LncRNA CCAT1 participates in pancreatic ductal adenocarcinoma progression by forming a positive feedback loop with c-Myc.

Long noncoding RNAs (lncRNAs) play fundamental roles in cancer development; however, the underlying mechanisms for a large proportion of lncRNAs in pancreatic ductal adenocarcinoma (PDAC) have not been elucidated. The expression of colon cancer-associated transcript-1 (CCAT1) in PDAC specimens and cell lines was measured by quantitative real-time polymerase chain reaction (qRT-PCR). The function of CCAT1 was examined in vitro and in vivo. The interactions among CCAT1, miR-24-3p and c-Myc were determined by bioinformatics analysis, RNA immunoprecipitation (RIP), dual-luciferase reporter assay, and rescue experiments. CCAT1 was significantly increased in PDAC, positively correlated with PDAC progression and predicted a worse prognosis. Furthermore, CCAT1 enhanced Adenosine triphosphate (ATP) production to facilitate PDAC cell proliferation, colony formation and motility in vitro and tumor growth in vivo. CCAT1 may serve as an miR-24-3p sponge, thereby counteracting its repression by c-Myc expression. Reciprocally, c-Myc may act as a transcription factor to alter CCAT1 expression by directly targeting its promoter region, thus forming a positive feedback loop with CCAT1. Collectively, these results demonstrate that a positive feedback loop of CCAT1/miR-24-3p/c-Myc is involved in PDAC development, which may serve as a biomarker and therapeutic target for PDAC.

circEIF3I facilitates the recruitment of SMAD3 to early endosomes to promote TGF-ß signalling pathway-mediated activation of MMPs in pancreatic cancer.

BACKGROUND: Among digestive tract tumours, pancreatic ductal adenocarcinoma (PDAC) shows the highest mortality trend. Moreover, although PDAC metastasis remains a leading cause of cancer-related deaths, the biological mechanism is poorly understood. Recent evidence demonstrates that circular RNAs (circRNAs) play important roles in PDAC progression. METHODS: Differentially expressed circRNAs in normal and PDAC tissues were screened via bioinformatics analysis. Sanger sequencing, RNase R and actinomycin D assays were performed to confirm the loop structure of circEIF3I. In vitro and in vivo functional experiments were conducted to assess the role of circEIF3I in PDAC. MS2-tagged RNA affinity purification, mass spectrometry, RNA immunoprecipitation, RNA pull-down assay, fluorescence in situ hybridization, immunofluorescence and RNA-protein interaction simulation and analysis were performed to identify circEIF3I-interacting proteins. The effects of circEIF3I on the interactions of SMAD3 with TGFßRI or AP2A1 were measured through co-immunoprecipitation and western blotting. RESULTS: A microarray data analysis showed that circEIF3I was highly expressed in PDAC cells and correlated with TNM stage and poor prognosis. Functional experiments in vitro and in vivo revealed that circEIF3I accelerated PDAC cells migration, invasion and metastasis by increasing MMPs expression and activity. Mechanistic research indicated that circEIF3I binds to the MH2 domain of SMAD3 and increases SMAD3 phosphorylation by strengthening the interactions between SMAD3 and TGFßRI on early endosomes. Moreover, AP2A1 binds with circEIF3I directly and promotes circEIF3I-bound SMAD3 recruitment to TGFßRI on early endosomes. Finally, we found that circEif3i exerts biological functions in mice similar to those of circEIF3I in humans PDAC. CONCLUSIONS: Our study reveals that circEIF3I promotes pancreatic cancer progression. circEIF3I is a molecular scaffold that interacts with SMAD3 and AP2A1 to form a ternary complex, that facilitates the recruitment of SMAD3 to early endosomes and then activates the TGF-ß signalling pathway. Hence, circEIF3I is a potential prognostic biomarker and therapeutic target in PDAC.

Positive feedback regulation of lncRNA TPT1-AS1 and ITGB3 promotes cell growth and metastasis in pancreatic cancer.

Emerging evidence has indicated that long noncoding RNAs (lncRNAs) are potential biomarkers and play crucial roles in cancer development. However, the functions and underlying mechanisms of lncRNA TPT1-AS1 in pancreatic ductal adenocarcinoma (PDAC) remain elusive. RNAseq data of PDAC tissues and normal tissues were analyzed, and lncRNAs which were associated with PDAC prognosis were identified. The clinical relevance of TPT1-AS1 for PDAC patients was explored, and the effects of TPT1-AS1 in PDAC progression were investigated in vitro and in vivo. LncRNA TPT1-AS1 was highly expressed in PDAC, and high TPT1-AS1 levels predicted a poor prognosis. Moreover, functional experiments revealed that TPT1-AS1 promoted pancreatic cancer cell proliferation, migration, invasion, and epithelial-to-mesenchymal transition (EMT) process in vitro and in vivo. Mechanistically, TPT1-AS1 functioned as an endogenous sponge for miR-30a-5p, which increased integrin ß3 (ITGB3) level in pancreatic cancer cells. Conversely, our data revealed that ITGB3 could activate the transcription factor signal transducer and activator of transcription 3 (STAT3), which in turn bound directly to the TPT1-AS1 promoter and affected the expression of TPT1-AS1, thus forming a positive feedback loop with TPT1-AS1. Taken together, our results uncovered a reciprocal loop of TPT1-AS1 and ITGB3 which contributed to pancreatic cancer growth and development, and indicated that TPT1-AS1 might serve as a novel potential diagnostic biomarker and therapeutic target for PDAC patients.

ANXA3-Rich Exosomes Derived from Tumor-Associated Macrophages Regulate Ferroptosis and Lymphatic Metastasis of Laryngeal Squamous Cell Carcinoma.

Tumor-associated macrophages (TAM) induce immunosuppression in laryngeal squamous cell carcinoma (LSCC). The interaction between LSCC cells and TAMs affects the progression of laryngeal cancer through exosomes, but the underlying molecular mechanism remains unclear. Proteomics analysis of TAMs isolated from human laryngeal tumor tissues obtained from patients with confirmed lymphatic metastasis revealed an upregulation of annexin A3 (ANXA3). In TAMs, ANXA3 promoted macrophages to polarize to an M2-like phenotype by activating the AKT-GSK3ß-ß-catenin pathway. In addition, ANXA3-rich exosomes derived from TAMs inhibited ferroptosis in laryngeal cancer cells through an ATF2-CHAC1 axis, and this process was associated with lymphatic metastasis. Mechanistically, ANXA3 in exosomes inhibited the ubiquitination of ATF2, whereas ATF2 acted as a transcription factor to regulate the expression of CHAC1, thus inhibiting ferroptosis in LSCC cells. These data indicate that abnormal ANXA3 expression can drive TAM reprogramming and promote an immunosuppressive microenvironment in LSCC. Meanwhile, ANXA3-rich exosomes inhibit ferroptosis of LSCC cells and promote lymphatic metastasis, thus promoting tumor progression.

The Prognostic and Immune Significance of CILP2 in Pan-Cancer and Its Relationship with the Progression of Pancreatic Cancer.

Cartilage intermediate layer protein 2 (CILP2) facilitates interactions between matrix components in cartilage and has emerged as a potential prognostic biomarker for cancer. This study aimed to investigate the function and mechanisms of CILP2 in pan-cancer. We evaluated the pan-cancer expression, methylation, and mutation data of CILP2 for its clinical prognostic value. Additionally, we explored the immunological characteristics of CILP2 in pan-cancer and then focused specifically on pancreatic ductal adenocarcinoma (PAAD). The subtype analysis of PAAD identified subtype-specific expression and immunological characteristics. Finally, in vitro and in vivo experiments assessed the impact of CILP2 on pancreatic cancer progression. CILP2 exhibited high expression in most malignancies, with significant heterogeneity in epigenetic modifications across multiple cancer types. The abnormal methylation and copy number variations in CILP2 were correlated with poor prognoses. Upregulated CILP2 was associated with TGFB/TGFBR1 and more malignant subtypes. CILP2 exhibited a negative correlation with immune checkpoints in PAAD, suggesting potential for immunotherapy. CILP2 activated the AKT pathway, and it increased proliferation, invasion, migration, and epithelial-mesenchymal transition (EMT) in pancreatic cancer. We demonstrated that CILP2 significantly contributes to pancreatic cancer progression. It serves as a prognostic biomarker and a potential target for immunotherapy.

DUSP2 recruits CSNK2A1 to suppress AKT1-mediated apoptosis resistance under hypoxic microenvironment in pancreatic cancer.

Pancreatic ductal adenocarcinoma (PDAC) is characterized by hypoxic tumor microenvironment (TME), which aids tumor progression, drug resistance, and immune evasion. Dual-specificity phosphatase 2 (DUSP2), a member of the mitogen-activated protein kinase phosphatase family, regulates pancreatic cancer metastasis. However, its role in the hypoxic TME in PDAC remains unknown. We explored the role of DUSP2 by simulating the hypoxic TME. DUSP2 significantly promoted apoptosis in PDAC both in vitro and in vivo, mainly through AKT1 rather than ERK1/2. Mechanistically, DUSP2 competed with AKT1 to bind to casein kinase 2 alpha 1 (CSNK2A1) and inhibited the phosphorylation of AKT1, which plays a crucial role in apoptosis resistance. Interestingly, aberrant activation of AKT1 resulted in an increase in the ubiquitin E3 ligase tripartite motif-containing 21 (TRIM21), which binds to and mediates the ubiquitination-dependent proteasomal degradation of DUSP2. Overall, we identified CSNK2A1 as a novel binding partner of DUSP2 that promotes PDAC apoptosis through CSN2KA1/AKT1 in an ERK1/2-independent manner. Activation of AKT1 also mediated proteasomal degradation of DUSP2 via the AKT1/TRIM21 positive feedback loop. We propose increasing the level of DUSP2 as a potential therapeutic strategy for PDAC.

Tumor Cell Derived Lnc-FSD2-31:1 Contributes to Cancer-Associated Fibroblasts Activation in Pancreatic Ductal Adenocarcinoma Progression through Extracellular Vesicles Cargo MiR-4736.

Pancreatic ductal adenocarcinoma (PDAC) presents with high mortality and short overall survival. Cancer-associated fibroblasts (CAFs) act as refuge for cancer cells in PDAC. Mechanisms of intracelluar communication between CAFs and cancer cells need to be explored. Long noncoding RNAs (lncRNAs) are involved in the modulation of oncogenesis and tumor progression of PDAC; however, specific lncRNAs and their mechanism of action have not been clarified clearly in tumoral microenvironment. This work aims to identify novel lncRNAs involved in cellular interaction between cancer cells and CAFs in PDAC. To this end, differentially expressed lncRNAs between long-term and short-term survival PDAC patients are screened. Lnc-FSD2-31:1 is found to be significantly increased in long-term survival patients. This work then discovers that tumor-derived lnc-FSD2-31:1 restrains CAFs activation via miR-4736 transported by extracellular vesicles (EVs) in vitro and in vivo. Mechanistically, EVs-derived miR-4736 suppresses autophagy and contributes to CAFs activation by targeting ATG7. Furthermore, blocking miR-4736 suppresses tumor growth in genetically engineered KPC (LSL-KrasG12D/+, LSL-Trp53R172H/+, and Pdx-1-Cre) mouse model of PDAC. This study demonstrates that intratumoral lnc-FSD2-31:1 modulates autophagy in CAFs resulting in their activation through EVs-derived miR-4736. Targeting miR-4736 may be a potential biomarker and therapeutic target for PDAC.