IDO1 oxidizes tryptophan (TRP) to generate kynurenine (KYN), the substrate for 1-carbon and NAD metabolism, and is implicated in pro-cancer pathophysiology and infection biology. However, the mechanistic relationships between IDO1 in amino acid depletion versus product generation have remained a longstanding mystery. We found an unrecognized link between IDO1 and cell survival mediated by KYN that serves as the source for molecules that inhibit ferroptotic cell death. We show that this effect requires KYN export from IDO1-expressing cells, which is then available for non-IDO1-expressing cells via SLC7A11, the central transporter involved in ferroptosis suppression. Whether inside the "producer" IDO1⁺ cell or the "receiver" cell, KYN is converted into downstream metabolites, suppressing ferroptosis by ROS scavenging and activating an NRF2-dependent, AHR-independent cell-protective pathway, including SLC7A11, propagating anti-ferroptotic signaling. IDO1, therefore, controls a multi-pronged protection pathway from ferroptotic cell death, underscoring the need to re-evaluate the use of IDO1 inhibitors in cancer treatment.

Interleukin-4-induced-1 (IL4i1) is an amino acid oxidase secreted from immune cells. Recent observations have suggested that IL4i1 is pro-tumorigenic via unknown mechanisms. As IL4i1 has homologs in snake venoms (L-amino acid oxidases [LAAO]), we used comparative approaches to gain insight into the mechanistic basis of how conserved amino acid oxidases regulate cell fate and function. Using mammalian expressed recombinant proteins, we found that venom LAAO kills cells via hydrogen peroxide generation. By contrast, mammalian IL4i1 is non-cytotoxic and instead elicits a cell protective gene expression program inhibiting ferroptotic redox death by generating indole-3-pyruvate (I3P) from tryptophan. I3P suppresses ferroptosis by direct free radical scavenging and through the activation of an anti-oxidative gene expression program. Thus, the pro-tumor effects of IL4i1 are likely mediated by local anti-ferroptotic pathways via aromatic amino acid metabolism, arguing that an IL4i1 inhibitor may modulate tumor cell death pathways.

Telomerase (TERT) is a ribonucleoprotein enzyme that preserves the molecular organization at the ends of eukaryotic chromosomes. Since TERT deregulation is a common step in leukaemia, treatments targeting telomerase might be useful for the therapy of hematologic malignancies. Despite a large spectrum of potential drugs, their bench-to-bedside translation is quite limited, with only a therapeutic vaccine in the clinic and a telomerase inhibitor at late stage of preclinical validation. We recently demonstrated that the adoptive transfer of T cell transduced with an HLA-A2-restricted T-cell receptor (TCR), which recognize human TERT with high avidity, controls human B-cell chronic lymphocytic leukaemia (B-CLL) progression without severe side-effects in humanized mice. In the present report, we show the ability of our approach to limit the progression of more aggressive leukemic pathologies, such as acute myeloid leukaemia (AML) and B-cell acute lymphoblastic leukaemia (B-ALL). Together, our findings demonstrate that TERT-based adoptive cell therapy is a concrete platform of T cell-mediated immunotherapy for leukaemia treatment.

Hyperforin (HPF) is an acylphloroglucinol compound found abundantly in Hypericum perforatum extract which exhibits antidepressant, anti-inflammatory, antimicrobial, and antitumor activities. Our recent study revealed a potent antimelanoma effect of HPF, which hinders melanoma cell proliferation, motility, colony formation, and induces apoptosis. Furthermore, we have identified glutathione peroxidase-4 (GPX-4), a key enzyme involved in cellular protection against iron-induced lipid peroxidation, as one of the molecular targets of HPF. Thus, in three BRAF-mutated melanoma cell lines, we investigated whether iron unbalance and lipid peroxidation may be a part of the molecular mechanisms underlying the antimelanoma activity of HPF. Initially, we focused on heme oxygenase-1 (HO-1), which catalyzes the heme group into CO, biliverdin, and free iron, and observed that HPF treatment triggered the expression of this inducible enzyme. In order to investigate the mechanism involved in HO-1 induction, we verified that HPF downregulates the BTB and CNC homology 1 (BACH-1) transcription factor, an inhibitor of the heme oxygenase 1 (HMOX-1) gene transcription. Remarkably, we observed a partial recovery of cell viability and an increase in the expression of the phosphorylated and active form of retinoblastoma protein when we suppressed the HMOX-1 gene using HMOX-1 siRNA while HPF was present. This suggests that the HO-1 pathway is involved in the cytostatic effect of HPF in melanoma cells. To explore whether lipid peroxidation is induced, we conducted cytofluorimetric analysis and observed a significant increase in the fluorescence of the BODIPY C-11 probe 48 h after HPF administration in all tested melanoma cell lines. To discover the mechanism by which HPF triggers lipid peroxidation, along with the induction of HO-1, we examined the expression of additional proteins associated with iron homeostasis and lipid peroxidation. After HPF administration, we confirmed the downregulation of GPX-4 and observed low expression levels of SLC7A11, a cystine transporter crucial for the glutathione production, and ferritin, able to sequester free iron. A decreased expression level of these proteins can sensitize cells to lipid peroxidation. On the other hand, HPF treatment resulted in increased expression levels of transferrin, which facilitates iron uptake, and LC3B proteins, a molecular marker of autophagy induction. Indeed, ferritin and GPX-4 have been reported to be digested during autophagy. Altogether, these findings suggest that HPF induced lipid peroxidation likely through iron overloading and decreasing the expression of proteins that protect cells from lipid peroxidation. Finally, we examined the expression levels of proteins associated with melanoma cell invasion and metastatic potential. We observed the decreased expression of CD133, octamer-4, tyrosine-kinase receptor AXL, urokinase plasminogen activator receptor, and metalloproteinase-2 following HPF treatment. These findings provide further support for our previous observations, demonstrating the inhibitory effects of HPF on cell motility and colony formation in soft agar, which are both metastasis-related processes in tumor cells.

Obesity-related diseases and perturbations of fat metabolism represent some of the most common health challenges. In this complex scenario, recent evidence has suggested the emergence of a condition related to fat accumulation in the pancreas, which is generally referred to as fatty pancreas disease. This study aimed to clarify the different compartments of intrapancreatic fat deposition. The study cohort is represented by 100 patients who underwent pancreatic surgical resection. The pancreatic neck margin was analyzed with hematoxylin and eosin for evaluating tissue composition and with Oil Red O, a fat-specific histochemical staining, highlighting lipid droplets as red signals, for evaluating the presence of intracellular fat. Two cases were also analyzed with electron microscopy as cross-sectional validation. Regarding tissue composition, the most prevalent component was normal pancreatic parenchyma (mean value, 71.8%), followed by fibrosis (17.3%) and interlobular/intralobular fat (10.9%). Regarding intracellular fat deposition, Oil Red O-positive intracytoplasmic lipid droplets were present in most patients. The tissue areas with the highest levels of fat deposition were Langerhans' islets, with neuroendocrine/insular cells showing more commonly a diffuse pattern of fat accumulation (>75% of cells). Electron microscopy confirmed the presence of intracytoplasmic lipid vacuoles in neuroendocrine/insular cells. Our findings showed the presence of different compartments of intrapancreatic fat deposition, both in terms of tissue composition and intracellular compartmentalization. Understanding the mechanisms of fat deposition in the pancreas is crucial toward improving the general knowledge on fatty pancreas disease, also opening new perspectives for the study of lipid metabolism and the treatment of fat-related diseases.

Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal cancer marked by poor prognosis and frequent gain‐of‐function mutations in the TP53 tumor suppressor gene. Given the crucial role of mutant p53 in the context of metabolic reprogramming and aggressive tumor behavior, we explored its role on mitochondria, which may present a valuable therapeutic target. In this study, we characterized the unique mitochondrial proteome observed in PDAC cells harboring the gain‐of‐function TP53 ^R273H mutation and discovered a strong mutant p53‐dependent upregulation of myosin heavy chain 14 (MYH14), a nonmuscle myosin, implicated in mitochondrial dynamics. We deeply investigated the role of mutant p53 in the regulation of mitochondrial architecture and functionality in PDAC cells. Our morphological and morphometric analyses with transmission electron microscopy and three‐dimensional confocal imaging revealed that mutant p53 induced marked mitochondrial fragmentation, whereas wild‐type p53 stimulated mitochondrial elongation. Interestingly, the fragmented mitochondrial morphology is associated with higher mitochondrial respiration levels and more efficient mitochondrial cristae. These findings support the role of oncogenic mutant p53 isoforms in inducing mitochondrial fragmentation through a mechanism involving MYH14, resulting in an increased oxidative phosphorylation level that may support PDAC cell growth and aggressiveness.