites drive IL-6 trans-signaling on endothelial cells, thereby contributing to cancer progression. Selective blockade of IL-6 trans-signaling may offer a promising therapeutic strategy to improve the management of patients with advanced ovarian cancer. Cancer Res; 71(2); 424-34. Ó2010 AACR.