The Biological Significance of PACAP and PACAP Receptors in Human Tumors: From Cell Lines to Cancers

Detection of bladder cancer using voided urine sample and by targeting genomic VPAC receptors

Introduction:

Cells exfoliated into urine from the bladder can help to diagnose the cancer. The objective of this study was to validate the hypothesis that bladder cancer could be detected noninvasively by a simple and reliable assay targeting genomic VPAC (combined vasoactive intestinal peptide and pituitary adenylate cyclase-activating peptide family of cell surface receptors) receptors expressed on the malignant bladder cancer cells shed in the voided urine.

Methods:

Patients ≥18 years of age with either imaging (ultrasonography/computed tomography [CT])-confirmed bladder tumors or those who have been previously treated for nonmuscle invasive bladder tumors and were visiting the department for check cystoscopy, formed the study group. Freshly voided urine sample was collected from these patients and sent for conventional cytology examination, 5-aminolevulinic acid (ALA) fluorescent urine cytology, and for positivity of VPAC receptors.

Results:

A total of 103 patients were prospectively included in the study. Of these, 65 patients (Group I) presented with image-diagnosed (ultrasonography and/or CT) bladder cancer. The remaining 38 patients (Group II) were previously diagnosed cases of nonmuscle invasive bladder cancer and presented for follow-up and check cystoscopy. The sensitivity for VPAC receptor positivity was 89.23% compared to conventional cytology (63.07%) and 5-ALA fluorescent urine cytology (87.69%). The specificity of VPAC receptor positivity was 100% compared to conventional cytology (100%) and 5-ALA-induced fluorescent cytology (90.47%).

Conclusions:

Our preliminary study shows encouraging results with VPAC receptor positivity studies, which has a high sensitivity when compared to the conventional cytology.

Small-molecule modulators of Hh and Wnt signaling pathways

Hedgehog (Hh) and Wnt signaling pathways play key roles in growth and patterning during embryonic development and in the postembryonic regulation of stem cell number in the epithelia. Numerous studies link aberrant modulation of these pathways to specific human diseases. This article focuses on general aspects of Hh and Wnt signal transduction and biologic molecules involved in the respective signaling cascades. Specifically, the authors summarize small-molecule modulators of both pathways that show promise as therapeutic modalities.

Pituitary Adenylate Cyclase-Activating Polypeptide Is a Potent Inhibitor of the Growth of Light Chain-Secreting Human Multiple Myeloma Cells

Multiple myeloma represents a malignant proliferation of plasma cells in the bone marrow, which often overproduces immunoglobulin light chains. We have shown previously that pituitary adenylate cyclase-activating polypeptide (PACAP) markedly suppresses the release of proinflammatory cytokines from light chain-stimulated human renal proximal tubule epithelial cells and prevents the resulting tubule cell injury. In this study, we have shown that PACAP suppresses the proliferation of human kappa and lambda light chain-secreting multiple myeloma-derived cells. The addition of PACAP suppressed light chain-producing myeloma cell-stimulated interleukin 6 (IL-6) secretion by the bone marrow stromal cells (BMSCs). A specific antagonist to either the human PACAP-specific receptor or the vasoactive intestinal peptide receptor attenuated the suppressive effect of PACAP on IL-6 production in the adhesion of human multiple myeloma cells to BMSCs. The secretion of IL-6 by BMSCs was completely inhibited by 10(-9) mol/L PACAP, which also attenuated the phosphorylation of both p42/44 and p38 mitogen-activated protein kinases (MAPK) as well as nuclear factor-kappaB (NF-kappaB) activation in response to the adhesion of multiple myeloma cells to BMSCs, whereas the inhibition of p42/44 MAPK signaling attenuated PACAP action. The signaling cascades involved in the inhibitory effect of PACAP on IL-6-mediated paracrine stimulation of light chain-secreting myeloma cell growth was mediated through the suppression of p38 MAPK as well as modulation of activation of transcription factor NF-kappaB. These findings suggest that PACAP may be a new antitumor agent that directly suppresses light chain-secreting myeloma cell growth and indirectly affects tumor cell growth by modifying the bone marrow milieu of the multiple myeloma.

Potential protective action of pituitary adenylate cyclase-activating polypeptide (PACAP38) on in vitro and in vivo models of myeloma kidney injury

The most common type of renal injury in multiple myeloma is chronic tubulointerstitial nephropathy associated with casts in tubule lumens, an entity referred to as “myeloma kidney” that often progresses to end-stage kidney diseases. Myeloma kidney is associated with a significant increase in all-cause mortality, yet no effective intervention, except a limited use of steroid, is available. Here, we report that pituitary adenylate cyclase-activating polypeptide with 38 residues (PACAP38) dramatically prevents injury of cultured renal proximal tubule cells caused by myeloma light chains through suppression of proinflammatory cytokines production, by inhibiting p38 MAPK and translocation of NFκB via both PAC1 and VPAC1 receptors. The suppressive effects of PACAP was as effective as dexamethasone in all of their cytokine assays and demonstrated both in vitro and in vivo. Furthermore, PACAP38 inhibits myeloma cell growth directly and may also indirectly by suppressing production of the growth factor, IL-6, from bone marrow stromal cells, that is stimulated by adhesion of myeloma cells. These findings render PACAP38 worth evaluation as a promising candidate for an effective and safe renoprotectant in myeloma kidney, and possibly other nephropathy, and also as a new antitumor agent in multiple myeloma.