Elucidation of the developmental mechanism of ovarian mature cystic teratomas using B allele-frequency plots of single nucleotide polymorphism array data.

Ovarian mature cystic teratomas (MCTs) originate from post-meiotic germ cells. Conventional methods such as karyotyping or short tandem repeat-polymorphism analysis may be used to better classify MCTs, although such data would be insufficient. The aim of this study was to elucidate the origin of ovarian MCTs using B allele-frequency (BAF) plots of single nucleotide polymorphism array data. MCTs can be classified in terms of the zygosity of the centromeres and distal chromosome regions. We evaluated the zygosity of all chromosomes from 38 MCT specimens using BAF plot data. BAF plots were used to determine the homozygous and heterozygous regions over the whole genome. Theoretically, MCTs originated from the fusion of two ova (previously referred to as type V MCTs) should have a mixed pattern of centromeric zygosity, that is, a combination of heterozygous and homozygous regions in the centromeric regions. However, no MCTs in this study met this criterion. We identified 13 type I MCTs, 14 type II MCTs, and 11 type III MCTs. In addition, BAF plots facilitated the construction of recombination maps at the whole-genome level for type I and II MCTs. No crossover, especially in the short arms, contributed to the failure of meiosis I, resulting in type I MCTs. Crossover in all arms might assure the normal progress of meiosis in human oocytes. In conclusion, our findings indicate that BAF plots can elucidate the developmental mechanism of MCTs, and further serve as useful analytical tools for analyzing human oocyte meiosis, and related aberrations.

Presence of the methylenetetrahydrofolate reductase gene polymorphism MTHFR C677T in molar tissue but not maternal blood predicts failure of methotrexate treatment for low-risk gestational trophoblastic neoplasia.

Gestational trophoblastic neoplasia (GTN) is a rare tumor, and its genomic constitution is different from the maternal genome because of its gestational origin. Methotrexate (MTX) is a standard chemotherapeutic agent for low-risk GTN. An association between polymorphisms of the methylenetetrahydrofolate reductase (MTHFR) gene and MTX treatment outcome has been reported in various diseases. Thus, we examined the association between clinical outcome and MTHFR polymorphisms in both tumor and blood DNA of low-risk GTN patients. MTHFR C677T (rs1801133) and A1298C (rs1801131) were genotyped using high-resolution melting assays in 62 Japanese low-risk GTN patients and in 52 antecedent molar tissues. We compared the genotypes of MTHFR polymorphisms with the clinical outcome of 5-day MTX treatment. Twenty-five patients entered remission and 37 patients developed drug resistance or adverse effects that necessitated a drug change. The MTHFR 677T allele in molar tissue was significantly related to the need for drug change (P=0.006; odds ratio [OR], 3.13; 95% confidence interval [CI], 1.31-7.49), in contrast to MTHFR 1298C (P=0.18; OR, 0.63; 95% CI, 0.32-1.25). The MTHFR 677T and 1298C alleles obtained from patients' blood DNA were not related to MTX treatment outcome (P=0.49; OR 1.31; 95% CI, 0.61-2.91 and P=0.10; OR 0.52; 95% CI, 0.22-1.15, respectively). These data demonstrate for the first time that the genotype of MTHFR 677TT in molar tissue is associated with ineffective MTX treatment in Japanese low-risk GTN patients.

Mature cystic teratomas arise from meiotic oocytes, but not from pre-meiotic oogonia.

Mature cystic teratomas (MCTs) in the ovaries have been thought to originate from germ cells from all developmental stages, i.e., from pre-meiotic oogonia through meiotic oocytes to mature post-meiotic ova. This view was based on research on MCTs by classical methods, including those involving centromeric heteromorphisms in karyotypes, enzyme polymorphisms, and DNA polymorphisms. However, insufficient genomic information was obtained in those studies. The current study aimed to confirm the cytogenetic origin of ovarian MCTs by using short tandem repeat (STR) polymorphism analysis to obtain sufficient genomic information, especially in connection with centromeric loci. Tissue samples of MCTs (57 ovaries from 51 patients, 91 MCTs, 156 specimens in total) obtained from cystectomies or oophorectomies were used. We categorized the specimens into two groups: i) solid components of MCTs and ii) cyst walls. The numbers of solid components of MCTs from pre-meiotic oogonia, primary oocytes, secondary oocytes, and ova were 0, 33, 16, and 15, respectively. There were no pre-meiotic oogonia in this series of solid-component specimens. We propose a hypothesis for the tumorigenesis of ovarian MCTs: the precursors of ovarian MCTs are not functional oocytes or ova, but are primary oocytes that have escaped from meiotic arrest. This hypothesis could satisfactorily explain the lack of pre-meiotic teratomas observed in this study and the nearly equal distribution of teratomas originating from primary oocytes, secondary oocytes, and ova in previous studies. Furthermore, this hypothesis could provide a starting point for determining the mechanism underlying tumorigenesis of ovarian MCTs.

Molecular distinction of consecutive molar pregnancies.

BACKGROUND: It may be difficult to differentiate the consecutive occurrence of two independent molar pregnancies from gestational trophoblastic neoplasia after the initial molar pregnancy, especially when the interval between them is short. CASE: A 25-year-woman who had had a complete hydatidiform mole 6 months earlier presented with a 6-week history of secondary amenorrhea. Serum human chorionic gonadotropin had increased to 19,857 micro-international units/mL, with no gestational sac demonstrated. Dilation and curettage was performed. Pathologic examination identified a tiny amount of hydropic villi compatible with complete hydatidiform mole. Analysis of short tandem repeat polymorphisms revealed that the molar tissues of the first and second complete hydatidiform moles were of different genetic origin. The patient went into remission spontaneously without chemotherapy. CONCLUSION: Genetic profiling was useful to discriminate a recurrent mole from suspected gestational trophoblastic neoplasia.

Tamoxifen and the risk of endometrial cancer in Japanese women with breast cancer.

PURPOSE: There is ongoing debate about whether tamoxifen for breast cancer is associated with a risk of endometrial cancer in Japanese women. We conducted a study to investigate this further. METHODS: We conducted a retrospective hospital-based cohort study. A total of 674 consecutive patients underwent surgery for primary breast cancer between January 1989 and December 1998. By December 2003, endometrial cancers had been diagnosed in six of these patients. Based on medical records, we evaluated the potential risk factors for endometrial cancer, including age, menopausal status, obesity, parity, diabetes mellitus, hypertension, and tamoxifen. The 674 patients were divided into three groups based on the cumulative duration of tamoxifen use (A, <2 years vs B, 2-5 years vs C, >5 years). To examine the relationships between endometrial cancer and tamoxifen (and other factors), the hazards ratio (HR), 95% confidence interval (CI), and two-sided P value for endometrial cancer associated with each variable were calculated by the Cox regression method. RESULTS: Endometrial cancer was found in 1/318 (0.31%) patients in group A, 3/247 in group B, and 2/109 in group C. In a multivariate analysis no variable was significant, but tamoxifen use for longer than 5 years (group C) was closely correlated with endometrial cancer (HR = 7.92, CI = 0.69-90.89, P = 0.096). CONCLUSION: Although our data did not reach significance, they support a link between long-term tamoxifen and the development of endometrial cancer in Japanese women with breast cancer.