Fatty acid oxidation is critical for the tumorigenic potential and chemoresistance of pancreatic cancer stem cells.

BACKGROUND: We have previously demonstrated the significant reliance of pancreatic Cancer Stem Cells (PaCSCs) on mitochondrial oxidative phosphorylation (OXPHOS), which enables versatile substrate utilization, including fatty acids (FAs). Notably, dysregulated lipid scavenging and aberrant FA metabolism are implicated in PDAC progression. METHODS & RESULTS: Our bioinformatics analyses revealed elevated expression of lipid metabolism-related genes in PDAC tissue samples compared to normal tissue samples, which correlated with a stemness signature. Additionally, PaCSCs exhibited heightened expression of diverse lipid metabolism genes and increased lipid droplet accumulation compared to differentiated progenies. Treatment with palmitic, oleic, and linolenic FAs notably augmented the self-renewal and chemotherapy resistance of CD133+ PaCSCs. Conversely, inhibitors of FA uptake, storage and metabolism reduced CSC populations both in vitro and in vivo. Mechanistically, inhibition of FA metabolism suppressed OXPHOS activity, inducing energy depletion and subsequent cell death in PaCSCs. Importantly, combining a FAO inhibitor and Gemcitabine treatment enhanced drug efficacy in vitro and in vivo, effectively diminishing the CSC content and functionality. CONCLUSION: Targeting FAO inhibition represents a promising therapeutic strategy against this highly tumorigenic population.

Ex vivo effect of JAK inhibition on JAK-STAT1 pathway hyperactivation in patients with dominant-negative STAT3 mutations.

PURPOSE: STAT1 gain-of-function (GOF) and dominant-negative (DN) STAT3 syndromes share clinical manifestations including infectious and inflammatory manifestations. Targeted treatment with Janus-kinase (JAK) inhibitors shows promising results in treating STAT1 GOF-associated symptoms while management of DN STAT3 patients has been largely supportive. We here assessed the impact of ruxolitinib on the JAK-STAT1/3 pathway in DN STAT3 patients' cells. METHODS: Using flow cytometry, immunoblot, qPCR, and ELISA techniques, we examined the levels of basal STAT1 and phosphorylated STAT1 (pSTAT1) of cells obtained from DN STAT3, STAT1 GOF patients, and healthy donors following stimulation with type I/II interferons (IFNs) or interleukin (IL)-6. We also describe the impact of ruxolitinib on cytokine-induced STAT1 signaling in these patients. RESULTS: DN STAT3 and STAT1 GOF resulted in a similar phenotype characterized by increased STAT1 and pSTAT1 levels in response to IFNα (CD3+ cells) and IFNγ (CD14+ monocytes). STAT1-downstream gene expression and C-X-C motif chemokine 10 secretion were higher in most DN STAT3 patients upon stimulation compared to healthy controls. Ex vivo treatment with the JAK1/2-inhibitor ruxolitinib reduced cytokine responsiveness and normalized STAT1 phosphorylation in DN STAT3 and STAT1 GOF patient' cells. In addition, ex vivo treatment was effective in modulating STAT1 downstream signaling in DN STAT3 patients. CONCLUSION: In the absence of effective targeted treatment options for AD-HIES at present, modulation of the JAK/STAT1 pathway with JAK inhibitors may be further explored particularly in those AD-HIES patients with autoimmune and/or autoinflammatory manifestations.

Biallelic TRAF3IP2 variants causing chronic mucocutaneous candidiasis in a child harboring a STAT1 variant.

BACKGROUND: Inherited chronic mucocutaneous candidiasis (CMC) is often caused by inborn errors of immunity, impairing the response to, or the production of IL-17A and IL-17F. About half of the cases carry STAT1 gain-of-function (GOF) mutations. Only few patients have been reported with mutations of TRAF3IP2, a gene encoding the adaptor ACT1 essential for IL-17 receptor(R) signaling. We investigated a 10-year-old girl with CMC, carrying a heterozygous variant of STAT1 and compound heterozygous variants of TRAF3IP2. METHODS: By flow cytometry, STAT1 levels and phosphorylation (CD14+) as well as IL-17A, IL-22, IFN-γ, and IL-4 production (memory CD4+ T cells) were determined. ACT1 expression and binding to IL-17RA were assessed by Western blot and co-immunoprecipitation in HEK-293T cells transfected with plasmids encoding wild-type or mutant HA-tagged ACT1 and Flag-IL-17RA. We evaluated IL-17A responses by measuring luciferase induction under a NF-κB-driven reporter system in HEK-293T cells and Gro-α secretion in fibroblasts. RESULTS: A STAT1 variant (c.1363G>A/p.V455I) was identified by next-generation sequencing and classified as likely non-pathogenic as functional testing revealed normal STAT1 expression and phosphorylation upon IFN-γ. We also found compound heterozygous variants (c.1325A>G/p.D451G and c.1335delA/p.K454fs11*) of TRAF3IP2. By overexpression, despite normal protein expression, and impaired (K454fs11*) or normal (D451G) interaction with IL-17RA, both mutant alleles resulted in impaired NF-κB activation. Patient's fibroblasts displayed abolished GRO-α secretion upon IL-17A stimulation. Finally, ex vivo CD4+ T cells showed increased IL-17A, IL-22, and IL-4 and normal low IFN-γ expression upon stimulation. CONCLUSION: We identify novel compound heterozygous variants of TRAFP3IP2 causing autosomal recessive ACT1 deficiency in a child with CMC and provide a review of the current literature.

Pharmacological targeting of the receptor ALK inhibits tumorigenicity and overcomes chemoresistance in pancreatic ductal adenocarcinoma.

Pancreatic ductal adenocarcinoma (PDAC) is an extremely aggressive disease characterized by its metastatic potential and chemoresistance. These traits are partially attributable to the highly tumorigenic pancreatic cancer stem cells (PaCSCs). Interestingly, these cells show unique features in order to sustain their identity and functionality, some of them amenable for therapeutic intervention. Screening of phospho-receptor tyrosine kinases revealed that PaCSCs harbored increased activation of anaplastic lymphoma kinase (ALK). We subsequently demonstrated that oncogenic ALK signaling contributes to tumorigenicity in PDAC patient-derived xenografts (PDXs) by promoting stemness through ligand-dependent activation. Indeed, the ALK ligands midkine (MDK) or pleiotrophin (PTN) increased self-renewal, clonogenicity and CSC frequency in several in vitro local and metastatic PDX models. Conversely, treatment with the clinically-approved ALK inhibitors Crizotinib and Ensartinib decreased PaCSC content and functionality in vitro and in vivo, by inducing cell death. Strikingly, ALK inhibitors sensitized chemoresistant PaCSCs to Gemcitabine, as the most used chemotherapeutic agent for PDAC treatment. Consequently, ALK inhibition delayed tumor relapse after chemotherapy in vivo by effectively decreasing the content of PaCSCs. In summary, our results demonstrate that targeting the MDK/PTN-ALK axis with clinically-approved inhibitors impairs in vivo tumorigenicity and chemoresistance in PDAC suggesting a new treatment approach to improve the long-term survival of PDAC patients.