PRMT6 promotes endometrial cancer via AKT/mTOR signaling and indicates poor prognosis
Introduction
Endometrial cancer (EMC), representing the most common pelvic gynecological malignancy in industrialized countries, ranks the fourth most common malignancy among women in the United States. In 2017, 61,380 newly diagnosed cases and 10,920 EMC-related deaths were estimated (Bray et al., 2018). The mortality of EMC is much higher than that of cervical and ovarian cancers (Siegel et al., 2017). The 5-year survival rate is over 95 % for patients diagnosed at early stage, but decreases to 68 % and 17 % for patients with regional spread and distant metastasis, respectively (Colombo et al., 2016). Historically, EMC is classified into two main clinicopathological types: Type I is the much more common endometrioid adenocarcinoma (80–90 %) and Type II comprises non-endometrioid subtypes such as serous, clear cell and undifferentiated carcinomas, as well as carcinosarcoma/malignant-mixed Müllerian tumor (10–20 %) (Halkia et al., 2012). In China, most of EMC patients are diagnosed with advanced-stage and high-grade tumors that spread beyond the uterus and experience tumor progression within 1 year (He et al., 2018). To date, surgery is the primary option for the early-stage patients and chemotherapy is used to treat advanced and recurrent patients. However, tumor heterogeneity and chemoresistance are major obstacles in EMC therapy. As a result, it is essential to obtain more information that would be helpful in understanding the biological underpinnings of tumor progression to generate promising strategies for the clinical management of EMC.
Post-translational modification participates in essential biological processes, such as signal transduction and cell fate decision. Arginine methylation plays important roles in DNA repair, alternative splicing and RNA metabolism that are involved in the initial and progression in human diseases (Blanc and Richard, 2017). Protein arginine methyltransferases (PRMTs), including nine members, consists of two groups (type I and II). Type I PRMTs (PRMT1, 2, 3, 4, 6, and 8) are responsible for asymmetric dimethylarginine (ADMA), while type II PRMTs (PRMT5 and 7) generates symmetric dimethylarginine (SDMA) (Bedford and Clarke, 2009). Specifically, PRMT6, lying on chromosome 1p13.3, transfers methyl from S-adenosylmethionine to guanidino nitrogen to produce asymmetrical dimethylated arginine (Hamamoto and Nakamura, 2016). PRMT6 is the major PRMT responsible for histone H3R2 methylation and is universally expressed in human normal tissues (Bedford and Clarke, 2009). During neural differentiation, PRMT6 interacts with polycomb repressive complex (PRC) subunits, such as CBX8 and EZH2, to repress the differentiation-associated transcriptional activation of rostral HOXA genes (Stein et al., 2016). In human cancer cells, PRMT6 is differently expressed. Decreased PRMT6 expression has been reported in melanoma (Limm et al., 2013) and hepatocellular carcinoma (Chan et al., 2018), whereas increased expression of PRMT6 is found in lung (Bouchard et al., 2018), breast (Kim et al., 2013), gastric (Okuno et al., 2019) and prostate (Almeida-Rios et al., 2016) cancers. Therefore, the biological function of PRMT6 in human cancers may be contradictory, dependent on the cellular content.
In this study, we intended to examine the expression of PRMT6 and its clinical significance in EMC, and to investigate its role in the progression of EMC. Our data show that PRMT6 is overexpressed and correlates with poor outcomes, and that PRMT6 exhibits oncogenic activity via AKT/mTOR signaling pathway.
Section snippets
Patients
Twenty-eight fresh EMC specimens were collected for determination of mRNA and protein levels of PRMT6 in The First Affiliated Hospital of Sun Yat-sen University (FAHSYSU) and The Affiliated Hexian Memorial Hospital of Southern Medical University. A total of 232 paraffin-embedded EMC cases diagnosed between Jan 2010 to Dec 2012 at FAHSYSU was recruited (known as FAHSYSU cohort) to examine the expression and clinical significance of PRMT6. None of the patients had received radiotherapy or
PRMT6 expression is increased and correlated with poor outcomes in EMC
TCGA data showed that genomic alterations frequently occurred in PRMT members (Supplementary Fig. 1A). Current literatures reported that PRMT6 was differently expressed in human cancers (Supplementary Fig. 1B). In this study, we first intended to investigate the expression of PRMT6 and its clinical significance in EMC. Using qRT-PCR and western blot, the mRNA and protein levels of PRMT6 were determined in 28 pairs of fresh EMC tissues and the corresponding adjacent endometrium tissues
Discussion
EMC represents one of the life risks that cause plenty of death in women (Siegel et al., 2017). Although literatures have unveiled aberrant signaling pathways that contribute to EMC progression, the molecular mechanism of EMC invasion and metastasis remain unclear. In the present study, we present data that PRMT6 expression is upregulated in clinical samples and correlates with unfavorable outcomes. in vitro and in vivo data demonstrate that PRMT6 exerts oncogenic activity to promote cell
Data availability statement
Data sharing is not applicable to this article as no new data were created or analyzed in this study.
Declaration of Competing Interest
All authors declare no conflict of interest.
CRediT authorship contribution statement
Nan Jiang: Conceptualization, Data curation, Writing - review & editing. Qiu-Li Li: Data curation, Methodology, Resources. Wenwei Pan: Data curation, Methodology. Jinhui Li: Data curation. Mei-Fang Zhang: Data curation. Tiefeng Cao: Data curation. Shu-Guang Su: Conceptualization, Supervision, Writing - review & editing. Huimin Shen: Conceptualization, Supervision, Writing - review & editing.
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These authors contributed equally to this work.