Challenges in Ras therapeutics in pancreatic cancer

Pancreatic Cancer: Pathogenesis and Clinical Studies

Pancreatic cancer (PC) is a highly lethal malignancy, with pancreatic ductal adenocarcinoma (PDAC) being the most common and aggressive subtype, characterized by late diagnosis, aggressive progression, and resistance to conventional therapies. Despite advances in understanding its pathogenesis, including the identification of common genetic mutations (e.g., KRAS, TP53, CDKN2A, SMAD4) and dysregulated signaling pathways (e.g., KRAS-MAPK, PI3K-AKT, and TGF-β pathways), effective therapeutic strategies remain limited. Current treatment modalities including chemotherapy, targeted therapy, immunotherapy, radiotherapy, and emerging therapies such as antibody-drug conjugates (ADCs), chimeric antigen receptor T (CAR-T) cells, oncolytic viruses (OVs), cancer vaccines, and bispecific antibodies (BsAbs), face significant challenges. This review comprehensively summarizes these treatment approaches, emphasizing their mechanisms, limitations, and potential solutions, to overcome these bottlenecks. By integrating recent advancements and outlining critical challenges, this review aims to provide insights into future directions and guide the development of more effective treatment strategies for PC, with a specific focus on PDAC. Our work underscores the urgency of addressing the unmet needs in PDAC therapy and highlights promising areas for innovation in this field.

Structural insights, regulation, and recent advances of RAS inhibitors in the MAPK signaling cascade: a medicinal chemistry perspective

The MAPK pathway has four main components: RAS, RAF, MEK, and ERK. Among these, RAS is the most frequently mutated protein and the leading cause of cancer. The three isoforms of the RAS gene are HRAS, NRAS, and KRAS. The KRAS gene is characterized by two splice variants, K-Ras4A and K-Ras4B. The occurrence of cancer often involves a mutation in both KRAS4A and KRAS4B. In this study, we have elucidated the mechanism of the RAS protein complex and the movement of switches I and II. Only two RAS inhibitors, sotorasib and adagrasib, have been approved by the FDA, and several are in clinical trials. This review comprises recent developments in synthetic RAS inhibitors, their unique properties, their importance in inhibiting RAS mutations, and the current challenges in developing new RAS inhibitors. This review will undoubtedly help researchers design novel RAS inhibitors.

Triple Blockade of Oncogenic RAS Signaling Using KRAS and MEK Inhibitors in Combination with Irradiation in Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest of human malignancies and carries an exceptionally poor prognosis. It is mostly driven by multiple oncogenic alterations, with the highest mutation frequency being observed in the KRAS gene, which is a key oncogenic driver of tumorogenesis and malignant progression in PDAC. However, KRAS remained undruggable for decades until the emergence of G12C mutation specific KRAS inhibitors. Despite this development, this therapeutic approach to target KRAS directly is not routinely used for PDAC patients, with the reasons being the rare presence of G12C mutation in PDAC with only 1-2% of occurring cases, modest therapeutic efficacy, activation of compensatory pathways leading to cell resistance, and absence of effective KRASG12D or pan-KRAS inhibitors. Additionally, indirect approaches to targeting KRAS through upstream and downstream regulators or effectors were also found to be either ineffective or known to cause major toxicities. For this reason, new and more effective treatment strategies that combine different therapeutic modalities aiming at achieving synergism and minimizing intrinsic or adaptive resistance mechanisms are required. In the current work presented here, pancreatic cancer cell lines with oncogenic KRAS G12C, G12D, or wild-type KRAS were treated with specific KRAS or SOS1/2 inhibitors, and therapeutic synergisms with concomitant MEK inhibition and irradiation were systematically evaluated by means of cell viability, 2D-clonogenic, 3D-anchorage independent soft agar, and bioluminescent ATP assays. Underlying pathophysiological mechanisms were examined by using Western blot analyses, apoptosis assay, and RAS activation assay.

Glutamine addiction and therapeutic strategies in pancreatic cancer

Pancreatic cancer remains one of the most lethal diseases worldwide owing to its late diagnosis, early metastasis, and poor prognosis. Because current therapeutic options are limited, there is an urgent need to investigate novel targeted treatment strategies. Pancreatic cancer faces significant metabolic challenges, principally hypoxia and nutrient deprivation, due to specific microenvironmental constraints, including an extensive desmoplastic stromal reaction. Pancreatic cancer cells have been shown to rewire their metabolism and energy production networks to support rapid survival and proliferation. Increased glucose uptake and glycolytic pathway activity during this process have been extensively described. However, growing evidence suggests that pancreatic cancer cells are glutamine addicted. As a nitrogen source, glutamine directly (or indirectly via glutamate conversion) contributes to many anabolic processes in pancreatic cancer, including amino acids, nucleobases, and hexosamine biosynthesis. It also plays an important role in redox homeostasis, and when converted to α-ketoglutarate, glutamine serves as an energy and anaplerotic carbon source, replenishing the tricarboxylic acid cycle intermediates. The present study aims to provide a comprehensive overview of glutamine metabolic reprogramming in pancreatic cancer, focusing on potential therapeutic approaches targeting glutamine metabolism in pancreatic cancer.

Deoxyribonucleic acid methylation driven aberrations in pancreatic cancer-related pathways

Pancreatic cancer (PanCa) presents a catastrophic disease with poor overall survival at advanced stages, with immediate requirement of new and effective treatment options. Besides genetic mutations, epigenetic dysregulation of signaling pathway-associated enriched genes are considered as novel therapeutic target. Mechanisms beneath the deoxyribonucleic acid methylation and its utility in developing of epi-drugs in PanCa are under trails. Combinations of epigenetic medicines with conventional cytotoxic treatments or targeted therapy are promising options to improving the dismal response and survival rate of PanCa patients. Recent studies have identified potentially valid pathways that support the prediction that future PanCa clinical trials will include vigorous testing of epigenomic therapies. Epigenetics thus promises to generate a significant amount of new knowledge of biological and medical importance. Our review could identify various components of epigenetic mechanisms known to be involved in the initiation and development of pancreatic ductal adenocarcinoma and related precancerous lesions, and novel pharmacological strategies that target these components could potentially lead to breakthroughs. We aim to highlight the possibilities that exist and the potential therapeutic interventions.

Chromatin accessibility uncovers KRAS-driven FOSL2 promoting pancreatic ductal adenocarcinoma progression through up-regulation of CCL28

BACKGROUND

The epigenetic mechanisms involved in the progression of pancreatic ductal adenocarcinoma (PDAC) remain largely unexplored. This study aimed to identify key transcription factors (TFs) through multiomics sequencing to investigate the molecular mechanisms of TFs that play critical roles in PDAC.

METHODS

To characterise the epigenetic landscape of genetically engineered mouse models (GEMMs) of PDAC with or without KRAS and/or TP53 mutations, we employed ATAC-seq, H3K27ac ChIP-seq, and RNA-seq. The effect of Fos-like antigen 2 (FOSL2) on survival was assessed using the Kaplan-Meier method and multivariate Cox regression analysis for PDAC patients. To study the potential targets of FOSL2, we performed Cleavage Under Targets and Tagmentation (CUT&Tag). To explore the functions and underlying mechanisms of FOSL2 in PDAC progression, we employed several assays, including CCK8, transwell migration and invasion, RT-qPCR, Western blotting analysis, IHC, ChIP-qPCR, dual-luciferase reporter, and xenograft models.

RESULTS

Our findings indicated that epigenetic changes played a role in immunosuppressed signalling during PDAC progression. Moreover, we identified FOSL2 as a critical regulator that was up-regulated in PDAC and associated with poor prognosis in patients. FOSL2 promoted cell proliferation, migration, and invasion. Importantly, our research revealed that FOSL2 acted as a downstream target of the KRAS/MAPK pathway and recruited regulatory T (Treg) cells by transcriptionally activating C-C motif chemokine ligand 28 (CCL28). This discovery highlighted the role of an immunosuppressed regulatory axis involving KRAS/MAPK-FOSL2-CCL28-Treg cells in the development of PDAC.

CONCLUSION

Our study uncovered that KRAS-driven FOSL2 promoted PDAC progression by transcriptionally activating CCL28, revealing an immunosuppressive role for FOSL2 in PDAC.

Extracellular Vesicles Derived from Human Umbilical Cord Mesenchymal Stromal Cells as an Efficient Nanocarrier to Deliver siRNA or Drug to Pancreatic Cancer Cells

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal cancers worldwide. Treatment of PDAC remains a major challenge. This study aims to evaluate, in vitro, the use of human umbilical cord mesenchymal stromal cell (UC-MSC)-derived EVs to specifically target pancreatic cancer cells. EVs were isolated from the FBS-free supernatants of the cultured UC-MSCs by ultracentrifugation and characterized by several methods. EVs were loaded with scramble or KRAS^G12D-targeting siRNA by electroporation. The effects of control and loaded EVs on different cell types were evaluated by assessing cell proliferation, viability, apoptosis and migration. Later, the ability of EVs to function as a drug delivery system for doxorubicin (DOXO), a chemotherapeutic drug, was also evaluated. Loaded EVs exhibited different kinetic rates of uptake by three cell lines, namely, BxPC-3 cells (pancreatic cancer cell line expressing KRAS^wt), LS180 cells (colorectal cell line expressing KRAS^G12D) and PANC-1 cells (pancreatic cell line expressing KRAS^G12D). A significant decrease in the relative expression of the KRAS^G12D gene after incubation with KRAS siRNA EVs was observed by real-time PCR. KRAS^G12D siRNA EVs significantly reduced the proliferation, viability and migration of the KRAS^G12D cell lines compared to scramble siRNA EVs. An endogenous EV production method was applied to obtain DOXO-loaded EVs. Briefly, UC-MSCs were treated with DOXO. After 24 h, UC-MSCs released DOXO-loaded EVs. DOXO-loaded EVs were rapidly taken up by PANC-1 cells and induced apoptotic cell death more efficiently than free DOXO. In conclusion, the use of UC-MSC-derived EVs as a drug delivery system for siRNAs or drugs could be a promising approach for the targeted treatment of PDAC.

KRAS mutation: The booster of pancreatic ductal adenocarcinoma transformation and progression

Pancreatic ductal adenocarcinoma (PDAC) is the most common type of pancreatic cancer. It has a poor response to conventional therapy and has an extremely poor 5-year survival rate. PDAC is driven by multiple oncogene mutations, with the highest mutation frequency being observed in KRAS. The KRAS protein, which binds to GTP, has phosphokinase activity, which further activates downstream effectors. KRAS mutation contributes to cancer cell proliferation, metabolic reprogramming, immune escape, and therapy resistance in PDAC, acting as a critical driver of the disease. Thus, KRAS mutation is positively associated with poorer prognosis in pancreatic cancer patients. This review focus on the KRAS mutation patterns in PDAC, and further emphases its role in signal transduction, metabolic reprogramming, therapy resistance and prognosis, hoping to provide KRAS target therapy strategies for PDAC.

Recent Advances in Well-Designed Therapeutic Nanosystems for the Pancreatic Ductal Adenocarcinoma Treatment Dilemma

Pancreatic ductal adenocarcinoma (PDAC) is a highly malignant tumor with an extremely poor prognosis and low survival rate. Due to its inconspicuous symptoms, PDAC is difficult to diagnose early. Most patients are diagnosed in the middle and late stages, losing the opportunity for surgery. Chemotherapy is the main treatment in clinical practice and improves the survival of patients to some extent. However, the improved prognosis is associated with higher side effects, and the overall prognosis is far from satisfactory. In addition to resistance to chemotherapy, PDAC is significantly resistant to targeted therapy and immunotherapy. The failure of multiple treatment modalities indicates great dilemmas in treating PDAC, including high molecular heterogeneity, high drug resistance, an immunosuppressive microenvironment, and a dense matrix. Nanomedicine shows great potential to overcome the therapeutic barriers of PDAC. Through the careful design and rational modification of nanomaterials, multifunctional intelligent nanosystems can be obtained. These nanosystems can adapt to the environment's needs and compensate for conventional treatments' shortcomings. This review is focused on recent advances in the use of well-designed nanosystems in different therapeutic modalities to overcome the PDAC treatment dilemma, including a variety of novel therapeutic modalities. Finally, these nanosystems' bottlenecks in treating PDAC and the prospect of future clinical translation are briefly discussed.

Arsenic trioxide sensitizes pancreatic cancer cells to gemcitabine through downregulation of the TIMP1/PI3K/AKT/mTOR axis

Gemcitabine (GEM) is the first-line medication for pancreatic ductal adenocarcinoma (PDAC). However, over some treatment cycles, GEM sensitivity declines and chemotherapeutic resistance develops, resulting in tumor recurrence and metastasis. Therefore, it is critical to elucidate the mechanism of GEM chemoresistance. And a specific drug that is closely related to the mechanism is urgently required to sensitize GEM. Here, tissue inhibitor of matrix metalloproteinases 1 (TIMP1) and phosphorylated mammalian target of rapamycin (p-mTOR) were found to be substantially elevated in PDAC patients and were associated with worse overall survival. The TIMP1/PI3K/AKT/mTOR pathway was found in GEM-resistant PDAC cells and was revealed to be involved in epithelial-mesenchymal transition (EMT) and apoptosis. Furthermore, arsenic trioxide (ATO), a basic therapeutic drug for acute promyelocytic leukemia, mediated TIMP1 reduction by inducing reactive oxygen species generation and hampered the subsequent PI3K/AKT/mTOR axis. Moreover, the combination of ATO and GEM cooperatively suppressed the TIMP1/PI3K/AKT/mTOR pathway, synergistically inhibited EMT and promoted apoptosis. In vitro and in vivo, ATO combined with GEM has a collaborative anticancer effect, inhibiting cancer cell proliferation, migration, invasion, and suppressing tumor growth both in PDAC parental and GEM-resistant cells. Overall, the TIMP1/PI3K/AKT/mTOR pathway is present in PDAC and linked to GEM resistance. ATO suppresses the axis to sensitize GEM and reverse GEM resistance, suggesting a promising treatment for the disease.

Therapeutic advances in metastatic pancreatic cancer: a focus on targeted therapies

Mortality from pancreatic ductal adenocarcinoma (PDAC) is increasing worldwide and effective new treatments are urgently needed. The current treatment of metastatic PDAC in fit patients is based on two chemotherapy combinations (FOLFIRINOX and gemcitabine plus nab-paclitaxel) which were validated more than 8 years ago. Although almost all treatments targeting specific molecular alterations have failed so far when administered to unselected patients, encouraging results were observed in the small subpopulations of patients with germline BRCA 1/2 mutations, and somatic gene fusions (neurotrophic tyrosine receptor kinase, Neuregulin 1, which are enriched in KRAS wild-type PDAC), KRAS G12C mutations, or microsatellite instability. While targeted tumor metabolism therapies and immunotherapy have been disappointing, they are still under investigation in combination with other drugs. Optimizing pharmacokinetics and adapting available chemotherapies based on molecular signatures are other promising avenues of research. This review evaluates the current expectations and limits of available treatments and analyses the existing trials. A permanent search for actionable vulnerabilities in PDAC tumor cells and microenvironments will probably result in a more personalized therapeutic approach, keeping in mind that supportive care must also play a major role if real clinical efficacy is to be achieved in these patients.

Synergistic Antitumoral Effect of Epigenetic Inhibitors and Gemcitabine in Pancreatic Cancer Cells

Epigenetic modifications could drive some of the molecular events implicated in proliferation, drug resistance and metastasis of pancreatic ductal adenocarcinoma (PDAC). Thus, epigenetic enzyme inhibitors could be the key to revert those events and transform PDAC into a drug-sensitive tumor. We performed a systematic study with five different epigenetic enzyme inhibitors (1, UVI5008, MS275, psammaplin A, and BIX01294) targeting either Histone Deacetylase (HDAC) 1 or 1/4, DNA methyltransferase 3a (DNMT3a), Euchromatic histone lysine methyltransferase 2 (EHMT2), or Sirtuin 1 (SIRT1), as well as one drug that restores the p53 function (P53R3), in three different human PDAC cell lines (SKPC-1, MIA PaCa-2, and BxPC-3) using 2D and 3D cell cultures. The synergistic effect of these antitumoral drugs with gemcitabine was tested and the most efficient combinations were characterized by RNA-seq. The inhibition of HDAC1/4 (MS275), HDAC1/4/SIRT1/DNMT3a (UVI5008) or EHMT2 (BIX01294) induced a significant reduction on the cell viability, even in gemcitabine-resistance cells. The combination of UVI5008 or MS275 with gemcitabine induced a synergistic effect at low concentration and the RNA-Seq analysis revealed some synergy candidate genes as potential biomarkers. Reverting aberrant epigenetic modifications in combination with gemcitabine offers an alternative treatment for PDAC patients, with an important reduction of the therapeutic dose.

RAS-mediated tumor stress adaptation and the targeting opportunities it presents

Cellular stress is known to function in synergistic cooperation with oncogenic mutations during tumorigenesis to drive cancer progression. Oncogenic RAS is a strong inducer of a variety of pro-tumorigenic cellular stresses, and also enhances the ability of cells to tolerate these stresses through multiple mechanisms. Many of these oncogenic, RAS-driven, stress-adaptive mechanisms have also been implicated in tolerance and resistance to chemotherapy and to therapies that target the RAS pathway. Understanding how oncogenic RAS shapes cellular stress adaptation and how this functions in drug resistance is of vital importance for identifying new therapeutic targets and therapeutic combinations to treat RAS-driven cancers.

Recent Advances in Pancreatic Cancer: Novel Prognostic Biomarkers and Targeted Therapy-A Review of the Literature

Pancreatic adenocarcinoma carries a devastating prognosis. For locally advanced and metastatic disease, several chemotherapeutic regimens are currently being used. Over the past years, novel approaches have included targeting EGFR, NTRK, PARP, K-Ras as well as stroma and fibrosis, leading to approval of NTRK and PARP inhibitors. Moreover, immune check point inhibitors and different combinational approaches involving immunotherapeutic agents are being investigated in many clinical trials. MiRNAs represent a novel tool and are thought to greatly improve management by allowing for earlier diagnosis and for more precise guidance of treatment.

Apamin-Conjugated Alendronate Sodium Nanocomplex for Management of Pancreatic Cancer

Pancreatic cancer has a low survival rate and has limited therapeutic options due to the peculiarity of the tumor tissue. Cancer nanotechnology provides several opportunities to resolve such difficulties as a result of the high surface-to-volume ratio of nanostructures. Peptide-drug nanocomplexes have proved to have immense potential in anticancer activity against pancreatic cancer cells. Thus, in the present study apamin (APA) and alendronate sodium (ALS) were combined to form nanocomplexes (APA-ALS-NC) against pancreatic cancer cells. Optimization of ALS, incubation time, and sonication time in terms of particle size of the nanocomplex was carried out. The optimized formulation was evaluated for anticancer activities in pancreatic cancer cells (PANC-1 cells). A Box-Behnken design using ALS, incubation time, and sonication time as independent factors and particle size as the response was chosen to optimize the APA-ALS-NC formulation. The optimized APA-ALS-NC had a particle size of 161.52 ± 8.4 nm. The evaluation of APA-ALS-NC in PANC-1 cells was carried out using various in vitro tests. The IC₅₀ values were determined by MTT assay and found to be 37.6 ± 1.65, 13.4 ± 0.59, and 1.01 ± 0.04 µg/mL for ALS, APA, and APA-ALS-NC, respectively. The higher cytotoxicity activity of APA-ALS-NC was confirmed from the higher percentage of cells in the necrosis phase (apoptosis study) and the G2-M phase (cell cycle study) compared to that of ALS and APA. While the loss of mitochondrial membrane potential was less for APA-ALS-NC, the levels of IL-1β, TNF-α, caspase-3, ROS, IL-6, and NF-kB showed that APA-ALS-NC can significantly enhance apoptosis and cytotoxicity in PANC-1 cells. Moreover, Bax (10.87 ± 1.36), Bcl-2 (0.27 ± 0.02), and p53 (9.16 ± 1.22) gene expressions confirmed that APA-ALS-NC had a significant apoptotic effect compared to ALS and APA. In summary, the APA-ALS-NC had a more significant cytotoxic effect than ALS and APA. The results of the present study are promising for further evaluation in pre-clinical and clinical trials for arriving at a successful therapeutic strategy against pancreatic cancer.

Oncogenic KRAS engages an RSK1/NF1 pathway to inhibit wild-type RAS signaling in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is a lethal malignancy with limited treatment options. Although activating mutations of the KRAS GTPase are the predominant dependency present in >90% of PDAC patients, targeting KRAS mutants directly has been challenging in PDAC. Similarly, strategies targeting known KRAS downstream effectors have had limited clinical success due to feedback mechanisms, alternate pathways, and dose-limiting toxicities in normal tissues. Therefore, identifying additional functionally relevant KRAS interactions in PDAC may allow for a better understanding of feedback mechanisms and unveil potential therapeutic targets. Here, we used proximity labeling to identify protein interactors of active KRAS in PDAC cells. We expressed fusions of wild-type (WT) (BirA-KRAS4B), mutant (BirA-KRAS4B^G12D), and nontransforming cytosolic double mutant (BirA-KRAS4B^G12D/C185S) KRAS with the BirA biotin ligase in murine PDAC cells. Mass spectrometry analysis revealed that RSK1 selectively interacts with membrane-bound KRAS^G12D, and we demonstrate that this interaction requires NF1 and SPRED2. We find that membrane RSK1 mediates negative feedback on WT RAS signaling and impedes the proliferation of pancreatic cancer cells upon the ablation of mutant KRAS. Our findings link NF1 to the membrane-localized functions of RSK1 and highlight a role for WT RAS signaling in promoting adaptive resistance to mutant KRAS-specific inhibitors in PDAC.

Integrative Genomic Analysis of Gemcitabine Resistance in Pancreatic Cancer by Patient-derived Xenograft Models

PURPOSE

Gemcitabine is most commonly used for pancreatic cancer. However, the molecular features and mechanisms of the frequently occurring resistance remain unclear. This work aims at exploring the molecular features of gemcitabine resistance and identifying candidate biomarkers and combinatorial targets for the treatment.

EXPERIMENTAL DESIGN

In this study, we established 66 patient-derived xenografts (PDXs) on the basis of clinical pancreatic cancer specimens and treated them with gemcitabine. We generated multiomics data (including whole-exome sequencing, RNA sequencing, miRNA sequencing, and DNA methylation array) of 15 drug-sensitive and 13 -resistant PDXs before and after the gemcitabine treatment. We performed integrative computational analysis to identify the molecular networks related to gemcitabine intrinsic and acquired resistance. Then, short hairpin RNA-based high-content screening was implemented to validate the function of the deregulated genes.

RESULTS

The comprehensive multiomics analysis and functional experiment revealed that MRPS5 and GSPT1 had strong effects on cell proliferation, and CD55 and DHTKD1 contributed to gemcitabine resistance in pancreatic cancer cells. Moreover, we found miR-135a-5p was significantly associated with the prognosis of patients with pancreatic cancer and could be a candidate biomarker to predict gemcitabine response. Comparing the molecular features before and after the treatment, we found that PI3K-Akt, p53, and hypoxia-inducible factor-1 pathways were significantly altered in multiple patients, providing candidate target pathways for reducing the acquired resistance.

CONCLUSIONS

This integrative genomic study systematically investigated the predictive markers and molecular mechanisms of chemoresistance in pancreatic cancer and provides potential therapy targets for overcoming gemcitabine resistance.

Knockdown of the DJ-1 (PARK7) gene sensitizes pancreatic cancer to erlotinib inhibition

The epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor erlotinib, in combination with gemcitabine, has been shown to be a promising therapy in the treatment of pancreatic cancer. Our previous study showed that DJ-1 promotes invasion and metastasis of pancreatic cancer cells by activating SRC/extracellular signal-regulated kinase (ERK)/uPA. The aim of this study was to evaluate whether knockdown of DJ-1 expression can sensitize pancreatic cancer cells to erlotinib treatment. Knockdown of DJ-1 expression accelerated erlotinib-induced cell apoptosis and improved the inhibitory effect of erlotinib on pancreatic cancer cell proliferation (for the BxPC-3, PANC-1, and MiaPACa-2 cell lines, regardless of KRAS mutation status) in vitro and in xenograft tumor growth in vivo. Knockdown of DJ-1 decreased K-RAS expression, membrane translocation, and activity in BxPC-3 cells. Knockdown of DJ-1 also decreased K-RAS, H-RAS, and N-RAS expression in PANC-1 and MiaPACa-2 cells. Knockdown of DJ-1 synergistically inhibited AKT and ERK1/2 phosphorylation with erlotinib in pancreatic cancer cells. These findings indicate that DJ-1 may activate the RAS pathway, reinforcing erlotinib drug resistance. Therefore, blocking DJ-1 in combination with the EGFR tyrosine kinase inhibitor erlotinib may be an attractive therapeutic target in pancreatic cancer.

Molecular Therapeutics of Pancreatic Ductal Adenocarcinoma: Targeted Pathways and the Role of Cancer Stem Cells

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal cancers in humans due to late detection and highly metastatic characteristics. PDAC cells vary in their tumorigenic capabilities with the presence of a subset of PDAC cells known as pancreatic cancer stem cells (CSCs), which are more resistant to currently used therapeutics. Here, we describe the role of CSCs and tumour stroma in developing therapeutic strategies for PDAC and suggest that developmental plasticity could be considered a hallmark of cancers. We provide an overview of the molecular targets in PDAC treatments, including targeted therapies of cellular processes such as proliferation, evasion of growth suppressors, activating metastasis, and metabolic effects. Since PDAC is an inflammation-driven cancer, we also revisit therapeutic strategies targeting inflammation and immunotherapy. Lastly, we suggest that targeting epigenetic mechanisms opens therapeutic routes for heterogeneous cancer cell populations, including CSCs.

RPL21 siRNA Blocks Proliferation in Pancreatic Cancer Cells by Inhibiting DNA Replication and Inducing G1 Arrest and Apoptosis

Background

Our previous study showed that the ribosomal protein L21 (RPL21) may play an important role in the development and survival of pancreatic cancer. In this article, RNA interference (RNAi) experiments were performed with RPL21-specific small interfering RNA (siRNA) to elucidate the mechanism by which RPL21 controls PC PANC-1 and BxPC-3 cell proliferation.

Methods

In the present study, PANC-1, BxPC-3 cells, and BALB/c nude mice were used to investigate antitumor effect and mechanism by which RPL21 controls cell proliferation and apoptosis in vitro and in vivo. The effects of RPL21 knockdown on PANC-1 and BxPC-3 cell proliferation, cell cycle and cell apoptosis in vitro were determined using 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide assays and flow cytometry assay. The mechanism of RPL21 regulating cell proliferation was investigated using transcriptome sequencing analysis and luciferase reporter assay. The effects of RPL21 knockdown on PANC-1 and BxPC-3 cell proliferation in vivo were determined using BALB/c nude mice tumor model.

Results

In PANC-1 and BxPC-3 cells, the knockdown of RPL21 expression with corresponding siRNA suppressed cell proliferation in vitro and in vivo, inhibited DNA replication, and induced arrests in the G1 phase of the cell cycle. Further results showed that the mini-chromosome maintenance (MCM) protein family (MCM2-7), CCND1 and CCNE1 were down-regulated significantly in PANC-1 and BxPC-3 cells after transfected with RPL21 siRNA, which suggests that the suppression of DNA replication is due to the reduced expression of MCM2-7 family, and the induction of G1 arrest is correlated with the inhibition of CCND1 and CCNE1. Luciferase reporter assay showed that RPL21 controls the DNA replication and G1-S phase progression possibly through the regulation of E2F1 transcription factor in PC cells. Moreover, RPL21 siRNA showed an apoptosis-inducing effect only in BxPC-3 and PANC-1 cells but not in normal HPDE6-C7 cells. The increase of caspase-8 activities and the loss of mitochondrial membrane potential after RPL21 silencing indicates that the RPL21 gene may be involved in caspase-8-related mitochondrial apoptosis.

Conclusion

Our findings suggest that siRNA against the RPL21 gene possesses a potential anti-cancer activity for PC cells by inhibiting their proliferation and DNA replication, as well as inducing cell cycle G1 arrest and cell apoptosis.

Screening potential microRNAs associated with pancreatic cancer: Data mining based on RNA sequencing and microarrays

Pancreatic cancer is a malignant tumor of the digestive tract, rendering it difficult to make an accurate diagnosis. The 5 year survival rate for pancreatic cancer is <1%, and surgical resection rarely proves to be effective. Therefore, the identification of more effective methods for the early detection of pancreatic cancer is an urgent requirement. The present study aimed to explore key genes and microRNAs (miRNAs) associated with the pathogenesis of pancreatic cancer. Public databases were searched, and the data were integrated from The Cancer Genome Atlas and Gene Expression Omnibus databases, leading to the identification of 23 differentially expressed miRNAs (DE-miRNAs). A total of four of the DE-miRNAs were upregulated (hsa-miR-892b, hsa-miR-194-2, hsa-miR-200a and hsa-miR-194-1), whereas 19 downregulated DE-miRNAs (hsa-miR-424, hsa-miR-191, hsa-miR-484, hsa-miR-142, hsa-miR-15b, hsa-miR-450a-1, hsa-miR-423, hsa-miR-126, hsa-miR-505, hsa-miR-16-1, hsa-miR-342, hsa-miR-130a, hsa-miR-3613, hsa-miR-450a-2, hsa-miR-26b, hsa-miR-451, hsa-miR-19b-2, hsa-miR-106a and hsa-miR-503) were identified using the cut-off criteria of P<0.05 and |log 2FC|>1.0. Hsa-miR-3613-5p was identified as a prognostic DE-miRNA. The functional enrichment analyses demonstrated that the target genes of hsa-miR-3613-5p may be associated with the p53 signaling pathway. Survival analysis performed for genes in the p53 signaling pathway revealed that cyclin-dependent kinase 6 and ribonucleoside-diphosphate reductase subunit M2 may be the most likely to be associated with prognostic value. The integrated analysis performed in the current study demonstrated that hsa-miR-3613-5p may be used as a potential prognostic marker for pancreatic cancer.

Inhibition of miR-21 Regulates Mutant KRAS Effector Pathways and Intercepts Pancreatic Ductal Adenocarcinoma Development

Almost all pancreatic ductal adenocarcinomas (PDA) develop following KRAS activation, which triggers epithelial transformation and recruitment of desmoplastic stroma through additional transcriptional and epigenetic regulation, but only a few of these regulatory mechanisms have been described. We profiled dysregulated miRNAs starting with the earliest premalignant pancreatic intraepithelial neoplasias (PanIN) in genetically engineered mutated KRAS and P53 (KPC) mice programmed to recapitulate human PDA tumorigenesis. We identified miR-21 and miR-224 as cell-specific and compartment-specific regulators in PanINs and PDA. miR-21 is overexpressed in tumor epithelial cells of premalignant ducts, while miR-224 is overexpressed in cancer-associated fibroblasts in PDA stroma. Inhibition of miR-21 reverted protumorigenic functionalities to baseline levels. Overexpression of miR-224 induced activated phenotypes in normal fibroblasts. In vivo miR-21 inhibition improved survival in established PDA. Importantly, early systemic miR-21 inhibition completely intercepted premalignant progression. Finally, an evaluation of miR-21 expression in the PDA cohort of The Cancer Genome Atlas identified a correlation between tumor epithelial cell content and miR-21 expression in human tumors providing further rationale for conducting human studies. Thus, miR-21 may be useful for early PanIN detection, and for intercepting developing premalignant pancreatic lesions and other KRAS-driven premalignancies.

Combination of a novel microtubule inhibitor MBRI-001 and gemcitabine synergistically induces cell apoptosis by increasing DNA damage in pancreatic cancer cell lines

Pancreatic cancer (PC) is a highly malignant cancer with poor prognosis. Although gemcitabine (GEM; 2',2'-difluoro-deoxycytidine) has been used as the first-line chemotherapeutic agent in PC treatment for decades, its limited efficacy remains a significant clinical issue, which may be resolved by GEM combination therapy. In this study, we aimed to investigate the anti-tumor effects of MBRI-001 in combination with GEM in BxPC-3 and MIA PaCa-2 human PC cell lines. In vitro and in vivo results indicate that MBRI-001 showed synergistic activity with GEM. GEM induced apoptosis by increasing DNA damage (phosphorylated core histone protein H2AX (γ-H2AX)), MBRI-001 activated mitochondrial-apoptotic pathway (cleaved poly-ADP ribose polymerase (PARP)). Thus, the combination of the two intensified both apoptosis and DNA damage and showed significantly superior anti-tumor activity compared to each agent alone. The adoption of combination of MBRI-001 with GEM may be beneficial as they act synergistically and thus, can be a potential therapeutic choice for improving the prognosis of PC patients in the future.

Targeting the "undruggable" RAS - new strategies - new hope?

K-RAS is the most frequently mutated oncogene in solid tumors, such as pancreatic, colon or lung cancer. The GTPase K-RAS can either be in an active (GTP-loaded) or inactive (GDP-loaded) form. In its active form K-RAS forwards signals from growth factors, cytokines or hormones to the nucleus, regulating essential pathways, such as cell proliferation and differentiation. In turn, activating somatic mutations of this proto-oncogene deregulate the complex interplay between GAP (GTPase-activating) - and GEF (Guanine nucleotide exchange factor) - proteins, driving neoplastic transformation. Due to a rather shallow surface, K-RAS lacks proper binding pockets for small molecules, hindering drug development over the past thirty years. This review summarizes recent progress in the development of low molecular antagonists and further shows insights of a newly described interaction between mutant K-RAS signaling and PD-L1 induced immunosuppression, giving new hope for future treatments of K-RAS mutated cancer.

Spotlight on liposomal irinotecan for metastatic pancreatic cancer: patient selection and perspectives

Pancreatic cancer is a highly lethal disease, where the mortality closely matches increasing incidence. Pancreatic ductal adenocarcinoma (PDAC) is the most common histologic type that tends to metastasize early in tumor progression. For metastatic PDAC, gemcitabine had been the mainstay treatment for the past three decades. The treatment landscape has changed since 2010, and current first-line chemotherapy includes triplet drugs like FOLFIRINOX (folinic acid, 5-fluorouracil, irinotecan, and oxaliplatin), and doublet agents like nab-paclitaxel and gemcitabine. Nanoliposomal encapsulated irinotecan (nal-IRI) was developed as a novel formulation to improve drug delivery, effectiveness, and limit toxicities. Nal-IRI, in combination with leucovorin-modulated fluorouracil (5-FU/LV), was found in a large randomized phase III clinical trial (NAPOLI-1) to significantly improve overall survival in patients who progressed on gemcitabine-based therapy. This review will focus on the value of using nal-IRI, toxicities, recent clinical experiences, and tools to improve patient outcomes in this setting.

HH1-1, a novel Galectin-3 inhibitor, exerts anti-pancreatic cancer activity by blocking Galectin-3/EGFR/AKT/FOXO3 signaling pathway

Pancreatic ductal adenocarcinoma is a highly malignant gastrointestinal tumor. Molecular targeting therapy for pancreatic cancer is still limited. High expressed Galectin-3 in pancreatic cancer is positively correlated with disease progression, indicating that Galectin-3 can be employed as a predictor of poor prognosis. From safflower, we isolated and purified a homogeneous polysaccharide, HH1-1, which could bind to and inhibit Galectin-3. HH1-1 could block the interaction between Galectin-3 and EGFR. Following HH1-1 treatment, the binding ability between EGFR and Galectin-3 was reduced by 245.28 folds. HH1-1 could suppress pancreatic cancer cell proliferation, arrest the cell cycle in S phase, induce cell apoptosis, inhibit angiogenesis and impede tumor cell migration and invasion. Moreover, HH1-1 affected the Galectin-3/EGFR/AKT/FOXO3 signaling pathway and possessed anti-pancreatic cancer activity in vitro and in vivo, especially in patient-derived xenografts. Further study suggested that HH1-1 had almost no toxicity both in vitro and in vivo. This adds new evidence to suggest that HH1-1 could be a promising therapeutic agent and support the pursuit of the Galectin-3 as a target in pancreatic cancer treatment.

Role of Gene Therapy in Pancreatic Cancer-A Review

Mortality from pancreatic ductal adenocarcinoma (PDAC) has remained essentially unchanged for decades and its relative contribution to overall cancer death is projected to only increase in the coming years. Current treatment for PDAC includes aggressive chemotherapy and surgical resection in a limited number of patients, with median survival of optimal treatment rather dismal. Recent advances in gene therapies offer novel opportunities for treatment, even in those with locally advanced disease. In this review, we summarize emerging techniques to the design and administration of virotherapy, synthetic vectors, and gene-editing technology. Despite these promising advances, shortcomings continue to exist and here will also be highlighted those approaches to overcoming obstacles in current laboratory and clinical research.

Targeted Therapies for Pancreatic Cancer

Pancreatic cancer is the third leading cause of cancer related death and by 2030, it will be second only to lung cancer. We have seen tremendous advances in therapies for lung cancer as well as other solid tumors using a molecular targeted approach but our progress in treating pancreatic cancer has been incremental with median overall survival remaining less than one year. There is an urgent need for improved therapies with better efficacy and less toxicity. Small molecule inhibitors, monoclonal antibodies and immune modulatory therapies have been used. Here we review the progress that we have made with these targeted therapies.