Probes for INS

Abstract

Activated Wnt signaling is critical in the pathogenesis of renal fibrosis, a final common pathway for most forms of chronic kidney disease. Therapeutic intervention by inhibition of individual Wnts or downstream Wnt/β-catenin signaling has been proposed, but these approaches do not interrupt the functions of all Wnts nor block non-canonical Wnt signaling pathways. Alternatively, an orally bioavailable small molecule, Wnt-C59, blocks the catalytic activity of the Wnt-acyl transferase porcupine, and thereby prevents secretion of all Wnt isoforms. We found that inhibiting porcupine dramatically attenuates kidney fibrosis in the murine unilateral ureteral obstruction model. Wnt-C59 treatment similarly blunts collagen mRNA expression in the obstructed kidney. Consistent with its actions to broadly arrest Wnt signaling, porcupine inhibition reduces expression of Wnt target genes and bolsters nuclear exclusion of β-catenin in the kidney following ureteral obstruction. Importantly, prevention of Wnt secretion by Wnt-C59 blunts expression of inflammatory cytokines in the obstructed kidney that otherwise provoke a positive feedback loop of Wnt expression in collagen-producing fibroblasts and epithelial cells. Thus, therapeutic targeting of porcupine abrogates kidney fibrosis not only by overcoming the redundancy of individual Wnt isoforms but also by preventing upstream cytokine-induced Wnt generation. These findings reveal a novel therapeutic maneuver to protect the kidney from fibrosis by interrupting a pathogenic crosstalk loop between locally generated inflammatory cytokines and the Wnt/β-catenin signaling pathway.

Abstract

Objectives

The aim of the present study was to investigate the molecular basis for the use of immune checkpoint inhibitors to treat salivary gland carcinomas (SGC).

Materials and methods

We examined the clinical and prognostic significance of programed death ligands 1 and 2 (PD-L1 and -L2) expression using immunohistochemistry and in situ hybridization, as well as microsatellite instability (MSI) status using polymerase chain reaction, along with tumor-infiltrating lymphocytes (TILs) in 30 cases of SGC.

Results

The SGC cases studied included adenoid cystic carcinoma (AdCC, 36.7%), salivary duct carcinoma (SDC, 26.7%), mucoepidermoid carcinoma (MEC, 23.3%), and carcinoma ex pleomorphic adenoma (CxPA, 13.3%). Either PD-L1 or PD-L2 overexpression was observed in 36.7% patients. PD-L2 expression was associated with reduced disease-specific survival (DSS) and disease-free survival (DFS) (P = 0.0266 and P = 0.0209, respectively). Simultaneous PD-L1 and PD-L2 overexpression was detected in 13.3% of cases, and was correlated with reduced DSS (P = 0.0113). Among non-AdCCs, all cases that developed distant metastasis were positive for PD-L2 (P = 0.001). Cases showing low-TILs that were positive for either PD-L1 or L2 were associated with poor DFS. No MSI was detected in the SGC cases studied.

Conclusion

To our knowledge, this is the first comprehensive study examining PD-L1 and PD-L2 status, MSI status, and TILs in SGC. Our results indicate that the PD-1/PD-L1 or PD-L2 pathway, which is associated with poor clinical outcomes, may provide promising therapeutic targets against SGC in selected patients. Further experimental and clinical studies are encouraged.

How stem cells maintain their identity and potency as tissues change during growth is not well understood. In mammalian hair, it is unclear how hair follicle stem cells can enter an extended period of quiescence during the resting phase but retain stem cell potential and be subsequently activated for growth. Here, we use lineage tracing and gene expression mapping to show that the Wnt target gene Axin2 is constantly expressed throughout the hair cycle quiescent phase in outer bulge stem cells that produce their own Wnt signals. Ablating Wnt signaling in the bulge cells causes them to lose their stem cell potency to contribute to hair growth and undergo premature differentiation instead. Bulge cells express secreted Wnt inhibitors, including Dickkopf (Dkk) and secreted frizzled-related protein 1 (Sfrp1). However, the Dickkopf 3 (Dkk3) protein becomes localized to the Wnt-inactive inner bulge that contains differentiated cells. We find that Axin2 expression remains confined to the outer bulge, whereas Dkk3 continues to be localized to the inner bulge during the hair cycle growth phase. Our data suggest that autocrine Wnt signaling in the outer bulge maintains stem cell potency throughout hair cycle quiescence and growth, whereas paracrine Wnt inhibition of inner bulge cells reinforces differentiation.