The Peptidoglycan Recognition Protein 1 confers immune evasive properties on pancreatic cancer stem cells.

OBJECTIVE: Pancreatic ductal adenocarcinoma (PDAC) has limited therapeutic options, particularly with immune checkpoint inhibitors. Highly chemoresistant 'stem-like' cells, known as cancer stem cells (CSCs), are implicated in PDAC aggressiveness. Thus, comprehending how this subset of cells evades the immune system is crucial for advancing novel therapies. DESIGN: We used the KPC mouse model (LSL-KrasG12D/+; LSL-Trp53R172H/+; Pdx-1-Cre) and primary tumour cell lines to investigate putative CSC populations. Transcriptomic analyses were conducted to pinpoint new genes involved in immune evasion. Overexpressing and knockout cell lines were established with lentiviral vectors. Subsequent in vitro coculture assays, in vivo mouse and zebrafish tumorigenesis studies, and in silico database approaches were performed. RESULTS: Using the KPC mouse model, we functionally confirmed a population of cells marked by EpCAM, Sca-1 and CD133 as authentic CSCs and investigated their transcriptional profile. Immune evasion signatures/genes, notably the gene peptidoglycan recognition protein 1 (PGLYRP1), were significantly overexpressed in these CSCs. Modulating PGLYRP1 impacted CSC immune evasion, affecting their resistance to macrophage-mediated and T-cell-mediated killing and their tumourigenesis in immunocompetent mice. Mechanistically, tumour necrosis factor alpha (TNFα)-regulated PGLYRP1 expression interferes with the immune tumour microenvironment (TME) landscape, promoting myeloid cell-derived immunosuppression and activated T-cell death. Importantly, these findings were not only replicated in human models, but clinically, secreted PGLYRP1 levels were significantly elevated in patients with PDAC. CONCLUSIONS: This study establishes PGLYRP1 as a novel CSC-associated marker crucial for immune evasion, particularly against macrophage phagocytosis and T-cell killing, presenting it as a promising target for PDAC immunotherapy.

Macrophages direct cancer cells through a LOXL2-mediated metastatic cascade in pancreatic ductal adenocarcinoma.

OBJECTIVE: The lysyl oxidase-like protein 2 (LOXL2) contributes to tumour progression and metastasis in different tumour entities, but its role in pancreatic ductal adenocarcinoma (PDAC) has not been evaluated in immunocompetent in vivo PDAC models. DESIGN: Towards this end, we used PDAC patient data sets, patient-derived xenograft in vivo and in vitro models, and four conditional genetically-engineered mouse models (GEMMS) to dissect the role of LOXL2 in PDAC. For GEMM-based studies, K-Ras +/LSL-G12D;Trp53 LSL-R172H;Pdx1-Cre mice (KPC) and the K-Ras +/LSL-G12D;Pdx1-Cre mice (KC) were crossed with Loxl2 allele floxed mice (Loxl2Exon2 fl/fl) or conditional Loxl2 overexpressing mice (R26Loxl2 KI/KI) to generate KPCL2KO or KCL2KO and KPCL2KI or KCL2KI mice, which were used to study overall survival; tumour incidence, burden and differentiation; metastases; epithelial to mesenchymal transition (EMT); stemness and extracellular collagen matrix (ECM) organisation. RESULTS: Using these PDAC mouse models, we show that while Loxl2 ablation had little effect on primary tumour development and growth, its loss significantly decreased metastasis and increased overall survival. We attribute this effect to non-cell autonomous factors, primarily ECM remodelling. Loxl2 overexpression, on the other hand, promoted primary and metastatic tumour growth and decreased overall survival, which could be linked to increased EMT and stemness. We also identified tumour-associated macrophage-secreted oncostatin M (OSM) as an inducer of LOXL2 expression, and show that targeting macrophages in vivo affects Osm and Loxl2 expression and collagen fibre alignment. CONCLUSION: Taken together, our findings establish novel pathophysiological roles and functions for LOXL2 in PDAC, which could be potentially exploited to treat metastatic disease.

Bcl3 Couples Cancer Stem Cell Enrichment With Pancreatic Cancer Molecular Subtypes.

BACKGROUND & AIMS: The existence of different subtypes of pancreatic ductal adenocarcinoma (PDAC) and their correlation with patient outcome have shifted the emphasis on patient classification for better decision-making algorithms and personalized therapy. The contribution of mechanisms regulating the cancer stem cell (CSC) population in different subtypes remains unknown. METHODS: Using RNA-seq, we identified B-cell CLL/lymphoma 3 (BCL3), an atypical nf-κb signaling member, as differing in pancreatic CSCs. To determine the biological consequences of BCL3 silencing in vivo and in vitro, we generated bcl3-deficient preclinical mouse models as well as murine cell lines and correlated our findings with human cell lines, PDX models, and 2 independent patient cohorts. We assessed the correlation of bcl3 expression pattern with clinical parameters and subtypes. RESULTS: Bcl3 was significantly down-regulated in human CSCs. Recapitulating this phenotype in preclinical mouse models of PDAC via BCL3 genetic knockout enhanced tumor burden, metastasis, epithelial to mesenchymal transition, and reduced overall survival. Fluorescence-activated cell sorting analyses, together with oxygen consumption, sphere formation, and tumorigenicity assays, all indicated that BCL3 loss resulted in CSC compartment expansion promoting cellular dedifferentiation. Overexpression of BCL3 in human PDXs diminished tumor growth by significantly reducing the CSC population and promoting differentiation. Human PDACs with low BCL3 expression correlated with increased metastasis, and BCL3-negative tumors correlated with lower survival and nonclassical subtypes. CONCLUSIONS: We demonstrate that bcl3 impacts pancreatic carcinogenesis by restraining CSC expansion and by curtailing an aggressive and metastatic tumor burden in PDAC across species. Levels of BCL3 expression are a useful stratification marker for predicting subtype characterization in PDAC, thereby allowing for personalized therapeutic approaches.

Targeting SRC Kinase Signaling in Pancreatic Cancer Stem Cells.

The proto-oncogene nonreceptor tyrosine-protein kinase SRC is a member of the SRC family of tyrosine kinases (SFKs), and its activation and overexpression have been shown to play a protumorigenic role in multiple solid cancers, including pancreatic ductal adenocarcinoma (PDAC). PDAC is currently the seventh-leading cause of cancer-related death worldwide, and, by 2030, it is predicted to become the second-leading cause of cancer-related death in the United States. PDAC is characterized by its high lethality (5-year survival of rate of <10%), invasiveness, and chemoresistance, all of which have been shown to be due to the presence of pancreatic cancer stem cells (PaCSCs) within the tumor. Due to the demonstrated overexpression of SRC in PDAC, we set out to determine if SRC kinases are important for PaCSC biology using pharmacological inhibitors of SRC kinases (dasatinib or PP2). Treatment of primary PDAC cultures established from patient-derived xenografts with dasatinib or PP2 reduced the clonogenic, self-renewal, and tumor-initiating capacity of PaCSCs, which we attribute to the downregulation of key signaling factors such as p-FAK, p-ERK1-2, and p-AKT. Therefore, this study not only validates that SRC kinases are relevant and biologically important for PaCSCs but also suggests that inhibitors of SRC kinases may represent a possible future treatment option for PDAC patients, although further studies are still needed.

Correction: Alcalá, S., et al. Targeting SRC Kinase Signaling in Pancreatic Cancer Stem Cells. Int. J. Mol. Sci. 2020, 21, 7437.

The authors recently reported on the potential of targeting SRC kinase signaling in pancreatic cancer stem cells [...].

Fresh and Aromatic Virgin Olive Oil Obtained from Arbequina, Koroneiki, and Arbosana Cultivars.

Three factors for the extraction of extra virgin olive oil (EVOO) were evaluated: diameter of the grid holes of the hammer-crusher, malaxation temperature, and malaxation time. A Box-Behnken design was used to obtain a total of 289 olive oil samples. Twelve responses were analyzed and 204 mathematical models were obtained. Olives from super-intensive rainfed or irrigated crops of the Arbequina, Koroneiki, and Arbosana cultivars at different stages of ripening were used. Malaxation temperature was found to be the factor with the most influence on the total content of lipoxygenase pathway volatile compounds; as the temperature increased, the content of volatile compounds decreased. On the contrary, pigments increased when the malaxation temperature was increased. EVOO from irrigated crops and from the Arbequina cultivar had the highest content of volatile compounds. Olive samples with a lower ripening degree, from the Koroneiki cultivar and from rainfed crops, had the highest content of pigments.

Intracellular autofluorescence: a biomarker for epithelial cancer stem cells.

Cancer stem cells (CSCs) are thought to drive tumor growth, metastasis and chemoresistance. Although surface markers such as CD133 and CD44 have been successfully used to isolate CSCs, their expression is not exclusively linked to the CSC phenotype and is prone to environmental alteration. We identified cells with an autofluorescent subcellular compartment that exclusively showed CSC features across different human tumor types. Primary tumor-derived autofluorescent cells did not overlap with side-population (SP) cells, were enriched in sphere culture and during chemotherapy, strongly expressed pluripotency-associated genes, were highly metastatic and showed long-term in vivo tumorigenicity, even at the single-cell level. Autofluorescence was due to riboflavin accumulation in membrane-bounded cytoplasmic structures bearing ATP-dependent ABCG2 transporters. In summary, we identified and characterized an intrinsic autofluorescent phenotype in CSCs of diverse epithelial cancers and used this marker to isolate and characterize these cells.

The ever-changing landscape of pancreatic cancer stem cells.

Over the past decade, the cancer stem cell (CSC) concept in solid tumors has gained enormous momentum as an attractive model to explain tumor heterogeneity. The model proposes that tumors contain a subpopulation of rare cancer cells with stem-like properties that maintain the hierarchy of the tumor and drive tumor initiation, progression, metastasis, and chemoresistance. The identification and subsequent isolation of CSCs in pancreatic ductal adenocarcinoma (PDAC) in 2007 provided enormous insight into this extremely metastatic and chemoresistant tumor and renewed hope for developing more specific therapies against this disease. Unfortunately, we have made only marginal advances in applying the knowledge learned to the development of new and more effective treatments for pancreatic cancer. The latter has been partly due to the lack of adequate in vitro and in vivo systems compounded by the use of markers that do not reproducibly nor exclusively select for an enriched CSC population. Thus, attempts to define a pancreatic CSC-specific genetic, epigenetic or proteomic signature has been challenging. Fortunately recent advances in the CSC field have overcome many of these challenges and have opened up new opportunities for developing therapies that target the CSC population. In this review, we discuss these current advances, specifically new methods for the identification and isolation of pancreatic CSCs, new insights into the metabolic profile of CSCs at the level of mitochondrial respiration, and the utility of genetically engineered mouse models as surrogate systems to both study CSC biology and evaluate CSC-specific targeted therapies in vivo.

Microenvironmental hCAP-18/LL-37 promotes pancreatic ductal adenocarcinoma by activating its cancer stem cell compartment.

OBJECTIVES: The tumour stroma/microenvironment not only provides structural support for tumour development, but more importantly it provides cues to cancer stem cells (CSCs) that regulate their self-renewal and metastatic potential. This is certainly true for pancreatic ductal adenocarcinomas (PDAC), where tumour-associated fibroblasts, pancreatic stellate cells and immune cells create an abundant paracrine niche for CSCs via microenvironment-secreted factors. Thus understanding the role that tumour stroma cells play in PDAC development and CSC biology is of utmost importance. DESIGN: Microarray analyses, tumour microarray immunohistochemical assays, in vitro co-culture experiments, recombinant protein treatment approaches and in vivo intervention studies were performed to understand the role that the immunomodulatory cationic antimicrobial peptide 18/LL-37 (hCAP-18/LL-37) plays in PDAC biology. RESULTS: We found that hCAP-18/LL-37 was strongly expressed in the stroma of advanced primary and secondary PDAC tumours and is secreted by immune cells of the stroma (eg, tumour-associated macrophages) in response to tumour growth factor-ß1 and particularly CSC-secreted Nodal/ActivinA. Treatment of pancreatic CSCs with recombinant LL-37 increased pluripotency-associated gene expression, self-renewal, invasion and tumourigenicity via formyl peptide receptor 2 (FPR2)- and P2X purinoceptor 7 receptor (P2X7R)-dependent mechanisms, which could be reversed by inhibiting these receptors. Importantly, in a genetically engineered mouse model of K-Ras-driven pancreatic tumourigenesis, we also showed that tumour formation was inhibited by either reconstituting these mice with bone marrow from cathelicidin-related antimicrobial peptide (ie, murine homologue of hCAP-18/LL-37) knockout mice or by pharmacologically inhibiting FPR2 and P2X7R. CONCLUSIONS: Thus, hCAP-18/LL-37 represents a previously unrecognised PDAC microenvironment factor that plays a critical role in pancreatic CSC-mediated tumourigenesis.

Platinum iodido drugs show potential anti-tumor activity, affecting cancer cell metabolism and inducing ROS and senescence in gastrointestinal cancer cells.

Cisplatin-based chemotherapy has associated clinical disadvantages, such as high toxicity and resistance. Thus, the development of new antitumor metallodrugs able to overcome different clinical barriers is a public healthcare priority. Here, we studied the mechanism of action of the isomers trans and cis-[PtI2(isopropylamine)2] (I5 and I6, respectively) against gastrointestinal cancer cells. We demonstrate that I5 and I6 modulate mitochondrial metabolism, decreasing OXPHOS activity and negatively affecting ATP-linked oxygen consumption rate. Consequently, I5 and I6 generated Reactive Oxygen Species (ROS), provoking oxidative damage and eventually the induction of senescence. Thus, herein we propose a loop with three interconnected processes modulated by these iodido agents: (i) mitochondrial dysfunction and metabolic disruptions; (ii) ROS generation and oxidative damage; and (iii) cellular senescence. Functionally, I5 reduces cancer cell clonogenicity and tumor growth in a pancreatic xenograft model without systemic toxicity, highlighting a potential anticancer complex that warrants additional pre-clinical studies.

Autofluorescent Cancer Stem Cells: Potential Biomarker to Predict Recurrence in Resected Colorectal Tumor.

Cancer stem cells (CSCs) in colorectal cancer (CRC) drive intratumoral heterogeneity and distant metastases. Previous research from our group showed that CSCs can be easily detected by autofluorescence (AF). The aim of the present study was to evaluate the potential role of AF CSCs as a prognostic biomarker for CRC relapse. Seventy-five freshly-resected tumors were analyzed, by flow cytometry. AF was categorized as high (H-AF) or low (L-AF), and results were correlated with histological features (grade of differentiation, presence of metastases in lymph nodes (LN), perivascular and lymphovascular invasion) and clinical variables (time to relapse and overall survival). Nineteen out of 75 (25.3%) patients experienced relapse (local or distant), 13 out of these 19 patients showed positive LNs and 6 patients had H-AF. Of note, 4 of them died before 5 years. While patients with H-AF CSCs percentages in the global population experienced 1.5 times increased relapse -HR 1.47, CI 95% (0.60 - 3.63), patients with H-AF CSC percentages and LN metastases had the highest risk of relapse; HR 7.92, p< 0.004, CI 95% (1.97 - 31.82). These data support AF as an accurate and feasible marker to identify CSCs in resected CRC. A strong statistical association between H-AF CSCs and the risk of relapse was observed, particularly in patients with positive LNs, suggesting that H-AF patients might benefit from adjuvant chemotherapy regimens and intensive surveillance due to their high propensity to experience disease recurrence.

Targeting cancer stem cell OXPHOS with tailored ruthenium complexes as a new anti-cancer strategy.

BACKGROUND: Previous studies by our group have shown that oxidative phosphorylation (OXPHOS) is the main pathway by which pancreatic cancer stem cells (CSCs) meet their energetic requirements; therefore, OXPHOS represents an Achille's heel of these highly tumorigenic cells. Unfortunately, therapies that target OXPHOS in CSCs are lacking. METHODS: The safety and anti-CSC activity of a ruthenium complex featuring bipyridine and terpyridine ligands and one coordination labile position (Ru1) were evaluated across primary pancreatic cancer cultures and in vivo, using 8 patient-derived xenografts (PDXs). RNAseq analysis followed by mitochondria-specific molecular assays were used to determine the mechanism of action. RESULTS: We show that Ru1 is capable of inhibiting CSC OXPHOS function in vitro, and more importantly, it presents excellent anti-cancer activity, with low toxicity, across a large panel of human pancreatic PDXs, as well as in colorectal cancer and osteosarcoma PDXs. Mechanistic studies suggest that this activity stems from Ru1 binding to the D-loop region of the mitochondrial DNA of CSCs, inhibiting OXPHOS complex-associated transcription, leading to reduced mitochondrial oxygen consumption, membrane potential, and ATP production, all of which are necessary for CSCs, which heavily depend on mitochondrial respiration. CONCLUSIONS: Overall, the coordination complex Ru1 represents not only an exciting new anti-cancer agent, but also a molecular tool to dissect the role of OXPHOS in CSCs. Results indicating that the compound is safe, non-toxic and highly effective in vivo are extremely exciting, and have allowed us to uncover unprecedented mechanistic possibilities to fight different cancer types based on targeting CSC OXPHOS.

Mitochondrial apoptosis induced by BH3-only molecules in the exclusive presence of endoplasmic reticular Bak.

Bak and Bax are critical apoptotic mediators that naturally localize to both mitochondria and the endoplasmic reticulum (ER). Although it is generally accepted that mitochondrial expression of Bak or Bax suffices for apoptosis initiated by BH3-only homologues, it is currently unclear whether their reticular counterparts may have a similar potential. In this study, we show that cells exclusively expressing Bak in endoplasmic membranes undergo cytochrome c mobilization and mitochondrial apoptosis in response to BimEL and Puma, even when these BH3-only molecules are also targeted to the ER. Surprisingly, calcium was necessary but not sufficient to drive the pathway, despite normal ER calcium levels. We provide evidence that calcium functions coordinately with the ER-stress surveillance machinery IRE1alpha/TRAF2 to transmit apoptotic signals from the reticulum to mitochondria. These results indicate that BH3-only mediators can rely on reticular Bak to activate an ER-to-mitochondria signalling route able to induce cytochrome c release and apoptosis independently of the canonical Bak,Bax-dependent mitochondrial gateway, thus revealing a new layer of complexity in apoptotic regulation.

An Aptamer against MNK1 for Non-Small Cell Lung Cancer Treatment.

Lung cancer is the leading cause of cancer-related death worldwide. Its late diagnosis and consequently poor survival make necessary the search for new therapeutic targets. The mitogen-activated protein kinase (MAPK)-interacting kinase 1 (MNK1) is overexpressed in lung cancer and correlates with poor overall survival in non-small cell lung cancer (NSCLC) patients. The previously identified and optimized aptamer from our laboratory against MNK1, apMNKQ2, showed promising results as an antitumor drug in breast cancer in vitro and in vivo. Thus, the present study shows the antitumor potential of apMNKQ2 in another type of cancer where MNK1 plays a significant role, such as NSCLC. The effect of apMNKQ2 in lung cancer was studied with viability, toxicity, clonogenic, migration, invasion, and in vivo efficacy assays. Our results show that apMNKQ2 arrests the cell cycle and reduces viability, colony formation, migration, invasion, and epithelial-mesenchymal transition (EMT) processes in NSCLC cells. In addition, apMNKQ2 reduces tumor growth in an A549-cell line NSCLC xenograft model. In summary, targeting MNK1 with a specific aptamer may provide an innovative strategy for lung cancer treatment.

Inhibiting NR5A2 targets stemness in pancreatic cancer by disrupting SOX2/MYC signaling and restoring chemosensitivity.

BACKGROUND: Pancreatic ductal adenocarcinoma (PDAC) is a profoundly aggressive and fatal cancer. One of the key factors defining its aggressiveness and resilience against chemotherapy is the existence of cancer stem cells (CSCs). The important task of discovering upstream regulators of stemness that are amenable for targeting in PDAC is essential for the advancement of more potent therapeutic approaches. In this study, we sought to elucidate the function of the nuclear receptor subfamily 5, group A, member 2 (NR5A2) in the context of pancreatic CSCs. METHODS: We modeled human PDAC using primary PDAC cells and CSC-enriched sphere cultures. NR5A2 was genetically silenced or inhibited with Cpd3. Assays included RNA-seq, sphere/colony formation, cell viability/toxicity, real-time PCR, western blot, immunofluorescence, ChIP, CUT&Tag, XF Analysis, lactate production, and in vivo tumorigenicity assays. PDAC models from 18 patients were treated with Cpd3-loaded nanocarriers. RESULTS: Our findings demonstrate that NR5A2 plays a dual role in PDAC. In differentiated cancer cells, NR5A2 promotes cell proliferation by inhibiting CDKN1A. On the other hand, in the CSC population, NR5A2 enhances stemness by upregulating SOX2 through direct binding to its promotor/enhancer region. Additionally, NR5A2 suppresses MYC, leading to the activation of the mitochondrial biogenesis factor PPARGC1A and a shift in metabolism towards oxidative phosphorylation, which is a crucial feature of stemness in PDAC. Importantly, our study shows that the specific NR5A2 inhibitor, Cpd3, sensitizes a significant fraction of PDAC models derived from 18 patients to standard chemotherapy. This treatment approach results in durable remissions and long-term survival. Furthermore, we demonstrate that the expression levels of NR5A2/SOX2 can predict the response to treatment. CONCLUSIONS: The findings of our study highlight the cell context-dependent effects of NR5A2 in PDAC. We have identified a novel pharmacological strategy to modulate SOX2 and MYC levels, which disrupts stemness and prevents relapse in this deadly disease. These insights provide valuable information for the development of targeted therapies for PDAC, offering new hope for improved patient outcomes. A Schematic illustration of the role of NR5A2 in cancer stem cells versus differentiated cancer cells, along with the action of the NR5A2 inhibitor Cpd3. B Overall survival of tumor-bearing mice following allocated treatment. A total of 18 PDX models were treated using a 2 x 1 x 1 approach (two animals per model per treatment); n=36 per group (illustration created with biorender.com ).

Enrichment of Refined Olive Oils with Phenolic Extracts of Olive Leaf and Exhausted Olive Pomace.

Refined olive oils (ROOs) are commonly enriched with synthetic antioxidants. Antioxidant extracts obtained from natural products can be used to improve the stability of these oils. In this study, ROOs were enriched through the addition of phenolic extracts from olive leaves (OLs) and exhausted olive pomace (EOP). In addition to replacing synthetic antioxidants with natural ones, this results in the valorization of these olive-derived biomasses. The most suitable method for mixing and enriching refined oils was probe-type ultrasonication using lecithin as the emulsifier. Thereafter, the change in the content of antioxidant compounds and the antioxidant capacity of the oils at 25, 35, and 45 °C were studied over 28 and 50 days of storage. The experimental results were fitted using a pseudo-first-order kinetic model. The oxidative stability index of the ROO enriched with a 2 g/L OL extract (70 h) was higher than that of a commercial ROO (46.8 h). Moreover, the oxidative stability index of the refined olive pomace oil (ROPO) enriched with a 2 g/L EOP extract (44.1 h) was higher than that of a commercial ROPO (38.9 h). In addition, the oxidative stabilities and antioxidant capacities of the oils were significantly correlated.

Combination of injectable multiple growth factor-releasing scaffolds and cell therapy as an advanced modality to enhance tissue neovascularization.

OBJECTIVE: Vasculogenic progenitor cell therapy for ischemic diseases bears great potential but still requires further optimization for justifying its clinical application. Here, we investigated the effects of in vivo tissue engineering by combining vasculogenic progenitors with injectable scaffolds releasing controlled amounts of proangiogenic growth factors. METHODS AND RESULTS: We produced biodegradable, injectable polylactic coglycolic acid-based scaffolds releasing single factors or combinations of vascular endothelial growth factor, hepatocyte growth factor, and angiopoietin-1. Dual and triple combinations of scaffold-released growth factors were superior to single release. In murine hindlimb ischemia models, scaffolds releasing dual (vascular endothelial growth factor and hepatocyte growth factor) or triple combinations improved effects of cord blood-derived vasculogenic progenitors. Increased migration, homing, and incorporation of vasculogenic progenitors into the vasculature augmented capillary density, translating into improved blood perfusion. Most importantly, scaffold-released triple combinations including the vessel stabilizer angiopoietin-1 enhanced the number of perivascular smooth muscle actin(+) vascular smooth muscle cells, indicating more efficient vessel stabilization. CONCLUSIONS: Vasculogenic progenitor cell therapy is significantly enhanced by in vivo tissue engineering providing a proangiogenic and provasculogenic growth factor-enriched microenvironment. Therefore, combined use of scaffold-released growth factors and cell therapy improves neovascularization in ischemic diseases and may translate into more pronounced clinical effects.

Inhibition of Mitochondrial Dynamics Preferentially Targets Pancreatic Cancer Cells with Enhanced Tumorigenic and Invasive Potential.

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest tumors, partly due to its intrinsic aggressiveness, metastatic potential, and chemoresistance of the contained cancer stem cells (CSCs). Pancreatic CSCs strongly rely on mitochondrial metabolism to maintain their stemness, therefore representing a putative target for their elimination. Since mitochondrial homeostasis depends on the tightly controlled balance between fusion and fission processes, namely mitochondrial dynamics, we aim to study this mechanism in the context of stemness. In human PDAC tissues, the mitochondrial fission gene DNM1L (DRP1) was overexpressed and positively correlated with the stemness signature. Moreover, we observe that primary human CSCs display smaller mitochondria and a higher DRP1/MFN2 expression ratio, indicating the activation of the mitochondrial fission. Interestingly, treatment with the DRP1 inhibitor mDivi-1 induced dose-dependent apoptosis, especially in CD133+ CSCs, due to the accumulation of dysfunctional mitochondria and the subsequent energy crisis in this subpopulation. Mechanistically, mDivi-1 inhibited stemness-related features, such as self-renewal, tumorigenicity, and invasiveness and chemosensitized the cells to the cytotoxic effects of Gemcitabine. In summary, mitochondrial fission is an essential process for pancreatic CSCs and represents an attractive target for designing novel multimodal treatments that will more efficiently eliminate cells with high tumorigenic potential.

Dysregulated splicing factor SF3B1 unveils a dual therapeutic vulnerability to target pancreatic cancer cells and cancer stem cells with an anti-splicing drug.

BACKGROUND: Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal cancer, requiring novel treatments to target both cancer cells and cancer stem cells (CSCs). Altered splicing is emerging as both a novel cancer hallmark and an attractive therapeutic target. The core splicing factor SF3B1 is heavily altered in cancer and can be inhibited by Pladienolide-B, but its actionability in PDAC is unknown. We explored the presence and role of SF3B1 in PDAC and interrogated its potential as an actionable target. METHODS: SF3B1 was analyzed in PDAC tissues, an RNA-seq dataset, and publicly available databases, examining associations with splicing alterations and key features/genes. Functional assays in PDAC cell lines and PDX-derived CSCs served to test Pladienolide-B treatment effects in vitro, and in vivo in zebrafish and mice. RESULTS: SF3B1 was overexpressed in human PDAC and associated with tumor grade and lymph-node involvement. SF3B1 levels closely associated with distinct splicing event profiles and expression of key PDAC players (KRAS, TP53). In PDAC cells, Pladienolide-B increased apoptosis and decreased multiple tumor-related features, including cell proliferation, migration, and colony/sphere formation, altering AKT and JNK signaling, and favoring proapoptotic splicing variants (BCL-XS/BCL-XL, KRASa/KRAS, Δ133TP53/TP53). Importantly, Pladienolide-B similarly impaired CSCs, reducing their stemness capacity and increasing their sensitivity to chemotherapy. Pladienolide-B also reduced PDAC/CSCs xenograft tumor growth in vivo in zebrafish and in mice. CONCLUSION: SF3B1 overexpression represents a therapeutic vulnerability in PDAC, as altered splicing can be targeted with Pladienolide-B both in cancer cells and CSCs, paving the way for novel therapies for this lethal cancer.

Targeting MAD2 modulates stemness and tumorigenesis in human Gastric Cancer cell lines.

Rationale: Gastric cancer (GC) is a solid tumor that contains subpopulations of cancer stem cells (CSCs), which are considered drivers of tumor initiation and metastasis; responsible for therapeutic resistance; and promoters of tumor relapse. The balance between symmetric and asymmetric division is crucial for stem cell maintenance. The objective of this study is to evaluate the role of MAD2, a key protein for proper mitotic checkpoint activity, in the tumorigenesis of GC. Methods: Gastric cancer stem cells (GCSCs) were obtained from MKN45, SNU638 and ST2957 cell lines. Pluripotency and stemness markers were evaluated by RT-qPCR and autofluorescence and membrane markers by flow cytometry. Relevant signal transduction pathways were studied by WB. We analysed cell cycle progression, migration and invasion after modulation of MAD2 activity or protein expression levels in these in vitro models. In vivo assays were performed in a nude mouse subcutaneous xenograft model. Results: We found that NANOG, CXCR4 and autofluorescence are common and consistent markers for the GCSCs analysed, with other markers showing more variability. The three main signalling pathways (Wnt/ß-catenin; Hedgehog and Notch) were activated in GCSCs. Downregulation of MAD2 in MKN45CSCs decreased the expression of markers CXCR4, CD133, CD90, LGR5 and VIM, without affecting cell cycle profile or therapy resistance. Moreover, migration, invasion and tumor growth were clearly reduced, and accordingly, we found that metalloprotease expression decreased. These results were accompanied by a reduction in the levels of transcription factors related with epithelial-to-mesenchymal transition. Conclusions: We can conclude that MAD2 is important for GCSCs stemness and its downregulation in MKN45CSCs plays a central role in GC tumorigenesis, likely through CXCR4-SNAI2-MMP1. Thus, its potential use in the clinical setting should be studied as its functions appear to extend beyond mitosis.