Systemic anticancer chemotherapy is immunosuppressive and mostly induces nonimmunogenic tumor cell death. Here, we show that even in the absence of any adjuvant, tumor cells dying in response to anthracyclins can elicit an effective antitumor immune response that suppresses the growth of inoculated tumors or leads to the regression of established neoplasia. Although both antracyclins and mitomycin C induced apoptosis with caspase activation, only anthracyclin-induced immunogenic cell death was immunogenic. Caspase inhibition by Z-VAD-fmk or transfection with the baculovirus inhibitor p35 did not inhibit doxorubicin (DX)-induced cell death, yet suppressed the immunogenicity of dying tumor cells in several rodent models of neoplasia. Depletion of dendritic cells (DCs) or CD8+T cells abolished the immune response against DX-treated apoptotic tumor cells in vivo. Caspase inhibition suppressed the capacity of DX-killed cells to be phagocytosed by DCs, yet had no effect on their capacity to elicit DC maturation. Freshly excised tumors became immunogenic upon DX treatment in vitro, and intratumoral inoculation of DX could trigger the regression of established tumors in immunocompetent mice. These results delineate a procedure for the generation of cancer vaccines and the stimulation of anti-neoplastic immune responses in vivo.

Coordination of ciliary beating is essential to ensure mucus clearance in the airway tract. The orientation and synchronization of ciliary motion responds in part to the organization of the underlying cytoskeletal networks. Using electron tomography on mouse trachea, we show that basal bodies are collectively hooked at the cortex by a regular microtubule array composed of 4-5 microtubules. Removal of Galectin-3, one of basal body components, provokes misrecruitment of γ-tubulin, disorganization of this microtubule framework emanating from the basal foot cap, together with loss of basal body alignment and cilium orientation, defects in cilium organization and reduced fluid flow in the tracheal lumen. We conclude that Galectin-3 plays a crucial role in the maintenance of the microtubule organizing center of the cilium and the “pillar” microtubules, and that this network is instrumental for the coordinated orientation and stabilization of motile cilia.

The capsid of hepatitis C virus (HCV) particles is considered to be composed of the mature form (p21) of core protein. Maturation to p21 involves cleavage of the transmembrane domain of the precursor form (p23) of core protein by signal peptide peptidase (SPP), a cellular protease embedded in the endoplasmic reticulum membrane. Here we have addressed whether SPP-catalyzed maturation to p21 is a prerequisite for HCV particle morphogenesis in the endoplasmic reticulum. HCV structural proteins were expressed by using recombinant Semliki Forest virus replicon in mammalian cells or recombinant baculovirus in insect cells, because these systems have been shown to allow the visualization of HCV budding events and the isolation of HCV-like particles, respectively. Inhibition of SPP-catalyzed cleavage of core protein by either an SPP inhibitor or HCV core mutations not only did not prevent but instead tended to facilitate the observation of viral buds and the recovery of virus-like particles. Remarkably, although maturation to p21 was only partially inhibited by mutations in insect cells, p23 was the only form of core protein found in HCV-like particles. Finally, newly developed assays demonstrated that p23 capsids are more stable than p21 capsids. These results show that SPP-catalyzed cleavage of core protein is dispensable for HCV budding but decreases the stability of the viral capsid. We propose a model in which p23 is the form of HCV core protein committed to virus assembly, and cleavage by SPP occurs during and/or after virus budding to predispose the capsid to subsequent disassembly in a new cell. Signal peptide peptidase (SPP)5 belongs to a novel family of polytopic membrane-associated aspartyl proteases that catalyze cleavage of peptide bonds within the hydrophobic environment of a lipid bilayer (for review see Ref. 1). SPP is highly conserved in higher eucaryotes from plants to humans, including insects (2, 3). This membrane protein with nine proposed transmembrane domains exerts its action in the endoplasmic reticulum (ER), where it resides by virtue of a classical ER retrieval signal (3-5). The SPP substrates identified so far have in common a type II (N terminus facing the cytosol and C terminus facing the lumen) orientation but do not unequivocally point to a common role for SPP activity. In humans, SPP carries out the intramembrane cleavage of signal peptides of polymorphic major histocompatibility complex class I molecules after they have been cleaved off by signal peptidase; the short N-terminal signal peptide remnants then serve as epitopes presented at the cell surface by nonpolymorphic human lymphocyte antigen-E molecules for immune surveillance (6). Thus, SPP activity may promote the liberation from the ER lipid bilayer of some bioactive signal peptide fragments. Another role of SPP activity may be to protect cells from the toxicity of some signal peptides, e.g. the signal peptide of eosinophil cationic protein (7). Finally, the substrate spectrum of SPP may not be restricted to signal peptides but e...