Pancreatic Ductal Adenocarcinoma Initiation Research Articles

Ras-dependent activation of BMAL2 regulates hypoxic metabolism in pancreatic cancer.

To identify drivers of malignancy in human pancreatic ductal adenocarcinoma (PDAC), we performed regulatory network analysis on a large collection of expression profiles from laser capture microdissected samples of PDAC and benign precursors. We discovered that BMAL2 plays a role in the initiation, progression, post resection survival, and KRAS activity in PDAC. Functional analysis of BMAL2 target genes led us to hypothesize that it plays a role in regulating the response to hypoxia, a critical but poorly understood feature of PDAC physiology. Knockout of BMAL2 in multiple human PDAC cell lines revealed effects on viability and invasion, particularly under hypoxic conditions. Loss of BMAL2 also affected glycolysis and other metabolic processes. We found that BMAL2 directly regulates hypoxia-responsive target genes. We also found that BMAL2 is necessary for the stabilization of HIF1A upon exposure to hypoxia, but destabilizes HIF2A under hypoxia. These data demonstrate that BMAL2 is a master transcriptional regulator of hypoxia responses in PDAC and may serve as a long-sought molecular switch that distinguishes HIF1A- and HIF2A-dependent modes of hypoxic metabolism.

KRAS-mediated upregulation of CIP2A promotes suppression of PP2A-B56α to initiate pancreatic cancer development.

Oncogenic mutations in KRAS are present in approximately 95% of patients diagnosed with pancreatic ductal adenocarcinoma (PDAC) and are considered the initiating event of pancreatic intraepithelial neoplasia (PanIN) precursor lesions. While it is well established that KRAS mutations drive the activation of oncogenic kinase cascades during pancreatic oncogenesis, the effects of oncogenic KRAS signaling on regulation of phosphatases during this process is not fully appreciated. Protein Phosphatase 2A (PP2A) has been implicated in suppressing KRAS-driven cellular transformation. However, low PP2A activity is observed in PDAC cells compared to non-transformed cells, suggesting that suppression of PP2A activity is an important step in the overall development of PDAC. In the current study, we demonstrate that KRASG12D induces the expression of both an endogenous inhibitor of PP2A activity, Cancerous Inhibitor of PP2A (CIP2A), and the PP2A substrate, c-MYC. Consistent with these findings, KRASG12D sequestered the specific PP2A subunit responsible for c-MYC degradation, B56α, away from the active PP2A holoenzyme in a CIP2A-dependent manner. During PDAC initiation in vivo, knockout of B56α promoted KRASG12D tumorigenesis by accelerating acinar-to-ductal metaplasia (ADM) and the formation of PanIN lesions. The process of ADM was attenuated ex vivo in response to pharmacological re-activation of PP2A utilizing direct small molecule activators of PP2A (SMAPs). Together, our results suggest that suppression of PP2A-B56α through KRAS signaling can promote the MYC-driven initiation of pancreatic tumorigenesis.

Driver Mutations in Pancreatic Cancer and Opportunities for Targeted Therapy.

Pancreatic cancer is the sixth leading cause of cancer-related mortality globally. As the most common form of pancreatic cancer, pancreatic ductal adenocarcinoma (PDAC) represents up to 95% of all pancreatic cancer cases, accounting for more than 300,000 deaths annually. Due to the lack of early diagnoses and the high refractory response to the currently available treatments, PDAC has a very poor prognosis, with a 5-year overall survival rate of less than 10%. Targeted therapy and immunotherapy are highly effective and have been used for the treatment of many types of cancer; however, they offer limited benefits in pancreatic cancer patients due to tumor-intrinsic and extrinsic factors that culminate in drug resistance. The identification of key factors responsible for PDAC growth and resistance to different treatments is highly valuable in developing new effective therapeutic strategies. In this review, we discuss some molecules which promote PDAC initiation and progression, and their potential as targets for PDAC treatment. We also evaluate the challenges associated with patient outcomes in clinical trials and implications for future research.

Abstract 1466: Tobacco carcinogen impacts redox pathway to facilitate pancreatic ductal adenocarcinoma (PDAC) initiation and progression

Abstract The 5-year survival rate for pancreatic ductal adenocarcinoma (PDAC) is only 10%. PDAC is projected to soon become the second leading cause of cancer death. Tobacco is one of the main risk factors for PDAC. Incidence of PDAC increases 2-fold among tobacco users, and 20-35% of PDAC cases are attributed to smoking. However, the specific pathways activated by tobacco carcinogens remain elusive.This research project addresses the impact of carcinogens in pancreatic cancer etiology. We hypothesize that carcinogens in tobacco increase reactive oxygen species (ROS), which elevates the Nrf2 redox pathway to facilitate PDAC initiation and progression. Specifically, we focus on two major subclasses of carcinogens: the heavy metal cadmium (Cd) and the polycyclic aromatic hydrocarbon (PAH) benzo(a)pyrene (BaP). Using mouse pancreatic ductal organoid cultures, we found that acute carcinogen exposure increases Nrf2 activity, which is sustained after "intermediate" exposure (5 passages). Intriguingly, chronic exposure (10 passages) downregulates Nrf2 activity, which has been shown to be associated with acquired metastatic potential. Furthermore, we found an upregulation in NFkB and EGFR signaling after intermediate exposure, which are involved in microenvironment remodeling and increased proliferative potential. Overall, we demonstrate that acute carcinogen exposure elevates ROS levels and activates the Nrf2 pathway, whereas prolonged exposure upregulates NFkB and EGFR pathways. Furthermore, we have established a novel carcinogenesis model using 3D organoid culture to recapitulate each step in pancreatic tumorigenesis. Collectively, this project contributes to our understanding of tobacco-related PDAC pathogenesis. Citation Format: Xiaoxue Lin, McKenna Stamp, Alexandra Fowler, Chelsea Bottomley, Shira Okhovat, Kristina Peck, Dannielle Engle. Tobacco carcinogen impacts redox pathway to facilitate pancreatic ductal adenocarcinoma (PDAC) initiation and progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1466.

Abstract 2896: Elucidating the role of transglutaminase 2 (TGM2) in pancreatic ductal adenocarcinoma pathogenesis and its therapeutic implications

Abstract Pancreatic cancer remains one of the deadliest malignancies, with limited therapeutic options and a poor prognosis due to delayed symptom presentation and disease detection. Pancreatic ductal adenocarcinoma (PDAC) has a 5-year survival rate of less than 8%, predominantly attributed to oncogenic KRAS mutations and loss-of-function mutations in TP53, SMAD4, and P16. Our lab is interested in studying Transglutaminase 2 (TGM2), a multifunctional enzyme involved in protein cross-linking and cellular signaling, because it is highly correlated with cancer cell survival, malignancy, metastasis, and treatment resistance. Clinically, overexpression of TGM2 is associated with poorer survival in patients with Pancreatic Ductal Adenocarcinoma so it is imperative to understand the mechanism of its action in disease progression. To elucidate the role of TGM2 in PDAC, we studied the targeted deletion of TGM2 in the context of a mouse model of PDAC and saw a significant reduction in PDAC incidence and precursor lesion formation, suggesting that TGM2 has a role in the tumor microenvironment. Using single cell sequencing, we found TGM2 levels to be elevated in certain cell populations, specifically endothelial cells and cancer cells. We discovered high TGM2 levels in TIE2-GFP mouse vessels and subsequently found high TGM2 levels in patient tumor vasculature. Further studies aim to conditionally ablate TGM2 in endothelial cells to assess its mechanistic involvement in PDAC initiation and progression. Additionally, we are studying concurrent conditional TGM2 and SMAD4 deletions in mice to investigate pancreatic cancer precursor lesion formation and are further evaluating the protective mechanisms of a TGM2 deletion in a more aggressive mouse model of PDAC. Our preliminary findings substantiate TGM2 as a critical player in PDAC pathogenesis, opening avenues for targeted therapeutics to ultimately improve patient prognosis. Citation Format: Polina Wright, Azeddine Atfi. Elucidating the role of transglutaminase 2 (TGM2) in pancreatic ductal adenocarcinoma pathogenesis and its therapeutic implications [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2896.

Clinical and Preclinical Targeting of Oncogenic Pathways in PDAC: Targeted Therapeutic Approaches for the Deadliest Cancer.

Pancreatic ductal adenocarcinoma (PDAC) is one of the leading causes of cancer-related death worldwide. It is commonly diagnosed in advanced stages and therapeutic interventions are typically constrained to systemic chemotherapy, which yields only modest clinical outcomes. In this review, we examine recent developments in targeted therapy tailored to address distinct molecular pathway alteration required for PDAC. Our review delineates the principal signaling pathways and molecular mechanisms implicated in the initiation and progression of PDAC. Subsequently, we provide an overview of prevailing guidelines, ongoing investigations, and prospective research trajectories related to targeted therapeutic interventions, drawing insights from randomized clinical trials and other pertinent studies. This review focus on a comprehensive examination of preclinical and clinical data substantiating the efficacy of these therapeutic modalities, emphasizing the potential of combinatorial regimens and novel therapies to enhance the quality of life for individuals afflicted with PDAC. Lastly, the review delves into the contemporary application and ongoing research endeavors concerning targeted therapy for PDAC. This synthesis serves to bridge the molecular elucidation of PDAC with its clinical implications, the evolution of innovative therapeutic strategies, and the changing landscape of treatment approaches.

DDX3X interacts with SIRT7 to promote PD-L1 expression to facilitate PDAC progression

Pancreatic ductal adenocarcinoma (PDAC) is recognized as the most aggressive and fatal malignancy. A previous study reported that PDAC patients who exhibit elevated levels of DDX3X have a poor prognosis and low overall survival rate. However, the underlying molecular mechanism remains unclear. This study aimed to investigate the specific roles of DDX3X in PDAC. Multiple bioinformatics analyses were used to evaluate DDX3X expression and its potential role in PDAC. In vitro and in vivo studies were performed to assess the effects of DDX3X on PDAC cell growth. Furthermore, Western blotting, quantitative PCR, immunohistochemistry, immunofluorescence, mass spectrometry, coimmunoprecipitation and multiplexed immunohistochemical staining were conducted to identify the specific regulatory mechanism in PDAC. The results verified that DDX3X expression is notably upregulated in the tumor tissue vs. normal tissue of PDAC patients. DDX3X knockdown markedly suppressed the proliferation, invasion and migration of PDAC cells in vitro and inhibited tumor growth in vivo. Conversely, overexpression of DDX3X induced the opposite effect. Further studies supported that the DDX3X protein can associate with sirtuin 7 (SIRT7) to stimulate PDAC carcinogenesis and progression. Furthermore, SIRT7 inhibition significantly impeded DDX3X-mediated tumor growth both ex vivo and in vivo. The results also revealed that programmed death ligand 1 (PD-L1) expression is positively correlated with DDX3X expression. These results reveal significant involvement of the DDX3X-SIRT7 axis in the initiation and advancement of PDAC and offer previously undiscovered therapeutic options for PDAC management.

TGFβ and Hippo Signaling Pathways Coordinate to Promote Acinar to Ductal Metaplasia in Human Pancreas.

Acinar-to-ductal metaplasia (ADM) serves as a precursor event in the development of pancreatic ductal adenocarcinoma (PDAC) upon constitutive environmental and genetical stress. While the role of ADM in PDAC progression has been established, the molecular mechanisms underlying human ADM remain elusive. We previously demonstrated the induction of ADM in human acinar cells through the transforming growth factor beta (TGFβ) signaling pathway. We aim to investigate the interaction between TGFβ and Hippo pathways in mediating ADM. RNA-sequencing was conducted on sorted normal primary human acinar, ductal, and AD (acinar cells that have undergone ADM) cells. ATAC-seq analysis was utilized to reveal the chromatin accessibility in these three cell types. ChIP-Seq of YAP1, SMAD4, and H3K27ac was performed to identify the gene targets of YAP1 and SMAD4. The role of YAP1/TAZ in ADM-driven cell proliferation, as well as in oncogenic KRAS driven proliferation, was assessed using sphere formation assay. AD cells have a unique transcription profile, with upregulated genes in open chromatin states in acinar cells. YAP1 and SMAD4 co-occupy the loci of ADM-related genes, including PROM1, HES1, and MMP7, co-regulating biological functions such as cell adhesion, cell migration, and inflammation. Overexpression of YAP1/TAZ promoted acinar cell proliferation but still required the TGFβ pathway. YAP1/TAZ were also crucial for TGFβ-induced sphere formation and were necessary for KRAS-induced proliferation. Our study reveals the intricate transition between acinar and AD states in human pancreatic tissues. It unveils the complex interaction between the Hippo and TGF-β pathways during ADM, highlighting the pivotal role of YAP1/TAZ and SMAD4 in PDAC initiation.

Abstract C080: Decoding the MYC-PDAC nexus: Unveiling the impact of PP2A-C subunit methylation on tumor onset and advancement

Abstract Introduction: Persistent disruptions in MYC regulation and the inactivation of the serine/threonine protein phosphatase 2A (PP2A) are prevalent among individuals diagnosed with pancreatic ductal adenocarcinoma (PDAC). While it is known that PP2A influences MYC activity by facilitating its degradation, the precise mechanism by which this occurs remains unclear. Small molecule activators PP2A (SMAPs) regulate the holoenzyme assembly consisting of a scaffolding-A subunit and a catalytic-C subunit, and over 40 distinct substrate directing regulatory-B subunits. PP2A heterotrimerization is regulated by post-translational modifications of the catalytic C subunit, notably methylation of L309, which impacts B subunit binding affinity to the AC dimer and thus the substrate selectivity. In this study, we aim to investigate whether the deregulation of MYC, attributed to the loss of PP2A-C subunit methylation, contributes to the initiation and progression of PDAC. Methods: We investigated the influence of SMAPs on MYC’s stability using clinical specimens, cellular, and mouse models. Clinical specimens consisted of tissue microarray (TMA) from patients with pancreatitis and PDAC. Cellular models involved ex-vivo acinar cell assays and proximity ligation assays. Mouse models included caerulein-induced pancreatitis, genetic mouse models like Ptf1a-Cre; LSL-KRASG12D (KC) and LSL-Kras G12D;P53 R172H/+;Pdx1-Cre (KPC), along with pharmacological inhibition studies with SMAPs. Results and discussion: Our TMA data revealed a consistent pattern of Methyl-PP2A-C (Methyl-C) loss and an increase in the stable and active phosphoform of MYC (p62MYC) throughout the sequential stages of PDAC progression, starting from normal tissue and advancing to acinar-to-ductal metaplasia, PanINs, and finally PDAC. In ex-vivo ADM assays, treatment with small molecule activators of PP2A (SMAPs), specifically DT061, significantly reduced the transformation of acinar cells to duct-like cells compared to untreated cells from both wild-type (WT) and KC mice. This suggests that PP2A plays a crucial role in the early events that drive the formation of pancreatic lesions. Moreover, SMAPs demonstrated the ability to alleviate caerulein-induced inflammation in normal mice, as well as suppress the development of pancreatic PanIN lesions and collagen deposition in caerulein-treated KC mice. These effects were associated with decreased levels of p62MYC and increased Methyl-C staining in both WT and KC mice treated with caerulein. Additionally, in KPC mice, treatment with DT061 resulted in reduced PDAC tumor growth, accompanied by decreased levels of p62MYC. Conclusion: Our results provide compelling evidence that small molecule activators of PP2A (SMAPs), through their ability to downregulate MYC, hold significant promise as a therapeutic strategy for individuals at high risk of developing PDAC, particularly those with chronic pancreatitis. This approach has the potential to effectively prevent PDAC development and mitigate its onset in this high-risk population. Citation Format: Vidhi Shah, Alexander Smith, Gabriel Cohn, Motoyuki Tsuda, Goutham Narla, Jonathan Brody, Brett Sheppard, Rosalie Sears. Decoding the MYC-PDAC nexus: Unveiling the impact of PP2A-C subunit methylation on tumor onset and advancement [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr C080.

Down-regulation of microRNA-23a promotes pancreatic ductal adenocarcinoma initiation and progression by up-regulation of FOXM1 expression

Transcriptional factor Forkhead box M1 (FOXM1) plays an important role in pancreatic ductal adenocarcinoma (PDAC) development and progression. The molecular mechanisms underlying its dysregulation remain unclear. We identified and functionally validated the microRNAs (miRNAs) that critically regulate FOXM1 expression in PDAC. The expression levels of miRNA-23a (miR-23a-3p and -5p) were altered in PDAC cell lines and their effects on FOXM1 signaling and cell proliferation and migration and tumorigenesis were examined in vitro and in vivo using mouse PDAC models. Compared with non-tumor pancreatic tissues, PDAC tissues and cell lines exhibited significantly reduced levels of miR-23a expression. Reduced miR-23a expression and concomitant increase in FOXM1 expression were also observed in acinar-to-ductal metaplasia and pancreatic intraepithelial neoplasia, the major premalignant lesions of PDAC. Transgenic expression of miR-23a reduced the expression of FOXM1 and suppressed cell proliferation and migration in PDAC cells, whereas the inhibitors of miR-23a did the opposite. Loss or reduced levels of miR-23a increased the levels of FOXM1 expression, while increased expression of FOXM1 down-regulated miR-23a expression, suggesting that miR-23a and FOXM1 were mutual negative regulators of their expression in PDAC cells. Therefore, the miR-23a/FOXM1 signaling axis is important in PDAC initiation and progression and could serve as an interventional or therapeutic target for patients with early or late stages of PDAC.

KRAS-Dependency in Pancreatic Ductal Adenocarcinoma: Mechanisms of Escaping in Resistance to KRAS Inhibitors and Perspectives of Therapy.

Pancreatic ductal adenocarcinoma (PDAC) is still one of the deadliest cancers in oncology because of its increasing incidence and poor survival rate. More than 90% of PDAC patients are KRAS mutated (KRASmu), with KRASG12D and KRASG12V being the most common mutations. Despite this critical role, its characteristics have made direct targeting of the RAS protein extremely difficult. KRAS regulates development, cell growth, epigenetically dysregulated differentiation, and survival in PDAC through activation of key downstream pathways, such as MAPK-ERK and PI3K-AKT-mammalian target of rapamycin (mTOR) signaling, in a KRAS-dependent manner. KRASmu induces the occurrence of acinar-to-ductal metaplasia (ADM) and pancreatic intraepithelial neoplasia (PanIN) and leads to an immunosuppressive tumor microenvironment (TME). In this context, the oncogenic mutation of KRAS induces an epigenetic program that leads to the initiation of PDAC. Several studies have identified multiple direct and indirect inhibitors of KRAS signaling. Therefore, KRAS dependency is so essential in KRASmu PDAC that cancer cells have secured several compensatory escape mechanisms to counteract the efficacy of KRAS inhibitors, such as activation of MEK/ERK signaling or YAP1 upregulation. This review will provide insights into KRAS dependency in PDAC and analyze recent data on inhibitors of KRAS signaling, focusing on how cancer cells establish compensatory escape mechanisms.

Towards a Synthesis of the Non-Genetic and Genetic Views of Cancer in Understanding Pancreatic Ductal Adenocarcinoma Initiation and Prevention.

While much of the research in oncogenesis and cancer therapy has focused on mutations in key cancer driver genes, more recent work suggests a complementary non-genetic paradigm. This paradigm focuses on how transcriptional and phenotypic heterogeneity, even in clonally derived cells, can create sub-populations associated with oncogenesis, metastasis, and therapy resistance. We discuss this complementary paradigm in the context of pancreatic ductal adenocarcinoma. A better understanding of cellular transcriptional heterogeneity and its association with oncogenesis can lead to more effective therapies that prevent tumor initiation and slow progression.

Abstract 336: Role of ST6GAL1 sialyltransferase in early stages of pancreatic cancer development

Abstract Increased cell surface sialylation is a prevalent feature of tumor cells. The addition of sialic acid (a negatively-charged sugar) to select surface receptors modulates the structure and function of these receptors, leading to changes in intracellular signaling and gene expression. Increased tumor cell sialylation occurs, in part, through the upregulation of sialyltransferases such as ST6GAL1, an enzyme that adds an α2-6 linked sialic acid to N-glycosylated proteins. ST6GAL1 is overexpressed in numerous malignancies, including pancreatic ductal adenocarcinoma (PDAC), and high expression correlates with a poor prognosis. Our group has shown that ST6GAL1 plays a causal role in promoting PDAC initiation and progression in tumor xenograft and genetically-engineered mouse (GEM) models. As one example, we developed a GEM model with conditional ST6GAL1 expression in the pancreas and crossed this line to the “KC” PDAC model, which expresses oncogenic Kras (KrasG12D). Mice with dual expression of ST6GAL1 and KrasG12D (”KSC” mice) exhibit greatly accelerated PDAC initiation, progression, and mortality when compared with KC mice. In light of ST6GAL1's known role in conferring progenitor-like cell characteristics, we postulated that ST6GAL1 activity contributes to PDAC initiation by fostering acinar to ductal metaplasia (ADM). During ADM, pancreatic acinar cells de-differentiate into ductal-like, progenitor cells and acquire greater proliferative potential as well as apoptosis resistance. Cells undergoing ADM are particularly vulnerable to Kras-dependent transformation. Using a variety of approaches and model systems including GEM organoids, 3D acinar cultures, acinar-like cell lines, and an in vivo assay for ADM, we uncovered a novel function for ST6GAL1 in promoting ADM. We further determined that high ST6GAL1 activity in acinar cells cooperates with KrasG12D to drive neoplasia. Finally, our studies suggest that the tumor-promoting effects of ST6GAL1 are mediated, at least in part, by ST6GAL1-mediated sialylation of EGFR. These collective results highlight a novel glycosylation-dependent mechanism involved in early stages of PDAC development. Citation Format: Susan L. Bellis, Asmi Chakraborty, Nikita Bhalerao, Michael Marciel, Jihye Hwang, Austin Silva. Role of ST6GAL1 sialyltransferase in early stages of pancreatic cancer development [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 336.

Abstract 4775: Knockout of Sod2 accelerates KrasG12D-driven formation of pancreatic cancerous lesions

Abstract Recent studies demonstrate that mitochondrially-generated reactive oxygen species (ROS) downstream of oncogenic KRAS drive acinar-to-ductal metaplasia (ADM), a key first step in the pancreatic ductal adenocarcinoma (PDA) progression model. MnSOD/SOD2 is a mitochondrial enzyme that converts superoxide into hydrogen peroxide. Previous studies have shown that SOD2 is biologically relevant to the study of pancreatic cancer. Some patients with a SOD2 polymorphism resulting in less active MnSOD at the mitochondrial matrix are at increased risk of developing pancreatic cancer. Additionally, MnSOD is lost in high-grade human PanIN, further suggesting a role in tumor development. To elucidate the role of MnSOD in pancreatic cancer initiation and progression, we crossed Sod2lox/lox mice into the p48Cre;LSL-KrasG12D (KC) mouse model. We found increased ROS, abundantly more abnormal tissue development and presence of flat lesions indicating accelerated early progression. However, Kaplan Meyer survival analysis of KC and KC;Sod2−/− mice did not indicate faster progression to cancer, suggesting that for later steps additional signaling is needed. In summary, we identify MnSOD as a key antioxidant molecule preventing initiation of PDA. Citation Format: Alicia K. Fleming Martinez, Brandy H. Edenfield, Irene Esposito, Peter Storz. Knockout of Sod2 accelerates KrasG12D-driven formation of pancreatic cancerous lesions. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4775.

Abstract 4779: MnSOD mimetic mitoquinone mesylate (MitoQ) increases DCLK1+pancreatic cancer stem cells

Abstract Mitochondrially-generated reactive oxygen species (mROS) have been shown to induce acinar-to-ductal metaplasia (ADM). ADM, in presence of an oncogenic KRAS mutation, is an initiating step for progression to pancreatic intraepithelial neoplasia (PanIN) and eventually pancreatic ductal adenocarcinoma (PDA). Here, we utilize primary murine cells as well as the p48Cre;LSL-KrasG12D (KC) mouse model to explore the use of the mitochondria-targeted mimetic of manganese superoxide dismutase MitoQ for targeting PDA initiation and progression. Previously published data by our laboratory has shown that treatment with MitoQ decreases the abundance of pancreatic low-grade lesions in KC mice. However, we here demonstrate that superoxide depletion by MitoQ at the same time increases formation of DCLK1+ cancer stem cells in such lesions. We here evaluate if the detoxification of mitochondrial superoxide results in a build-up of hydrogen peroxide, which is a major driver of the DCLK1+ cell type. We determine how altered expression of ROS detoxifying enzymes in different cell types contribute to PDA stem cell formation and PDA development. Eventually we test if the increase in DCLK1+ cancer stem cells can contribute to changes in the microenvironment and accelerated progression of abnormal tissue. Citation Format: Jeffrey Mario Perera, Alicia K. Fleming Martinez, Peter Storz. MnSOD mimetic mitoquinone mesylate (MitoQ) increases DCLK1+pancreatic cancer stem cells. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4779.

Targeted therapy for pancreatic ductal adenocarcinoma: Mechanisms and clinical study.

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive and lethal malignancy with a high rate of recurrence and a dismal 5-year survival rate. Contributing to the poor prognosis of PDAC is the lack of early detection, a complex network of signaling pathways and molecular mechanisms, a dense and desmoplastic stroma, and an immunosuppressive tumor microenvironment. A recent shift toward a neoadjuvant approach to treating PDAC has been sparked by the numerous benefits neoadjuvant therapy (NAT) has to offer compared with upfront surgery. However, certain aspects of NAT against PDAC, including the optimal regimen, the use of radiotherapy, and the selection of patients that would benefit from NAT, have yet to be fully elucidated. This review describes the major signaling pathways and molecular mechanisms involved in PDAC initiation and progression in addition to the immunosuppressive tumor microenvironment of PDAC. We then review current guidelines, ongoing research, and future research directions on the use of NAT based on randomized clinical trials and other studies. Finally, the current use of and research regarding targeted therapy for PDAC are examined. This review bridges the molecular understanding of PDAC with its clinical significance, development of novel therapies, and shifting directions in treatment paradigm.

Biological and Clinical Impacts of Glucose Metabolism in Pancreatic Ductal Adenocarcinoma.

Pancreatic ductal adenocarcinoma (PDAC) is a lethal cancer type as it is prone to metastases and is difficult to diagnose at an early stage. Despite advances in molecular detection, its clinical prognosis remains poor and it is expected to become the second leading cause of cancer-related deaths. Approximately 85% of patients develop glucose metabolism disorders, most commonly diabetes mellitus, within three years prior to their pancreatic cancer diagnosis. Diabetes, or glucose metabolism disorders related to PDAC, are typically associated with insulin resistance, and beta cell damage, among other factors. From the perspective of molecular regulatory mechanisms, glucose metabolism disorders are closely related to PDAC initiation and development and to late invasion and metastasis. In particular, abnormal glucose metabolism impacts the nutritional status and prognosis of patients with PDAC. Meanwhile, preliminary research has shown that metformin and statins are effective for the prevention or treatment of malignancies; however, no such effect has been shown in clinical trials. Hence, the causes underlying these conflicting results require further exploration. This review focuses on the clinical significance of glucose metabolism disorders in PDAC and the mechanisms behind this relationship, while also summarizing therapeutic approaches that target glycolysis.

Role of epigenetics in pancreatic ductal adenocarcinoma.

Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive cancers, associated with poor survival outcomes. Lack of early diagnosis, resistance to conventional therapeutic treatments (including immunotherapy) and recurrence are some of the major hurdles in PDAC and contribute to its poor survival rate. While the risk of genetic predisposition to cancers is widely acknowledged and understood, recent advances in whole-genome and next-generation sequencing techniques have led to the acknowledgment of the role played by epigenetics, especially in PDAC. Epigenetic changes are heritable genetic modifications that influence gene expression without altering the DNA sequence. Epigenetic mechanisms (e.g., DNA methylation, post-translational modification of histone complexes and ncRNA) that result in reversible changes in gene expression are increasingly understood to be responsible for tumor initiation, development and even escape from immune surveillance. Our review seeks to highlight the various components of the epigenetic machinery that are known to be implicated in PDAC initiation and development and the feasibility of targeting these components to identify novel pharmacological strategies that could potentially lead to breakthroughs in PDAC treatment.

Epigenetics in Pancreatic Ductal Adenocarcinoma: Impact on Biology and Utilization in Diagnostics and Treatment.

Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive malignancies with high potential of metastases and therapeutic resistance. Although genetic mutations drive PDAC initiation, they alone do not explain its aggressive nature. Epigenetic mechanisms, including aberrant DNA methylation and histone modifications, significantly contribute to inter- and intratumoral heterogeneity, disease progression and metastasis. Thus, increased understanding of the epigenetic landscape in PDAC could offer new potential biomarkers and tailored therapeutic approaches. In this review, we shed light on the role of epigenetic modifications in PDAC biology and on the potential clinical applications of epigenetic biomarkers in liquid biopsy. In addition, we provide an overview of clinical trials assessing epigenetically targeted treatments alone or in combination with other anticancer therapies to improve outcomes of patients with PDAC.

Targeting autophagy in pancreatic cancer: The cancer stem cell perspective.

Pancreatic cancer is currently the seventh leading cause of cancer-related deaths worldwide, with the estimated death toll approaching half a million annually. Pancreatic ductal adenocarcinoma (PDAC) is the most common (>90% of cases) and most aggressive form of pancreatic cancer, with extremely poor prognosis and very low survival rates. PDAC is initiated by genetic alterations, usually in the oncogene KRAS and tumor suppressors CDKN2A, TP53 and SMAD4, which in turn affect a number of downstream signaling pathways that regulate important cellular processes. One of the processes critically altered is autophagy, the mechanism by which cells clear away and recycle impaired or dysfunctional organelles, protein aggregates and other unwanted components, in order to achieve homeostasis. Autophagy plays conflicting roles in PDAC and has been shown to act both as a positive effector, promoting the survival of pancreatic tumor-initiating cells, and as a negative effector, increasing cytotoxicity in uncontrollably expanding cells. Recent findings have highlighted the importance of cancer stem cells in PDAC initiation, progression and metastasis. Pancreatic cancer stem cells (PaCSCs) comprise a small subpopulation of the pancreatic tumor, characterized by cellular plasticity and the ability to self-renew, and autophagy has been recognised as a key process in PaCSC maintenance and function, simultaneously suggesting new strategies to achieve their selective elimination. In this review we evaluate recent literature that links autophagy with PaCSCs and PDAC, focusing our discussion on the therapeutic implications of pharmacologically targeting autophagy in PaCSCs, as a means to treat PDAC.