Metastasis-associated fibroblasts in peritoneal surface malignancies.

Over decades, peritoneal surface malignancies (PSMs) have been associated with limited treatment options and poor prognosis. However, advancements in perioperative systemic chemotherapy, cytoreductive surgery (CRS), and hyperthermic intraperitoneal chemotherapy (HIPEC) have significantly improved clinical outcomes. PSMs predominantly result from the spread of intra-abdominal neoplasia, which then form secondary peritoneal metastases. Colorectal, ovarian, and gastric cancers are the most common contributors. Despite diverse primary origins, the uniqueness of the peritoneum microenvironment shapes the common features of PSMs. Peritoneal metastization involves complex interactions between tumour cells and the peritoneal microenvironment. Fibroblasts play a crucial role, contributing to tumour development, progression, and therapy resistance. Peritoneal metastasis-associated fibroblasts (MAFs) in PSMs exhibit high heterogeneity. Single-cell RNA sequencing technology has revealed that immune-regulatory cancer-associated fibroblasts (iCAFs) seem to be the most prevalent subtype in PSMs. In addition, other major subtypes as myofibroblastic CAFs (myCAFs) and matrix CAFs (mCAFs) were frequently observed across PSMs studies. Peritoneal MAFs are suggested to originate from mesothelial cells, submesothelial fibroblasts, pericytes, endothelial cells, and omental-resident cells. This plasticity and heterogeneity of CAFs contribute to the complex microenvironment in PSMs, impacting treatment responses. Understanding these interactions is crucial for developing targeted and local therapies to improve PSMs patient outcomes.

Nephronophthisis-associated FBW7 mediates cyst-dependent decline of renal function in ADPKD.

Nephronophthisis (NPHP) and autosomal dominant Polycystic Kidney Disease (ADPKD) are two genetically distinct forms of Polycystic Kidney Disease (PKD), yet both diseases present with kidney cysts and a gradual decline in renal function. Prevailing dogma in PKD is that changes in kidney architecture account for the decline in kidney function, but the molecular/cellular basis of such coupling is unknown. To address this question, we induced a form of proteome reprogramming by deleting Fbxw7 encoding FBW7, the recognition receptor of the SCF FBW7 E3 ubiquitin ligase in different segments of the kidney tubular system. Deletion of Fbxw7 in the medulla led to a juvenile-adult NPHP-like phenotype, where the decline in renal function was due to SOX9-mediated interstitial fibrosis rather than cystogenesis. In contrast, the decline of renal function in ADPKD is coupled to cystic expansion via the abnormal accumulation of FBW7 in the proximal tubules and other cell types in the renal cortex. We propose that FBW7 functions at the apex of a protein network that determines renal function in ADPKD by sensing architectural changes induced by cystic expansion.

Hepatectomy-induced apoptotic extracellular vesicles stimulate neutrophils to secrete regenerative growth factors.

BACKGROUND & AIMS: Surgical resection of the cancerous tissue represents one of the few curative treatment options for neoplastic liver disease. Such partial hepatectomy (PHx) induces hepatocyte hyperplasia, which restores liver function. PHx is associated with bacterial translocation, leading to an immediate immune response involving neutrophils and macrophages, which are indispensable for the priming phase of liver regeneration. Additionally, PHx induces longer-lasting intrahepatic apoptosis. Herein, we investigated the effect of apoptotic extracellular vesicles (aEVs) on neutrophil function and their role in this later phase of liver regeneration. METHODS: A total of 124 patients undergoing PHx were included in this study. Blood levels of the apoptosis marker caspase-cleaved cytokeratin-18 (M30) and circulating aEVs were analyzed preoperatively and on the first and fifth postoperative days. Additionally, the in vitro effects of aEVs on the secretome, phenotype and functions of neutrophils were investigated. RESULTS: Circulating aEVs increased at the first postoperative day and were associated with higher concentrations of M30, which was only observed in patients with complete liver recovery. Efferocytosis of aEVs by neutrophils induced an activated phenotype (CD11bhighCD16highCD66bhighCD62Llow); however, classical inflammatory responses such as NETosis, respiratory burst, degranulation, or secretion of pro-inflammatory cytokines were not observed. Instead, efferocytosing neutrophils released various growth factors including fibroblast growth factor-2 and hepatocyte growth factor (HGF). Accordingly, we observed an increase of HGF-positive neutrophils after PHx and a correlation of plasma HGF with M30 levels. CONCLUSIONS: These data suggest that the clearance of PHx-induced aEVs leads to a population of non-inflammatory but regenerative neutrophils, which may support human liver regeneration. LAY SUMMARY: In this study, we show that the surgical removal of a diseased part of the liver triggers a specific type of programmed cell death in the residual liver tissue. This results in the release of vesicles from dying cells into the blood, where they are cleared by circulating immune cells. These respond by secreting hepatocyte growth factors that could potentially support the regeneration of the liver remnant.

Metastatic colorectal carcinoma-associated fibroblasts have immunosuppressive properties related to increased IGFBP2 expression.

Fibroblasts are the most abundant stromal constituents of the tumour microenvironment in primary as well as metastatic colorectal cancer (CRC). Their supportive effect on tumour cells is well established. There is growing evidence that stromal fibroblasts also modulate the immune microenvironment in tumours. Here, we demonstrate a difference in fibroblast-mediated immune modulation between primary CRC and peritoneal metastasis. Cancer-associated fibroblasts (CAFs) were isolated from primary cancer and from peritoneal metastases (MAFs) from a total of 17 patients. The ectoenzyme CD38 was consistently expressed on the surface of all MAFs, while it was absent from CAFs. Furthermore, MAFs secreted higher levels of IGFBP2, CXCL2, CXCL6, CXCL12, PDGF-AA, FGFb, and IL-6. This was associated with a decreased activation of macrophages and a suppression of CD25 expression and proliferation of co-cultivated T-cells. Downregulation of IGFBP2 abolished these immunosuppressive effects of MAFs. Taken together, these results show that MAFs contribute to an immunosuppressive tumour microenvironment in CRC metastases by modulating the phenotype of immune cells through an IGFBP2-dependent mechanism.

FBW7 couples structural integrity with functional output of primary cilia.

Structural defects in primary cilia have robust effects in diverse tissues and systems. However, how disorders of ciliary length lead to functional outcomes are unknown. We examined the functional role of a ciliary length control mechanism of FBW7-mediated destruction of NDE1, in mesenchymal stem cell (MSC) differentiation. We show that FBW7 functions as a master regulator of both negative (NDE1) and positive (TALPID3) regulators of ciliogenesis, with an overall positive net effect on primary cilia formation, MSC differentiation to osteoblasts, and bone architecture. Deletion of Fbxw7 suppresses ciliation, Hedgehog activity, and differentiation, which are partially rescued in Fbxw7/Nde1-null cells. We also show that NDE1, despite suppressing ciliogenesis, promotes MSC differentiation by increasing the activity of the Hedgehog pathway by direct binding and enhancing GLI2 activity in a cilia-independent manner. We propose that FBW7 controls a protein-protein interaction network coupling ciliary structure and function, which is essential for stem cell differentiation.

Loss of polycystins suppresses deciliation via the activation of the centrosomal integrity pathway.

The primary cilium is a microtubule-based, antenna-like organelle housing several signaling pathways. It follows a cyclic pattern of assembly and deciliation (disassembly and/or shedding), as cells exit and re-enter the cell cycle, respectively. In general, primary cilia loss leads to kidney cystogenesis. However, in animal models of autosomal dominant polycystic kidney disease, a major disease caused by mutations in the polycystin genes (Pkd1 or Pkd2), primary cilia ablation or acceleration of deciliation suppresses cystic growth, whereas deceleration of deciliation enhances cystogenesis. Here, we show that deciliation is delayed in the cystic epithelium of a mouse model of postnatal deletion of Pkd1 and in Pkd1- or Pkd2-null cells in culture. Mechanistic experiments show that PKD1 depletion activates the centrosomal integrity/mitotic surveillance pathway involving 53BP1, USP28, and p53 leading to a delay in deciliation. Reduced deciliation rate causes prolonged activation of cilia-based signaling pathways that could promote cystic growth. Our study links polycystins to cilia dynamics, identifies cellular deciliation downstream of the centrosomal integrity pathway, and helps explain pro-cystic effects of primary cilia in autosomal dominant polycystic kidney disease.