The effects of CD40 ligation in an epithelial context are complex, with the level of CD40 engagement influencing the physiological outcome. Low levels of CD40 ligation promote cell survival/proliferation, whereas high levels induce growth arrest/apoptosis. The precise form of the CD40 stimulus affects these responses with the most profound effects in carcinoma cells being induced by membrane-bound rather than recombinant soluble CD40L. However, the signaling pathways underlying these differential responses are yet to be fully characterized. We have investigated the mechanistic differences resulting from CD40 engagement by soluble and membrane-bound ligands using a novel adenovirus-delivered CD40L mutated to resist cleavage from the cell membrane in the CD40-positive EJ bladder carcinoma cell line. We have shown that membrane-bound CD40L induces apoptosis by influencing the balance between apoptotic and survival signals. Thus, membrane-bound CD40L stabilizes TNFR-associated factor 3 to induce JNK-dependent apoptosis via release of mitochondrial cytochrome c, caspase 9, and effector caspases 3/7. Further, we have shown that this process is dependent on activation of caspase 8. However, there is also a requirement for suppression of TNFR-associated factor 6-mediated PI3K/Akt-dependent survival signals for apoptosis to occur. These data provide mechanistic insights into the consequences of CD40 activation in carcinoma cells and how these might be exploited in the clinical development of CD40-targeted anticancer therapies.

Membrane-bound CD40L (mCD40L) but not soluble CD40L (sCD40L) has been implicated in direct cell death induction and apoptosis in CD40-expressing carcinomas. In this study, we show that mCD40L but not sCD40L induces NORE1A/Rassf5 expression in an NFκB-dependant mechanism. NORE1A expression appeared to contribute to mCD40L-induced cell death and enhance cell transition from G1 to S phase of the cell cycle in a p21-dependent mechanism. The upregulation of p21 protein was attributed to NORE1A expression, since NORE1A inhibition resulted in p21 downregulation. p21 upregulation was concomitant with lower p53 expression in the cytoplasmic fraction with no detectable increase at the nuclear p53 level. Moreover, mCD40L-induced cell death mediated by NORE1A expression appeared to be independent of mCD40L-induced cell death mediated by sustained JNK activation since NORE1A inhibition did not affect JNK phosphorylation and vice versa. The presented data allow better understanding of the mechanism by which mCD40L induces cell death which could be exploited in the clinical development of CD40-targeted anti-cancer therapies.

Despite advances in management, bladder cancer remains a major cause of cancer related complications. Characterisation of gene expression patterns in bladder cancer allows the identification of pathways involved in its pathogenesis, and may stimulate the development of novel therapies targeting these pathways. Between 2004 and 2005, cystoscopic bladder biopsies were obtained from 19 patients and 11 controls. These were subjected to whole transcript-based microarray analysis. Unsupervised hierarchical clustering was used to identify samples with similar expression profiles. Hypergeometric analysis was used to identify canonical pathways and curated networks having statistically significant enrichment of differentially expressed genes. Osteopontin (OPN) expression was validated by immunohistochemistry. Hierarchical clustering defined signatures, which differentiated between cancer and healthy tissue, muscle-invasive or non-muscle invasive cancer and healthy tissue, grade 1 and grade 3. Pathways associated with cell cycle and proliferation were markedly upregulated in muscle-invasive and grade 3 cancers. Genes associated with the classical complement pathway were downregulated in non-muscle invasive cancer. Osteopontin was markedly overexpressed in invasive cancer compared to healthy tissue. The present study contributes to a growing body of work on gene expression signatures in bladder cancer. The data support an important role for osteopontin in bladder cancer, and identify several pathways worthy of further investigation.

In carcinomas, the nature of CD40 ligand shapes the outcome of CD40 ligation. To date, the consequences of membrane-bound CD40L (mCD40L) on its immune-stimulatory function are unknown. Here, we examined the impact of mCD40L versus soluble CD40L (sCD40L) on T24 bladder carcinoma gene expression profiling. Of 410 differentially expressed genes, 286 were upregulated and 124 downregulated by mCD40L versus sCD40L. Gene ontology enrichment analysis revealed immunestimulatory function as the most significant enriched biological process affected by upregulated transcripts, while those downregulated were critical for cell growth and division. Furthermore, immature dendritic cells (iDC) responded to mCD40L with enhanced maturation and activation over sCD40L evidenced by higher expression levels of CD83, CD86, HLA-DR and CD54, increased secretion of IL12 and IL10 and higher tumour-antigen (TA) uptake capacity. Furthermore, autologus CD3+ T cells responded to TA-loaded mCD40L-activated DC with increased proliferation and cytotoxic response (CD107a and IFN-γ-producing CD3+ CD8+ T cells) to the tumour-loaded autologous PBMCs compared to sCD40L. Thus, these data indicate that mCD40L enhances the immunostimulatory capacity over sCD40L. Furthermore, the ability of mCD40L to also directly induce cell death in CD40-expressing carcinomas, subsequently releasing tumour-specific antigens into the tumour microenvironment highlights the potential for mCD40L as a multi-faceted anti-cancer immunotherapeutic. The fundamental role of the CD40 receptor, a member of the TNFR superfamily together with its ligand (CD40L/ CD154) in coordinating immune responses has been widely recognised as an early event in initiating immune responses 1. CD40, a 40-kD type 1 transmembrane protein is expressed in normal B cells, malignant hematopoietic cells and antigen presenting cells (APC), including dendritic cells (DC) and monocytes 2,3. Furthermore, activated CD4 + and CD8+ T cells also express CD40 receptor, where in absence of CD40 expression, CD8+ T cells were unable to differentiate into memory cells or receive CD4 help 4. In addition to hematopoietic cells, several carcinomas express CD40 receptor, including those of the ovary, liver, and bladder, despite receptor expression being undetectable in normal epithelium derived from the same tissue 5. In contrast to the wide-spectrum of CD40 expression, the expression of CD40L, a 32-kD protein is restricted mainly to activated CD4+ T cells and, to a lesser extent, activated B cells and platelets 6. In hematopoietic cells the importance of CD40-CD40L interaction is well-recognized particularly in shaping adaptive immune responses, where the outcome of CD40 ligation is cell-type dependant, with CD40 activation in DC leading to differentiation into IL12-and IFNγ-secreting cells and upregulation of co-stimulatory and adhesion molecules; while B cells respond by Ig-class switching 7. Furthermore, the strength of CD40 ligation by CD40L can influence the signalling outcome, with strong CD40 ligation enhancing anti...