TGF-β-induced stromal CYR61 promotes resistance to gemcitabine in pancreatic ductal adenocarcinoma through downregulation of the nucleoside transporters hENT1 and hCNT3

The Crosstalk Analysis between mPSCs and Panc1 Cells Identifies CCN1 as a Positive Regulator of Gemcitabine Sensitivity in Pancreatic Cancer Cells

Pancreatic ductal adenocarcinoma (PDAC) is a deadly disease that is almost entirely resistant to conventional chemotherapy and radiation therapy. A significant factor in this resistance appears to be the dense desmoplastic stroma, which contains various cancer-associated fibroblast (CAF) populations. However, our understanding of the communication between tumor cells and CAFs that contributes to this aggressive malignancy is still developing. Recently, we used an advanced three-dimensional heterospecies, heterospheroid co-culture model to investigate the signaling between human pancreatic tumor Panc1 cells and mouse pancreatic stellate cells (mPSCs) through global expression profiling. Upon discovering that CCN1 was significantly upregulated in Panc1 cells during co-culture, we decided to explore the role of CCN1 using CRISPR-Cas9 knockout technology. Panc1 cells lacking CCN1 showed reduced differentiation and decreased sensitivity to gemcitabine, primarily due to lower expression of genes involved in gemcitabine transport and metabolism. Additionally, we observed that stimulation with TGF-β1 and lysophosphatidic acid increased CCN1 expression in Panc1 cells and induced a shift in mPSCs towards a more myofibroblastic CAF-like phenotype.

Overcoming therapy resistance in pancreatic cancer: New insights and future directions

Pancreatic adenocarcinoma (PDAC) is predicted to become the second leading cause of cancer deaths by 2030 and this is mostly due to therapy failure. Limited treatment options and resistance to standard-of-care (SoC) therapies makes PDAC one of the cancer types with poorest prognosis and survival rates [1,2]. Pancreatic tumors are renowned for their poor response to therapeutic interventions including targeted therapies, chemotherapy and radiotherapy. Herein, we review hallmarks of therapy resistance in PDAC and current strategies aiming to tackle escape mechanisms and to re-sensitize cancer cells to therapy. We will further provide insights on recent advances in the field of drug discovery, nanomedicine, and disease models that are setting the ground for future research.

Personalized treatment using predictive biomarkers in solid organ malignancies: A review

In recent years, the influence of specific biomarkers in the diagnosis and prognosis of solid organ malignancies has been increasingly prominent. The relevance of the use of predictive biomarkers, which predict cancer response to specific forms of treatment provided, is playing a more significant role than ever before, as it affects diagnosis and initiation of treatment, monitoring for efficacy and side effects of treatment, and adjustment in treatment regimen in the long term. In the current review, we explored the use of predictive biomarkers in the treatment of solid organ malignancies, including common cancers such as colorectal cancer, breast cancer, lung cancer, prostate cancer, and cancers associated with high mortalities, such as pancreatic cancer, liver cancer, kidney cancer and cancers of the central nervous system. We additionally analyzed the goals and types of personalized treatment using predictive biomarkers, and the management of various types of solid organ malignancies using predictive biomarkers and their relative efficacies so far in the clinical settings.

Hypoxia-initiated Cysteine-rich protein 61 secretion promotes chemoresistance of acute B lymphoblastic leukemia cells

The drug resistance is a major obstacle in acute B-lymphoblastic leukemia (B-ALL) treatment. Our previous study has indicated that increased levels of Cysteine-rich protein 61 (Cyr61) in the bone marrow can mitigate the chemosensitivity of B-ALL cells, though the specific source of Cyr61 in the bone marrow remains unknown. In this study, we aimed to investigate whether hypoxia can induce Cyr61 production in B-ALL cells, delineates the underlying mechanisms, and evaluates the effect of Cyr61 on the chemosensitivity of B-ALL cells under hypoxia conditions. The results indicate that hypoxia promotes Cyr61 production in B-ALL cells by activating the NF-κB pathway. Increased Cyr61 expression appears to reduce the chemosensitivity of B-ALL cell to vincristine (VCR) and daunorubicin (DNR) through autophagy under hypoxia. Notably, inhibition of Cyr61 restores the chemosensitivity of B-ALL cells to both chemotherapeutic agents. This study is the first time to report that hypoxia decreases the chemosensitivity of B-ALL cells by inducing Cyr61 production, suggesting that targeting Cyr61 or its associated pathways could potentially improve the clinical response of B-ALL patients.

Elucidation of the Gemcitabine Transporters of Escherichia coli K-12 and Gamma-Proteobacteria Linked to Gemcitabine-Related Chemoresistance

Gemcitabine (2',2'-difluoro-2'-deoxycytidine), a widely used anticancer drug, is considered a gold standard in treating aggressive pancreatic cancers. Gamma-proteobacteria that colonize the pancreatic tumors contribute to chemoresistance against gemcitabine by metabolizing the drug to a less active and deaminated form. The gemcitabine transporters of these bacteria are unknown to date. Furthermore, there is no complete knowledge of the gemcitabine transporters in Escherichia coli or any other related proteobacteria. In this study, we investigate the complement of gemcitabine transporters in E. coli K-12 and two common chemoresistance-related bacteria (Klebsiella pneumoniae and Citrobacter freundii). We found that E. coli K-12 has two high-affinity gemcitabine transporters with distinct specificity properties, namely, NupC and NupG, whereas the gemcitabine transporters of C. freundii and K. pneumoniae include the NupC and NupG orthologs, functionally indistinguishable from their counterparts, and, in K. pneumoniae, one additional NupC variant, designated KpNupC2. All these bacterial transporters have a higher affinity for gemcitabine than their human counterparts. The highest affinity (KM 2.5-3.0 μΜ) is exhibited by NupGs of the bacteria-specific nucleoside-H+ symporter (NHS) family followed by NupCs (KM 10-13 μΜ) of the concentrative nucleoside transporter (CNT) family, 15-100 times higher than the affinities reported for the human gemcitabine transporter hENT1/SLC29A1, which is primarily associated with gemcitabine uptake in the pancreatic adenocarcinoma cells. Our results offer a basis for further insight into the role of specific bacteria in drug availability within tumors and for understanding the structure-function differences of bacterial and human drug transporters.

The role of yes activated protein (YAP) in melanoma metastasis

Hippo was first identified in a genetic screen as a protein that suppressed proliferation and cell growth. Subsequently, it was shown that hippo acted in a so-called canonical cascade to suppress Yorkie, the Drosophila equivalent of Yes-activated protein (YAP), a mechanosensitive transcriptional cofactor that enhances the activity of the TEAD family of transcription factors. YAP promotes fibrosis, activation of cancer-associated fibroblasts, angiogenesis and cancer cell invasion. YAP activates the expression of the matricellular proteins CCN1 (cyr61) and CCN2 (ctgf), themselves mediators of fibrogenesis and oncogenesis, and coordination of matrix deposition and angiogenesis. This review discusses how therapeutically targeting YAP through YAP inhibitors verteporfin and celastrol and its downstream mediators CCN1 and CCN2 might be useful in treating melanoma.

Cancer-associated fibroblasts in pancreatic ductal adenocarcinoma therapy: Challenges and opportunities

Pancreatic ductal adenocarcinoma (PDAC) is a solid organ malignancy with a high mortality rate. Statistics indicate that its incidence has been increasing as well as the associated deaths. Most patients with PDAC show poor response to therapies making the clinical management of this cancer difficult. Stromal cells in the tumor microenvironment (TME) contribute to the development of resistance to therapy in PDAC cancer cells. Cancer-associated fibroblasts (CAFs), the most prevalent stromal cells in the TME, promote a desmoplastic response, produce extracellular matrix proteins and cytokines, and directly influence the biological behavior of cancer cells. These multifaceted effects make it difficult to eradicate tumor cells from the body. As a result, CAF-targeting synergistic therapeutic strategies have gained increasing attention in recent years. However, due to the substantial heterogeneity in CAF origin, definition, and function, as well as high plasticity, majority of the available CAF-targeting therapeutic approaches are not effective, and in some cases, they exacerbate disease progression. This review primarily elucidates on the effect of CAFs on therapeutic efficiency of various treatment modalities, including chemotherapy, radiotherapy, immunotherapy, and targeted therapy. Strategies for CAF targeting therapies are also discussed.

Upregulation of CYR61 by TGF-β and YAP signaling exerts a counter-suppression of hepatocellular carcinoma

Transforming growth factor-β (TGF-β) and Hippo signaling are two critical pathways engaged in cancer progression by regulating both oncogenes and tumor suppressors, yet how the two pathways coordinately exert their functions in the development of hepatocellular carcinoma (HCC) remains elusive. In this study, we firstly conducted an integrated analysis of public liver cancer databases and our experimental TGF-β target genes, identifying CYR61 as a pivotal candidate gene relating to HCC development. The expression of CYR61 is downregulated in clinical HCC tissues and cell lines than that in the normal counterparts. Evidence revealed that CYR61 is a direct target gene of TGF-β in liver cancer cells. In addition, TGF-β-stimulated Smad2/3 and the Hippo pathway downstream effectors YAP and TEAD4 can form a protein complex on the promoter of CYR61, thereby activating the promoter activity and stimulating CYR61 gene transcription in a collaborative manner. Functionally, depletion of CYR61 enhanced TGF-β- or YAP-mediated growth and migration of liver cancer cells. Consistently, ectopic expression of CYR61 was capable of impeding TGF-β- or YAP-induced malignant transformation of HCC cells in vitro and attenuating HCC xenograft growth in nude mice. Finally, transcriptomic analysis indicates that CYR61 can elicit an antitumor program in liver cancer cells. Together, these results add new evidence for the crosstalk between TGF-β and Hippo signaling and unveil an important tumor suppressor function of CYR61 in liver cancer.

Chemotherapy-initiated cysteine-rich protein 61 decreases acute B-lymphoblastic leukemia chemosensitivity

PURPOSE

Chemoresistance is a major challenge for acute lymphoblastic leukemia (ALL) treatment. Cysteine-rich protein 61 (Cyr61) plays an important role in drug resistance modulation of tumor cells, and Cyr61 levels are increased in the bone marrow of patients with ALL and contribute to ALL cell survival. However, the effect of Cyr61 on B cell acute lymphoblastic leukemia (B-ALL) cell chemosensitivity and the regulatory mechanisms underlying Cyr61 production in bone marrow remain unknown.

METHODS

Nalm-6 and Reh human B-ALL cell lines were used in this study. Cyr61 levels were assessed using quantitative real-time PCR (qRT-PCR), western blot analysis, and enzyme-linked immunosorbent assay. The effect of Cyr61 on B-ALL cell chemosensitivity to daunorubicin (DNR) was evaluated using cell viability and flow cytometry analyses. The regulatory mechanisms of Cyr61 production in bone marrow were examined using qRT-PCR and western blot analysis.

RESULTS

Cyr61 knockdown and overexpression increased and decreased the chemosensitivity of B-ALL cells to DNR, respectively. Cyr61 attenuated chemotherapeutic drug-induced apoptosis by upregulating B cell lymphoma-2. Notably, DNR induced DNA damage response and increased Cyr61 secretion in B-ALL cells through the ataxia telangiectasia mutated (ATM)-dependent nuclear factor kappa B pathway.

CONCLUSION

DNR induces Cyr61 production in B-ALL cells, and increased Cyr61 levels reduce the chemosensitivity of B-ALL cells. Consequently, targeting Cyr61 or related ATM signaling pathway may present a promising treatment strategy to enhance the chemosensitivity of patients with B-ALL.

Macrophages reprogramming driven by cancer-associated fibroblasts under FOLFIRINOX treatment correlates with shorter survival in pancreatic cancer

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) remains a clinically challenging cancer, mainly due to limited therapeutic options and the presence of a highly prominent tumor microenvironment (TME), facilitating tumor progression. The TME is predominated by heterogeneous populations of cancer-associated fibroblasts (CAFs) and tumor associated macrophages (TAMs), in constant communication with each other and with tumor cells, influencing many tumoral abilities such as therapeutic resistance. However how the crosstalk between CAFs and macrophages evolves following chemotherapeutic treatment remains poorly understood, limiting our capacity to halt therapeutic resistance.

METHODS

We combined biological characterization of macrophages indirectly cocultured with human PDAC CAFs, under FOLFIRINOX treatment, with mRNAseq analyses of such macrophages and evaluated the relevance of the specific gene expression signature in a large series of primary PDAC patients to search for correlation with overall survival (OS) after FOLFIRINOX chemotherapy.

RESULTS

Firstly, we demonstrated that CAFs polarize naïve and M1 macrophages towards an M2-like phenotype with a specific increase of CD200R and CD209 M2 markers. Then, we demonstrated that CAFs counteract the pro-inflammatory phenotype induced by the FOLFIRINOX on Macrophages. Indeed, we highlighted that, under FOLFIRINOX, CAFs limit the FOLFIRINOX-induced cell death of macrophages and further reinforce their M2 phenotype as well as their immunosuppressive impact through specific chemokines production. Finally, we revealed that under FOLFIRINOX CAFs drive a specific macrophage gene expression signature involving SELENOP and GOS2 that correlates with shortened OS in FOLFIRINOX-treated PDAC patients.

CONCLUSION

Our study provides insight into the complex interactions between TME cells under FOLFIRINOX treatment. It suggests potential novel candidates that could be used as therapeutic targets in combination with FOLFIRINOX to prevent and alleviate TME influx on therapeutic resistance as well as biomarkers to predict FOLFIRINOX response in PDAC patients. Video Abstract.

Deletion of the mRNA stability factor ELAVL1 (HuR) in pancreatic cancer cells disrupts the tumor microenvironment integrity

Stromal cells promote extensive fibrosis in pancreatic ductal adenocarcinoma (PDAC), which is associated with poor prognosis and therapeutic resistance. We report here for the first time that loss of the RNA-binding protein human antigen R (HuR, ELAVL1) in PDAC cells leads to reprogramming of the tumor microenvironment. In multiple in vivo models, CRISPR deletion of ELAVL1 in PDAC cells resulted in a decrease of collagen deposition, accompanied by a decrease of stromal markers (i.e. podoplanin, α-smooth muscle actin, desmin). RNA-sequencing data showed that HuR plays a role in cell-cell communication. Accordingly, cytokine arrays identified that HuR regulates the secretion of signaling molecules involved in stromal activation and extracellular matrix organization [i.e. platelet-derived growth factor AA (PDGFAA) and pentraxin 3]. Ribonucleoprotein immunoprecipitation analysis and transcription inhibition studies validated PDGFA mRNA as a novel HuR target. These data suggest that tumor-intrinsic HuR supports extrinsic activation of the stroma to produce collagen and desmoplasia through regulating signaling molecules (e.g. PDGFAA). HuR-deficient PDAC in vivo tumors with an altered tumor microenvironment are more sensitive to the standard of care gemcitabine, as compared to HuR-proficient tumors. Taken together, we identified a novel role of tumor-intrinsic HuR in its ability to modify the surrounding tumor microenvironment and regulate PDGFAA.

TGF-β mediated drug resistance in solid cancer

Transforming growth factor β (TGF-β) is an important signaling molecule which is expressed in three different isoforms in mammals (i.e. TGF-β1, -β2, and -β3). The interaction between TGF-β and its receptor triggers several pathways, which are classified into SMAD-dependent (canonical) and SMAD-independent (non-canonical) signaling, whose activation/transduction is finely regulated by several mechanisms. TGF-β is involved in many physiological and pathological processes, assuming a dualistic role in cancer progression depending on tumor stage. Indeed, TGF-β inhibits cell proliferation in early-stage tumor cells, while it promotes cancer progression and invasion in advanced tumors, where high levels of TGF-β have been reported in both tumor and stromal cells. In particular, TGF-β signaling has been found to be strongly activated in cancers after treatment with chemotherapeutic agents and radiotherapy, resulting in the onset of drug resistance conditions. In this review we provide an up-to-date description of several mechanisms involved in TGF-β-mediated drug resistance, and we report different strategies that are currently under development in order to target TGF-β pathway and increase tumor sensitivity to therapy.

Vactosertib, TGF-β receptor I inhibitor, augments the sensitization of the anti-cancer activity of gemcitabine in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) exhibits a pronounced extracellular matrix (ECM)-rich response, which is produced by an excessive amount of transforming growth factor β (TGF-β), resulting in tumor progression and metastasis. In addition, TGF-β signaling contributes to rapidly acquired resistance and incomplete response to gemcitabine. Recently, selective inhibitors of the TGF-β signaling pathway have shown promise in PDAC treatment, particularly as an option for augmenting responses to chemotherapy. Here, we investigated the synergistic anticancer effects of a small-molecule TGF-β receptor I kinase inhibitor (vactosertib/EW-7197) in the presence of gemcitabine, and its mechanism of action in pancreatic cancer. Vactosertib sensitized pancreatic cancer cells to gemcitabine by synergistically inhibiting their viability. Importantly, the combination of vactosertib and gemcitabine significantly attenuated the expression of major ECM components, including collagens, fibronectin, and α-SMA, in pancreatic cancer compared with gemcitabine alone. This resulted in potent induction of mitochondrial-mediated apoptosis, gemcitabine-mediated cytotoxicity, and inhibition of tumor ECM by vactosertib. Additionally, the combination decreased metastasis through inhibition of migration and invasion, and exhibited synergistic anti-cancer activity by inhibiting the TGF-β/Smad2 pathway in pancreatic cancer cells. Furthermore, co-treatment significantly suppressed tumor growth in orthotopic models. Therefore, our findings demonstrate that vactosertib synergistically increased the antitumor activity of gemcitabine via inhibition of ECM component production by inhibiting the TGF-β/Smad2 signaling pathway. This suggests that the combination of vactosertib and gemcitabine may be a potential treatment option for patients with pancreatic cancer.

CRISPR technology: A versatile tool to model, screen, and reverse drug resistance in cancer

BACKGROUND

Drug resistance is a serious challenge in cancer treatment that can render chemotherapy a failure. Understanding the mechanisms behind drug resistance and developing novel therapeutic approaches are cardinal steps in overcoming this issue. Clustered regularly interspaced short palindrome repeats (CRISPR) gene-editing technology has proven to be a useful tool to study cancer drug resistance mechanisms and target the responsible genes. In this review, we evaluated original research studies that used the CRISPR tool in three areas related to drug resistance, namely screening resistance-related genes, generating modified models of resistant cells and animals, and removing resistance by genetic manipulation. We reported the targeted genes, study models, and drug groups in these studies. In addition to discussing different applications of CRISPR technology in cancer drug resistance, we analyzed drug resistance mechanisms and provided examples of CRISPR's role in studying them. Although CRISPR is a powerful tool for examining drug resistance and sensitizing resistant cells to chemotherapy, more studies are required to overcome its disadvantages, such as off-target effects, immunotoxicity, and inefficient delivery of CRISPR/cas9 into the cells.

Barriers and opportunities for gemcitabine in pancreatic cancer therapy

Pancreatic ductal adenocarcinoma (PDA) has become one of the leading causes of cancer-related deaths across the world. A lack of durable responses to standard-of-care chemotherapies renders its treatment particularly challenging and largely contributes to the devastating outcome. Gemcitabine, a pyrimidine antimetabolite, is a cornerstone in PDA treatment. Given the importance of gemcitabine in PDA therapy, extensive efforts are focusing on exploring mechanisms by which cancer cells evade gemcitabine cytotoxicity, but strategies to overcome them have not been translated into patient care. Here, we will introduce the standard treatment paradigm for patients with PDA, highlight mechanisms of gemcitabine action, elucidate gemcitabine resistance mechanisms, and discuss promising strategies to circumvent them.

Pancreatic stellate cell-induced gemcitabine resistance in pancreatic cancer is associated with LDHA- and MCT4-mediated enhanced glycolysis

BACKGROUND

Profound resistance to chemotherapy remains a major challenge in achieving better clinical outcomes for patients with pancreatic ductal adenocarcinoma (PDAC). Recent studies indicate that gemcitabine (GEM) resistance is promoted both by pancreatic stellate cells (PSCs) and through increased glycolysis. However, it remains unknown whether PSCs affect GEM sensitivity via glycolytic regulation.

METHODS

Human pancreatic cancer cell (PCC) lines (BxPC-3, Capan-2, HPAF-II, Mia PaCa-2, Panc-1, SW-1990) were exposed to three different PSC-conditioned media (PSC-CM; PSC-1, PSC-2, HPaSteC), following either pre-treatment with glycolysis inhibitor NV-5440 or transfection for transient silencing of key glycolytic regulators (LDHA and MCT4). Proliferation, glucose transport, extracellular lactate, and GEM sensitivity were assessed. Protein expression was determined by Western blot and immunostaining. Moreover, secreted proteins in PSC-CMs were profiled by mass spectrometry (MS).

RESULTS

While exposure to PSC-CMs did not affect glucose transport in PCCs, it increased their lactate release and proliferation, and reduced the sensitivity for GEM. Both NV-5440 treatment and transient silencing of LDHA and MCT4 inhibited these PSC-induced changes in PCCs. MS analysis identified 688 unique proteins with differential expression, of which only 87 were common to the three PSC-CMs. Most PSC-secreted proteins were extracellular matrix-related, including SPARC, fibronectin, and collagens. Moreover, exposure to PSC-CMs increased the phosphorylation of ERK in PCCs, but the treatment of PCCs with the MEK/ERK inhibitor PD98059 resulted in a reduction of PSC-CM-induced glycolysis and improved GEM sensitivity.

CONCLUSIONS

The study findings suggest that PSC-secreted factors promote both glycolysis and GEM resistance in PCCs, and that glycolysis inhibition by NV-5440 and blocking of ERK phosphorylation by PD98059 protect PCCs from PSC-CM-induced loss of GEM sensitivity. Taken together, PSCs appear to promote GEM resistance in PDAC via glycolysis. Thus, targeting glycolysis may improve the effect of chemotherapy in PDAC.

Nucleoside transporters and immunosuppressive adenosine signaling in the tumor microenvironment: Potential therapeutic opportunities

Adenosine compartmentalization has a profound impact on immune cell function by regulating adenosine localization and, therefore, extracellular signaling capabilities, which suppresses immune cell function in the tumor microenvironment. Nucleoside transporters, responsible for the translocation and cellular compartmentalization of hydrophilic adenosine, represent an understudied yet crucial component of adenosine disposition in the tumor microenvironment. In this review article, we will summarize what is known regarding nucleoside transporter's function within the purinome in relation to currently devised points of intervention (i.e., ectonucleotidases, adenosine receptors) for cancer immunotherapy, alterations in nucleoside transporter expression reported in cancer, and potential avenues for targeting of nucleoside transporters for the desired modulation of adenosine compartmentalization and action. Further, we put forward that nucleoside transporters are an unexplored therapeutic opportunity, and modulation of nucleoside transport processes could attenuate the pathogenic buildup of immunosuppressive adenosine in solid tumors, particularly those enriched with nucleoside transport proteins.

The promising therapeutic effects of metformin on metabolic reprogramming of cancer-associated fibroblasts in solid tumors

Tumor-infiltrated lymphocytes are exposed to many toxic metabolites and molecules in the tumor microenvironment (TME) that suppress their anti-tumor activity. Toxic metabolites, such as lactate and ketone bodies, are produced mainly by catabolic cancer-associated fibroblasts (CAFs) to feed anabolic cancer cells. These catabolic and anabolic cells make a metabolic compartment through which high-energy metabolites like lactate can be transferred via the monocarboxylate transporter channel 4. Moreover, a decrease in molecules, including caveolin-1, has been reported to cause deep metabolic changes in normal fibroblasts toward myofibroblast differentiation. In this context, metformin is a promising drug in cancer therapy due to its effect on oncogenic signal transduction pathways, leading to the inhibition of tumor proliferation and downregulation of key oncometabolites like lactate and succinate. The cross-feeding and metabolic coupling of CAFs and tumor cells are also affected by metformin. Therefore, the importance of metabolic reprogramming of stromal cells and also the pivotal effects of metformin on TME and oncometabolites signaling pathways have been reviewed in this study.

Patient-specific modeling of stroma-mediated chemoresistance of pancreatic cancer using a three-dimensional organoid-fibroblast co-culture system

BACKGROUND

Cancer-associated fibroblasts (CAFs) are considered to play a fundamental role in pancreatic ductal adenocarcinoma (PDAC) progression and chemoresistance. Patient-derived organoids have demonstrated great potential as tumor avatars for drug response prediction in PDAC, yet they disregard the influence of stromal components on chemosensitivity.

METHODS

We established direct three-dimensional (3D) co-cultures of primary PDAC organoids and patient-matched CAFs to investigate the effect of the fibroblastic compartment on sensitivity to gemcitabine, 5-fluorouracil and paclitaxel treatments using an image-based drug assay. Single-cell RNA sequencing was performed for three organoid/CAF pairs in mono- and co-culture to uncover transcriptional changes induced by tumor-stroma interaction.

RESULTS

Upon co-culture with CAFs, we observed increased proliferation and reduced chemotherapy-induced cell death of PDAC organoids. Single-cell RNA sequencing data evidenced induction of a pro-inflammatory phenotype in CAFs in co-cultures. Organoids showed increased expression of genes associated with epithelial-to-mesenchymal transition (EMT) in co-cultures and several potential receptor-ligand interactions related to EMT were identified, supporting a key role of CAF-driven induction of EMT in PDAC chemoresistance.

CONCLUSIONS

Our results demonstrate the potential of personalized PDAC co-cultures models not only for drug response profiling but also for unraveling the molecular mechanisms involved in the chemoresistance-supporting role of the tumor stroma.

Role of the Tumor Microenvironment in Regulating Pancreatic Cancer Therapy Resistance

Pancreatic cancer has a notoriously poor prognosis, exhibits persistent drug resistance, and lacks a cure. Unique features of the pancreatic tumor microenvironment exacerbate tumorigenesis, metastasis, and therapy resistance. Recent studies emphasize the importance of exploiting cells in the tumor microenvironment to thwart cancers. In this review, we summarize the hallmarks of the multifaceted pancreatic tumor microenvironment, notably pancreatic stellate cells, tumor-associated fibroblasts, macrophages, and neutrophils, in the regulation of chemo-, radio-, immuno-, and targeted therapy resistance in pancreatic cancer. The molecular insight will facilitate the development of novel therapeutics against pancreatic cancer.

Role of drug catabolism, modulation of oncogenic signaling and tumor microenvironment in microbe-mediated pancreatic cancer chemoresistance

Pancreatic ductal adenocarcinoma (PDAC) has one of the highest incidence/death ratios among all neoplasms due to its late diagnosis and dominant chemoresistance. Most PDAC patients present with an advanced disease characterized by a multifactorial, inherent and acquired resistance to current anticancer treatments. This remarkable chemoresistance has been ascribed to several PDAC features including the genetic landscape, metabolic alterations, and a heterogeneous tumor microenvironment that is characterized by dense fibrosis, and a cellular contexture including functionally distinct subclasses of cancer-associated fibroblasts, immune suppressive cells, but also a number of bacteria, shaping a specific tumor microbiome microenvironment. Thus, recent studies prompted the emergence of a new research avenue, by describing the role of the microbiome in gemcitabine resistance, while next-generation-sequencing analyses identified a specific microbiome in different tumors, including PDAC. Functionally, the contribution of these microbes to PDAC chemoresistance is only beginning to be explored. Here we provide an overview of the studies demonstrating that bacteria have the capacity to metabolically transform and hence inactivate anticancer drugs, as exemplified by the inhibition of the efficacy of 10 out of 30 chemotherapeutics by Escherichia coli. Moreover, a number of bacteria modulate specific oncogenic pathways, such as Fusobacterium nucleatum, affecting autophagy and apoptosis induction by 5-fluorouracil and oxaliplatin. We hypothesize that improved understanding of how chemoresistance is driven by bacteria could enhance the efficacy of current treatments, and discuss the potential of microbiome modulation and targeted therapeutic approaches as well as the need for more reliable models and biomarkers to translate the findings of preclinical/translational research to the clinical setting, and ultimately overcome PDAC chemoresistance, hence improving clinical outcome.

Combination treatment with hENT1 and miR-143 reverses gemcitabine resistance in triple-negative breast cancer

Background

Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer and is susceptible to develop gemcitabine (GEM) resistance. Decreased expression of human equilibrative nucleoside transporter 1 (hENT1) accompanied by compensatory increase of glycolysis is strongly associated with GEM resistance in TNBC. In this study, we investigated the treatment feasibility of combined hENT1 upregulation and miR-143-mediated inhibition of glycolysis for reversing GEM resistance in TNBC.

Methods

Experiments were performed in vitro and in vivo to compare the efficacy of GEM therapies. In this study, we established stable drug-resistant cell line, GEM-R cells, from parental cells (MDA-MB-231) through exposure to GEM following a stepwise incremental dosing strategy. Then GEM-R cells were transfected by lentiviral plasmids and GEM-R cells overexpressing hENT1 (GEM-R-hENT1) were established. The viability and apoptosis of wild-type (MDA-MB-231), GEM-R, and GEM-R-hENT1 cells treated with GEM or GEM + miR-143 were analyzed by CCK8 assay and flow cytometry. The RNA expression and protein expression were measured by RT-PCR and western blotting respectively. GEM uptake was determined by multiple reaction monitoring (MRM) analysis. Glycolysis was measured by glucose assay and ¹⁸F-FDG uptake. The antitumor effect was assessed in vivo in a tumor xenograft model by evaluating toxicity, tumor volume, and maximum standardized uptake value in ¹⁸F-FDG PET. Immunohistochemistry and fluorescence photography were taken in tumor samples. Pairwise comparisons were performed using Student’s t-test.

Results

Our results represented that overexpression of hENT1 reversed GEM resistance in GEM-R cells by showing lower IC₅₀ and higher rate of apoptosis. MiR-143 suppressed glycolysis in GEM-R cells and enhanced the effect of reversing GEM resistance in GEM-R-hENT1 cells. The therapeutic efficacy was validated using a xenograft mouse model. Combination treatment decreased tumor growth rate and maximum standardized uptake value in ¹⁸F-FDG PET more effectively.

Conclusions

Combined therapy of exogenous upregulation of hENT1 expression and miR-143 mimic administration was effective in reversing GEM resistance, providing a promising strategy for treating GEM-resistant TNBC.

Systematic exploration of the underlying mechanism of gemcitabine resistance in pancreatic adenocarcinoma

Resistance to gemcitabine is the main challenge of chemotherapy for pancreatic ductal adenocarcinoma (PDAC). Hence, the development of a response signature to gemcitabine is essential for precision therapy of PDAC. However, existing quantitative signatures of gemcitabine are susceptible to batch effects and variations in sequencing platforms. Therefore, based on within-sample relative expression ordering of pairwise genes, we developed a transcriptome-based gemcitabine signature consisting of 28 gene pairs (28-GPS) that could predict response to gemcitabine for PDAC at the individual level. The 28-GPS was superior to previous quantitative signatures in terms of classification accuracy and prognostic performance. Resistant samples classified by 28-GPS showed poorer overall survival, higher genomic instability, lower immune infiltration, higher metabolic level and higher-fidelity DNA damage repair compared with sensitive samples. In addition, we found that gemcitabine combined with phosphoinositide 3-kinase (PI3K) inhibitor may be an alternative treatment strategy for PDAC. Single-cell analysis revealed that cancer cells in the same PDAC sample showed both the characteristics of sensitivity and resistance to gemcitabine, and the activation of the TGFβ signalling pathway could promote progression of PDAC. In brief, 28-GPS could robustly determine whether PDAC is resistant or sensitive to gemcitabine, and may be an auxiliary tool for clinical treatment.

Case Report: A Case of Locally Advanced Pancreatic Cancer Which Achieved Progression Free for Over 12 Months by Subsequent Therapy with Anlotinib Hydrochloride Plus Tegafur-Gimeracil-Oteracil Potassium (TS-1)

Titled the "most destructive of all cancers", pancreatic cancer is a malignant tumor with a very poor prognosis and has a poor response to systemic therapy. At present, several studies have shown that tegafur-gimeracil-oteracil potassium (hereinafter referred to as TS-1) is no less superior to gemcitabine in the treatment of advanced pancreatic cancer. In addition, a number of current clinical studies have shown that targeted therapy combined with chemotherapy reflects therapeutic advantages in pancreatic cancer. Moreover, in vitro and in vivo experiments have also demonstrated that anlotinib can curb the proliferation of pancreatic cancer cells and induce their apoptosis. Here, we report for the first time that a patient with locally advanced pancreatic cancer achieved good efficacy after switching to TS-1 chemotherapy combined with anlotinib targeted therapy. Previously, the disease of the patient still rapidly progressed without control following the first switch to abraxane combined with gemcitabine chemotherapy (AG regimen) due to the progression after chemo-radiotherapy. In this case, the patient achieved progression-free survival (PFS) of over 14 months via the treatment with anlotinib targeted therapy combined with TS-1 chemotherapy and secondary radiotherapy (prior to secondary radiotherapy, the patient achieved a PFS of nearly 12 months via the treatment with oral anlotinib combined with TS-1). Up to now, the progress of the disease is ceased. The oral administration of targeted therapy and chemotherapy are still in progress and the general condition of the patient is good. This suggests that patients with advanced pancreatic cancer may benefit from treatment with the anlotinib targeted therapy combined with TS-1 chemotherapy.

The Role of Cancer-Associated Fibroblasts in Ovarian Cancer

Ovarian cancer is a lethal gynecologic tumor and is generally resistant to conventional treatments. Stable cancer-associated fibroblasts (CAFs) are important cellular components in the ovarian cancer tumor microenvironment and may provide novel resources for future treatment strategies. Different subtypes of CAFs display specific functions in tumor pathogenesis and various CAF markers suggest potential treatment targets, such as FAP and GPR77. Both autocrine and paracrine cytokines play important roles in the CAF activation process and regulate tumor progression. Downstream mediators and pathways, including IL-6, TGF-β, NF-κB, mitogen-activated protein kinase (MAPK), and AKT/mTOR/(p70S6K), play important roles in the initiation, proliferation, invasiveness, and metastasis of ovarian cancer cells and also participate in angiogenesis, therapeutic resistance, and other biological processes. Several clinical or preclinical trials have targeted stromal fibroblasts and focused on the properties of CAFs to enhance ovarian cancer treatment outcomes. This review concentrates on the origins, subtypes, and activation of CAFs, as well as specific roles of CAFs in regulating tumor development and drug resistance, and aims to provide potential and prospective targets for improving the therapeutic efficacy of ovarian cancer treatment.

A new era: tumor microenvironment in chemoresistance of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is a solid malignant tumor with an extremely poor prognosis. Gemcitabine (GEM)-based chemotherapy remains one of the most important treatment choices for PDAC. However, either as monotherapy or as a part of the combination chemotherapy, GEM achieved only limited success in improving the survival of patients with advanced PDAC, primarily due to GEM resistance. PDAC is characterized by an extensive desmoplasia in the tumor microenvironment (TME). Increasing evidence indicates that this fibrotic TME not only actively participates in the tumor growth and spread of PDAC but also contributes to the induction of GEM resistance. Here we review the current advances of how TME components are involved in the induction of GEM resistance.

TGF-β Signaling and Resistance to Cancer Therapy

The transforming growth factor β (TGF-β) pathway, which is well studied for its ability to inhibit cell proliferation in early stages of tumorigenesis while promoting epithelial-mesenchymal transition and invasion in advanced cancer, is considered to act as a double-edged sword in cancer. Multiple inhibitors have been developed to target TGF-β signaling, but results from clinical trials were inconsistent, suggesting that the functions of TGF-β in human cancers are not yet fully explored. Multiple drug resistance is a major challenge in cancer therapy; emerging evidence indicates that TGF-β signaling may be a key factor in cancer resistance to chemotherapy, targeted therapy and immunotherapy. Finally, combining anti-TGF-β therapy with other cancer therapy is an attractive venue to be explored for the treatment of therapy-resistant cancer.

Role of human nucleoside transporters in pancreatic cancer and chemoresistance

The prognosis of pancreatic cancer is poor with the overall 5-year survival rate of less than 5% changing minimally over the past decades and future projections predicting it developing into the second leading cause of cancer related mortality within the next decade. Investigations into the mechanisms of pancreatic cancer development, progression and acquired chemoresistance have been constant for the past few decades, thus resulting in the identification of human nucleoside transporters and factors affecting cytotoxic uptake via said transporters. This review summaries the aberrant expression and role of human nucleoside transports in pancreatic cancer, more specifically human equilibrative nucleoside transporter 1/2 (hENT1, hENT2), and human concentrative nucleoside transporter 1/3 (hCNT1, hCNT3), while briefly discussing the connection and importance between these nucleoside transporters and mucins that have also been identified as being aberrantly expressed in pancreatic cancer. The review also discusses the incidence, current diagnostic techniques as well as the current therapeutic treatments for pancreatic cancer. Furthermore, we address the importance of chemoresistance in nucleoside analogue drugs, in particular, gemcitabine and we discuss prospective therapeutic treatments and strategies for overcoming acquired chemoresistance in pancreatic cancer by the enhancement of human nucleoside transporters as well as the potential targeting of mucins using a combination of mucolytic compounds with cytotoxic agents.

The Cellular Origins of Cancer-Associated Fibroblasts and Their Opposing Contributions to Pancreatic Cancer Growth

Pancreatic tumors are known to harbor an abundant and highly desmoplastic stroma. Among the various cell types that reside within tumor stroma, cancer-associated fibroblasts (CAFs) have gained a lot of attention in the cancer field due to their contributions to carcinogenesis and tumor architecture. These cells are not a homogeneous population, but have been shown to have different origins, phenotypes, and contributions. In pancreatic tumors, CAFs generally emerge through the activation and/or recruitment of various cell types, most notably resident fibroblasts, pancreatic stellate cells (PSCs), and tumor-infiltrating mesenchymal stem cells (MSCs). In recent years, single cell transcriptomic studies allowed the identification of distinct CAF populations in pancreatic tumors. Nonetheless, the exact sources and functions of those different CAF phenotypes remain to be fully understood. Considering the importance of stromal cells in pancreatic cancer, many novel approaches have aimed at targeting the stroma but current stroma-targeting therapies have yielded subpar results, which may be attributed to heterogeneity in the fibroblast population. Thus, fully understanding the roles of different subsets of CAFs within the stroma, and the cellular dynamics at play that contribute to heterogeneity in CAF subsets may be essential for the design of novel therapies and improving clinical outcomes. Fortunately, recent advances in technologies such as microfluidics and bio-printing have made it possible to establish more advanced ex vivo models that will likely prove useful. In this review, we will present the different roles of stromal cells in pancreatic cancer, focusing on CAF origin as a source of heterogeneity, and the role this may play in therapy failure. We will discuss preclinical models that could be of benefit to the field and that may contribute to further clinical development.

Tumor microenvironment and metabolic remodeling in gemcitabine-based chemoresistance of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is a solid malignant tumor with a very low operative rate and a poor patient prognosis. Therefore, gemcitabine (GEM)-based chemotherapy remains one of the most important treatment choices for PDAC. However, the efficacy of GEM monotherapy or GEM combination chemotherapy in improving the survival of patients with advanced PDAC is very limited, primarily due to GEM resistance. The mechanism of GEM resistance is complex and unclear. An extensive and dense fibrous matrix in the tumor microenvironment (TME) is an important feature of PDAC. Increasing evidence indicates that this fibrotic TME not only actively participates in the growth and spread of PDAC but also contributes to the induction of GEM resistance. Metabolic remodeling reduces GEM transport and synthesis in PDAC. This review focuses on the main cellular and molecular mechanisms underlying the involvement of the extracellular matrix (ECM), immune cells, and metabolic remodeling in the induction of GEM resistance; highlights the prospect of targeting the TME as an essential strategy to overcome GEM resistance; and provides new precise interventions for chemotherapy sensitization and improving the overall prognosis of patients with PDAC.

Improving selective targeting to cancer-associated fibroblasts by modifying liposomes with arginine based materials

A library of arginine-like surface modifiers was tested to improve the targetability of DOPE:DOPC liposomes towards myofibroblasts in a tumour microenvironment. Liposomes were characterised using zeta potential and dynamic light scattering. Cell viability remained unchanged for all liposomes. Liposomes were encapsulated using doxorubicin (DOX) with an encapsulation efficiency >94%. The toxicity of DOX-loaded liposomes was calculated via half-maximal inhibitory concentration (IC₅₀) for fibroblasts and myofibroblasts. These liposomes resulted in significantly lower IC₅₀-values for myofibroblasts compared to fibroblasts, making them more toxic towards the myofibroblasts. Furthermore, a significant increase in cell internalisation was observed for myofibroblasts compared to fibroblasts, using fluorescein-loaded liposomes. Most importantly, a novel regression model was constructed to predict the IC₅₀-values for different modifications using their physicochemical properties. Fourteen modifications (A-N) were used to train and validate this model; subsequently, this regression model predicted IC₅₀-values for three new modifications (O, P and Q) for both fibroblasts and myofibroblasts. Predicted and measured IC₅₀-values showed no significant difference for fibroblasts. For myofibroblasts, modification O showed no significant difference. This study demonstrates that the tested surface modifications can improve targeting to myofibroblasts in the presence of fibroblasts and hence are suitable drug delivery vehicles for myofibroblasts in a tumour microenvironment.

Advances in research of extracellular mechanisms underlying gemcitabine resistance in pancreatic cancer

Pancreatic cancer is a solid malignant tumor with the worst prognosis worldwide, and about 90% of cases are pancreatic ductal adenocarcinoma (PDAC). Although surgical resection is the only potential way to cure PDAC, the overall survival rate after surgery is still not optimistic. Consequently, gemcitabine (GEM)-based chemotherapy is still one of the most important treatment options for PDAC. However, the survival improvement by GEM monotherapy for advanced PDAC is very limited, and GEM resistance is the key reason. The mechanism underlying gemcitabine resistance is complex and still unclear in PDAC. The extensive and dense fibrous mesenchyme in the tumor microenvironment (TME) is an important feature of PDAC. More and more evidence has shown that TME is not only an active participant in tumor growth and spread, but also a contributor to the induction of GEM resistance. This article will review the recent advances in the understanding of the cellular and molecular mechanisms underlying GEM resistance in PDAC, and discuss potential GEM chemosensitization strategies, in order to improve the effective rate of chemotherapy and the outcome.

Ellagic Acid Resensitizes Gemcitabine-Resistant Bladder Cancer Cells by Inhibiting Epithelial-Mesenchymal Transition and Gemcitabine Transporters

Simple Summary

Chemoresistance of bladder cancer has become a major obstacle to clinical treatment, especially in first-line treatments involving gemcitabine (GCB). Epithelial-mesenchymal transition (EMT) is highly correlated with GCB resistance but less correlated with GCB metabolism and less reported as a novel therapeutic strategy. Our findings indicated that EMT-related GCB resistance occurs through the TGF-β/Smad signaling pathways and involves repressed expression of the GCB transporters hCNT1 and hENT1. Ellagic acid (EA) combined with GCB intensified the chemosensitivity of GCB in resistant cells by repressing Smad2, Smad3, and Smad4 expression and rescuing hCNT1 and hENT transcription. These data suggest that EA is a good adjuvant agent for blocking TGF-β/Smad signaling-related GCB resistance in bladder cancer.

Abstract

Gemcitabine (GCB) resistance is a major issue in bladder cancer chemoresistance, but its underlying mechanism has not been determined. Epithelial-mesenchymal transition (EMT) has been shown to be comprehensively involved in GCB resistance in several other cancer types, but the direct connection between EMT and GCB remains unclear. This study was designed to elucidate the mechanism of EMT-related GCB resistance in bladder cancer and identify a potential phytochemical to modulate drug sensitivity. The biological effects of ellagic acid (EA) or its combined effects with GCB were compared in GCB-resistant cells and the GCB-sensitive line in terms of cell viability, apoptosis, motility, and in vivo tumorigenicity. The molecular regulation of EMT-related GCB resistance was evaluated at both the mRNA and protein expression levels. Our results indicated that TGF-β/Smad induced the overactivation of EMT in GCB-resistant cells and reduced the expression of GCB influx transporters (hCNT1 and hENT1). Moreover, ellagic acid (EA) inhibited the TGF-β signaling pathway both in vitro and in vivo by reducing Smad2, Smad3, and Smad4 expression and thereby resensitized GCB sensitivity. In conclusion, our results demonstrate that TGF-β/Smad-induced EMT contributes to GCB resistance in bladder cancer by reducing GCB influx and also elucidate the novel mechanisms of EA-mediated inhibition of TGF-β/Smad-induced EMT to overcome GCB resistance. Our study warrants further investigation of EA as an effective therapeutic adjuvant agent for overcoming GCB resistance in bladder cancer.

Diagnostic, Predictive and Prognostic Molecular Biomarkers in Pancreatic Cancer: An Overview for Clinicians

Simple Summary

Pancreatic cancer is the fourth most common cancer-related cause of death in the United States and is usually asymptomatic in early stages. There is a scarcity of tests that facilitate early diagnosis or accurately predict the disease progression. To this end, biomarkers have been identified as important tools in the diagnosis and management of pancreatic cancer. Despite the increasing number of biomarkers described in the literature, most of them have demonstrated moderate sensitivity and/or specificity and are far from being considered as screening tests. More efficient non-invasive biomarkers are needed to facilitate early-stage diagnosis and interventions. Multi-disciplinary collaboration might be required to facilitate the identification of such markers.

Abstract

Pancreatic ductal adenocarcinoma (PDAC) is the most common pancreatic malignancy and is associated with aggressive tumor behavior and poor prognosis. Most patients with PDAC present with an advanced disease stage and treatment-resistant tumors. The lack of noninvasive tests for PDAC diagnosis and survival prediction mandates the identification of novel biomarkers. The early identification of high-risk patients and patients with PDAC is of utmost importance. In addition, the identification of molecules that are associated with tumor biology, aggressiveness, and metastatic potential is crucial to predict survival and to provide patients with personalized treatment regimens. In this review, we summarize the current literature and focus on newer biomarkers, which are continuously added to the armamentarium of PDAC screening, predictive tools, and prognostic tools.

Cancer-Associated Fibroblasts as a Common Orchestrator of Therapy Resistance in Lung and Pancreatic Cancer

Cancer arises from mutations accruing within cancer cells, but the tumor microenvironment (TME) is believed to be a major, often neglected, factor involved in therapy resistance and disease progression. Cancer-associated fibroblasts (CAFs) are prominent and key components of the TME in most types of solid tumors. Extensive research over the past decade revealed their ability to modulate cancer metastasis, angiogenesis, tumor mechanics, immunosuppression, and drug access through synthesis and remodeling of the extracellular matrix and production of growth factors. Thus, they are considered to impede the response to current clinical cancer therapies. Therefore, targeting CAFs to counteract these protumorigenic effects, and overcome the resistance to current therapeutic options, is an appealing and emerging strategy. In this review, we discuss how CAFs affect prognosis and response to clinical therapy and provide an overview of novel therapies involving CAF-targeting agents in lung and pancreatic cancer.

Ocoxin Increases the Antitumor Effect of BRAF Inhibition and Reduces Cancer Associated Fibroblast-Mediated Chemoresistance and Protumoral Activity in Metastatic Melanoma

Whereas the prevalence of several cancer types is decreasing, skin malignancies are growing more common every year. Malignant melanoma is the most aggressive form of skin cancer with high metastatic capacity. In most cases, malignant melanoma shows acquired therapy resistance. We evaluated the ability of Ocoxin, a natural compound-based antioxidant and anti-inflammatory nutritional complement, to exert an antitumor effect in melanoma. To do so, the cytotoxicity of Ocoxin in a panel of BRAF-mutated murine and human melanoma cell lines was tested alone and in combination with BRAF inhibitor Vemurafenib. Our results revealed a potent cytotoxic effect of Ocoxin against melanoma cells and a synergic effect when combined with Vemurafenib, reducing viability and increasing apoptosis. Besides, Ocoxin interferes with the cell cycle, impairs the inherent and fibroblast-mediated melanoma cell migration, and reduces resistance to BRAF inhibition. Proteomic analysis revealed reduced tumor secretion of inflammatory factors Galectin-1, Osteopontin, CCL5, and CCL9 upon treatment with Ocoxin. Moreover, RNASeq showed that Ocoxin downregulated the cell cycle and proliferation-related genes. In vivo, Ocoxin reduced the number of lung metastasis of YUMM-1.7 melanoma cells. Therefore, Ocoxin arises as a good candidate for clinical trials analyzing the beneficial effects in patients suffering from this cutaneous malignancy.

Stellate Cells Aid Growth-Permissive Metabolic Reprogramming and Promote Gemcitabine Chemoresistance in Pancreatic Cancer

Simple Summary

The great majority, more than 90%, of patients with pancreatic ductal adenocarcinoma (PDAC) die within less than five years after detection of the disease, despite recent treatment advances. The poor prognosis is related to late diagnosis, aggressive disease progression, and tumor resistance to conventional chemotherapy. PDAC tumor tissue is characterized by dense fibrosis and poor nutrient availability. A large portion of the tumor is made up of stromal fibroblasts, the pancreatic stellate cells (PSCs), which are known to contribute to tumor progression in several ways. PSCs have been shown to act as an alternate energy source, induce drug resistance, and inhibit drug availability in tumor cells, however, the underlying exact molecular mechanisms remain unknown. In this literature review, we discuss recent available knowledge about the contributions of PSCs to the overall progression of PDAC via changes in tumor metabolism and how this is linked to therapy resistance.

Abstract

Pancreatic ductal adenocarcinoma (PDAC), also known as pancreatic cancer (PC), is characterized by an overall poor prognosis and a five-year survival that is less than 10%. Characteristic features of the tumor are the presence of a prominent desmoplastic stromal response, an altered metabolism, and profound resistance to cancer drugs including gemcitabine, the backbone of PDAC chemotherapy. The pancreatic stellate cells (PSCs) constitute the major cellular component of PDAC stroma. PSCs are essential for extracellular matrix assembly and form a supportive niche for tumor growth. Various cytokines and growth factors induce activation of PSCs through autocrine and paracrine mechanisms, which in turn promote overall tumor growth and metastasis and induce chemoresistance. To maintain growth and survival in the nutrient-poor, hypoxic environment of PDAC, tumor cells fulfill their high energy demands via several unconventional ways, a process generally referred to as metabolic reprogramming. Accumulating evidence indicates that activated PSCs not only contribute to the therapy-resistant phenotype of PDAC but also act as a nutrient supplier for the tumor cells. However, the precise molecular links between metabolic reprogramming and an acquired therapy resistance in PDAC remain elusive. This review highlights recent findings indicating the importance of PSCs in aiding growth-permissive metabolic reprogramming and gemcitabine chemoresistance in PDAC.

Therapeutic resistance of pancreatic cancer: Roadmap to its reversal

Pancreatic cancer is a lethal disease with limited opportunity for resectable surgery as the first choice for cure due to its late diagnosis and early metastasis. The desmoplastic stroma and cellular genetic or epigenetic alterations of pancreatic cancer impose physical and biological barriers to effective therapies, including chemotherapy, radiotherapy, targeted therapy, and immunotherapy. Here, we review the current therapeutic options for pancreatic cancer, and underlying mechanisms and potential reversal of therapeutic resistance, a hallmark of this deadly disease.

"Open Sesame?": Biomarker Status of the Human Equilibrative Nucleoside Transporter-1 and Molecular Mechanisms Influencing its Expression and Activity in the Uptake and Cytotoxicity of Gemcitabine in Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) is an extremely aggressive tumor characterized by early invasiveness, rapid progression and resistance to treatment. For more than twenty years, gemcitabine has been the main therapy for PDAC both in the palliative and adjuvant setting. After the introduction of FOLFIRINOX as an upfront treatment for metastatic disease, gemcitabine is still commonly used in combination with nab-paclitaxel as an alternative first-line regimen, as well as a monotherapy in elderly patients unfit for combination chemotherapy. As a hydrophilic nucleoside analogue, gemcitabine requires nucleoside transporters to permeate the plasma membrane, and a major role in the uptake of this drug is played by human equilibrative nucleoside transporter 1 (hENT-1). Several studies have proposed hENT-1 as a biomarker for gemcitabine efficacy in PDAC. A recent comprehensive multimodal analysis of hENT-1 status evaluated its predictive role by both immunohistochemistry (with five different antibodies), and quantitative-PCR, supporting the use of the 10D7G2 antibody. High hENT-1 levels observed with this antibody were associated with prolonged disease-free status and overall-survival in patients receiving gemcitabine adjuvant chemotherapy. This commentary aims to critically discuss this analysis and lists molecular factors influencing hENT-1 expression. Improved knowledge on these factors should help the identification of subgroups of patients who may benefit from specific therapies and overcome the limitations of traditional biomarker studies.

Cancer-associated fibroblasts in therapeutic resistance of pancreatic cancer: Present situation, predicaments, and perspectives

Pancreatic cancer is highly lethal, and the most effective treatment is curative resection followed by chemotherapy. Unfortunately, chemoresistance is an extremely common occurrence, and novel treatment modalities, such as immunotherapy and molecular targeted therapy, have shown limited success in clinical practice. Pancreatic cancer is characterized by an abundant stromal compartment. Cancer-associated fibroblasts (CAFs) and the extracellular matrix they deposit account for a large portion of the pancreatic tumor stroma. CAFs interact directly and indirectly with pancreatic cancer cells and can compromise the effects of, and even promote tumorigenic responses to, various treatment approaches. To eliminate these adverse effects, CAFs depletion strategies were developed. Instead of the anticipated antitumor effects of CAFs depletion, more aggressive tumor phenotypes were occasionally observed. The failure of universal stromal depletion led to the investigation of CAFs heterogeneity that forms the foundation for stromal remodeling and normalization. This review analyzes the role of CAFs in therapeutic resistance of pancreatic cancer and discusses potential CAFs-targeting strategies basing on the diverse biological functions of CAFs, thus to improve the outcome of pancreatic cancer treatment.

A genome-scale CRISPR/Cas9 knockout screening reveals SH3D21 as a sensitizer for gemcitabine

Gemcitabine, 2',2'-difluoro-2'-deoxycytidine, is used as a pro-drug in treatment of variety of solid tumour cancers including pancreatic cancer. After intake, gemcitabine is transferred to the cells by the membrane nucleoside transporter proteins. Once inside the cells, it is converted to gemcitabine triphosphate followed by incorporation into DNA chains where it causes inhibition of DNA replication and thereby cell cycle arrest and apoptosis. Currently gemcitabine is the standard drug for treatment of pancreatic cancer and despite its widespread use its effect is moderate. In this study, we performed a genome-scale CRISPR/Cas9 knockout screening on pancreatic cancer cell line Panc1 to explore the genes that are important for gemcitabine efficacy. We found SH3D21 as a novel gemcitabine sensitizer implying it may act as a therapeutic target for improvement of gemcitabine efficacy in treatment of pancreatic cancer.

CRISPR Cas9 in Pancreatic Cancer Research

Pancreatic cancer is now becoming a common cause of cancer death with no significant change in patient survival over the last 10 years. The main treatment options for pancreatic cancer patients are surgery, radiation therapy and chemotherapy, but there is now considerable effort to develop new and effective treatments. In recent years, CRISPR/Cas9 technology has emerged as a powerful gene editing tool with promise, not only as an important research methodology, but also as a new and effective method for targeted therapy. In this review, we summarize current advances in CRISPR/Cas9 technology and its application to pancreatic cancer research, and importantly as a means of selectively targeting key drivers of pancreatic cancer.

Downregulation of LINC01638 lncRNA inhibits migration and invasion of pancreatic ductal adenocarcinoma cells by reducing TGF‑β signaling

LINC01638 is a long non-coding RNA (lncRNA) with an oncogenic role in breast cancer, while its involvement in other malignancies is unknown. This study was performed to investigate the potential role of LINC01638 in pancreatic ductal adenocarcinoma (PDAC). The expression of LINC01638 was determined via reverse transcription-quantitative polymerase chain reaction analysis, whereas the levels of transforming growth factor-β1 (TGF-β1) in plasma were measured via ELISA. Receiver operating characteristic curve analysis was conducted to determine the diagnostic value of LINC01638. Additionally, the migratory and invasive abilities of cells were evaluated via Transwell migration and invasion assays. In the present study, LINC01638 was significantly upregulated in tumor tissues compared with adjacent healthy tissues in the majority of patients with PDAC. Plasma levels of LINC01638 were significantly higher in patients with PDAC compared with in healthy controls. In effect, upregulation of plasma LINC01638 distinguished patients with PDAC from healthy controls in receiver operating characteristic analysis. Plasma levels of LINC01638 and TGF-β1 were positively correlated in patients with PDAC, but not in healthy controls. LINC01638 overexpression increased TGF-β1 expression, while silencing of LINC01638 using short hairpin RNA (shRNA) led to reduced TGF-β1 expression in a PDAC cell line. LINC01638 overexpression promoted, while shRNA silencing inhibited, migration and invasion of cell of a PDAC cell line. Treatment with exogenous TGF-β1 attenuated the inhibitory effect of LINC01638 shRNA silencing on cancer cell migration and invasion. It is concluded that LINC01638 lncRNA may be involved in the migration and invasion of PDAC cells via regulation of TGF-β1.

Establishment and characterization of the gemcitabine-resistant human pancreatic cancer cell line SW1990/gemcitabine

Due to its rapid progression, metastasis and resistance to chemotherapy, pancreatic cancer is one of the most malignant tumor types to affect the digestive system. Gemcitabine chemotherapy is typically the first choice of treatment for advanced pancreatic cancer; however, chemoresistance is a major obstacle to successful treatment. In order to elucidate the underlying mechanisms of gemcitabine resistance in pancreatic cancer, the drug-resistant cell line SW1990-gemcitabine (SW1990-GZ) was established using the human pancreatic cancer cell line SW1990. The IC₅₀, resistance index and growth of SW1990 and SW1990-GZ cells were also assessed using 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assays. The cellular uptake of gemcitabine in SW1990 and SW1990-GZ was measured using high performance liquid chromatography (HPLC). The protein expression of p53 was also assessed by western blot analysis. The results demonstrated that the IC₅₀ of SW1990 and SW1990-Gz was 0.07±0.0021 and 87.5±3.24 µg/ml, respectively, and that the resistance index ratio of SW1990-Gz was 1,250. The growth rate of SW1990-GZ cells was low compared with that of SW1990 cells. The HPLC results indicated that gemcitabine uptake was markedly reduced in SW1990-GZ cells compared with in SW1990 cells at different time points. The protein expression of p53 was significantly higher in GEM-resistant SW1990-GZ cells compared with that in SW1990 cells (P<0.01). These results suggest that a human gemcitabine-resistant pancreatic cancer cell line was successfully established, with stable and significant drug resistance. The results of the present study suggest that the decreased cellular uptake of gemcitabine may serve an important role in gemcitabine chemoresistance in SW1990-GZ cells; thus, this cell line may be used as an effective in vitro model to improve our understanding of gemcitabine-resistance in pancreatic cancer.

Impact of Cancer-Associated Fibroblast on the Radiation-Response of Solid Xenograft Tumors

Increasing evidence indicates that the heterogeneous tumor stroma supports therapy resistance at multiple levels. Fibroblasts, particularly cancer-associated fibroblasts (CAFs) are critical components of the tumor stroma. However, the impact of CAFs on the outcome of radiotherapy (RT) is poorly understood. Here, we investigated if and how fibroblasts/CAFs modulate the radiation response of malignant tumors by altering cancer cell radiosensitivity or radioresistance in vitro and in vivo. The influence of fibroblasts on cancer cell proliferation, cell death induction and long-term survival after RT was studied using different sets of fibroblasts and cancer cells in an indirect co-culture (2D) system to analyse potential paracrine interactions or a 3D model to study direct interactions. Paracrine signals from embryonic NIH-3T3 fibroblasts promoted MPR31.4 prostate and Py8119 breast cancer cell proliferation. Indirect co-culture with L929 skin fibroblasts induced higher levels of apoptosis in irradiated MPR31.4 cells, while they promoted proliferation of irradiated Py8119 cells. In addition, NIH-3T3 fibroblasts promoted long-term clonogenic survival of both tumor cell types upon irradiation in the 3D co-culture system when compared to non-irradiated controls. Also in vivo, co-implantation of cancer cells and fibroblasts resulted in different effects depending on the respective cell combinations used: co-implantation of MPR31.4 cells with NIH-3T3 fibroblasts or of Py8119 cells with L929 fibroblasts led to increased tumor growth and reduced radiation-induced tumor growth delay when compared to the respective tumors without co-implanted fibroblasts. Taken together, the impact of fibroblasts on cancer cell behavior and radiation sensitivity largely depended on the respective cell types used as they either exerted a pro-tumorigenic and radioresistance-promoting effect, an anti-tumorigenic effect, or no effect. We conclude that the plasticity of fibroblasts allows for such a broad spectrum of activities by the same fibroblast and that this plasticity is at least in part mediated by cancer cell-induced fibroblast activation toward CAFs.

Application of CRISPR/Cas9 gene editing technique in the study of cancer treatment

In recent years, gene editing, especially that using clustered regularly interspaced short palindromic repeat (CRISPR)/Cas9, has made great progress in the field of gene function. Rapid development of gene editing techniques has contributed to their significance in the field of medicine. Because the CRISPR/Cas9 gene editing tool is not only powerful but also has features such as strong specificity and high efficiency, it can accurately and rapidly screen the whole genome, facilitating the administration of gene therapy for specific diseases. In the field of tumor research, CRISPR/Cas9 can be used to edit genomes to explore the mechanisms of tumor occurrence, development, and metastasis. In these years, this system has been increasingly applied in tumor treatment research. CRISPR/Cas9 can be used to treat tumors by repairing mutations or knocking out specific genes. To date, numerous preliminary studies have been conducted on tumor treatment in related fields. CRISPR/Cas9 holds great promise for gene-level tumor treatment. Personalized and targeted therapy based on CRISPR/Cas9 will possibly shape the development of tumor therapy in the future. In this study, we review the findings of CRISPR/Cas9 for tumor treatment research to provide references for related future studies on the pathogenesis and clinical treatment of tumors.

Cell signaling and cancer: a mechanistic insight into drug resistance

Drug resistance is a major setback for advanced therapeutics in multiple cancers. The increasing prevalence of this resistance is a growing concern and bitter headache for the researchers since a decade. Hence, it is essential to revalidate the existing strategies available for cancer treatment and to look after a novel therapeutic approach for target based killing of cancer cells at the genetic level. This review outlines the different mechanisms enabling resistance including drug efflux, drug target alternation, alternative splicing, the release of the extracellular vesicle, tumor heterogeneity, epithelial-mesenchymal transition, tumor microenvironment, the secondary mutation in the receptor, epigenetic alternation, heterodimerization of receptors, amplification of target and amplification of components rather than the target. Furthermore, existing evidence and the role of various signaling pathways like EGFR, Ras, PI3K/Akt, Wnt, Notch, TGF-β, Integrin-ECM signaling in drug resistance are explained. Lastly, the prevention of this resistance by a contemporary therapeutic strategy, i.e., a combination of specific signaling pathway inhibitors and the cocktail of a cancer drug is summarized showing the new treatment strategies.

Cysteine-rich protein 61 regulates the chemosensitivity of chronic myeloid leukemia to imatinib mesylate through the nuclear factor kappa B/Bcl-2 pathway

Although the targeted tyrosine kinase inhibitor imatinib mesylate (IM) has achieved significant responses against CML in the clinical setting, a small proportion of patients fail to respond to IM treatment and their disease continues to progress, indicating resistance to IM therapy. As a secreted extracellular matrix protein, cysteine‐rich protein 61 (Cyr61) plays an important role in the resistance of solid tumors to chemotherapy, but its role in CML is unclear. In the present study, we observed that Cyr61 levels were upregulated in the plasma and bone marrow (BM) of patients with CML as well as in K562 cells. This upregulation of Cyr61 significantly decreased IM‐induced cellular apoptosis of K562 cells through nuclear factor kappa B/B‐cell lymphoma 2 pathways. Inhibition of Cyr61 restored the chemosensitivity of K562 cells to IM both in vitro and in vivo. Thus, our results showed for the first time that Cyr61 plays an important role in regulating the chemosensitivity of CML cells to IM, suggesting that selectively targeting Cyr61 directly or its relevant effector pathways may provide potential value in improving the clinical response of patients with CML to IM treatment.

Secretion of fibronectin by human pancreatic stellate cells promotes chemoresistance to gemcitabine in pancreatic cancer cells

Background

Gemcitabine remains a cornerstone in chemotherapy of pancreatic ductal adenocarcinoma (PDAC) despite suboptimal clinical effects that are partly due to the development of chemoresistance. Pancreatic stellate cells (PSCs) of the tumor stroma are known to interact with pancreatic cancer cells (PCCs) and influence the progression of PDAC through a complex network of signaling molecules that involve extracellular matrix (ECM) proteins. To understand tumor-stroma interactions regulating chemosensitivity, the role of PSC-secreted fibronectin (FN) in the development of gemcitabine resistance in PDAC was examined.

Methods

PSC cultures obtained from ten different human PDAC tumors were co-cultured with PCC lines (AsPC-1, BxPC-3, Capan-2, HPAF-II, MIA PaCa-2, PANC-1 and SW-1990) either directly, or indirectly via incubation with PSC-conditioned medium (PSC-CM). Gemcitabine dose response cytotoxicity was determined using MTT based cell viability assays. Protein expression was assessed by western blotting and immunofluorescence. PSC-CM secretome analysis was performed by proteomics-based LC-MS/MS, and FN content in PSC-CM was determined with ELISA. Radiolabeled gemcitabine was used to determine the capacity of PCCs to uptake the drug.

Results

In both direct and indirect co-culture, PSCs induced varying degrees of resistance to the cytotoxic effects of gemcitabine among all cancer cell lines examined. A variable degree of increased phosphorylation of ERK1/2 was observed across all PCC lines upon incubation with PSC-CM, while activation of AKT was not detected. Secretome analysis of PSC-CM identified 796 different proteins, including several ECM-related proteins such as FN and collagens. Soluble FN content in PSC-CM was detected in the range 175–350 ng/ml. Neither FN nor PSC-CM showed any effect on PCC uptake capacity of gemcitabine. PCCs grown on FN-coated surface displayed higher resistance to gemcitabine compared to cells grown on non-coated surface. Furthermore, a FN inhibitor, synthetic Arg-Gly-Asp-Ser (RGDS) peptide significantly inhibited PSC-CM-induced chemoresistance in PCCs via downregulation of ERK1/2 phosphorylation.

Conclusions

The findings of this study suggest that FN secreted by PSCs in the ECM plays a key role in the development of resistance to gemcitabine via activation of ERK1/2. FN-blocking agents added to gemcitabine-based chemotherapy might counteract chemoresistance in PDAC and provide better clinical outcomes.

Electronic supplementary material

The online version of this article (10.1186/s12885-019-5803-1) contains supplementary material, which is available to authorized users.