More than 50% of patients with aggressive B lymphomas and the majority of patients with low grade lymphomas are not cured by current therapeutic strategies. The lymphomas express the B cell antigen CD20 on the cell surface and this antigen serves as target for antibody-directed therapies. Clinical studies with encouraging results have been underway with the use of a chimeric anti-CD20 antibody (IDEC-C2B8), consisting of human IgG1-6 constant regions and variable regions from the murine monoclonal anti-CD20 antibody IDEC-2B8. This study investigated the potential anti-tumor therapeutic value of combination treatment with anti-C2B8 and cytotoxic drugs. The in vitro study examined the sensitizing effect of C2B8 antibody on the DHL-4 B lymphoma line to various cytotoxic agents. Cytotoxicity was determined by the MTT assay. Surface and cytoplasmic proteins were determined by flow cytometry. Pretreatment of DHL-4 with C2B8 resulted in inhibition of cell proliferation and cell death and a fraction of the cells underwent apoptosis. While the DHL-4 tumor cells were relatively resistant to several cytotoxic drugs, pretreatment with C2B8 rendered the cells sensitive to TNF-alpha, ricin, diphtheria toxin (DTX), adriamycin and cisplatin but not to VP-16. Chemosensitization of DHL-4 tumor cells was not due to downmodulation of either the MDR-1 or bcl-2 gene products. However, treatment of DHL-4 with C2B8 inhibited TNF-alpha secretion. These findings demonstrate that C2B8 antibody potentiates the sensitivity of DHL-4 tumor cells to several cytotoxic agents. Further, the findings suggest that combination treatments with C2B8 antibody and drugs may be of clinical benefit in the treatment of patients with resistant aggressive B lymphomas.

The final size and function of the adult central nervous system (CNS) are determined by neuronal lineages generated by neural stem cells (NSCs) in the developing brain. In Drosophila, NSCs called neuroblasts (NBs) reside within a specialised microenvironment called the glial niche. Here, we explore non-autonomous glial regulation of NB proliferation. We show that lipid droplets (LDs) which reside within the glial niche are closely associated with the signalling molecule Hedgehog (Hh). Under physiological conditions, cortex glial Hh is autonomously required to sustain niche chamber formation. Upon FGF-mediated cortex glial overgrowth, glial Hh non-autonomously activates Hh signalling in the NBs, which in turn disrupts NB cell cycle progression and its ability to produce neurons. Glial Hh's ability to signal to NB is further modulated by lipid storage regulator lipid storage droplet-2 (Lsd-2) and de novo lipogenesis gene fatty acid synthase 1 (Fasn1). Together, our data suggest that glial-derived Hh modified by lipid metabolism mechanisms can affect the neighbouring NB's ability to proliferate and produce neurons.

The final size of the adult central nervous system (CNS) is determined by the size of neuronal lineages generated by neural stem cells (NSCs) during development. In Drosophila, NSCs called neuroblasts (NBs) reside within a specialised microenvironment called the glial niche. Here, we explore non-cell autonomous regulation of NB behaviour by glia during normal development, and upon glial overgrowth. We show that lipid droplets that reside within the glial niche are closely associated with the signalling molecule Hedgehog (Hh). Under physiological conditions, Hh is present at low levels in the glial niche to ensure NBs faithfully produce the correct number and types of progeny that populate the adult nervous system. Upon Fibroblast Growth Factor (FGF) activation in glia, an accumulation of lipid droplets and Hh ligand non-cell autonomously triggers adjacent NBs to reduce their cell cycle speed, increase the developmental period in which they proliferate and disrupt their asymmetric division. Downstream of FGF signalling in the glia, we found that lipid metabolism affects both Hh subcellular localisation, as well as Hh post-translational modification, to modulate its activity, and in turn, its ability to activate Hh-signalling in the adjacent NBs. Together, our data suggest that wildtype and dysfunctional glial niche non-autonomously regulate neural lineage size via modulation of lipid metabolism and Hedgehog signalling. Statistical analysisP-values are calculated by two-tailed, unpaired Student's t-test, with equal sample variance; The Welch's correction was applied in case of unequal variances. Mann-Whitney test was used when data deviated from a normal distribution. For all histograms, error bars represent SEM.