Fibroblast drug scavenging increases intratumoural gemcitabine accumulation in murine pancreas cancer

Ultrasound- and Microbubble-Assisted Gemcitabine Delivery to Pancreatic Cancer Cells

Pancreatic ductal adenocarcinoma (PDAC) is a major cause of cancer death worldwide. Poor drug delivery to tumours is thought to limit chemotherapeutic treatment efficacy. Sonoporation combines ultrasound (US) and microbubbles to increase the permeability of cell membranes. We assessed gemcitabine uptake combined with sonoporation in vitro in three PDAC cell lines (BxPC-3, MIA PaCa-2 and PANC-1). Cells were cultured in hypoxic bioreactors, while gemcitabine incubation ± sonoporation was conducted in cells with operational or inhibited nucleoside membrane transporters. Intracellular active metabolite (dFdCTP), extracellular gemcitabine, and inactive metabolite (dFdU) concentrations were measured with liquid chromatography tandem mass spectrometry. Sonoporation with increasing US intensities resulted in decreasing extracellular gemcitabine concentrations in all three cell lines with inhibited membrane transporters. In cells with inhibited membrane transporters, without sonoporation, dFdCTP concentrations were reduced down to 10% of baseline. Sonoporation partially restored gemcitabine uptake in these cells, as indicated by a moderate increase in dFdCTP concentrations (up to 37% of baseline) in MIA PaCa-2 and PANC-1. In BxPC-3, gemcitabine was effectively inactivated to dFdU, which might represent a protective mechanism against dFdCTP accumulation in these cells. Intracellular dFdCTP concentrations did not change significantly following sonoporation in any of the cell lines with operational membrane transporters, indicating that the gemcitabine activation pathway may have been saturated with the drug. Sonoporation allowed a moderate increase in gemcitabine transmembrane uptake in all three cell lines, but pre-existing nucleoside transporters were the major determinants of gemcitabine uptake and retention.

The life cycle of cancer-associated fibroblasts within the tumour stroma and its importance in disease outcome

The tumour microenvironment (TME) determines vital aspects of tumour development, such as tumour growth, metastases and response to therapy. Cancer-associated fibroblasts (CAFs) are abundant and extremely influential in this process and interact with cellular and matrix TME constituents such as endothelial and immune cells and collagens, fibronectin and elastin, respectively. However, CAFs are also the recipients of signals—both chemical and physical—that are generated by the TME, and their phenotype effectively evolves alongside the tumour mass during tumour progression. Amid a rising clinical interest in CAFs as a crucial force for disease progression, this review aims to contextualise the CAF phenotype using the chronological framework of the CAF life cycle within the evolving tumour stroma, ranging from quiescent fibroblasts to highly proliferative and secretory CAFs. The emergence, properties and clinical implications of CAF activation are discussed, as well as research strategies used to characterise CAFs and current clinical efforts to alter CAF function as a therapeutic strategy.

Establishment and Characterization of Paired Primary Cultures of Human Pancreatic Cancer Cells and Stellate Cells Derived from the Same Tumor

Pancreatic ductal adenocarcinoma (PDAC) is characterized by an extremely poor prognosis, and its treatment remains a challenge. As the existing in vitro experimental models offer only a limited resemblance to human PDAC, there is a strong need for additional research tools to better understand PDAC tumor biology, particularly the impact of the tumor stroma. Here, we report for the first time the establishment and characterization of human PDAC-derived paired primary monolayer cultures of (epithelial) cancer cells (PCCs) and mesenchymal stellate cells (PSCs) derived from the same tumor by the outgrowth method. Characterization of cell morphology, cytostructural, and functional profiles and proteomics-based secretome analysis were performed. All PCCs harbored KRAS and TP53 mutations, and expressed cytokeratin 19, ki-67, and p53, while the expression of EpCAM and vimentin was variable. All PSCs expressed α-smooth muscle actin (α-SMA) and vimentin. PCCs showed a significantly higher growth rate and proliferation than PSCs. Secretome analysis confirmed the distinct nature of PCCs as compared to PSCs and allowed identification of potential molecular regulators of PSC-conditioned medium (PSC-CM)-induced migration of PCCs. Paired primary cultures of PCCs and PSCs derived from the same tumor specimen represent a novel experimental model for basic research in PDAC tumor biology.

Stromal Features of the Primary Tumor Are Not Prognostic in Genetically Engineered Mice of Pancreatic Cancer

The Kras^G12D/+;LSL-Trp53^R172H/+;Pdx-1-Cre (KPC) mouse model is frequently employed for preclinical therapeutic testing, in particular in regard to antistromal therapies. Here, we investigate the prognostic implications of histopathological features that may guide preclinical trial design. Pancreatic tumor tissue from n = 46 KPC mice was quantitatively analyzed using immunohistochemistry and co-immunofluorescence for proliferation (Ki67), mitotic rate (phospho-Histone 3, PHH3), apoptosis (cleaved caspase-3, CC3), collagen content, secreted protein acidic and rich in cysteine (SPARC), hyaluronic acid (HA), and α-smooth muscle actin (α-SMA). Furthermore, mean vessel density (MVD), mean lumen area (MLA), grading, activated stroma index (ASI), and fibroblast-proliferation rate (α-SMA/Ki67) were assessed. Univariate analysis using the Kaplan–Meier estimator and Cox regression model for continuous variables did not show association between survival and any of the analyzed parameters. Spearman correlation demonstrated that desmoplasia was inversely correlated with differentiated tumor grade (ρ = −0.84). Ki67 and PHH3 synergized as proliferation markers (ρ = 0.54), while SPARC expression was positively correlated with HA content (ρ = 0.37). MVD and MLA were correlated with each other (ρ = 0.31), while MLA positively correlated with CC3 (ρ = 0.45). Additionally, increased MVD was correlated with increased fibroblast proliferation rate (α-SMA + Ki67; ρ = 0.36). Our pilot study provides evidence that individual histopathological parameters of the primary tumor of KPC mice are not associated with survival, and may hint at the importance of systemic tumor-related effects such as cachexia.

The Emerging Role of Cytidine Deaminase in Human Diseases: A New Opportunity for Therapy?

The recycling activity of cytidine deaminase (CDA) within the pyrimidine salvage pathway is essential to DNA and RNA synthesis. As such, CDA deficiency can lead to replicative stress, notably in Bloom syndrome. Alternatively, CDA also can deaminate cytidine and deoxycytidine analog-based therapies, such as gemcitabine. Thus, CDA overexpression is often associated with lower systemic, chemotherapy-related, adverse effects but also with resistance to treatment. Considering the increasing interest of CDA in cancer chemoresistance, the aims of this review are to describe CDA structure, regulation of expression, and activity, and to report the therapeutic strategies based on CDA expression that recently emerged for tumor treatment.

Potent Antitumor Activity of Liposomal Irinotecan in an Organoid- and CRISPR-Cas9-Based Murine Model of Gallbladder Cancer

Gallbladder cancer is associated with a dismal prognosis, and accurate in vivo models will be elemental to improve our understanding of this deadly disease and develop better treatment options. We have generated a transplantation-based murine model for gallbladder cancer that histologically mimics the human disease, including the development of distant metastasis. Murine gallbladder–derived organoids are genetically modified by either retroviral transduction or transfection with CRISPR/Cas9 encoding plasmids, thereby allowing the rapid generation of complex cancer genotypes. We characterize the model in the presence of two of the most frequent oncogenic drivers—Kras and ERBB2—and provide evidence that the tumor histology is highly dependent on the driver oncogene. Further, we demonstrate the utility of the model for the preclinical assessment of novel therapeutic approaches by showing that liposomal Irinotecan (Nal-IRI) is retained in tumor cells and significantly prolongs the survival of gallbladder cancer–bearing mice compared to conventional irinotecan.

hENT1 Testing in Pancreatic Ductal Adenocarcinoma: Are We Ready? A Multimodal Evaluation of hENT1 Status

Gemcitabine is still one of the standard chemotherapy regimens for pancreatic ductal adenocarcinoma (PDAC). Gemcitabine uptake into tumor cells is mainly through the human equilibrative nucleoside transport 1 (hENT1). It was therefore proposed as a potential predictive biomarker of gemcitabine efficacy but reports are conflicting, with an important heterogeneity in methods to assess hENT1 expression. A multicenter cohort of 471 patients with a resected PDAC was used to assess simultaneously the predictive value of the 2 best described hENT1 antibodies (10D7G2 and SP120). Three additional antibodies and the predictive value of hENT1 mRNA were also tested on 251 and 302 patients, respectively. hENT1 expression was assessed in 54 patients with matched primary tumors and metastases samples. The 10D7G2 clone was the only hENT1 antibody whose high expression was associated with a prolonged progression free survival and overall survival in patients who received adjuvant gemcitabine. hENT1 mRNA level was also predictive of gemcitabine benefit. hENT1 status was concordant in 83% of the cases with the best concordance in synchronous metastases. The 10D7G2 clone has the best predictive value of gemcitabine benefit in PDAC patients. Since it is not commercially available, hENT1 mRNA level could represent an alternative to assess hENT1 status.

Deoxycytidine Release from Pancreatic Stellate Cells Promotes Gemcitabine Resistance

Pancreatic ductal adenocarcinoma (PDAC) is a leading cause of cancer deaths in the United States. The deoxynucleoside analogue gemcitabine is among the most effective therapies to treat PDAC, however, nearly all patients treated with gemcitabine either fail to respond or rapidly develop resistance. One hallmark of PDAC is a striking accumulation of stromal tissue surrounding the tumor, and this accumulation of stroma can contribute to therapy resistance. To better understand how stroma limits response to therapy, we investigated cell-extrinsic mechanisms of resistance to gemcitabine. Conditioned media from pancreatic stellate cells (PSC), as well as from other fibroblasts, protected PDAC cells from gemcitabine toxicity. The protective effect of PSC-conditioned media was mediated by secretion of deoxycytidine, but not other deoxynucleosides, through equilibrative nucleoside transporters. Deoxycytidine inhibited the processing of gemcitabine in PDAC cells, thus reducing the effect of gemcitabine and other nucleoside analogues on cancer cells. These results suggest that reducing deoxycytidine production in PSCs may increase the efficacy of nucleoside analog therapies. SIGNIFICANCE: This study provides important new insight into mechanisms that contribute to gemcitabine resistance in PDAC and suggests new avenues for improving gemcitabine efficacy.

SPARC dependent collagen deposition and gemcitabine delivery in a genetically engineered mouse model of pancreas cancer

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is characterised by extensive matrix deposition that has been implicated in impaired drug delivery and therapeutic resistance. Secreted protein acidic and rich in cysteine (SPARC) is a matricellular protein that regulates collagen deposition and is highly upregulated in the activated stroma subtype with poor prognosis in PDAC patients.

METHODS

KrasG12D;p48-Cre;SPARC-/- (KC-SPARC-/-) and KrasG12D;p48-Cre;SPARCWT (KC-SPARCWT) were generated and analysed at different stages of carcinogenesis by histological grading, immunohistochemistry for epithelial and stromal markers, survival and preclinical analysis. Pharmacokinetic and pharmacodynamic studies were conducted by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and immunohistochemistry following gemcitabine treatment (100 mg/kg) in vivo.

FINDINGS

Global genetic ablation of SPARC in a KrasG12D driven mouse model resulted in significantly reduced overall and mature collagen deposition around early and advanced pancreatic intraepithelial neoplasia (PanIN) lesions and in invasive PDAC (p < .001). However, detailed pathological scoring and molecular analysis showed no effects on PanIN to PDAC progression, vessel density (CD31), tumour incidence, grading or metastatic frequency. Despite comparable tumour kinetics, ablation of SPARC resulted in a significantly shortened survival in KC-SPARC-/- mice (280 days versus 485 days, p < .03, log-rank-test). Using LC-MS/MS, we show that SPARC dependent collagen deposition does not affect intratumoural gemcitabine accumulation or immediate therapeutic response in tumour bearing KC-SPARCWT and KC-SPARC-/-mice.

INTERPRETATION

Global SPARC ablation reduces the collagen-rich microenvironment in murine PDAC. Moreover, global SPARC depletion did not affect tumour growth kinetics, grading or metastatic frequency. Notably, the dense-collagen matrix did not restrict access of gemcitabine to the tumour. These findings may have direct translational implications in clinical trial design.

NF-κB Dependent Chemokine Signaling in Pancreatic Cancer

Pancreatic cancer is one of the carcinomas with the worst prognoses, as shown by its five-year survival rate of 9%. Although there have been new therapeutic innovations, the effectiveness of these therapies is still limited, resulting in pancreatic ductal adenocarcinoma (PDAC) becoming the second leading cause of cancer-related death in 2020 in the US. In addition to tumor cell intrinsic resistance mechanisms, this disease exhibits a complex stroma consisting of fibroblasts, immune cells, neuronal and vascular cells, along with extracellular matrix, all conferring therapeutic resistance by several mechanisms. The NF-κB pathway is involved in both the tumor cell-intrinsic and microenvironment-mediated therapeutic resistance by regulating the transcription of a plethora of target genes. These genes are involved in nearly all scenarios described as the hallmarks of cancer. In addition to classical regulators of apoptosis, NF-κB regulates the expression of chemokines and their receptors, both in the tumor cells and in cells of the microenvironment. These chemokines mediate autocrine and paracrine loops among tumor cells but also cross-signaling between tumor cells and the stroma. In this review, we will focus on NF-κB-mediated chemokine signaling, with an emphasis on therapy resistance in pancreatic cancer.

Optimization of nanoemulsion containing gemcitabine and evaluation of its cytotoxicity towards human fetal lung fibroblast (MRC5) and human lung carcinoma (A549) cells

BACKGROUND

Gemcitabine (GEM) is a chemotherapeutic agent, which is known to battle cancer but challenging due to its hydrophilic nature. Nanoemulsion is water-in-oil (W/O) nanoemulsion shows potential as a carrier system in delivering gemcitabine to the cancer cell.

METHODS

The behaviour of GEM in MCT/surfactants/NaCl systems was studied in the ternary system at different ratios of Tween 80 and Span 80. The system with surfactant ratio 3:7 of Tween 80 and Span 80 was chosen for further study on the preparation of nanoemulsion formulation due to the highest isotropic region. Based on the selected ternary phase diagram, a composition of F1 was chosen and used for optimization by using the D-optimal mixture design. The interaction variables between medium chain triglyceride (MCT), surfactant mixture Tween 80: Span 80 (ratio 3:7), 0.9 % sodium chloride solution and gemcitabine were evaluated towards particle size as a response.

RESULTS

The results showed that NaCl solution and GEM gave more effects on particle size, polydispersity index and zeta potential of 141.57±0.05 nm, 0.168 and -37.10 mV, respectively. The optimized nanoemulsion showed good stability (no phase separation) against centrifugation test and storage at three different temperatures. The in vitro release of gemcitabine at different pH buffer solution was evaluated. The results showed the release of GEM in buffer pH 6.5 (45.19%) was higher than GEM in buffer pH 7.4 (13.62%). The cytotoxicity study showed that the optimized nanoemulsion containing GEM induced cytotoxicity towards A549 cell and at the same time reduced cytotoxicity towards MRC5 when compared to the control (GEM solution).

Pancreatic ductal adenocarcinoma: biological hallmarks, current status, and future perspectives of combined modality treatment approaches

Pancreatic ductal adenocarcinoma (PDAC) is a highly devastating disease with poor prognosis and rising incidence. Late detection and a particularly aggressive biology are the major challenges which determine therapeutic failure. In this review, we present the current status and the recent advances in PDAC treatment together with the biological and immunological hallmarks of this cancer entity. On this basis, we discuss new concepts combining distinct treatment modalities in order to improve therapeutic efficacy and clinical outcome - with a specific focus on protocols involving radio(chemo)therapeutic approaches.

Preclinical Evaluation of 1,2-Diamino-4,5-Dibromobenzene in Genetically Engineered Mouse Models of Pancreatic Cancer

Background: Pancreatic ductal adenocarcinoma (PDAC) is highly resistant to standard chemo- and radiotherapy. Recently, a new class of non-platinum-based halogenated molecules (called FMD compounds) was discovered that selectively kills cancer cells. Here, we investigate the potential of 1,2-Diamino-4,5-dibromobenzene (2Br-DAB) in combination with standard chemotherapy and radiotherapy in murine and human PDAC. Methods: Cell viability and colony formation was performed in human (Panc1, BxPC3, PaTu8988t, MiaPaCa) and three murine LSL-Kras^G12D/+;LSL-Trp53^R172H/+;Pdx-1-Cre (KPC) pancreatic cancer cell lines. In vivo, preclinical experiments were conducted in LSL-Kras^G12D/+;p48-Cre (KC) and KPC mice using 2Br-DAB (7 mg/kg, i.p.), +/- radiation (10 × 1.8 Gy), gemcitabine (100 mg/kg, i.p.), or a combination. Tumor growth and therapeutic response were assessed by high-resolution ultrasound and immunohistochemistry. Results: 2Br-DAB significantly reduced cell viability in human and murine pancreatic cancer cell lines in a dose-dependent manner. In particular, colony formation in human Panc1 cells was significantly decreased upon 25 µM 2Br-DAB + radiation treatment compared with vehicle control (p = 0.03). In vivo, 2Br-DAB reduced tumor frequency in KC mice. In the KPC model, 2Br-DAB or gemcitabine monotherapy had comparable therapeutic effects. Furthermore, the combination of gemcitabine and 2Br-DAB or 2Br-DAB and 18 Gy irradiation showed additional antineoplastic effects. Conclusions: 2Br-DAB is effective in killing pancreatic cancer cells in vitro. 2Br-DAB was not toxic in vivo, and additional antineoplastic effects were observed in combination with irradiation.

Low expression of SPARC in gastric cancer-associated fibroblasts leads to stemness transformation and 5-fluorouracil resistance in gastric cancer

Background

The aim of the present study was to clarify the correlations between SPARC expression in gastric cancer-associated fibroblasts (GCAFs) and the prognosis of patients with gastric cancer and to elucidate the role of GCAF-derived SPARC in stemness transformation and 5-fluorouracil resistance in gastric cancer.

Methods

One hundred ninety-two patients were enrolled in the present study. SPARC expression levels were evaluated by immunohistochemical staining. Primary GCAFs were obtained and cultured from cancer patients for in vitro study, and a lentivirus infection method was employed to knock down SPARC expression in GCAFs. The stemness phenotype and 5-fluorouracil (5-FU) response of gastric cancer cells were assessed via a 3D co-culture model. The apoptotic status and stemness alterations were monitored by flow cytometry and western blotting. Additionally, label-free quantification proteomics was used to identify the differentially expressed proteins and potential pathways in gastric cancer cells treated with GCAF-derived SPARC.

Results

Low expression of GCAF-derived SPARC was associated with decreased differentiation and reduced 5-year overall survival and was an independent predictive factor for prognosis in gastric cancer. The 3D tumour growth and 5-FU resistance abilities of gastric cancer cells were elevated after treatment with GCAFs with SPARC knockdown relative to these abilities in negative control cells. Additionally, suppressing SPARC expression in GCAFs facilitated the phenotypic alteration of gastric cancer cells towards CD44⁺/CD24⁻ cancer stem cell (CSC)-like cells. Quantification proteomics analysis revealed that the differentially expressed proteins in gastric cancer cells were mainly involved in the AKT/mTOR and MEK/ERK signalling pathways.

Conclusions

SPARC expression in GCAFs is a useful prognostic factor in patients with gastric cancer. Low expression of GCAF-derived SPARC can lead to CSC transformation and 5-FU resistance. Additionally, the AKT/mTOR and MEK/ERK signalling pathways may participate in the malignant process.

Electronic supplementary material

The online version of this article (10.1186/s12935-019-0844-8) contains supplementary material, which is available to authorized users.

Proteomic analysis of gemcitabine-resistant pancreatic cancer cells reveals that microtubule-associated protein 2 upregulation associates with taxane treatment

BACKGROUND

Chemoresistance hampers the treatment of patients suffering from pancreatic ductal adenocarcinoma (PDAC). Here we aimed to evaluate the (phospho)proteome of gemcitabine-sensitive and gemcitabine-resistant PDAC cells to identify novel therapeutic targets and predictive biomarkers.

METHODS

The oncogenic capabilities of gemcitabine-sensitive and resistant PDAC cells were evaluated in vitro and in vivo. Cultured cells were analyzed by label-free proteomics. Differential proteins and phosphopeptides were evaluated by gene ontology and for their predictive or prognostic biomarker potential with immunohistochemistry of tissue microarrays.

RESULTS

Gemcitabine-resistant cells had increased potential to induce xenograft tumours (p value < 0.001). Differential analyses showed that proteins associated with gemcitabine resistance are correlated with microtubule regulation. Indeed, gemcitabine-resistant cells displayed an increased sensitivity for paclitaxel in vitro (p < 0.001) and nab-paclitaxel had a strong anti-tumour efficacy in vivo. Microtubule-associated protein 2 (MAP2) was found to be highly upregulated (p = 0.002, fold change = 10) and phosphorylated in these resistant cells. Expression of MAP2 was correlated with a poorer overall survival in patients treated with gemcitabine in the palliative (p = 0.037) and adjuvant setting (p = 0.014).

CONCLUSIONS

These data show an explanation as to why the combination of gemcitabine with nab-paclitaxel is effective in PDAC patients. The identified gemcitabine-resistance marker, MAP2, emerged as a novel prognostic marker in PDAC patients treated with gemcitabine and warrants further clinical investigation.

Role of c-MET Inhibitors in Overcoming Drug Resistance in Spheroid Models of Primary Human Pancreatic Cancer and Stellate Cells

Pancreatic stellate cells (PSCs) are a key component of tumor microenvironment in pancreatic ductal adenocarcinoma (PDAC) and contribute to drug resistance. c-MET receptor tyrosine kinase activation plays an important role in tumorigenesis in different cancers including PDAC. In this study, effects of PSC conditioned medium (PCM) on c-MET phosphorylation (by immunocytochemistry enzyme-linked immunosorbent assay (ELISA)) and drug response (by sulforhodamine B assay) were investigated in five primary PDAC cells. In novel 3D-spheroid co-cultures of cyan fluorescence protein (CFP)-firefly luciferase (Fluc)-expressing primary human PDAC cells and green fluorescence protein (GFP)-expressing immortalized PSCs, PDAC cell growth and chemosensitivity were examined by luciferase assay, while spheroids' architecture was evaluated by confocal microscopy. The highest phospho-c-MET expression was detected in PDAC5 and its subclone sorted for "stage specific embryonic antigen-4" (PDAC5 (SSEA4)). PCM of cells pre-incubated with PDAC conditioned medium, containing increased hepatocyte growth factor (HGF) levels, made PDAC cells significantly more resistant to gemcitabine, but not to c-MET inhibitors. Hetero-spheroids containing both PSCs and PDAC5 (SSEA4) cells were more resistant to gemcitabine compared to PDAC5 (SSEA4) homo-spheroids. However, c-MET inhibitors (tivantinib, PHA-665752 and crizotinib) were equally effective in both spheroid models. Experiments with primary human PSCs confirmed the main findings. In conclusion, we developed spheroid models to evaluate PSC-PDAC reciprocal interaction, unraveling c-MET inhibition as an important therapeutic option against drug resistant PDAC.

Fibroblasts in Pancreatic Ductal Adenocarcinoma: Biological Mechanisms and Therapeutic Targets

The desmoplastic reaction of pancreas cancer may begin as a wound healing response to the nascent neoplasm, but it soon creates an insidious shelter that can sustain the growing tumor and rebuff therapy. Among the many cell types subverted by transformed epithelial cells, fibroblasts are recruited and activated to lay a foundation of extracellular matrix proteins and glycosaminoglycans that alter tumor biophysics and signaling. Their near-universal presence in pancreas cancer and ostensible support of disease progression make fibroblasts attractive therapeutic targets. More recently, however, it has also become apparent that diverse subpopulations of fibroblasts with distinct phenotypes and secretomes inhabit the stroma, and that targeted depletion of particular fibroblast subsets could either provide substantial therapeutic benefit or accelerate disease progression. An improved characterization of these fibroblast subtypes, along with their potential relationships to tumor subtypes and mutational repertoires, is needed in order to make anti-fibroblast therapies clinically viable.

Cancer-associated fibroblasts in gastrointestinal cancer

The tumour microenvironment, also termed the tumour stroma or tumour mesenchyme, includes fibroblasts, immune cells, blood vessels and the extracellular matrix and substantially influences the initiation, growth and dissemination of gastrointestinal cancer. Cancer-associated fibroblasts (CAFs) are one of the critical components of the tumour mesenchyme and not only provide physical support for epithelial cells but also are key functional regulators in cancer, promoting and retarding tumorigenesis in a context-dependent manner. In this Review, we outline the emerging understanding of gastrointestinal CAFs with a particular emphasis on their origin and heterogeneity, as well as their function in cancer cell proliferation, tumour immunity, angiogenesis, extracellular matrix remodelling and drug resistance. Moreover, we discuss the clinical implications of CAFs as biomarkers and potential targets for prevention and treatment of patients with gastrointestinal cancer.

Stress responses in stromal cells and tumor homeostasis

In most (if not all) solid tumors, malignant cells are outnumbered by their non-malignant counterparts, including immune, endothelial and stromal cells. However, while the mechanisms whereby cancer cells adapt to microenvironmental perturbations have been studied in great detail, relatively little is known on stress responses in non-malignant compartments of the tumor microenvironment. Here, we discuss the mechanisms whereby cancer-associated fibroblasts and other cellular components of the tumor stroma react to stress in the context of an intimate crosstalk with malignant, endothelial and immune cells, and how such crosstalk influences disease progression and response to treatment.

Cancer-associated fibroblasts-derived IL-8 mediates resistance to cisplatin in human gastric cancer

Chemoresistance remains the major obstacle to achieve optimal prognosis in gastric cancer patients, and the underlying molecular mechanisms of cancer-associated fibroblasts (CAFs) in gastric cancer chemoresistance remain poorly understood. We identified the high pretherapeutical serum IL-8 level in gastric cancer patients was associated with poor response to platinum-based therapy, and it increased gradually during neoadjuvant chemotherapy and it decreased after radical surgery. Immunohistochemistry assays showed that IL-8 was highly expressed in gastric cancer tissues in chemoresistant patients, and located in CAFs. Primary CAFs produced more IL-8 than the corresponding normal fibroblasts, and human stomach fibroblast line Hs738 secreted more IL-8 after co-cultured with conditioned media from AGS or MGC-803 cells. IL-8 increased the IC50 of cisplatin (CDDP) in AGS or MGC-803 in vitro. Simultaneously, IL-8 treatment enhanced the expression of PI3K, phosphorylated-AKT (p-AKT), phosphorylated-IKb (p-IKb), phosphorylated-p65 (p-p65) and ABCB1, and ABCB1 and p-p65 were overexpressed in tumor tissues of chemoresistant patients. Collectively, CAFs derived IL-8 promotes chemoresistance in human gastric cancer via NF-κB activation and ABCB1 up-regulation. Our study provides a novel strategy to improve the chemotherapeutical efficacy and the prognosis of gastric cancer.

Ex vivo organotypic culture system of precision-cut slices of human pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) has a poor prognosis, which is mainly due to late diagnosis and profound resistance to treatment. The latter is to a large extent attributed to the tumor stroma that is exceedingly prominent in PDAC and engages in complex interactions with the cancer cells. Hence, relevant preclinical models of PDAC should also include the tumor stroma. We herein describe the establishment and functional validation of an ex vivo organotypic culture of human PDAC that is based on precision-cut tissue slices from surgical specimens and reproducibly recapitulates the complex cellular and acellular composition of PDAC, including its microenvironment. The cancer cells, tumor microenvironment and interspersed remnants of nonneoplastic pancreas contained in these 350 µm thick slices maintained their structural integrity, phenotypic characteristics and functional activity when in culture for at least 4 days. In particular, tumor cell proliferation persisted and the grade of differentiation and morphological phenotype remained unaltered. Cultured tissue slices were metabolically active and responsive to rapamycin, an mTOR inhibitor. This culture system is to date the closest surrogate to the parent carcinoma and harbors great potential as a drug sensitivity testing system for the personalized treatment of PDAC.

Cytosolic 5'-nucleotidase 1A is overexpressed in pancreatic cancer and mediates gemcitabine resistance by reducing intracellular gemcitabine metabolites

BACKGROUND

Cytosolic 5'-nucleotidase 1A (NT5C1A) dephosphorylates non-cyclic nucleoside monophosphates to produce nucleosides and inorganic phosphates. Here, we investigate NT5C1A expression in pancreatic ductal adenocarcinoma (PDAC) and its impact on gemcitabine metabolism and therapeutic efficacy.

METHODS

NT5C1A expression was determined by semiquantitative immunohistochemistry using tissue microarrays. Gemcitabine metabolites and response were assessed in several human and murine PDAC cell lines using crystal violet assays, Western blot, viability assays, and liquid chromatography tandem mass-spectrometry (LC-MS/MS).

FINDINGS

NT5C1A was strongly expressed in tumor cells of a large subgroup of resected PDAC patients in two independent patient cohorts (44-56% score 2 and 8-26% score 3, n = 414). In contrast, NT5C1A was expressed at very low levels in the tumor stroma, and neither stromal nor tumoral expression was a prognostic marker for postoperative survival. In vitro, NT5C1A overexpression increased gemcitabine resistance by reducing apoptosis levels and significantly decreased intracellular amounts of cytotoxic dFdCTP in +NT5C1A tumor cells. Co-culture experiments with conditioned media from +NT5C1A PSCs improved gemcitabine efficacy in tumor cells. In vivo, therapeutic efficacy of gemcitabine was significantly decreased and serum levels of the inactive gemcitabine metabolite dFdU significantly increased in mice bearing NT5C1A overexpressing tumors.

INTERPRETATION

NT5C1A is robustly expressed in tumor cells of resected PDAC patients. Moreover, NT5C1A mediates gemcitabine resistance by decreasing the amount of intracellular dFdCTP, leading to reduced tumor cell apoptosis and larger pancreatic tumors in mice. Further studies should clarify the role of NT5C1A as novel predictor for gemcitabine treatment response in patients with PDAC.

Targeting Pancreatic Stellate Cells in Cancer

Pancreatic stellate cells (PSCs) are the major contributor to the aggressive, metastatic, and resilient nature of pancreatic ductal adenocarcinoma (PDAC), which has a poor prognosis with a 5-year survival rate of 8%. PSCs constitute more than 50% of the tumor stroma in PDAC, where they induce extensive desmoplasia by secreting abundant extracellular matrix (ECM) proteins. In addition, they establish dynamic crosstalk with cancer cells and other stromal cells, which collectively supports tumor progression via various inter- and intracellular pathways. These cellular interactions and associated pathways may reveal novel therapeutic opportunities against this unmet clinical problem. In this review article, we discuss the role of PSCs in inducing tumor progression, their crosstalk with other cells, and therapeutic strategies to target PSCs.

Commonly Used Pancreatic Stellate Cell Cultures Differ Phenotypically and in Their Interactions with Pancreatic Cancer Cells

Activated pancreatic stellate cells (PSCs) play a central role in the tumor stroma of pancreatic ductal adenocarcinoma (PDAC). Given the limited availability of patient-derived PSCs from PDAC, immortalized PSC cell lines of murine and human origin have been established; however, it is not elucidated whether differences in species, organ disease status, donor age, and immortalization alter the PSC phenotype and behavior compared to that of patient-derived primary PSC cultures. Therefore, a panel of commonly used PSC cultures was examined for important phenotypical and functional features: three primary cultures from human PDAC, one primary from normal human pancreas, and three immortalized (one from human, two from murine pancreas). Growth rate was considerably lower in primary PSCs from human PDAC. Basal collagen synthesis varied between the PSC cultures, and TGF-β stimulation increased collagen synthesis only in non-immortalized cultures. Differences in secretome composition were observed along with a divergence in the DNA synthesis, migration, and response to gemcitabine of PDAC cell lines that were grown in conditioned medium from the various PSC cultures. The findings reveal considerable differences in features and functions that are key to PSCs and in the interactions with PDAC. These observations may be relevant to researchers when selecting the most appropriate PSC culture for their experiments.

Stromal biology and therapy in pancreatic cancer: ready for clinical translation?

Pancreatic ductal adenocarcinoma (PDA) is notoriously aggressive and hard to treat. The tumour microenvironment (TME) in PDA is highly dynamic and has been found to promote tumour progression, metastasis niche formation and therapeutic resistance. Intensive research of recent years has revealed an incredible heterogeneity and complexity of the different components of the TME, including cancer-associated fibroblasts, immune cells, extracellular matrix components, tumour vessels and nerves. It has been hypothesised that paracrine interactions between neoplastic epithelial cells and TME compartments may result in either tumour-promoting or tumour-restraining consequences. A better preclinical understanding of such complex and dynamic network systems is required to develop more powerful treatment strategies for patients. Scientific activity and the number of compelling findings has virtually exploded during recent years. Here, we provide an update of the most recent findings in this area and discuss their translational and clinical implications for basic scientists and clinicians alike.

Ultrasonic cavitation induces necrosis and impairs growth in three-dimensional models of pancreatic ductal adenocarcinoma

INTRODUCTION

Pancreatic ductal adenocarcinoma (PDAC) is a rapidly increasing cause of mortality whose dismal prognosis is mainly due to overwhelming chemoresistance. New therapeutic approaches include physical agents such as ultrasonic cavitation, but clinical applications require further insights in the mechanisms of cytotoxicity. 3-D in vitro culture models such as spheroids exploit realistic spatial, biochemical and cellular heterogeneity that may bridge some of the experimental gap between conventional in vitro and in vivo experiments.

PURPOSE

To assess the feasibility and efficiency of inertial cavitation associated or not with chemotherapy, in a spheroid model of PDAC.

METHODS

We used DT66066 cells, derived from a genetically-engineered murine PDAC, isolated from KPC-transgenic mice (LSL-KrasG12D/+; LSL-Trp53R172H/+; Pdx-1- Cre). Spheroids were obtained by either a standard centrifugation-based method, or by using a magnetic nano-shuttle method allowing the formation of spheroids within 24 hours and facilitating their handling. The spheroids were exposed to ultrasonic inertial cavitation in a specially designed setup. Eight or nine spheroids were analyzed for each of 4 conditions: control, gemcitabine alone, US cavitation alone, US cavitation + gemcitabine. Five US inertial cavitation indexes, corresponding to increased US intensities, were evaluated. The effectiveness of treatment was assessed after 24 hours with the following criteria: spheroid size (growth), ratio of phase S-entered cells (proliferation), proportion of cells in apoptosis or necrosis (mortality). These parameters were assessed by quantitative immunofluorescence techniques.

RESULTS

The 3D culture model presented excellent reproducibility. Cavitation induced a significant decrease in the size of spheroids, an effect significantly correlated to an increasing cavitation index (p < 0.0001). The treatment induced cell death whose predominant mechanism was necrosis (p < 0.0001). There was a tendency to a synergistic effect of US cavitation and gemcitabine at 5μM concentration, however significant in only one of the cavitation indexes used (p = 0. 013).

CONCLUSION

Ultrasonic inertial cavitation induced a significant reduction of tumor growth in a spheroid model of PDAC., with necrosis rather than apoptosis as a Cell dominant mechanism of cell death. More investigations are needed to understand the potential role of inertial cavitation in overcoming chemoresistance.

Blocking Autophagy in Cancer-Associated Fibroblasts Supports Chemotherapy of Pancreatic Cancer Cells

In this study we evaluated the interaction of pancreatic cancer cells, cancer-associated fibroblasts, and distinct drugs such as α-cyano-4-hydroxycinnamate, metformin, and gemcitabine. We observed that α-cyano-4-hydroxycinnamate as monotherapy or in combination with metformin could significantly induce collagen I deposition within the stromal reaction. Subsequently, we demonstrated that cancer-associated fibroblasts impaired the anti-proliferation efficacy of α-cyano-4-hydroxycinnamate, metformin and gemcitabine. Interestingly, inhibition of autophagy in these fibroblasts can augment the anti-proliferation effect of these chemotherapeutics in vitro and can reduce the tumor weight in a syngeneic pancreatic cancer model. These results suggest that inhibiting autophagy in cancer-associated fibroblasts may contribute to strategies targeting cancer.

Silencing of caveolin-1 in fibroblasts as opposed to epithelial tumor cells results in increased tumor growth rate and chemoresistance in a human pancreatic cancer model

Caveolin-1 (Cav-1) expression has been shown to be associated with tumor growth and resistance to chemotherapy in pancreatic cancer. The primary aim of this study was to explore the significance of Cav-1 expression in pancreatic cancer cells as compared to fibroblasts in relation to cancer cell proliferation and chemoresistance, both in vitro and in vivo, in an immunodeficient mouse model. We also aimed to evaluate the immunohistochemical expression of Cav-1 in the epithelial and stromal component of pancreatic cancer tissue specimens. The immunohistochemical staining of poorly differentiated tissue sections revealed a strong and weak Cav-1 expression in the epithelial tumor cells and stromal fibroblasts, respectively. Conversely, the well-differentiated areas were characterized by a weak epithelial Cav-1 expression. Cav-1 downregulation in cancer cells resulted in an increased proliferation in vitro; however, it had no effect on chemoresistance and growth gain in vivo. By contrast, the decreased expression of Cav-1 in fibroblasts resulted in a growth advantage and the chemo-resistance of cancer cells when they were co-injected into immunodeficient mice to develop mixed fibroblast/cancer cell xenografts. On the whole, the findings of this study suggest that the downregulation of Cav-1 in fibroblasts is associated with an increased tumor proliferation rate in vivo and chemoresistance. Further studies are warranted to explore whether the targeting of Cav-1 in the stroma may represent a novel therapeutic approach in pancreatic cancer.

Typing of pancreatic cancer-associated fibroblasts identifies different subpopulations

AIM

To determine whether it is possible to identify different immune phenotypic subpopulations of cancer-associated fibroblasts (CAFs) in pancreatic cancer (PC).

METHODS

We defined four different stromal compartments in surgical specimens with PC: The juxtatumoural, peripheral, lobular and septal stroma. Tissue microarrays were produced containing all pre-defined PC compartments, and the expression of 37 fibroblast (FB) and 8 extracellular matrix (ECM) markers was evaluated by immunohistochemistry, immunofluorescence (IF), double-IF, and/or in situ hybridization. The compartment-specific mean labelling score was determined for each marker using a four-tiered scoring system. DOG1 gene expression was examined by quantitative reverse transcription PCR (qPCR).

RESULTS

CD10, CD271, cytoglobin, DOG1, miR-21, nestin, and tenascin C exhibited significant differences in expression profiles between the juxtatumoural and peripheral compartments. The expression of CD10, cytoglobin, DOG1, nestin, and miR-21 was moderate/strong in juxtatumoural CAFs (j-CAFs) and barely perceptible/weak in peripheral CAFs (p-CAFs). The upregulation of DOG1 gene expression in PC compared to normal pancreas was verified by qPCR. Tenascin C expression was strong in the juxtatumoural ECM and barely perceptible/weak in the peripheral ECM. CD271 expression was barely perceptible in j-CAFs but moderate in the other compartments. Galectin-1 was stronger expressed in j-CAFs vs septal fibroblasts, PDGF-Rβ, tissue transglutaminase 2, and hyaluronic acid were stronger expressed in lobular fibroblasts vs p-CAFs, and plectin-1 was stronger expressed in j-CAFs vs l-FBs. The expression of the remaining 33 markers did not differ significantly when related to the quantity of CAFs/FBs or the amount of ECM in the respective compartments.

CONCLUSION

Different immune phenotypic CAF subpopulations can be identified in PC, using markers such as cytoglobin, CD271, and miR-21. Future studies should determine whether CAF subpopulations have different functional properties.

IL1-Induced JAK/STAT Signaling Is Antagonized by TGFβ to Shape CAF Heterogeneity in Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is poorly responsive to therapies and histologically contains a paucity of neoplastic cells embedded within a dense desmoplastic stroma. Within the stroma, cancer-associated fibroblasts (CAF) secrete tropic factors and extracellular matrix components, and have been implicated in PDAC progression and chemotherapy resistance. We recently identified two distinct CAF subtypes characterized by either myofibroblastic or inflammatory phenotypes; however, the mechanisms underlying their diversity and their roles in PDAC remain unknown. Here, we use organoid and mouse models to identify TGFβ and IL1 as tumor-secreted ligands that promote CAF heterogeneity. We show that IL1 induces LIF expression and downstream JAK/STAT activation to generate inflammatory CAFs and demonstrate that TGFβ antagonizes this process by downregulating IL1R1 expression and promoting differentiation into myofibroblasts. Our results provide a mechanism through which distinct fibroblast niches are established in the PDAC microenvironment and illuminate strategies to selectively target CAFs that support tumor growth. SIGNIFICANCE: Understanding the mechanisms that determine CAF heterogeneity in PDAC is a prerequisite for the rational development of approaches that selectively target tumor-promoting CAFs. Here, we identify an IL1-induced signaling cascade that leads to JAK/STAT activation and promotes an inflammatory CAF state, suggesting multiple strategies to target these cells in vivo. See related commentary by Ling and Chiao, p. 173. This article is highlighted in the In This Issue feature, p. 151.

The impact of cancer-associated fibroblasts on major hallmarks of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) constitutes one of the most challenging lethal tumors and has a very poor prognosis. In addition to cancer cells, the tumor microenvironment created by a repertoire of resident and recruited cells and the extracellular matrix also contribute to the acquisition of hallmarks of cancer. Among these factors, cancer-associated fibroblasts (CAFs) are critical components of the tumor microenvironment. CAFs originate from the activation of resident fibroblasts and pancreatic stellate cells, the differentiation of bone marrow-derived mesenchymal stem cells and epithelial-to-mesenchymal transition. CAFs acquire an activated phenotype via various cytokines and promote tumor proliferation and growth, accelerate invasion and metastasis, induce angiogenesis, promote inflammation and immune destruction, regulate tumor metabolism, and induce chemoresistance; these factors contribute to the acquisition of major hallmarks of PDAC. Therefore, an improved understanding of the impact of CAFs on the major hallmarks of PDAC will highlight the diagnostic and therapeutic values of these targeted cells.

GRP78-mediated antioxidant response and ABC transporter activity confers chemoresistance to pancreatic cancer cells

Chemoresistance is a major therapeutic challenge that plays a role in the poor statistical outcomes in pancreatic cancer. Unfolded protein response (UPR) is one of the homeostasis mechanisms in cancer cells that have been correlated with chemoresistance in a number of cancers including pancreatic cancer. In this study, we show that modulating glucose regulatory protein 78 (GRP78), the master regulator of the UPR, can have a profound effect on multiple pathways that mediate chemoresistance. Our study showed for the first time that silencing GRP78 can diminish efflux activity of ATP-binding cassette (ABC) transporters, and it can decrease the antioxidant response resulting in an accumulation of reactive oxygen species (ROS). We also show that these effects can be mediated by the activity of specificity protein 1 (SP1), a transcription factor overexpressed in pancreatic cancer. Thus, inhibition of SP1 negatively affects the UPR, deregulates the antioxidant response of NRF2, as well as ABC transporter activity by inhibiting GRP78-mediated ER homeostasis. Sp1 and NRF2 have been classified as nononcogene addiction genes and thus are imperative to understanding the molecular mechanism of resistance. These finding have huge clinical relevance as both Sp1 and GRP78 are overexpressed in pancreatic cancer patients and increased expression of these proteins is indicative of poor prognosis. Understanding how these proteins may regulate chemoresistance phenotype of this aggressive cancer may pave the way for development of efficacious therapy for this devastating disease.

Trefoil factor 1 inhibits epithelial-mesenchymal transition of pancreatic intraepithelial neoplasm

The tumor-suppressive role of trefoil factor family (TFF) members in gastric carcinogenesis has been suggested, but their significance and mechanisms in other digestive diseases remain elusive. To clarify the role of TFF1 in pancreatic carcinogenesis, we performed IHC on human samples, transfected siRNA against TFF1 into pancreatic cancer cell lines, and employed mouse models in which PanIN development and loss of TFF1 occur simultaneously. In human samples, the expression of TFF1 was specifically observed in pancreatic intraepithelial neoplasm (PanIN), but was frequently lost in the invasive component of pancreatic ductal adenocarcinoma (PDAC). When the expression of TFF1 was suppressed in vitro, pancreatic cancer cell lines showed enhanced invasive ability and features of epithelial-mesenchymal transition (EMT), including upregulated Snail expression. TFF1 expression was also observed in PanIN lesions of Pdx-1 Cre; LSL-KRASG12D (KC) mice, a model of pancreatic cancer, and loss of TFF1 in these mice resulted in the expansion of PanIN lesions, an EMT phenotype in PanIN cells, and an accumulation of cancer-associated fibroblasts (CAFs), eventually resulting in the development of invasive adenocarcinoma. This study indicates that the acquisition of TFF1 expression is an early event in pancreatic carcinogenesis and that TFF1 might act as a tumor suppressor to prevent EMT and the invasive transformation of PanIN.

Activated gastric cancer-associated fibroblasts contribute to the malignant phenotype and 5-FU resistance via paracrine action in gastric cancer

Background

Cancer-associated fibroblasts (CAFs) play important roles in tumor progression. However, the behaviors of activated CAFs in gastric cancer remain to be determined. The aim of the present study was to investigate the correlations between activated gastric CAFs and the prognosis of patients with gastric cancer, and to determine the effects of activated CAFs on the malignant phenotype and 5-fluorouracil resistance in this cancer.

Methods

Ninety-five patients with primary gastric cancer were enrolled in this study. Activation states of gastric CAFs were evaluated by immunohistochemistry. A modified method for the primary culture of gastric CAFs was employed. Types of CAFs and activation states were identified by immunocytochemical and immunofluorescent staining. Cell co-culture and gastric CAF conditioned medium transfer models were established to investigate the paracrine effects of activated CAFs on the migration and invasion of gastric cell lines. The half maximal inhibitory concentration of 5-fluorouracil and levels of cell apoptosis were examined using cell viability assay and flow cytometry, respectively. Protein expression levels of associated molecules were measured by Western blotting.

Results

Kaplan–Meier survival curves showed that activated gastric CAFs identified via fibroblast activation protein were significantly related to poorer cumulative survival in gastric cancer patients. Five strains of CAFs were successfully cultured via the modified culture method, and three gastric CAFs strains were identified as activated gastric CAFs. The migration and invasion abilities of gastric cells were significantly enhanced in both the co-culture group and the conditioned medium group. The half maximal inhibitory concentration for 5-fluorouracil in BGC-823 cells was elevated after treatment with conditioned medium, and early apoptosis was inhibited. Additionally, an obvious elevation of epithelial–mesenchymal transition level was observed in the conditioned medium group.

Conclusions

Activated gastric CAFs correlate with a poor prognosis of cancer patients and may contribute to the malignant phenotype and the development of resistance to 5-fluorouracil via paracrine action in gastric cancer. Gastric CAFs with a specific activation state might be used as a tumor biomarker within the microenvironment for prognosis and as a new therapeutic target for chemoresistant gastric cancer.

Electronic supplementary material

The online version of this article (10.1186/s12935-018-0599-7) contains supplementary material, which is available to authorized users.

The hepatic pre-metastatic niche in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) remains one of the most aggressive malignancies to date, largely because it is associated with high metastatic risk. Pancreatic tumors have a characteristic tendency to metastasize preferentially to the liver. Over the past two decades, it has become evident that the otherwise hostile milieu of the liver is selectively preconditioned at an early stage to render it more conducive to the engraftment and growth of disseminated cancer cells, a concept defined as pre-metastatic niche (PMN) formation. Pancreatic cancer cells exploit components of the tumor microenvironment to facilitate their migration out of the primary tumor, which often involves conversion of pancreatic cancer cells from an epithelial to a mesenchymal phenotype via the epithelial-to-mesenchymal transition. Pancreatic stellate cells and matrix stiffness have been put forward as major drivers of invasiveness in PDAC. Even before the onset of pancreatic cancer cell dissemination, soluble factors and extracellular vesicles secreted by the primary tumor, and possibly even premalignant lesions, help shape a supportive niche in the liver by providing vascular docking sites for circulating tumor cells, enhancing vascular permeability, remodeling the extracellular matrix and recruiting immunosuppressive inflammatory cells. Emerging evidence suggests that some of these tumor-derived factors may represent powerful diagnostic or prognostic biomarkers. Though our understanding of the mechanisms driving PMN formation in PDAC has expanded considerably, many outstanding questions and challenges remain. Further studies dissecting the molecular and cellular events involved in hepatic PMN formation in PDAC will likely improve diagnosis and open new avenues from a therapeutic standpoint.

Organoid Profiling Identifies Common Responders to Chemotherapy in Pancreatic Cancer

Pancreatic cancer is the most lethal common solid malignancy. Systemic therapies are often ineffective, and predictive biomarkers to guide treatment are urgently needed. We generated a pancreatic cancer patient-derived organoid (PDO) library that recapitulates the mutational spectrum and transcriptional subtypes of primary pancreatic cancer. New driver oncogenes were nominated and transcriptomic analyses revealed unique clusters. PDOs exhibited heterogeneous responses to standard-of-care chemotherapeutics and investigational agents. In a case study manner, we found that PDO therapeutic profiles paralleled patient outcomes and that PDOs enabled longitudinal assessment of chemosensitivity and evaluation of synchronous metastases. We derived organoid-based gene expression signatures of chemosensitivity that predicted improved responses for many patients to chemotherapy in both the adjuvant and advanced disease settings. Finally, we nominated alternative treatment strategies for chemorefractory PDOs using targeted agent therapeutic profiling. We propose that combined molecular and therapeutic profiling of PDOs may predict clinical response and enable prospective therapeutic selection.Significance: New approaches to prioritize treatment strategies are urgently needed to improve survival and quality of life for patients with pancreatic cancer. Combined genomic, transcriptomic, and therapeutic profiling of PDOs can identify molecular and functional subtypes of pancreatic cancer, predict therapeutic responses, and facilitate precision medicine for patients with pancreatic cancer. Cancer Discov; 8(9); 1112-29. ©2018 AACR.See related commentary by Collisson, p. 1062This article is highlighted in the In This Issue feature, p. 1047.

Do anti-stroma therapies improve extrinsic resistance to increase the efficacy of gemcitabine in pancreatic cancer?

Pancreatic ductal adenocarcinoma (PDAC) is among the most devastating human malignancies, with approximately 20-30% of PDAC patients receiving the surgical resection with curative intent. Although many studies have focused on finding ideal "drug chaperones" that facilitate and/or potentiate the effects of gemcitabine (GEM) in pancreatic cancer, a significant benefit in overall survival could not be demonstrated for any of these combination therapies in PDAC. Given that pancreatic cancer is characterized by desmoplasia and the dual biological roles of stroma in pancreatic cancer, we reassess the importance of stroma in GEM-based therapeutic approaches in light of current findings. This review is focused on understanding the role of stromal components in the extrinsic resistance to GEM and whether anti-stroma therapies have a positive effect on the GEM delivery. This work contributes to the development of novel and promising combination GEM-based regimens that have achieved significant survival benefits for the patients with pancreatic cancer.

Experimental models of pancreatic cancer desmoplasia

Desmoplasia is a fibro-inflammatory process and a well-established feature of pancreatic cancer. A key contributor to pancreatic cancer desmoplasia is the pancreatic stellate cell. Various in vitro and in vivo methods have emerged for the isolation, characterization, and use of pancreatic stellate cells in models of cancer-associated fibrosis. In addition to cell culture models, genetically engineered animal models have been established that spontaneously develop pancreatic cancer with desmoplasia. These animal models are currently being used for the study of pancreatic cancer pathogenesis and for evaluating therapeutics against pancreatic cancer. Here, we review various in vitro and in vivo models that are being used or have the potential to be used to study desmoplasia in pancreatic cancer.

Pancreatic Cancer Chemoresistance to Gemcitabine

Pancreatic ductal adenocarcinoma (PDAC), commonly referred to as pancreatic cancer, ranks among the leading causes of cancer-related deaths in the Western world due to disease presentation at an advanced stage, early metastasis and generally a very limited response to chemotherapy or radiotherapy. Gemcitabine remains a cornerstone of PDAC treatment in all stages of the disease despite suboptimal clinical effects primarily caused by molecular mechanisms limiting its cellular uptake and activation and overall efficacy, as well as the development of chemoresistance within weeks of treatment initiation. To circumvent gemcitabine resistance in PDAC, several novel therapeutic approaches, including chemical modifications of the gemcitabine molecule generating numerous new prodrugs, as well as new entrapment designs of gemcitabine in colloidal systems such as nanoparticles and liposomes, are currently being investigated. Many of these approaches are reported to be more efficient than the parent gemcitabine molecule when tested in cellular systems and in vivo in murine tumor model systems; however, although promising, their translation to clinical use is still in a very early phase. This review discusses gemcitabine metabolism, activation and chemoresistance entities in the gemcitabine cytotoxicity pathway and provides an overview of approaches to override chemoresistance in pancreatic cancer.

Mithramycin-loaded mPEG-PLGA nanoparticles exert potent antitumor efficacy against pancreatic carcinoma

Previous studies have shown that mithramycin A (MIT) is a promising candidate for the treatment of pancreatic carcinoma through inhibiting transcription factor Sp1. However, systemic toxicities may limit its clinical application. Here, we report a rationally designed formulation of MIT-loaded nanoparticles (MIT-NPs) with a small size and sustained release for improved passive targeting and enhanced therapeutic efficacy. Nearly spherical MIT-NPs with a mean particle size of 25.0±4.6 nm were prepared by encapsulating MIT into methoxy poly(ethylene glycol)-block-poly(d,l-lactic-co-glycolic acid) (mPEG-PLGA) nanoparticles (NPs) with drug loading of 2.11%±0.51%. The in vitro release of the MIT-NPs lasted for >48 h with a sustained-release pattern. The cytotoxicity of MIT-NPs to human pancreatic cancer BxPC-3 and MIA Paca-2 cells was comparable to that of free MIT. Determined by flow cytometry and confocal microscopy, the NPs internalized into the cells quickly and efficiently, reaching the peak level at 1-2 h. In vivo fluorescence imaging showed that the prepared NPs were gradually accumulated in BxPC-3 and MIA Paca-2 xenografts and retained for 168 h. The fluorescence intensity in both BxPC-3 and MIA Paca-2 tumors was much stronger than that of various tested organs. Therapeutic efficacy was evaluated with the poorly permeable BxPC-3 pancreatic carcinoma xenograft model. At a well-tolerated dose of 2 mg/kg, MIT-NPs suppressed BxPC-3 tumor growth by 96%. Compared at an equivalent dose, MIT-NPs exerted significantly higher therapeutic effect than free MIT (86% versus 51%, P<0.01). Moreover, the treatment of MIT and MIT-NPs reduced the expression level of oncogene c-Myc regulated by Sp1, and notably, both of them decreased the protein level of CD47. In summary, the novel formulation of MIT-NPs shows highly therapeutic efficacy against pancreatic carcinoma xenograft. In addition, MIT-NPs can downregulate CD47 expression, implying that it might play a positive role in cancer immunotherapy.

MUC1 and HIF-1alpha Signaling Crosstalk Induces Anabolic Glucose Metabolism to Impart Gemcitabine Resistance to Pancreatic Cancer

Poor response to cancer therapy due to resistance remains a clinical challenge. The present study establishes a widely prevalent mechanism of resistance to gemcitabine in pancreatic cancer, whereby increased glycolytic flux leads to glucose addiction in cancer cells and a corresponding increase in pyrimidine biosynthesis to enhance the intrinsic levels of deoxycytidine triphosphate (dCTP). Increased levels of dCTP diminish the effective levels of gemcitabine through molecular competition. We also demonstrate that MUC1-regulated stabilization of hypoxia inducible factor-1α (HIF-1α) mediates such metabolic reprogramming. Targeting HIF-1α or de novo pyrimidine biosynthesis, in combination with gemcitabine, strongly diminishes tumor burden. Finally, reduced expression of TKT and CTPS, which regulate flux into pyrimidine biosynthesis, correlates with better prognosis in pancreatic cancer patients on fluoropyrimidine analogs.