Inhibiting signal transducer and activator of transcription-3 increases response to gemcitabine and delays progression of pancreatic cancer

The oncogenic mechanisms of the Janus kinase-signal transducer and activator of transcription pathway in digestive tract tumors

Digestive tract tumors are heterogeneous and involve the dysregulation of multiple signaling pathways. The Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathway plays a notable role in the oncogenesis of digestive tract tumors. Typically activated by pro-inflammatory cytokines, it regulates important biological processes, such as cell growth, differentiation, apoptosis, immune responses, and inflammation. The aberrant activation of this pathway manifests in different forms, including mutations in JAKs, overexpression of cytokine receptors, and sustained STAT activation, and contributes to promoting the malignant characteristics of cancer cells, including uncontrolled proliferation, resistance to apoptosis, enhanced invasion and metastasis, angiogenesis, acquisition of stem-like properties, and drug resistance. Numerous studies have shown that aberrant activation of the JAK-STAT pathway is closely related to the development and progression of digestive tract tumors, contributing to tumor survival, angiogenesis, changes in the tumor microenvironment, and even immune escape processes. In addition, this signaling pathway also affects the sensitivity of digestive tract tumors to chemotherapy and targeted therapy. Therefore, it is crucial to comprehensively understand the oncogenic mechanisms underlying the JAK-STAT pathway in order to develop effective therapeutic strategies against digestive tract tumors. Currently, several JAK-STAT inhibitors are undergoing clinical and preclinical trials as potential treatments for various human diseases. However, further investigation is required to determine the role of this pathway, as well as the effectiveness and safety of its inhibitors, especially in the context of digestive tract tumors. In this review, we provide an overview of the structure, classic activation, and negative regulation of the JAK-STAT pathway. Furthermore, we discuss the pathogenic mechanisms of JAK-STAT signaling in different digestive tract tumors, with the aim of identifying potential novel therapeutic targets. Video Abstract.

Recent advances in targeted therapy for pancreatic adenocarcinoma

Pancreatic adenocarcinoma (PDAC) is a fatal disease with a 5-year survival rate of 8% and a median survival of 6 mo. In PDAC, several mutations in the genes are involved, with Kirsten rat sarcoma oncogene (90%), cyclin-dependent kinase inhibitor 2A (90%), and tumor suppressor 53 (75%–90%) being the most common. Mothers against decapentaplegic homolog 4 represents 50%. In addition, the self-preserving cancer stem cells, dense tumor microenvironment (fibrous accounting for 90% of the tumor volume), and suppressive and relatively depleted immune niche of PDAC are also constitutive and relevant elements of PDAC. Molecular targeted therapy is widely utilized and effective in several solid tumors. In PDAC, targeted therapy has been extensively evaluated; however, survival improvement of this aggressive disease using a targeted strategy has been minimal. There is currently only one United States Food and Drug Administration-approved targeted therapy for PDAC – erlotinib, but the absolute benefit of erlotinib in combination with gemcitabine is also minimal (2 wk). In this review, we summarize current targeted therapies and clinical trials targeting dysregulated signaling pathways and components of the PDAC oncogenic process, analyze possible reasons for the lack of positive results in clinical trials, and suggest ways to improve them. We also discuss emerging trends in targeted therapies for PDAC: combining targeted inhibitors of multiple pathways. The PubMed database and National Center for Biotechnology Information clinical trial website (www.clinicaltrials.gov) were queried to identify completed and published (PubMed) and ongoing (clinicaltrials.gov) clinical trials (from 2003-2022) using the keywords pancreatic cancer and targeted therapy. The PubMed database was also queried to search for information about the pathogenesis and molecular pathways of pancreatic cancer using the keywords pancreatic cancer and molecular pathways.

Overcoming Acquired Drug Resistance to Cancer Therapies through Targeted STAT3 Inhibition

Anti-neoplastic agents for cancer treatment utilize many different mechanisms of action and, when combined, can result in potent inhibition of cancer growth. Combination therapies can result in long-term, durable remission or even cure; however, too many times, these anti-neoplastic agents lose their efficacy due to the development of acquired drug resistance (ADR). In this review, we evaluate the scientific and medical literature that elucidate STAT3-mediated mechanisms of resistance to cancer therapeutics. Herein, we have found that at least 24 different anti-neoplastic agents-standard toxic chemotherapeutic agents, targeted kinase inhibitors, anti-hormonal agents, and monoclonal antibodies-that utilize the STAT3 signaling pathway as one mechanism of developing therapeutic resistance. Targeting STAT3, in combination with existing anti-neoplastic agents, may prove to be a successful therapeutic strategy to either prevent or even overcome ADR to standard and novel cancer therapies.

Penetrating Micelle for Reversing Immunosuppression and Drug Resistance in Pancreatic Cancer Treatment

Pancreatic ductal adenocarcinoma (PDAC) is on of the most lethal malignant tumors with relatively poor prognosis, characterized with insufficient drug penetration, low immune response and obvious drug resistances. The therapeutic inefficiency is multifactorially related to its specific tumor microenvironment (TME), which is representatively featured as rich stroma and immunosuppression. In this work, a versatile drug delivery system is developed that can coencapsulate two prodrugs modified from gemcitabine (GEM) and a signal transducer and activator of transcription 3 (STAT3) inhibitor (HJC0152), and the gradient pH variation is further sensed in the TME of PDAC to achieve a higher penetration by reversing its surficial charges. The escorted prodrugs can release GEM intracellularly, and respond to the hypoxic condition to yield the parental STAT3 inhibitor HJC0152, respectively. By inhibiting STAT3, the tumor immunosuppression microenvironment can be re-educated through the reversion of M2-like tumor associated macrophages (M2-TAMs), recruitment of cytotoxic T lymphocytes and downregulation of regulatory T cells (Treg s). Furthermore, cytidine deaminase (CDA) and α-smooth muscle actin (α-SMA) expression can be downregulated, plus the lipid modification of GEM, the drug resistance of GEM can be greatly relieved. Based on the above design, a synergetic therapeutic efficacy in PDAC treatment can be achieved to provide more opportunity for clinical applications.

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.

5-epi-Sinuleptolide from Soft Corals of the Genus Sinularia Exerts Cytotoxic Effects on Pancreatic Cancer Cell Lines via the Inhibition of JAK2/STAT3, AKT, and ERK Activity

Pancreatic ductal adenocarcinoma is one of the most lethal malignancies: more than half of patients are diagnosed with a metastatic disease, which is associated with a five-year survival rate of only 3%. 5-epi-Sinuleptolide, a norditerpene isolated from Sinularia sp., has been demonstrated to possess cytotoxic activity against cancer cells. However, the cytotoxicity against pancreatic cancer cells and the related mechanisms are unknown. The aim of this study was to evaluate the anti-pancreatic cancer potential of 5-epi-sinuleptolide and to elucidate the underlying mechanisms. The inhibitory effects of 5-epi-sinuleptolide treatment on the proliferation of pancreatic cancer cells were determined and the results showed that 5-epi-sinuleptolide treatment inhibited cell proliferation, induced apoptosis and G2/M cell cycle arrest, and suppressed the invasion of pancreatic cancer cells. The results of western blotting further revealed that 5-epi-sinuleptolide could inhibit JAK2/STAT3, AKT, and ERK phosphorylation, which may account for the diverse cytotoxic effects of 5-epi-sinuleptolide. Taken together, our present investigation unveils a new therapeutic and anti-metastatic potential of 5-epi-sinuleptolide for pancreatic cancer treatment.

Gemcitabine synergizes with cisplatin to inhibit nasopharyngeal carcinoma cell proliferation and tumor growth

In a recently published phase III clinical trial, gemcitabine (GEM) plus cisplatin (DDP) induction chemotherapy significantly improved recurrence-free survival and overall survival and became the standard of care among patients with locoregionally advanced NPC. However, the molecular mechanisms of GEM synergized with DPP in NPC cells remain elucidated. These findings prompt us to explore the effect of the combination between GEM and DDP in NPC cell lines through proliferative phenotype, immunofluorescence, flow cytometry, and western blotting assays. In vitro studies reveal that GEM or DPP treated alone induces cell cycle arrest, promotes cell apoptosis, forces DNA damage response, and GEM synergism with DDP significantly increases the above effects in NPC cells. In vivo studies indicate that GEM or DPP treated alone significantly inhibits the tumor growth and prolongs the survival time of mice injected with SUNE1 cells compared to the control group. Moreover, the mice treated with GEM combined with DDP have smaller tumors and survive longer than those in GEM or DPP treated alone group. In addition, P-gp may be the key molecule that regulates the synergistic effect of gemcitabine and cisplatin. GEM synergizes with DPP to inhibit NPC cell proliferation and tumor growth by inducing cell cycle arrest, cell apoptosis, and DNA damage response, which reveals the mechanisms of combined GEM and DDP induction chemotherapy in improving locoregionally advanced NPC.

Immunity-Related Gene Signature Identifies Subtypes Benefitting From Adjuvant Chemotherapy or Potentially Responding to PD1/PD-L1 Blockage in Pancreatic Cancer

Tumor microenvironment comprises of a variety of cell types, which is quite complex and involved in chemotherapy and immune checkpoint blockage resistance. In order to explore the mechanisms involved in tumor immune microenvironment in pancreatic ductal adenocarcinoma (PDAC), we first constructed an immunity-related 18-gene signature using The Cancer Genome Atlas (TCGA) PDAC project data. Then we applied the 18-gene signature to divide PDAC patients into low score and high score groups. Patients in high score group showed inferior prognosis, which was validated in another four independent cohorts, including Ruijin cohort. High score group showed significant enrichment of pathways involved in cell division and cell cycle especially in G1/S phase transition. In high score group, IHC analysis revealed higher levels of the proliferative indexes of Ki67 and PCNA than that in low score group. Prognostic analysis confirmed that patients in high score group could benefit from the gemcitabine-based adjuvant chemotherapy. In low score group, the programmed cell death 1 ligand 1(PD-L1) (+) cases showed worse prognosis but higher T cell infiltration than PD-L1(−) cases. Our immunity-related 18-gene signature could effectively predict PDAC prognosis, and it might be a practical predictive tool to identify PDAC subtype benefitting from gemcitabine-based adjuvant chemotherapy or potentially responding to PD1/PD-L1 blockade therapy.

Overcoming the Tumor Microenvironmental Barriers of Pancreatic Ductal Adenocarcinomas for Achieving Better Treatment Outcomes

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive disease with the lowest survival rate among all solid tumors. The lethality of PDAC arises from late detection and propensity of the tumor to metastasize and develop resistance against chemo and radiation therapy. A highly complex tumor microenvironment composed of dense stroma, immune cells, fibroblast, and disorganized blood vessels, is the main obstacle to current PDAC therapy. Despite the tremendous success of immune checkpoint inhibitors (ICIs) in cancers, PDAC remains one of the poorest responders of ICIs therapy. The immunologically "cold" phenotype of PDAC is attributed to the low mutational burden, high infiltration of myeloid-derived suppressor cells and T-regs, contributing to a significant immunotherapy resistance mechanism. Thus, the development of innovative strategies for turning immunologically "cold" tumor into "hot" ones is an unmet need to improve the outcome of PDAC ICIs therapies. Other smart strategies, such as nanomedicines, sonic Hedgehog inhibitor, or smoothened inhibitor, are discussed to enhance chemotherapeutic agents' efficiency by disrupting the PDAC stroma. This review highlights the current challenges and various preclinical and clinical strategies to overcome current PDAC therapy difficulties, thus significantly advancing PDAC research knowledge.

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.

The natural product trienomycin A is a STAT3 pathway inhibitor that exhibits potent in vitro and in vivo efficacy against pancreatic cancer

BACKGROUND AND PURPOSE

Pancreatic cancer is an exceptionally fatal disease. However, therapeutic drugs for pancreatic cancer have presented a serious shortage over the past few decades. Signal transducer and activator of transcription-3 (STAT3) is persistently activated in many human cancers where it promotes tumour development and progression. Natural products serve as an inexhaustible source of anticancer drugs. Here, we identified the natural product trienomycin A (TA), an ansamycin antibiotic, as a potential inhibitor of the STAT3 pathway with potent activity against pancreatic cancer.

EXPERIMENTAL APPROACH

Effects of trienomycin A on transcriptional activity of STAT3 were assessed by the STAT3-luciferase (STAT3-luc) reporter system. In vitro and in vivo inhibitory activity of TA against pancreatic cancer made use of molecular docking, surface plasmon resonance (SPR) assay, MTS assay, colony formation assay, transwell migration/invasion assay, flow cytometric analysis, immunofluorescence staining, quantitative real-time polymerase chain reaction (PCR), western blotting, tumour xenograft model, haematoxylin and eosin (H&E) staining and immunohistochemistry.

KEY RESULTS

Trienomycin A directly bound to STAT3 and inhibited STAT3 (Tyr705) phosphorylation, thus inhibiting the STAT3 pathway. Trienomycin A also inhibited colony formation, proliferation, migration and invasion of pancreatic cancer cell lines. Trienomycin A also markedly blocked pancreatic tumour growth in vivo. More importantly, trienomycin A did not show obvious toxicity at the effective dose in mice.

CONCLUSIONS AND IMPLICATIONS

Trienomycin A exerted anti-neoplastic activity by suppressing STAT3 activation in pancreatic cancer. This natural product could be a novel therapeutic candidate for pancreatic cancer.

Phospho-valproic acid (MDC-1112) reduces pancreatic cancer growth in patient-derived tumor xenografts and KPC mice: enhanced efficacy when combined with gemcitabine

New chemotherapeutic agents are needed for pancreatic cancer (PC). We have previously shown that phospho-valproic acid (MDC-1112) is effective in cell-line xenografts of PC. Here, we explored whether MDC-1112 is effective in additional clinically relevant animal models of PC and whether MDC-1112 enhances the anticancer effect of clinically used chemotherapeutic agents. MDC-1112 alone strongly reduced patient-derived pancreatic tumor xenograft growth, and extended survival of LSL-KrasG12D/+; LSL-Trp53R172H/+; Pdx1-Cre (KPC) mice. In both models, MDC-1112 inhibited STAT3 activation and its downstream signals, including Bcl-xL and cyclin D1. In human PC cell lines, P-V enhanced the growth inhibitory effect of gemcitabine (GEM), Abraxane and 5-FU, but not that of irinotecan. Normal human pancreatic epithelial cells were more resistant to the cytotoxic effects of MDC-1112/GEM combination. Furthermore, MDC-1112 enhanced GEM's effect on colony formation, apoptosis, cell migration, and cell invasion. In vivo, MDC-1112 and GEM, given alone, reduced patient-derived pancreatic tumor xenograft growth by 58% and 87%, respectively; whereas MDC-1112/GEM combination reduced tumor growth by 94%, inducing tumor stasis. In conclusion, MDC-1112 should be further explored as a potential agent to be used in combination with GEM for treating PC.

Combined inhibition of Ref-1 and STAT3 leads to synergistic tumour inhibition in multiple cancers using 3D and in vivo tumour co-culture models

With a plethora of molecularly targeted agents under investigation in cancer, a clear need exists to understand which pathways can be targeted simultaneously with multiple agents to elicit a maximal killing effect on the tumour. Combination therapy provides the most promise in difficult to treat cancers such as pancreatic. Ref-1 is a multifunctional protein with a role in redox signalling that activates transcription factors such as NF-κB, AP-1, HIF-1α and STAT3. Formerly, we have demonstrated that dual targeting of Ref-1 (redox factor-1) and STAT3 is synergistic and decreases cell viability in pancreatic cancer cells. Data presented here extensively expands upon this work and provides further insights into the relationship of STAT3 and Ref-1 in multiple cancer types. Using targeted small molecule inhibitors, Ref-1 redox signalling was blocked along with STAT3 activation, and tumour growth evaluated in the presence and absence of the relevant tumour microenvironment. Our study utilized qPCR, cytotoxicity and in vivo analysis of tumour and cancer-associated fibroblasts (CAF) response to determine the synergy of Ref-1 and STAT3 inhibitors. Overall, pancreatic tumours grown in the presence of CAFs were sensitized to the combination of STAT3 and Ref-1 inhibition in vivo. In vitro bladder and pancreatic cancer demonstrated the most synergistic responses. By disabling both of these important pathways, this combination therapy has the capacity to hinder crosstalk between the tumour and its microenvironment, leading to improved tumour response.

Identification of Withaferin A as a Potential Candidate for Anti-Cancer Therapy in Non-Small Cell Lung Cancer

Low response rate and recurrence are common issues in lung cancer; thus, identifying a potential compound for these patients is essential. Utilizing an in silico screening method, we identified withaferin A (WA), a cell-permeable steroidal lactone initially extracted from Withania somnifera, as a potential anti-lung cancer and anti-lung cancer stem-like cell (CSC) agent. First, we demonstrated that WA exhibited potent cytotoxicity in several lung cancer cells, as evidenced by low IC₅₀ values. WA concurrently induced autophagy and apoptosis and the activation of reactive oxygen species (ROS), which plays an upstream role in mediating WA-elicited effects. The increase in p62 indicated that WA may modulate the autophagy flux followed by apoptosis. In vivo research also demonstrated the anti-tumor effect of WA treatment. We subsequently demonstrated that WA could inhibit the growth of lung CSCs, decrease side population cells, and inhibit lung cancer spheroid-forming capacity, at least through downregulation of mTOR/STAT3 signaling. Furthermore, the combination of WA and chemotherapeutic drugs, including cisplatin and pemetrexed, exerted synergistic effects on the inhibition of epidermal growth factor receptor (EGFR) wild-type lung cancer cell viability. In addition, WA can further enhance the cytotoxic effect of cisplatin in lung CSCs. Therefore, WA alone or in combination with standard chemotherapy is a potential treatment option for EGFR wild-type lung cancer and may decrease the occurrence of cisplatin resistance by inhibiting lung CSCs.

Ki67 and P53 in Relation to Disease Progression in Metastatic Pancreatic Cancer: a Single Institution Analysis

We investigated the expression patterns of Ki67 and p53 in metastatic pancreatic adenocarcinomas and analyzed their relationship with disease progression-free survival (PFS) and overall survival (OS) in the overall study population and in patients treated with a gemcitabine-containing chemotherapy versus FOLFIRINOX chemotherapy. Patients with histologically confirmed stage IV adenocarcinoma of the pancreas treated at AUBMC were included after obtaining institutional review board approval (IRB ID: IM.ST.05). The ROC was plotted to identify the threshold Ki-67, p53 and CA19-9 value for disease progression, the identified value was further used in Kaplan Meier curves to compare PFS for both groups (gemcitabine versus FOLFIRINOX). A value of p < 0.05 was considered significant in all analyses. On univariate analysis, patients who had a Ki-67 > 12.5% or a p53 > 15% had significantly shorter PFS (p = 0.034 and p = 0.016, respectively). This effect was restricted to Gemcitabine or gemcitabine-combination treated patients. A decrease in CA19-9 levels 6-8 weeks after chemotherapy of >58% had significantly longer PFS (p = 0.027). On multivariate analysis after controlling for grade, age and P53, Ki-67 remained significant, for every one unit increase in Ki-67 the progression risk increases by 1.017 times. Our study highlights the negative impact of high P53 expression and Ki67 proliferation index on PFS in patients with metastatic pancreatic cancer.

TGF-βRII Knock-down in Pancreatic Cancer Cells Promotes Tumor Growth and Gemcitabine Resistance. Importance of STAT3 Phosphorylation on S727

Pancreatic adenocarcinoma (PDAC) is one of the most deadly cancers in the Western world because of a lack of early diagnostic markers and efficient therapeutics. At the time of diagnosis, more than 80% of patients have metastasis or locally advanced cancer and are therefore not eligible for surgical resection. Pancreatic cancer cells also harbour a high resistance to chemotherapeutic drugs such as gemcitabine that is one of the main palliative treatments for PDAC. Proteins involved in TGF-β signaling pathway (SMAD4 or TGF-βRII) are frequently mutated in PDAC (50–80%). TGF-β signalling pathway plays antagonistic roles during carcinogenesis by initially inhibiting epithelial growth and later promoting the progression of advanced tumors and thus emerged as both tumor suppressor and oncogenic pathways. In order to decipher the role of TGF-β in pancreatic carcinogenesis and chemoresistance, we generated CAPAN-1 and CAPAN-2 cell lines knocked down for TGF-βRII (first actor of TGF-β signaling). The impact on biological properties of these TGF-βRII-KD cells was studied both in vitro and in vivo. We show that TGF-βRII silencing alters tumor growth and migration as well as resistance to gemcitabine. TGF-βRII silencing also leads to S727 STAT3 and S63 c-Jun phosphorylation, decrease of MRP3 and increase of MRP4 ABC transporter expression and induction of a partial EMT phenotype. These markers associated with TGF-β signaling pathways may thus appear as potent therapeutic tools to better treat/manage pancreatic cancer.

OSU-A9 inhibits pancreatic cancer cell lines by modulating p38-JAK-STAT3 signaling

Pancreatic cancer is an aggressive malignancy that is the fourth leading cause of death worldwide. Since there is a dire need for novel and effective therapies to improve the poor survival rates of advanced pancreatic cancer patients, we analyzed the antitumor effects of OSU-A9, an indole-3-carbinol derivative, on pancreatic cancer cell lines in vitro and in vivo. OSU-A9 exhibited a stronger antitumor effect than gemcitabine on two pancreatic cancer cell lines, including gemcitabine-resistant PANC-1 cells. OSU-A9 treatment induced apoptosis, the down-regulation of Akt phosphorylation, up-regulation of p38 phosphorylation and decreased phosphorylation of JAK and STAT3. Cell migration and invasiveness assays showed that OSU-A9 reduced cancer cell aggressiveness and inhibited BxPC-3 xenograft growth in nude mice. These results suggest that OSU-A9 modulates the p38-JAK-STAT3 signaling module, thereby inducing cytotoxicity in pancreatic cancer cells. Continued evaluation of OSU-A9 as a potential therapeutic agent for pancreatic cancer thus appears warrented.

Updates in pancreatic cancer: Modest gains and hopeful targets

Pancreatic cancer is the twelfth most common cancer in the United States, representing 3.2% of all new cancer cases. While composing a small percentage of cancer diagnoses, pancreatic cancer is amongst the most lethal carcinomas, with an overall 5-year survival of 8.2% and incidence rates almost equivocal to death rates. By the time of diagnosis, a majority of patients will present with advanced stage disease. For patients with resectable disease, the estimated overall survival (OS) remains low at 20% as most will develop metastatic disease within 5 years. The lethality of this cancer is attributed to several factors including delayed presentation, lack of effective screening, and complex tumor biology and genetics. Data also suggest that even upon early presentation, pancreatic cancer is a systemic disease with micrometastasis present in the early stages. Traditional cytotoxic therapies have not been clinically impactful in pancreatic cancer, especially in advanced stages, and very little headway has been made in the development of new targeted therapies. As such, this review will discuss current advances in standard of care treatments and novel drug targets being researched.

Gemcitabine enhances cell invasion via activating HAb18G/CD147-EGFR-pSTAT3 signaling

Pancreatic cancer, one of the most lethal cancers, has very poor 5-year survival partly due to gemcitabine resistance. Recently, it was reported that chemotherapeutic agents may act as stressors to induce adaptive responses and to promote chemoresistance in cancer cells. During long-term drug treatment, the minority of cancer cells survive and acquire an epithelial-mesenchymal transition phenotype with increased chemo-resistance and metastasis. However, the short-term response of most cancer cells remains unclear. This study aimed to investigate the short-term response of pancreatic cancer cells to gemcitabine stress and to explore the corresponding mechanism. Our results showed that gemcitabine treatment for 24 hours enhanced pancreatic cancer cell invasion. In gemcitabine-treated cells, HAb18G/CD147 was up-regulated; and HAb18G/CD147 down-regulation or inhibition attenuated gemcitabine-enhanced invasion. Mechanistically, HAb18G/CD147 promoted gemcitabine-enhanced invasion by activating the EGFR (epidermal growth factor receptor)-STAT3 (signal transducer and activator of transcription 3) signaling pathway. Inhibition of EGFR-STAT3 signaling counteracted gemcitabine-enhanced invasion, and which relied on HAb18G/CD147 levels. In pancreatic cancer tissues, EGFR was highly expressed and positively correlated with HAb18G/CD147. These data indicate that pancreatic cancer cells enhance cell invasion via activating HAb18G/CD147-EGFR-pSTAT3 signaling. Our findings suggest that inhibiting HAb18G/CD147 is a potential strategy for overcoming drug stress-associated resistance in pancreatic cancer.

Effect of arenobufagin on human pancreatic carcinoma cells

Pancreatic carcinoma (PC) is a deadly form of cancer with poor overall survival. Currently, chemotherapy such as gemcitabine and 5-fluorouracil (5-FU) are the most popular medications that can improve survival, but rapid drug-resistance makes the search for more effective drugs urgent. Upon looking for natural components to treat PC, it was found that arenobufagin, a cardiac glycosides-like compound, showed significant effects on the gemcitabine-resistant pancreatic carcinoma cell line Panc-1 and the gemcitabine-sensitive cell line ASPC-1 at nanomolar concentrations. The present study used MTT and clonogenic survival assays to examine survival and proliferation, and western blotting to assess changes in the associated mitogen activated protein kinase and phosphoinositide 3-kinase pathways and expression of apoptosis-related proteins. The current study also detected the cell cycle by flow cytometry. Arenobufagin inhibited cell survival and proliferation, decreased the phosphorylation of key downstream proteins of K-Ras, including protein kinase B and extracellular signal related kinase, induced cell cycle G2/M phase arrest and apoptosis, and downregulated the level of phosphorylated epidermal growth factor receptor. Notably, the present data also showed that arenobufagin can enhance the sensitivity of PC cells to gemcitabine and 5-FU. In conclusion, arenobufagin could enhance the effect of gemcitabine and 5-FU on PC cells by targeting multiple key proteins. Therefore, arenobufagin has potential as anadjuvant therapy for the treatment of PC.

Boehmenan, a Lignan From the Chinese Medicinal Plant Clematis armandii, Inhibits A431 Cell Growth via Blocking p70S6/S6 Kinase Pathway

Previously, we have shown that boehmenan, a natural product isolated from the dried stem of Caulis clematidis armandii, exhibits various biological activities. The current study investigated the effects of boehmenan on the growth of human epidermoid carcinoma A431 cells. Cell viability and 50% inhibiting concentration (IC₅₀) were assessed by CellTiter-Glo luminescent cell viability assay. Cell cycle arrest was measured by flow cytometry. Intracellular reactive oxygen species production and mitochondrial membrane potential (ΔΨ_m) collapse were analyzed by a fluorescence spectrophotometer. The activation of epidermal growth factor receptor signaling pathway was evaluated by Western blot. The results showed that boehmenan significantly inhibited the growth of A431 cells (IC₅₀ = 1.6 µM) in a concentration- and time-dependent manner. This compound also blocked cell cycle progression at G2/M phase and modulated mitochondrial apoptosis-related proteins, as evidenced by upregulating p21, cleaved caspase-3, and cleaved poly (ADP-ribose) polymerase protein levels and by downregulating Bcl-2, pro-caspase-9 levels. In addition, boehmenan also markedly induced intracellular reactive oxygen species production and ΔΨ_m depolarization in a concentration-dependent manner. Furthermore, boehmenan-attenuated epidermal growth factor mediated the phosphorylation of signal transducer and activator of transcription 3 (STAT3), p70 ribosomal protein S6 kinase (p70S6)/S6 in a concentration-dependent manner. Taken together, our results suggest that boehmenan-mediated antiproliferative property in A431 cells was mediated partially by modulation of mitochondrial function and inhibition of STAT3 and p70S6 signal pathways.

Gemcitabine reduces MDSCs, tregs and TGFβ-1 while restoring the teff/treg ratio in patients with pancreatic cancer

Background

Cancer immunotherapy can be potentiated by conditioning regimens such as cyclophosphamide, which reduces the level of regulatory T cells (tregs). However, myeloid suppressive cells are still remaining. Accordingly to previous reports, gemcitabine improves immune status of cancer patients. In this study, the role of gemcitabine was further explored to map its immunological target cells and molecules in patients with pancreatic cancer.

Methods

Patient blood was investigated by flow cytometry and cytokine arrays at different time points during gemcitabine treatment.

Results

The patients had elevated myeloid-derived suppressor cells (MDSCs), and Tregs at diagnosis. Myeloid cells were in general decreased by gemcitabine. The granulocytic MDSCs were significantly reduced while monocytic MDSCs were not affected. In vitro, monocytes responding to IL-6 by STAT3 phosphorylation were prevented to respond in gemcitabine medium. However, gemcitabine could not prevent STAT3 phosphorylation in IL-6-treated tumor cell lines. TGFβ-1 was significantly reduced after only one treatment and continued to decrease. At the same time, the effector T cell:Treg ratio was increased and the effector T cells had full proliferative capacity during the gemcitabine cycle. However, after a resting period, the level of suppressor cells and TGFβ-1 had been restored showing the importance of continuous conditioning.

Conclusions

Gemcitabine regulates the immune system in patients with pancreatic cancer including MDSCs, Tregs and molecules such as TGFβ-1 but does not hamper the ability of effector lymphocytes to expand to stimuli. Hence, it may be of high interest to use gemcitabine as a conditioning strategy together with immunotherapy.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-016-1037-z) contains supplementary material, which is available to authorized users.

Gemcitabine treatment promotes pancreatic cancer stemness through the Nox/ROS/NF-κB/STAT3 signaling cascade

Gemcitabine, the standard chemotherapy drug for advanced pancreatic cancer, has shown limited benefits because of profound chemoresistance. However, the mechanism involved remains unclear. Cancer stem cells exhibit great tumorigenicity and are closely correlated with drug resistance and tumor relapse. In this study, we demonstrated that certain doses of gemcitabine increased the ratios of CD24⁺ and CD133⁺ cells and the expression of stemness-associated genes such as Bmi1, Nanog, and Sox2. The enhancement of stemness after gemcitabine treatment was accompanied by increased cell migration, chemoresistance, and tumorigenesis. Moreover, we found that gemcitabine promoted the binding of phosphorylated STAT3 to the promoter of Bmi1, Nanog, and Sox2 genes. Furthermore, inhibition of STAT3 partially reversed gemcitabine-induced sphere formation, migration, chemoresistance, and tumor relapse. We also demonstrated that the activation of STAT3 and gemcitabine-enhanced stemness was NADPH oxidase (Nox)-generated, ROS-dependent, and NF-κB partially mediated the process. Together, our results suggest a pivotal role of pancreatic cancer stem cells in developing chemoresistance toward gemcitabine treatment through the Nox/ROS/NF-κB/STAT3 signaling pathway. These findings will provide new insight for identifying potential targets that can be used to sensitize pancreatic cancer cells to chemotherapy.

Downregulation of STAT3/NF-κB potentiates gemcitabine activity in pancreatic cancer cells

There is an unmet need to develop new agents or strategies against therapy resistant pancreatic cancer (PanCA). Recent studies from our laboratory showed that STAT3 negatively regulates NF-κB and that inhibition of this crosstalk using Nexrutine® (Nx) reduces transcriptional activity of COX-2. Inhibition of these molecular interactions impedes pancreatic cancer cell growth as well as reduces fibrosis in a preclinical animal model. Nx is an extract derived from the bark of Phellodendron amurense and has been utilized in traditional Chinese medicine as antidiarrheal, astringent, and anti-inflammatory agent for centuries. We hypothesized that "Nx-mediated inhibition of survival molecules like STAT3 and NF-κB in pancreatic cancer cells will improve the efficacy of the conventional chemotherapeutic agent, gemcitabine (GEM)." Therefore, we explored the utility of Nx, one of its active constituents berberine and its derivatives, to enhance the effects of GEM. Using multiple human pancreatic cancer cells we found that combination treatment with Nx and GEM resulted in significant alterations of proteins in the STAT3/NF-κB signaling axis culminating in growth inhibition in a synergistic manner. Furthermore, GEM resistant cells were more sensitive to Nx treatment than their parental GEM-sensitive cells. Interestingly, although berberine, the Nx active component used, and its derivatives were biologically active in GEM sensitive cells they did not potentiate GEM activity when used in combination. Taken together, these results suggest that the natural extract, Nx, but not its active component, berberine, has the potential to improve GEM sensitivity, perhaps by down regulating STAT3/NF-κB signaling. © 2016 Wiley Periodicals, Inc.

Blockage of STAT3 Signaling Pathway by Morusin Induces Apoptosis and Inhibits Invasion in Human Pancreatic Tumor Cells

OBJECTIVES

Signal transducer and activator of transcription 3 (STAT3) is an oncogenic transcription factor implicated in carcinogenesis. Here, we investigated the role of morusin, the major prenylflavonoid, isolated from Chinese herbal medicine in abrogating the constitutive STAT3 activation in human pancreatic tumor cells.

METHODS

The effect of morusin on STAT3 activation, associated protein kinases, STAT3-regulated gene products, cellular proliferation, and apoptosis was examined.

RESULTS

Morusin specifically inhibited constitutive STAT3 activation both at tyrosine residue 705 and serine residue 727 in 4 pancreatic tumor cells. The inhibition of STAT3 was mediated through the suppression of activation of upstream JAK1, JAK2, and c-Src kinases. Morusin led to the accumulation of the cells in different phases of the cell cycle and caused induction of apoptosis and loss of mitochondrial membrane potential. Morusin downregulated the expression of various STAT3-regulated gene products; this correlated with induction of caspase-3 activation and anti-invasive effects. Treatment with the protein tyrosine phosphatase inhibitor pervanadate reversed the morusin-induced downregulation of STAT3, thereby suggesting the involvement of a protein tyrosine phosphatase.

CONCLUSIONS

Morusin is a novel blocker of STAT3 activation and thus may have potential in negative regulation of growth and metastasis of pancreatic tumor cells.

STAT3-Mediated Metabolic Reprograming in Cellular Transformation and Implications for Drug Resistance

Signal transducer and activator of transcription (STAT)3 mediates the signaling downstream of cytokine and growth factor receptors, regulating the expression of target genes. It is constitutively phosphorylated on tyrosine (Y-P) in many tumors, where its transcriptional activity can induce a metabolic switch toward aerobic glycolysis and down-regulate mitochondrial activity, a prominent metabolic feature of most cancer cells, correlating with reduced production of ROS, delayed senescence, and protection from apoptosis. STAT3 can, however, also localize to mitochondria, where its serine-phosphorylated (S-P) form preserves mitochondrial oxidative phosphorylation and controls the opening of the mitochondrial permeability transition pore, also promoting survival and resistance to apoptosis in response to specific signals/oncogenes such as RAS. Thus, downstream of different signals, both nuclear, Y-P STAT3, and mitochondrial, S-P STAT3, can act by promoting cell survival and reducing ROS production. Here, we discuss these properties in the light of potential connections between STAT3-driven alterations of mitochondrial metabolism and the development of drug resistance in cancer patients.

The inhibitory effects of xanthohumol, a prenylated chalcone derived from hops, on cell growth and tumorigenesis in human pancreatic cancer

Pancreatic cancer (PC) is one of the most lethal human malignancies worldwide. Here, we demonstrated that xanthohumol (XN), the most abundant prenylated chalcone isolated from hops, inhibited the growth of cultured PC cells and their subcutaneous xenograft tumors. XN treatment was found to induce cell cycle arrest and apoptosis of PC cells (PANC-1, BxPC-3) by inhibiting phosphorylation of signal transducer and activator of transcription 3 (STAT3) and expression of its downstream targeted genes cyclinD1, survivin, and Bcl-xL at the messenger RNA level, which involved in regulation of apoptosis and the cell cycle. Overall, our results suggested that XN presents a promising candidate therapeutic agent against human PC and the STAT3 signaling pathway is its key molecular target.

Novel thiosemicarbazones regulate the signal transducer and activator of transcription 3 (STAT3) pathway: inhibition of constitutive and interleukin 6-induced activation by iron depletion

Pharmacologic manipulation of metal pools in tumor cells is a promising strategy for cancer treatment. Here, we reveal how the iron-binding ligands desferrioxamine (DFO), di-2-pyridylketone-4,4-dimethyl-3-thiosemicarbazone (Dp44mT), and di-2-pyridylketone 4-cyclohexyl-4-methyl-3-thiosemicarbazone (DpC) inhibit constitutive and interleukin 6-induced activation of signal transducer and activator of transcription 3 (STAT3) signaling, which promotes proliferation, survival, and metastasis of cancer cells. We demonstrate that DFO, Dp44mT, and DpC significantly decrease constitutive phosphorylation of the STAT3 transcription factor at Tyr705 in the pancreatic cancer cell lines PANC-1 and MIAPaCa-2 as well as the prostate cancer cell line DU145. These compounds also significantly decrease the dimerized STAT3 levels, the binding of nuclear STAT3 to its target DNA, and the expression of downstream targets of STAT3, including cyclin D1, c-myc, and Bcl-2. Examination of upstream mediators of STAT3 in response to these ligands has revealed that Dp44mT and DpC could significantly decrease activation of the nonreceptor tyrosine kinase Src and activation of cAbl in DU145 and MIAPaCa-2 cells. In contrast to the effects of Dp44mT, DpC, or DFO on inhibiting STAT3 activation, the negative control compound di-2-pyridylketone 2-methyl-3-thiosemicarbazone, or the DFO:Fe complex, which cannot bind cellular iron, had no effect. This demonstrates the role of iron-binding in the activity observed. Immunohistochemical staining of PANC-1 tumor xenografts showed a marked decrease in STAT3 in the tumors of mice treated with Dp44mT or DpC compared with the vehicle. Collectively, these studies demonstrate suppression of STAT3 activity by iron depletion in vitro and in vivo, and reveal insights into regulation of the critical oncogenic STAT3 pathway.

MiR-1181 inhibits stem cell-like phenotypes and suppresses SOX2 and STAT3 in human pancreatic cancer

Recent studies have shown that cancer stem cells (CSCs) play an important role in the development of pancreatic cancer. Multiple oncogenes and signaling pathways have been confirmed to participate in the stemness maintenance and tumorigenicity of CSCs, including sex-determining region Y-box 2 (SOX2) and signal transduction and activation of transcription 3 (STAT3), which may provide novel therapeutic targets on pancreatic cancer. Here, we reported in pancreatic cancer tissues and cells that miR-1181 expression was markedly downregulated, and the low miR-1181 expression was associated with poorer overall survival and disease-free survival in pancreatic cancer patients. Furthermore, overexpression of miR-1181 inhibited, whereas downregulation of miR-1181 promoted, CSCs-like phenotypes in vitro and tumorigenicity in vivo in pancreatic cancer cells. Moreover, we demonstrated that miR-1181 directly suppressed SOX2 and STAT3 expression, resulting in downregulation of SOX2 and inhibition of the STAT3 pathway. Hence, our results suggest that miR-1181 plays a vital role in inhibiting the CSCs-like phenotypes in pancreatic cancer and might represent a potential target for anti-pancreatic cancer.

DNA microarray reveals ZNF195 and SBF1 are potential biomarkers for gemcitabine sensitivity in head and neck squamous cell carcinoma cell lines

Gemcitabine is a potential chemotherapy drug for treatment of head and neck squamous cell carcinoma (HNSCC), however, the poor or partial response of HNSCC patients to gemcitabine demonstrated the urgent need for gemcitabine biomarkers to improve the therapy. In present work, 10 HNSCC cell lines were employed to figure out the biomarkers for gemcitabine sensitivity. The sensitivities of these 10 cell lines to gemcitabine and the basal expression of these cell lines was investigated, the correlation between gemcitabine response (IC50 dose) and gene expression was investigated by Pearson correlation and FDR estimation. The top seven positive genes responsible for gemcitabine sensitivity were validated by qPCR in these 10 HNSCC cell lines, while only two genes (SBF1 and ZNF195) were expression-correlated to gemcitabine response. Furthermore, ZNF195 expression was closely associated with gemcitabine sensitivity in the subsequent independent validation in cell lines from various types of cancer. Our work might provide potential biomarkers for gemcitabine sensitivity in HNSCC and various type of cancer.