AHNAK2 Promotes the Progression of Pancreatic Ductal Adenocarcinoma by Maintaining the Stability of c-MET.

Purpose: Pancreatic ductal adenocarcinoma (PDAC) is extremely malignant and rapidly progresses. The overall response rate of PDAC to current treatment methods is still unsatisfactory. Thus, identifying novel targets and clarifying the underlying mechanisms associated with PDAC progression may potentially offer additional treatment strategies. AHNAK2 is aberrantly expressed in a variety of tumors and exerts pro-tumorigenic effects. However, the biological role of AHNAK2 in PDAC remains poorly understood. Methods: The expression of AHNAK2 in PDAC and paired non-tumor tissues was detected by immunohistochemistry (IHC) and quantitative real-time polymerase chain reaction (qRT-PCR). Lentivirus knockdown was performed to investigate the impact of AHNAK2 on the biological function of pancreatic cancer cells. The subcutaneous cell-derived xenograft (CDX) model and the KPC spontaneous mouse model with AHNAK2 silencing were used to observe the effects of AHNAK2 on tumor growth and prognosis. The expression of c-MET at protein level in response to HGF treatment was assessed using western blot. Results: Our results demonstrated that AHNAK2 was highly expressed in PDAC clinical samples and associated with poor prognosis. Knockdown of AHNAK2 significantly inhibited the proliferation, migration, and invasion of pancreatic cancer cells. AHNAK2 knockdown or knockout resulted in tumor growth suppression and prolonged survival in mice with PDAC. In addition, AHNAK2 and c-MET expression levels showed a significant positive correlation at the post-transcriptional level. Mechanistically, AHNAK2 promoted tumor progression by preventing c-MET degradation and persistently activating the HGF/c-MET signaling pathway. Conclusion: Overall, our study revealed that AHNAK2 plays an important role in PDAC progression by modulating the c-MET signaling pathway, and targeting AHNAK2 may be an effective therapeutic strategy for PDAC.

circCUL2 induces an inflammatory CAF phenotype in pancreatic ductal adenocarcinoma via the activation of the MyD88-dependent NF-κB signaling pathway.

BACKGROUND: Pancreatic ductal adenocarcinoma (PDAC) is characterized by clusters of cancer cells surrounded by a dense desmoplastic stroma. However, little is known about stromal cell heterogeneity in the pancreatic tumor microenvironment. METHODS: We conducted circRNA profiling in primary fibroblasts by high-throughput sequencing and detected circCUL2 levels in PDAC tissues by qRT-PCR. We subsequently investigated the effect of circCUL2 on inflammatory cancer-associated fibroblast (iCAF) activation, heterogeneity and protumor activity by ELISA, flow cytometry, colony formation and transwell assays in vitro and by xenograft models in vivo. The regulatory effect of circCUL2 on miR-203a-3p/MyD88/IL6 was examined by RNA pulldown, FISH, and luciferase reporter assays. RESULTS: We identified that circCUL2 was specifically expressed in cancer-associated fibroblasts (CAFs) but not in cancer cells. Moreover, the enrichment of circCUL2 in tumor tissues was significantly correlated with the poor prognosis of PDAC patients. Upregulation of circCUL2 expression in normal fibroblasts (NFs) induced the iCAF phenotype, and then iCAFs promoted PDAC progression through IL6 secretion in vitro. Furthermore, circCUL2-transduced NFs promoted tumorigenesis and metastasis of PDAC cells in vivo, which was blocked by an anti-IL6 antibody. Mechanistically, circCUL2 functioned as a ceRNA and modulated the miR-203a-3p/MyD88/NF-κB/IL6 axis, thereby further activating the STAT3 signaling pathway in pancreatic cancer cells to induce PDAC progression. CONCLUSIONS: We showed that the circCUL2/miR-203a-5p/MyD88/NF-κB/IL6 axis contributes to the induction of iCAFs and established a distinct fibroblast niche for PDAC progression, which could help the development of strategies that selectively target tumor-promoting CAFs in PDAC.

Cancer-associated fibroblast-induced lncRNA UPK1A-AS1 confers platinum resistance in pancreatic cancer via efficient double-strand break repair.

The tumor stroma of pancreatic ductal adenocarcinoma (PDAC) is characterized by an abundant and heterogeneous population of cancer-associated fibroblasts (CAFs), which are critically involved in chemoresistance. However, the underlying mechanism of CAFs in chemoresistance is unclear. Here, we show that CAFR, a CAF subset derived from platinum-resistant PDAC patients, assumes an iCAF phenotype and produces more IL8 than CAFS isolated from platinum-sensitive PDAC patients. CAFR-derived IL8 promotes oxaliplatin chemoresistance in PDAC. Based on long noncoding RNA (lncRNA) profiling in tumor cells incubated with CAF-CM, we found that UPK1A-AS1, whose expression is directly induced by IL8/NF-kappa B signaling, functions as a chemoresistance-promoting lncRNA and is critical for active IL8-induced oxaliplatin resistance. Impressively, blocking the activation of UPK1A-AS1 expression increases the oxaliplatin sensitivity of tumor cells in vivo. Mechanistically, UPK1A-AS1 strengthens the interaction between Ku70 and Ku80 to facilitate nonhomologous end joining (NHEJ), thereby enhancing DNA double-strand break (DSB) repair. Clinically, UPK1A-AS1 expression is positively correlated with IL8 expression, a poor chemotherapeutic response and a shorter progression-free survival (PFS) time in advanced PDAC patients. Collectively, our study reveals a lncRNA-mediated mechanism of CAF-derived paracrine IL8-dependent oxaliplatin resistance and highlights UPK1A-AS1 as a potential therapeutic target.

A novel gene signature for prognosis prediction and chemotherapy response in patients with pancreatic cancer.

Pancreatic cancer is a lethal disease. Chemoresistance is one of the characteristics of pancreatic cancer and leads to a poor prognosis. This study built an effective predictive model for personalized treatment and explored the molecular mechanism of chemoresistance. A four-gene signature, including serine peptidase inhibitor Kazal type 1 (SPINK1), anoctamin 1 (ANO1), desmoglein 3 (DSG3) and GTPase, IMAP family member 1 (GIMAP1) was identified and associated with prognosis and chemoresistance in the training group. An internal testing dataset and the external dataset, GSE57495, were used for validation and showed a good performance of the gene signature. The high-risk group was enriched with multiple oncological pathways related to immunosuppression and was correlated with epidermal growth factor receptor (EGFR) expression, a target molecule of Erlotinib. In conclusion, this study identified a four-gene signature and established two nomograms for predicting prognosis and chemotherapy responses in patients with pancreatic cancer. The clinical value of the nomogram was evaluated by decision curve analysis (DCA). It showed that these may be helpful for clinical treatment decision-making and the discovery of the potential molecular mechanism and therapy targets for pancreatic cancer.