SMAD4 loss triggers the phenotypic changes of pancreatic ductal adenocarcinoma cells

Differential Sensitivity to Ionizing Radiation in Gemcitabine-Resistant and Paclitaxel-Resistant Pancreatic Cancer Cells

PURPOSE

Chemoresistance remains a major challenge in treating pancreatic ductal adenocarcinoma (PDAC). Although chemoradiation has proven effective in other tumor types, such as head and neck squamous cell carcinoma, its role in PDAC and effect on acquired chemoresistance have yet to be fully explored. In this study, we investigated the sensitivity of gemcitabine-resistant (GR) and paclitaxel-resistant (PR) PDAC cells to ionizing radiation (IR) and their underlying mechanisms.

METHODS AND MATERIALS

GR and PR clones were generated from PANC-1, PATU-T, and SUIT2-007 pancreatic cancer cell lines. Cell survival after radiation was assessed using clonogenic assay, sulforhodamine B assay, apoptosis, and spheroid growth by bioluminescence. Radiation-induced DNA damage was assessed using Western blot, extra-long polymerase chain reaction, reactive oxygen species production, and immunofluorescence. Autophagy and modulation of the Hippo signaling pathway were investigated using proteomics, Western blot, immunofluorescence, and reverse-transcription quantitative polymerase chain reaction.

RESULTS

In both 2- and 3-dimensional settings, PR cells were more sensitive to IR and showed decreased β-globin amplification, indicating more DNA damage accumulation compared with GR or wild-type cells after 24 hours. Proteomic analysis of PR PATU-T cells revealed that the protein MST4, a kinase involved in autophagy and the Hippo signaling pathway, was highly downregulated. A differential association was found between autophagy and radiation treatment depending on the cell model. Interestingly, increased yes-associated protein nuclear localization and downstream Hippo signaling pathway target gene expression were observed in response to IR.

CONCLUSIONS

This was the first study investigating the potential of IR in targeting PDAC cells with acquired chemoresistance. Our results demonstrate that PR cells exhibit enhanced sensitivity to IR due to greater accumulation of DNA damage. Additionally, depending on the specific cellular context, radiation-induced modulation of autophagy and the Hippo signaling pathway emerged as potential underlying mechanisms, findings with potential to inform personalized treatment strategies for patients with acquired chemoresistance.

SMAD4 endows TGF-β1-induced highly invasive tumor cells with ferroptosis vulnerability in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is an extremely aggressive malignancy prone to recurrence and metastasis. Studies show that tumor cells with increased invasive and metastatic potential are more likely to undergo ferroptosis. SMAD4 is a critical molecule in the transforming growth factor β (TGF-β) pathway, which affects the TGF-β-induced epithelial-mesenchymal transition (EMT) status. SMAD4 loss is observed in more than half of patients with PDAC. In this study, we investigated whether SMAD4-positive PDAC cells were prone to ferroptosis because of their high invasiveness. We showed that SMAD4 status almost determined the orientation of transforming growth factor β1 (TGF-β1)-induced EMT via the SMAD4-dependent canonical pathway in PDAC, which altered ferroptosis vulnerability. We identified glutathione peroxidase 4 (GPX4), which inhibited ferroptosis, as a SMAD4 down-regulated gene by RNA sequencing. We found that SMAD4 bound to the promoter of GPX4 and decreased GPX4 transcription in PDAC. Furthermore, TGF-β1-induced high invasiveness enhanced sensitivity of SMAD4-positive organoids and pancreas xenograft models to the ferroptosis inducer RAS-selective lethal 3 (RSL3). Moreover, SMAD4 enhanced the cytotoxic effect of gemcitabine combined with RSL3 in highly invasive PDAC cells. This study provides new ideas for the treatment of PDAC, especially SMAD4-positive PDAC.

Biological characteristics of pancreatic ductal adenocarcinoma: Initiation to malignancy, intracellular to extracellular

Pancreatic ductal adenocarcinoma (PDAC) is a highly life-threatening tumour with a low early-detection rate, rapid progression and a tendency to develop resistance to chemotherapy. Therefore, understanding the regulatory mechanisms underlying the initiation, development and metastasis of pancreatic cancer is necessary for enhancing therapeutic effectiveness. In this review, we summarised single-gene mutations (including KRAS, CDKN2A, TP53, SMAD4 and some other less prevalent mutations), epigenetic changes (including DNA methylation, histone modifications and RNA interference) and large chromosome alterations (such as copy number variations, chromosome rearrangements and chromothripsis) associated with PDAC. In addition, we discussed variations in signalling pathways that act as intermediate oncogenic factors in PDAC, including PI3K/AKT, MAPK/ERK, Hippo and TGF-β signalling pathways. The focus of this review was to investigate alterations in the microenvironment of PDAC, particularly the role of immunosuppressive cells, cancer-associated fibroblasts, lymphocytes, other para-cancerous cells and tumour extracellular matrix in tumour progression. Peripheral axons innervating the pancreas have been reported to play a crucial role in the development of cancer. In addition, tumour cells can influence the behaviour of neighbouring non-tumour cells by secreting certain factors, both locally and at a distance. In this review, we elucidated the alterations in intracellular molecules and the extracellular environment that occur during the progression of PDAC. Altogether, this review may enhance the understanding of the biological characteristics of PDAC and guide the development of more precise treatment strategies.

S100A2 induces epithelial-mesenchymal transition and metastasis in pancreatic cancer by coordinating transforming growth factor β signaling in SMAD4-dependent manner

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive tumor and is associated with a poor prognosis. Treatment strategies for PDAC are largely ineffective primarily because of delay in its diagnosis and limited efficacy of systematic treatment. S100A2 is associated with the proliferation, migration, and differentiation of several tumors; however, its effects on PDAC and the associated molecular mechanisms remain to be explored. We studied the mechanisms underlying the effect of S100A2 on epithelial-mesenchymal transition (EMT) and metastasis in PDAC cells. We found that the level of S100A2 remarkably increased and was associated with poor PDAC prognosis. The overexpression of S100A2 in PANC-1 cells also induced EMT, in addition to increasing the invasion and migration of PDAC cells, whereas the knockdown of S100A2 markedly inhibited cell metastasis. Furthermore, S100A2 was found to enhance metastatic abilities in vivo. The overexpression of S100A2 increased SMAD4 expression, whereas the knockdown of S100A2 reduced SMAD4 expression. SMAD4 overexpression could effectively rescue the effects of S100A2 knockdown on EMT. S100A2 mechanistically activated the transforming growth factor (TGF)-β/Smad2/3 signaling pathway, upregulated SMAD4 expression, induced EMT, and increased PANC-1 cell metastasis. In conclusion, the S100A2/SMAD4 axis modulates EMT to accelerate PDAC development. Our results supplement and enrich the understanding of the pathogenesis underlying PDAC and provide a new theoretical basis and strategy targeting S100A2 for the diagnosis and treatment of PDAC.

Mitoxantrone and Mitoxantrone-Loaded Iron Oxide Nanoparticles Induce Cell Death in Human Pancreatic Ductal Adenocarcinoma Cell Spheroids

Pancreatic ductal adenocarcinoma is a hard-to-treat, deadly malignancy. Traditional treatments, such as surgery, radiation and chemotherapy, unfortunately are still not able to significantly improve long-term survival. Three-dimensional (3D) cell cultures might be a platform to study new drug types in a highly reproducible, resource-saving model within a relevant pathophysiological cellular microenvironment. We used a 3D culture of human pancreatic ductal adenocarcinoma cell lines to investigate a potential new treatment approach using superparamagnetic iron oxide nanoparticles (SPIONs) as a drug delivery system for mitoxantrone (MTO), a chemotherapeutic agent. We established a PaCa DD183 cell line and generated PANC-1^{SMAD4 (-/-)} cells by using the CRISPR-Cas9 system, differing in a prognostically relevant mutation in the TGF-β pathway. Afterwards, we formed spheroids using PaCa DD183, PANC-1 and PANC-1^{SMAD4 (-/-)} cells, and analyzed the uptake and cytotoxic effect of free MTO and MTO-loaded SPIONs by microscopy and flow cytometry. MTO and SPION-MTO-induced cell death in all tumor spheroids in a dose-dependent manner. Interestingly, spheroids with a SMAD4 mutation showed an increased uptake of MTO and SPION-MTO, while at the same time being more resistant to the cytotoxic effects of the chemotherapeutic agents. MTO-loaded SPIONs, with their ability for magnetic drug targeting, could be a future approach for treating pancreatic ductal adenocarcinomas.

KRAS Mutation Variants and Co-occurring PI3K Pathway Alterations Impact Survival for Patients with Pancreatic Ductal Adenocarcinomas

BACKGROUND

KRAS variant alleles may have differential biological properties which impact prognosis and therapeutic options in pancreatic ductal adenocarcinomas (PDA).

MATERIALS AND METHODS

We retrospectively identified patients with advanced PDA who received first-line therapy and underwent blood and/or tumor genomic sequencing at the University of Washington between 2013 and 2020. We examined the incidence of KRAS mutation variants with and without co-occurring PI3K or other genomic alterations and evaluated the association of these mutations with clinicopathological characteristics and survival using a Cox proportional hazards model.

RESULTS

One hundred twenty-six patients had genomic sequencing data; KRAS mutations were identified in 111 PDA and included the following variants: G12D (43)/G12V (35)/G12R (23)/other (10). PI3K pathway mutations (26% vs. 8%) and homologous recombination DNA repair (HRR) defects (35% vs. 12.5%) were more common among KRAS G12R vs. non-G12R mutated cancers. Patients with KRAS G12R vs. non-G12R cancers had significantly longer overall survival (OS) (HR 0.55) and progression-free survival (PFS) (HR 0.58), adjusted for HRR pathway co-mutations among other covariates. Within the KRAS G12R group, co-occurring PI3K pathway mutations were associated with numerically shorter OS (HR 1.58), while no effect was observed on PFS.

CONCLUSIONS

Patients with PDA harboring KRAS G12R vs. non-G12R mutations have longer survival, but this advantage was offset by co-occurring PI3K alterations. The KRAS/PI3K genomic profile could inform therapeutic vulnerabilities in patients with PDA.

An EGFR/HER2-targeted conjugate sensitizes gemcitabine-sensitive and resistant pancreatic cancer through different SMAD4-mediated mechanisms

Chemoresistance limits its clinical implementation for pancreatic ductal adenocarcinoma (PDAC). We previously generated an EGFR/HER2 targeted conjugate, dual-targeting ligand-based lidamycin (DTLL), which shows a highly potent antitumor effect. To overcome chemoresistance in PDAC, we aim to study DTLL efficacy when combined with gemcitabine and explore its mechanisms of action. DTLL in combination with gemcitabine show a superior inhibitory effect on the growth of gemcitabine-resistant/sensitive tumors. DTLL sensitizes gemcitabine efficacy via distinct action mechanisms mediated by mothers against decapentaplegic homolog 4 (SMAD4). It not only prevents neoplastic proliferation via ATK/mTOR blockade and NF-κB impaired function in SMAD4-sufficient PDACs, but also restores SMAD4 bioactivity to trigger downstream NF-κB-regulated signaling in SMAD4-deficient tumors and to overcome chemoresistance. DTLL seems to act as a SMAD4 module that normalizes its function in PDAC, having a synergistic effect in combination with gemcitabine. Our findings provide insight into a rational SMAD4-directed precision therapy in PDAC.

Chemoresistance is a main limitation for the treatment of pancreatic ductal adenocarcinoma (PDAC). Here, the authors show that an antibody drug conjugate-like compound targeting both EGFR and HER2 overcomes gemcitabine resistance in PDAC preclinical models by mechanisms involving the tumour suppressor SMAD4.

Spatiotemporal modulation of SMAD4 by HBx is required for cellular proliferation in hepatitis B-related liver cancer

PURPOSE

Hepatitis B virus (HBV) plays a crucial role in the progression of hepatocellular carcinoma (HCC). It is known that HBV-encoded X protein (HBx) can induce genetic alterations in some oncogenes and that SMAD4 is relevant for the development of some cancers, especially HBV-related HCC. Previously, it has been reported that HBx can promote SMAD4 protein expression in liver fibrosis and HCC but, as yet, its regulatory mechanism has not been fully elucidated. Here, we aimed to investigate the correlation between and regulatory mechanism behind HBx and SMAD4 in HCC.

METHODS

mRNA and protein expression of SMAD4 in HCC tissues was detected by qRT-PCR, Western blotting and IHC. CCK-8 and colony forming assays, as well as xenograft murine models were used to evaluate the effects of HBx and SMAD4 on the proliferation and tumorigenicity of HCC cells. Luciferase reporter, immunofluorescence, Co-IP and truncation assays were performed to assess the regulatory relationship between HBx and SMAD4.

RESULTS

We found that SMAD4 was highly expressed in HBV-positive HCC patient samples and correlated with a poor prognosis. The proliferation of HCC cells with a high SMAD4 expression was found to be enhanced in vitro and in vivo, and knocking down HBx while replenishing SMAD4 rescued HCC cell proliferation. Mechanically, we found that HBx regulates SMAD4 expression at the transcriptional level via TFII-I and can bind to SMAD4 to repress its ubiquitination. The binding region comprised the MH2 domain of SMAD4. Furthermore, we found that SMAD4 can promote HBx expression through a positive feedback mechanism.

CONCLUSIONS

From our data we conclude that SMAD4 is modulated spatiotemporally via both transcriptional activation and protein stabilization by HBx in HCC cells. Our data shed light on the molecular mechanism underlying HBx-induced hepatocarcinogenesis.

Evidence for a novel, effective approach to targeting carcinoma catabolism exploiting the first-in-class, anti-cancer mitochondrial drug, CPI-613

Clinical targeting of the altered metabolism of tumor cells has long been considered an attractive hypothetical approach. However, this strategy has yet to perform well clinically. Metabolic redundancy is among the limitations on effectiveness of many approaches, engendering intrinsic single-agent resistance or efficient evolution of such resistance. We describe new studies of the multi-target, tumor-preferential inhibition of the mitochondrial tricarboxylic acid (TCA) cycle by the first-in-class drug CPI-613® (devimistat). By suppressing the TCA hub, indispensable to many metabolic pathways, CPI-613 substantially reduces the effective redundancy of tumor catabolism. This TCA cycle suppression also engenders an apparently homeostatic accelerated, inefficient consumption of nutrient stores in carcinoma cells, eroding some sources of drug resistance. Nonetheless, sufficiently abundant, cell line-specific lipid stores in carcinoma cells are among remaining sources of CPI-613 resistance in vitro and during the in vivo pharmacological drug pulse. Specifically, the fatty acid beta-oxidation step delivers electrons directly to the mitochondrial electron transport system (ETC), by-passing the TCA cycle CPI-613 target and producing drug resistance. Strikingly, tested carcinoma cell lines configure much of this fatty acid flow to initially traverse the peroxisome enroute to additional mitochondrial beta-oxidation. This feature facilitates targeting as clinically practical agents disrupting this flow are available. Two such agents significantly sensitize an otherwise fully CPI-613-resistant carcinoma xenograft in vivo. These and related results are strong empirical support for a potentially general class of strategies for enhanced clinical targeting of carcinoma catabolism.

Thymidine phosphorylase induction by ionizing radiation antagonizes 5-fluorouracil resistance in human ductal pancreatic adenocarcinoma

Chemoresistance in pancreatic ductal adenocarcinoma (PDAC) frequently contributes to failure of systemic therapy. While the radiosensitizing properties of 5-fluorouracil (FU) are well known, it is unknown whether ionizing radiation (IR) sensitizes towards FU cytotoxicity. Here, we hypothesize that upregulation of thymidine phosphorylase (TP) by IR reverses FU chemoresistance in PDAC cells. The FU resistant variant of the human PDAC cell line AsPC-1 (FU-R) was used to determine the sensitizing effects of IR. Proliferation rates of FU sensitive parental (FU-S) and FU-R cells were determined by WST-1 assays after low (0.05 Gy) and intermediate dose (2.0 Gy) IR followed by FU treatment. TP protein expression in PDAC cells before and after IR was assessed by Western blot. To analyze the specificity of the FU sensitizing effect, TP was ablated by siRNA. FU-R cells showed a 2.7-fold increase of the half maximal inhibitory concentration, compared to FU-S parental cells. Further, FU-R cells showed a concomitant IR resistance towards both doses applied. When challenging both cell lines with FU after IR, FU-R cells had lower proliferation rates than FU-S cells, suggesting a reversal of chemoresistance by IR. This FU sensitizing effect was abolished when TP was blocked by anti-TP siRNA before IR. An increase of TP protein expression was seen after both IR doses. Our results suggest a TP dependent reversal of FU-chemoresistance in PDAC cells that is triggered by IR. Thus, induction of TP expression by low dose IR may be a therapeutic approach to potentially overcome FU chemoresistance in PDAC.

Piperlongumine induces ROS mediated apoptosis by transcriptional regulation of SMAD4/P21/P53 genes and synergizes with doxorubicin in osteosarcoma cells

Piperlongumine is a herbal drug, with well-known anti-microbial and anti-neoplastic properties. The anti-carcinogenic potential of piperlongumine has been extensively explored for breast, colorectal, lungs, pancreatic, prostate, and oral carcinoma. However, a few numbers of studies are available on its bio-activity in osteosarcoma. Therefore, the present study aimed at exploring the therapeutic potential and possible mechanisms of action of piperlongumine in three human osteosarcoma cell lines in-vitro. The cytotoxicity of piperlongumine was determined by MTT assay, which shows dose and time-dependent inhibition of MG-63, 143B and KHOS/NP cells. Piperlongumine arrest the cells in G2/M phase of cell cycle and increases reactive oxygen species production, which possibly leads to lethal oxidative stress and apoptosis. Piperlongumine treatment significantly upregulated the expression of genes BAX, P21, P53, and SMAD4; while the BCL-2, SURVIVIN, TNFA, and NFKB genes expression was found down-regulated. Furthermore, piperlongumine exposure inhibited the migration of osteosarcoma cells as the expression of migration marker genes CDH2, CTNNB1, FN1, and TWIST were found to be down-regulated. The drug combination studies show the synergistic effect of piperlongumine with the conventional chemotherapeutic drug doxorubicin in osteosarcoma cells. Taken together, the above results suggest that PL displays anticancer properties against osteosarcoma and can be used as a therapeutic agent for osteosarcoma treatment in clinical settings.

The Role of SMAD4 Inactivation in Epithelial-Mesenchymal Plasticity of Pancreatic Ductal Adenocarcinoma: The Missing Link?

Simple Summary

Pancreatic ductal adenocarcinoma (PDAC) is currently one of the deadliest cancers. Despite the progress that has been made in the research of patient care and the understanding of pancreatic cancer, the survival rate remains mediocre. SMAD4, a tumor-suppressor gene, is specifically inactivated in 50–55% of pancreatic cancers. The role of SMAD4 protein loss in PDAC remains controversial, but seems to be associated with worse overall survival and metastasis. Here, we review the function of SMAD4 inactivation in the context of a specific biological process called epithelial–mesenchymal transition, as it has been increasingly associated with tumor formation, metastasis and resistance to therapy. By improving our understanding of these molecular mechanisms, we hope to find new targets for therapy and improve the care of patients with PDAC.

Abstract

Pancreatic ductal adenocarcinoma (PDAC) presents a five-year survival rate of 10% and its incidence increases over the years. It is, therefore, essential to improve our understanding of the molecular mechanisms that promote metastasis and chemoresistance in PDAC, which are the main causes of death in these patients. SMAD4 is inactivated in 50% of PDACs and its loss has been associated with worse overall survival and metastasis, although some controversy still exists. SMAD4 is the central signal transducer of the transforming growth factor-beta (TGF-beta) pathway, which is notably known to play a role in epithelial–mesenchymal transition (EMT). EMT is a biological process where epithelial cells lose their characteristics to acquire a spindle-cell phenotype and increased motility. EMT has been increasingly studied due to its potential implication in metastasis and therapy resistance. Recently, it has been suggested that cells undergo EMT transition through intermediary states, which is referred to as epithelial–mesenchymal plasticity (EMP). The intermediary states are characterized by enhanced aggressiveness and more efficient metastasis. Therefore, this review aims to summarize and analyze the current knowledge on SMAD4 loss in patients with PDAC and to investigate its potential role in EMP in order to better understand its function in PDAC carcinogenesis.

Loss of SMAD4 Is Associated With Poor Tumor Immunogenicity and Reduced PD-L1 Expression in Pancreatic Cancer

Transforming Growth Factor β (TGFβ) is a key mediator of immune evasion in pancreatic ductal adenocarcinoma (PDAC), and the addition of TGFβ inhibitors in select immunotherapy regimens shows early promise. Though the TGFβ target SMAD4 is deleted in approximately 55% of PDAC tumors, the effects of SMAD4 loss on tumor immunity have yet to be fully explored. Using a combination of genomic databases and PDAC specimens, we found that tumors with loss of SMAD4 have a comparatively poor T-cell infiltrate. SMAD4 loss was also associated with a reduction in several chemokines with known roles in T-cell recruitment, which was recapitulated using knockdown of SMAD4 in PDAC cell lines. Accordingly, JURKAT T-cells were poorly attracted to conditioned media from PDAC cells with knockdown of SMAD4 and lost their ability to produce IFNγ. However, while exogenous TGFβ modestly reduced PD-L1 expression in SMAD4-intact cell lines, SMAD4 and PD-L1 positively correlated in human PDAC samples. PD-L1 status was closely related to tumor-infiltrating lymphocytes, particularly IFNγ-producing T-cells, which were more abundant in SMAD4-expressing tumors. Low concentrations of IFNγ upregulated PD-L1 in tumor cells in vitro, even when administered alongside high concentrations of TGFβ. Hence, while SMAD4 may have a modest inhibitory effect on PD-L1 in tumor cells, SMAD4 indirectly promotes PD-L1 expression in the pancreatic tumor microenvironment by enhancing T-cell infiltration and IFNγ biosynthesis. These data suggest that pancreatic cancers with loss of SMAD4 represent a poorly immunogenic disease subtype, and SMAD4 status warrants further exploration as a predictive biomarker for cancer immunotherapy.

TGFβ Signaling in the Pancreatic Tumor Microenvironment

Pancreatic ductal adenocarcinoma (PDAC) is associated with poor clinical outcomes, largely attributed to incomplete responses to standard therapeutic approaches. Recently, selective inhibitors of the Transforming Growth Factor β (TGFβ) signaling pathway have shown early promise in the treatment of PDAC, particularly as a means of augmenting responses to chemo- and immunotherapies. However, TGFβ is a potent and pleiotropic cytokine with several seemingly paradoxical roles within the pancreatic tumor microenvironment (TME). Although TGFβ signaling can have potent tumor-suppressive effects in epithelial cells, TGFβ signaling also accelerates pancreatic tumorigenesis by enhancing epithelial-to-mesenchymal transition (EMT), fibrosis, and the evasion of the cytotoxic immune surveillance program. Here, we discuss the known roles of TGFβ signaling in pancreatic carcinogenesis, the biologic consequences of the genetic inactivation of select components of the TGFβ pathway, as well as past and present attempts to advance TGFβ inhibitors in the treatment of PDAC patients.

Hypoxic microenvironment induced spatial transcriptome changes in pancreatic cancer

OBJECTIVE

Hypoxia is a significant feature of solid tumors, including pancreatic ductal adenocarcinoma (PDAC). It is associated with tumor invasion, metastasis, and drug resistance. However, the spatial distribution of hypoxia-related heterogeneity in PDAC remains unclear.

METHODS

Spatial transcriptomics (STs), a new technique, was used to investigate the ST features of engrafted human PDAC in the ischemic hind limbs of nude mice. Transcriptomes from ST spots in the hypoxic tumor and the control were clustered using differentially-expressed genes. These data were compared to determine the spatial organization of hypoxia-induced heterogeneity in PDAC. Clinical relevance was validated using the Tumor Cancer Genome Atlas and KM-plotter databases. The CMAP website was used to identify molecules that may serve as therapeutic targets for PDAC.

RESULTS

ST showed that the tumor cell subgroups decreased to 7 subgroups in the hypoxia group, compared to 9 subgroups in the control group. Different subgroups showed positional characteristics and different gene signatures. Subgroup 6 located at the invasive front showed a higher proliferative ability under hypoxia. Subgroup 6 had active functions including cell proliferation, invasion, and response to stress. Expressions of hypoxia-related genes, LDHA, TPI1, and ENO1, induced changes. CMAP analysis indicated that ADZ-6482, a PI3K inhibitor, was targeted by the invasive subgroup in hypoxic tumors.

CONCLUSIONS

This study is the first to describe hypoxic microenvironment-induced spatial transcriptome changes in PDAC, and to identify potential treatment targets for PDAC. These data will provide the basis for further investigations of the prognoses and treatments of hypoxic tumors.

SMAD4 loss limits the vulnerability of pancreatic cancer cells to complex I inhibition via promotion of mitophagy

Pancreatic cancer is one of the deadliest forms of cancer, which is attributed to lack of effective treatment options and drug resistance. Mitochondrial inhibitors have emerged as a promising class of anticancer drugs, and several inhibitors of the electron transport chain (ETC) are being clinically evaluated. We hypothesized that resistance to ETC inhibitors from the biguanide class could be induced by inactivation of SMAD4, an important tumor suppressor involved in transforming growth factor β (TGFβ) signaling, and associated with altered mitochondrial activity. Here we show that, paradoxically, both TGFβ-treatment and the loss of SMAD4, a downstream member of TGFβ signaling cascade, induce resistance to biguanides, decrease mitochondrial respiration, and fragment the mitochondrial network. Mechanistically, the resistance of SMAD4-deficient cells is mediated by increased mitophagic flux driven by MAPK/ERK signaling, whereas TGFβ-induced resistance is autophagy-independent and linked to epithelial-to-mesenchymal transition (EMT). Interestingly, mitochondria-targeted tamoxifen, a complex I inhibitor under clinical trial, overcomes resistance mediated by SMAD4-deficiency or TGFβ signaling. Our data point to differential mechanisms underlying the resistance to treatment in PDAC arising from TGFβ signaling and SMAD4 loss, respectively. The findings will help the development of mitochondria-targeted therapy for pancreatic cancer patients with SMAD4 as a plausible predictive marker.

Tumor-Stromal Interactions in a Co-Culture Model of Human Pancreatic Adenocarcinoma Cells and Fibroblasts and Their Connection with Tumor Spread

One key feature of pancreatic ductal adenocarcinoma (PDAC) is a dense desmoplastic reaction that has been recognized as playing important roles in metastasis and therapeutic resistance. We aim to study tumor-stromal interactions in an in vitro coculture model between human PDAC cells (Capan-1 or PL-45) and fibroblasts (LC5). Confocal immunofluorescence, Enzyme-Linked Immunosorbent Assay (ELISA), and Western blotting were used to evaluate the expressions of activation markers; cytokines arrays were performed to identify secretome profiles associated with migratory and invasive properties of tumor cells; extracellular vesicle production was examined by ELISA and transmission electron microscopy. Coculture conditions increased FGF-7 secretion and α-SMA expression, characterized by fibroblast activation and decreased epithelial marker E-cadherin in tumor cells. Interestingly, tumor cells and fibroblasts migrate together, with tumor cells in forming a center surrounded by fibroblasts, maximizing the contact between cells. We show a different mechanism for tumor spread through a cooperative migration between tumor cells and activated fibroblasts. Furthermore, IL-6 levels change significantly in coculture conditions, and this could affect the invasive and migratory capacities of cells. Targeting the interaction between tumor cells and the tumor microenvironment might represent a novel therapeutic approach to advanced PDAC.

Smad4 deficiency substitutes Cdkn2b but not Cdkn2a downregulation in pancreatic cancer following induction of genetic events in adult mice

BACKGROUND

Minor progress in pancreatic cancer treatment and prognosis implies that more reliable animal models are urgently needed to decipher its molecular mechanisms and preclinical research. We recently reported a genetically engineered adult mouse model where Cdkn2b downregulation was required together with Cdkn2a downregulation to inactivate the Rb pathway. Besides, the role of Smad4, which is mutated more frequently than Cdkn2b in human pancreatic cancer, was determined critical on the development of the pancreas tumor by some reports. However, the impact of Smad4 deficiency in combination with PDAC-relevant mutations, such as Cdkn2a when induced in adult pancreas has not been completely elucidated in mice.

METHODS

Lentiviral delivered oncogene/tumor suppressors in adult pancreas. The development of pancreatic cancer was monitored. Hematoxylin and eosin staining and immunofluorescence were performed for pathological identification of the pancreatic cancer. Real-time polymerase chain reaction, immunofluorescence and western blot were used to test gene expression.

RESULTS

Loss of Smad4 could cooperate with alterations of KRAS, Trp53, and Cdkn2a to induce pancreatic cancer in adult mice. The role of Smad4 was mainly in downregulating the expression of Cdkn2b and further inducing phosphorylation of the Rb1 protein.

CONCLUSIONS

These findings show an essential role of Smad4 deficiency in pancreatic ductal adenocarcinoma (PDAC) formation. This model better recapitulates the adult onset, clonal origin, and genetic alterations in human PDAC and can be simply generated on a large-scale.

Molecular Alterations in Pancreatic Cancer: Transfer to the Clinic

Pancreatic ductal adenocarcinoma (PDA) is the most common cancer of the exocrine pancreas and probably the tumor that has benefited the least from clinical progress in the last three decades. A consensus has been reached regarding the histologic classification of the ductal preneoplastic lesions (pancreatic intra-epithelial neoplasia-PanIN) and the molecular alterations associated with them. Mutations in KRAS and inactivation of CDKN2A, SMAD4 and TP53 are among the most prevalent alterations. Next generation sequencing studies are providing a broad picture of the enormous heterogeneity in this tumor type, describing new mutations less prevalent. These studies have also allowed the characterization of different subtypes with prognostic value. However, all this knowledge has not been translated into a clinical progress. Effective preventive and early diagnostic strategies are essential to improve the survival rates. The main challenge is, indeed, to identify new effective drugs. Despite many years of research and its limited success, gemcitabine is still the first line treatment of PDA. New drug combinations and new concepts to improve drug delivery into the tumor, as well as the development of preclinical predictive assays, are being explored and provide optimism and prospects for better therapies.

CircATRNL1 activates Smad4 signaling to inhibit angiogenesis and ovarian cancer metastasis via miR-378

Ovarian cancer is one of the most frequent carcinomas in females, and the occurrence rate is still rising despite many advances made. The pathogenesis of ovarian cancer remains greatly unclear. Here, we investigated the mechanisms of ovarian cancer, with the focus on circATRNL1. Human ovarian cancer tissues and cell lines were used to examine levels of circATRNL1, miR‐378, Smad4, AKT, and other proliferation‐related and migration‐related proteins. Cellular assays were used to determine cancer cell proliferation, invasion, migration, apoptosis, and angiogenesis. We validated the interactions of circATRNL1/miR‐378 and miR‐378/Smad4, and a mouse tumor xenograft model was employed to assess the effect of circATRNL1 on tumor growth and metastasis in vivo. We found that circATRNL1 was decreased while miR‐378 was increased in human ovarian cancer tissues and cells. circATRNL1 bound to miR‐378 while miR‐378 directly targeted Smad4. Overexpression of circATRNL1 or knockdown of miR‐378 suppressed angiogenesis and ovarian cancer cell proliferation, invasion, and migration via decreasing proliferation‐ and migration‐related proteins via miR‐378 or Smad4, respectively. Overexpression of circATRNL1 restrained ovarian cancer growth and abdominal metastasis in vivo. Our findings indicate that circATRNL1 acts as a miR‐378 sponge to active Smad4 signaling and suppresses angiogenesis and ovarian cancer metastasis.

SMAD4-Expressing Pancreatic Ductal Adenocarcinomas Have Better Response to Neoadjuvant Therapy and Significantly Lower Lymph Node Metastasis Rates

OBJECTIVE

For many patients whose pancreatic ductal adenocarcinoma (PDAC) is locally advanced, neoadjuvant therapy has been proposed as a way to decrease tumor burden. Pancreatic ductal adenocarcinoma is generally thought to be resistant to chemotherapy and radiation, however, response to neoadjuvant therapy in PDAC has been described in a subset of patients. The SMAD4 status is considered to be an important molecular feature which distinguishes two subsets of PDAC, SMAD4-positive and -negative tumors. The objective of this study was to evaluate the neoadjuvant treatment response rate as well as compare the different clinicopathologic variables between SMAD4-positive and -negative tumors.

METHODS

We analyzed the data of patients who underwent surgical resection for PDAC from 2009-2019. Our cohort from a single institution included 233 patients.

RESULTS

Of the 233 cases, 143 (61.4%) were SMAD4-negative and 90 (38.6%) were SMAD4-positive. Overall, SMAD4-positive tumors with neoadjuvant therapy had better treatment response and better tumor regression scores. In addition, SMAD4-positive tumors had a significantly lower lymph node metastasis rate in both the neoadjuvant and nonneoadjuvant setting.

CONCLUSIONS

Further characterization of the role of SMAD4 within the context of neoadjuvant therapy will lead to improved personalized therapeutic strategies.

Identifying Drug Sensitivity Subnetworks with NETPHIX

Phenotypic heterogeneity in cancer is often caused by different patterns of genetic alterations. Understanding such phenotype-genotype relationships is fundamental for the advance of personalized medicine. We develop a computational method, named NETPHIX (NETwork-to-PHenotype association with eXclusivity) to identify subnetworks of genes whose genetic alterations are associated with drug response or other continuous cancer phenotypes. Leveraging interaction information among genes and properties of cancer mutations such as mutual exclusivity, we formulate the problem as an integer linear program and solve it optimally to obtain a subnetwork of associated genes. Applied to a large-scale drug screening dataset, NETPHIX uncovered gene modules significantly associated with drug responses. Utilizing interaction information, NETPHIX modules are functionally coherent and can thus provide important insights into drug action. In addition, we show that modules identified by NETPHIX together with their association patterns can be leveraged to suggest drug combinations.

Circadian Dysregulation of the TGFβ/SMAD4 Pathway Modulates Metastatic Properties and Cell Fate Decisions in Pancreatic Cancer Cells

Impairment of circadian rhythms impacts carcinogenesis. SMAD4, a clock-controlled gene and central component of the TGFβ canonical pathway, is frequently mutated in pancreatic ductal adenocarcinoma (PDA), leading to decreased survival. Here, we used an in vitro PDA model of SMAD4-positive and SMAD4-negative cells to investigate the interplay between circadian rhythms, the TGFβ canonical signaling pathway, and its impact on tumor malignancy. Our data show that TGFβ1, SMAD3, SMAD4, and SMAD7 oscillate in a circadian fashion in SMAD4-positive PDA cells, whereas altering the clock impairs the mRNA dynamics of these genes. Furthermore, the expression of the clock genes DEC1, DEC2, and CRY1 varied depending on SMAD4 status. TGFβ pathway activation resulted in an altered clock, cell-cycle arrest, accelerated apoptosis rate, enhanced invasiveness, and chemosensitivity. Our data suggest that the impact of TGFβ on the clock is SMAD4-dependent, and S MAD3, SMAD4, DEC1, and CRY1 involved in this cross-talk affect PDA patient survival.

SMAD4 and the TGFβ Pathway in Patients with Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is the fourth leading cause of cancer death worldwide. PDAC is an aggressive disease with an 11-month median overall survival and a five-year survival of less than 5%. Incidence of PDAC is constantly increasing and is predicted to become the second leading cause of cancer in Western countries within a decade. Despite research and therapeutic development, current knowledge about PDAC molecular mechanisms still needs improvements and it seems crucial to identify novel therapeutic targets. Genomic analyses of PDAC revealed that transforming growth factor β (TGFβ) signaling pathways are modified and the SMAD4 gene is altered in 47% and 60% of cases, respectively, highlighting their major roles in PDAC development. TGFβ can play a dual role in malignancy depending on the context, sometimes as an inhibitor and sometimes as an inducer of tumor progression. TGFβ signaling was identified as a potent inducer of epithelial-to-mesenchymal transition (EMT), a process that confers migratory and invasive properties to epithelial cells during cancer. Therefore, aberrant TGFβ signaling and EMT are linked to promoting PDAC aggressiveness. TGFβ and SMAD pathways were extensively studied but the mechanisms leading to cancer promotion and development still remain unclear. This review aims to describe the complex role of SMAD4 in the TGFβ pathway in patients with PDAC.

Differential Contributions of Actin and Myosin to the Physical Phenotypes and Invasion of Pancreatic Cancer Cells

INTRODUCTION

Metastasis is a fundamentally physical process in which cells deform through narrow gaps and generate forces to invade surrounding tissues. While it is commonly thought that increased cell deformability is an advantage for invading cells, we previously found that more invasive pancreatic ductal adenocarcinoma (PDAC) cells are stiffer than less invasive PDAC cells. Here we investigate potential mechanisms of the simultaneous increase in PDAC cell stiffness and invasion, focusing on the contributions of myosin II, Arp2/3, and formins.

METHOD

We measure cell invasion using a 3D scratch wound invasion assay and cell stiffness using atomic force microscopy (AFM). To determine the effects of actin- and myosin-mediated force generation on cell stiffness and invasion, we treat cells with pharmacologic inhibitors of myosin II (blebbistatin), Arp2/3 (CK-666), and formins (SMIFH2).

RESULTS

We find that the activity of myosin II, Arp2/3, and formins all contribute to the stiffness of PDAC cells. Interestingly, we find that the invasion of PDAC cell lines is differentially affected when the activity of myosin II, Arp2/3, or formins is inhibited, suggesting that despite having similar tissue origins, different PDAC cell lines may rely on different mechanisms for invasion.

CONCLUSIONS

These findings deepen our knowledge of the factors that regulate cancer cell mechanotype and invasion, and incite further studies to develop therapeutics that target multiple mechanisms of invasion for improved clinical benefit.

Differences between KC and KPC pancreatic ductal adenocarcinoma mice models, in terms of their modeling biology and their clinical relevance

Pancreatic ductal adenocarcinoma (PDAC) is among the dangerous human cancers, is the 10th highly prevalent cancer, and the fourth sole cause of cancer-related mortality in the United States of America. Notwithstanding the significant commitment, the forecast for people with this burden continues to have a five-year survival rate of just 4-6%. The most critical altered genes within PDAC consist of K-ras the proto-oncogene which is usually mutationally activated above 90% cases and tumor suppressors likeTrp53 are altered at 55%. To face the burden of pancreatic ductal adenocarcinoma, a variety of genetically engineered pancreatic cancer mice models have been created over the last past years. These models have distinctive features and are not all appropriate for preclinical studies. In this review, we focus on differences between two mice models K-ras^LSL.G12D/+;Pdx-1-Cre(KC) and K-ras^LSL.G12D/+; Trp53^R172H/+; Pdx-1-Cre(KPC) in terms of their modeling biology and their clinical relevance.

SMAD4 Y353C promotes the progression of PDAC

Background

SMAD4 is frequently inactivated and associated with a poor prognosis in pancreatic ductal adenocarcinoma (PDAC). Abnormal SMAD4 expression also plays an important role in the malignant progression of PDAC.

Methods

We investigated SMAD4 status in PDAC by immunohistochemical methods to explore the relationships between SMAD4 expression and clinicopathological features and then detected SMAD4 mutations by Sanger sequencing in 95 patients with PDAC to identify new mutation sites in PDAC. We further evaluated the effects of a missense mutation, Y353C, in the SMAD4 MH2 domain, on cell proliferation and migration in vitro.

Results

Immunohistochemistry showed that the expression of SMAD4 in PDAC carcinoma tissue was significantly lower than that in normal pancreatic tissue, and negative SMAD4 expression was closely related to tumour diameter, staging, lymph node metastasis and differentiation. Sanger sequencing analysis showed that the rate of SMAD4 mutation was 11.8% in 85 PDAC cases, and the novel SMAD4 Y353C missense mutation identified in this study promoted cell migration and invasion without affecting cell proliferation in vitro. Furthermore, SMAD4 Y353C resulted in reduced expression of E-cadherin and increased expression of Vimentin compared with wild-type SMAD4 overexpression.

Conclusion

This study supports the key role of SMAD4 as a tumour suppressor gene in PDAC and shows that SMAD4 Y353C is associated with poor progression of PDAC.

Pancreatic cancer in young adults: changes, challenges, and solutions

Despite improvements in multidisciplinary treatments, survival of pancreatic cancer (PC) patients remains dismal. Studies dealing with early onset pancreatic cancer (EOPC) patients are scarce. In this review, we discuss differences between EOPC and late-onset pancreatic cancer based on findings in original papers and reviews with a focus on morphology, genetics, clinical outcomes and therapy. In conclusion, families with a positive history of PC and patients with BRCA 1 or 2 mutations should be monitored. Patients with EOPC usually present with better overall fitness compared to the average PC population, however often with even more aggressive cancer behaviour. Therefore, potent state-of-the-art multi-modal systemic therapies should be applied whenever possible. Large-scale registries and randomized clinical trials dealing with EOPC in regard to distinct biology and outcome are warranted.

LAMB3 mediates apoptotic, proliferative, invasive, and metastatic behaviors in pancreatic cancer by regulating the PI3K/Akt signaling pathway

The poor prognosis of patients with pancreatic ductal adenocarcinoma (PDAC) is partially attributed to the invasive and metastatic behavior of this disease. Laminin subunit beta-3 (LAMB3) encodes one of the three subunits of LM-332, an extracellular matrix protein secreted by cultured human keratinocytes. In addition, LAMB3 is involved in the invasive and metastatic abilities of some types of cancer, including colon, pancreas, lung, cervix, stomach, and prostate cancer, but the role and mechanism of LAMB3 in PDAC have not been previously determined. Herein, we tentatively investigated the role of LAMB3 in the malignant biological behavior of PDAC. In this study, we demonstrated that LAMB3 is upregulated in PDAC. Inhibition of LAMB3 abrogated the tumorigenic outcomes of PI3K/Akt signaling pathway activation, including those involving cell cycle arrest, cell apoptosis, proliferation, invasion and migration in vitro, and tumor growth and liver metastasis in vivo. Our results showed that LAMB3 could mediate cell cycle arrest and apoptosis in PDAC cells and alter the proliferative, invasive, and metastatic behaviors of PDAC by regulating the PI3K/Akt signaling pathway. LAMB3 may be a novel therapeutic target for the treatment of PDAC in the future.

Enhancement of gemcitabine cytotoxicity in pancreatic adenocarcinoma through controlled release of nitric oxide

Gemcitabine (GEM) is the first-line treatment for pancreatic adenocarcinoma (PAC) yet chemoresistance is common. Nitric oxide (NO) is the predominant species responsible for the cytotoxic action of macrophages against cancer cells yet localized delivery is difficult given the short half-life. We sought to study the effect of locally delivered NO on GEM mediated PAC cytotoxicity and the potential role of SMAD4 in this effect. We hypothesized that NO would enhance the cytotoxicity of GEM in a SMAD4 dependent manner. NO-Silica nanoparticles (NO-Si) were synthesized via a co-condensation of tetraethoxysilane with aminoalkoxysilane under high-pressure nitrous oxide. NO release was measured using chemiluminescence. A SMAD4 negative PAC cell line (SMAD4-) was made using retroviral knockdown of Panc1 PAC cells. Panc1 and SMAD4- cells were treated with gemcitabine (100 nm (hi) to 30 μm (lo)), 30 mg NOSi particles, or both (NOSi^hi or NOSi^lo) and cell viability assessed. NoSi reduced cell viability by 25.99% in Panc1 and 24.38% in SMAD4-. When combined with gemcitabine, further reductions were seen in a dose dependent manner for both cell lines. We have demonstrated the in-vitro dose dependent cytotoxic effects of NOSi. When combined with GEM there is a synergistic effect resulting in improved cytotoxicity seen in both Panc1 and SMAD4- PAC cells with a differential pattern of cell death seen at high concentrations of NO. These findings suggest not only that NO is useful chemosensitizing agent but that SMAD4- may play a role in its synergism with GEM.

miRNA expression profiles in Smad4-positive and Smad4-negative SW620 human colon cancer cells detected by next-generation small RNA sequencing

Background and aims

SMAD4, as a tumor suppressive gene in human colon cancer, inhibits the metastasis of colon adenocarcinoma cells. However, the molecular mechanisms are unclear. miRNAs play an important role in the pathogenesis and progression of cancer.

Methods

In this study, a deep sequencing technique was used to screen Smad4-regulated miR-NAs in human colon cancer SW620 cell line. Using a next-generation small RNA sequencing approach, we compared the miRNA expression profiles of SW620 colon cancer cells transfected with smad4 lentiviral vector with those transfected with control vector. Six samples were selected and sequenced randomly each from control group (smad4-negative cell) and Smad4 group (Smad4-positive cells). Quantitative reverse transcription-PCR (qRT-PCR) and Western blot (WB) was used to validate the results of sequencing.

Results

Smad4 reexpression significantly upregulated 43 known miRNAs and downregulated 10 known miRNAs expression. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analysis of predicted miRNAs targets showed that these genes were mainly involved in protein-binding transcription factor activity, vascular smooth muscle contraction, pathways in cancer metastasis, and phosphatidylinositol 3-kinase-Akt signal pathway. qRT-PCR and WB validated the partial results of sequencing. Reexpression of Smad4 inhibited colon cancer cell migration and invasion. Smad4 reexpression increased the expression of E-cadherin (E-cad) and decreased the Vimentin (Vim) and Matrix Metalloproteinase-9 expression. Restoration of SMAD4 results in a marked decrease of Vim by inhibiting p-AKT and p-EPHA2, but significantly increased the E-cad by AKT-EPHA2 pathways.

Conclusion

Smad4 inhibits the migration and invasion ability of colon cancer cells in vitro and this is the first report of Smad4-mediated miRNA expression profiling in Smad4-positive and Smad4-negative SW620 human colon cancer cells, which may help us better understand the role of Smad4 in inhibiting the metastasis of colon cancer cells and its possible molecular mechanisms.

Ethyl acetate extract from Inula helenium L. inhibits the proliferation of pancreatic cancer cells by regulating the STAT3/AKT pathway

Sesquiterpene lactones are bioactive compounds that have been identified as responsible for the anticancer activity of the medicinal herb, Inula helenium L. (IHL). However, the mechanisms of action involved in the anti‑pancreatic cancer activity of IHL have yet to be elucidated. The present study used an optimized extraction strategy to obtain sesquiterpene lactones from IHL (the resulting product termed ethyl acetate extract of IHL; EEIHL), and examined the potential mechanisms involved in the anti‑pancreatic cancer activity of EEIHL. Ethanol and ethyl acetate were used to extract sesquiterpene lactones from IHL to give the final product EEIHL. Cell Counting Kit‑8, colony formation and Annexin V/propidium iodide assays were used to detect the anti‑proliferative activity of EEIHL. Cell migration was determined with a wound healing assay. mRNA and protein expression levels were analyzed by reverse transcription‑quantitative polymerase chain reaction and western blot analyses, respectively. It was identified that low concentrations of EEIHL caused CFPAC‑1 cell cycle arrest in the G0/G1 phase, whereas high concentrations of EEIHL induced mitochondria‑dependent apoptosis. In addition, EEIHL could inhibit the phosphorylation of the signal transducer and activator of transcription (STAT)3/AKT pathway, potentially resulting in impeded cell mobility. In conclusion, EEIHL could activate mitochondrial‑dependent apoptosis and inhibit cell migration through the STAT3/AKT pathway in CFPAC-1 cells.

Pancreatic Cancer: Molecular Characterization, Clonal Evolution and Cancer Stem Cells. Biomedicines. 2017;5. [PMID: 29156578 PMCID: PMC5744089 DOI: 10.3390/biomedicines5040065]

Pancreatic Ductal Adenocarcinoma (PDAC) is the fourth most common cause of cancer-related death and is the most lethal of common malignancies with a five-year survival rate of <10%. PDAC arises from different types of non-invasive precursor lesions: intraductal papillary mucinous neoplasms, mucinous cystic neoplasms and pancreatic intraepithelial neoplasia. The genetic landscape of PDAC is characterized by the presence of four frequently-mutated genes: KRAS, CDKN2A, TP53 and SMAD4. The development of mouse models of PDAC has greatly contributed to the understanding of the molecular and cellular mechanisms through which driver genes contribute to pancreatic cancer development. Particularly, oncogenic KRAS-driven genetically-engineered mouse models that phenotypically and genetically recapitulate human pancreatic cancer have clarified the mechanisms through which various mutated genes act in neoplasia induction and progression and have led to identifying the possible cellular origin of these neoplasias. Patient-derived xenografts are increasingly used for preclinical studies and for the development of personalized medicine strategies. The studies of the purification and characterization of pancreatic cancer stem cells have suggested that a minority cell population is responsible for initiation and maintenance of pancreatic adenocarcinomas. The study of these cells could contribute to the identification and clinical development of more efficacious drug treatments.

The Role of Platelet-Derived ADP and ATP in Promoting Pancreatic Cancer Cell Survival and Gemcitabine Resistance

Platelets have been demonstrated to be vital in cancer epithelial-mesenchymal transition (EMT), an important step in metastasis. Markers of EMT are associated with chemotherapy resistance. However, the association between the development of chemoresistance, EMT, and the contribution of platelets to the process, is still unclear. Here we report that platelets regulate the expression of (1) human equilibrative nucleoside transporter 1 (hENT1) and (2) cytidine deaminase (CDD), markers of gemcitabine resistance in pancreatic cancer. Human ENT1 (hENT1) is known to enable cellular uptake of gemcitabine while CDD deactivates gemcitabine. Knockdown experiments demonstrate that Slug, a mesenchymal transcriptional factor known to be upregulated during EMT, regulates the expression of hENT1 and CDD. Furthermore, we demonstrate that platelet-derived ADP and ATP regulate Slug and CDD expression in pancreatic cancer cells. Finally, we demonstrate that pancreatic cancer cells express the purinergic receptor P2Y₁₂, an ADP receptor found mainly on platelets. Thus ticagrelor, a P2Y₁₂ inhibitor, was used to examine the potential therapeutic effect of an ADP receptor antagonist on cancer cells. Our data indicate that ticagrelor negated the survival signals initiated in cancer cells by platelet-derived ADP and ATP. In conclusion, our results demonstrate a novel role of platelets in modulating chemoresistance in pancreatic cancer. Moreover, we propose ADP/ATP receptors as additional potential drug targets for treatment of pancreatic cancer.

miR-509-5p and miR-1243 increase the sensitivity to gemcitabine by inhibiting epithelial-mesenchymal transition in pancreatic cancer. Sci Rep. 2017;7:4002. [PMID: 28638102 PMCID: PMC5479822 DOI: 10.1038/s41598-017-04191-w]

The epithelial-mesenchymal transition (EMT) contributes to various processes in cancer progression, such as metastasis and drug resistance. Since we have already established a cell-based reporter system for identifying EMT-suppressive microRNAs (miRNAs) in the pancreatic cancer cell line Panc1, we performed a function-based screening assay by combining this reporter system and a miRNA library composed of 1,090 miRNAs. As a result, we identified miR-509-5p and miR-1243 as EMT-suppressive miRNAs, although the mechanisms for EMT-suppression induced by these miRNAs have yet to be clarified. Herein, we demonstrated that overexpression of miR-509-5p and miR-1243 increased the expression of E-cadherin through the suppression of EMT-related gene expression and that drug sensitivity increased with a combination of each of these miRNAs and gemcitabine. Moreover, miR-509-5p was associated with worse overall survival in patients with pancreatic cancer and was identified as an independently selected predictor of mortality. Our findings suggest that miR-509-5p and miR-1243 might be novel chemotherapeutic targets and serve as biomarkers in pancreatic cancer.

Inflammation and Epithelial-Mesenchymal Transition in Pancreatic Ductal Adenocarcinoma: Fighting Against Multiple Opponents

Pancreatic ductal adenocarcinoma (PDAC) is the most common type of pancreatic cancer and one of the most lethal human cancers. Inflammation is a critical component in PDAC initiation and progression. Inflammation also contributes to the aggressiveness of PDAC indirectly via induction of epithelial-mesenchymal transition (EMT), altogether leading to enhanced resistance to chemotherapy and poor survival rates. This review gives an overview of the key pro-inflammatory signaling pathways involved in PDAC pathogenesis and discusses the role of inflammation in induction of EMT and development of chemoresistance in patients with PDAC.

Molecular Drivers of Pancreatic Cancer Pathogenesis: Looking Inward to Move Forward

Pancreatic cancer (PC) continues to rank among the most lethal cancers. The consistent increase in incidence and mortality has made it the seventh leading cause of cancer-associated deaths globally and the third in the United States. The biggest challenge in combating PC is our insufficient understanding of the molecular mechanism(s) underlying its complex biology. Studies during the last several years have helped identify several putative factors and events, both genetic and epigenetic, as well as some deregulated signaling pathways, with implications in PC onset and progression. In this review article, we make an effort to summarize our current understanding of molecular and cellular events involved in the pathogenesis of pancreatic malignancy. Specifically, we provide up-to-date information on the genetic and epigenetic changes that occur during the initiation and progression of PC and their functional involvement in the pathogenic processes. We also discuss the impact of the tumor microenvironment on the molecular landscape of PC and its role in aggressive disease progression. It is envisioned that a better understanding of these molecular factors and the mechanisms of their actions can help unravel novel diagnostic and prognostic biomarkers and can also be exploited for future targeted therapies.

Loss of KLF4 and consequential downregulation of Smad7 exacerbate oncogenic TGF-β signaling in and promote progression of hepatocellular carcinoma

Hyperactivation of TGF-β signaling pathway is a common feature of hepatocellular carcinoma (HCC) progression. However, the driver factors leading to enhanced TGF-β activity are not well characterized. Here, we explore the mechanisms that loss of Krüppel-like factor 4 (KLF4) exacerbates oncogenic TGF-β signaling in human HCC. The expression of KLF4 and TGF-β signaling components in primary HCC and their clinicopathologic relevance and significance was evaluated by using tissue microarray and immunohistochemistry. Cellular and molecular impacts of altered KLF4 expression and TGF-β signaling were determined using immunofluorescence, Western blot, reverse-transcriptase polymerase chain reaction, chromatin immunoprecipitation, and promoter reporter assays. Loss of KLF4 expression in primary HCC closely correlated with decreased Smad7 expression, increased p-Smad2/3 expression, and independently predicts reduced overall and relapse-free survival after surgery. TGF-β signaling components were expressed in most HCC cells, and activation of TGF-β signaling promoted cell migration and invasion. Enforced KLF4 expression blocked TGF-β signal transduction and inhibited cell migration and invasion via activation of Smad7 transcription, whereas deletion of its C-terminal zinc-finger domain diminished this effect. KLF4 protein physically interacts with the Smad7 promoter. Promoter deletion and point mutation analyses revealed that a region between nucleotides −15 bp and −9 bp of the Smad7 promoter was required for the induction of Smad7 promoter activity by KLF4. Our data indicate that KLF4 suppresses oncogenic TGF-β signaling by activation of Smad7 transcription, and that loss of KLF4 expression in primary HCC may contribute to activation of oncogenic TGF-β signaling and subsequent tumor progression.

Epithelial-mesenchymal transition as a therapeutic target for overcoming chemoresistance in pancreatic cancer

Pancreatic cancer has one of the worst prognoses among all cancers due to the late manifestation of identifiable symptoms and high resistance to chemo- and radiation therapies. In recent years, a cancer development phase termed epithelial-mesenchymal transition (EMT) has gained increasing research focus. The process is implicated in tumour metastasis, and emerging evidence suggests EMT also contributes or induces chemoresistance in several cancers. Nevertheless, the applicability of therapeutic targeting of EMT faces many challenges. In this mini-review, we summarise the evidence supporting the role of EMT in pancreatic cancer progression, focusing particularly on its association with chemoresistance.

Stiffness of pancreatic cancer cells is associated with increased invasive potential

Metastasis is a fundamentally physical process in which cells are required to deform through narrow gaps as they invade surrounding tissues and transit to distant sites. In many cancers, more invasive cells are more deformable than less invasive cells, but the extent to which mechanical phenotype, or mechanotype, can predict disease aggressiveness in pancreatic ductal adenocarcinoma (PDAC) remains unclear. Here we investigate the invasive potential and mechanical properties of immortalized PDAC cell lines derived from primary tumors and a secondary metastatic site, as well as noncancerous pancreatic ductal cells. To investigate how invasive behavior is associated with cell mechanotype, we flow cells through micron-scale pores using parallel microfiltration and microfluidic deformability cytometry; these results show that the ability of PDAC cells to passively transit through pores is only weakly correlated with their invasive potential. We also measure the Young's modulus of pancreatic ductal cells using atomic force microscopy, which reveals that there is a strong association between cell stiffness and invasive potential in PDAC cells. To determine the molecular origins of the variability in mechanotype across our PDAC cell lines, we analyze RNAseq data for genes that are known to regulate cell mechanotype. Our results show that vimentin, actin, and lamin A are among the most differentially expressed mechanoregulating genes across our panel of PDAC cell lines, as well as a cohort of 38 additional PDAC cell lines. We confirm levels of these proteins across our cell panel using immunoblotting, and find that levels of lamin A increase with both invasive potential and Young's modulus. Taken together, we find that stiffer PDAC cells are more invasive than more compliant cells, which challenges the paradigm that decreased cell stiffness is a hallmark of metastatic potential.

Smad4 inhibits cell migration via suppression of JNK activity in human pancreatic carcinoma PANC-1 cells

Smad4 is a common Smad and is a key downstream regulator of the transforming growth factor-β signaling pathway, in which Smad4 often acts as a potent tumor suppressor and functions in a highly context-dependent manner, particularly in pancreatic cancer. However, little is known regarding whether Smad4 regulates other signaling pathways involved in pancreatic cancer. The present study demonstrated that Smad4 downregulates c-Jun N-terminal kinase (JNK) activity using a Smad4 loss-of-function or gain-of-function analysis. Additionally, stable overexpression of Smad4 clearly affected the migration of human pancreatic epithelioid carcinoma PANC-1 cells, but did not affect cell growth. In addition, the present study revealed that upregulation of mitogen-activated protein kinase phosphatase-1 is required for the reduction of JNK activity by Smad4, leading to a decrease in vascular endothelial growth factor expression and inhibiting cell migration. Overall, the present findings indicate that Smad4 may suppress JNK activation and inhibit the tumor characteristics of pancreatic cancer cells.

Large-Scale Profiling of Kinase Dependencies in Cancer Cell Lines

One approach to identifying cancer-specific vulnerabilities and therapeutic targets is to profile genetic dependencies in cancer cell lines. Here, we describe data from a series of siRNA screens that identify the kinase genetic dependencies in 117 cancer cell lines from ten cancer types. By integrating the siRNA screen data with molecular profiling data, including exome sequencing data, we show how vulnerabilities/genetic dependencies that are associated with mutations in specific cancer driver genes can be identified. By integrating additional data sets into this analysis, including protein-protein interaction data, we also demonstrate that the genetic dependencies associated with many cancer driver genes form dense connections on functional interaction networks. We demonstrate the utility of this resource by using it to predict the drug sensitivity of genetically or histologically defined subsets of tumor cell lines, including an increased sensitivity of osteosarcoma cell lines to FGFR inhibitors and SMAD4 mutant tumor cells to mitotic inhibitors.

Inactivation of TGFβ receptor II signalling in pancreatic epithelial cells promotes acinar cell proliferation, acinar-to-ductal metaplasia and fibrosis during pancreatitis

Determining signalling pathways that regulate pancreatic regeneration following pancreatitis is critical for implementing therapeutic interventions. In this study we elucidated the molecular mechanisms underlying the effects of transforming growth factor-β (TGFβ) in pancreatic epithelial cells during tissue regeneration. To this end, we conditionally inactivated TGFβ receptor II (TGFβ-RII) using a Cre-LoxP system under the control of pancreas transcription factor 1a (PTF1a) promoter, specific for the pancreatic epithelium, and evaluated the molecular and cellular changes in a mouse model of cerulein-induced pancreatitis. We show that TGFβ-RII signalling does not mediate the initial acinar cell damage observed at the onset of pancreatitis. However, TGFβ-RII signalling not only restricts acinar cell replication during the regenerative phase of the disease but also limits ADM formation in vivo and in vitro in a cell-autonomous manner. Analyses of molecular mechanisms underlying the observed phenotype revealed that TGFβ-RII signalling stimulates the expression of cyclin-dependent kinase inhibitors and intersects with the EGFR signalling axis. Finally, TGFβ-RII ablation in epithelial cells resulted in increased infiltration of inflammatory cells in the early phases of pancreatitis and increased activation of pancreatic stellate cells in the later stages of pancreatitis, thus highlighting a TGFβ-based crosstalk between epithelial and stromal cells regulating the development of pancreatic inflammation and fibrosis. Collectively, our data not only contribute to clarifying the cellular processes governing pancreatic tissue regeneration, but also emphasize the conserved role of TGFβ as a tumour suppressor, both in the regenerative process following pancreatitis and in the initial phases of pancreatic cancer.

Construction and analysis of three networks of genes and microRNAs in adenocarcinoma

Adenocarcinoma is one of the most serious diseases that threaten human health. Numerous studies have investigated adenocarcinoma and have obtained a considerable amount of data regarding genes and microRNA (miRNA) in adenocarcinoma. However, studies have only focused on one or a small number of genes and miRNAs, and the data is stored in a scattered form, making it challenging to summarize and assess the associations between the genes and miRNAs. In the present study, three networks of genes and miRNAs in adenocarcinoma were focused on. This enabled the construction of networks of elements involved in adenocarcinoma and the analysis of these networks, rather than only discussing one gene. Transcription factors (TFs), miRNAs, and target and host genes of miRNAs in adenocarcinoma, and the regulatory associations between these elements were identified in the present study. These elements and associations were then used to construct three networks, which consisted of the differentially-expressed, associated and global networks. The similarities and differences between the three networks were compared and analyzed. In total, 3 notable TFs, consisting of TP53, phosphatase and tensin homolog and SMAD4, were identified in adenocarcinoma. These TFs were able to regulate the differentially-expressed genes and the majority of the differentially-expressed miRNAs. Certain important regulatory associations were also found in adenocarcinoma, in addition to self-regulating associations between TFs and miRNAs. The upstream and downstream elements of the differentially-expressed genes and miRNAs were recorded, which revealed the regulatory associations between genes and miRNAs. The present study clearly revealed components of the pathogenesis of adenocarcinoma and the regulatory associations between the elements in adenocarcinoma. The present study may aid the investigation of gene therapy in adenocarcinoma and provides a theoretical basis for studies of gene therapy methods as a treatment for adenocarcinoma.

Pancreatic cancer stem cells: Advances and perspectives

The evolution of certain types of malignancies including pancreatic carcinoma, as verified in mountains of literature published since the 1970s, is due in great measure to cancer stem cells located within the hierarchically organized tumor structure. However, by now, the results of numerous attempts to relate cancer stem cell theory to malignant biological behavior of cancers have appeared rather discouraging in terms of explaining and overcoming tumor heterogeneity in both in vitro and in vivo conditions. In seeking to describe the cancer stem cells in pancreatic adenocarcinoma, in the current editorial, we rely primarily on the existing evidence to gain a comprehensive perspective toward this area.

Smad4 loss synergizes with TGFα overexpression in promoting pancreatic metaplasia, PanIN development, and fibrosis

AIMS

While overexpression of TGFα has been reported in human pancreatic ductal adenocarcinoma (PDAC), mice with overexpressed TGFα develop premalignant pancreatic acinar-to-ductal metaplasia (ADM) but not PDAC. TGF-β signaling pathway is pivotal to the development of PDAC and tissue fibrosis. Here we sought to investigate the interplay between TGFα and TGF-β signaling in pancreatic tumorigenesis and fibrosis, namely via Smad4 inactivation.

METHODS

The MT-TGFα mouse was crossed with a new Smad4 conditional knock-out mouse (Smad4flox/flox;p48-Cre or S4) to generate Smad4flox/flox;MT-TGFα;p48-Cre (STP). After TGFα overexpression was induced with zinc sulfate water for eight months, the pancreata of the STP, MT-TGFα, and S4 mice were examined for tumor development and fibrotic responses. PanIN lesions and number of ducts were counted, and proliferation was measured by Ki67 immunohistochemistry (IHC). Qualitative analysis of fibrosis was analyzed by Trichrome Masson and Sirius Red staining, while vimentin was used for quantification. Expression analyses of fibrosis, pancreatitis, or desmoplasia associated markers (α-SMA, Shh, COX-2, Muc6, Col1a1, and Ctgf) were performed by IHC and/or qRT-PCR.

RESULTS

Our STP mice exhibited advanced ADM, increased fibrosis, increased numbers of PanIN lesions, overexpression of chronic pancreatitis-related marker Muc6, and elevated expression of desmoplasia-associated marker Col1A1, compared to the MT-TGFα mice. The inactivation of Smad4 in the exocrine compartment was responsible for both the enhanced PanIN formation and fibrosis in the pancreas. The phenotype of the STP mice represents a transient state from ADMs to PanINs, closely mimicking the interface area seen in human chronic pancreatitis associated with PDAC.

CONCLUSION

We have documented a novel mouse model, the STP mice, which displayed histologic presentations reminiscent to those of human chronic pancreatitis with signs of early tumorigenesis. The STP mice could be a suitable animal model for interrogating the transition of chronic pancreatitis to pancreatic cancer.

Pancreatic cancer stem cells

Studies are emerging in support of the cancer stem cells (CSCs) theory which considers that a tiny subset of cancer cells is exclusively responsible for the initiation and malignant behavior of a cancer. This cell population, also termed CSCs, possesses the capacity both to self-renew, producing progeny that have the identical tumorigenic potential, and to differentiate into the bulk of cancer cells, helping serve the formation of the tumor entities, which, altogether, build the hierarchically organized structure of a cancer. In this review, we try to articulate the complicated signaling pathways regulating the retention of the characteristics of pancreatic CSCs, and in the wake of which, we seek to offer insights into the CSCs-relevant targeted therapeutics which are, in the meantime, confronted with bigger challenges than ever.