Pancreatic carcinoma cell lines with SMAD4 inactivation show distinct expression responses to TGFB1

Exosomal circPACRGL promotes progression of colorectal cancer via the miR-142-3p/miR-506-3p- TGF-β1 axis

BACKGROUND

Colorectal cancer (CRC) is the leading cause of cancer-related death worldwide. Exosome shave emerged as crucial regulators of intercellular communication and that abundant Circular RNAs (circRNAs) are enriched within exosomes. CircRNAs are novel members of noncoding RNAs regulating cancer proliferation and progression. However, the function and regulatory mechanism of cancer-derived exosomal circRNAs in CRC remains unclear.

METHODS

CRC cells-derived exosomes were characterized using transmission electron microscopy, nanoparticle tracking analysis (NTA) and western blot. CCK-8, wound healing and transwell assays, and flow cytometry assays were conducted to assess whether exosomes would affect the proliferation, metastasis, and apoptosis of CRC cells, respectively. Moreover, we performed the RNA sequencing and RT-qPCR to identify circRNAs in exosome-stimulated CRC cells. Fluorescence in situ hybridization (FISH) assay was used to detect the cellular distribution of circPACRGL. Bioinformatic analyses (StarBase 2.0) were used to pool the miRNA targets of circPACRGL. Luciferase assays were performed to verify the direct interaction. Finally, flow cytometry was used to detect the differentiation of N1-N2 neutrophils.

RESULTS

Our study identified a novel CRC-derived exosomal circRNA, circPACRGL. We found circPACRGL was significantly upregulated in CRC cells after tumor-derived exosomes addition. Moreover, circPACRGL serves as a sponge for miR-142-3p/miR-506-3p to facilitate the transforming growth factor-β1 (TGF-β1) expression. As a result, circPACRGL promoted CRC cell proliferation, migration and invasion, as well as differentiation of N1 to N2 neutrophils via miR-142-3p/miR-506-3p-TGF-β1 axis.

CONCLUSION

Our study, the first to reveal that cancer-derived exosomal circPACRGL plays an oncogenic role in CRC proliferation and metastasis, providing mechanistic insights into the roles of circRNAs in CRC progression and a valuable marker for CRC treatment.

Recent advances in pancreatic cancer: biology, treatment, and prevention

Pancreatic cancer (PC) is the fourth leading cause of cancer-related death in United States. Efforts have been made towards the development of the viable solution for its treatment with constrained accomplishment because of its complex biology. It is well established that pancreatic cancer stem cells (CSCs), albeit present in a little count, contribute incredibly to PC initiation, progression, and metastasis. Customary chemo and radiotherapeutic alternatives, however, expands general survival, the related side effects are the significant concern. Amid the most recent decade, our insight about molecular and cellular pathways involved in PC and role of CSCs in its progression has increased enormously. Presently the focus is to target CSCs. The herbal products have gained much consideration recently as they, usually, sensitize CSCs to chemotherapy and target molecular signaling involved in various tumors including PC. Some planned studies have indicated promising results proposing that examinations in this course have a lot to offer for the treatment of PC. Although preclinical studies uncovered the importance of herbal products in attenuating pancreatic carcinoma, limited studies have been conducted to evaluate their role in clinics. The present review provides a new insight to recent advances in pancreatic cancer biology, treatment and current status of herbal products in its anticipation.

Growth inhibition induced by transforming growth factor-beta1 in human oral squamous cell carcinoma

Oral squamous cell carcinoma (OSCC) is a world-wide health problem and its incidence accounts for 1.9-3.5% of all malignant tumors. Transforming growth factor beta/Smads (TGF-beta/Smads) signaling pathway plays an important role in oncogenesis, but its function and molecular mechanisms in OSCC remain unclear. Expression of transforming growth factor-beta receptor type II (TbetaRII) and Smad4 was studied by immunohistochemistry in 108 OSCC patients and 10 normal controls. Function and molecular mechanisms of TGF-beta/Smads signaling pathway was then investigated in two human tongue squamous carcinoma cell lines with high and low metastasis (Tb and Tca8113) by RT-PCR, Western Blot, immunofluorescence, cell growth curve and flow cytometry (FCM), respectively. TbetaRII and Smad4 were significantly down-regulated in tumor tissues (with or without lymph node metastasis) compared to normal oral epithelium tissues (P < 0.05). TGF-beta1 induced arrest of the cell cycle rather than cell death in Tca8113 and Tb cells, and this influence was mediated by the increasing the expression and changing the location of its downstream components of TGF-beta1/Smads signaling pathway. TGF-beta1 rapidly increased the expression of p15 and p21 in both Tca8113 and Tb cells. TGF-beta1 did not increase p27 expression in Tca8113 cells, but p27 expression was increased in Tb cells. These indicated that TGF-beta1 induced G(1) arrest of cell cycle through a different regulating pathway in Tb cells compared with Tca8113 cells. Thus, we conclude that TGF-beta/Smads signaling pathway play a important role on cell growth and metastasis potential in OSCC.

Expression profiling of genes regulated by TGF-beta: differential regulation in normal and tumour cells

Background

TGF-beta is one of the key cytokines implicated in various disease processes including cancer. TGF-beta inhibits growth and promotes apoptosis in normal epithelial cells and in contrast, acts as a pro-tumour cytokine by promoting tumour angiogenesis, immune-escape and metastasis. It is not clear if various actions of TGF-beta on normal and tumour cells are due to differential gene regulations. Hence we studied the regulation of gene expression by TGF-beta in normal and cancer cells.

Results

Using human 19 K cDNA microarrays, we show that 1757 genes are exclusively regulated by TGF-beta in A549 cells in contrast to 733 genes exclusively regulated in HPL1D cells. In addition, 267 genes are commonly regulated in both the cell-lines. Semi-quantitative and real-time qRT-PCR analysis of some genes agrees with the microarray data. In order to identify the signalling pathways that influence TGF-beta mediated gene regulation, we used specific inhibitors of p38 MAP kinase, ERK kinase, JNK kinase and integrin signalling pathways. The data suggest that regulation of majority of the selected genes is dependent on at least one of these pathways and this dependence is cell-type specific. Interestingly, an integrin pathway inhibitor, RGD peptide, significantly affected TGF-beta regulation of Thrombospondin 1 in A549 cells.

Conclusion

These data suggest major differences with respect to TGF-beta mediated gene regulation in normal and transformed cells and significant role of non-canonical TGF-beta pathways in the regulation of many genes by TGF-beta.

Basement membrane component laminin-5 is a target of the tumor suppressor Smad4

The tumor suppressor Smad4 is involved in carcinogenesis mainly of the pancreas and colon. Functional inactivation of Smad4 is a genetically late event that occurs upon transition from premalignant stages to invasive and metastatic growth. Smad4 encodes an intracellular messenger common to all signalling cascades induced by members of the transforming growth factor-beta (TGF-beta) superfamily of cytokines. Despite extensive knowledge about the mechanisms of TGF-beta/Smad signal transduction, little is known about Smad4 targets involved in the transition to malignancy. The hallmark of invasive growth is a breakdown of the basement membrane (BM), a specialized sheet of extracellular matrix produced through cooperation of epithelial and stromal cells. Laminin-5, a heterotrimeric epithelial-derived BM component, is commonly lost in carcinomas but not in premalignant tumors. Herein, we report that in human colon and pancreatic tumor cells, Smad4 functions as a positive transcriptional regulator of all three genes encoding laminin-5. Coordinate re-expression of the three laminin-5 chains induced by reconstitution of Smad4 leads to secretion and deposition of the heterotrimeric molecule in BM-like structures. These data define the expression control of an essential BM component as a novel function for the tumor suppressor Smad4.

Smad4 is dispensable for normal pancreas development yet critical in progression and tumor biology of pancreas cancer

SMAD4 is inactivated in the majority of pancreatic ductal adenocarcinomas (PDAC) with concurrent mutational inactivation of the INK4A/ARF tumor suppressor locus and activation of the KRAS oncogene. Here, using genetically engineered mice, we determined the impact of SMAD4 deficiency on the development of the pancreas and on the initiation and/or progression of PDAC-alone or in combination with PDAC--relevant mutations. Selective SMAD4 deletion in the pancreatic epithelium had no discernable impact on pancreatic development or physiology. However, when combined with the activated KRAS(G12D) allele, SMAD4 deficiency enabled rapid progression of KRAS(G12D)-initiated neoplasms. While KRAS(G12D) alone elicited premalignant pancreatic intraepithelial neoplasia (PanIN) that progressed slowly to carcinoma, the combination of KRAS(G12D) and SMAD4 deficiency resulted in the rapid development of tumors resembling intraductal papillary mucinous neoplasia (IPMN), a precursor to PDAC in humans. SMAD4 deficiency also accelerated PDAC development of KRAS(G12D) INK4A/ARF heterozygous mice and altered the tumor phenotype; while tumors with intact SMAD4 frequently exhibited epithelial-to-mesenchymal transition (EMT), PDAC null for SMAD4 retained a differentiated histopathology with increased expression of epithelial markers. SMAD4 status in PDAC cell lines was associated with differential responses to transforming growth factor-beta (TGF-beta) in vitro with a subset of SMAD4 wild-type lines showing prominent TGF-beta-induced proliferation and migration. These results provide genetic confirmation that SMAD4 is a PDAC tumor suppressor, functioning to block the progression of KRAS(G12D)-initiated neoplasms, whereas in a subset of advanced tumors, intact SMAD4 facilitates EMT and TGF-beta-dependent growth.

Pancreatic cancer cells invasiveness is mainly affected by interleukin-1beta not by transforming growth factor-beta1

BACKGROUND

We investigated in vitro whether IL-1beta and TGF-beta1 affect pancreatic cancer cell growth, adhesion to the extracellular matrix and Matrigel invasion.

MATERIALS AND METHODS

Adhesion to fibronectin, laminin and type I collagen, and Matrigel invasion after stimulation with saline, IL-1beta and TGF-beta1 were evaluated using three primary and three metastatic pancreatic cancer cell lines.

RESULTS

Extracellular matrix adhesion of control cells varied independently of the metastatic characteristics of the studied cell lines, whereas Matrigel invasion of control cells was partly correlated with the in vivo metastatic potential. IL-1beta did not influence extracellular matrix adhesion, whereas it significantly enhanced the invasiveness of three of the six cell lines. TGF-beta1 affected the adhesion of one cell line, and exerted contrasting effects on Matrigel invasion of different cell lines.

CONCLUSIONS

IL-1beta enhances the invasive capacity of pancreatic cancer cells, whereas TGF-beta1 has paradoxical effects on pancreatic cancer cells; this makes it difficult to interfere with TGF-beta1 signaling in pancreatic cancer treatment.

The inherited genetics of pancreatic cancer and prospects for secondary screening

It is estimated that pancreatic cancer has a familial component in approximately 5-10% of cases. Some of these cases are part of a defined cancer syndrome with a known gene mutation but in the remaining the causative gene remains unknown. In recent years, a better understanding of the molecular events that occur in the progression model of pancreatic cancer has lead to the development of secondary screening programmes with the aim of identifying early precursor lesions or pre-invasive cancer at a stage amenable to curative resection. High-risk groups who have an inherited predisposition for pancreatic cancer form the ideal group to study in developing a robust screening programme. Multimodality screening using computed tomography and endoluminal ultrasound in combination with molecular analysis of pancreatic juice are proving promising as diagnostics tools or at least serving as predictors of risk over a defined period.

Characterization of gene expression in major types of salivary gland carcinomas with epithelial differentiation

Gene expression profiles were studied in 13 cases of salivary gland carcinoma including mucoepidermoid carcinoma (MEC), acinic cell carcinoma (ACC), and salivary duct carcinoma (SDC) using a cDNA array. A total of 162 genes were deregulated. Only 5 genes were overexpressed in all carcinomas including fibronectin 1 (FN1), tissue metalloproteinase inhibitor 1 (TIMP1), biglycan (BGN), tenascin-C (HXB), and insulin-like growth factor binding protein 5 (IGFBP5), whereas 16 genes were underexpressed. The small number of similarly deregulated genes in these carcinoma entities suggests an extensive genetic variation between them. This result agrees with the great histopathological diversity of different entities of salivary gland carcinoma. Furthermore, diversity in gene expression between the carcinoma types was identified also by hierarchical clustering. Each carcinoma entity was clustered together but MEC, SDC, and ACC were separated from each other. Significance analysis of microarrays identified 27 genes expressed differently between the groups. In MEC, overexpressed genes included those of cell proliferation (IL-6 and SFN) and cell adhesion (SEMA3F and COL6A3), whereas many underexpressed genes were related to DNA modification (NTHL1 and RBBP4). Apoptosis-related genes CASP10 and MMP11 were overexpressed in SDC, in accordance with the typical tumor necrosis seen in this entity. An intermediate filament protein of basal epithelial cells, cytokeratin 14 (KRT14) was clearly differently expressed between the 3 types of carcinoma, and can be used as an aid in their differential diagnosis. The array results were validated by RT-PCR and immunohistochemistry.

Targeting endogenous transforming growth factor beta receptor signaling in SMAD4-deficient human pancreatic carcinoma cells inhibits their invasive phenotype1

Transforming growth factor-beta (TGF-beta) suppresses tumor formation by blocking cell cycle progression and maintaining tissue homeostasis. In pancreatic carcinomas, this tumor suppressive activity is often lost by inactivation of the TGF-beta-signaling mediator, Smad4. We found that human pancreatic carcinoma cell lines that have undergone deletion of MADH4 constitutively expressed high endogenous levels of phosphorylated receptor-associated Smad proteins (pR-Smad2 and pR-Smad3), whereas Smad4-positive lines did not. These elevated pR-Smad levels could not be attributed to a decreased dephosphorylation rate nor to increased expression of TGF-beta type I (TbetaR-I) or type II (TbetaR-II) receptors. Although minimal amounts of free bioactive TGF-beta1 and TGF-beta2 were detected in conditioned medium, treatment with a pan-specific (but not a TGF-beta3 specific) TGF-beta-neutralizing antibody and with anti-alpha(V)beta(6) integrin antibody decreased steady-state pSmad2 levels and activation of a TGF-beta-inducible reporter gene in neighboring cells, respectively. Thus, activation of TGF-beta at the cell surface was responsible for the increased autocrine endogenous and paracrine signaling. Blocking TbetaR-I activity using a selective kinase inhibitor (SD-093) strongly decreased the in vitro motility and invasiveness of the pancreatic carcinoma cells without affecting their growth characteristics, morphology, or the subcellular distribution of E-cadherin and F-actin. Moreover, exogenous TGF-beta strongly stimulated in vitro invasiveness of BxPC-3 cells, an effect that could also be blocked by SD-093. Thus, the motile and invasive properties of Smad4-deficient pancreatic cancer cells are at least partly driven by activation of endogenous TGF-beta signaling. Therefore, targeting the TbetaR-I kinase represents a potentially powerful novel therapeutic approach for the treatment of this disease.

Cirrhotic hepatocytes exhibit decreased TGFβ growth inhibition associated with downregulated Smad protein expression

TGFbeta controls hepatocyte growth through cell cycle arrest and apoptosis, and resistance to TGFbeta is a mechanism of malignant transformation. The aim of this study was to assess differences in TGFbeta-mediated growth inhibition in normal and cirrhotic hepatocytes. Cirrhosis was induced in mice and normal and cirrhotic hepatocytes were isolated by collagenase perfusion and treated with or without TGFbeta (5 ng/ml). DNA synthesis, Smad protein expression, and DNA binding activity were determined. TGFbeta reduced DNA synthesis to a greater degree in normal hepatocytes than in cirrhotic hepatocytes (87% vs. 68%; p<0.05). Smad protein expression was decreased in cirrhotic hepatocytes and Smad 2/3/4 complex formation was suppressed. Furthermore, cirrhotic hepatocytes had decreased DNA binding activity at 120 min following TGFbeta treatment. In conclusion, decreased Smad protein expression may impair TGFbeta-mediated growth inhibition in cirrhotic hepatocytes.