K-Ras promotes growth transformation and invasion of immortalized human pancreatic cells by Raf and phosphatidylinositol 3-kinase signaling

Base-excision repair pathway regulates transcription-replication conflicts in pancreatic ductal adenocarcinoma

Oncogenic mutations (such as in KRAS) can dysregulate transcription and replication, leading to transcription-replication conflicts (TRCs). Here, we demonstrate that TRCs are enriched in human pancreatic ductal adenocarcinoma (PDAC) compared to other common solid tumors or normal cells. Several orthogonal approaches demonstrated that TRCs are oncogene dependent. A small interfering RNA (siRNA) screen identified several factors in the base-excision repair (BER) pathway as main regulators of TRCs in PDAC cells. Inhibitors of BER pathway (methoxyamine and CRT) enhanced TRCs. Mechanistically, BER pathway inhibition severely altered RNA polymerase II (RNAPII) and R-loop dynamics at nascent DNA, causing RNAPII trapping and contributing to enhanced TRCs. The ensuing DNA damage activated the ATR-Chk1 pathway. Co-treatment with ATR inhibitor (VX970) and BER inhibitor (methoxyamine) at clinically relevant doses synergistically enhanced DNA damage and reduced cell proliferation in PDAC cells. The study provides mechanistic insights into the regulation of TRCs in PDAC by the BER pathway, which has biologic and therapeutic implications.

A bioprinted sea-and-island multicellular model for dissecting human pancreatic tumor-stroma reciprocity and adaptive metabolism

Pancreatic ductal adenocarcinoma (PDAC) presents a formidable clinical challenge due to its intricate microenvironment characterized by desmoplasia and complex tumor-stroma interactions. Conventional models hinder studying cellular crosstalk for therapeutic development. To recapitulate key features of PDAC masses, this study creates a novel sea-and-island PDAC tumor construct (s&i PTC). The s&i PTC consists of 3D-printed islands of human PDAC cells positioned within an interstitial extracellular matrix (ECM) populated by human cancer-associated fibroblasts (CAFs). This design closely mimics the in vivo desmoplastic architecture and nutrient-poor conditions. The model enables studying dynamic tumor-stroma crosstalk and signaling reciprocity, revealing both known and yet-to-be-discovered multicellular metabolic adaptations. Using the model, we discovered the orchestrated dynamic alterations of CAFs under nutrient stress, resembling critical in vivo human tumor niches, such as the secretion of pro-tumoral inflammatory factors. Additionally, nutrient scarcity induces dynamic alterations in the ECM composition and exacerbates poor cancer cell differentiation-features well-established in PDAC progression. Proteomic analysis unveiled the enrichment of proteins associated with aggressive tumor behavior and ECM remodeling in response to poor nutritional conditions, mimicking the metabolic stresses experienced by avascular pancreatic tumor cores. Importantly, the model's relevance to patient outcomes is evident through an inverse correlation between biomarker expression patterns in the s&i PTCs and PDAC patient survival rates. Key findings include upregulated MMPs and key ECM proteins (such as collagen 11 and TGFβ) under nutrient-avid conditions, known to be regulated by CAFs, alongside the concomitant reduction in E-cadherin expression associated with a poorly differentiated PDAC state under nutrient deprivation. Furthermore, elevated levels of hyaluronic acid (HA) and integrins in response to nutrient deprivation underscore the model's fidelity to the PDAC microenvironment. We also observed increased IL-6 and reduced α-SMA expression under poor nutritional conditions, suggesting a transition of CAFs from myofibroblastic to inflammatory phenotypes under a nutrient stress akin to in vivo niches. In conclusion, the s&i PTC represents a significant advancement in engineering clinically relevant 3D models of PDAC masses. It offers a promising platform for elucidating tumor-stroma interactions and guiding future therapeutic strategies to improve patient outcomes.

Regulatory role of miRNAs in nasopharyngeal cancer involving PTEN/PI3K/AKT, TGFβ/SMAD, RAS/MAPK, Wnt/β-catenin and pRB-E2F signaling pathways: A review

MicroRNAs (miRNA) are small and conserved noncoding RNA molecules that regulate gene expression at the posttranscriptional level. These groups of RNAs are crucial in various cellular processes, especially in mediating disease pathogenesis, particularly cancer. The dysregulation of miRNAs was reported in many cancer types, including nasopharyngeal cancer (NPC), which is a malignant tumor of the nasopharynx. In this review, miRNAs involvement in crucial signaling pathways associated with NPC such as PTEN/PI3K/AKT, TGFβ/SMAD, RAS/MAPK, Wnt/β-catenin and pRB-E2F was investigated. miRNAs could function as tumor suppressor-miR or onco-miR in NPC profoundly influenced cell cycle, apoptosis, proliferation, migration, and metastasis. This comprehensive review of current literature provided a thorough profile of miRNAs and their interplay with the aforementioned signaling pathways in NPC. Understanding these molecular interactions could remarkably impact the diagnosis, prognosis, and therapeutic strategies for NPC.

Structural insights into the complex of oncogenic KRas4BG12V and Rgl2, a RalA/B activator

About a quarter of total human cancers carry mutations in Ras isoforms. Accumulating evidence suggests that small GTPases, RalA, and RalB, and their activators, Ral guanine nucleotide exchange factors (RalGEFs), play an essential role in oncogenic Ras-induced signalling. We studied the interaction between human KRas4B and the Ras association (RA) domain of Rgl2 (Rgl2RA), one of the RA-containing RalGEFs. We show that the G12V oncogenic KRas4B mutation changes the interaction kinetics with Rgl2RA The crystal structure of the KRas4BG12V: Rgl2RA complex shows a 2:2 heterotetramer where the switch I and switch II regions of each KRasG12V interact with both Rgl2RA molecules. This structural arrangement is highly similar to the HRasE31K:RALGDSRA crystal structure and is distinct from the well-characterised Ras:Raf complex. Interestingly, the G12V mutation was found at the dimer interface of KRas4BG12V with its partner. Our study reveals a potentially distinct mode of Ras:effector complex formation by RalGEFs and offers a possible mechanistic explanation for how the oncogenic KRas4BG12V hyperactivates the RalA/B pathway.

Novel insights on perils and promises of miRNA in understanding colon cancer metastasis and progression

Colorectal cancer (CRC) is the third highest frequent malignancy and ultimate critical source of cancer-associated mortality around the world. Regardless of latest advances in molecular and surgical targeted medicines that have increased remedial effects in CRC patients, the 5-year mortality rate for CRC patients remains dismally low. Evidence suggests that microRNAs (miRNAs) execute an essential part in the development and spread of CRC. The miRNAs are a type of short non-coding RNA that exhibited to control the appearance of tumor suppressor genes and oncogenes. miRNA expression profiling is already being utilized in clinical practice as analytical and prognostic biomarkers to evaluate cancer patients' tumor genesis, advancement, and counteraction to drugs. By modulating their target genes, dysregulated miRNAs are linked to malignant characteristics (e.g., improved proliferative and invasive capabilities, cell cycle aberration, evasion of apoptosis, and promotion of angiogenesis). This review presents an updated summary of circulatory miRNAs, tumor-suppressive and oncogenic miRNAs, and the potential reasons for dysregulated miRNAs in CRC. Further we will explore the critical role of miRNAs in CRC drug resistance.

Small molecule antagonist of CXCR2 and CXCR1 inhibits tumor growth, angiogenesis, and metastasis in pancreatic cancer

Pancreatic cancer (PC) has a poor prognosis, and current therapeutic strategies are ineffective in advanced diseases. We and others have shown the aberrant expression of CXCR2 and its ligands in PC development and progression. Our objective for this study was to evaluate the therapeutic utility of CXCR2/1 targeting using an small molecule antagonist, SCH-479833, in different PC preclinical murine models (syngeneic or xenogeneic). Our results demonstrate that CXCR2/1 antagonist had both antitumor and anti-metastatic effects in PC. CXCR2/1 antagonist treatment inhibited tumor cell proliferation, migration, angiogenesis, and recruitment of neutrophils, while it increased apoptosis. Treatment with the antagonist enhanced fibrosis, tumor necrosis, and extramedullary hematopoiesis. Together, these findings suggest that selectively targeting CXCR2/1 with small molecule inhibitors is a promising therapeutic approach for inhibiting PC growth, angiogenesis, and metastasis.

LAMC2 marks a tumor-initiating cell population with an aggressive signature in pancreatic cancer

BACKGROUND

Tumor-initiating cells (TIC), also known as cancer stem cells, are considered a specific subpopulation of cells necessary for cancer initiation and metastasis; however, the mechanisms by which they acquire metastatic traits are not well understood.

METHODS

LAMC2 transcriptional levels were evaluated using publicly available transcriptome data sets, and LAMC2 immunohistochemistry was performed using a tissue microarray composed of PDAC and normal pancreas tissues. Silencing and tracing of LAMC2 was performed using lentiviral shRNA constructs and CRISPR/Cas9-mediated homologous recombination, respectively. The contribution of LAMC2 to PDAC tumorigenicity was explored in vitro by tumor cell invasion, migration, sphere-forming and organoids assays, and in vivo by tumor growth and metastatic assays. mRNA sequencing was performed to identify key cellular pathways upregulated in LAMC2 expressing cells. Metastatic spreading induced by LAMC2- expressing cells was blocked by pharmacological inhibition of transforming growth factor beta (TGF-β) signaling.

RESULTS

We report a LAMC2-expressing cell population, which is endowed with enhanced self-renewal capacity, and is sufficient for tumor initiation and differentiation, and drives metastasis. mRNA profiling of these cells indicates a prominent squamous signature, and differentially activated pathways critical for tumor growth and metastasis, including deregulation of the TGF-β signaling pathway. Treatment with Vactosertib, a new small molecule inhibitor of the TGF-β type I receptor (activin receptor-like kinase-5, ALK5), completely abrogated lung metastasis, primarily originating from LAMC2-expressing cells.

CONCLUSIONS

We have identified a highly metastatic subpopulation of TICs marked by LAMC2. Strategies aimed at targeting the LAMC2 population may be effective in reducing tumor aggressiveness in PDAC patients. Our results prompt further study of this TIC population in pancreatic cancer and exploration as a potential therapeutic target and/or biomarker.

An Exosomal miRNA Biomarker for the Detection of Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) remains a difficult tumor to diagnose and treat. To date, PDAC lacks routine screening with no markers available for early detection. Exosomes are 40-150 nm-sized extracellular vesicles that contain DNA, RNA, and proteins. These exosomes are released by all cell types into circulation and thus can be harvested from patient body fluids, thereby facilitating a non-invasive method for PDAC detection. A bioinformatics analysis was conducted utilizing publicly available miRNA pancreatic cancer expression and genome databases. Through this analysis, we identified 18 miRNA with strong potential for PDAC detection. From this analysis, 10 (MIR31, MIR93, MIR133A1, MIR210, MIR330, MIR339, MIR425, MIR429, MIR1208, and MIR3620) were chosen due to high copy number variation as well as their potential to differentiate patients with chronic pancreatitis, neoplasms, and PDAC. These 10 were examined for their mature miRNA expression patterns, giving rise to 18 mature miRs for further analysis. Exosomal RNA from cell culture media was analyzed via RTqPCR and seven mature miRs exhibited statistical significance (miR-31-5p, miR-31-3p, miR-210-3p, miR-339-5p, miR-425-5p, miR-425-3p, and miR-429). These identified biomarkers can potentially be used for early detection of PDAC.

NetrinG1+ cancer-associated fibroblasts generate unique extracellular vesicles that support the survival of pancreatic cancer cells under nutritional stress

It is projected that in 5 years, pancreatic cancer will become the second deadliest cancer in the United States. A unique aspect of pancreatic ductal adenocarcinoma (PDAC) is its stroma; rich in cancer-associated fibroblasts (CAFs) and a dense CAF-generated extracellular matrix (ECM). These pathogenic stroma CAF/ECM units cause the collapse of local blood vessels rendering the tumor microenvironment nutrient-poor. PDAC cells are able to survive this state of nutrient stress via support from CAF-secreted material, which includes small extracellular vesicles (sEVs). The tumor-supportive CAFs possess a distinct phenotypic profile, compared to normal-like fibroblasts, expressing NetrinG1 (NetG1) at the plasma membrane, and active Integrin α₅β₁ localized to the multivesicular bodies; traits indicative of poor patient survival. We herein report that NetG1⁺ CAFs secrete sEVs that stimulate Akt-mediated survival in nutrient-deprived PDAC cells, protecting them from undergoing apoptosis. Further, we show that NetG1 expression in CAFs is required for the pro-survival properties of sEVs. Additionally, we report that the above-mentioned CAF markers are secreted in distinct subpopulations of EVs; with NetG1 being enriched in exomeres, and Integrin α₅β₁ being enriched in exosomes. Finally, we found that NetG1 and Integrin α₅β₁ were detected in sEVs collected from plasma of PDAC patients, while their levels were significantly lower in plasma-derived sEVs of sex/age-matched healthy donors. The discovery of these tumor-supporting CAF-EVs elucidates novel avenues in tumor-stroma interactions and pathogenic stroma detection.

The Potential Mechanisms of Cinobufotalin Treating Colon Adenocarcinoma by Network Pharmacology

Network pharmacology, as a novel way using bioinformatics to explore drug targets and interactions in cancer, broadens our understanding of drug action, thereby facilitating drug discovery. Here, we utilized network pharmacology to explore the role and mechanism by which cinobufotalin functions in colon adenocarcinoma (COAD). We found that cinobufotalin represses the growth and proliferation of colon cancer cells, and integrated public databases for targets reported to be associated with COAD, together with those predicted to be targets of cinobufotalin. Targets overlapped between COAD-associated proteins and cinobufotalin target proteins were used to filter candidate targets of cinobufotalin in COAD. The following proteins were thought to occupy a key position in COAD-cinobufotalin target networks: SRC, PIK3R1, MAPK1, PIK3CA, HSP90AA1, CTNNB1, GRB2, RHO1, PTPN11, and EGFR. The networks regulated by cinobufotalin were involved mainly in extracellular signal stimulation and transduction, including MAPK signaling pathway, PI3K-AKT signaling pathway, and JAK-STAT signaling pathway. Besides, transcriptome sequencing results also indicated that cinobufotalin inhibits the response of colon cancer cells to extracellular stimulation and promotes cell apoptosis. Molecular docking results showed that cinobufotalin matches in the pocket of the top candidate cinobufotalin target proteins (SRC, PIK3R1, MAPK1 and PIK3CA). These findings demonstrate cinobufotalin can be developed as potential anti-cancer therapeutics.

Tumor Suppressor microRNAs in Gastrointestinal Cancers: A Mini-Review

BACKGROUND

Gastrointestinal (GI) cancer is associated with a group of cancers affecting the organs in the GI tract, with a high incidence and mortality rate. This type of cancer development involves a series of molecular events that arise by the dysregulation of gene expressions and microRNAs (miRNAs).

OBJECTIVES

This mini-review focuses on elucidating the mechanism of tumor suppressor miRNA-mediated oncogenic gene silencing, which may contribute to a better understanding of miRNA-mediated gene expression regulation of cell cycle, proliferation, invasion, and apoptosis in GI cancers. In this review, the biological significance of tumor suppressor miRNAs involved in gastrointestinal cancers is briefly explained.

METHODS

The articles were searched with the keywords 'miRNA', 'gastrointestinal cancers', 'esophageal cancer', 'gastric cancer', 'colorectal cancer', 'pancreatic cancer', 'liver cancer', and 'gall bladder cancer' from the Google Scholar and PubMed databases. A total of 71 research and review articles have been collected and referred for this study.

RESULTS

This review summarises recent research enhancing the effectiveness of miRNAs as novel prognostic, diagnostic, and therapeutic markers for GI cancer treatment strategies. The expression pattern of various miRNAs has been dysregulated in GI cancers, which are associated with proliferation, cell cycle regulation, apoptosis, migration, and invasion.

CONCLUSION

The role of tumor suppressor miRNAs in the negative regulation of oncogenic gene expression was thoroughly explained in this review. Its potential role as a microRNA therapeutic candidate is also discussed. Profiling and regulating tumor suppressor miRNA expression in gastrointestinal cancers using miRNA mimics could be used as a prognostic, diagnostic, and therapeutic marker, as well as an elucidating molecular therapeutic approach to tumor suppression.

Combined Alcohol Exposure and KRAS Mutation in Human Pancreatic Ductal Epithelial Cells Induces Proliferation and Alters Subtype Signatures Determined by Multi-Omics Analysis

Simple Summary

Pancreatic ductal adenocarcinoma is a deadly disease wherein alcohol use increases the risk of developing this cancer. Mutations in the KRAS oncogene are required for alcohol to promote pancreatic cancer in mice, but little is known about the molecular events associated with the combined exposure of alcohol and mutant KRAS expression in pancreas cells. In this study, we use pancreas cell models with and without mutant KRAS to evaluate the impact of chronic alcohol exposure on transcription and protein expression. This study identifies numerous differentially expressed transcripts and proteins that could influence the emergence of oncogenic features, such as increased proliferation, in pancreas cells.

Abstract

Pancreatic Ductal adenocarcinoma (PDAC) is an aggressive cancer commonly exhibiting KRAS-activating mutations. Alcohol contributes to the risk of developing PDAC in humans, and murine models have shown alcohol consumption in the context of KRAS mutation in the pancreas promotes the development of PDAC. The molecular signatures in pancreas cells altered by alcohol exposure in the context of mutant KRAS could identify pathways related to the etiology of PDAC. In this study, we evaluated the combined effects of alcohol exposure and KRAS mutation status on the transcriptome and proteome of pancreatic HPNE cell models. These analyses identified alterations in transcription and translational processes in mutant KRAS cells exposed to alcohol. In addition, multi-omics analysis suggests an increase in the correlation between mRNA transcript and protein abundance in cells exposed to alcohol with an underlying KRAS mutation. Through differential co-expression, SERPINE1 was found to be influential for PDAC development in the context of mutant KRAS and ethanol. In terms of PDAC subtypes, alcohol conditioning of HPNE cells expressing mutant KRAS decreases the Inflammatory subtype signature and increases the Proliferative and Metabolic signatures, as we previously observed in patient samples. The alterations in molecular subtypes were associated with an increased sensitivity to chemotherapeutic agents gemcitabine, irinotecan, and oxaliplatin. These results provide a framework for distinguishing the molecular dysregulation associated with combined alcohol and mutant KRAS in a pancreatic cell line model.

Human Papillomavirus Type 16 Early Protein E7 Activates Autophagy through Inhibition of Dual-Specificity Phosphatase 5

Consistent high-risk human papillomavirus (HPV) infection leads to various malignant cancers. Autophagy can promote cancer progression by helping cancer cells survive under stress or induce oncogenic effects when mutations or abnormalities occur. Mitogen activated protein kinases (MAPKs) can transduce various external or intrinsic stimuli into cellular responses, including autophagy, and dual-specificity phosphates (DUSPs) contribute to the direct regulation of MAPK activities. Previously, we showed that expression of DUSP5 was repressed in HPV16 E7-expressing normal human epidermal keratinocytes (NHEKs). Here we show that clinical HPV16 E7-positive precancerous and cancerous tissues also demonstrate low DUSP5 levels compared with control tissues, indicating that the inverse correlation between HPV16 E7 and DUSP5 is clinically relevant. We furthermore investigated the autophagy response in both DUSP5-deficient and HPV16 E7-expressing NHEKs. Confocal microscopy and Western analysis showed induction of LC3-II levels, autophagosome formation and autophagy fluxes in DUSP5-deficient NHEKs. Furthermore, Western analysis demonstrated specific induction of phosphorylated ERK in DUSP5-deficient and HPV16 E7-expressing NHEKs, indicating that HPV16 E7-mediated repression of DUSP5 results in induced MAPK/ERK signaling. Finally, phosphorylated mTOR and ULK (S757) were reduced in DUSP5-deficient NHEKs, while phosphorylated ULK (S555) and AMPK were increased, thereby inducing canonical autophagy through the mTOR and AMPK pathways. In conclusion, our results demonstrate that HPV16 E7 expression reduces DUSP5 levels, which in turn results in active MAPK/ERK signaling and induction of canonical autophagy through mTOR and MAPK regulation. Given its demonstrated inverse correlation with clinical cancerous tissues, DUSP5 may serve as a potential therapeutic target for cervical cancer.

Concurrent Inhibition of IGF1R and ERK Increases Pancreatic Cancer Sensitivity to Autophagy Inhibitors

The aggressive nature of pancreatic ductal adenocarcinoma (PDAC) mandates the development of improved therapies. As KRAS mutations are found in 95% of PDAC and are critical for tumor maintenance, one promising strategy involves exploiting KRAS-dependent metabolic perturbations. The macrometabolic process of autophagy is upregulated in KRAS-mutant PDAC, and PDAC growth is reliant on autophagy. However, inhibition of autophagy as monotherapy using the lysosomal inhibitor hydroxychloroquine (HCQ) has shown limited clinical efficacy. To identify strategies that can improve PDAC sensitivity to HCQ, we applied a CRISPR-Cas9 loss-of-function screen and found that a top sensitizer was the receptor tyrosine kinase (RTK) insulin-like growth factor 1 receptor (IGF1R). Additionally, reverse phase protein array pathway activation mapping profiled the signaling pathways altered by chloroquine (CQ) treatment. Activating phosphorylation of RTKs, including IGF1R, was a common compensatory increase in response to CQ. Inhibition of IGF1R increased autophagic flux and sensitivity to CQ-mediated growth suppression both in vitro and in vivo. Cotargeting both IGF1R and pathways that antagonize autophagy, such as ERK-MAPK axis, was strongly synergistic. IGF1R and ERK inhibition converged on suppression of glycolysis, leading to enhanced dependence on autophagy. Accordingly, concurrent inhibition of IGF1R, ERK, and autophagy induced cytotoxicity in PDAC cell lines and decreased viability in human PDAC organoids. In conclusion, targeting IGF1R together with ERK enhances the effectiveness of autophagy inhibitors in PDAC.

SIGNIFICANCE

Compensatory upregulation of IGF1R and ERK-MAPK signaling limits the efficacy of autophagy inhibitors chloroquine and hydroxychloroquine, and their concurrent inhibition synergistically increases autophagy dependence and chloroquine sensitivity in pancreatic ductal adenocarcinoma.

Cell Type of Pancreatic Ductal Adenocarcinoma Origin: Implications for Prognosis and Clinical Outcomes

Background

Pancreatic ductal adenocarcinoma (PDAC) is a devastating disease that has no effective early detection method or treatment to date.

Summary

The normal cell type that initiates PDAC, or its cellular origin, is still unknown. To investigate the contribution of distinct normal epithelial cell types to PDAC tumorigenesis, genetically engineered mouse models were used to show that both acinar and ductal cells are capable of giving rise to PDAC. These studies indicated that genetic mutations and pancreatic injury interact differently with each cellular origin to affect their predilection and process for forming PDAC. In this review, we summarize recent findings using various genetically engineered mouse models in the identification and characterization of the PDAC cell of origin. We also discuss potential implications for cellular origin on tumor development, PDAC transcriptional subtype, and disease prognosis of patients.

Key Message

Although it is clear that both ductal and acinar cells have the potential to form PDAC, whether cellular origin can indeed influence patient prognosis and whether knowledge of cellular origin will aid in the diagnosis or treatment of patients in the future will need further study.

MicroRNA-96: A therapeutic and diagnostic tumor marker

Cancer has been always considered as one of the main human health challenges worldwide. One of the main causes of cancer-related mortality is late diagnosis in the advanced stages of the disease, which reduces the therapeutic efficiency. Therefore, novel non-invasive diagnostic methods are required for the early detection of tumors and improving the quality of life and survival in cancer patients. MicroRNAs (miRNAs) have pivotal roles in various cellular processes such as cell proliferation, motility, and neoplastic transformation. Since circulating miRNAs have high stability in body fluids, they can be suggested as efficient noninvasive tumor markers. MiR-96 belongs to the miR-183-96-182 cluster that regulates cell migration and tumor progression as an oncogene or tumor suppressor by targeting various genes in solid tumors. In the present review, we have summarized all of the studies that assessed the role of miR-96 during tumor progression. This review clarifies the molecular mechanisms and target genes recruited by miR-96 to regulate tumor progression and metastasis. It was observed that miR-96 mainly affects tumorigenesis by targeting the structural proteins and FOXO transcription factors.

p53/FBXL20 axis negatively regulates the protein stability of PR55α, a regulatory subunit of PP2A Ser/Thr phosphatase

We have previously reported an important role of PR55α, a regulatory subunit of PP2A Ser/Thr phosphatase, in the support of critical oncogenic pathways required for oncogenesis and the malignant phenotype of pancreatic cancer. The studies in this report reveal a novel mechanism by which the p53 tumor suppressor inhibits the protein-stability of PR55α via FBXL20, a p53-target gene that serves as a substrate recognition component of the SCF (Skp1_Cullin1_F-box) E3 ubiquitin ligase complex that promotes proteasomal degradation of its targeted proteins. Our studies show that inactivation of p53 by siRNA-knockdown, gene-deletion, HPV-E6-mediated degradation, or expression of the loss-of-function mutant p53R175H results in increased PR55α protein stability, which is accompanied by reduced protein expression of FBXL20 and decreased ubiquitination of PR55α. Subsequent studies demonstrate that knockdown of FBXL20 by siRNA mimics p53 deficiency, reducing PR55α ubiquitination and increasing PR55α protein stability. Functional tests indicate that ectopic p53R175H or PR55α expression results in an increase of c-Myc protein stability with concomitant dephosphorylation of c-Myc-T58, which is a PR55α substrate, whose phosphorylation otherwise promotes c-Myc degradation. A significant increase in anchorage-independent proliferation is also observed in normal human pancreatic cells expressing p53R175H or, to a greater extent, overexpressing PR55α. Consistent with the common loss of p53 function in pancreatic cancer, FBXL20 mRNA expression is significantly lower in pancreatic cancer tissues compared to pancreatic normal tissues and low FBXL20 levels correlate with poor patient survival. Collectively, these studies delineate a novel mechanism by which the p53/FBXL20 axis negatively regulates PR55α protein stability.

CHK1 protects oncogenic KRAS-expressing cells from DNA damage and is a target for pancreatic cancer treatment

We apply genetic screens to delineate modulators of KRAS mutant pancreatic ductal adenocarcinoma (PDAC) sensitivity to ERK inhibitor treatment, and we identify components of the ATR-CHK1 DNA damage repair (DDR) pathway. Pharmacologic inhibition of CHK1 alone causes apoptotic growth suppression of both PDAC cell lines and organoids, which correlates with loss of MYC expression. CHK1 inhibition also activates ERK and AMPK and increases autophagy, providing a mechanistic basis for increased efficacy of concurrent CHK1 and ERK inhibition and/or autophagy inhibition with chloroquine. To assess how CHK1 inhibition-induced ERK activation promotes PDAC survival, we perform a CRISPR-Cas9 loss-of-function screen targeting direct/indirect ERK substrates and identify RIF1. A key component of non-homologous end joining repair, RIF1 suppression sensitizes PDAC cells to CHK1 inhibition-mediated apoptotic growth suppression. Furthermore, ERK inhibition alone decreases RIF1 expression and phenocopies RIF1 depletion. We conclude that concurrent DDR suppression enhances the efficacy of ERK and/or autophagy inhibitors in KRAS mutant PDAC.

ZC3HAV1 promotes the proliferation and metastasis via regulating KRAS in pancreatic cancer

Proliferation and metastasis are important malignant features of pancreatic cancer (PC), but the underlying molecular mechanism is unclear. ZC3HAV1, a PARP family member of proteins-enzymes, has been considered to play a significant part in a variety of biological processes. Nonetheless, the functions of ZC3HAV1 in developing PC are still unknown. This research aims to explore the biological function and the expression of ZC3HAV1 shown in PC. In our study, PCR analysis suggested that ZC3HAV1 was expressed at a high level in PC tissues and cell lines, and high ZC3HAV1 expression was remarkably related to poor prognosis. The functional assays indicated that upregulated ZC3HAV1 accelerated PC cell proliferation along with colony formation capacities in vitro. Subsequently, ZC3HAV1 could upregulate cyclin D1 and CDK2 and also promote G1/S transition in cells of PC. What's more, we also discovered that ZC3HAV1 promotes the migration and the invasion of PC cells. It upregulates the expression of EMT (epithelial-mesenchymal transition) relevant markers. Conversely, the functional assays showed that ZC3HAV1 knockdown significantly reduced tumorigenesis. Using bioinformatics analysis and immunoprecipitation assays we found that ZC3HAV1 could directly bind to KRAS and positively regulate its expression. Furthermore, ZC3HAV1 overexpression activated MAPK signaling by increasing p-ERK levels. Conversely, knockdown of KRAS attenuated ZC3HAV1-mediated promotion of proliferation and invasion in cells of PC. The result indicated that ZC3HAV1 was in relation to poor prognosis and accelerated the proliferation and metastasis of PC cells by regulation of KRAS. Our research may offer brand-new evidence to diagnose and treat PC in clinic.

Simultaneous inhibition of PFKFB3 and GLS1 selectively kills KRAS-transformed pancreatic cells

Activating mutations of the oncogenic KRAS in pancreatic ductal adenocarcinoma (PDAC) are associated with an aberrant metabolic phenotype that may be therapeutically exploited. Increased glutamine utilization via glutaminase-1 (GLS1) is one such feature of the activated KRAS signaling that is essential to cell survival and proliferation; however, metabolic plasticity of PDAC cells allow them to adapt to GLS1 inhibition via various mechanisms including activation of glycolysis, suggesting a requirement for combinatorial anti-metabolic approaches to combat PDAC. We investigated whether targeting the glycolytic regulator 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase-3 (PFKFB3) in combination with GLS1 can selectively prevent the growth of KRAS-transformed cells. We show that KRAS-transformation of pancreatic duct cells robustly sensitizes them to the dual targeting of GLS1 and PFKFB3. We also report that this sensitivity is preserved in the PDAC cell line PANC-1 which harbors an activating KRAS mutation. We then demonstrate that GLS1 inhibition reduced fructose-2,6-bisphosphate levels, the product of PFKFB3, whereas PFKFB3 inhibition increased glutamine consumption, and these effects were augmented by the co-inhibition of GLS1 and PFKFB3, suggesting a reciprocal regulation between PFKFB3 and GLS1. In conclusion, this study identifies a novel mutant KRAS-induced metabolic vulnerability that may be targeted via combinatorial inhibition of GLS1 and PFKFB3 to suppress PDAC cell growth.

Perillyl alcohol for pediatric TP53- and RAS-mutated SHH-medulloblastoma: an in vitro and in vivo translational pre-clinical study

PURPOSE

Inhalation of perillyl alcohol (POH) recently emerged as an investigational promising antiglioma strategy. However, little attention has been paid to its therapeutic potential for other brain tumors, especially in the pediatric setting.

METHODS

The effects of POH were explored in medulloblastoma cell models belonging to the SHH variant with activation of RAS (ONS-76) or with TP53 mutations (DAOY and UW402), by means of proliferation and invasion assays. Interactions with methotrexate, thiotepa, or ionizing radiation were also assessed. Mice bearing subcutaneous tumors were treated with intraperitoneal injections. Alternatively, animals with intracranial tumors were exposed to intranasal POH alone or combined with radiation. Tumor growth was measured by bioluminescence. Analyses of cytotoxicity to the nasal cavity were also performed, and the presence of POH in the brain, lungs, and plasma was surveyed through chromatography/mass spectrometry.

RESULTS

POH decreased cell proliferation and colony formation, with conspicuous death, though the invasive capacity was only affected in the NRAS-mutated cell line. Median-drug effect analysis displayed synergistic combinations with methotrexate. Otherwise, POH showed to be a reasonable radiosensitizer. In vivo, intraperitoneal injection significantly decreased tumor volume. However, its inhalation did not affect orthotopic tumors, neither alone or followed by cranial irradiation. Nasal cavity epithelium showed unimportant alterations, though, no traces of POH or its metabolites were detected in tissue samples.

CONCLUSION

POH presents robust in vitro antimedulloblastoma effects and sensitizes cell lines to other conventional therapeutics, reducing tumor volume when administered intraperitoneally. Nevertheless, further improvement of delivery devices and/or drug formulations are needed to better characterize its effectiveness through inhalation.

Targeting p130Cas- and microtubule-dependent MYC regulation sensitizes pancreatic cancer to ERK MAPK inhibition

To identify therapeutic targets for KRAS mutant pancreatic cancer, we conduct a druggable genome small interfering RNA (siRNA) screen and determine that suppression of BCAR1 sensitizes pancreatic cancer cells to ERK inhibition. Integrative analysis of genome-scale CRISPR-Cas9 screens also identify BCAR1 as a top synthetic lethal interactor with mutant KRAS. BCAR1 encodes the SRC substrate p130Cas. We determine that SRC-inhibitor-mediated suppression of p130Cas phosphorylation impairs MYC transcription through a DOCK1-RAC1-β-catenin-dependent mechanism. Additionally, genetic suppression of TUBB3, encoding the βIII-tubulin subunit of microtubules, or pharmacological inhibition of microtubule function decreases levels of MYC protein in a calpain-dependent manner and potently sensitizes pancreatic cancer cells to ERK inhibition. Accordingly, the combination of a dual SRC/tubulin inhibitor with an ERK inhibitor cooperates to reduce MYC protein and synergistically suppress the growth of KRAS mutant pancreatic cancer. Thus, we demonstrate that mechanistically diverse combinations with ERK inhibition suppress MYC to impair pancreatic cancer proliferation.

Netrin G1 Promotes Pancreatic Tumorigenesis through Cancer-Associated Fibroblast-Driven Nutritional Support and Immunosuppression

Pancreatic ductal adenocarcinoma (PDAC) has a poor 5-year survival rate and lacks effective therapeutics. Therefore, it is of paramount importance to identify new targets. Using multiplex data from patient tissue, three-dimensional coculturing in vitro assays, and orthotopic murine models, we identified Netrin G1 (NetG1) as a promoter of PDAC tumorigenesis. We found that NetG1+ cancer-associated fibroblasts (CAF) support PDAC survival, through a NetG1-mediated effect on glutamate/glutamine metabolism. Also, NetG1+ CAFs are intrinsically immunosuppressive and inhibit natural killer cell-mediated killing of tumor cells. These protumor functions are controlled by a signaling circuit downstream of NetG1, which is comprised of AKT/4E-BP1, p38/FRA1, vesicular glutamate transporter 1, and glutamine synthetase. Finally, blocking NetG1 with a neutralizing antibody stunts in vivo tumorigenesis, suggesting NetG1 as potential target in PDAC. SIGNIFICANCE: This study demonstrates the feasibility of targeting a fibroblastic protein, NetG1, which can limit PDAC tumorigenesis in vivo by reverting the protumorigenic properties of CAFs. Moreover, inhibition of metabolic proteins in CAFs altered their immunosuppressive capacity, linking metabolism with immunomodulatory function.See related commentary by Sherman, p. 230.This article is highlighted in the In This Issue feature, p. 211.

Establishment and Characterization of Immortalized Miniature Pig Pancreatic Cell Lines Expressing Oncogenic K-RasG12D

In recent decades, many studies on the treatment and prevention of pancreatic cancer have been conducted. However, pancreatic cancer remains incurable, with a high mortality rate. Although mouse models have been widely used for preclinical pancreatic cancer research, these models have many differences from humans. Therefore, large animals may be more useful for the investigation of pancreatic cancer. Pigs have recently emerged as a new model of pancreatic cancer due to their similarities to humans, but no pig pancreatic cancer cell lines have been established for use in drug screening or analysis of tumor biology. Here, we established and characterized an immortalized miniature pig pancreatic cell line derived from primary pancreatic cells and pancreatic cancer-like cells expressing K-ras^G12D regulated by the human PTF1A promoter. Using this immortalized cell line, we analyzed the gene expression and phenotypes associated with cancer cell characteristics. Notably, we found that acinar-to-ductal transition was caused by K-ras^G12D in the cell line constructed from acinar cells. This may constitute a good research model for the analysis of acinar-to-ductal metaplasia in human pancreatic cancer.

The Key Genes for Perineural Invasion in Pancreatic Ductal Adenocarcinoma Identified With Monte-Carlo Feature Selection Method

Background

Pancreatic ductal adenocarcinoma (PDAC) is the most aggressive form of pancreatic cancer. Its 5-year survival rate is only 3–5%. Perineural invasion (PNI) is a process of cancer cells invading the surrounding nerves and perineural spaces. It is considered to be associated with the poor prognosis of PDAC. About 90% of pancreatic cancer patients have PNI. The high incidence of PNI in pancreatic cancer limits radical resection and promotes local recurrence, which negatively affects life quality and survival time of the patients with pancreatic cancer.

Objectives

To investigate the mechanism of PNI in pancreatic cancer, we analyzed the gene expression profiles of tumors and adjacent tissues from 50 PDAC patients which included 28 patients with perineural invasion and 22 patients without perineural invasion.

Method

Using Monte-Carlo feature selection and Incremental Feature Selection (IFS) method, we identified 26 key features within which 15 features were from tumor tissues and 11 features were from adjacent tissues.

Results

Our results suggested that not only the tumor tissue, but also the adjacent tissue, was informative for perineural invasion prediction. The SVM classifier based on these 26 key features can predict perineural invasion accurately, with a high accuracy of 0.94 evaluated with leave-one-out cross validation (LOOCV).

Conclusion

The in-depth biological analysis of key feature genes, such as TNFRSF14, XPO1, and ATF3, shed light on the understanding of perineural invasion in pancreatic ductal adenocarcinoma.

Physapubescin B enhances the sensitivity of gastric cancer cells to trametinib by inhibiting the STAT3 signaling pathway

Given the poor prognosis of unresectable advanced gastric cancer (GC), novel therapeutic strategies are needed. The mitogen-activated protein kinase (MAPK) signaling cascade, the most frequently activated pathway in GC, plays an important role in tumorigenesis and metastasis. The MAPK/extracellular signal-regulated kinase (ERK) pathway is an attractive therapeutic target for GC. In this study, trametinib, a mitogen-activated protein/extracellular signal-regulated kinase kinase (MEK) inhibitor, reduced the p-ERK level and significantly increased signal transducer and activator of transcription 3 (STAT3) phosphorylation in GC cells, resulting in reduced sensitivity to trametinib. Physapubescin B (PB), a steroidal compound extracted from the plant Physalis pubescens L., inhibited the proliferation and induced the apoptosis of GC cells by suppressing STAT3 phosphorylation. The combination of PB and trametinib suppressed the STAT3 phosphorylation induced by trametinib, and synergistically suppressed gastric tumor growth in vitro and in vivo. Together, these results indicate that inhibition of both MEK and STAT3 may be effective for patients with MAPK/ERK pathway-addicted GC.

CXCR2 signaling promotes secretory cancer-associated fibroblasts in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) remains one of the most challenging malignancies. Desmoplasia and tumor-supporting inflammation are hallmarks of PDAC. The tumor microenvironment contributes significantly to tumor progression and spread. Cancer-associated fibroblasts (CAFs) facilitate therapy resistance and metastasis. Recent reports emphasized the concurrence of multiple subtypes of CAFs with diverse roles, fibrogenic, and secretory. C-X-C motif chemokine receptor 2 (CXCR2) is a chemokine receptor known for its role during inflammation and its adverse role in PDAC. Oncogenic Kras upregulates CXCR2 and its ligands and, thus, contribute to tumor proliferation and immunosuppression. CXCR2 deletion in a PDAC syngeneic mouse model produced increased fibrosis revealing a potential undescribed role of CXCR2 in CAFs. In this study, we demonstrate that the oncogenic Kras-CXCR2 axis regulates the CAFs function in PDAC and contributes to CAFs heterogeneity. We observed that oncogenic Kras and CXCR2 signaling alter CAFs, producing a secretory CAF phenotype with low fibrogenic features; and increased secretion of pro-tumor cytokines and CXCR2 ligands, utilizing the NF-κB activity. Finally, using syngeneic mouse models, we demonstrate that oncogenic Kras is associated with secretory CAFs and that CXCR2 inhibition promotes activation of fibrotic cells (myofibroblasts) and impact tumors in a mutation-dependent manner.

Global analysis of human glycosyltransferases reveals novel targets for pancreatic cancer pathogenesis

BACKGROUND

Several reports have shown the role of glycosylation in pancreatic cancer (PC), but a global systematic screening of specific glycosyltransferases (glycoTs) in its progression remains unknown.

METHODS

We demonstrate a rigorous top-down approach using TCGA-based RNA-Seq analysis, multi-step validation using RT-qPCR, immunoblots and immunohistochemistry. We identified six unique glycoTs (B3GNT3, B4GALNT3, FUT3, FUT6, GCNT3 and MGAT3) in PC pathogenesis and studied their function using CRISPR/Cas9-based KD systems.

RESULTS

Serial metastatic in vitro models using T3M4 and HPAF/CD18, generated in house, exhibited decreases in B3GNT3, FUT3 and GCNT3 expression on increasing metastatic potential. Immunohistochemistry identified clinical significance for GCNT3, B4GALNT3 and MGAT3 in PC. Furthermore, the effects of B3GNT3, FUT3, GCNT3 and MGAT3 were shown on proliferation, migration, EMT and stem cell markers in CD18 cell line. Talniflumate, GCNT3 inhibitor, reduced colony formation and migration in T3M4 and CD18 cells. Moreover, we found that loss of GCNT3 suppresses PC progression and metastasis by downregulating cell cycle genes and β-catenin/MUC4 axis. For GCNT3, proteomics revealed downregulation of MUC5AC, MUC1, MUC5B including many other proteins.

CONCLUSIONS

Collectively, we demonstrate a critical role of O- and N-linked glycoTs in PC progression and delineate the mechanism encompassing the role of GCNT3 in PC.

The Plasma Membrane as a Competitive Inhibitor and Positive Allosteric Modulator of KRas4B Signaling

Mutant Ras proteins are important drivers of human cancers, yet no approved drugs act directly on this difficult target. Over the last decade, the idea has emerged that oncogenic signaling can be diminished by molecules that drive Ras into orientations in which effector-binding interfaces are occluded by the cell membrane. To support this approach to drug discovery, we characterize the orientational preferences of membrane-bound K-Ras4B in 1.45-ms aggregate time of atomistic molecular dynamics simulations. Individual simulations probe active or inactive states of Ras on membranes with or without anionic lipids. We find that the membrane orientation of Ras is relatively insensitive to its bound guanine nucleotide and activation state but depends strongly on interactions with anionic phosphatidylserine lipids. These lipids slow Ras' translational and orientational diffusion and promote a discrete population in which small changes in orientation control Ras' competence to bind multiple regulator and effector proteins. Our results suggest that compound-directed conversion of constitutively active mutant Ras into functionally inactive forms may be accessible via subtle perturbations of Ras' orientational preferences at the membrane surface.

Atypical KRASG12R Mutant Is Impaired in PI3K Signaling and Macropinocytosis in Pancreatic Cancer

Allele-specific signaling by different KRAS alleles remains poorly understood. The KRAS G12R mutation displays uneven prevalence among cancers that harbor the highest occurrence of KRAS mutations: It is rare (∼1%) in lung and colorectal cancers, yet relatively common (∼20%) in pancreatic ductal adenocarcinoma (PDAC), suggesting context-specific properties. We evaluated whether KRASG12R is functionally distinct from the more common KRASG12D- or KRASG12V-mutant proteins (KRASG12D/V). We found that KRASG12D/V but not KRASG12R drives macropinocytosis and that MYC is essential for macropinocytosis in KRASG12D/V- but not KRASG12R-mutant PDAC. Surprisingly, we found that KRASG12R is defective for interaction with a key effector, p110α PI3K (PI3Kα), due to structural perturbations in switch II. Instead, upregulated KRAS-independent PI3Kγ activity was able to support macropinocytosis in KRASG12R-mutant PDAC. Finally, we determined that KRASG12R-mutant PDAC displayed a distinct drug sensitivity profile compared with KRASG12D-mutant PDAC but is still responsive to the combined inhibition of ERK and autophagy. SIGNIFICANCE: We determined that KRASG12R is impaired in activating a key effector, p110α PI3K. As such, KRASG12R is impaired in driving macropinocytosis. However, overexpression of PI3Kγ in PDAC compensates for this deficiency, providing one basis for the prevalence of this otherwise rare KRAS mutant in pancreatic cancer but not other cancers.See related commentary by Falcomatà et al., p. 23.This article is highlighted in the In This Issue feature, p. 1.

Kirsten Rat Sarcoma Viral Oncogene Homologue (KRAS) Mutations in the Occurrence and Treatment of Pancreatic Cancer

Pancreatic cancer is a highly malignant tumor with a 5-year survival rate of less than 6%, and incidence increasing year by year globally. Pancreatic cancer has a poor prognosis and a high recurrence rate, almost the same as the death rate. However, the available effective prevention and treatment measures for pancreatic cancer are still limited. The genome variation is one of the main reasons for the development of pancreatic cancer. In recent years, with the development of gene sequencing technology, in-depth research on pancreatic cancer gene mutation presents that a growing number of genetic mutations are confirmed to be in a close relationship with invasion and metastasis of pancreatic cancer. Among them, KRAS mutation is a special one. Therefore, it is particularly important to understand the mechanism of the KRAS mutation in the occurrence and development of pancreatic cancer, and to explore the method of its transformation into clinical tumor molecular targeted treatment sites, to further improve the therapeutic effect on pancreatic cancer. Therefore, to better design chemical drugs, this review based on the biological functions of KRAS, summarized the types of KRAS mutations and their relationship with pancreatic cancer and included the downstream signaling pathway Raf-MEK-ERK, PI3K-AKT, RalGDS-Ral of KRAS and the current medicinal treatment methods for KRAS mutations. Moreover, drug screening and clinical treatment for KRAS mutated cell and animal models of pancreatic cancer are also reviewed along with the prospect of targeted medicinal chemistry therapy for precision treatment of pancreatic cancer in the future.

The potential role of regulatory microRNAs of RAS/MAPK signaling pathway in the pathogenesis of colorectal cancer

Colorectal cancer (CRC) is the leading cause of cancer death worldwide. Dysregulation of RAS/MAPK signaling axis is frequently found in CRC patients. The RAS/MAPK axis regulates cancer cell proliferation, apoptosis, inflammation, migration, and metastasis. Oncogenic or tumor-suppressor microRNAs (miRNAs) for RAS/MAPK signaling play a key role in the pathogenesis of CRC and are considered as novel potential biomarkers for diagnosis and prognosis of human malignancies. This review summarizes the current knowledge of mechanisms of action of RAS/MAPK miRNAs in the development and progression of CRC for a better understanding and hence a better management of this disease.

Rigidity controls human desmoplastic matrix anisotropy to enable pancreatic cancer cell spread via extracellular signal-regulated kinase 2

It is predicted that pancreatic ductal adenocarcinoma (PDAC) will become the second most lethal cancer in the US by 2030. PDAC includes a fibrous-like stroma, desmoplasia, encompassing most of the tumor mass, which is produced by cancer-associated fibroblasts (CAFs) and includes their cell-derived extracellular matrices (CDMs). Since elimination of desmoplasia has proven detrimental to patients, CDM reprogramming, as opposed to stromal ablation, is therapeutically desirable. Hence, efforts are being made to harness desmoplasia's anti-tumor functions. We conducted biomechanical manipulations, using variations of pathological and physiological substrates in vitro, to culture patient-harvested CAFs and generate CDMs that restrict PDAC growth and spread. We posited that extrinsic modulation of the environment, via substrate rigidity, influences CAF's cell-intrinsic forces affecting CDM production. Substrates used were polyacrylamide gels of physiological (~1.5 kPa) or pathological (~7 kPa) stiffnesses. Results showed that physiological substrates influenced CAFs to generate CDMs similar to normal/control fibroblasts. We found CDMs to be softer than the corresponding underlying substrates, and CDM fiber anisotropy (i.e., alignment) to be biphasic and informed via substrate-imparted morphological CAF aspect ratios. The biphasic nature of CDM fiber anisotropy was mathematically modeled and proposed a correlation between CAF aspect ratios and CDM alignment; regulated by extrinsic and intrinsic forces to conserve minimal free energy. Biomechanical manipulation of CDMs, generated on physiologically soft substrates, leads to reduction in nuclear translocation of pERK1/2 in KRAS mutated pancreatic cells. ERK2 was found essential for CDM-regulated tumor cell spread. In vitro findings correlated with in vivo observations; nuclear pERK1/2 is significantly high in human PDAC samples. The study suggests that altering underlying substrates enable CAFs to remodel CDMs and restrict pancreatic cancer cell spread in an ERK2 dependent manner.

Precision delivery of RAS-inhibiting siRNA to KRAS driven cancer via peptide-based nanoparticles

Over 95% of pancreatic adenocarcinomas (PDACs), as well as a large fraction of other tumor types, such as colorectal adenocarcinoma, are driven by KRAS activation. However, no direct RAS inhibitors exist for cancer therapy. Furthermore, the delivery of therapeutic agents of any kind to PDAC in particular has been hindered by the extensive desmoplasia and resultant drug delivery challenges that accompanies these tumors. Small interfering RNA (siRNA) is a promising modality for anti-neoplastic therapy due to its precision and wide range of potential therapeutic targets. Unfortunately, siRNA therapy is limited by low serum half-life, vulnerability to intracellular digestion, and transient therapeutic effect. We assessed the ability of a peptide based, oligonucleotide condensing, endosomolytic nanoparticle (NP) system to deliver siRNA to KRAS-driven cancers. We show that this peptide-based NP is avidly taken up by cancer cells in vitro, can deliver KRAS-specific siRNA, inhibit KRAS expression, and reduce cell viability. We further demonstrate that this system can deliver siRNA to the tumor microenvironment, reduce KRAS expression, and inhibit pancreatic cancer growth in vivo. In a spontaneous KPPC model of PDAC, this system effectively delivers siRNA to stroma-rich tumors. This model has the potential for translational relevance for patients with KRAS driven solid tumors.

Exploring the Lapse in Druggability: Sequence Analysis, Structural Dynamics and Binding Site Characterization of K-RasG12C Variant, a Feasible Oncotherapeutics Target

BACKGROUND

The difficulty in druggability of K-Ras variant has presented a challenge in the treatment of cancer diseases associated with its dysfunctionality. Despite the identification of different binding sites, limited information exists in the literature about their characteristics. Therefore, identification, crossvalidation and characterization of its druggable sites would aid the design of chemical compounds that will arrest its dysfunctionality related oncogenesis.

OBJECTIVE

This study entails the identification, cross-validation and characterization of K-Ras G12C variant's binding sites for potential druggability, coupled with the elucidation of alterations in 3D conformations and dynamics.

METHOD

Molecular dynamics simulation was carried out on the inactive, the active and the hyperactive K-RasG12Cvariant using the amber software package. The SiteMap software was employed in identifying and characterizing the druggable binding sites while the validation of the binding sites was carried out with the SiteHound and MetaPocket servers.

RESULTS

Four druggable binding sites were identified, validated and characterized based on physicochemical attributes such as size, volume, degree of enclosure or exposure, degree of contact, hydrophobic/hydrophilic character, hydrophobic/hydrophilic balance and hydrogen-bonding features. Conformational studies also revealed that the K-Ras variant exhibited notable structural instability, increased flexibility and a strongly anticorrelated movement compared to the inactive and active wildtype forms.

CONCLUSION

The attributes of the characterized druggable sites will be useful in designing site-specific K-Ras inhibitors for the treatment of K-Ras variant associated cancer diseases.

Combination of ERK and autophagy inhibition as a treatment approach for pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is characterized by KRAS- and autophagy-dependent tumorigenic growth, but the role of KRAS in supporting autophagy has not been established. We show that, to our surprise, suppression of KRAS increased autophagic flux, as did pharmacological inhibition of its effector ERK MAPK. Furthermore, we demonstrate that either KRAS suppression or ERK inhibition decreased both glycolytic and mitochondrial functions. We speculated that ERK inhibition might thus enhance PDAC dependence on autophagy, in part by impairing other KRAS- or ERK-driven metabolic processes. Accordingly, we found that the autophagy inhibitor chloroquine and genetic or pharmacologic inhibition of specific autophagy regulators synergistically enhanced the ability of ERK inhibitors to mediate antitumor activity in KRAS-driven PDAC. We conclude that combinations of pharmacologic inhibitors that concurrently block both ERK MAPK and autophagic processes that are upregulated in response to ERK inhibition may be effective treatments for PDAC.

Structural centrosome aberrations sensitize polarized epithelia to basal cell extrusion

Centrosome aberrations disrupt tissue architecture and may confer invasive properties to cancer cells. Here we show that structural centrosome aberrations, induced by overexpression of either Ninein-like protein (NLP) or CEP131/AZI1, sensitize polarized mammalian epithelia to basal cell extrusion. While unperturbed epithelia typically dispose of damaged cells through apical dissemination into luminal cavities, certain oncogenic mutations cause a switch in directionality towards basal cell extrusion, raising the potential for metastatic cell dissemination. Here we report that NLP-induced centrosome aberrations trigger the preferential extrusion of damaged cells towards the basal surface of epithelial monolayers. This switch in directionality from apical to basal dissemination coincides with a profound reorganization of the microtubule cytoskeleton, which in turn prevents the contractile ring repositioning that is required to support extrusion towards the apical surface. While the basal extrusion of cells harbouring NLP-induced centrosome aberrations requires exogenously induced cell damage, structural centrosome aberrations induced by excess CEP131 trigger the spontaneous dissemination of dying cells towards the basal surface from MDCK cysts. Thus, similar to oncogenic mutations, structural centrosome aberrations can favour basal extrusion of damaged cells from polarized epithelia. Assuming that additional mutations may promote cell survival, this process could sensitize epithelia to disseminate potentially metastatic cells.

LMP1 and 2A Induce the Expression of Nrf2 Through Akt Signaling Pathway in Epstein-Barr Virus-Transformed B Cells

The transcription factor Nrf2, which regulates the expression of antioxidant and cytoprotective enzymes, contributes to cell proliferation and resistance to chemotherapy. Nrf2 is also dysregulated in many cancers such as lung, head and neck, and breast cancers, but its role in Epstein-Barr virus (EBV)–transformed B cells is still not understood. Here, we investigated EBV infection-induced Nrf2 activation in B cells by analyzing translocation of Nrf2 from the cytosol to the nucleus. In addition, we confirmed expression of the target genes in response to increased Nrf2 activation in EBV-transformed B cells. We demonstrated that knockdown of LMP1 and 2A blocks the translocation of Nrf2 to the nucleus and reduces ROS production in EBV-transformed B cells. Further, we showed that inhibition of Akt prevents Nrf2 activation. Moreover, knockdown of Nrf2 induces apoptotic cell death in EBV-transformed B cells. In conclusion, our study demonstrates that Nrf2 promotes proliferation of EBV-transformed B cells through the EBV-related proteins LMP1 and 2A and Akt signaling, implicating Nrf2 as a potential molecular target for EBV-associated disease.

The Modulatory Role of MicroRNA-873 in the Progression of KRAS-Driven Cancers

KRAS is one of the most frequently mutated proto-oncogenes in pancreatic ductal adenocarcinoma (PDAC) and aberrantly activated in triple-negative breast cancer (TNBC). A profound role of microRNAs (miRNAs) in the pathogenesis of human cancer is being uncovered, including in cancer therapy. Using in silico prediction algorithms, we identified miR-873 as a potential regulator of KRAS, and we investigated its role in PDAC and TNBC. We found that reduced miR-873 expression is associated with shorter patient survival in both cancers. miR-873 expression is significantly repressed in PDAC and TNBC cell lines and inversely correlated with KRAS levels. We demonstrate that miR-873 directly bound to the 3′ UTR of KRAS mRNA and suppressed its expression. Notably, restoring miR-873 expression induced apoptosis; recapitulated the effects of KRAS inhibition on cell proliferation, colony formation, and invasion; and suppressed the activity of ERK and PI3K/AKT, while overexpression of KRAS rescued the effects mediated by miR-873. Moreover, in vivo delivery of miR-873 nanoparticles inhibited KRAS expression and tumor growth in PDAC and TNBC tumor models. In conclusion, we provide the first evidence that miR-873 acts as a tumor suppressor by targeting KRAS and that miR-873-based gene therapy may be a therapeutic strategy in PDAC and TNBC.

MicroRNA‑143‑3p suppresses cell growth and invasion in laryngeal squamous cell carcinoma via targeting the k‑Ras/Raf/MEK/ERK signaling pathway

MicroRNAs (miRNAs or miRs) have been identified as an important regulator in carcinogenesis and other pathological processes. However, the molecular mechanism underlying the function of miRNAs in the progression and development of laryngeal squamous cell carcinoma (LSCC) remains to be fully elucidated. In the present study, the miRNA expression pattern in LSCC tissues was profiled using miRNA microarray analysis. It was found that a large set of miRNAs are aberrantly expressed in LSCC tissues and that miR‑143‑3p was the most markedly downregulated compared with normal tissues. The low expression of miR‑143‑3p was associated with poor prognosis in LSCC. The overexpression of miR‑143‑3p repressed cellular proliferation and induced apoptosis in vitro, and inhibited tumor growth in vivo. The upregulation of miR‑143‑3p suppressed cell migration and invasion through inhibiting the epithelial‑mesenchymal transition cascade. In addition, it was verified that the oncogene k‑Ras is a target of miR‑143‑3p in LSCC cells, and the suppressive effects of miR‑143‑3p on LSCC cells were abrogated by the overexpression of k‑Ras. It was also revealed that miR‑143‑3p may inhibit cell growth and metastasis through targeting the k‑Ras/Raf/mitogen‑activated protein kinase kinase (MEK)/extracellular signal‑regulated kinase (ERK) signaling pathway. Taken together, the data indicated that the miR‑143‑3p/k‑Ras/Raf/MEK/ERK axis serves a key regulator in the development and progression of LSCC, suggesting that miR‑143‑3p may be a potential prognostic biomarker and therapeutic target in the treatment of LSCC.

Prolonged MEK inhibition leads to acquired resistance and increased invasiveness in KRAS mutant gastric cancer

Gastric cancer (GC) is one of the most common causes of cancer-associated death. However, traditional therapeutic strategies have failed to significantly improve the survival of patient with advanced GC. While KRAS mutations have been found in some patients with gastric cancer, an effective therapy to treat KRAS-driven gastric cancer has not been established yet. To provide a rationale for clinical application of kinase inhibitors targeting RAS pathways, we first determined the sensitivity of GC cell lines harboring KRAS mutations or amplification to RAS pathway inhibitors. We found that MAPK pathway inhibitors (MEKi and ERKi) were more effective than AKT inhibitor, suggesting that KRAS-driven gastric cancer cells are dependent on MAPK pathway for survival. Further, we established a KRAS mutant GC cell line with acquired resistance to MEK inhibitors in order to mimic clinical situation of kinase inhibitor resistance. A comprehensive analysis of tyrosine phosphorylation in receptor tyrosine kinases in combination with small molecule chemical library screening revealed upregulated c-MET phosphorylation in this resistance cell line with elevated sensitivity to c-MET TKI (crizotinib) and PI3K/mTOR dual inhibitor (BEZ235). We also showed that migration and invasion of resistant cells were promoted, and crizotinib and BEZ235 could inhibit this malignant phenotype. Overall, our results indicate that prolonged MAPK pathway inhibition could result in acquired resistance which is associated with increased malignant phenotype in KRAS mutant GC and pharmacological targeting c-MET and PI3K/mTOR could overcome this problem.

KRAS Suppression-Induced Degradation of MYC Is Antagonized by a MEK5-ERK5 Compensatory Mechanism

Our recent ERK1/2 inhibitor analyses in pancreatic ductal adenocarcinoma (PDAC) indicated ERK1/2-independent mechanisms maintaining MYC protein stability. To identify these mechanisms, we determined the signaling networks by which mutant KRAS regulates MYC. Acute KRAS suppression caused rapid proteasome-dependent loss of MYC protein, through both ERK1/2-dependent and -independent mechanisms. Surprisingly, MYC degradation was independent of PI3K-AKT-GSK3β signaling and the E3 ligase FBWX7. We then established and applied a high-throughput screen for MYC protein degradation and performed a kinome-wide proteomics screen. We identified an ERK1/2-inhibition-induced feedforward mechanism dependent on EGFR and SRC, leading to ERK5 activation and phosphorylation of MYC at S62, preventing degradation. Concurrent inhibition of ERK1/2 and ERK5 disrupted this mechanism, synergistically causing loss of MYC and suppressing PDAC growth.

RalB directly triggers invasion downstream Ras by mobilizing the Wave complex

The two Ral GTPases, RalA and RalB, have crucial roles downstream Ras oncoproteins in human cancers; in particular, RalB is involved in invasion and metastasis. However, therapies targeting Ral signalling are not available yet. By a novel optogenetic approach, we found that light-controlled activation of Ral at plasma-membrane promotes the recruitment of the Wave Regulatory Complex (WRC) via its effector exocyst, with consequent induction of protrusions and invasion. We show that active Ras signals to RalB via two RalGEFs (Guanine nucleotide Exchange Factors), RGL1 and RGL2, to foster invasiveness; RalB contribution appears to be more important than that of MAPK and PI3K pathways. Moreover, on the clinical side, we uncovered a potential role of RalB in human breast cancers by determining that RalB expression at protein level increases in a manner consistent with progression toward metastasis. This work highlights the Ras-RGL1/2-RalB-exocyst-WRC axis as appealing target for novel anticancer strategies.

Cancers develop when cells in the body divide rapidly in an uncontroled manner. It is generally possible to cure cancers that remain contained within a small area. However, if the tumor cells start to move, the cancer may spread in the body and become life threatening. Currently, most of the anti-cancer treatments act to reduce the multiplication of these cells, but not their ability to migrate.

A signal protein called Ras stimulates human cells to grow and move around. In healthy cells, the activity of Ras is tightly controled to ensure cells only divide and migrate at particular times, but in roughly 30% of all human cancers, Ras is abnormally active. Ras switches on another protein, named RalB, which is also involved in inappropriate cell migration. Yet, it is not clear how RalB is capable to help Ras trigger the migration of cells.

Zago et al. used an approach called optogenetics to specifically activate the RalB protein in human cells using a laser that produces blue light. When activated, the light-controlled RalB started abnormal cell migration; this was used to dissect which molecules and mechanisms were involved in the process.

Taken together, the experiments showed that, first, Ras ‘turns on’ RalB by changing the location of two proteins that control RalB. Then, the activated RalB regulates the exocyst, a group of proteins that travel within the cell. In turn, the exocyst recruits another group of proteins, named the Wave complex, which is part of the molecular motor required for cells to migrate.

Zago et al. also found that, in patients, the RalB protein was present at abnormally high levels in samples of breast cancer cells that had migrated to another part of the body. Overall, these findings indicate that the role of RalB protein in human cancers is larger than previously thought, and they highlight a new pathway that could be a target for new anti-cancer drugs.

Concurrent HER or PI3K Inhibition Potentiates the Antitumor Effect of the ERK Inhibitor Ulixertinib in Preclinical Pancreatic Cancer Models

Effective treatment for pancreatic ductal adenocarcinoma (PDAC) is an urgent, unmet medical need. Targeting KRAS, the oncogene that is present in >95% of PDAC, is a heavily pursued strategy, but remains unsuccessful in the clinic. Therefore, targeting key effector cascades of KRAS oncoprotein, particularly the mitogenic RAF-MEK-ERK pathway, represents the next best strategy. However, RAF or MEK inhibitors have failed to show clinical efficacy in PDAC. Several studies have shown that cancer cells treated with RAF or MEK inhibitors adopt multiple mechanisms to reactivate ERK signaling. Therefore, development of ERK-specific inhibitors carries the promise to effectively abrogate this pathway. Ulixertinib (or BVD-523) is a first-in-class ERK-specific inhibitor that has demonstrated promising antitumor activity in a phase I clinical trial for advanced solid tumors with NRAS and BRAF mutations, providing a strong rationale to test this inhibitor in PDAC. In this study, we show that ulixertinib effectively inhibits in vitro growth of multiple PDAC lines and potentiates the cytotoxic effect of gemcitabine. Moreover, we found that PDAC cells treated with ulixertinib upregulates the parallel PI3K-AKT pathway through activating the HER/ErbB family proteins. Concurrent inhibition of PI3K or HER proteins synergizes with ulixertinib in suppressing PDAC cell growth in vitro and in vivo Overall, our study provides the preclinical rationale for testing combinations of ulixertinib with chemotherapy or PI3K and HER inhibitors in PDAC patients. Mol Cancer Ther; 17(10); 2144-55. ©2018 AACR.

Targeting Cancer Stem Cells for Chemoprevention of Pancreatic Cancer

Pancreatic ductal adenocarcinoma is one of the deadliest cancers worldwide and the fourth leading cause of cancer-related deaths in United States. Regardless of the advances in molecular pathogenesis and consequential efforts to suppress the disease, this cancer remains a major health problem in United States. By 2030, the projection is that pancreatic cancer will be climb up to be the second leading cause of cancer-related deaths in the United States. Pancreatic cancer is a rapidly invasive and highly metastatic cancer, and does not respond to standard therapies. Emerging evidence supports that the presence of a unique population of cells called cancer stem cells (CSCs) as potential cancer inducing cells and efforts are underway to develop therapeutic strategies targeting these cells. CSCs are rare quiescent cells, and with the capacity to self-renew through asymmetric/symmetric cell division, as well as differentiate into various lineages of cells in the cancer. Studies have been shown that CSCs are highly resistant to standard therapy and also responsible for drug resistance, cancer recurrence and metastasis. To overcome this problem, we need novel preventive agents that target these CSCs. Natural compounds or phytochemicals have ability to target these CSCs and their signaling pathways. Therefore, in the present review article, we summarize our current understanding of pancreatic CSCs and their signaling pathways, and the phytochemicals that target these cells including curcumin, resveratrol, tea polyphenol EGCG (epigallocatechin- 3-gallate), crocetinic acid, sulforaphane, genistein, indole-3-carbinol, vitamin E δ- tocotrienol, Plumbagin, quercetin, triptolide, Licofelene and Quinomycin. These natural compounds or phytochemicals, which inhibit cancer stem cells may prove to be promising agents for the prevention and treatment of pancreatic cancers.

A Landscape of Therapeutic Cooperativity in KRAS Mutant Cancers Reveals Principles for Controlling Tumor Evolution

Combinatorial inhibition of effector and feedback pathways is a promising treatment strategy for KRAS mutant cancers. However, the particular pathways that should be targeted to optimize therapeutic responses are unclear. Using CRISPR/Cas9, we systematically mapped the pathways whose inhibition cooperates with drugs targeting the KRAS effectors MEK, ERK, and PI3K. By performing 70 screens in models of KRAS mutant colorectal, lung, ovarian, and pancreas cancers, we uncovered universal and tissue-specific sensitizing combinations involving inhibitors of cell cycle, metabolism, growth signaling, chromatin regulation, and transcription. Furthermore, these screens revealed secondary genetic modifiers of sensitivity, yielding a SRC inhibitor-based combination therapy for KRAS/PIK3CA double-mutant colorectal cancers (CRCs) with clinical potential. Surprisingly, acquired resistance to combinations of growth signaling pathway inhibitors develops rapidly following treatment, but by targeting signaling feedback or apoptotic priming, it is possible to construct three-drug combinations that greatly delay its emergence.

Status and future directions in the management of pancreatic cancer: potential impact of nanotechnology

Pancreatic ductal adenocarcinoma (PDAC) is typically diagnosed at a late stage, has limited treatments, and patients have poor survival rates. It currently ranks as the seventh leading cause of cancer deaths globally and has increasing rates of diagnosis. Improved PDAC treatment requires the development of innovative, effective, and economical therapeutic drugs. The late stage diagnosis limits options for surgical resection, and traditional PDAC chemotherapeutics correlate with increased organ and hematologic toxicity. In addition, PDAC tumor tissue is dense and highly resistant to many traditional chemotherapeutic applications, making the disease difficult to treat and impeding options for palliative care. New developments in nanotechnology may offer innovative options for targeted PDAC therapeutic drug delivery. Nanotechnology can be implemented using multimodality methods that offer increased opportunities for earlier diagnosis, precision enhanced imaging, targeted long-term tumor surveillance, and controlled drug delivery, as well as improved palliative care and patient comfort. Nanoscale delivery methods have demonstrated the capacity to infiltrate the dense, fibrous tumor tissue associated with PDAC, increasing delivery and effectiveness of chemotherapeutic agents and reducing toxicity through the loading of multiple drug therapies on a single nano delivery vehicle. This review presents an overview of nanoscale drug delivery systems and multimodality carriers at the forefront of new PDAC treatments.

Dependence on the Pyrimidine Biosynthetic Enzyme DHODH Is a Synthetic Lethal Vulnerability in Mutant KRAS-Driven Cancers

Activating KRAS mutations are major oncogenic drivers in multiple tumor types. Synthetic lethal screens have previously been used to identify targets critical for the survival of KRAS mutant cells, but their application to drug discovery has proven challenging, possibly due in part to a failure of monolayer cultures to model tumor biology. Here, we report the results of a high-throughput synthetic lethal screen for small molecules that selectively inhibit the growth of KRAS mutant cell lines in soft agar. Chemoproteomic profiling identifies the target of the most KRAS-selective chemical series as dihydroorotate dehydrogenase (DHODH). DHODH inhibition is shown to perturb multiple metabolic pathways. In vivo preclinical studies demonstrate strong antitumor activity upon DHODH inhibition in a pancreatic tumor xenograft model.

Novel agents for pancreatic ductal adenocarcinoma: emerging therapeutics and future directions

A poor prognosis of pancreatic ductal adenocarcinoma (PDAC) associated with chemoresistance has not changed for the past three decades. A multidisciplinary diagnosis followed by surgery and chemo(radiation)therapy is the main treatment approach. However, gemcitabine- and 5-fluorouracil-based therapies did not present satisfying outcomes. Novel regimens targeting pancreatic cancer cells, the tumor microenvironment, and immunosuppression are emerging. Biomarkers concerning the treatment outcome and patient selection are being discovered in preclinical or clinical studies. Combination therapies of classic chemotherapeutic drugs and novel agents or novel therapeutic combinations might bring hope to the dismal prognosis for PDAC patients.