The methyltransferase like 3 (METTL3) is a key component of the large N6-adenosine-methyltransferase complex in mammalian responsible for N6-methyladenosine (m6A) modification in diverse RNAs including mRNA, tRNA, rRNA, small nuclear RNA, microRNA precursor and long non-coding RNA. However, the characteristics of METTL3 in activation and post-translational modification (PTM) is seldom understood. Here we find that METTL3 is modified by SUMO1 mainly at lysine residues K177, K211, K212 and K215, which can be reduced by an SUMO1-specific protease SENP1. SUMOylation of METTL3 does not alter its stability, localization and interaction with METTL14 and WTAP, but significantly represses its m6A methytransferase activity resulting in the decrease of m6A levels in mRNAs. Consistently with this, the abundance of m6A in mRNAs is increased with re-expression of the mutant METTL3-4KR compared to that of wild-type METTL3 in human non-small cell lung carcinoma (NSCLC) cell line H1299-shMETTL3, in which endogenous METTL3 was knockdown. The alternation of m6A in mRNAs and subsequently change of gene expression profiles, which are mediated by SUMOylation of METTL3, may directly influence the soft-agar colony formation and xenografted tumor growth of H1299 cells. Our results uncover an important mechanism for SUMOylation of METTL3 regulating its m6A RNA methyltransferase activity.

The purpose of this study was to investigate the clinical, pathological, and prognostic characteristics of breast cancer patients with diabetes. In total, the study included 1,013 breast cancer patients with diabetes and 4,621 breast cancer patients without diabetes. Patients with diabetes were further divided into the metformin- and nonmetformin-treated subgroups. The percentage of elderly patients (P < 0.001), obese patients (P < 0.001), and menopausal patients (P < 0.001) as well as the percentage of patients with cardio-cerebrovascular complications (P < 0.001), negative PR (P < 0.001) expression, or low Ki67 expression (P = 0.001) tended to be higher in the diabetic group. In addition, these patients had later pathological stages (P < 0.001), more lymph node metastasis (P = 0.014), and a lower percentage of them were on the anthracycline-based chemotherapy regimen (P = 0.003). The diabetic group was further divided into the metformin and nonmetformin-treated subgroups. The pairwise comparison between the metformin-treated subgroup and the control group did not show a significant difference in the pathological stages (P = 0.0079). However, the HER-2 positive rate tended to be lower in the metformin-treated subgroup than in the nonmetformin-treated subgroup (P = 0.002). No significant difference was found in the lymph node status between the nonmetformin-treated subgroup and the control group (P = 0.057), while the nonmetformin-treated subgroup was associated with higher HER-2 positive expression (P = 0.002). The median follow-up time for this study was 68 months (10-120 months). In Kaplan-Meier analysis, The diabetic group predicted worse survival compared with the control group (P < 0.001) with 5-year survival rates of 79 and 82 %, respectively. The breast cancer mortality rates in the metformin-treated subgroup, the nonmetformin-treated subgroup, and the control group were significantly different (long-rank test, P < 0.001), and the 5-year survival rates were 88, 73, and 82 %, respectively. As shown in the multivariate survival analysis using Cox's regression model, compared with the control group, the metformin-treated subgroup was associated with lower mortality risk (HR 0.762; 95 % CI 0.6-0.968; P = 0.026), whereas the nonmetformin-treated subgroup was associated with higher mortality risk (HR 1.708; 95 % CI 1.461-1.997; P < 0.001). In conclusion, the diabetic group is associated with poor prognosis. Compared with the control group, the metformin-treated subgroup is associated with better clinical outcomes, while nonmetformin-treated subgroup with poorer prognosis. The selection of different antidiabetic drugs may impact the prognosis of breast cancer patients with diabetes.

N 6-Methyladenosine (m6A) is the most abundant modification within diverse RNAs including mRNAs and lncRNAs and is regulated by a reversible process with important biological functions. Human YTH domain family 2 (YTHDF2) selectively recognized m6A-RNAs to regulate degradation. However, the possible regulation of YTHDF2 by protein post-translational modification remains unknown. Here, we show that YTHDF2 is SUMOylated in vivo and in vitro at the major site of K571, which can be induced by hypoxia while reduced by oxidative stress and SUMOylation inhibitors. SUMOylation of YTHDF2 has little impact on its ubiquitination and localization, but significantly increases its binding affinity of m6A-modified mRNAs and subsequently results in deregulated gene expressions which accounts for cancer progression. Moreover, Disease-free survival analysis of patients with lung adenocarcinoma derived from TCGA dataset reveals that higher expression of YTHDF2 together with higher expression of SUMO1 predicts poor prognosis. Our works uncover a new regulatory mechanism for YTHDF2 recognition of m6A-RNAs and highlight the importance of YTHDF2 SUMOylation in post-transcriptional gene expression regulation and cancer progression.

This study selected luminal-type breast cancer patients as the study subjects. The patients were divided into groups according to the presence of diabetes and the types of medication used, and the patients' clinicopathological characteristics and prognostic indicators were explored. A total of 5,785 patients with luminal-type breast cancer admitted to Tianjin Medical University Cancer Institute and Hospital between January 2002 and December 2006 were selected as the study subjects. The subjects included 680 breast cancer patients with diabetes and 5,105 breast cancer patients without diabetes. The patients were divided into Luminal A, Luminal B (high ki67), and Luminal B (her-2/neu+) subtypes. Each subtype was further divided into a metformin group, a non-metformin group, and a nondiabetic group. The research indicators included breast cancer mortality, age, body mass index (BMI), amenorrhea, the presence of cardiovascular and cerebrovascular disease, pathological stage, pathological type, lymph node involvement, vessel carcinoma embolus, and the chemotherapy and endocrine regimen. A Kaplan-Meier analysis was conducted to analyze the differences in breast cancer mortality rates among the groups. The Cox proportional hazard model was adopted to detect independent factors related to prognosis. Kaplan-Meier univariate analysis showed that for the Luminal A, Luminal B (high ki67), and Luminal B (her-2/neu+) subtypes, the cancer-specific mortality rates differed significantly among the metformin, non-metformin, and nondiabetic groups. The 5-year survival rates were 94%, 82%, and 91% (P = 0.002); 93.5%, 81%, and 89% (P < 0.001); and 84%, 77%, and 83% (P = 0.035) for the subtypes within each group, respectively. Cox regression multivariate analysis showed that compared with the metformin group, all three subtypes of the, the non-metformin group showed poorer prognosis (hazard ratio [HR], 3.579; 95% confidence interval [CI], 1.506-8.506 [P = 0.004]; HR, 3.232; 95% CI, 1.839-5.678 [P < 0.001]; HR, 2.034; 95% CI,1.019-4.059 [P = 0.044] for Luminal A, Luminal B (high ki67), and Luminal B (her-2/neu+, respectively). Compared with the metformin group, the diabetic group showed poorer prognosis only for the Luminal B (high ki67) subtype (HR, 1.762; 95% CI, 1.033-3.005 [P = 0.038]). In addition, for the Luminal A, Luminal B (high ki67), and Luminal B (her-2/neu+) subgroups, there was a higher proportion of elderly patients (P < 0.001) and postmenopausal patients (P < 0.001) in the metformin and non-metformin groups than in the nondiabetic group. Moreover, the probability of having cardiovascular and cerebrovascular disease was also higher (P < 0.001) in the metformin and non-metformin groups. For the Luminal B (high ki67) and Luminal B (her-2/neu +) subgroups, there was a higher proportion of obese patients in the metformin and non-metformin groups (P < 0.001). In terms of clinical characteristics, for the Luminal B (high ki67) subtype, the proportion of patients with invasive ductal carcinoma was lower in the non-metformin gro...

Prostate cancer (PCa) is the second leading cause of cancer-related deaths in north American men, and most its related deaths are due to advanced and metastatic PCa. However, the molecular mechanisms underlying PCa progression are still unclear. Here we use a pair of prostate cell lines P69/M12, which have the same genetic background and the highly metastatic cell line M12 is a subline derived from P69, to identify the pathogenesis of PCa. We find that a key miRNA--miR186 is significantly reduced in M12 compared to that in P69. Further, we validate that miR186 is also downregulated in human PCa specimens, most significantly in the metastatic patient specimens. The low miR186 expression is correlated with poor patient survival. Through knockdown or overexpression of miR186 in PCa cell lines, we discover that miR186 strongly inhibits cell motility, invasive, soft-agar colony formation, 3D culture growth and vasculogenic mimicry (VM) formation capacity, as well as the epithelial-to-mesenchymal transition (EMT) process by downregulation of its target Twist1. Moreover, the inverse relationship between the expression levels of miR186 and Twist1 is confirmed in vivo tumor metastasis experiment and clinical specimens. Taken together, our findings demonstrate an important role of miR186/Twist1 axis in the regulation of PCa progression, suggesting a potential application of miR186/Twist1 in PCa treatment.

Pancreatic cancer (PC) is a highly aggressive tumor, often difficult to diagnose and treat. Aspartate β-hydroxylase (ASPH) is a type II transmembrane protein and the member of α-ketoglutarate-dependent dioxygenase family, found to be overexpressed in different cancer types, including PC. ASPH appears to be involved in the regulation of proliferation, invasion and metastasis of PC cells through multiple signaling pathways, suggesting its role as a tumor biomarker and therapeutic target. In this review, we briefly summarize the possible mechanisms of action of ASPH in PC and recent progress in the therapeutic approaches targeting ASPH.

BackgroundMicroRNAs (miRNAs) are important regulators involved in diverse physiological and pathological processes including cancer. SUMO (small ubiquitin-like modifier) is a reversible protein modifier. We recently found that SUMOylation of TARBP2 and DGCR8 is involved in the regulation of the miRNA pathway. KHSRP is a single stranded nucleic acid binding protein with roles in transcription and mRNA decay, and it is also a component of the Drosha-DGCR8 complex promoting the miRNA biogenesis.MethodsThe in vivo SUMOylation assay using the Ni2+-NTA affinity pulldown or immunoprecipitation (IP) and the in vitro E.coli-based SUMOylation assay were used to analyze SUMOylation of KHSRP. Nuclear/Cytosol fractionation assay and immunofluorescent staining were used to observe the localization of KHSRP. High-throughput miRNA sequencing, quantantive RT-PCR and RNA immunoprecipitation assay (RIP) were employed to determine the effects of KHSRP SUMO1 modification on the miRNA biogenesis. The soft-agar colony formation, migration, vasculogenic mimicry (VM) and three-dimensional (3D) cell culture assays were performed to detect the phenotypes of tumor cells in vitro, and the xenograft tumor model in mice was conducted to verify that SUMO1 modification of KHSRP regulated tumorigenesis in vivo.ResultsKHSRP is modified by SUMO1 at the major site K87, and this modification can be increased upon the microenvironmental hypoxia while reduced by the treatment with growth factors. SUMO1 modification of KHSRP inhibits its interaction with the pri-miRNA/Drosha-DGCR8 complex and probably increases its translocation from the nucleus to the cytoplasm. Consequently, SUMO1 modification of KHSRP impairs the processing step of pre-miRNAs from pri-miRNAs which especially harbor short G-rich stretches in their terminal loops (TL), resulting in the downregulation of a subset of TL-G-Rich miRNAs such as let-7 family and consequential tumorigenesis.ConclusionsOur data demonstrate how the miRNA biogenesis pathway is connected to tumorigenesis and cancer progression through the reversible SUMO1 modification of KHSRP.Electronic supplementary materialThe online version of this article (10.1186/s12943-017-0724-6) contains supplementary material, which is available to authorized users.

This study evaluated the effects of an mTOR inhibitor everolimus alone or in combination with letrozole on MCF-7/Aro (MCF-7 cells stably transfected with CYP19) in vitro and in vivo. In vitro studies, full-length CYP19 (aromatase) was cloned in a plasmid transfer vector pH ß-Aro and then transfected into MCF-7 stem cells which were ESA(+)CD44(+)CD24(-/low) sorted by flow cytometry. MTT assays were used to quantify the inhibitory effect of the drugs on MCF-7/Aro stem cells (SCs) and non-stem cells (NSCs). Apoptosis and the cell cycle distributions of stem cells were examined by flow cytometry. The tumorigenicity of stem cells after treatment was investigated by soft agar colony formation assays. In vivo studies, the BALB/c mice were injected with MCF-7/Aro SCs, and the different treatments were administered. After necropsy, the expression of KI67, CD31, AKT1, phospho-AKT (Thr308), and mTOR was analyzed by immunohistochemistry. In vitro, compared with MCF-7/Aro NSCs, there were greater resistance to the standard treatment doses of letrozole and everolimus in MCF-7/Aro SCs (17- and 15-fold, respectively). Treatment with everolimus or letrozole resulted in growth inhibition of SCs in a dose-dependent manner. Compared with single-agent therapy, the combination of everolimus with letrozole was more effective in the inhibition of cell growth (P < 0.001) and tumorigenicity (P < 0.01). In addition, an increase in G1 cell cycle arrest and increases in early apoptosis were observed in the combination treatment group compared with either single-agent group. In vivo, the xenograft tumor sizes were significantly decreased in everolimus alone group compared to control group, and everolimus plus letrozole therapy was much more effective compared with either single agent alone (P < 0.01). Compared with everolimus alone, the combination of everolimus and letrozole reduced the expression of KI67, mTOR, and phospho-AKT (Thr308; P < 0.01). Everolimus has effective inhibition on aromatase-overexpressing stem cell in vitro and in vivo. The combination everolimus and letrozole could be more effective than either drug alone.