[G-banded chromosomes of peripheral blood from both trophoblastic tumor patients and their husbands]

The G-banded chromosomes of peripheral blood from 55 patients with clinically and/or pathologically diagnosed trophoblastic tumors, husbands of 45 patients with the disease and 181 female and male normal controls were analyzed. Loss of chromosome 22, sporadic translocation of chromosome 7; 14 and low percentage mosaicism of sex chromosomes were noted. Significantly increased frequencies of the latter two abnormalities as well as another one, pericentric inversion of chromosome 9, were detected in both the patient and the husband groups, suggesting that these chromosome abnormalities might be causal factors of trophoblastic tumors.

Relaxation of imprinting in trophoblastic disease

Genomic imprinting--the uniparental-dependent transmittance of a genetic trait--has been accepted in recent years as a major mechanism in mammalian genetics. We studied the expression of the H19 gene, a parentally imprinted (maternally expressed) gene, by in situ hybridization in human placenta and trophoblastic disease. Expression was found to be abundant, in a decreasing order, in the intermediate trophoblast (villous and interstitial), the cytotrophoblast, and the syncytiotrophoblast. The villous stroma was also prominently labeled. Partial hydatidiform mole showed a similar pattern of expression as normal placenta. As expected, complete hydatidiform mole, whose genome consists of two haploid sets of paternal origin, was not labeled in the villous stroma and surrounding trophoblastic layer. However, some of the large mononuclear cells in the proliferating groups sprouting from the villous surface were strongly labeled. Prominent expression of H19 was found in placental site trophoblastic tumor and gestational choriocarcinoma. The phenomenon of emergence of expression of alleles subject to repression according to their gamete of origin is termed relaxation of imprinting, and is considered to be relevant to tumorigenesis. We suggest that the expression of the maternally expressed H19 gene in the androgenetic tissue of complete hydatidiform mole represents relaxation of imprinting and may be associated with its malignant potential.

Genomic imprinting--defusing the ovarian time bomb

Why do mammals imprint their parental genomes? Imprinting is seen in many phyla, but that in mammals is by far the most dramatic. Is there something peculiar to mammals that calls for such a striking phenomenon? We propose that imprinting is a device that protects female mammals from the potential ravages of ovarian trophoblast disease. Without imprinting, the ovarian teratomas that frequently arise from parthenogenetically activated oocytes in situ might be capable of forming malignant trophoblast. An allele that favored imprinting would spread rapidly because of the great increase in fitness associated with suppressing a lethal cancer of females.

Human imprinted genes as oncodevelopmental markers

Imprinted genes mediate unique maternal or paternal genetic roles and their function is essential in prenatal development. The reciprocally imprinted human insulin-like growth factor 2 (IGF2) and H19 genes are expressed during embryonal life, also in the placenta, and are downregulated postnatally. They reexpress in pediatric tumors (e.g. Wilms' tumor) and in inborn developmental syndromes predisposing to such tumors (e.g., Beckwith-Wiedemann syndrome). H19 (RNA transcripts) and IGF2 are manifested in Wilms' tumor, rhabdomyosarcoma, immature ovarian teratoma and gestational trophoblastic diseases. We have found that in the placenta and in urothelial carcinoma, H19 expression reflects the degree of invasiveness. These genes, displaying a tissue-specific oncofetal pattern of expression, are, therefore, tumor markers.

Cell proliferative activity and mutation of P53 suppressor gene in human gestational trophoblastic disease

Cell proliferative activity and the overaccumulation of P53 suppressor gene were evaluated in 26 cases of gestational trophoblastic disease and five cases with normal placentae. Formalin-fixed, paraffin-embedded histological sections were used for immunohistochemistry, utilizing the avidin-biotin-peroxidase technique and antibodies to PCNA (proliferative cell nuclear antigen) and to P53 (product of suppressor gene). Positive reactions for PCNA were graded from 1+ to 3+ (1(+)-less than 10% of cells; 2(+)-10-50%; 3(+)-more than 50%). Eight of 10 cases of choriocarcinoma (80%) showed moderate to strong reactivity for PCNA (2+ and 3+). All 9 cases with hydatidiform mole and 6 of 7 cases with partial mole also demonstrated 2+ and 3+ reactions for PCNA. There was minimal or no PCNA staining in the trophoblastic cells of normal placentae. Five of 10 cases with choriocarcinoma (50%) exhibited P53 overaccumulation as did 7 of 9 cases with hydatidiform mole (78%). In hydatidiform moles, P53 staining was limited to the areas of trophoblastic proliferation separate from chorionic villi. None of the partial moles or normal placentae showed P53 overaccumulation. It is concluded that the cell proliferative activity of choriocarcinomas as well as complete and partial hydatidiform moles are comparable. On the other hand, the mutation of P53 suppressor gene, as demonstrated by the overaccumulation of P53 protein, is seen only in true trophoblastic neoplasms, namely, choriocarcinomas and hydatidiform moles.

Malignant trophoblastic tumors: immunohistochemical and flow cytometric comparison of choriocarcinoma and placental site trophoblastic tumors

We performed an immunohistochemical and flow cytometric study of the formalin-fixed, paraffin-embedded tissues of eight recent gestational choriocarcinomas (CCs) and three placental-site trophoblastic tumors (PSTTs). The follow-up period ranged from 1 to 144 months (mean, 74.3 months). In the CCs, which consisted predominantly of cytotrophoblasts and syncytiotrophoblasts intermingled with small amounts of intermediate trophoblasts, cytotrophoblasts were occasionally positive for beta-subunit human chorionic gonadotropin (HCG) and syncytiotrophoblasts contained abundant HCG. Some intermediate trophoblasts were positive for HCG and many were positive for human placental lactogen. In the three PSTTs, which were characterized by a monomorphic proliferation of intermediate trophoblasts, the tumor cells were positive for human placental lactogen and placental alkaline phosphatase. The tumors of two patients, including one fatal case, contained more human placental lactogen-positive cells than HCG-positive cells, while the tumor of the remaining patient, who had high serum HCG levels, showed a reversed staining pattern resembling that of CC; this patient has been alive without disease for 9 years. One CC patient and one PSTT patient died of multiple lung metastases, despite hysterectomy and multiagent chemotherapy. All CCs and PSTTs had an exclusively diploid DNA content, and there was no correlation among histopathologic and immunohistochemical features, DNA ploidy, S-phase fraction, and clinical outcome for patients with these tumors. These results suggest that there is a PSTT that immunohistochemically resembles CC and that flow cytometric and immunohistochemical analysis may not be effective tools to predict the biologic behavior of malignant trophoblastic tumors.

Identification of the pregnancy responsible for gestational trophoblastic disease by DNA analysis

In three cases of choriocarcinoma, genetic loci including a variable number of tandem repeat regions were amplified by the polymerase chain reaction method on DNA from three established cell lines and from lymphocytes of patients and their husbands to identify the responsible pregnancy. Case 1, from whom NaUCC-3 was derived, had only one full-term fetal death. Case 2, from whom NaUCC-4 was derived, had one normal delivery followed by one complete molar delivery and one normal delivery. Case 3, from whom NaUCC-2 was derived, had one normal delivery followed by one complete molar delivery. In case 1, NaUCC-3 was found to be of parental origin and derived from the pregnancy with full-term fetal death. In cases 2 and 3, NaUCC-4 and NaUCC-2 were of probable androgenetic origin and were derived from the pregnancy with complete hydatidiform mole. We also conducted the restriction fragment length polymorphism method using case 1 samples, and it confirmed the results based on the polymerase chain reaction method product patterns. All nine cases of hydatidiform mole and three cases of invasive mole were of androgenetic origin. The polymerase chain reaction method thus makes it possible to identify easily the pregnancy responsible for choriocarcinoma using only a few specimens without isotopes.

Metastasizing placental site trophoblastic tumor. An immunohistochemical and flow cytometric study of two cases

An immunohistochemical and flow cytometric DNA study of two cases of metastasizing placental site trophoblastic tumor are presented. One patient aged 29 died rapidly of widespread metastases despite hysterectomy and multiagent chemotherapy. The patient had a low level of serum HCG. The course was complicated by the presence of a nephrotic syndrome. The other patient aged 34 had a vaginal metastasis and high levels of serum HCG, and was alive without disease for 9 years after hysterectomy and chemotherapy. Histologically, these tumors were characterized by a monomorphic trophoblastic cell population, probably derived from intermediate trophoblast in the placental site. The mitotic rate in these tumors was 2-4/10 high-power fields. Immunohistochemically, many tumor cells contained human placental lactogen and placental alkaline phosphatase. Beta-unit chorionic gonadotropin was present in many cells of the second patient, and only focally in the first. All specimens including the curettaged and metastatic lesions revealed a diploid DNA content in both cases. Neither DNA ploidy nor S-phase fraction was associated with survival of patient. Since predicting the biologic behavior of placental site trophoblastic tumor is very difficult, making a correct diagnosis on endometrial curettings, hysterectomy, and monitoring serum HCG level is essential in patients with this tumor.

Gestational and non-gestational trophoblastic neoplasms: new developments in DNA analysis, metabolic function, diagnosis and treatment

Recent technological advances have made it possible to further define important molecular biological characteristics of gestational and non-gestational trophoblast neoplasm, as they relate to genetic origin and metabolic, endocrine, and diagnostic functions. Exciting new work with DNA analysis has defined origins of placental site trophoblastic tumors, a variant of choriocarcinoma not previously well understood. Coexistent hydatidiform mole and normal gestation have been diagnostically defined and carried out to viability. Finally, refinement of classification systems and expanded tumor markers offer promise of improved salvage in gestational neoplasms and an enlarging number of non-gestational neoplasms.

Flow cytometric DNA analysis of placental-site trophoblastic tumors

The placental-site trophoblastic tumor is a rare form of gestational trophoblastic neoplasia. Although originally considered benign, it is now apparent that this lesion can be associated with aggressive clinical behavior. Our study examined the DNA ploidy status and clinicopathologic features of four new cases of placental-site trophoblastic tumor. Three cases demonstrated diploid DNA stemlines with S-phase fractions ranging from 6% to 16%. These patients were alive and well at follow-up and had low-serum human chorionic gonadotrophin (hCG) levels. A fourth patient, who had a large tumor, demonstrated a tetraploid DNA peak with a prominent S-phase fraction. This patient exhibited an elevated serum hCG at limited follow-up. Flow cytometric DNA analysis may be a useful adjunct for the identification of placental-site trophoblastic tumors with malignant potential.

The immune system in disease: gestational trophoblastic tumours

Trophoblastic tumours form a spectrum of disease from the borderline malignancy of HM to highly aggressive choriocarcinoma. Their management requires the integration of the information derived from serial hCG estimations, the clinical history and pattern of spread of the disease, so that our understanding of the prognostic variables can be applied appropriately. This maximizes the patient's chances of complete remission from her disease with the minimum of toxicity. Given our knowledge of this group of diseases and an integrated approach to management, it should be uncommon for any woman to die from her trophoblastic tumour.

[Sister chromatid exchanges in lymphocytes of patients with gynecological malignancies]

The frequency of SCE in the peripheral blood lymphocytes of 30 patients with gynecological malignancies was investigated. The frequency of SCE was found to be 5.37 +/- 0.44, 5.30 +/- 0.35 and 3.76 +/- 0.38 respectively in the patients before and after chemotherapy and in the control cases. The SCE values deviated significantly from those of control, and were not related to the staging of the tumor. The study suggested the possibility of utilizing SCE as a cytogenetic indicator in some malignant tumors.

Gestational trophoblastic diseases: recent advances in the understanding of cytogenetics, histopathology, and natural history

Our understanding of gestational trophoblastic diseases has progressed considerably in recent years in terms of our knowledge of their cytogenetic origin, histopathology, and natural history. Advances in molecular biology have been applied to the study of gestational trophoblastic diseases, providing new insights into their pathogenesis. Molecular biologic studies have now clearly demonstrated that complete molar pregnancies result from fertilization of an anuclear, "empty" ovum. Improved understanding of the cytogenetics and biology of gestational trophoblastic diseases may well contribute to further advances in patient care.

Flow cytometric diagnosis of partial mole

To differentiate histologically partial hydatidiform moles (PM) and complete hydatidiform moles (CM) may be difficult. Cytogenetic studies have shown that PMs often had a triploid karyotype while CMs were always diploid. We assessed the DNA content of 31 paraffin-embedded cases of trophoblastic disease with flow cytometry. Twenty-four cases were histologically diagnosed as PM, 3 cases as CM; the others as hydropic abortion (2 cases), choriocarcinoma (1 case), and persistent trophoblastic disease (1 case). Four normal term placentas were used as diploidy controls. In 9 cases the results of the cytogenetic analysis were available. All placental specimens included also maternal tissue as an internal control. Eight of the 24 histologically diagnosed PMs were triploid; there was agreement in 8 cases out of 9 (90%) between the flow cytometric analysis and the karyotypic determination of ploidy. All normal controls as well as the hydropic abortion, the CM and the persistent trophoblastic disease were diploid. Abnormal content of DNA (DI = 1.3) was observed in the choriocarcinoma. Our results show that flow cytometric analysis of DNA content is a reliable and fast method of diagnosing PM on paraffin-embedded material.

Genetic evidence that placental site trophoblastic tumours can originate from a hydatidiform mole or a normal conceptus

The genetic origin of two placental site trophoblastic tumours was established using a Y chromosome-specific and locus-specific minisatellite probes. A gestational origin was confirmed for both tumours. In one case the origin of the tumour was consistent with derivation from a normal female conceptus while the other was shown to arise from a homozygous complete hydatidiform mole, an abnormal conceptus more usually associated with the development of choriocarcinoma.

[Biology of the trophoblastic tissue and placental tumors]

The trophoblast of early placenta has many attributes of malignant tissue: it displays highly proliferative and invasive properties and expresses hormones, growth factors, growth factor receptors and oncogene products. Moreover, this tissue may have an autocrine control of growth. Collectively, these properties are similar to those of malignant tissues and the normal trophoblast is then considered as a "pseudomalignant" tissue. Moreover, either benign (hydatidiform mole) or malignant (choriocarcinoma) trophoblastic disease may be developed from the trophoblastic cells. In this article, the biological features of both the normal and the tumoral trophoblast will be presented. Finally, the trophoblast is a model and a source of molecules of biological interest.

[Flow cytometric analysis of trophoblastic tumors]

19 cases of malignant trophoblastic tumors were studied by flow cytometry in comparison with 9 cases of benign hydatidiform mole that had been followed up for 1.5 years with no history of malignancy. The results showed that there were significant differences in DNA index (DI), S phase of cells and the pattern of ploidies between the malignant trophoblastic tumor and benign hydatidiform mole. It is considered that flow cytometry is a useful parameter in reference to the diagnosis, chemotherapy and assessing prognosis of malignant trophoblastic tumor.

Expression and amplification of cellular oncogenes in human developing placenta and neoplastic trophoblastic tissue

To confirm the expression of cellular oncogenes during normal development, their differential RNA levels in developing human placenta have been studied using radioactive probes such as v-abl, v-erbA, v-fms, v-mos, v-myc, N-ras and v-src. The c-mos and N-ras genes are expressed and amplified at high levels especially in term placenta, while c-abl, and c-erbA are expressed constantly during development. These findings indicate that c-mos and N-ras genes may be closely linked to normal differentiation, although c-abl and c-erbA may participate in overall developmental processes. In contrast, transcripts of c-myc and c-src are enhanced at first trimester and decreased sequentially thereafter, showing that these genes may play a role in early proliferation. Expression patterns of c-fms gene are same as that of c-myc and c-src except reelevation at term. In addition, to characterize the effect of cellular oncogene expression has been also examined in hydatidiform mole and tumor cells such as BeWo and choriocarcinoma. All cellular oncogenes examined in this study were significantly overexpressed. Thus, our results suggest that cellular oncogene activation may be strongly associated with neoplastic change of trophoblast.

Gestational and nongestational trophoblastic tumors distinguished by DNA analysis

In three patients in whom a diagnosis of gestational trophoblastic tumor was possible on the basis of pathology and elevated levels of serum human chorionic gonadotrophin, locus-specific minisatellite probes were used to identify restriction fragment length polymorphisms (RFLP) in DNA from the tumor, the patient, and her partner. On the basis of results from these studies, one tumor, originally diagnosed as a germ cell tumor, was reclassified as a gestational choriocarcinoma, whereas a second tumor, diagnosed as gestational choriocarcinoma, was shown to be of nongestational origin. In the third case, a diagnosis of gestational trophoblastic tumor was confirmed, but in this case the androgenetic origin of the tumor indicated that it was derived, not from the antecedent term pregnancy, but from a previous pregnancy with hydatidiform mole. This study clearly demonstrates the value of DNA analysis in the classification of tumors with trophoblastic differentiation.

Flow cytometric analysis of DNA content in partial hydatidiform moles with persistent gestational trophoblastic tumor

Hydatidiform moles may be classified as partial or complete based on genetic and pathologic criteria. Between January 1979 and January 1990, 17 (5.5%) of 310 patients followed for partial mole developed persistent gestational trophoblastic tumor. Tissues from 14 partial moles were available for flow cytometric analysis of DNA content. Eleven partial moles (85%) were triploid, two (15%) were diploid, and one DNA histogram was uninterpretable. All patients with triploid partial moles achieved complete remission with one course of single-agent chemotherapy. The two with diploid partial mole required multiple courses of chemotherapy to achieve gonadotropin remission. Although the DNA content of most partial moles with persistent gestational trophoblastic tumor was triploid, diploid partial moles with persistent tumor were less sensitive to single-agent chemotherapy.

Evolving concepts of molar pregnancy

Molar pregnancy is composed of two distinct clinical and pathologic entities, complete and partial mole. Knowledge of the cytogenetic origin, natural history and treatment of complete and partial hydatidiform mole is evolving.

Human chorionic gonadotropin, its free subunits and gestational trophoblastic disease

Monoclonal antibody-based immunoassays can detect specifically intact human chorionic gonadotropin (hCG), the free alpha-subunit and the free beta-subunit. The differential production of hCG and its free subunits is important in gestational trophoblastic disease. Using well-defined epitope-specific monoclonal antibodies in an immunoradiometric assay format, specific and sensitive assays have been developed. Serum levels of free beta-hCG were abnormally high in patients with gestational trophoblastic disease. In contrast, free alpha-hCG levels in serum were not increased.