Chemoresistance In Pancreatic Ductal Adenocarcinoma Research Articles

ARID3A enhances chemoresistance of pancreatic cancer via inhibiting PTEN-induced ferroptosis

Currently, chemotherapy remains occupying a pivotal place in the treatment of pancreatic ductal adenocarcinoma (PDAC). Nonetheless, the emergence of drug resistance in recent years has limited the clinical efficacy of chemotherapeutic agents, especially gemcitabine (GEM). Through bioinformatics analysis, AT-rich Interactive Domain-containing Protein 3A (ARID3A), one of transcription factors, is discovered to possibly participate in this progress. This study thoroughly investigates the potential role of ARID3A in the malignant progression and GEM chemoresistance of PDAC and explores the underlying mechanisms. The results indicate that ARID3A knockdown suppresses tumor development and enhances the sensitivity of PDAC cells to GEM in vitro and vivo. Mechanically, CUT&Tag profiling sequencing, RNA‐sequencing and functional studies demonstrates that decreased ARID3A expression alleviates the transcriptional inhibition of phosphatase and tensin homolog (PTEN), consequently leading to glutathione peroxidase 4 (GPX4) depletion and increased lipid peroxidation levels. Activated ferroptosis induced by the inhibition of GPX4 subsequently restricts tumor progression and reduces GEM resistance in PDAC. This research identifies the ferroptosis regulatory pathway of ARID3A-PTEN-GPX4 axis and reveals its critical role in driving the progression and chemoresistance of pancreatic cancer. Notably, both inhibition of ARID3A and enhancement of ferroptosis can increase chemosensitivity to GEM, which offers a promising opportunity for developing therapeutic strategies to combat acquired chemotherapy resistance in pancreatic cancer.

Cellular collusion: cracking the code of immunosuppression and chemo resistance in PDAC

Despite the efforts, pancreatic ductal adenocarcinoma (PDAC) is still highly lethal. Therapeutic challenges reside in late diagnosis and establishment of peculiar tumor microenvironment (TME) supporting tumor outgrowth. This stromal landscape is highly heterogeneous between patients and even in the same patient. The organization of functional sub-TME with different cellular compositions provides evolutive advantages and sustains therapeutic resistance. Tumor progressively establishes a TME that can suit its own needs, including proliferation, stemness and invasion. Cancer-associated fibroblasts and immune cells, the main non-neoplastic cellular TME components, follow soluble factors-mediated neoplastic instructions and synergize to promote chemoresistance and immune surveillance destruction. Unveiling heterotypic stromal-neoplastic interactions is thus pivotal to breaking this synergism and promoting the reprogramming of the TME toward an anti-tumor milieu, improving thus the efficacy of conventional and immune-based therapies. We underscore recent advances in the characterization of immune and fibroblast stromal components supporting or dampening pancreatic cancer progression, as well as novel multi-omic technologies improving the current knowledge of PDAC biology. Finally, we put into context how the clinic will translate the acquired knowledge to design new-generation clinical trials with the final aim of improving the outcome of PDAC patients.

Tumor Microenvironment Modulates Invadopodia Activity of Non-Selected and Acid-Selected Pancreatic Cancer Cells and Its Sensitivity to Gemcitabine and C18-Gemcitabine.

Pancreatic ductal adenocarcinoma (PDAC) is a deadly disease with high mortality due to early metastatic dissemination and high chemoresistance. All these factors are favored by its extracellular matrix (ECM)-rich microenvironment, which is also highly hypoxic and acidic. Gemcitabine (GEM) is still the first-line therapy in PDAC. However, it is quickly deaminated to its inactive metabolite. Several GEM prodrugs have emerged to improve its cytotoxicity. Here, we analyzed how the acidic/hypoxic tumor microenvironment (TME) affects the response of PDAC cell death and invadopodia-mediated ECM proteolysis to both GEM and its C18 prodrug. For this, two PDAC cell lines, PANC-1 and Mia PaCa-2 were adapted to pHe 6.6 or not for 1 month, grown as 3D organotypic cultures and exposed to either GEM or C18 in the presence and absence of acidosis and the hypoxia inducer, deferoxamine. We found that C18 has higher cytotoxic and anti-invadopodia activity than GEM in all culture conditions and especially in acid and hypoxic environments. We propose C18 as a more effective approach to conventional GEM in developing new therapeutic strategies overcoming PDAC chemoresistance.

Abstract 4436: Phenotypic heterogeneity in pancreatic ductal adenocarcinoma revealed by single-cell lipidomics

Abstract Introduction: The high chemoresistance of pancreatic ductal adenocarcinoma (PDAC) is partly attributed to the phenotypic plasticity and high adaptability of PDAC cells to the challenges of the harsh microenviroment. Phenotypic presentation of the PDAC cell is also determined by the lipid composition of the plasma membrane and lipid species that organize the rigid or more flexible lipid bilayer and determine the cellular mobility and plasticity. Lipids are also important energy and signaling molecules that contribute to the aggressiveness of the cell. Here we focus on differences in lipid profile of PDAC cells in epithelial and mesenchymal cell state using single-cell lipidomics approach (SpaceM). Methods: Lipid profile of 2D cultures of eight conventional and ten primary patient derived cell lines of different source (patient derived xenograft, ascites, primary tumor, organoid derived) was investigated. Epithelial (E) or mesenchymal (M) cell state was evaluated by gene and protein expression of EMT markers. Matrix-Assisted Laser Desorption/Ionization (MALDI)-imaging MS was used for data acquisition on positive ion mode at 25 µm step size and m/z range of 600-1000. For annotating lipids in MALDI-imaging data, we used the METASPACE cloud software. For constructing single-cell lipidomic profiles we used the SpaceM method. In total, around 150.000 cells were analyzed and 1400 lipid ions detected. Results: Gene expression analysis suggested prominent metabolism of structural lipids in the conventional epithelial cells. In UMAP analysis of single cell lipidomics data, each cell line, conventional and primary, presented a unique lipid fingerprint with however prominent clustering into the two phenotypes, epithelial and mesenchymal. We detected enrichment of alkyl-acyl phosphatidylcholines, alkyl-acyl phospatidylethanolamines, ceramides and sphingolipids in the epithelial phenotype. Mesenchymal phenotype was enriched for lipids involved in lateral diffusion and low bilayer thickness supporting the increased fluidity of the mesenchymal cell membrane. Furthermore, mesenchymal phenotype was enriched for lipid droplets and energy storing triacylglycerols, also confirmed by histological lipid droplet staining. Conclusions: Using the single cell lipid information, a successful grouping to epithelial or mesenchymal subtype could be performed regardless of sample source, suggesting a conserved lipid profile typical for the two states. Further detailed investigation of single cell lipidomics data aims to unveil the prominent epithelial-mesenchymal state lipid markers and open a niche for functional investigations of cell-state specific markers and potential cell-state targeting. Citation Format: Marija Trajkovic-Arsic, Jeany Delafiori, Mohammed Shahraz, Corinna Münch, Smiths S. Lueong, Sven T. Liffers, Doris Hellerschmied, Theodore Alexandrov, Jens T. Siveke. Phenotypic heterogeneity in pancreatic ductal adenocarcinoma revealed by single-cell lipidomics [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 4436.

Abstract 4613: Tumor-derived interleukin 35 facilitates the gemcitabine resistance in pancreatic adenocarcinoma by mediating the dissemination of chemoresistance among PDAC cells

Abstract Rapid drug resistance after chemotherapy is a key cause of treatment failure in human pancreatic ductal adenocarcinoma (PDAC). Here, we found that tumor-derived interleukin 35 (IL-35) mediated the rapid resistance of PDAC to gemcitabine (GEM). The role of IL-35 in GEM resistance was determined by molecular and cell biology approaches in PDAC cells and in patient-derived tumor xenograft (PDX) models. We used whole genome RNA sequencing, molecular cloning and other molecular biological methods to study the molecular mechanism of IL-35 mediated GEM resistance. An anti-IL-35 neutralizing antibody was used in mouse models to investigate the feasibility of targeting IL-35 to overcome drug resistance in pancreatic cancer. We observed the phenomenon that GEM resistance could spread from GEM resistant PDAC cells to GEM sensitive ones. The results of sequencing and experiments confirmed that the IL-35 secretion is responsible for the dissemination of chemoresistance. IL-35 secreted from GEM resistant cells activated the IL35 expression in GEM sensitive cells and upregulated SOD2 expression via GP130-STAT1 signaling, which scavenges reactive oxygen species (ROS) and then leads to GEM resistance.Furthermore, we found that a neutralizing antibody against IL-35 significantly enhanced the tumor suppressive effect of GEM. These findings collectively reveal that IL-35 plays crucial roles in mediating GEM resistance in pancreatic cancer. Moreover, IL-35 might serve as a promising therapeutic target for combating PDAC chemoresistance. Citation Format: Chongbiao Huang, Huizhi Sun, Antao Chang, Jihui Hao. Tumor-derived interleukin 35 facilitates the gemcitabine resistance in pancreatic adenocarcinoma by mediating the dissemination of chemoresistance among PDAC cells [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 4613.

Exploring the therapeutic potential of focal adhesion kinase inhibition in overcoming chemoresistance in pancreatic ductal adenocarcinoma.

Pancreatic ductal adenocarcinoma (PDAC) is among the leading causes of cancer-related deaths worldwide. Focal adhesion kinase (FAK) is a nonreceptor tyrosine kinase often overexpressed in PDAC. FAK has been linked to cell migration, survival, proliferation, angiogenesis and adhesion. This review first highlights the chemoresistant nature of PDAC. Second, the role of FAK in PDAC cancer progression and resistance is carefully described. Additionally, it discusses recent developments of FAK inhibitors as valuable drugs in the treatment of PDAC, with a focus on diamine-substituted-2,4-pyrimidine-based compounds, which represent the most potent class of FAK inhibitors in clinical trials for the treatment of PDAC disease. To conclude, relevant computational studies performed on FAK inhibitors are reported to highlight the key structural features required for interaction with the protein, with the aim of optimizing this novel targeted therapy.

Tumor-derived interleukin 35 mediates the dissemination of gemcitabine resistance in pancreatic adenocarcinoma.

Rapid development of drug resistance after chemotherapy is a major cause of treatment failure in individuals with pancreatic ductal adenocarcinoma (PDAC). In this study, we illustrate that tumor-derived interleukin 35 (IL-35) mediates the accelerated resistance of PDAC to gemcitabine (GEM). We observe that GEM resistance can spread from GEM-resistant PDAC cells to GEM-sensitive cells, and that IL-35 is responsible for the propagation of chemoresistance, which is supported by sequencing and experimental data. Additionally, we discover that GEM-resistant cells have significantly higher levels of IL-35 expression. Mechanistically, aberrantly expressed IL-35 triggers transcriptional activation of SOD2 expression via GP130-STAT1 signaling, scavenging reactive oxygen species (ROS) and leading to GEM resistance. Furthermore, GEM treatment stimulates IL-35 expression through activation of the NF-κB pathway, resulting in acquired chemoresistance. In the mouse model, a neutralizing antibody against IL-35 enhances the tumor suppressive effect of GEM. Collectively, our data suggests that IL-35 is critical in mediating GEM resistance in pancreatic cancer, and therefore could be a valuable therapeutic target in overcoming PDAC chemoresistance.

Abstract B085: K17-induced pyrimidine biosynthesis drives chemoresistance in PDAC

Abstract Background: The 5-year survival rate of pancreatic cancer is extremely low compared with other cancers, although it has increased to 12% in 2023 in the United States. 80% of pancreatic ductal adenocarcinoma (PDAC) patients are not eligible for surgical procedure, and unfortunately, PDAC is refractory to standard-of-care chemotherapy. Thus, developing novel and more effective treatment strategies for PDAC is urgently needed. We previously reported keratin 17 (K17) as a novel negative prognostic and predictive biomarker, whose overexpression confers the resistance to chemotherapies. Here, we investigated the mechanisms of chemoresistance and tumor-specific vulnerabilities that can be exploited for K17-mediated targeted therapies. Methods: Survival analyses, immunohistochemistry (IHC), and matrix assisted laser desorption/ionization mass spectrometry (MALDI MSI) metabolite imaging were applied in patient derived samples. The K17 stable expression cell line models (KPC and PANC-1) and K17 loss-of-function cell line model (L3.6) were generated, where the analyses were applied including western blots, qRT-PCR, mass spectrometric metabolomics analysis, immunofluorescence imaging, cell viability and proliferation assays. KPC cells with or without K17 expression were orthotopically implanted into the head of the pancreas of c57B6J mice for tumor growth and treatment study. Results: Unbiased metabolomic studies in isogenic PDAC models identified several key metabolic pathways that are upregulated in the presence of K17. We demonstrate that K17 increases pyrimidine biosynthesis, a pathway that drives chemoresistance. Patient dataset analysis revealed that K17 expression and enzymes involved in pyrimidine, but not purine, de novo biosynthesis is associated with shorter patient survival. Furthermore, K17-expressing cells were more sensitive to Brequinar, a specific inhibitor of dihydroorotate dehydrogenase (DHODH), the rate-limiting enzyme in de novo pyrimidine biosynthetic pathway. Targeting DHODH by small interfering RNA or by Brequinar with Gemcitabine synergistically inhibited the viability of K17- positive cells. Importantly, the combination of Gemcitabine and Brequinar significantly inhibited the growth of K17-expressing tumors and extended survival of mice bearing K17-positive tumors. Mechanistically, K17 increased mitochondrial DHODH translocation which made these cells more sensitive to Brequinar. We also found that the coil 2 domain of K17 was crucial for triggering metabolic reprogramming and promoting tumor aggression. Conclusions: Overall, we define a novel connection between K17, nucleotide metabolism, and chemoresistance in PDAC. We report for the first time that K17, a negative biomarker of the most aggressive PDAC subtype, drives chemoresistance by up-regulating de novo pyrimidine biosynthesis, which provides a tumor-specific vulnerability: DHODH. Further study could lead to the development of a DHODH targeted therapy for K17-expressing PDAC. Citation Format: Yinghuan Lyu, Kenneth Shroyer, Chun-Hao Pan, Robert Tseng, Md Afjalus Siraj, Girish Halemirle Rajacharya, Bo Chen, Katie L Donnelly, Michael Horowitz, Carlos Mauricio Mejia Arbelaez, Sumedha Chowdhury, Lyanne Oblein, Natalia Marchenko, Luisa Escobar-Hoyos, Pankaj K. Singh. K17-induced pyrimidine biosynthesis drives chemoresistance in PDAC [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 B085.

Extracellular vesicle-packaged circBIRC6 from cancer-associated fibroblasts induce platinum resistance via SUMOylation modulation in pancreatic cancer

BackgroundCancer-associated fibroblasts (CAFs) play pivotal roles in chemoresistance of pancreatic ductal adenocarcinoma (PDAC). However, the underlying mechanisms are poorly understood. Revealing the cross-talk network between tumor stroma and pancreatic cancer and developing effective strategies against oxaliplatin resistance are highly desired in the clinic.MethodsHigh-throughput sequence was used to screened the key circRNAs transmitted by extracellular vesicles (EVs) from CAFs to pancreatic cancer cells. The associations between EV-packaged circBIRC6 and chemotherapy responsiveness were validated in a cohort of 82 cases of advanced PDAC patients. Then, the effects of EV-packaged circBIRC6 on CAF-induced oxaliplatin resistance were investigated by flow cytometry, colony formation, viability of pancreatic cancer organoids in vitro and by xenograft models in vivo. RNA pulldown, RNA immunoprecipitation, and sites mutation assays were used to reveal the underlying mechanism.ResultsWe identified a circRNA, circBIRC6, is significantly upregulated in CAF-derived EVs and is positively associated with oxaliplatin-based chemoresistance. In vitro and in vivo functional assays showed that CAF-derived EV-packaged circBIRC6 enhance oxaliplatin resistance of pancreatic cancer cells and organoids via regulating the non-homologous end joining (NHEJ) dependent DNA repair. Mechanistically, circBIRC6 directly binds with XRCC4 and enhanced the interaction of XRCC4 with SUMO1 at the lysine 115 residue, which facilitated XRCC4 chromatin localization. XRCC4K115R mutation dramatically abrogated the EV-packaged circBIRC6 induced effect. Moreover, combination of antisense oligonucleotide inhibitors against circBIRC6 with Olaparib dramatically suppressed chemoresistance in patient-derived xenograft models.ConclusionsOur study revealed that EV-packaged circBIRC6 confer oxaliplatin resistance in PDAC by mediating SUMOylation of XRCC4, introducing a promising predictive and therapeutic target for PDAC on oxaliplatin resistance.

Knockdown of TACC3 inhibits tumor cell proliferation and increases chemosensitivity in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is a highly malignant digestive tract tumor with limited clinical treatments. Transforming acidic coiled-coil-containing protein 3 (TACC3) is a component of the centrosome axis and a member of the TACC family, which affect mitosis and regulate chromosome stability and are involved in tumor development and progression. However, the role of TACC3 in PDAC remains elusive. In this study, by exploiting the TCGA database, we found that high TACC3 expression in PDAC is associated with poor prognosis. shRNA-mediated TACC3 knockdown caused S phase arrest of the cell cycle and inhibited proliferation in PDAC cell lines. Through RNA sequencing and protein co-immunoprecipitation combined with mass spectrometry, KIF11 was identified as a protein that interacts with TACC3. TACC3 stabilizes and regulates KIF11 protein expression levels in PDAC cells through physical interaction. Knockdown of TACC3 or KIF11 resulted in abnormal spindle formation during cell division both in vitro and in vivo. Pharmacological inhibition of TACC3 or KIF11 can suppress tumor cell proliferation and promote apoptosis. Our studies further demonstrated that high expression of TACC3 and KIF11 mediated the resistance of PDAC to gemcitabine, and deficiency of TACC3 or KIF11 increased the sensitivity of PDAC cells to chemotherapy. In conclusion, our study reveals the fundamental role of TACC3 expression in PDAC cell proliferation and chemoresistance, suggesting that TACC3 can be used as a molecular marker to evaluate the prognosis of PDAC.

Increased mitochondria are responsible for the acquisition of gemcitabine resistance in pancreatic cancer cell lines.

Pancreatic ductal adenocarcinoma has a particularly poor prognosis as it is often detected at an advanced stage and acquires resistance to chemotherapy early during its course. Stress adaptations by mitochondria, such as metabolic plasticity and regulation of apoptosis, promote cancer cell survival; however, the relationship between mitochondrial dynamics and chemoresistance in pancreatic ductal adenocarcinoma remains unclear. We here established human pancreatic cancer cell lines resistant to gemcitabine from MIA PaCa-2 and Panc1 cells. We compared the cells before and after the acquisition of gemcitabine resistance to investigate the mitochondrial dynamics and protein expression that contribute to this resistance. The mitochondrial number increased in gemcitabine-resistant cells after resistance acquisition, accompanied by a decrease in mitochondrial fission 1 protein, which induces peripheral mitosis, leading to mitophagy. An increase in the number of mitochondria promoted oxidative phosphorylation and increased anti-apoptotic protein expression. Additionally, enhanced oxidative phosphorylation decreased the AMP/ATP ratio and suppressed AMPK activity, resulting in the activation of the HSF1-heat shock protein pathway, which is required for environmental stress tolerance. Synergistic effects observed with BCL2 family or HSF1 inhibition in combination with gemcitabine suggested that the upregulated expression of apoptosis-related proteins caused by the mitochondrial increase may contribute to gemcitabine resistance. The combination of gemcitabine with BCL2 or HSF1 inhibitors may represent a new therapeutic strategy for the treatment of acquired gemcitabine resistance in pancreatic ductal adenocarcinoma.

AKR7A3 modulates the metastasis of pancreatic ductal adenocarcinoma through regulating PHGDH-suppressed autophagy.

AKR7A3 is a member of Aldo-Keto Reductase(AKR) protein family whose primary purpose is to reduce aldehydes and ketones to generate primary and secondary alcohols. It has been reported that AKR7A3 is downregulated in pancreatic cancer (PC). However, the mechanism underlying the effects of AKR7A3 in PC remains largely unclarified. Here, we explored the biological function, molecular mechanism and clinical relevance of AKR7A3 in pancreatic ductal adenocarcinoma (PDAC). AKR7A3 expression was downregulated in PDAC compared to adjacent normal tissues, and the lower AKR7A3 expression was related to poor prognosis. In addition, our results demonstrated that AKR7A3 could be a potential diagnostic marker for PDAC, especially in the early stages. Knockdown of AKR7A3 promoted PDAC progression and chemoresistance, while inhibiting the autophagy flux. Mechanistically, AKR7A3 affected the metastatic, autophagy and chemoresistance of PDAC by regulating PHGDH. Overall, the present study suggests that AKR7A3 inhibits PDAC progression by regulating PHGDH-induced autophagy. In addition, AKR7A3 inhibits chemoresistance via regulating PHGDH, and may serve as a new therapeutic target for PDAC.

PDAC, the Influencer Cancer: Cross-Talk with Tumor Microenvironment and Connected Potential Therapy Strategies.

Pancreatic ductal adenocarcinoma (PDAC) is among the leading causes of death by cancer in the world. What makes this pathological condition particularly lethal is a combination of clinical and molecular heterogeneity, lack of early diagnostic indexes, and underwhelming results from current therapeutic protocols. A major cause of PDAC chemoresistance seems to lie in the ability of cancer cells to spread out and fill the pancreatic parenchyma, exchanging nutrients, substrates, and even genetic material with cells from the surrounding tumor microenvironment (TME). Several components can be found in the TME ultrastructure, including collagen fibers, cancer-associated fibroblasts, macrophages, neutrophils, mast cells, and lymphocytes. Cross-talk between PDAC and TME cells results in the latter being converted into cancer-favoring phenotypes; this behavior could be compared to an influencer guiding followers into supporting his activity. Moreover, TME could be a potential target for some of the newest therapeutic strategies; these include the use of pegvorhyaluronidase-α and CAR-T lymphocytes against HER2, FAP, CEA, MLSN, PSCA, and CD133. Other experimental therapy options are being currently studied, aiming to interfere with the KRAS pathway, DNA-repairing proteins, and apoptosis resistance in PDAC cells. Hopefully these new approaches will grant better clinical outcomes in future patients.

Microbiota-Derived Tryptophan Metabolite Indole-3-Acetic Acid Improves Chemoresistance in Pancreatic Ductal Adenocarcinoma.

Microbiota-Derived Tryptophan Metabolite Indole-3-Acetic Acid Improves Chemoresistance in Pancreatic Ductal Adenocarcinoma.

Chemotherapeutic drugs-induced pyroptosis mediated by gasdermin E promotes the progression and chemoresistance of pancreatic cancer

Pyroptosis is closely associated with cancer development; however, the role of pyroptosis in pancreatic ductal adenocarcinoma (PDAC), a fatal malignant tumour with a poor overall survival rate, remains elusive. Here, we explored the mechanism of chemotherapy-induced pyroptosis and elucidated the role of pyroptosis in mediating PDAC progression and chemoresistance. The results demonstrated first- and second-line chemotherapeutic drugs against PDAC, including gemcitabine, irinotecan, 5-fluorouracil, paclitaxel, and cisplatin, induced concurrent pyroptosis and apoptosis. During this process, gasdermin E (GSDME) was cleaved by activated caspase-3, which was accompanied by pro-apoptotic caspase-7/8 activation. GSDME knockdown switched pyroptosis to apoptosis, decreased invasion and migration, and enhanced the sensitivity of PDAC cells to chemotherapy in vitro and in vivo. GSDME was highly expressed in PDAC tissues and positively correlated with histological differentiation and vascular invasion. Furthermore, cells that survived pyroptosis promoted proliferation and invasion and impaired the chemosensitivity of PDAC cells, which was attenuated by the GSDME knockdown. Our findings demonstrated that chemotherapeutics against PDAC induce GSDME-dependent pyroptosis, and GSDME expression positively correlated with PDAC progression and chemoresistance. Targeting GSDME may be a novel approach to overcoming chemoresistance in PDAC.

Lauric Acid Overcomes Hypoxia-Induced Gemcitabine Chemoresistance in Pancreatic Ductal Adenocarcinoma.

Although gemcitabine (GEM) is widely used in chemotherapy for pancreatic ductal adenocarcinoma (PDA), drug resistance restricts its clinical effectiveness. To examine the mechanism of GEM resistance, we established two GEM-resistant cell lines from human PDA cells by continuous treatment with GEM and CoCl2-induced chemical hypoxia. One resistant cell line possessed reduced energy production and decreased mitochondrial reactive oxygen species levels, while the other resistant cell line possessed increased stemness. In both cell lines, ethidium bromide-stained mitochondrial DNA levels decreased, suggesting mitochondrial DNA damage. Inhibition of hypoxia-inducible factor-1α in both cell lines did not restore the GEM sensitivity. In contrast, treatment of both cell types with lauric acid (LAA), a medium-chain fatty acid, restored GEM sensitivity. These results suggest that decreased energy production, decreased mitochondrial reactive oxygen species levels, and increased stemness associated with mitochondrial damage caused by GEM lead to GEM resistance, and that hypoxia may promote this process. Furthermore, forced activation of oxidative phosphorylation by LAA could be a tool to overcome GEM resistance. Clinical verification of the effectiveness of LAA in GEM resistance is necessary in the future.

Cancer-associated fibroblasts suppress ferroptosis and induce gemcitabine resistance in pancreatic cancer cells by secreting exosome-derived ACSL4-targeting miRNAs

BackgroundPancreatic cancer continues to be one of the world's most lethal cancers. Chemotherapy resistance in patients with advanced pancreatic cancer often accompany with dismal prognosis, highlighting the need to investigate mechanisms of drug resistance and develop therapies to overcome chemoresistance. MethodsThis research was filed with the Chinese Clinical Trial Registry (ChiCTR2200061320). In order to isolate primary normal fibroblasts (NFs) and cancer-associated fibroblasts (CAFs) samples of pancreatic ductal adenocarcinoma (PDAC) and paracancerous pancreatic tissue from individuals diagnosed with PDAC were obtained. The exosomes were obtained using ultracentrifugation, and their characteristics were determined by Western blotting, nanoparticle tracking analysis, and transmission electron microscopy. CAF-derived miRNAs were analyzed by RT-qPCR and high-throughput sequencing. Gemcitabine (GEM) was employed to promote ferroptosis, and ferroptosis levels were determined by monitoring lipid reactive oxygen species (ROS), cell survival, and intracellular Fe2+ concentrations. To assess in vivo tumor response to GEM therapy, a xenograft tumor mouse model was utilized. ResultsExosomes derived from CAFs in PDAC did not exhibit innate GEM resistance. CAFs promoted chemoresistance in PDAC cells following GEM treatment by secreting exosomes, and maintaining signaling communication with cancer cells. Mechanistically, miR-3173–5p derived from CAF exosomes sponged ACSL4 and inhibited ferroptosis after uptake by cancer cells. ConclusionThis work demonstrates a novel mode of acquired chemoresistance in PDAC and identifies the miR-3173–5p/ACSL4 pathway as a promising treatment target for GEM-resistant pancreatic cancer.

Chemoresistance in pancreatic ductal adenocarcinoma: Overcoming resistance to therapy.

Pancreatic ductal adenocarcinoma (PDAC), a prominent cause of cancer deaths worldwide, is a highly aggressive cancer most frequently detected at an advanced stage that limits treatment options to systemic chemotherapy, which has provided only marginal positive clinical outcomes. More than 90% of patients with PDAC die within a year of being diagnosed. PDAC is increasing at a rate of 0.5-1.0% per year, and it is expected to be the second leading cause of cancer-related mortality by 2030. The resistance of tumor cells to chemotherapeutic drugs, which can be innate or acquired, is the primary factor contributing to the ineffectiveness of cancer treatments. Although many PDAC patients initially responds to standard of care (SOC) drugs they soon develop resistance caused partly by the substantial cellular heterogeneity seen in PDAC tissue and the tumor microenvironment (TME), which are considered key factors contributing to resistance to therapy. A deeper understanding of molecular mechanisms involved in PDAC progression and metastasis development, and the interplay of the TME in all these processes is essential to better comprehend the etiology and pathobiology of chemoresistance observed in PDAC. Recent research has recognized new therapeutic targets ushering in the development of innovative combinatorial therapies as well as enhancing our comprehension of several different cell death pathways. These approaches facilitate the lowering of the therapeutic threshold; however, the possibility of subsequent resistance development still remains a key issue and concern. Discoveries, that can target PDAC resistance, either alone or in combination, have the potential to serve as the foundation for future treatments that are effective without posing undue health risks. In this chapter, we discuss potential causes of PDAC chemoresistance and approaches for combating chemoresistance by targeting different pathways and different cellular functions associated with and mediating resistance.

Matrix stiffness triggers chemoresistance through elevated autophagy in pancreatic ductal adenocarcinoma.

Pancreatic ductal adenocarcinoma (PDAC) has a signature of extremely high matrix stiffness caused by a special desmoplastic reaction, which dynamically stiffens along with the pathological process. The poor prognosis and low five-year survival rate of PDAC are partly owing to chemoresistance triggered by substrate stiffness. Understanding the potential mechanisms of matrix stiffness causing PDAC chemoresistance is of great significance. In this study, methacrylated gelatin hydrogel was used as platform for PANC-1 and MIA-PaCa2 cell culture. The results indicated that compared to soft substrate, stiff substrate distinctively reduced the gemcitabine sensitivity of pancreatic cancer. Intriguingly, transmission electron microscopy, immunofluorescence staining, western blot and qRT-PCR assay showcased that the number of autophagosomes and the expression of LC3 were elevated. The observations indicate that matrix stiffness may regulate the autophagy level, which plays a vital role during chemoresistance. In brief, soft substrate exhibited low autophagy level, while the counterpart displayed elevated autophagy level. In order to elucidate the underlying interaction between matrix stiffness-mediated cell autophagy and chemoresistance, rescue experiments with rapamycin and chloroquine were conducted. We found that inhibiting cell autophagy dramatically increased the sensitivity of pancreatic cancer cells to gemcitabine in the stiff group, while promoting autophagy-driven chemoresistance in the soft group, demonstrating that matrix stiffness modulated chemoresistance via autophagy. Furthermore, RNA-seq results showed that miR-1972 may regulate autophagy level in response to matrix stiffness. Overall, our research shed light on the synergistic therapy of PDAC combined with gemcitabine and chloroquine, which is conducive to promoting a therapeutic effect.

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.