5-Azacytidine suppresses the proliferation of pancreatic cancer cells by inhibiting the Wnt/β-catenin signaling pathway

Understanding and targeting anoikis in metastasis for cancer therapies

The development of effective treatments for cancers requires investigations for a more detailed and comprehensive understanding of the basic cellular mechanisms involved in carcinogenesis, cancer progression, and metastasis. One of those driving mechanisms is anoikis, a special type of apoptosis, which is induced by losing anchorage from the extracellular matrix (ECM). In other words, resisting death in detached cells (cells without ECM) forms an anoikis-resistant phenotype. Since the anoikis-resistance state compensates for the initial steps of cancer metastasis, this review aimed to discuss mechanisms of gaining anoikis/anoikis resistance phenotype in tumor cells. Finally, we highlighted the significance of anoikis in malignancies so as to provide clear insight into cancer diagnosis and therapy development.

Inhibiting DNA methylation as a strategy to enhance adipose-derived stem cells differentiation: Focus on the role of Akt/mTOR and Wnt/β-catenin pathways on adipogenesis

Adipose-derived mesenchymal stem cells (ASCs) represent a valid therapeutic option for clinical application in several diseases, due to their ability to repair damaged tissues and to mitigate the inflammatory/immune response. A better understanding of the underlying mechanisms regulating ASC biology might represent the chance to modulate their in vitro characteristics and differentiation potential for regenerative medicine purposes. Herein, we investigated the effects of the demethylating agent 5-azacytidine (5-aza) on proliferation, clonogenicity, migration, adipogenic differentiation and senescence of ASCs, to identify the molecular pathways involved. Through functional assays, we observed a detrimental effect of 5-aza on ASC self-renewal capacity and migration, accompanied by actin cytoskeleton reorganization, with decreased stress fibers. Conversely, 5-aza treatment enhanced ASC adipogenic differentiation, as assessed by lipid accumulation and expression of lineage-specific markers. We analyzed the involvement of the Akt/mTOR, MAPK and Wnt/β-catenin pathways in these processes. Our results indicated impairment of Akt and ERK phosphorylation, potentially explaining the reduced cell proliferation and migration. We observed a 5-aza-mediated inhibition of the Wnt signaling pathway, this potentially explaining the pro-adipogenic effect of the drug. Finally, 5-aza treatment significantly induced ASC senescence, through upregulation of the p53/p21 axis. Our data may have important translational implications, by helping in clarifying the potential risks and advantages of using epigenetic treatment to improve ASC characteristics for cell-based clinical approaches.

GPX2 silencing relieves epithelial-mesenchymal transition, invasion, and metastasis in pancreatic cancer by downregulating Wnt pathway

Glutathione peroxidase 2 (GPX2) participates in many cancers including pancreatic cancer (PC), and overexpression of GPX2 promotes tumor growth. Herein, we identified the role of GPX2 in epithelial-mesenchymal transformation (EMT), invasion, and metastasis in PC. Bioinformatics prediction was applied to select PC-related genes. The regulatory function of GPX2 in PC was explored by treatment with short hairpin RNA against GPX2 or LiCl (activator of wingless-type MMTV integration site [Wnt] pathway) in PC cells. GPX2 level in PC tissues, the levels of GPX2, β-catenin, Vimentin, Snail, epithelial-cadherin (E-cadherin), matrix metalloproteinase 2 (MMP2), MMP9, and Wnt2 in cells were determined. Subsequently, cell proliferation, invasion, and metastasis were assayed. Bioinformatics analysis revealed that GPX2 was involved in PC development mediated by the Wnt pathway. GPX2 was highly expressed in PC tissues. GPX2 silencing downregulated levels of β-catenin, Vimentin, Snail, MMP2, MMP9, and Wnt2 but upregulated levels of E-cadherin. It was confirmed that GPX2 silencing suppressed PC cell proliferation, metastasis, and invasion. Furthermore, the trend of EMT and invasion and metastasis of PC induced by the LiCl-activated Wnt pathway was reversed when the GPX2 was silenced. GPX2 silencing could inhibit the Wnt pathway, subsequently suppress PC development.

SOX17, β-catenin and CyclinD1 expression in the endometrioid adenocarcinoma and influence of 5-AZA on expression

The present study discusses the expression and effect of the SOX17 gene in endometrioid adenocarcinoma. MTT assay is performed to determine the growth inhibition ratio of the DNA methyltransferase inhibitor 5-AZA for endometrial carcinoma cells, and the real-time fluorescence quantification PCR (qRT-PCR) was used to detect the mRNA expression of SOX17, β-catenin, and CyclinD1 in endometrial carcinoma tissues before and after using 5-AZA to treat the endometrial carcinoma cell line. There were 30 cases on endometrioid adenocarcinoma tissues and 10 cases on normal endometrial tissues. The results revealed that the expression of SOX17 in endometrioid adenocarcinoma tissues was downregulated (P < 0.05), the expression of β-catenin and CyclinD1 was upregulated (P < 0.05), and the expression of SOX17, CyclinD1, and β-catenin was negatively correlated (r = -0.353, P > 0.05; R = -0.463, P < 0.05). The higher the histological grade and FIGO staging were, the lower the expression level of SOX17 was (P < 0.05). After HEC1A cells were treated by 5-AZA, the cell growth inhibition was most obvious (IC₅₀ = 12.033) at 72 h, as determined by MTT assay. After cell treatment by 5-AZA, the genetic expression of SOX17 significantly increased, when compared with that before treatment (P < 0.05), while the genetic expression of β-catenin and CyclinD1 significantly declined (P < 0.05). These results indicate that the expression level of SOX17 in endometrioid adenocarcinoma declined, and the upregulated expression level of SOX17 in cells inhibited the growth of tumor cells.

Wnt/β-Catenin Signaling: The Culprit in Pancreatic Carcinogenesis and Therapeutic Resistance

Pancreatic ductal adenocarcinoma (PDAC) is responsible for 7.3% of all cancer deaths. Even though there is a steady increase in patient survival for most cancers over the decades, the patient survival rate for pancreatic cancer remains low with current therapeutic strategies. The Wnt/β-catenin pathway controls the maintenance of somatic stem cells in many tissues and organs and is implicated in pancreatic carcinogenesis by regulating cell cycle progression, apoptosis, epithelial-mesenchymal transition (EMT), angiogenesis, stemness, tumor immune microenvironment, etc. Further, dysregulated Wnt has been shown to cause drug resistance in pancreatic cancer. Although different Wnt antagonists are effective in pancreatic patients, limitations remain that must be overcome to increase the survival benefits associated with this emerging therapy. In this review, we have summarized the role of Wnt signaling in pancreatic cancer and suggested future directions to enhance the survival of pancreatic cancer patients.

Signalling pathway impact analysis based on the strength of interaction between genes

Signalling pathway analysis is a popular approach that is used to identify significant cancer‐related pathways based on differentially expressed genes (DEGs) from biological experiments. The main advantage of signalling pathway analysis lies in the fact that it assesses both the number of DEGs and the propagation of signal perturbation in signalling pathways. However, this method simplifies the interactions between genes by categorising them only as activation (+1) and suppression (−1), which does not encompass the range of interactions in real pathways, where interaction strength between genes may vary. In this study, the authors used newly developed signalling pathway impact analysis (SPIA) methods, SPIA based on Pearson correlation coefficient (PSPIA), and mutual information (MSPIA), to measure the interaction strength between pairs of genes. In analyses of a colorectal cancer dataset, a lung cancer dataset, and a pancreatic cancer dataset, PSPIA and MSPIA identified more candidate cancer‐related pathways than were identified by SPIA. Generally, MSPIA performed better than PSPIA.

Wnt Signaling in Renal Cell Carcinoma

Renal cell carcinoma (RCC) accounts for 90% of all kidney cancers. Due to poor diagnosis, high resistance to the systemic therapies and the fact that most RCC cases occur sporadically, current research switched its focus on studying the molecular mechanisms underlying RCC. The aim is the discovery of new effective and less toxic anti-cancer drugs and novel diagnostic markers. Besides the PI3K/Akt/mTOR, HGF/Met and VHL/hypoxia cellular signaling pathways, the involvement of the Wnt/β-catenin pathway in RCC is commonly studied. Wnt signaling and its targeted genes are known to actively participate in different biological processes during embryonic development and renal cancer. Recently, studies have shown that targeting this pathway by alternating/inhibiting its intracellular signal transduction can reduce cancer cells viability and inhibit their growth. The targets and drugs identified show promising potential to serve as novel RCC therapeutics and prognostic markers. This review aims to summarize the current status quo regarding recent research on RCC focusing on the involvement of the Wnt/β-catenin pathway and how its understanding could facilitate the identification of potential therapeutic targets, new drugs and diagnostic biomarkers.

Clinicopathological Implications of Wingless/int1 (WNT) Signaling Pathway in Pancreatic Ductal Adenocarcinoma

Pancreatic cancer is still one of the most lethal malignancies in the world, and a more thorough understanding of its detailed pathogenetic mechanisms and the development of more effective therapeutic strategies are urgently required. Pancreatic ductal adenocarcinoma (PDA), the most common type of pancreatic cancer, is characterized by consistent genetic abnormalities such as point mutations in the Kirsten rat sarcoma viral oncogene homolog (KRAS) and in the tumor suppressor protein p53 (TP53) genes. Alterations in intracellular core signal pathways have also been shown to induce the development or progression of PDA. The Wingless/int1 (WNT) signal pathway plays a pivotal role in embryonic development, cellular proliferation and differentiation, and dysregulation of WNT signaling can lead to neoplastic transformation in a variety of organ systems, including the pancreas. Recent studies have shown that altered WNT signaling is associated with a poor prognosis in patients with PDA, suggesting that the pathway is a predictor of patients' survival and a potential therapeutic target of PDA. In this review, the clinicopathological implications of WNT signaling in PDA are highlighted.

Abnormal methylation in pancreatic cancer

Pancreatic cancer is one of the most aggressive malignancies in the world and has a poor prognosis. Since most cases have already had local invasion or distant metastasis at diagnosis, they usually lost the opportunity for effective surgical resection. Thus, early detection and treatment are of great clinical significance for reducing mortality. Epigenetic changes play an important role in the occurrence of cancers. Abnormal methylation is an important part of epigenetic theory. Here we discuss abnormal methylation of multiple genes in pancreatic cancer, with an aim to find methods of early diagnosis and treatment for this devastating disease.

PLK2 phosphorylates and inhibits enriched TAp73 in human osteosarcoma cells

TAp73, a member of the p53 tumor suppressor family, can substitute for p53 function, especially in p53‐null and p53‐mutant cells. However, TAp73 enrichment and phosphorylation change its transcriptional activity. Previously, we found that the antitumor function of TAp73 was reactivated by dephosphorylation. Polo‐like kinase 2 (PLK2) plays an important role in bone development. Using a biological information database and phosphorylation prediction software, we hypothesized that PLK2 phosphorylates TAp73 and inhibits TAp73 function in osteosarcomas. Actually,we determined that PLK2 physically binds to and phosphorylates TAp73 when TAp73 protein abundance is up‐regulated by cisplatin. PLK2‐phosphorylated TAp73 at residue Ser48 within the TA domain; phosphorylation of TAp73 was abolished by mutating this residue. Moreover, PLK2 inhibition combined with cisplatin treatment in osteosarcoma Saos2 cells up‐regulated p21 and puma mRNA expression to a greater extent than cisplatin treatment alone. Inhibiting PLK2 in TAp73‐enriched Saos2 cells resulted in inhibited cell proliferation, increased apoptosis, G1 phase arrest, and decreased cell invasion. However, these changes did not occur in TAp73 knockdown Saos2 cells. In conclusion, these findings reveal a novel PLK2 function in the phosphorylation of TAp73, which prevents TAp73 activity in osteosarcoma cells. Thereby, this research provides an insight into the clinical treatment of malignant tumors overexpressing TAp73.

Co‑expression of the carbamoyl‑phosphate synthase 1 gene and its long non‑coding RNA correlates with poor prognosis of patients with intrahepatic cholangiocarcinoma

The mechanisms leading to high rates of malignancy and recurrence of human intrahepatic cholangiocarcinoma (ICC) remain unclear. It is difficult to diagnose and assess the prognosis of patients with ICC in the clinic due to the lack of specific biomarkers. In addition, long non-coding RNAs (lncRNAs) have been reported to serve important roles in certain types of tumorigenesis however a role in ICC remains to be reported. The aim of the current study was to screen for genes and lncRNAs that are abnormally expressed in ICC and to investigate their biological and clinicopathological significance in ICC. The global gene and lncRNA expression profiles in ICC were measured using bioinformatics analysis. Carbamoyl-phosphate synthase 1 (CPS1) and its lncRNA CPS1 intronic transcript 1 (CPS1-IT1) were observed to be upregulated in ICC. The expression of CPS1 and CPS1-IT1 was measured in 31 tissue samples from patients with ICC and a number of cell lines. The effects of CPS1 and CPS1-IT1 on the proliferation and apoptosis of the ICC-9810 cell line were measured. In addition, the clinicopathological features and survival rates of patients with ICC with respect to the gene and lncRNA expression status were analyzed. CPS1 and CPS1-IT1 were co-upregulated in ICC tissues compared with non-cancerous tissues. Knockdown of CPS1 andor CPS1-IT1 reduced the proliferation and increased the apoptosis of ICC-9810 cells. Additionally, clinical analysis indicated that CPS1 and CPS1-IT1 were associated with poor liver function and reduced survival rates when the relative expression values were greater than 4 in cancer tissues. The comparisons between the high CPS1 expression group and the low expression group indicated significant differences in international normalized ratio (P=0.048), total protein (P=0.049), indirect bilirubin (P=0.025), alkaline phosphatase (P=0.003) and disease-free survival (P=0.034). In addition, there were differential trends in CA19-9 (P=0.068), globulin (P=0.052) and total bilirubin (P=0.066). The comparisons between the high CPS1-IT1 expression group and the low expression group indicated significant differences in lymphatic invasion (P=0.045), carbohydrate antigen 19-9 (P=0.044), disease-free survival (P=0.026), and non-significant differential trends in alkaline phosphatase were observed (P=0.085). In conclusion, CPS1 and CPS1-IT1 may serve an important role in ICC development by promoting the proliferation of ICC cells. Furthermore, CPS1 and CPS1-IT1 were associated with poor liver function and reduced survival rates. Thus, CPS1 and CPS1-IT1 may be potential prognostic indicators for patients with ICC.

TMPyP4-regulated cell proliferation and apoptosis through the Wnt/β-catenin signaling pathway in SW480 cells

BACKGROUND

The aim of this study was to investigate the potential effects of the 5, 10, 15, 20-tetrakis (1-methylpyridinium-4-yl) porphyrin (TMPyP4) on the proliferation and apoptosis of SW480 cells and the underlying mechanisms by which TMPyP4 exerted its actions.

METHODS

After treated with different doses of TMPyP4, cell viability was determined by MTT method, the apoptosis was observed by flow cytometry (FCM) and the expression of Wnt, GSK-3β, β-catenin and cyclinD1 was measured by RT-PCR and Western blot analysis.

RESULTS

The analysis revealed that TMPyP4 potently suppressed cell viability and induced the apoptosis of SW480 cells in a dose-dependent manner. In addition, the downregulation of Wnt, β-catenin and cyclinD1 expression levels was detected in TMPyP4-treated SW480 cells. However, followed by the block of Wnt signaling pathway using siRNA methods, the effects of TMPyP4 on proliferation and apoptosis of SW480 cells were significantly reduced.

CONCLUSION

It indicates that the TMPyP4-inhibited proliferation and -induced apoptosis in SW480 cells was accompanied by the suppression of Wnt/β-catenin signaling pathway. Therefore, TMPyP4 may represent a potential therapeutic method for the treatment of colon carcinoma.

Anoikis-resistant subpopulations of human osteosarcoma display significant chemoresistance and are sensitive to targeted epigenetic therapies predicted by expression profiling

Background

Osteosarcoma (OS) is the most common type of solid bone cancer, with latent metastasis being a typical mode of disease progression and a major contributor to poor prognosis. For this to occur, cells must resist anoikis and be able to recapitulate tumorigenesis in a foreign microenvironment. Finding novel approaches to treat osteosarcoma and target those cell subpopulations that possess the ability to resist anoikis and contribute to metastatic disease is imperative. Here we investigate anchorage-independent (AI) cell growth as a model to better characterize anoikis resistance in human osteosarcoma while using an expression profiling approach to identify and test targetable signaling pathways.

Methods

Established human OS cell lines and patient-derived human OS cell isolates were subjected to growth in either adherent or AI conditions using Ultra-Low Attachment plates in identical media conditions. Growth rate was assessed using cell doubling times and chemoresistance was assessed by determining cell viability in response to a serial dilution of either doxorubicin or cisplatin. Gene expression differences were examined using quantitative reverse-transcription PCR and microarray with principal component and pathway analysis. In-vivo OS xenografts were generated by either subcutaneous or intratibial injection of adherent or AI human OS cells into athymic nude mice. Statistical significance was determined using student’s t-tests with significance set at α = 0.05.

Results

We show that AI growth results in a global gene expression profile change accompanied by significant chemoresistance (up to 75 fold, p < 0.05). AI cells demonstrate alteration of key mediators of mesenchymal differentiation (β-catenin, Runx2), stemness (Sox2), proliferation (c-myc, Akt), and epigenetic regulation (HDAC class 1). AI cells were equally tumorigenic as their adherent counterparts, but showed a significantly decreased rate of growth in-vitro and in-vivo (p < 0.05). Treatment with the pan-histone deacetylase inhibitor vorinostat and the DNA methyltransferase inhibitor 5-azacytidine mitigated AI growth, while 5-azacytidine sensitized anoikis-resistant cells to doxorubicin (p < 0.05).

Conclusions

These data demonstrate remarkable plasticity in anoikis-resistant human osteosarcoma subpopulations accompanied by a rapid development of chemoresistance and altered growth rates mirroring the early stages of latent metastasis. Targeting epigenetic regulation of this process may be a viable therapeutic strategy.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-015-0466-4) contains supplementary material, which is available to authorized users.