Our previous work demonstrated that cytotoxic T lymphocyte (CTL)-mediated tumor immunosurveillance of the 15-12RM tumor could be suppressed by a CD1d-restricted lymphocyte, most likely a natural killer (NK) T cell, which produces interleukin (IL)-13. Here we present evidence for the effector elements in this suppressive pathway. T cell–reconstituted recombination activating gene (RAG)2 knockout (KO) and RAG2/IL-4 receptor α double KO mice showed that inhibition of immunosurveillance requires IL-13 responsiveness by a non–T non–B cell. Such nonlymphoid splenocytes from tumor-bearing mice produced more transforming growth factor (TGF)-β, a potent inhibitor of CTL, ex vivo than such cells from naive mice, and this TGF-β production was dependent on the presence in vivo of both IL-13 and CD1d-restricted T cells. Ex vivo TGF-β production was also abrogated by depleting either CD11b+ or Gr-1+ cells from the nonlymphoid cells of tumor-bearing mice. Further, blocking TGF-β or depleting Gr-1+ cells in vivo prevented the tumor recurrence, implying that TGF-β made by a CD11b+ Gr-1+ myeloid cell, in an IL-13 and CD1d-restricted T cell–dependent mechanism, is necessary for down-regulation of tumor immunosurveillance. Identification of this stepwise regulation of immunosurveillance, involving CD1-restricted T cells, IL-13, myeloid cells, and TGF-β, explains previous observations on myeloid suppressor cells or TGF-β and provides insights for targeted approaches for cancer immunotherapy, including synergistic blockade of TGF-β and IL-13.

The activity of fibroblast growth factor 2 (FGF-2) is stringently controlled. Inactive in undisturbed tissues, it is activated during injury and is critical for tissue repair. We find that this control can be imposed by the soluble syndecan-1 ectodomain, a heparan sulfate proteoglycan shed from cell surfaces into wound fluids. The ectodomain potently inhibits heparin-mediated FGF-2 mitogenicity because of the poorly sulfated domains in its heparin sulfate chains. Degradation of these regions by platelet heparanase produces heparin-like heparin sulfate fragments that markedly activate FGF-2 mitogenicity and are found in wound fluids. These results establish a novel physiological control for FGF-2 and suggest new ways to modulate FGF activity.

Chronic kidney disease–mineral bone disorder (CKD‐MBD) is defined by abnormalities in mineral and hormone metabolism, bone histomorphometric changes, and/or the presence of soft‐tissue calcification. Emerging evidence suggests that features of CKD‐MBD may occur early in disease progression and are associated with changes in osteocyte function. To identify early changes in bone, we utilized the jck mouse, a genetic model of polycystic kidney disease that exhibits progressive renal disease. At 6 weeks of age, jck mice have normal renal function and no evidence of bone disease but exhibit continual decline in renal function and death by 20 weeks of age, when approximately 40% to 60% of them have vascular calcification. Temporal changes in serum parameters were identified in jck relative to wild‐type mice from 6 through 18 weeks of age and were subsequently shown to largely mirror serum changes commonly associated with clinical CKD‐MBD. Bone histomorphometry revealed progressive changes associated with increased osteoclast activity and elevated bone formation relative to wild‐type mice. To capture the early molecular and cellular events in the progression of CKD‐MBD we examined cell‐specific pathways associated with bone remodeling at the protein and/or gene expression level. Importantly, a steady increase in the number of cells expressing phosphor‐Ser33/37‐β‐catenin was observed both in mouse and human bones. Overall repression of Wnt/β‐catenin signaling within osteocytes occurred in conjunction with increased expression of Wnt antagonists (SOST and sFRP4) and genes associated with osteoclast activity, including receptor activator of NF‐κB ligand (RANKL). The resulting increase in the RANKL/osteoprotegerin (OPG) ratio correlated with increased osteoclast activity. In late‐stage disease, an apparent repression of genes associated with osteoblast function was observed. These data confirm that jck mice develop progressive biochemical changes in CKD‐MBD and suggest that repression of the Wnt/β‐catenin pathway is involved in the pathogenesis of renal osteodystrophy. © 2012 American Society for Bone and Mineral Research.

Polycystic kidney diseases (PKDs) are primarily characterized by the growth of fluid-filled cysts in renal tubules leading to end-stage renal disease. Mutations in the PKD1 or PKD2 genes lead to autosomal dominant PKD (ADPKD), a slowly developing adult form. Autosomal recessive polycystic kidney disease results from mutations in the PKHD1 gene, affects newborn infants and progresses very rapidly. No effective treatment is currently available for PKD. A previously unrecognized site of subcellular localization was recently discovered for all proteins known to be disrupted in PKD: primary cilia. Because ciliary functions seem to be involved in cell cycle regulation, disruption of proteins associated with cilia or centrioles may directly affect the cell cycle and proliferation, resulting in cystic disease. We therefore reasoned that the dysregulated cell cycle may be the most proximal cause of cystogenesis, and that intervention targeted at this point could provide significant therapeutic benefit for PKD. Here we show that treatment with the cyclin-dependent kinase (CDK) inhibitor (R)-roscovitine does indeed yield effective arrest of cystic disease in jck and cpk mouse models of PKD. Continuous daily administration of the drug is not required to achieve efficacy; pulse treatment provides a robust, long-lasting effect, indicating potential clinical benefits for a lifelong therapy. Molecular studies of the mechanism of action reveal effective cell-cycle arrest, transcriptional inhibition and attenuation of apoptosis. We found that roscovitine is active against cysts originating from different parts of the nephron, a desirable feature for the treatment of ADPKD, in which cysts form in multiple nephron segments. Our results indicate that inhibition of CDK is a new and effective approach to the treatment of PKD.

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