Identification of myoferlin as a mitochondria-associated membranes component required for calcium signaling in PDAC cell lines.

BACKGROUND: Pancreatic ductal adenocarcinoma is an aggressive cancer type with one of the lowest survival rates due to late diagnosis and the absence of effective treatments. A better understanding of PDAC biology will help researchers to discover the Achilles' heel of cancer cells. In that regard, our research team investigated the function of an emerging oncoprotein known as myoferlin. Myoferlin is overexpressed in PDAC and its silencing/targeting has been shown to affect cancer cell proliferation, migration, mitochondrial dynamics and metabolism. Nevertheless, our comprehension of myoferlin functions in cells remains limited. In this study, we aimed to understand the molecular mechanism linking myoferlin silencing to mitochondrial dynamics. METHODS: Experiments were performed on two pancreas cancer cell lines, Panc-1 and MiaPaCa-2. Myoferlin localization on mitochondria was evaluated by immunofluorescence, proximity ligation assay, and cell fractionation. The presence of myoferlin in mitochondria-associated membranes was assessed by cell fractionation and its function in mitochondrial calcium transfer was evaluated using calcium flow experiments, proximity ligation assays, co-immunoprecipitation, and timelapse fluorescence microscopy in living cells. RESULTS: Myoferlin localization on mitochondria was investigated. Our results suggest that myoferlin is unlikely to be located on mitochondria. Instead, we identified myoferlin as a new component of mitochondria-associated membranes. Its silencing significantly reduces the mitochondrial calcium level upon stimulation, probably through myoferlin interaction with the inositol 1,4,5-triphosphate receptors 3. CONCLUSIONS: For the first time, myoferlin was specifically demonstrated to be located in mitochondria-associated membranes where it participates to calcium flow. We hypothesized that this function explains our previous results on mitochondrial dynamics. This study improves our comprehension of myoferlin localization and function in cancer biology.

Methylglyoxal: a novel upstream regulator of DNA methylation.

BACKGROUND: Aerobic glycolysis, also known as the Warburg effect, is predominantly upregulated in a variety of solid tumors, including breast cancer. We have previously reported that methylglyoxal (MG), a very reactive by-product of glycolysis, unexpectedly enhanced the metastatic potential in triple negative breast cancer (TNBC) cells. MG and MG-derived glycation products have been associated with various diseases, such as diabetes, neurodegenerative disorders, and cancer. Glyoxalase 1 (GLO1) exerts an anti-glycation defense by detoxifying MG to D-lactate. METHODS: Here, we used our validated model consisting of stable GLO1 depletion to induce MG stress in TNBC cells. Using genome-scale DNA methylation analysis, we report that this condition resulted in DNA hypermethylation in TNBC cells and xenografts. RESULTS: GLO1-depleted breast cancer cells showed elevated expression of DNMT3B methyltransferase and significant loss of metastasis-related tumor suppressor genes, as assessed using integrated analysis of methylome and transcriptome data. Interestingly, MG scavengers revealed to be as potent as typical DNA demethylating agents at triggering the re-expression of representative silenced genes. Importantly, we delineated an epigenomic MG signature that effectively stratified TNBC patients based on survival. CONCLUSION: This study emphasizes the importance of MG oncometabolite, occurring downstream of the Warburg effect, as a novel epigenetic regulator and proposes MG scavengers to reverse altered patterns of gene expression in TNBC.

Cancer-Associated Fibroblast Diversity Shapes Tumor Metabolism in Pancreatic Cancer.

Despite extensive research, the 5-year survival rate of pancreatic cancer (PDAC) patients remains at only 9%. Patients often show poor treatment response, due partly to a highly complex tumor microenvironment (TME). Cancer-associated fibroblast (CAF) heterogeneity is characteristic of the pancreatic TME, where several CAF subpopulations have been identified, such as myofibroblastic CAFs (myCAFs), inflammatory CAFs (iCAFs), and antigen presenting CAFs (apCAFs). In PDAC, cancer cells continuously adapt their metabolism (metabolic switch) to environmental changes in pH, oxygenation, and nutrient availability. Recent advances show that these environmental alterations are all heavily driven by stromal CAFs. CAFs and cancer cells exchange cytokines and metabolites, engaging in a tight bidirectional crosstalk, which promotes tumor aggressiveness and allows constant adaptation to external stress, such as chemotherapy. In this review, we summarize CAF diversity and CAF-mediated metabolic rewiring, in a PDAC-specific context. First, we recapitulate the most recently identified CAF subtypes, focusing on the cell of origin, activation mechanism, species-dependent markers, and functions. Next, we describe in detail the metabolic crosstalk between CAFs and tumor cells. Additionally, we elucidate how CAF-driven paracrine signaling, desmoplasia, and acidosis orchestrate cancer cell metabolism. Finally, we highlight how the CAF/cancer cell crosstalk could pave the way for new therapeutic strategies.

Myoferlin targeting triggers mitophagy and primes ferroptosis in pancreatic cancer cells.

Myoferlin, an emerging oncoprotein, has been associated with a low survival in several cancer types including pancreas ductal adenocarcinoma where it controls mitochondria structure and respiratory functions. Owing to the high susceptibility of KRAS-mutated cancer cells to iron-dependent cell death, ferroptosis, and to the high iron content in mitochondria, we investigated the relation existing between mitochondrial integrity and iron-dependent cell death. We discovered that myoferlin targeting with WJ460 pharmacological compound triggered mitophagy and ROS accumulation culminating with lipid peroxidation and apoptosis-independent cell death. WJ460 caused a reduction of the abundance of ferroptosis core regulators xc- cystine/glutamate transporter and GPX-4. Mitophagy inhibitor Mdivi1 and iron chelators inhibited the myoferlin-related ROS production and restored cell growth. Additionally, we reported a synergic effect between ferroptosis inducers, erastin and RSL3, and WJ460.