Abstract
BackgroundPancreatic cancer is one of the most lethal types of cancer with extremely poor diagnosis and prognosis, and chemo-resistance remains a major challenge. The dynamic and reversible N6-methyladenosine (m6A) RNA modification has emerged as a new layer of epigenetic gene regulation.MethodsqRT-PCR and IHC were applied to examine ALKBH5 levels in normal and pancreatic cancer tissues. Cancer cell proliferation and chemo-resistance were evaluated by clonogenic formation, chemosensitivity detection, and Western blotting assays. m6A-seq was performed to identify target genes. We evaluated the inhibitory effect of ALKBH5 in both in vivo and in vitro models.ResultsHere, we show that m6A demethylase ALKBH5 is downregulated in gemcitabine-treated patient-derived xenograft (PDX) model and its overexpression sensitized pancreatic ductal adenocarcinoma (PDAC) cells to chemotherapy. Decreased ALKBH5 levels predicts poor clinical outcome in PDAC and multiple other cancers. Furthermore, silencing ALKBH5 remarkably increases PDAC cell proliferation, migration, and invasion both in vitro and in vivo, whereas its overexpression causes the opposite effects. Global m6A profile revealed altered expression of certain ALKBH5 target genes, including Wnt inhibitory factor 1 (WIF-1), which is correlated with WIF-1 transactivation and mediation of the Wnt pathway.ConclusionsOur work uncovers the tumor suppressive and chemo-sensitizing function for ALKBH5, which provides insight into critical roles of m6A methylation in PDAC.
Highlights
Pancreatic cancer is one of the most lethal types of cancer with extremely poor diagnosis and prognosis, and chemo-resistance remains a major challenge
Alkylation repair homolog protein 5 (ALKBH5) expression is downregulated in gemcitabinetreated patient-derived xenograft (PDX) pancreatic cancer Gemcitabine resistance usually develops within weeks of treatment initiations, which limits its overall efficacy as the first line chemotherapy in pancreatic ductal adenocarcinoma (PDAC) [19]
We found frequent deletion and downregulated expression of ALKBH5 in 2 Gene Expression Omnibus (GEO) datasets (GSE16515 and 106,901) of PDACs compared to their matched normal tissues (NT), which was validated by qRT-PCR analysis of matched tumor and adjacent tissues (Additional file 2: Figure S2a and Fig. 1e-g)
Summary
Pancreatic cancer is one of the most lethal types of cancer with extremely poor diagnosis and prognosis, and chemo-resistance remains a major challenge. Pancreatic cancer is one of the few malignancies with the mortality approaching the incidence, ranking the six and seventh leading cause of cancer death in China and worldwide, respectively [1,2,3] It caused an estimation of 458, 918 new cases and an associated 432,242 deaths globally in 2018 [4]. (2020) 19:3 primary microRNA processing, and RNA–protein interactions [7, 8] This modification is reversible and relies on the RNA methyltransferases (writers), the demethylases (erasers), and m6A-binding proteins (readers), which are frequently upregulated in a variety of human cancers and might play a crucial role in the process of carcinogenesis [7,8,9,10]. The exact role of ALKBH5 in tumorigenesis of pancreatic cancer deserves further investigation
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