Úloha epigenetiky pri rakovine endometria


Endometriálny adenokarcinóm, uvádzaný často aj ako rakovina endometria, je najčastejším druhom rakoviny ma- ternice. V posledných desaťročiach možno sledovať nárast jeho výskytu a každoročne sú desaťtisíce žien na celom svete diagnostikované jedným z dvoch typov rakoviny endometria. Známe je, že relatívne vyšší výskyt pozorujeme vo vyspelých krajinách sveta, najmä v štátoch Severnej Ameriky a strednej Európy. Táto nepríjemná štatistika je však tiež možnou príležitosťou pre tieto regióny študovať karcinogenézu a možné spôsoby, aké sú príčiny a dôsledky tejto malignity na bunkovej úrovni. Ako to býva pri multifaktoriálnych ochoreniach, postihnuté bunky prechádzajú nielen mnohými zmenami genetickej informácie, ale aj epigenetickými modifikáciami. Nie všetky by sa mali považovať za kritické pre onkologický proces, no aj sprievodné modifikácie v tkanivách ad- enokarcinómu môžu ovplyvniť vývoj malignity. Preto môže byť štúdium mutácií, epigenetických zmien v DNA, zmien v histónovom kóde alebo molekulách mikroRNA, prípadne narušených hormonálnych signálnych dráhach kľúčové pre pochopenie procesu karcinogenézy. Sprievodné zmeny s významnou mierou korelácie, aj keď nie sú rozhodujúce pre potenciálnu terapiu, môžu mať svoju úlohu pri vývoji nových klinicky relevantných nástrojov. V tomto článku podávame prehľad epigenetických zmien ovplyvňujúcich oba typy rakoviny endometria.

Kľúčové slová: karcinogenéza rakoviny endometria, epigenetika, rakovina endometria 2. typu, DNA metylácia, OncomiRs

*Všetky tabuľky, grafy a obrázky, ktoré sú súčasťou článku, nájdete v priloženom PDF súbore na konci štúdie.


Endometrial cancer (EC) is the second most common gynecologic cancer (after breast cancer) and seventh most common cancer worldwide among females(1,2). Regions of Central and eastern Europe had the second highest cumulative risk in both incidence (2,48%) and mortality (0,47%) in 2020. In estimated age-standardized incidence rates of all ages, Slovakia is ranked 15th of all countries (Table 1)(2). The full mechanisms of EC development remain unclear but there is growing number of molecules (hormones, proteins and RNAs) reported to have a role in carcinogenic process. Mutations in coding regions of functional molecules same as their regulation is crucial for EC development. In last decades, the research is getting more focused on epigenetic changes, such as hypermethylation, deacetylation of histones or RNA interference(1,3,4). The epigenetic modifications seems to be more frequent in EC that genetic changes, therefore they could potentially serve as a diagnostic tool(4).


Types of endometrial cancer and their differences

There are two types of EC differing in the body estrogen excess and the rate of spreading. Type 1 is more common (80% of cases), growing slower and linked to excess of estrogen. It occurs mostly among premenopausal and perimenopausal women. Type 2, on the other hand, is faster growing one, without apparent multistage process. It is not linked to excess estrogen in the body, mostly developing among postmenopausal women(5,6). Typical for type 1 EC is sequence of changes from normal endometrium, through hyperplasia, to precancerous lesion (Figure 1). The transition from stage-to-stage is believed to be accompanied with accumulation of mutations in oncogenes, tumor suppressor genes DNA maintenance genes and their regulators(6).


Molecular characterization of endometrioid tumors

One of the latest classifications is subtyping the endometrial tumors based on their molecular DNA background. Even though these molecular subgroups has not been implemented in clinical routine so far, studies confirm their prognostic relevance(7,8).

These four groups of carcinomas, independent on histological subtype, are POLE ultramutated (group 1), microsatellite instability (group 2), low-copy-number alterations (group 3), and high-copy-number alterations and TP53 mutations (group 4)(9,10).

The POLE mutated EC is characterised by pathogenic variants in the DNA polymerase-epsilon (POLE) exonuclease domain mostly in one of the five hot-spots: P286R, V411L, S297F, A456P and S459F. This group presents itself at the younger age of patient and has excellent prognosis(7,10). The second group is typically mismatch repair (MMR) deficient and the prognostic level is intermediate. The p53 mu- tant EC, in accordance with Type 2 classification, presents itself at late stage which corelates with its poor prognosis. The MMR-proficient, POLE and p53 wildtype group, often referred as NSMP EC (no specific molecular profile) has intermediate to excellent prognosis and is associated with higher body mass index(10).


The role of epigenetics – promotor methylation

The regulation of EC stage-to-stage transition could be provided by activity of DNA methyltransferases, particularly de novo DNA methyltransferases. Their modification of CpG rich regions (often found in promoter regions, first exons or terminal parts of genes coding untranslated regions) has a crucial role for gene expression. Changed methylation of the hMLH1 gene is considered one of the earliest steps in multistage endometrial carcinogenesis and is found in ~30 – 40% of cases(11,12). This gene encodes the homolog of bacterial DNA mismatch repair protein and the malfunctional expression of the gene (caused by hypermethylation) is associated with other cancer kinds(13-15). Kawaguchi et al.(16) reported that abnormalities in the mismatch repair genes (including hMLH1) leads to microsatellite instability which cascades into further mutations and increase in gene instability of other cancer related genes. Therefore, it has been recently pro- posed, in conformity with the recent group 1 – 4 subtyping, the MMR proteins and loss of MLH1 should be tested for promoter hypermethylation to evaluate its epigenetic mechanism. Subsequent POLE and p53 studies are also encouraged(8).

There is also strong correlation between estrogen lev- els and expression of hMLH1. MMR activity was increased in high estrogen conditions for in vitro cultivated endometrial epithelial cells. High estrogen levels could therefore protect from EC development(12). Cyclic production of estrogen and progesterone in menstruation cycle as well as decline of sex steroid hormone after menopause have direct effect on proliferation and morphology of endometrial tissue(3). Methylation of the estrogen and progesterone receptor genes were therefore studied in EC cells. They both contain a CpG region in the first exon, but its methylation level have been variable in recent studies, thus its effect is not yet fully understood(3).

During the atypical endometrial hyperplasia, the next stage of EC development, hypermethylation of APC promotor is likely to happen, since it is not methylated in normal endometrium, frequently hypermethylated in early cancer stages, but the methylation level is decreasing with an increase in the clinical stage(17). E-cadherin is tumor suppressor encoded by CDH1 gene, which promoter is also susceptible to hypermethylation. Decrease of its expression is not only sign of EC development but has an unfortunate 5-year clinical survival rate(18). Most known affected gene in type 1 EC is PTEN. It functions as tumor suppressor gene, regulating proliferation and apoptosis. Its mutation occurs in 26 – 80% of EC, either at development of atypical endometrial hyperplasia or at low grade endometrioid cancer, quite possibly as a consequence of MMR disfunction(3,6). There is a possibility, that this gene may be downregulated by hypermethylation, as well(19), although, its analysis of the methylation status is quite challenging, since it is 98% identical to PTEN pseudogene (psiPTEN)(20). The other methylation affected genes in EC development are regulators of proliferation (HOXA11, TGF-‑βRII), apoptosis (CASP8), hormone metabolism (COMT) or other tumor suppressors (RSK4, P73, RASSF1A). For specifics about their involvement in EC, see(1).

The type 2 EC have distinct methylation patterns. The promotors of many genes mentioned above (hMLH1, APC, PTEN, RASSF1A, progesterone receptor coding gene) are detected more frequently in type 1 tumors. Such findings indicates that the process of DNA methylation is predominant in type 1 EC and in type 2 it may have less significant role(3,21,22).


The role of epigenetics – microRNAs

Another way of epigenetic regulation in EC is via microRNA (miRNA) molecules. They may contribute via RNA-associated silencing, but their genes are also under epigenetic regulation. miRNAs are short (19 – 25 nt), noncoding, single-stranded RNA molecules produced by RNA polymerase II or III usually cleaved from primary transcripts by RNase III(4,23). Targeting of specific miRNA is not trivial since it is potentially able to regulate hundreds of genes and each transcript may be regulated by several miRNAs(24).

The epigenetic regulation of miRNA is occurring on several levels since their production is also regulated by methylation level CpG-rich domains. Favier et al.(4) have recently published a complex review for miRNAs with increased (n=140), decreased (n=148) and miRNAs with discordant expression (n=22) in EC from over 100 articles. Additionally, the complex review reports about miRNAs with changed methylation level, six hypomethylated mRNAs and nine hypermethylated ones. Unsurprisingly, the majority of hypermethylated miRNAs (miR-638, miR-137, miR-633, miR-34b, miR-124a-2, miR-124a-3, miR-152, miR- 129-2)(4,25-31) are tumor suppressors and the hypomethylated (miR-182, miR-200b, miR-130a/b, miR-625, miR-222, miR-208a)(4,29,32,33) are OncomiRs, the miRNAs associated with the cancer development. Particularly interesting are two miRNAs directly involved in DNA methylation of specific loci. miR-30d is responsible for methylation of CpG region in H19 noncoding RNA gene and miR191 downregulates the TET1 expression, the enzyme responsible for methylation removal in promoters of tumor suppressors (E.g., APC)(34,35).

From vast list of miRNAs that are associated with EC and could serve as diagnostic markers, most known are miR-182, miR-183, miR-200 and miR-205(4,36). miR-182 targets the CUL5 protein, ubiquitin ligase, which has altered expression in several types of cancers. CUL5 overexpression in EC model cell line resulted in decreased cell proliferation(32). CPEB1 mRNA is targeted, and its expression is downregulated by miR-183, which promotes cell proliferation, migration, invasion, and in vivo tumorigenesis in EC(37). The miR-200 family affects the PI3K/AKT/mTOR by downregulation of PTEN, tumor suppressor protein(4). Since mR-205 is overexpressed not only in EC(36), but also in other types of cancer(38,39), Favier et al.(4) do not find it suitable for diagnosis of EC but considers it as potential prognostic biomarker.



Although, the high number of factors responsible for development of EC, either environmental, hormonal, genetic or epigenetic, we still need many pieces of complex mosaic, to finish the whole picture of this carcinogenic process. Such discoveries might serve as a useful prognostic and diagnostic tool. Because of high rate of EC in regions of Central and Easter Europe (see Table 1), we suggest investigating the methylation status Slovak endometrial cancer samples to compare found gene inactivation with known data. Thus, it might be possible to adjust diagnosis in our region.



This article was created with the support of the OP Integrated Infrastructure for the project: Center for biomedical research – BIOMEDIRES – II. phase, ITMS: 313011W428, co‑financed by the European Regional De- velopment Fund.


Táto publikácia vznikla vďaka podpore v rámci Operačného programu Integrovaná infraštruktúra pre projekt: Centrum pre biomedicínsky výskum – BIOMEDIRES ‑ II. eta- pa , kód ITMS: 313011W428, spolufinancovaný zo zdrojov Európskeho fondu regionálneho rozvoja.



  1. Banno K, Kisu I, Yanokura M, Masuda K, Ueki A, Kobayashi Y, Susumu N, Aoki Epigenetics and genetics in endometrial cancer: new carcinogenic mechanisms and relationship with clinical practice. Epigenomics. 2012 Apr; 4(2): 147-62. doi: 10.2217/epi.12.13.
  2. Global Cancer Observatory, iarc.fr, (28. September 2021).
  3. Tao MH, Freudenheim DNA methylation in endometrial cancer. Epigenetics. 2010 Aug 16; 5(6): 491-8. doi: 10.4161/epi.5.6.12431. Epub 2010 Aug 16.
  1. Favier A, Rocher G, Larsen AK, Delangle R, Uzan C, Sabbah M, Castela M, Duval A, Mehats C, Canlorbe MicroRNA as Epigenetic Modifiers in Endometrial Cancer: A Systematic Review. Cancers (Basel). 2021 Mar 6; 13(5): 1137. doi: 10.3390/cancers13051137.
  2. Cancer Research UK, org/about-cancer/ womb-cancer/types-grades, (26. September 2021).
  3. Banno K, Yanokura M, Iida M, Masuda K, Aoki Carcinogenic mechanisms of endometrial cancer: Involvement of genetics and epigenetics. Journal of Obstetrics and Gynaecology Research, 2014 Aug; 40(8): 1957–67 doi: 10.1111/jog.12442.
  4. Vermij L, Smit V, Nout R, Bosse Incorporation of molecular characteristics into endometrial cancer management. Histopathology. 2020 Jan; 76(1): 52-63. doi: 10.1111/his.14015.
  5. Goulder A, Gaillard Molecular classification of endometrial cancer: entering an era of precision medicine. Journal of Gynecologic Oncology, 2022 May; 33(3): e47. doi: 10.3802/jgo.2022.33.e47.
  6. Cancer Genome Atlas Research Network, Kandoth C, Schultz N, Cherniack AD, Akbani R, Liu Y, Shen H, Robertson AG, Pashtan I, Shen R, Benz CC, Yau C, Laird PW, Ding L, Zhang W, Mills GB, Kucherlapati R, Mardis ER, Levine Integrated genomic characterization of endometrial carcinoma. Nature. 2013 May 2; 497(7447): 67-73. doi: 10.1038/ nature12113.
  7. Kim KR, Lax SF, Lazar AJ, Longacre TA, Malpica A, Matias-Guiu X, Nuc- ci M, Oliva Tumours of the Uterine Corpus in WHO Classification of Female Genital Tumours, 5th ed.; International Agency for Research on Cancer: Lyon, France, 2020; Volume 4.
  8. Muraki Y, Banno K, Yanokura M, Kobayashi Y, Kawaguchi M, Nomura H, Hirasawa A, Susumu N, Aoki Epigenetic DNA hypermethylation: clinical applications in endometrial cancer (Review). Oncol Rep. 2009 Nov; 22(5): 967-72. doi: 10.3892/or_00000523.
  9. Miyamoto T, Shiozawa T, Kashima H, Feng YZ, Suzuki A, Kurai M, Nikaido T, Konishi Estrogen up-regulates mismatch repair activity in normal and malignant endometrial glandular cells. Endocrinology. 2006 Oct; 147(10): 4863-70. doi: 10.1210/en.2006-0632. Epub 2006 Jul 6.
  10. Endoh Y, Tamura G, Ajioka Y, Watanabe H, Motoyama T. Frequent hypermethylation of the hMLH1 gene promoter in differentiated-type tumors of the stomach with the gastric foveolar Am J Pathol. 2000 Sep; 157(3): 717-22. doi: 10.1016/S0002-9440(10)64584-1.
  11. Truninger K, Menigatti M, Luz J, Russell A, Haider R, Gebbers JO, Bannwart F, Yurtsever H, Neuweiler J, Riehle HM, Cattaruzza MS, Heinimann K, Schär P, Jiricny J, Marra Immunohistochemical analysis reveals high frequency of PMS2 defects in colorectal cancer. Gastroenterology. 2005 May; 128(5): 1160-71. doi: 10.1053/j.gastro.2005.01.056.
  12. Chang Z, Zhang W, Chang Z, Song M, Qin Y, Chang F, Guo H, Wei Q. Expression characteristics of FHIT, p53, BRCA2 and MLH1 in families with a history of oesophageal cancer in a region with a high incidence of oesophageal Oncol Lett. 2015 Jan; 9(1): 430-436. doi: 10.3892/ ol.2014.2682. Epub 2014 Nov 7.
  13. Kawaguchi M, Banno K, Yanokura M, Kobayashi Y, Kishimi A, Ogawa S, Kisu I, Nomura H, Hirasawa A, Susumu N, Aoki Analysis of candidate target genes for mononucleotide repeat mutation in microsatellite instability-high (MSI-H) endometrial cancer. Int J Oncol. 2009 Nov; 35(5): 977-82 doi: 10.3892/ijo_00000411.
  1. Ignatov A, Bischoff J, Ignatov T, Schwarzenau C, Krebs T, Kuester D, Costa SD, Roessner A, Semczuk A, Schneider-Stock APC promoter hypermethylation is an early event in endometrial tumorigenesis. Cancer Sci. 2010 Feb; 101(2): 321-7. doi: 10.1111/j.1349-7006.2009.01397.x. Epub 2009 Oct 12.
  1. Yi TZ, Guo J, Zhou L, Chen X, Mi RR, Qu QX, Zheng JH, Zhai Prognostic value of E-cadherin expression and CDH1 promoter methylation in patients with endometrial carcinoma. Cancer Invest. 2011 Jan; 29(1): 86-92 doi: 10.3109/07357907.2010.512603. Epub 2010 Sep 27.
  2. Salvesen HB, Stefansson I, Kretzschmar EI, Gruber P, MacDonald ND, Ryan A, Jacobs IJ, Akslen LA, Das S. Significance of PTEN alterations in endometrial carcinoma: a population-based study of mutations, promoter methylation and PTEN protein Int J Oncol. 2004 Dec; 25(6): 1615-23.
  3. Zysman MA, Chapman WB, Bapat Considerations when analyzing the methylation status of PTEN tumor suppressor gene. Am J Pathol. 2002 Mar; 160(3): 795-800. doi: 10.1016/S0002-9440(10)64902-4. Erratum in: Am J Pathol 2002 Jun; 160(6): 2311.
  1. Risinger JI, Maxwell GL, Berchuck A, Barrett JC. Promoter hypermethylation as an epigenetic component in Type I and Type II endometrial Ann N Y Acad Sci. 2003 Mar; 983: 208-12. doi: 10.1111/j.1749- 6632.2003.tb05975.x.
  2. Liao X, Siu MK, Chan KY, Wong ES, Ngan HY, Chan QK, Li AS, Khoo US, Cheung AN. Hypermethylation of RAS effector related genes and DNA methyltransferase 1 expression in endometrial carcinogenesis. Int J Can- 2008 Jul 15; 123(2): 296-302. doi: 10.1002/ijc.23494.
  3. Berindan-Neagoe I, Monroig Pdel C, Pasculli B, Calin GA. MicroR- NAome genome: a treasure for cancer diagnosis and CA Cancer J Clin. 2014 Sep-Oct; 64(5): 311-36. doi: 10.3322/caac.21244. Epub 2014 Aug 7
  4. Betel D, Wilson M, Gabow A, Marks DS, Sander The microRNA.org resource: targets and expression. Nucleic Acids Res. 2008 Jan; 36(Database issue): D149-53. doi: 10.1093/nar/gkm995. Epub 2007 Dec 23.
  5. Ni J, Liang S, Shan B, Tian W, Wang H, Ren Methylation-associated silencing of miR-638 promotes endometrial carcinoma progression by targeting MEF2C. Int J Mol Med. 2020 Jun; 45(6): 1753-1770. doi: 10.3892/ ijmm.2020.4540. Epub 2020 Mar 16.
  6. Zhang W, Chen JH, Shan T, Aguilera-Barrantes I, Wang LS, Huang TH, Rader JS, Sheng X, Huang miR-137 is a tumor suppressor in endometrial cancer and is repressed by DNA hypermethylation. Lab Invest. 2018 Nov; 98(11): 1397-1407. doi: 10.1038/s41374-018-0092-x. Epub 2018 Jun 28.
  1. Yanokura M, Banno K, Adachi M, Aoki D, Abe Genome-wide DNA methylation sequencing reveals miR-663a is a novel epimutation candidate in CIMP-high endometrial cancer. Int J Oncol. 2017 Jun; 50(6): 1934- 1946. doi: 10.3892/ijo.2017.3966. Epub 2017 Apr 19.
  2. Hiroki E, Suzuki F, Akahira J, Nagase S, Ito K, Sugawara J, Miki Y, Suzuki T, Sasano H, Yaegashi MicroRNA-34 b functions as a potential tumor suppressor in endometrial serous adenocarcinoma. Int J Cancer. 2012 Aug 15; 131(4): E395-404. doi: 10.1002/ijc.27345. Epub 2012 Feb 28.
  1. Pavicic W, Perkiö E, Kaur S, Peltomäki Altered methylation at microRNA-associated CpG islands in hereditary and sporadic carcinomas: a methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA)-based approach. Mol Med. 2011; 17(7-8): 726-35. doi: 10.2119/molmed.2010.00239. Epub 2011 Feb 9.
  2. Tsuruta T, Kozaki K, Uesugi A, Furuta M, Hirasawa A, Imoto I, Susumu N, Aoki D, Inazawa miR-152 is a tumor suppressor microRNA that is silenced by DNA hypermethylation in endometrial cancer. Cancer Res. 2011 Oct 15; 71(20): 6450-62. doi: 10.1158/0008-5472.CAN-11-0364. Epub 2011 Aug 25.
  3. Huang YW, Liu JC, Deatherage DE, Luo J, Mutch DG, Goodfellow PJ, Miller DS, Huang Epigenetic repression of microRNA-129-2 leads to overexpression of SOX4 oncogene in endometrial cancer. Cancer Res. 2009 Dec 1; 69(23): 9038-46. doi: 10.1158/0008-5472.CAN-09-1499. Epub 2009 Nov 3.
  4. Devor EJ, Schickling BM, Reyes HD, Warrier A, Lindsay B, Goodheart MJ, Santillan DA, Leslie Cullin-5, a ubiquitin ligase scaffold protein, is significantly underexpressed in endometrial adenocarcinomas and is a target of miR-182. Oncol Rep. 2016 Apr; 35(4): 2461-5. doi: 10.3892/ or.2016.4605. Epub 2016 Feb 1.
  5. Li BL, Lu W, Lu C, Qu JJ, Yang TT, Yan Q, Wan CpG island hypermethylation-associated silencing of microRNAs promotes human endometrial cancer. Cancer Cell Int. 2013 May 16; 13(1): 44. doi: 10.1186/1475-2867-13-44.
  6. Moreno-Moya JM, Vilella F, Martínez S, Pellicer A, Simón The transcriptomic and proteomic effects of ectopic overexpression of miR-30d in human endometrial epithelial cells. Mol Hum Reprod. 2014 Jun; 20(6): 550-66. doi: 10.1093/molehr/gau010. Epub 2014 Jan 30.
  7. Yang C, Ota-Kurogi N, Ikeda K, Okumura T, Horie-Inoue K, Takeda S, Inoue S. MicroRNA-191 regulates endometrial cancer cell growth via TET1-mediated epigenetic modulation of J Biochem. 2020 Jul 1; 168(1): 7-14. doi: 10.1093/jb/mvaa014.
  8. Donkers H, Bekkers R, Galaal Diagnostic value of microRNA pan- el in endometrial cancer: A systematic review. Oncotarget. 2020 May 26; 11(21): 2010-2023. doi: 10.18632/oncotarget.27601.
  9. Xiong H, Chen R, Liu S, Lin Q, Chen H, Jiang MicroRNA-183 induces epithelial-mesenchymal transition and promotes endometrial cancer cell migration and invasion in by targeting CPEB1. J Cell Biochem. 2018 Nov; 119(10): 8123-8137. doi: 10.1002/jcb.26763. Epub 2018 Jun 20.
  10. Li JH, Sun SS, Li N, Lv P, Xie SY, Wang MiR-205 as a promising bomarker in the diagnosis and prognosis of lung cancer. Oncotarget. 2017 Aug 14; 8(54): 91938-91949. doi: 10.18632/oncotarget.20262.
  11. Chauhan N, Dhasmana A, Jaggi M, Chauhan SC, Yallapu miR- 205: A Potential Biomedicine for Cancer Therapy. Cells. 2020 Aug 25; 9(9): doi: 10.3390/cells9091957.