The mechanism controlling long-chain fatty acid (LCFA) mobilization from adipose tissue is not well understood. Here, we investigated how the LCFA transporter CD36 regulates this process. By using tissue-specific KO mouse models, we showed that CD36 in adipocytes and endothelial cells mediated both LCFA deposition into and release from adipose tissue. We demonstrated the role of adipocytic and endothelial CD36 in promoting tumor growth and chemoresistance conferred by adipose tissue–derived LCFAs. We showed that dynamic cysteine S-acylation of CD36 in adipocytes, endothelial cells, and cancer cells mediated intercellular LCFA transport. We demonstrated that lipolysis induction in adipocytes triggered CD36 deacylation and deglycosylation, as well as its dissociation from interacting proteins, prohibitin-1 (PHB) and annexin 2 (ANX2). Our data indicate that lipolysis triggers caveolar endocytosis and translocation of CD36 from the cell membrane to lipid droplets. This study suggests a mechanism for both outside-in and inside-out cellular LCFA transport regulated by CD36 S-acylation and its interactions with PHB and ANX2.

Proper processing of collagens COL1 and COL6 is required for normal function of adipose tissue and skeletal muscle. Proteoglycan decorin (DCN) regulates collagen fiber formation. The amino-terminus of DCN is modified with an O-linked glycosaminoglycan (GAG), the function of which has remained unclear. Previously, non-glycanated DCN (ngDCN) was identified as a marker of adipose stromal cells. Here, we identify MMP14 as the metalloprotease that cleaves DCN to generate ngDCN. We demonstrate that mice ubiquitously lacking DCN GAG (ngDCN mice) have reduced matrix rigidity, enlarged adipocytes, fragile skin, as well as skeletal muscle hypotrophy, fibrosis, and dysfunction. Our results indicate that DCN deglycanation results in reduced intracellular DCN—collagen binding and increased production of truncated COL6 chains, leading to aberrant procollagen processing and extracellular localization. This study reveals that the GAG of DCN functions to regulate collagen assembly in adipose tissue and skeletal muscle and uncovers a new mechanism of matrix dysfunction in obesity and aging.

Immune checkpoint blockade therapy, transformative in some cancer types, has remained ineffective for patients with pancreatic cancer. The effects of subpopulations of cancer-associated fibroblasts (CAF) on cancer progression and therapy resistance are incompletely understood. In this study, the roles of CAFs expressing platelet-derived growth factor receptor β (Pdgfrb) and of CAFs expressing markers of adipose stromal cells (ASC) were analyzed in mice with pancreatic ductal adenocarcinoma. Ablation of Pdgfrb+ cells resulted in suppression of primary pancreatic tumor growth, reduction of extracellular matrix deposition, and increased cancer cell metastasis to the liver. A peptide D-CAN, which induces apoptosis in ASC-like CAFs, also reduced pancreatic tumor growth and extracellular matrix deposition while promoting metastases. Single-cell RNA sequencing demonstrated that depletion of either Pdgfrb+ or ASC-like CAFs decreased frequencies of tumor endothelial cells and viable cancer cells. However, whereas depletion of Pdgfrb+ CAFs led to stronger induction of cancer cell aggressiveness markers, depletion of ASC-like CAFs had an opposite effect on remaining CAFs. Depletion of ASC-like CAFs using D-CAN also led to higher infiltration of cytotoxic T-lymphocytes and B-lymphocytes. Administration of anti-PDL1 antibody (aPDL1), which inhibits the immune checkpoint, had a stronger suppressive effect on tumor growth when combined with D-CAN in both female and male mice. Liver metastases were also reduced by the D-CAN/aPDL1 combination more effectively than by aPDL1 alone in female mice. We conclude that improved approaches to target ASC-like CAFs may be effective in combination with immunotherapy. Significance: This study shows that populations of CAFs have distinct effects on pancreatic cancer progression and shows that depletion of CAFs expressing adipose markers potentiates tumor/metastasis suppression effects of immune checkpoint blockade.

Background/objectives: Progression of pancreatic ductal adenocarcinoma (PDAC) and other carcinomas relies on cancer-associated fibroblasts (CAFs). A subset of CAFs is derived from adipose stromal cells (ASCs) recruited by tumors and the ASC-CAF conversion has been associated with invasiveness and poor prognosis. Methods: To explore the underlying molecular mechanisms, we used a model based on primary ASCs derived from human visceral adipose tissue co-cultured with human PDAC cell line Capan-1. To investigate cancer progression in vivo, we also used mice orthotopically grafted with mouse KPC cells. Results: Genomic analysis revealed that Capan-1 co-culture induces Wnt and TGFβ signaling and extracellular matrix (ECM) gene expression in ASC. We investigated the function of two markers of the fibroblastic transition highly induced by cancer cells: a long non-coding RNA LINC01614 and a Wnt signaling modulator SFRP4. By using ASCs with either SFRP4 or LINC01614 knocked out (ko), we showed that both genes are required for Wnt/TGFβ signaling and ECM induction in ASCs by Capan-1. Analysis of changes in Capan-1 genes that rely on LINC01614 and SFRP4 expression in ASCs also identified the Wnt and TGF pathways. SFRP4 ko in ASCs suppressed both migration and invasion of Capan-1 cells. We show that tumors in SFRP4 ko mice have less desmoplasia, less epithelial dedifferentiation, reduced growth rate, and reduced progression to metastasis. Conclusions: We conclude that SFRP4 promotes cancer progression in pancreatic cancer and is a promising therapeutic target.

Metastasis is the leading cause of cancer-related deaths, and metastatic cancers remain largely incurable due to chemoresistance. Biomarkers of metastatic cells are lacking, and probes that could be used to detect and target metastases would be highly valuable. Here we hypothesize that metastatic cancer cells express cell-surface receptors that can be harnessed for identification of molecules homing to metastases. Screening a combinatorial library in a mouse mammary tumor model of spontaneous metastasis identified cyclic peptides with tropism for cancer cells disseminated to the lungs. Two lead peptides, CLRHSSKIC and CRAGVGRGC, bound murine and human cells derived from breast carcinoma and melanoma in culture and were selective for metastatic cells in vivo. In mice, peptide CRAGVGRGC radiolabeled with 67Ga for biodistribution analysis demonstrated selective probe homing to lung metastases. Moreover, systemic administration of 68Ga-labeled CRAGVGRGC enabled noninvasive imaging of lung metastases in mice by PET. A CRAGVGRGC-derived peptide induced apoptosis upon cell internalization in vitro and suppressed metastatic burden in vivo. Colocalization of CLRHSSKIC and CRAGVGRGC with N-cadherin+/E-cadherin− cells indicated that both peptides are selective for cancer cells that have undergone the epithelial-to-mesenchymal transition. We conclude that CRAGVGRGC is useful as a probe to facilitate the development of imaging modalities and therapies targeting metastases. Significance: This study identifies new molecules that bind metastatic cells and demonstrates their application as noninvasive imaging probes and vehicles for cytotoxic therapy delivery in preclinical cancer models.

Duchenne muscular dystrophy (DMD), caused by the loss of dystrophin, remains incurable. Reduction in muscle regeneration with DMD is associated with the accumulation of fibroadipogenic progenitors (FAPs) differentiating into myofibroblasts and leading to a buildup of the collagenous tissue aggravating DMD pathogenesis. Mesenchymal stromal cells (MSCs) expressing platelet-derived growth factor receptors (PDGFRs) are activated in muscle during DMD progression and give rise to FAPs promoting DMD progression. Here, we hypothesized that muscle dysfunction in DMD could be delayed via genetic or pharmacologic depletion of MSC-derived FAPs. In this paper, we test this hypothesis in dystrophin-deficient mdx mice. To reduce fibro/adipose infiltration and potentiate muscle progenitor cells (MPCs), we used a model for inducible genetic ablation of proliferating MSCs via a suicide transgene, viral thymidine kinase (TK), expressed under the Pdgfrb promoter. We also tested if MSCs from fat tissue, the adipose stromal cells (ASCs), contribute to FAPs and could be targeted in DMD. Pharmacological ablation was performed with a hunter-killer peptide D-CAN targeting ASCs. MSC depletion with these approaches resulted in increased endurance, measured based on treadmill running, as well as grip strength, without significantly affecting fibrosis. Although more research is needed, our results suggest that depletion of pathogenic MSCs mitigates muscle damage and delays the loss of muscle function in mouse models of DMD.