Activation of IGF/IGF-IR signaling pathway fails to induce epithelial-mesenchymal transition in pancreatic cancer cells

SOX9 Protein in Pancreatic Cancer Regulates Multiple Cellular Networks in a Cell-Specific Manner

SOX9 is upregulated in the majority of pancreatic ductal adenocarcinoma cases. It is hypothesized that the increased expression of SOX9 is necessary for the formation and maintenance of tumor phenotypes in pancreatic cancer cells. In our research, we studied six pancreatic cancer cell lines, which displayed varying levels of differentiation and a range of oncogenic mutations. We chose the method of downregulation of SOX9 expression via siRNA transfection as the main method for investigating the functional role of the SOX9 factor in pancreatic cancer cells. We discovered that the downregulation of SOX9 expression in the cell lines leads to cell-line-specific changes in the expression levels of epithelial and mesenchymal protein markers. Additionally, the downregulation of SOX9 expression had a specific effect on the expression of pancreatic developmental master genes. SOX9 downregulation had the greatest effect on the expression levels of the protein regulators of cell proliferation. In three of the four cell lines studied, the transfection of siSOX9 led to a significant decrease in proliferative activity and to the activation of proapoptotic caspases in transfected cells. The acquired results demonstrate that the SOX9 protein exerts its multiple functions as a pleiotropic regulator of differentiation and a potential promoter of tumor growth in a cell-specific manner in pancreatic cancer cells.

miRNA‑7515 suppresses pancreatic cancer cell proliferation, migration and invasion via downregulating IGF‑1 expression

Pancreatic cancer (PC) is a lethal malignancy of the gastrointestinal tract. Previous studies have reported that microRNAs (miRNAs/miRs) are involved in the tumorigenesis of PC. Therefore, the present study aimed to determine the effects of miR‑7515 on PC cell proliferation, invasion and migration in vitro and in vivo, and investigate its underlying molecular mechanism using bioinformatics, double luciferase assay and western blotting. The results revealed that the expression levels of miR‑7515 were downregulated in PC, which predicted a poor clinical outcome. The overexpression of miR‑7515 significantly decreased the proliferation, invasive and migratory abilities of PC cells in vitro and in vivo, while the knockdown of miR‑7515 exerted the opposite effects. miR‑7515 was identified to directly bind to insulin‑like growth factor 1 (IGF‑1) and downregulate its expression, which subsequently downregulated the Ras/Raf/MEK/ERK signalling pathway. The overexpression of IGF‑1 reversed the inhibitory effects of miR‑7515 overexpression on PC cells. In conclusion, the findings of the present study indicated that miR‑7515 may act as a tumor suppressor in PC, as it repressed PC cell proliferation invasion and migration via downregulating the expression of IGF‑1 and the activity of the Ras/Raf/MEK/ERK signalling pathways.

Dysregulation of miRNAs Targeting the IGF-1R Pathway in Pancreatic Ductal Adenocarcinoma

Background: Pancreatic ductal adenocarcinoma (PDAC), the most prevalent neoplastic lethal pancreatic disease, has a poor prognosis and an increasing incidence. The insulin-like growth factor-1 receptor (IGF-1R) signaling pathway is considered to be a contributing factor to the progression, metastasis, and therapy resistance of PDAC. Currently available treatment options for PDAC are limited, but microRNAs (miRNAs) may represent a new therapeutic strategy for targeting genes involved in the IGF-1R signaling pathway. Method: We investigated the expression levels of 21 miRNAs involved in the IGF-1R signaling pathway in pancreatic tissue from 38 patients with PDAC and 11 controls (five patients with chronic pancreatitis and six patients with normal pancreatic tissue). Results: We found 19 differentially expressed miRNAs between the PDAC cases and the controls. In particular, miR-100-5p, miR-145-5p, miR-29c-3p, miR-9-5p, and miR-195-5p were exclusively downregulated in PDAC tissue but not in chronic pancreatitis or normal pancreatic tissues; both control types presented similar levels. We also identified miR-29a-3p, miR-29b-3p, and miR-7-5p as downregulated miRNAs in PDAC tissues as compared with normal tissues but not with pancreatitis tissues. Conclusions: We identified a panel of miRNAs that could represent putative therapeutic targets for the development of new miRNA-based therapies for PDAC.

Arid5a Promotes Immune Evasion by Augmenting Tryptophan Metabolism and Chemokine Expression

The acquisition of mesenchymal traits leads to immune evasion in various cancers, but the underlying molecular mechanisms remain unclear. In this study, we found that the expression levels of AT-rich interaction domain-containing protein 5a (Arid5a), an RNA-binding protein, were substantially increased in mesenchymal tumor subtypes. The deletion of Arid5a in tumor cell lines enhanced antitumor immunity in immunocompetent mice, but not in immunodeficient mice, suggesting a role for Arid5a in immune evasion. Furthermore, an Arid5a-deficient tumor microenvironment was shown to have robust antitumor immunity, as manifested by suppressed infiltration of granulocytic myeloid-derived suppressor cells and regulatory T cells. In addition, infiltrated T cells were more cytotoxic and less exhausted. Mechanistically, Arid5a stabilized Ido1 and Ccl2 mRNAs and augmented their expression, resulting in enhanced tryptophan catabolism and an immunosuppressive tumor microenvironment. Thus, our findings demonstrate the role of Arid5a beyond inflammatory diseases and suggest Arid5a as a promising target for the treatment of immunotolerant malignant tumors.See related Spotlight by Van den Eynde, p. 854.

Tumor Microenvironment Uses a Reversible Reprogramming of Mesenchymal Stromal Cells to Mediate Pro-tumorigenic Effects

The role of mesenchymal stromal cells (MSCs) in the tumor microenvironment is well described. Available data support that MSCs display anticancer activities, and that their reprogramming by cancer cells in the tumor microenvironment induces their switch toward pro-tumorigenic activities. Here we discuss the recent evidence of pro-tumorigenic effects of stromal cells, in particular (i) MSC support to cancer cells through the metabolic reprogramming necessary to maintain their malignant behavior and stemness, and (ii) MSC role in cancer cell immunosenescence and in the establishment and maintenance of immunosuppression in the tumor microenvironment. We also discuss the mechanisms of tumor microenvironment mediated reprogramming of MSCs, including the effects of hypoxia, tumor stiffness, cancer-promoting cells, and tumor extracellular matrix. Finally, we summarize the emerging strategies for reprogramming tumor MSCs to reactivate anticancer functions of these stromal cells.

Emerging data supporting stromal cell therapeutic potential in cancer: reprogramming stromal cells of the tumor microenvironment for anti-cancer effects

After more than a decade of controversy on the role of stromal cells in the tumor microenvironment, the emerging data shed light on pro-tumorigenic and potential anti-cancer factors, as well as on the roots of the discrepancies. We discuss the pro-tumorigenic effects of stromal cells, considering the effects of tumor drivers like hypoxia and tumor stiffness on these cells, as well as stromal cell-mediated adiposity and immunosuppression in the tumor microenvironment, and cancer initiating cells' cellular senescence and adaptive metabolism. We summarize the emerging data supporting stromal cell therapeutic potential in cancer, discuss the possibility to reprogram stromal cells of the tumor microenvironment for anti-cancer effects, and explore some causes of discrepancies on the roles of stromal cells in cancer in the available literature.

Canonical BMP Signaling Executes Epithelial-Mesenchymal Transition Downstream of SNAIL1

Epithelial-mesenchymal transition (EMT) is a pivotal process in development and disease. In carcinogenesis, various signaling pathways are known to trigger EMT by inducing the expression of EMT transcription factors (EMT-TFs) like SNAIL1, ultimately promoting invasion, metastasis and chemoresistance. However, how EMT is executed downstream of EMT-TFs is incompletely understood. Here, using human colorectal cancer (CRC) and mammary cell line models of EMT, we demonstrate that SNAIL1 critically relies on bone morphogenetic protein (BMP) signaling for EMT execution. This activity requires the transcription factor SMAD4 common to BMP/TGFβ pathways, but is TGFβ signaling-independent. Further, we define a signature of BMP-dependent genes in the EMT-transcriptome, which orchestrate EMT-induced invasiveness, and are found to be regulated in human CRC transcriptomes and in developmental EMT processes. Collectively, our findings substantially augment the knowledge of mechanistic routes whereby EMT can be effectuated, which is relevant for the conceptual understanding and therapeutic targeting of EMT processes.

HMGA2 Antisense Long Non-coding RNAs as New Players in the Regulation of HMGA2 Expression and Pancreatic Cancer Promotion

Background: Natural antisense long non-coding RNAs (lncRNAs) are regulatory RNAs transcribed from the opposite strand of either protein coding or non-coding genes, able to modulate their own sense gene expression. Hence, their dysregulation can lead to pathologic processes. Cancer is a complex class of diseases determined by the aberrant expression of a variety of factors, among them, the oncofetal chromatin architectural proteins High Mobility Group A (HMGA) modulate several cancer hallmarks. Thus, we decided to investigate the presence of natural antisense lncRNAs in HMGA1 and HMGA2 loci, and their possible involvement in gene expression regulation. Methods: We used FANTOM5 data resources, FANTOM-CAT genome browser and Zenbu visualization tool, which employ 1,829 human CAGE and RNA-sequencing libraries, to determine expression, ontology enrichment, and dynamic regulation of natural antisense lncRNAs in HMGA1 and HMGA2 loci. We then performed qRT-PCR in different cancer cell lines to validate the existence of HMGA2-AS1 transcripts. We depleted HMGA2-AS1 transcripts with siRNAs and investigated HMGA2 expression by qRT-PCR and western blot analyses. Moreover, we evaluated cell viability and migration by MTS and transwell assays, and EMT markers by qRT-PCR and immunofluorescence. Furthermore, we used bioinformatics approaches to evaluate HMGA2 and HMGA2-AS1 correlation and overall survival in tumor patients. Results: We found the presence of a promoter-associated lncRNA (CATG00000088127.1) in the HMGA1 gene and three antisense genes (RPSAP52, HMGA2-AS1, and RP11-366L20.3) in the HMGA2 gene. We studied the uncharacterized HMGA2-AS1 transcripts, validating their existence in cancer cell lines and observing a positive correlation between HMGA2 and HMGA2-AS1 expression in a cancer-derived patient dataset. We showed that HMGA2-AS1 transcripts positively modulate HMGA2 expression and migration properties of PANC1 cells through HMGA2. In addition, Kaplan-Meier analysis showed that high level of HMGA2-AS1 is a negative prognostic factor in pancreatic cancer patients. Conclusions: Our results describe novel antisense lncRNAs associated with HMGA1 and HMGA2 genes. In particular, we demonstrate that HMGA2-AS1 is involved in the regulation of its own sense gene expression, mediating tumorigenesis. Thus, we highlight a new layer of complexity in the regulation of HMGA2 expression, providing new potential targets for cancer therapy.