Mouse models of pancreatic cancer

Pancreatic cancer is one of the most lethal of human malignancies ranking 4th among cancer-related death in the western world and in the United States,and potent therapeutic options are lacking.Although during the last few years there have been important advances in the understanding of the molecular events responsible for the development of pancreatic cancer,currently specific mechanisms of treatment resistance remain poorly understood and new effective systemic drugs need to be developed and probed.In vivo models to study pancreatic cancer and approach this issue remain limited and present different molecular features that must be considered in the studies depending on the purpose to fit special research themes.In the last few years,several genetically engineered mouse models of pancreatic exocrine neoplasia have been developed.These models mimic the disease as they reproduce genetic alterations implicated in the progression of pancreatic cancer.Genetic alterations such as activating mutations in KRas,or TGFb and/or inactivation of tumoral suppressors such as p53,INK4A/ARF BRCA2 and Smad4 are the most common drivers to pancreatic carcinogenesis and have been used to create transgenic mice.These mouse models have a spectrum of pathologic changes,from pancreatic intraepithelial neoplasia to lesions that progress histologically culminating in fully invasive and metastatic disease and represent the most useful preclinical model system.These models can characterize the cellular and molecular pathology of pancreatic neoplasia and cancer and constitute the best tool to investigate new therapeutic approaches,chemopreventive and/or anticancer treatments.Here,we review and update the current mouse models that reproduce different stages of human pancreatic ductal adenocarcinoma and will have clinical relevance in future pancreatic cancer developments.

Antitumor effect of VEGFR2-targeted microbubble destruction with gemcitabine using an endoscopic ultrasound probe:In vivo mouse pancreatic ductal adenocarcinoma model

Background:Ultrasound-targeted microbubble destruction(UTMD)induces cellular inflow of drugs at low intensity,while high intensity eradicates tumor vessels.Since vascular endothelial growth factor receptor 2(VEGFR2)is highly expressed in pancreatic ductal adenocarcinoma(PDAC),VEGFR2-targeted microbubble(MB)might additionally increase the tissue specificity of drugs and thus improve antitumor effects.In addition,fixing the dual pulse intensity could maximize MB properties.This study evaluated the one-off(experiment 1)and cumulative(experiment 2)treatment effect of UTMD by regulating the dual pulse output applied to PDAC using VEGFR2-targeted MB.Methods:C57BL/6 mice inoculated with Pan-02 cells were allocated to five groups:VEGFR2-targeted MB+gemcitabine(GEM),VEGFR2-targeted MB,non-targeted MB+GEM,GEM,and control groups.After injection of GEM or GEM and either VEGFR2-targeted or non-targeted MB,UTMD was applied for several minutes at low intensity followed by high intensity application.In experiment 1,mice were treated by the protocol described above and then euthanized immediately or at the tumor diameter doubling time(TDT).In experiment 2,the same protocol was repeated weekly and mice were euthanized at TDT regardless of protocol completion.Histological analysis by CD31 and VEGFR2 staining provided microvascular density(MVD)and VEGFR2 expression along vessels(VEGFR2v)or intra/peripheral cells(VEGFR2c).Results:In experiment 1,TDT was significantly longer in the VEGFR2-targeted MB+GEM group compared to the non-targeted MB+GEM,GEM,and control groups,while the VEGFR2-targeted MB group showed no statistical significance.MVD and VEGFR2v in the immediate euthanasia was significantly lower in the VEGFR2-targeted MB+GEM and VEGFR2-targeted MB groups than other conditions.In experiment 2,the VEGFR2-targeted MB+GEM group produced significantly longer TDT than the GEM or control groups,whereas the VEGFR2-targeted MB group showed no significant difference.Histology revealed significantly reduced VEGFR2v and VEGFR2c in the VEGFR2-targeted and non-targeted MB+GEM groups,while only VEGFR2v was significantly less in the VEGFR2-targeted MB group.Conclusions:UTMD-mediated GEM therapy with the dual pulse application using VEGFR2-targeted MB substantially suppresses PDCA growth.

Spontaneous regression of pancreatic cancer: Real or a misdiagnosis?

Spontaneous tumor regression has been subject of numerous studies and speculations for many years. This phenomenon is exceptional, but well reported, in some types of tumors, but not in pancreatic cancer. Pancreatic cancer has the worst five-year survival rate of any cancer. Despite numerous molecular studies and clinical approaches, using several mouse models, this cancer responds poorly to the existing chemotherapeutic agents and progress on treatment remains elusive. Although pancreatic cancer tumors seldom undergo spontaneous regression, and some authors take that with skepticism, there are some cases reported in the literature. However, the variability in the description of the reports and technical details could make this process susceptible to misdiagnosis. Distinguishing between different types of pancreatic carcinoma should be taken with caution as they have wide differences in malignant potential. Diseases such as pancreatic benign tumors, insulinomas, or autoimmune pancreatitis could be responsible for this misdiagnosis as a pancreatic cancer. Here we review different cases reported, their clinical characteristics, and possible mechanisms leading to spontaneous regression of pancreatic cancer. We also discuss the possibilities of misdiagnosis.

Adjuvant and neoadjuvant treatment in pancreatic cancer

Pancreatic adenocarcinoma is one of the most aggressive human malignancies,ranking 4th among causes for cancer-related death in the Western world including the United States.Surgical resection offers the only chance of cure,but only 15 to 20 percent of cases are potentially resectable at presentation.Different studies demonstrate and confirm that advanced pancreatic cancer is among the most complex cancers to treat and that these tumors are relatively resistant to chemotherapy and radiotherapy.Currently there is no consensus around the world on what constitutes"standard"adjuvant therapy for pancreatic cancer.This controversy derives from several studies,each fraught with its own limitations.Standards of care also vary somewhat with regard to geography and economy,for instance chemo-radiotherapy followed by chemotherapy or vice versa is considered the optimal therapy in North America while chemotherapy alone is the current standard in Europe.Regardless of the efforts in adjuvant and neoadjuvant improved therapy,the major goal to combat pancreatic cancer is to find diagnostic markers,identifying the disease in a pre-metastatic stage and making a curative treatment accessible to more patients.In this review,authors examined the different therapy options for advanced pancreatic patients in recent years and the future directions in adjuvant and neoadjuvant treatments for these patients.

Alcohol consumption on pancreatic diseases

Although the association between alcohol and pancreatic diseases has been recognized for a long time,the impact of alcohol consumption on pancreatitis and pancreatic cancer(PC)remains poorly defined.Nowadays there is not consensus about the epidemiology and the beverage type,dose and duration of alcohol consumption causing these diseases.The objective of this study was to review the epidemiology described in the literature for pancreatic diseases as a consequence of alcoholic behavior trying to understand the association between dose,type and frequency of alcohol consumption and risk of pancreatitis and PC.The majority of the studies conclude that high alcohol intake was associated with a higher risk of pancreatitis(around 2.5%-3% between heavy drinkers and 1.3%between non drinkers).About 70%of pancreatitis are due to chronic heavy alcohol consumption.Although this incidence rate differs between countries,it is clear that the risk of developing pancreatitis increases with increasing doses of alcohol and the average of alcohol consumption vary since 80 to 150 g/d for 10-15 years.With regard to PC, the role of alcohol consumption remains less clear,and low to moderate alcohol consumption do not appear to be associated with PC risk,and only chronic heavy drinking increase the risk compared with lightly drinkers.In a population of 10%-15%of heavy drinkers, 2%-5%of all PC cases could be attributed to alcohol consumption.However,as only a minority(less than 10%for pancreatitis and 5%for PC)of heavily drinkers develops these pancreatic diseases,there are other predisposing factors besides alcohol involved.Genetic variability and environmental exposures such as smoking and diet modify the risk and should be considered for further investigations.

Embryonic stem cell factors and pancreatic cancer

Pancreatic ductal adenocarcinoma(PDAC),the most common type of pancreatic tumor,is a highly aggressive human cancer with the lowest five-year survival rate of any human maligancy primarily due to its earlymetastasis and lack of response to chemotherapy and radiation.Recent research suggests that PDAC cells comprise a hierarchy of tumor cells that develop around a population of cancer stem cells(CSCs),a small and distinct population of cancer cells that mediates tumoregenesis,metastasis and resistance to standard treatments.Thus,CSCs could be a target for more effective treatment options.Interestingly,pancreatic CSCs are subject to regulation by some of key embryonic stem cell(ESC)transctiption factors abberently expressed in PDAC,such as SOX2,OCT4 and NANOG.ESC transcription factors are important DNA-binding proteins present in both embryonic and adult somatic cells.The critical role of these factors in reprogramming processes makes them essential not only for embryonic development but also tumorigenesis.Here we provide an overview of stem cell transcription factors,particularly SOX2,OCT4,and NANOG,on their expression and function in pancreatic cancer.In contrast to embryonic stem cells,in which OCT4 and SOX2 are tightly regulated and physically interact to regulate a wide spectrum of target genes,de novo SOX2 expression alone in pancreatic cancer cells is sufficient to promote self-renewal,dedifferentiation and imparting stemness characteristics via impacting specific cell cycle regulatory genes and epithelial-mesnechymal transtion driver genes.Thus,targeting ESC factors,particularly SOX2,could be a worthy strategy for pancreatic cancer therapy.

MicroRNAs in biliary diseases

Cholangiopathies are a group of diseases primarily or secondarily affecting bile duct cells, and result in cholangiocyte proliferation, regression, and/or transformation. Their etiopathogenesis may be associated with a broad variety of causes of different nature, which includes genetic, neoplastic, immune-associated, infectious, vascular, and drug-induced alterations, or being idiopathic. miRNAs, small non-coding endogenous RNAs that post-transcriptionally regulate gene expres sion, have been associated with pathophysiological processes in different organs and cell types, and are postulated as potential targets for diagnosis and therapy. In the current manuscript, knowledge regarding the role of miRNAs in the development and/or progression of cholangiopathies has been reviewed and the most relevant findings in this promising field of hepatology have been highlighted.

c-Met in pancreatic cancer stem cells: Therapeutic implications

Pancreatic cancer is the deadliest solid cancer and currently the fourth most frequent cause of cancer-related deaths. Emerging evidence suggests that cancer stem cells (CSCs) play a crucial role in the development and progression of this disease. The identification of CSC markers could lead to the development of new therapeutic targets. In this study, the authors explore the functional role of c-Met in pancreatic CSCs, by analyzing self-renewal with sphere assays and tumorigenicity capacity in NOD SCID mice. They concluded that c-Met is a novel marker for identifying pancreatic CSCs and c-Met high in a higher tumorigenic cancer cell population. Inhibition of c-Met with XL184 blocks self-renewal capacity in pancreatic CSCs. In pancreatic tumors established in NOD SCID mice, c-Met inhibition slowed tumor growth and reduced the population of CSCs, along with preventing the development of metastases.

Enzymatic and metabolic regulation of lysine succinylation

Lysine succinylation(Ksucc),defined as a transfer of a succinyl group to a lysine residue of a protein,is a newly identified protein post-translational modification^1-3.This chemical modification is reversible,dynamic,and evolutionarily conserved^4 where it has been comprehensively studied in both bacterial and mammalian cells^5-7.Numerous proteins involved in the regulation of various cellular and biological processes have been shown to be heavily succinylated^5-7.Emerging clinical data provides evidence that dysregulation of Ksucc is correlated with the development of several diseases,including cardiovascular diseases and cancer^7-9.Therefore,an in-depth understanding of Ksucc and its regulation is important not only for understanding its physiological function but also for developing drug therapies and targeted agents for these diseases.In this review,we highlight some of the recent advances in understanding the role of Ksucc and desuccinylation under physiological and pathological conditions.

All ways lead to Rome: assembly of retromer on membranes with different sorting nexins

In a recent paper published in Science Advances,Leneva et al.1 present cryo-electron tomography structures of assembling metazoan and fungal core retromer complexes(VPS29/VPS35/VPS26)on membranes enriched in Фx(L/M/V)motif(where Ф is a bulky aromatic residue)-containing cargo and sorting nexin 3(SNX3).The structures suggest that retromer forms a conserved arch-like scaffold that can incorporate different types of membrane adaptors and cargoes.More surprisingly,the SNX3-reotrmer complex is sufficient to induce membrane curvature and tabulation,in the absence of classical membrane curvature drivers,such as bin/amphiphysin/rvs-domain-containing sorting nexin protein(SNX-BARs).

Commanding the Commander:structure of a key protein machinery in endosomal trafficking

In a recent study published in Cell1 and two bioRxiv pre-prints,2,3 three studies investigate the structure of the endosomal Commander complex through a combination of X-ray crystal-lography,cryogenic-electron microscopy(Cryo-EM),Alphafold predictions and extensive site-directed mutagenesis(Fig.1a),which sheds lights on the molecular characteristics of this evolutionarily-conserved protein machinery,and enables the mapping of mutations causing X-linked intellectual disability(XILD)and Ritscher-Schinzel syndrome(RSS).When proteins enter the endosomal network,they are either transported to lysosome for degradation,or recycled to the plasma membrane or the trans-Golgi network for reuse.Multiple protein machineries are essential for the process,including Retromer,Commander,and several members of the sorting nexin(SNX)family.Commander genes are highly conserved in metazoa and can be found in almost all tissues and cells.

Resistance to venetoclax and hypomethylating agents in acute myeloid leukemia

Despite the success of the combination of venetoclax with the hypomethylating agents(HMA)decitabine or azacitidine in inducing remission in older,previously untreated patients with acute myeloid leukemia(AML),resistance-primary or secondary-still constitutes a significant roadblock in the quest to prolong the duration of response.Here we review the proposed and proven mechanisms of resistance to venetoclax monotherapy,HMA monotherapy,and the doublet of venetoclax and HMA for the treatment of AML.We approach the mechanisms of resistance to HMAs and venetoclax in the light of the agents’mechanisms of action.We briefly describe potential therapeutic strategies to circumvent resistance to this promising combination,including alternative scheduling or the addition of other agents to the HMA and venetoclax backbone.Understanding the mechanisms of action and evolving resistance in AML remains a priority in order to maximize the benefit from novel drugs and combinations,identify new therapeutic targets,define potential prognostic markers,and avoid treatment failure.