MicroRNA‑34b expression enhances chemosensitivity of endometrial cancer cells to paclitaxel

Aberrant DNA methylation is widely observed in various types of cancer, and expression of microRNAs (miRNAs/miRs) is suppressed by DNA methylation. The present study explored tumor suppressor miRNAs downregulated by DNA methylation in endometrial cancer cells, as the basis of a novel therapeutic approach for endometrial cancer. Among 821 candidate miRNAs, miR‑34b was identified as an upregulated miRNA after demethylation treatment in all four endometrial cancer cell lines (HEC‑108, SNG‑II, Ishikawa and HHUA) examined. miR‑34b expression with or without demethylation treatment in cancer cells was confirmed by TaqMan quantitative PCR. MYC and MET, the predicted target genes of miR‑34b, were downregulated at both the RNA and protein levels following miR‑34b overexpression. Following miR‑34b treatment, inhibition of cell growth and invasion, and cell cycle arrest were observed in HEC‑108 cells. Sensitivity to paclitaxel was increased in cancer cells with miR‑34b overexpression, compared with untreated cancer cells, but this difference was not identified for cisplatin or doxorubicin. In vivo, combination treatment with miR‑34b and paclitaxel markedly reduced tumor growth compared with treatment with negative control miRNA and paclitaxel. These data suggest that miR‑34b enhances paclitaxel sensitivity in endometrial cancer cells, and that miR‑34b and MET are key targets for treatment of endometrial cancer. The present results may contribute to the development of combination treatment with a demethylation agent, miR‑34b mimic or MET inhibitor and an anticancer drug.

Mutations of RAS genes in endometrial polyps

Endometrial polyps are common, yet the molecular mechanisms underlying their formation and progression remain unclear. We examined gene mutations possibly related to the pathogenesis of endometrial polyps, as well as to their clinical features. Four premenopausal patients with endometrial polyps, who were not under drug treatment, were recruited. Whole exomes of endometrial polyps and peripheral blood lymphocytes were analyzed by next‑generation sequencing, and somatic mutations were derived by subtraction. Then, 35 samples of endometrial polyps and 12 samples of atypical polypoid adenomyoma were newly recruited to validate the identified mutations by polymerase chain reaction‑reverse sequence specific oligonucleotide method. The mutations were also analyzed in separate stromal and glandular components of the polyps after laser‑capture microdissection. Whole exome sequencing revealed that KRAS mutations were the only type of mutation detectable in multiple cases (2/4). Targeted mutation analysis revealed that 16 of 35 samples (45.7%) of endometrial polyps harbored RAS mutations. Mutation‑positive cases exhibited a significantly higher number of endometrial polyps (3.25±2.70 vs. 1.74±0.87, P=0.045). Laser‑capture microdissection in NRAS‑mutated endometrial polyps revealed that both stromal and glandular components harbored RAS mutations. There was no RAS mutation in 12 samples of atypical polypoid adenomyoma. This is the first report demonstrating that pathogenic RAS mutations are frequent in non‑treated endometrial polyps. RAS mutations may have an important role in tumorigenesis and in the formation of multiple endometrial polyps.

Current status of uterine regenerative medicine for absolute uterine factor infertility

Though assisted reproduction technology has been developed, a treatment for absolute uterine factor infertility (AUFI), such as defects in the uterus, has not yet been established. Regenerative medicine has been developed and applied clinically over recent years; however, whole solid organs still cannot be produced. Though uterine regeneration has the potential to be a treatment for AUFI, there have been only a few studies on uterine regeneration involving the myometrium in vivo. In the present report, those relevant articles are reviewed. A literature search was conducted in PubMed with a combination of key words, and 10 articles were found, including nine in rat models and one in a mouse model. Of these studies, eight used scaffolds and two were performed without scaffolds. In four of these studies, scaffolds were re-cellularized with various cells. In the remaining four studies, scaffolds were transplanted alone, or other structures were used. Though the methods differed, the injured uterus recovered well, morphologically and functionally, in every study. Only 10 articles were relevant to our investigation, but the results were favorable, if limited to partial regeneration. Recently, uterus transplantation (UTx) has been investigated as a treatment for AUFI. However, UTx has many problems in the medical, ethical and social fields. Though the artificial uterus was also researched and some improvements in this technology were reported, it will take long time for this to reach a clinically applicable stage. Though the results of uterine regeneration studies were promising, these studies were conducted using animal models, so further human studies and trials are needed.

Synchronous endometrial and ovarian cancer in Lynch syndrome with a MSH2 germline mutation: A case report

Synchronous endometrial and ovarian cancer (SEOC) is a rare entity among gynecological cancers, which exhibits endometrioid histology in its early stages and generally has a good prognosis. However, diagnosis is difficult and recent reports have demonstrated that most clinically diagnosed cases of SEOC have clonally related cancers, indicating metastatic cancer. The association of SEOC with Lynch syndrome is also not clearly understood. We herein present the case of a 41-year-old SEOC patient with MSH2 mutation. The endometrial cancer was an endometrioid adenocarcinoma and the ovarian cancer was mainly endometrioid, but also included a clear cell carcinoma with a borderline clear cell adenofibromatous component, indicating primary ovarian cancer. Both tumors exhibited microsatellite instability (MSI) and loss of expression of MSH2 and MSH6. The patient had a family history of colorectal and gastric cancers. Genetic analysis revealed a germline mutation in exon 6 of MSH2 (c.1042C>T, p.Gln348*) and the patient was diagnosed with Lynch syndrome. This MSH2 mutation has only been registered in one case in the InSiGHT variant databases and has not been reported in a gynecological tumor or SEOC to date. This case is a rare example of a patient with genetically diagnosed Lynch syndrome who also developed SEOC. This synchronous cancer is not common, but it may be caused by Lynch syndrome. Testing for MSI and immunohistochemistry for mismatch repair deficiency is necessary in cases with suspected SEOC.

Screening for Lynch syndrome using risk assessment criteria in patients with ovarian cancer

Objective

Lynch syndrome is a cancer predisposition syndrome caused by germline mutation of DNA mismatch repair (MMR) genes. Lynch syndrome only causes about 0.4% of cases of ovarian cancer, which suggests that universal screening may not be cost-efficient. However, the frequency of Lynch syndrome in ovarian cancer is unclear in the Asian population. The goal of the study was to investigate a screening strategy using family history.

Methods

The subjects were 129 patients with ovarian cancer. Clinical and family history were collected using a self-administered questionnaire, and Society of Gynecologic Oncology (SGO) criteria 2007 and PREMM₅ were used for risk assessment. Microsatellite instability, immunohistochemistry, and methylation of MMR genes were analyzed.

Results

Of the 129 cases, 25 (19.4%) met the SGO criteria, and 4 of these 25 had MSI-high and MMR deficiency. Two cases had loss of MSH2 and MSH6, indicating MSH2 mutation, and the other two had loss of MLH1 and PMS2, including one without MLH1 methylation indicating MLH1 mutation. These results show that screening using family history can detect Lynch syndrome in 12.0% (3/25) of ovarian cancer cases. The 3 cases were positive for PREMM₅, but negative for Amsterdam II criteria and revised Bethesda guidelines. Genetic testing in one case with MSH2 and MSH6 deficiency confirmed the diagnosis of Lynch syndrome with MSH2 mutation.

Conclusion

This is the first study of screening for Lynch syndrome in ovarian cancer using clinical and family history in an Asian population. This approach may be effective for diagnosis in these patients.

Recent findings on epigenetic gene abnormalities involved in uterine cancer

Selective aberrant genetic effects that do not depend on abnormal DNA sequences are referred to as epigenetic abnormalities and are involved in carcinogenesis. In uterine cancer, various genes involved in apoptosis, cell cycle, DNA repair, cell proliferation and cell adhesion are abnormally methylated, resulting in gene silencing. Reversal of such epigenetic abnormalities in cancer cells is a potential strategy for cancer therapy, and studies on epigenetic abnormalities and treatment methods in uterine cancer are in progress. These include the evaluation of 5-hydroxymethylcytosine, which is present in cancer tissues at lower levels compared with those in normal tissues, as a prognostic marker in cervical cancer; combination therapy with 5-azacytidine and cisplatin; combination treatment focusing on tumor necrosis factor-related apoptosis-inducing ligand in cervical cancer; studies focusing on DNA mismatch repair in endometrial cancer; and use of a demethylating agent to reactivate tumor suppressor genes and inhibit tumor proliferation. Detection of epigenetic changes using biomarkers may be used for histological classification, evaluation of disease progression and identification of compounds that are able to modulate epigenetic changes and may be useful for uterine cancer treatment.

Aberrant chromatin remodeling in gynecological cancer

Epigenetic regulatory mechanisms are a current focus in studies investigating cancer. Chromatin remodeling alters chromatin structure and regulates gene expression, and aberrant chromatin remodeling is involved in carcinogenesis. AT-rich interactive domain-containing protein 1A (ARID1A) and SWItch/sucrose non-fermentable-related, matrix-associated, actin-dependent regulator of chromatin, subfamily a, member 4 are remodeling factors that are mutated in numerous types of cancer. In gynecological cancer, ARID1A mutations have been identified in 46-57% of clear cell carcinoma and 30% of endometrioid carcinoma. Mutations of chromodomain helicase, DNA-binding protein 4 have been detected in 17-21% of endometrial serous cancer, and mutations of ARID1A and mixed-lineage leukemia 3 occur in 36 and 27% of uterine carcinosarcoma, respectively. These data suggest that aberrant chromatin remodeling is a potential cause of cancer, and have led to the development of novel proteins targeting these processes. Additional accumulation of information on the mechanisms of chromatin remodeling and markers for these events may promote personalized anticancer therapies.

New use of microsatellite instability analysis in endometrial cancer

The increasing incidence of obesity and diabetes due to changes in diet, earlier menarche, delayed menopause, late marriage, and declining birth rate have resulted in an increase in the number of endometrial cancer cases over the last few decades. Although surgical therapy is sufficient for early endometrial cancer, there is no effective therapy for patients with advanced and recurrent endometrial cancer. The oncogenic mechanism of endometrial cancer involves microsatellite instability (MSI) caused by dysfunction of DNA mismatch repair genes in 30% of patients. Immune checkpoint inhibitors, including anti-programmed death (PD)-1 and anti-PD-ligand 1 antibodies, are of interest as novel anticancer drugs; however, these drugs are currently expensive, and there is a need to select patients who will benefit from their use. The use of MSI analysis as a predictive biomarker for the therapeutic efficacy of these drugs may be useful for reducing the costs of drug therapy.

Genome-wide DNA methylation sequencing reveals miR-663a is a novel epimutation candidate in CIMP-high endometrial cancer

Aberrant DNA methylation is widely observed in many cancers. Concurrent DNA methylation of multiple genes occurs in endometrial cancer and is referred to as the CpG island methylator phenotype (CIMP). However, the features and causes of CIMP-positive endometrial cancer are not well understood. To investigate DNA methylation features characteristic to CIMP-positive endometrial cancer, we first classified samples from 25 patients with endometrial cancer based on the methylation status of three genes, i.e. MLH1, CDH1 (E-cadherin) and APC: CIMP-high (CIMP-H, 2/25, 8.0%), CIMP-low (CIMP-L, 7/25, 28.0%) and CIMP-negative (CIMP(-), 16/25, 64.0%). We then selected two samples each from CIMP-H and CIMP(-) classes, and analyzed DNA methylation status of both normal (peripheral blood cells: PBCs) and cancer tissues by genome-wide, targeted bisulfite sequencing. Genomes of the CIMP-H cancer tissues were significantly hypermethylated compared to those of the CIMP(-). Surprisingly, in normal tissues of the CIMP-H patients, promoter region of the miR-663a locus is hypermethylated relative to CIMP(-) samples. Consistent with this finding, miR-663a expression was lower in the CIMP-H PBCs than in the CIMP(-) PBCs. The same region of the miR663a locus is found to be highly methylated in cancer tissues of both CIMP-H and CIMP(-) cases. This is the first report showing that aberrant DNA methylation of the miR-663a promoter can occur in normal tissue of the cancer patients, suggesting a possible link between this epigenetic abnormality and endometrial cancer. This raises the possibility that the hypermethylation of the miR-663a promoter represents an epimutation associated with the CIMP-H endometrial cancers. Based on these findings, relationship of the aberrant DNA methylation and CIMP-H phenotype is discussed.

Genome-wide analysis of gynecologic cancer: The Cancer Genome Atlas in ovarian and endometrial cancer

Cancer typically develops due to genetic abnormalities, but a single gene abnormality cannot completely account for the onset of cancer. The Cancer Genome Atlas (CGA) project was conducted for the cross-sectional genome-wide analysis of numerous genetic abnormalities in various types of cancer. This approach has facilitated the identification of novel AT-rich interaction domain 1A gene mutations in ovarian clear cell carcinoma, frequent tumor protein 53 (TP53) gene mutations in high-grade ovarian serous carcinoma, and Kirsten rat sarcoma and B-rapidly accelerated fibrosarcoma proto-oncogene, serine/threonine kinase gene mutations in low-grade ovarian serous carcinoma. Genome-wide analysis of endometrial cancers has led to the establishment of four subgroups: Polymerase ultramutated, microsatellite instability hypermutated, genome copy-number low and genome copy-number high. These results may facilitate the improvement of the prediction of patient prognosis and therapeutic sensitivity in various types of gynecologic cancer. The enhanced use of currently available therapeutic agents and the development of novel drugs may be facilitated by the novel classification of ovarian cancer based on TP53 mutations, the efficacy of poly (ADP-ribose) polymerase inhibitors for tumors with breast cancer 1/2 mutations and the effect of phosphoinositide-3-kinase (PI3K)/mammalian target of rapamycin inhibitors for tumors with mutations in the PI3K/protein kinase B signaling pathway. Important results have been revealed by genome-wide analyses; however, the pathogenic underlying mechanisms of gynecologic cancer will require further studies and multilateral evaluation using epigenetic, transcriptomic and proteomic analyses, in addition to genomic analysis.

Carcinoma of the lower uterine segment diagnosed with Lynch syndrome based on MSH6 germline mutation: A case report

Endometrial cancer in the lower uterine segment (LUS) is associated with Lynch syndrome with MLH1 or MSH2 germline mutation. Here, we report a case of carcinoma of the LUS diagnosed with Lynch syndrome based on MSH6 germline mutation in a 46-year-old woman with abnormal vaginal bleeding. She had had rectal cancer at age 39 with a family history of colon cancer (father, 75 years), pancreatic cancer (paternal grandmother, 74 years), and colon cancer (maternal grandmother, 85 years). Magnetic resonance imaging showed a tumor in the LUS. Endometrial biopsy revealed endometrioid adenocarcinoma G1. As her cancer history met the revised Bethesda criteria, we examined microsatellite instability and the result was negative, but loss of the MSH6 expression was detected by immunohistochemistry. Genetic testing revealed deleterious germline mutation of MSH6, which was compatible with Lynch syndrome. To our knowledge, this is the first case of endometrial carcinoma of the LUS with MSH6 germline mutation.

Methylation Analysis of DNA Mismatch Repair Genes Using DNA Derived from the Peripheral Blood of Patients with Endometrial Cancer: Epimutation in Endometrial Carcinogenesis

Germline mutation of DNA mismatch repair (MMR) genes is a cause of Lynch syndrome. Methylation of MutL homolog 1 (MLH1) and MutS homolog 2 (MSH2) has been detected in peripheral blood cells of patients with colorectal cancer. This methylation is referred to as epimutation. Methylation of these genes has not been studied in an unselected series of endometrial cancer cases. Therefore, we examined methylation of MLH1, MSH2, and MSH6 promoter regions of peripheral blood cells in 206 patients with endometrial cancer using a methylation-specific polymerase chain reaction (MSP). Germline mutation of MMR genes, microsatellite instability (MSI), and immunohistochemistry (IHC) were also analyzed in each case with epimutation. MLH1 epimutation was detected in a single patient out of a total of 206 (0.49%)-1 out of 58 (1.72%) with an onset age of less than 50 years. The patient with MLH1 epimutation showed high level MSI (MSI-H), loss of MLH1 expression and had developed endometrial cancer at 46 years old, complicated with colorectal cancer. No case had epimutation of MSH2 or MSH6. The MLH1 epimutation detected in a patient with endometrial cancer may be a cause of endometrial carcinogenesis. This result indicates that it is important to check epimutation in patients with endometrial cancer without a germline mutation of MMR genes.

Differential micro ribonucleic acid expression profiling in ovarian endometrioma with leuprolide acetate treatment

AIM

Micro ribonucleic acids (miRNAs) play an important pathological role in endometriosis. Leuprolide acetate, an analog of gonadotropin-releasing hormone, is widely used to treat endometriosis; however, the molecular mechanisms involved in endometriotic tissue regression remain unclear. We performed miRNA expression profiling of clinical ovarian endometrioma to obtain insight into the effects of leuprolide acetate treatment.

METHODS

We obtained clinical samples from nine normal eutopic endometrium, eight ovarian endometriotic, and 12 leuprolide acetate-treated endometriotic tissues. We compared the miRNA expression profiles of the three groups by performing TaqMan Array MicroRNA Card and bioinformatic analysis.

RESULTS

Two miRNAs, miR-939 and miR-154, were upregulated in endometriotic tissue and downregulated in leuprolide acetate-treated endometriotic tissue. Five miRNAs (miR-146a, miR-142-3p, miR-136*, miR-125b-1* and miR-15b*) were unchanged in endometriotic tissue but were upregulated under leuprolide acetate treatment. Ingenuity pathway analysis using predicted target genes for the seven identified miRNAs suggested the involvement of a range of pathways, including axonal guidance, bone morphogenetic protein, phosphatase and tensin homolog and nitric oxide signaling; molecular mechanisms of cancer; and the adipogenesis and signal transducer and activator of transcription 3 (STAT3) pathways.

CONCLUSIONS

To our knowledge, this is the first report profiling the miRNAs of endometrioma under leuprolide acetate treatment. The expression of seven miRNAs was modulated, concomitant with the disease state. This result gives new insight into the effects of leuprolide acetate treatment. Further investigation using quantitative reverse transcriptase-polymerase chain reaction and immunohistochemistry will allow us to validate the results of this study and to explore new therapeutic targets and biomarkers of endometriosis.

Metformin: A candidate for the treatment of gynecological tumors based on drug repositioning

Metformin is a first-line drug used for the treatment of type 2 diabetes. Recently, metformin has been reported to reduce the carcinogenic risk and inhibit tumor cell growth in glioma and breast cancer. The anticancer action of metformin involves the enhancement of phosphorylation of liver kinase B1, activation of adenosine monophosphate-activated protein kinase and inhibition of mammalian target of rapamycin, which reduces cell growth. Metformin is anticipated to exert antitumor effects in gynecological cancer, and its efficacy for the treatment of endometrial, breast and ovarian cancer has been suggested in preclinical studies and clinical trials. Although the effect of metformin on cervical cancer remains to be examined in clinical trials, its antitumor effects have been reported in preclinical studies. Thus, the use of metformin for the treatment of gynecological cancer may become a successful example of drug repositioning, following establishment of the drug's antitumor effects, risk evaluation, screening and validation of efficacy.

ARID1A gene mutation in ovarian and endometrial cancers (Review)

The AT-rich interacting domain-containing protein 1A gene (ARID1A) encodes ARID1A, a member of the SWI/SNF chromatin remodeling complex. Mutation of ARID1A induces changes in expression of multiple genes (CDKN1A, SMAD3, MLH1 and PIK3IP1) via chromatin remodeling dysfunction, contributes to carcinogenesis, and has been shown to cause transformation of cells in association with the PI3K/AKT pathway. Information on ARID1A has emerged from comprehensive genome-wide analyses with next-generation sequencers. ARID1A mutations have been found in various types of cancer and occur at high frequency in endometriosis-associated ovarian cancer, including clear cell adenocarcinoma and endometrioid adenocarcinoma, and also occur at endometrial cancer especially in endometrioid adenocarcinoma. It has also been suggested that ARID1A mutation occurs at the early stage of canceration from endometriosis to endometriosis-associated carcinoma in ovarian cancer and also from atypical endo-metrial hyperplasia to endometrioid adenocarcinoma in endometrial cancer. Therefore, development of a screening method that can detect mutations of ARID1A and activation of the PI3K/AKT pathway might enable early diagnosis of endometriosis-associated ovarian cancers and endometrial cancers. Important results may also emerge from a current clinical trial examining a multidrug regimen of temsirolimus, a small molecule inhibitor of the PI3K/AKT pathway, for treatment of advanced ovarian clear cell adenocarcinoma with ARID1A mutation and PI3K/AKT pathway activation. Also administration of sorafenib, a multikinase inhibitor, can inhibit cancer proliferation with PIK3CA mutation and resistance to mTOR inhibitors and GSK126, a molecular-targeted drug can inhibit proliferation of ARID1A-mutated ovarian clear cell adenocarcinoma cells by targeting and inhibiting EZH2. Further studies are needed to determine the mechanism of chromatin remodeling dysregulation initiated by ARID1A mutation, to develop methods for early diagnosis, to investigate new cancer therapy targeting ARID1A, and to examine the involvement of ARID1A mutations in development, survival and progression of cancer cells.

Differential mRNA expression profiling in ovarian endometriotic tissue with versus without leuprolide acetate treatment

AIM

Leuprolide acetate, an analog of gonadotropin-releasing hormone (GnRH), regresses endometriotic tissue and reduces pain, resulting in clinical improvement upon treatment. The molecular mechanisms involved in the regression of endometriotic tissue, however, remain to be elucidated. In this study, we performed genome-wide gene expression profiling of clinical specimens of ovarian endometrioma to obtain insight into the effects of leuprolide acetate treatment.

METHODS

We obtained clinical samples from nine normal eutopic endometrium tissues, eight ovarian endometriotic tissues, and 12 leuprolide acetate-treated endometriotic tissues. We compared the gene expression profiles of the three groups using Affymetrix GeneChip Human genome arrays and bioinformatic analysis, including molecular concept analysis.

RESULTS

Leuprolide acetate-treated endometriotic tissue showed downregulated genes associated with the biological functions of steroid hormone regulation, cell proliferation, inflammation, and intracellular signaling. These genes included PTGDS, GRP, APLP2, PLTP, and FGFRL1. In contrast, genes upregulated by leuprolide acetate treatment were associated with cell growth inhibition and apoptosis. These genes included CARD11 and USP18.

CONCLUSIONS

These preliminary results based on GeneChip analysis suggest that leuprolide acetate treatment induces a modulation of gene expression that allows for cooperative alterations in disease state. This study gives new insight into the effects of leuprolide acetate treatment. Further investigations with quantitative reverse transcription-polymerase chain reaction and immunohistochemistry are needed to validate this study and to explore new therapeutic targets and biomarkers of endometriosis.

Drug repositioning for gynecologic tumors: a new therapeutic strategy for cancer

The goals of drug repositioning are to find a new pharmacological effect of a drug for which human safety and pharmacokinetics are established and to expand the therapeutic range of the drug to another disease. Such drug discovery can be performed at low cost and in the short term based on the results of previous clinical trials. New drugs for gynecologic tumors may be found by drug repositioning. For example, PPAR ligands may be effective against ovarian cancer, since PPAR activation eliminates COX-2 expression, arrests the cell cycle, and induces apoptosis. Metformin, an antidiabetic drug, is effective for endometrial cancer through inhibition of the PI3K-Akt-mTOR pathway by activating LKB1-AMPK and reduction of insulin and insulin-like growth factor-1 due to AMPK activation. COX-2 inhibitors for cervical cancer may also be examples of drug repositioning. PGE2 is induced in the arachidonate cascade by COX-2. PGE2 maintains high expression of COX-2 and induces angiogenic factors including VEGF and bFGF, causing carcinogenesis. COX-2 inhibitors suppress these actions and inhibit carcinogenesis. Combination therapy using drugs found by drug repositioning and current anticancer drugs may increase efficacy and reduce adverse drug reactions. Thus, drug repositioning may become a key approach for gynecologic cancer in drug discovery.

MicroRNAS in endometrial cancer: recent advances and potential clinical applications

Endometrial cancer is a common malignant gynecological tumor, but there are few biomarkers that are useful for early and accurate diagnosis and few treatments other than surgery. However, use of microRNAs (miRNAs) that induces gene downregulation in cells may permit effective and minimally invasive diagnosis and treatment. In endometrial cancer cells, expression levels of miRNAs including miR-185, miR-210 and miR-423 are upregulated and those of miR-let7e, miR-30c and miR-221 are downregulated compared to normal tissues, and these miRNAs are involved in carcinogenesis, invasion and metastasis. miRNAs with expression changes such as miR-181b, miR-324-3p and miR-518b may be used as prognostic biomarkers and transfection of miR-152 may inhibit cancer growth. However, most current studies of miRNAs are at a basic level and further work is needed to establish clinical applications targeting miRNAs.

Aurora kinase A has a significant role as a therapeutic target and clinical biomarker in endometrial cancer

Aurora kinase A (AURKA) regulates the cell cycle checkpoint and maintains genomic integrity. AURKA is overexpressed in various malignant tumors and its upregulation induces chromosomal instability, which leads to aneuploidy and cell transformation. To investigate the role of AURKA in endometrial cancer, we evaluated the association of immunohistochemical expression of AURKA with clinicopathological factors. Furthermore, we examined the effects of AURKA inhibition by transfected siRNA in HEC-1B cells on colony-forming ability, invasion and migration capacity, and chemosensitivity. Immunohistochemical staining showed that overexpression of AURKA was significantly associated with tumor grade (P<0.05) and poor histologic differentiation (P<0.05). The recurrence rate also tended to be high in cases with overexpression of AURKA (P<0.1) and these cases also had a tendency for shorter disease-free survival (DFS) (P<0.1). AURKA inhibition in endometrial cancer cell lines significantly decreased cell growth, invasion and migration (P<0.05), and increased chemosensitivity to paclitaxel. We also evaluated the efficacy of a combination of AURKA siRNA and paclitaxel against subcutaneous tumors formed in a nude mouse. After treatment, the tumor volume shrank significantly compared to treatment with paclitaxel only (P<0.05). To our knowledge, this is the first study in endometrial carcinoma to show a correlation between overexpression of AURKA and tumor grade, histological type and sensitivity to paclitaxel. AURKA is a promising therapeutic target in endometrial cancer and the combination therapy with AURKA inhibitors and paclitaxel could be effective for endometrial cancer that is resistant to conventional treatment and has a poor prognosis.

Features of ovarian cancer in Lynch syndrome (Review)

Lynch syndrome is a hereditary ovarian cancer with a prevalence of 0.9-2.7%. Lynch syndrome accounts for 10-15% of hereditary ovarian cancers, while hereditary breast and ovarian cancer syndrome accounts for 65-75% of these cancers. The lifetime risk for ovarian cancer in families with Lynch syndrome is ~8%, which is lower than colorectal and endometrial cancers, and ovarian cancer is not listed in the Amsterdam Criteria II. More than half of sporadic ovarian cancers are diagnosed in stage III or IV, but ≥80% of ovarian cancers in Lynch syndrome are diagnosed in stage I or II. Ovarian cancers in Lynch syndrome mostly have non-serous histology and different properties from those of sporadic ovarian cancers. A screening method for ovarian cancers in Lynch syndrome has yet to be established and clinical studies of prophylactic administration of oral contraceptives are not available. However, molecular profiles at the genetic level indicate that ovarian cancer in Lynch syndrome has a more favorable prognosis than sporadic ovarian cancer. Inhibitors of the phosphatidylinositol 3-kinase/mammalian target of the rapamycin pathway and anti-epidermal growth factor antibodies may have efficacy for the disease. To the best of our knowledge, this is the first review focusing on ovarian cancer in Lynch syndrome.

Candidate biomarkers for cervical cancer treatment: Potential for clinical practice (Review)

Cervical cancer ranks high among the causes of female cancer mortalities and is an important disease in developing and developed countries. Current diagnosis of cervical cancer depends on colposcopy, pathological diagnosis and preoperative diagnosis using methods, including magnetic resonance imaging and computed tomography. Advanced cervical cancer has a poor prognosis. The tumor marker squamous cell carcinoma is conventionally used for screening, but recent studies have revealed the mechanisms of carcinogenesis and the factors associated with a poor prognosis in cervical cancer. These include epigenetic biomarkers, with the methylation level of the checkpoint with forkhead and ring finger gene being potentially useful for predicting the malignancy of cervical cancer and sensitivity to treatment with paclitaxel. The extent of methylation of the Werner DNA helicase gene is also useful for determining sensitivity to an anticancer agent, CPT-11. In addition to epigenetic changes, the expression levels of hypoxia-inducible factor 1α subunit, epidermal growth factor receptor and cyclooxygenase-2 have been reported as possible biomarkers in cervical cancer. Novel prognostic factors, including angiogenic factors, fragile histidine triad, thymidylate synthase, glucose-related protein 58 and mucin antigens, have also been described, and hemoglobin and platelets may also be significant prognostic biomarkers. Utilization of these biomarkers may facilitate personalized treatment and improved outcomes in cervical cancer.

Hereditary gynecological tumors associated with Peutz-Jeghers syndrome (Review)

Peutz-Jeghers syndrome (PJS) is an autosomal dominant disease that is characterized by gastrointestinal hamartomatous polyposis and mucocutaneous melanin spots. The tumor suppressor gene, STK11/LKB1, which is located on chromosome 19p13.3, has been reported to be responsible for this condition. PJS is complicated by benign and malignant tumors of various organs and complications from rare diseases, including sex cord tumor with annular tubules (SCTAT) and minimal deviation adenocarcinoma (MDA), which have also recently attracted attention in the field of gynecology. Among the total MDA cases, 10% are complications of PJS, and mutations in the STK11 gene are closely associated with the development and prognosis of MDA. Furthermore, a new type of uterine cervical tumor, lobular endocervical glandular hyperplasia (LEGH), has been identified and has been predicted to be a precancerous lesion of MDA. The first case of LEGH induced by a germline STK11 mutation has also been described. A high risk of endometrial cancer in PJS has also been reported. These developments suggest that PJS is an important syndrome of hereditary gynecological tumors that requires further study.

Current status of molecular-targeted drugs for endometrial cancer (Review)

Endometrial cancer is a common gynecological malignant tumor in Western countries and its incidence has also been on the increase in Asia. Genetic abnormalities related to onset and progression of malignancy in the endometrial membrane and signaling system have been identified and the developmental mechanism of endometrial cancer is becoming elucidated. The identification of the molecules related to these abnormalities has led to new potential treatment regimens for endometrial cancer, using molecular-targeted drugs. The current chemotherapy for endometrial cancer often causes systemic side effects that require discontinuation of the treatment. Furthermore, a treatment regimen for cancers of rare histological types has not been established. Recent studies on endometrial cancer revealed patterns of genetic disorders that differ among the histological types. Genetic and molecular information that underlie pathological changes and is associated with DNA mismatch repair genes and epigenetic regulation was also identified. Targeting of these mechanisms with molecular-targeted drugs has been performed with the aim of linking treatment to the carcinogenic mechanism at the molecular and genetic levels. However, the response rates with single-agent therapy are generally low and several problems remain unresolved. Trials of combinations of molecular-targeted drugs with currently available treatments and identification of factors determining sensitivity are required to overcome these difficulties.

Aurora kinase inhibitors: Potential molecular-targeted drugs for gynecologic malignant tumors

Chemotherapy and surgery are important treatment strategies for gynecologic malignant tumors such as ovarian, cervical and endometrial cancer. However, many anticancer drugs currently available are cytotoxic and cause strong adverse reactions in patients. Aurora kinases have attracted increasing attention in recent years as serine/threonine kinases with various roles in cell division, including chromosomal agglutination and segregation, functions of centromeres, centrosomal maturation, spindle formation and cytokinesis. Aurora kinases are overexpressed in a number of cancers and recent studies have shown that they are involved in onco genesis and cause an aberrant increase in centrosome number, emergence of polykaryocytes and failure of cancer inhibition mechanisms. Thus, drugs that inhibit Aurora kinases are likely to exert anticancer effects in various fields, including the gynecologic field. Aurora kinase inhibitors exert antitumor effects in monotherapy and synergistic effects in combination therapy with taxane-based anticancer agents for gynecologic tumors and are likely to increase the efficacy of existing anticancer drugs. Current Aurora kinase inhibitors include ZM447439, Hesperadin, VX-680/MK-0457, AT9283 and Barasertib, and clinical trials are ongoing to verify the effects of these inhibitors.

MicroRNAs in endometrial cancer

MicroRNAs (miRNAs) are small non-coding ribonucleic acids (RNAs) of approximately 22 bp that induce RNA interference with a complementary messenger RNA (mRNA) and act in silencing of mRNA. miRNAs are strongly associated with cancer development and those involved in carcinogenesis are classified into oncogenic miRNAs and tumor suppressor miRNAs (tumor suppressor miRs). Specific miRNAs are expressed in various tissues and changes in regulation of gene expression are thought to cause carcinogenesis. Thus, tissue-specific miRNAs may be biomarkers for cancer diagnosis and prognosis. Approaches to application of miRNAs as cancer therapy are also ongoing, based on the involvement of miRNAs in carcinogenesis. In endometrial cancer, miRNAs are associated with regulation of gene expression, epigenetic dysfunction and carcinogenesis. Thus, miRNAs are likely to have key roles in diagnosis, prognostic prediction, and therapy in endometrial cancer.

New candidate therapeutic agents for endometrial cancer: potential for clinical practice (review)

Cases of endometrial cancer have increased in recent years, but the prognosis of patients with this disease has also been improved by combined modality therapy with surgery, radiotherapy and chemotherapy. However, the development of new therapy is required from the perspectives of conservation of fertility and efficacy for recurrent and intractable cancer. New candidate therapeutic agents for endometrial cancer include fourth-generation progestins for inhibition of growth and differentiation of endometrial glands; metformin for reduction of hTERT expression in the endometrium and inhibition of the mTOR pathway by activation of AMPK, with consequent inhibition of the cell cycle; mTOR inhibitors for supressing growth of cancer cells by G1 cell cycle arrest; microRNAs involved in the molecular mechanisms of oncogenesis and progression; and HDAC inhibitors that block the growth of cancer cells by transcriptional elevation of tumor-suppressor genes, cell cycle arrest and induction of apoptosis. In this study, we review the background and early clinical evidence for these agents as new therapeutic candidates for endometrial cancer.

Relationship of lower uterine segment cancer with Lynch syndrome: a novel case with an hMLH1 germline mutation

Lynch syndrome is a genetic disease that often develops in patients with endometrial cancer and is caused by abnormal DNA mismatch repair (MMR) genes. In the United States, it was recently reported that the prevalence of Lynch syndrome with an hMSH2 mutation in patients with endometrial cancer in the lower uterine segment (LUS) is much greater than that in patients with endometrial cancer, although no such reports have been published in Asia. In this study, we examined the correlation between endometrial cancer in LUS and abnormalities in MMR genes. We examined 625 patients, who were diagnosed with endometrial cancer and underwent a hysterectomy. Nine patients (1.4%) had cancer based on pathological confirmation of a tumor in the lower part of the uterus and no cancer in the upper part. These cases were compared with 27 cases of sporadic endometrial (non-LUS) cancer. The age and BMI of the patients with LUS cancer were significantly lower than those of the patients with non-LUS cancer. No differences were observed in the pathological characteristics. The microsatellite instability (MSI)-positive rates were similar. Immunohistochemistry showed a decreased expression of hMLH1 and hMSH6 in patients with LUS cancer. In contrast with earlier reports from the United States, hMSH2 was expressed in all the cases. Of the 2 patients with LUS cancer who exhibited high MSI, 1 patient showed abnormal methylation of hMLH1, while the other patient was diagnosed with Lynch syndrome with a mutation in the hMLH1 gene. This is the second report on the relationship of LUS cancer and Lynch syndrome, and the first to describe an Asian patient with LUS cancer with Lynch syndrome induced by an hMLH1 mutation.

Epigenetics and genetics in endometrial cancer: new carcinogenic mechanisms and relationship with clinical practice

Endometrial cancer is the seventh most common cancer worldwide among females. An increased incidence and a younger age of patients are also predicted to occur, and therefore elucidation of the pathological mechanisms is important. However, several aspects of the mechanism of carcinogenesis in the endometrium remain unclear. Associations with genetic mutations of cancer-related genes have been shown, but these do not provide a complete explanation. Therefore, epigenetic mechanisms have been examined. Silencing of genes by DNA hypermethylation, hereditary epimutation of DNA mismatch repair genes and regulation of gene expression by miRNAs may underlie carcinogenesis in endometrial cancer. New therapies include targeting epigenetic changes using histone deacetylase inhibitors. Some cases of endometrial cancer may also be hereditary. Thus, patients with Lynch syndrome which is a hereditary disease, have a higher risk for developing endometrial cancer than the general population. Identification of such disease-related genes may contribute to early detection and prevention of endometrial cancer.

Association of epigenetic inactivation of the WRN gene with anticancer drug sensitivity in cervical cancer cells

The Werner (WRN) gene codes for a DNA helicase that contributes to genomic stability and has been identified as the gene responsible for progeria. Recent studies have shown reduced WRN expression due to aberrant DNA hypermethylation in cancer cells. Furthermore, WRN expression is thought to affect sensitivity to DNA topoisomerase I inhibitors in cancer therapy. In this study, we examined the relationship between aberrant DNA hypermethylation of WRN and the sensitivity of cervical cancer cells to anticancer drugs. DNA was extracted from samples from 22 patients with primary cervical cancer and 6 human cervical cancer-derived cell lines. Aberrant DNA hypermethylation was analyzed by methylation-specific PCR. WRN expression in cultured cells before and after addition of 5-aza-2-deoxycytidine, a demethylating agent, was examined using RT-PCR. The sensitivity of cells to anticancer drugs was determined using a collagen gel droplet embedded culture drug sensitivity test (CD-DST). siRNA against WRN was transfected into a cervical cancer-derived cell line with high WRN expression. Changes in drug sensitivity after silencing WRN were determined by CD-DST. Aberrant DNA hypermethylation and decreased expression of WRN were detected in 7/21 cases of primary cervical cancer and in two cervical cancer-derived cell lines. These two cell lines showed high sensitivity to CPT-11, a topoisomerase I inhibitor, but became resistant to CPT-11 after treatment with 5-aza-2-deoxycytidine. Transfection of siRNA against WRN increased the sensitivity of the cells to CPT-11. Aberrant DNA hypermethylation of WRN also increased the sensitivity of cervical cancer cells to CPT-11. Therefore, epigenetic inactivation of this gene may be a biomarker for selection of drugs for the treatment of cervical cancer. This is the first report to show a relationship between the methylation of the WRN gene and sensitivity to CPT-11 in gynecological cancers.

Epimutation and cancer: a new carcinogenic mechanism of Lynch syndrome (Review)

Epimutation is defined as abnormal transcriptional repression of active genes and/or abnormal activation of usually repressed genes caused by errors in epigenetic gene repression. Epimutation arises in somatic cells and the germline, and constitutional epimutation may also occur. Epimutation is the first step of tumorigenesis and can be a direct cause of carcinogenesis. Cancers associated with epimutation include Lynch syndrome (hereditary non-polyposis colorectal cancer, HNPCC), chronic lymphocytic leukemia, breast cancer and ovarian cancer. Epimutation has been shown for many tumor suppressor genes, including RB, VHL, hMLH1, APC and BRCA1, in sporadic cancers. Methylation has recently been shown in DNA from normal tissues and peripheral blood in cases of sporadic colorectal cancer and many studies show constitutive epimutation in cancers. Epimutation of DNA mismatch repair (MMR) genes (BRCA1, hMLH1 and hMSH2) involved in development familial cancers has also been found. These results have led to a focus on epimutation as a novel oncogenic mechanism.

Indocyanine green fluorescence imaging for evaluation of uterine blood flow in cynomolgus macaque

Background

Uterine blood flow is an important factor in uterine viability, but the number of blood vessels required to maintain viability is uncertain. In this study, indocyanine green (ICG) fluorescence imaging was used to examine uterine hemodynamics and vessels associated with uterine blood flow in cynomolgus macaque.

Methods

The uterus of a female cynomolgus macaque was cut from the vaginal canal to mimic a situation during trachelectomy or uterine transplantation surgery in which uterine perfusion is maintained only with uterine and ovarian vessels. Intraoperative uterine hemodynamics was observed using ICG fluorescence imaging under conditions in which various nutrient vessels were selected by clamping of blood vessels. A time-intensity curve was plotted using imaging analysis software to measure the T_max of uterine perfusion for selected blood vessel patterns. Open surgery was performed with the uterus receiving nutritional support only from uterine vessels on one side. The size of the uterus after surgery was monitored using transabdominal ultrasonography.

Results

The resulting time-intensity curves displayed the average intensity in the regions of the uterine corpus and uterine cervix, and in the entire uterus. Analyses of the uterine hemodynamics in the cynomolgus macaque showed that uterine vessels were significantly related to uterine perfusion (P = 0.008), whereas ovarian vessels did not have a significant relationship (P = 0.588). When uterine vessels were clamped, ovarian vessels prolonged the time needed to reach perfusion maximum. Postoperative transabdominal ultrasonography showed that the size of the uterus was not changed 2 months after surgery, with recovery of periodic menstruation. The cynomolgus macaque has got pregnant with favorable fetus well-being.

Conclusion

Uterine vessels may be responsible for uterine blood flow, and even one uterine vessel may be sufficient to maintain uterine viability in cynomolgus macaque. Our results show that ICG fluorescence imaging is useful for evaluation of uterine blood flow since this method allows real-time observation of uterine hemodynamics.

Biomarkers in endometrial cancer: Possible clinical applications (Review)

The number of cases of endometrial cancer has shown a tendency to increase in recent years. Endometrial cancer originates from the endometrium and is classified, based on the development mechanism, into types 1 and 2, which are responsive and non-responsive to estrogen, respectively, and have significantly different gene expression profiles. Studies of genes with abnormal expression in endometrial cancer have identified multiple oncogenes, tumor suppressors, mismatch repair genes, apoptosis-associated genes, levels of hormone receptors and DNA ploidy and aneuploidy as biomarkers of endometrial cancer. The use of these molecules and genes may facilitate accurate diagnosis and prognostic prediction and contribute to individualized treatment. Trials of drugs which target these biomarkers and searches for new biomarkers using cDNA microarrays and RT-qPCR are ongoing and it is likely that these findings can be translated to clinical use.

Progestin therapy for endometrial cancer: the potential of fourth-generation progestin (review)

Progestin preparations are made of synthetic progesterone and have often been used for hormone therapy in gynecological patients with endometriosis or endometrial cancer. Hormone therapy using progestin is considered to be one of the effective means of treatment particularly when dealing with endometrial cancer (an estrogen-dependent tumor). Numerous reports have been published concerning its efficacy in advanced or recurrent cases of atypical endometrial hyperplasia or endometrial cancer. Dienogest has been developed as a fourth-generation progestin for hormone therapy for endometriosis that can be used with high safety for long periods of time. In Japan, dienogest has been recommended as a first-line drug for endometriosis-associated pain. However, its antitumor activity has also been attracting close attention following a report that this drug suppressed the proliferation in vitro of endometrial cancer-derived cell lines which failed to respond to other progestins such as medroxyprogesterine acetate (MPA). The mechanism for antitumor activity of dienogest is considered to differ from the mechanism for antitumor activity of conventional progestin preparations used for treatment of endometrial cancer. This drug is expected to be clinically applicable as a new drug for the treatment of endometrial cancer.

Relationship between DNA Mismatch Repair Deficiency and Endometrial Cancer

Some cases of endometrial cancer are associated with a familial tumor and are referred to as hereditary nonpolyposis colorectal cancer (HNPCC or Lynch syndrome). Lynch syndrome is thought to be induced by germline mutation of the DNA mismatch repair (MMR) gene. An aberration in the MMR gene prevents accurate repair of base mismatches produced during DNA replication. This phenomenon can lead to an increased frequency of errors in target genes involved in carcinogenesis, resulting in cancerization of the cell. On the other hand, aberrant DNA methylation is thought to play a key role in sporadic endometrial carcinogenesis. Hypermethylation of unmethylated CpG islands in the promoter regions of cancer-related genes associated with DNA repair leads to the cell becoming cancerous. Thus, both genetic and epigenetic changes are intricately involved in the process through which cells become cancerous. In this review, we introduce the latest findings on the DNA mismatch repair pathway in endometrial cancer.

Carcinoma of the Lower Uterine Segment (LUS): Clinicopathological Characteristics and Association with Lynch Syndrome

Endometrial cancer arises from the uterine body and fundus in many cases, but can also originate from the lower region of the uterine body through the upper region of the cervix. Such tumors are referred to as carcinoma of the lower uterine segment (LUS) or isthmus, and account for 3-6.3% of all cases of endometrial cancer. This relatively low incidence has permitted performance of only small-scale studies, but the clinical and pathological characteristics of carcinoma of the LUS in all these reports have differed from those of other endometrial cancers. Generally, endometrial cancer is classified into estrogen-dependent endometrioid adenocarcinoma (designated as type I), and non-endometrioid types that are less associated with estrogen and include poorly differentiated adenocarcinoma (type II). In some reports, carcinoma of the LUS has been found to have type II characteristics. Carcinoma of the LUS has also been associated with Lynch syndrome, a hereditary disease with frequent development of colorectal, endometrial, and ovarian cancers. Lynch syndrome is thought to be induced by mismatch repair gene mutation. The frequency of Lynch syndrome in cases of general endometrial cancer is 1-2%. In contrast, the frequency in patients with carcinoma of the LUS is much higher, with up to 29% of cases diagnosable with Lynch syndrome and a high frequency of hMSH2 mutation found in one study. This suggests that further investigation of the clinical and pathological characteristics of carcinoma of the LUS and the association with Lynch syndrome is required through performance of a large-scale survey.

Endometrial cancer as a familial tumor: pathology and molecular carcinogenesis (review)

Some cases of endometrial cancer are associated with a familial tumor and are referred to as hereditary nonpolyposis colorectal cancer (HNPCC or Lynch syndrome). Such tumors are thought to be induced by germline mutation of the DNA mismatch repair (MMR) gene, but many aspects of the pathology of familial endometrial cancer are unclear and no effective screening method has been established. However, the pathology of endometrial cancer with familial tumor has been progressively clarified in recent studies. At present, about 0.5% of all cases of endometrial cancers meet the clinical diagnostic criteria for HNPCC. A recent analysis of the three MMR genes (hMLH1, hMSH2 and hMSH6) revealed germline mutations in 18 of 120 cases (15.0%) of endometrial cancer with familial accumulation of cancer or double cancer, with a frameshift mutation of the hMSH6 gene being the most common. Many cases with mutation did not meet the current clinical diagnostic criteria for HNPCC, indicating that familial endometrial cancer is often not diagnosed as HNPCC. The results suggest that the hMSH6 gene mutation may be important in carcinogenesis in endometrial cancer and germline mutations of the MMR gene may be more prevalent in cases associated with familial accumulation of cancer. An international large-scale muticenter study is required to obtain further information about the pathology of endometrial cancer as a familial tumor.

MicroRNA and endometrial cancer: Roles of small RNAs in human tumors and clinical applications (Review)

MicroRNAs (miRNAs) are small non-coding RNAs of approximately 22 base pairs that regulate the expression of genes by targeting messenger RNA with complementarity with the miRNA base sequence. Regulation of gene expression by miRNAs is crucial in cellular development and differentiation, and recent studies suggest a relationship between human diseases and the breakdown of gene silencing mechanisms induced by miRNA abnormalities. In particular, abnormal miRNA expression has been detected in various types of cancer and the target genes have been identified. These results indicate that miRNAs act in a manner equivalent to oncogenes or tumor suppressors. miRNAs may also serve as diagnostic biomarkers and therapeutic targets. In this review, we introduce the latest findings on miRNAs in human endometrial cancer, a common malignancy, and discuss the potential of miRNAs as biomarkers and targets for molecular therapy.

Analysis of candidate target genes for mononucleotide repeat mutation in microsatellite instability-high (MSI-H) endometrial cancer

Microsatellite instability (MSI) is an indicator of DNA instability and is caused by abnormalities in DNA mismatch repair (MMR) genes such as hMLH1, hMSH2 and hMSH6. MSI occurs frequently in endometrial cancer (in approximately 30% of cases), and accumulation of gene mutations due to MSI may therefore have a major role in the mechanism of malignant transformation. However, a responsible target gene has not been identified in endometrial cancer. In this study, we analyzed mutations in 11 cancer-related genes with mononucleotide repeats susceptible to MSI in a coding region [hMSH3 (A8), hMSH6 (C8), TGF-beta RII (A10), MBD4 (A10), BAX (G8), PTEN (A6 in exon 7), HDAC2 (A9), EPHB2 (A9), Caspase-5 (A10), TCF-4 (A9) and Axin2 (G7)] in 22 patients with MSI-H sporadic endometrial cancer. Mutations in hMSH6 (C8) and TGF-beta RII (A10) were found most frequently, at rates of 36.3% (8/22) each. Mutations of BAX (G8) and TCF-4 (A9), which are common in MSI-positive colorectal cancer, occurred at rates of 22.7 and 0%, respectively, which suggests that the MSI target gene may differ between endometrial and colorectal cancers. Mutations in hMSH6 (C8) were correlated with reduced protein expression (p=0.042) and patients with these mutations had significantly more mutations in mononucleotide repeats in other cancer-related genes compared to patients without hMSH6 (C8) mutations (p=0.042). This suggests the possibility of a novel cascade in carcinogenesis of endometrial cancer in which MSI mutates hMSH6 (C8), increases gene instability, and leads to accumulation of mutations in other cancer-related genes. To our knowledge, this is the first report to show that hMSH6 (C8) has an important role as an MSI target gene in sporadic endometrial cancer.

Epigenetic DNA hypermethylation: clinical applications in endometrial cancer (Review)

Improvements in epigenetics have resulted in identification of a number of genes with aberrant hypermethylation associated with systematic occurrence of cancer. It is now evident that aberrant hypermethylation inactivates cancer-related genes including those associated with cell cycle control, apoptosis, and DNA repair. An epigenetic analysis of DNA hypermethylation in type I endometrial cancer has led to a proposed mechanism for endometrial carcinogenesis. Reduced DNA mismatch repair due to loss of hMLH1 expression is thought to have a major role in carcinogenesis and these findings open up approaches to prevention, diagnosis, risk assessment, and treatment of type I endometrial cancer. Aberrant DNA hypermethylation can be detected with high sensitivity for identification of cancer cells in sputum, blood and other biopsy materials, including in endometrial cancer specimens. There have been many attempts to use methylation inhibitors as anticancer agents, and epigenetic abnormalities may be useful as biomarkers of anticancer drug sensitivity and to identify biological characteristics of tumor cells for determination of treatment options based on hypermethylation. For example, aberrant hypermethylation of the CHFR gene is correlated with cellular sensitivity to microtubule inhibitors, and this may be useful in treatment of type I endometrial cancer. An ultimate objective of epigenetics is to identify the type of hereditary methylation responsible for cancer, with the goal of improved diagnosis and treatment based on control of methylation.

Analysis of a correlation between the BRAF V600E mutation and abnormal DNA mismatch repair in patients with sporadic endometrial cancer

Point mutations of KRAS and BRAF genes are thought to be important in carcinogenesis of colon cancer. In particular, gene instability caused by decreased expression of the hMLH1 gene, a DNA mismatch repair (MMR) gene, may be linked to the activating BRAF V600E point mutation in sporadic colon cancer. However, a consensus has not been established regarding the correlation between point mutations of KRAS or BRAF and carcinogenesis in patients with endometrial cancer, which is closely related to colon cancer. Therefore, we analyzed aberrant hypermethylation of the hMLH1 gene, microsatellite instability (MSI), and point mutations of KRAS and BRAF in 44 samples of sporadic endo-metrial cancer, with the aim of examining the mechanism of carcinogenesis in patients with endometrial cancer. Aberrant hMLH1 hypermethylation was found in 17 of the 44 cases (38.6%) and showed a significant positive correlation with MSI (p=0.02). This suggests that an abnormal MMR mechanism plays an important role in carcinogenesis of sporadic endometrial cancer. Point mutation of KRAS was found in 6 of the 44 cases (13.6%), but no BRAF V600E mutation was detected. These data suggest that the BRAF V600E mutation is not the target gene for abnormal MMR in carcinogenesis in patients with sporadic endometrial cancer, unlike in colon cancer. This is supported by the relatively few previous reports indicating a correlation between endometrial cancer and the BRAF V600E mutation. Identification of new candidates for the target gene for abnormal MMR in endometrial cancer requires further work.

Epigenetic inactivation of the CHFR gene in cervical cancer contributes to sensitivity to taxanes

A relationship between inactivation of mitotic checkpoint genes and sensitivity of cancer cells to anticancer agents has been reported. We investigated the effect of epigenetic inactivation by aberrant hypermethylation of the mitotic checkpoint gene CHFR (checkpoint with forkhead and ring finger) on the sensitivity of cervical cancer cells to taxanes. Methylation-specific PCR (MSP) of cervical smears showed aberrant methylation of CHFR in 12.3% (2/14) of adenocarcinoma specimens. In contrast, aberrant DNA methylation was not detected in normal cervical cells or squamous cell carcinoma cells. Aberrant methylation of CHFR was also analyzed in 6 human cervical carcinoma-derived cell lines and was observed in SKG-IIIb and HeLa cells. These cell lines showed high sensitivity to taxanes, but became taxane-resistant upon treatment with 5-azacytidine. Furthermore, suppression of CHFR expression in siRNA-transfected SKG-IIIa cells caused increased sensitivity to taxanes. In conclusion, aberrant methylation of the CHFR gene may be useful as a molecular marker for selection of therapy for patients with cervical adenocarcinoma with a poor prognosis, and may also suggest a new therapeutic strategy of targeting CHFR in cervical cancer. To our knowledge, this study is the first to examine epigenetic inactivation by aberrant hypermethylation of CHFR in cervical cancer.

Relationship of aberrant DNA hypermethylation of CHFR with sensitivity to taxanes in endometrial cancer

The relationship of aberrant DNA hypermethylation of cell cycle checkpoint genes with the sensitivity of cancer cells to anticancer drugs is a question of current interest. In this study, we investigated the relationship between aberrant hypermethylation of the CHFR (checkpoint with forkhead-associated and ring finger) mitotic checkpoint gene and sensitivity to taxanes in endometrial cancer. Methylation-specific PCR (MSP) indicated aberrant hypermethylation of CHFR in 12.0% (6/50) of endometrial cancer specimens, and suggested that aberrant hypermethylation is significantly more frequent in poorly differentiated adenocarcinoma (G3) (p<0.05). Of six culture cell lines, SNG-II and HEC108 cells showed aberrant hypermethylation and reduced expression of CHFR. These cells had high sensitivity to taxanes but became resistant after demethylation. Cancer specimens with aberrant hypermethylation of CHFR also exhibited high sensitivity to taxanes. To our knowledge, this study is the first to examine aberrant hypermethylation of CHFR in endometrial cancer, and our results suggest that the methylation status of CHFR may be a new molecular index that will allow design of personalized treatment in endometrial cancer. This may be particularly important in poorly differentiated adenocarcinoma (G3), which is known to have a poor prognosis.