HLA-G immunoreactivity is specific for intermediate trophoblast in gestational trophoblastic disease and can serve as a useful marker in differential diagnosis

Aberrant trophoblastic differentiation in human cancer: An emerging novel therapeutic target (Review)

Various types of human cancer may develop aberrant trophoblastic differentiation, including histological changes and altered expression of β‑human chorionic gonadotropin (β‑hCG). Aberrant trophoblastic differentiation in epithelial cancer is usually associated with poor differentiation, tumor metastasis, unfavorable prognosis and treatment resistance. Since β‑hCG‑targeting vaccines have failed in an early phase II trial, it is crucial to obtain a better understanding of the molecular pathogenesis of trophoblastic differentiation in human cancer. The present review summarizes the clinical and translational research on this topic with the aim of accelerating the development of an effective targeted therapy. Ectopic expression of β‑hCG promotes proliferation, migration, invasion, vasculogenesis and epithelial‑mesenchymal transition (EMT) in vitro, and enhances metastatic and tumorigenic capabilities in vivo. Signaling cascades modulated by β‑hCG include the TGF‑β receptor pathway, EMT‑related pathways, the c‑MET receptor tyrosine kinase and mitogen‑activated protein kinase/ERK pathways, and the SMAD2/4 pathway. Taken together, these findings indicated that TGF‑β receptors, c‑MET and ERK1/2 are potential therapeutic targets. Nevertheless, further investigation on the molecular basis of aberrant trophoblastic differentiation is mandatory to improve the design of precision therapy for this aggressive type of human cancer.

Extrauterine epithelioid trophoblastic tumour and its somatic carcinoma mimics: short tandem repeat genotyping meets the diagnostic challenges

AIMS

While epithelioid trophoblastic tumour (ETT) primarily arises from the uterus, cases have been increasingly documented at extrauterine sites, originating from an ectopic gestation or presenting as a metastatic tumour, leading to the major differential diagnosis of somatic carcinoma with trophoblastic differentiation. The precise separation of a gestational trophoblastic tumour from its somatic carcinoma mimics is highly relevant and crucial for patient management and prognosis.

METHODS AND RESULTS

We summarise the clinicopathological and molecular features of four challenging epithelioid malignancies presenting at extrauterine sites, with ETT as the main differential diagnosis. All four tumours demonstrated histological and immunohistochemical features overlapping between a somatic carcinoma and an ETT, combined with inconclusive clinical and imaging findings. Serum beta-hCG elevation was documented in two cases. Short tandem repeat (STR) genotyping was performed and was informative in all cases. The presence of a unique paternal allelic pattern in the tumour tissue confirmed the diagnosis of ETT in two cases with an initial consideration of either somatic carcinoma or suspicion of a gestational trophoblastic tumour. The presence of matching genetic profile with the patient's paired normal tissue was seen in two other cases (both initially considered as ETT), confirming their somatic origin, including one metastatic triple-negative breast carcinoma and one primary lung carcinoma.

CONCLUSIONS

Diagnostic separation of ETT at an extrauterine site from its somatic carcinoma mimics can be difficult at the histological and immunohistochemical levels. STR genotyping offers a robust ancillary tool that precisely separates ETT from somatic carcinomas with trophoblastic differentiation.

Gestational choriocarcinoma

Gestational choriocarcinoma accounts for 5% of gestational trophoblastic neoplasms. Approximately 50%, 25%, and 25% of gestational choriocarcinoma occur after molar pregnancies, term pregnancies, and other gestational events, respectively. The FIGO scoring system categorizes patients into low (score 0 to 6) and high risk (score 7 or more) choriocarcinoma. Single-agent and multi-agent chemotherapy are used in low- and high-risk patients, respectively. Chemotherapy for localized disease has a goal of eradication of disease without surgery and is associated with favorable prognosis and fertility preservation. Most patients with gestational choriocarcinoma are cured with chemotherapy; however, some (<5.0%) will die as a result of multi-drug resistance, underscoring the need for novel approaches in this group of patients. Although there are limited data due to its rarity, the treatment response with immunotherapy is high, ranging between 50-70%. Novel combinations of immune checkpoint inhibitors with targeted therapies (including VEGFR-2 inhibitors) are under evaluation. PD-L1 inhibitors are considered a potential important opportunity for chemo-resistant patients, and to replace or de-escalate chemotherapy to avoid or minimize chemotherapy toxicity. In this review, the Rare Tumor Working Group and the European Organization for Research and Treatment of Cancer evaluated the current landscape and further perspective in the management of patients diagnosed with gestational choriocarcinoma.

HLA-G and Recurrent Pregnancy Loss

Placentation is an immunological compromise where maternal immune system cells and trophoblastic cells interact to reach an equilibrium condition. Although the cross talk between the two systems is complex and not completely understood, Human Leukocyte Antigen G (HLA-G), expressed on trophoblastic cell surfaces, seems to be one of the main molecules involved in the modulation of both local and systemic maternal immune response. The prevalence of recurrent pregnancy loss (RPL), probably underestimated, is 5% of all women who achieve pregnancy, and about 40-60% percent of RPL cases are unexplained. There is an immunological analogy between allograft rejection and miscarriage, and the purpose of this review is to describe how the HLA-G pathway alterations are involved in disrupting the immunologic balance and in increasing the risk of recurrent pregnancy loss.

Transcriptomic and immunohistochemical approaches identify HLA-G as a predictive biomarker of gestational choriocarcinoma resistance to monochemotherapy

OBJECTIVE

Using a transcriptional approach on tissue samples, we sought to identify predictive biomarkers of post molar malignant transformation, and of choriocarcinoma chemosensitivity to mono- (methotrexate or actinomycin D) or polychemotherapy [EMA(Etoposide, Methotrexate, Actinomycin D)-CO(Cyclophosphamide, Vincristine) and EMA-EP(Etoposide, Cisplatine)] regimens.

METHODS

We studied the expression of a 760-gene panel (PanCancer Pathway) related to oncogenesis and immune tolerance in tissue samples of complete hydatidiform moles and gestational choriocarcinoma.

RESULTS

We did not identify any differentially expressed gene between moles with post molar malignant transformation in choriocarcinoma (n = 14) and moles with remission (n = 20). In monochemoresistant choriocarcinoma (n = 34), four genes (HLA-G, COL27A1, IL1R2 and GLI3) had a significantly reduced expression and one (THEM4) had an increased expression [FDR (false discovery rate) adjusted p-value ≤ 0.05] when compared to monochemosensitive choriocarcinoma (n = 9). The proportion of trophoblast cells and the intensity of immunohistochemical HLA-G expression were reduced in monochemoresistant choriocarcinoma (p < 0.05). In polychemoresistant choriocarcinoma (n = 20) we did not identify differentially expressed genes with an FDR adjusted p-value ≤ 0.05 when compared to polychemosensitive choriocarcinoma (n = 15). Gene pathway analysis revealed a predicted activation of IFN ᵞ in monochemoresistant choriocarcinoma and inhibited IL2 and TNF in polychemoresistant choriocarcinoma. The main biological functions predicted to be altered in chemoresistant choriocarcinoma were related to immunological homeostasis and leukopoiesis.

CONCLUSION

HLA-G is a strong candidate gene to predict choriocarcinoma resistance to monochemotherapy and that further studies are required to implement its routine quantification in the decision process for the management of gestational choriocarcinoma.

Epithelioid Trophoblastic Tumor: Expanding the Clinicopathologic Spectrum of a Rare Malignancy

Epithelioid trophoblastic tumor is a malignancy derived from the chorionic laeve-type intermediate trophoblast with sufficient rarity that the vast majority of literature on the topic exists in the form of case reports and small series. Classically, it is regarded as a well-circumscribed tumor with an expansile growth pattern that occurs in reproductive-aged women, usually after a normal pregnancy. However, we recently encountered a case of epithelioid trophoblastic tumor with aggressive spread throughout the abdomen and pelvis in a 68-yr-old female presenting 30 yr after her last delivery. Although to our knowledge this is the first report in a postmenopausal patient to be confirmed by molecular analysis of short tandem repeats, there are multiple similar case reports spanning a variety of clinical settings that deviate from the original description. We therefore sought to synthesize the clinicopathologic data among the available reports in the English literature, with emphasis on pathologic findings. While the overarching themes are largely unchanged, this series of 77 patients reveals a broader spectrum of disease and highlights frequent misdiagnosis. Here we present a clinicopathologic update on this rare entity, with emphasis on a practical approach to diagnosis.

A Review on the Pathogenesis and Clinical Management of Placental Site Trophoblastic Tumors

Placental site trophoblastic tumor (PSTT) is a rare type of gestational trophoblastic disease originating from the intermediate trophoblast. Compared with hydatidiform mole, invasive hydatidiform mole and choriocarcinoma, the diagnosis of PSTT is more complicated and lacks specific and sensitive tumor markers. Most PSTT patients demonstrate malignant potential, and the primary treatment of PSTT is hysterectomy. However, metastasis occasionally occurs and even causes death in a small number of PSTT patients. Most PSTT patients are young women hence fertility preservation is an important consideration. The major obstacle for PSTT patient prognosis is chemotherapy resistance. However, the current understanding of the pathogenesis of PSTT and clinical treatment remains elusive. In this review, we summarized the research progress of PSTT in recent years from three aspects: mechanism, clinical presentation, and treatment and prognosis. Well-conducted multi-center studies with sufficient sample sizes are of great importance to better examine the pathological progress and evaluate the prognosis of PSTT patients, so as to develop prevention and early detection programs, as well as novel treatment strategies, and finally improve prognosis for PSTT patients.

Gestational Trophoblastic Tumors: A Timely Review of Diagnostic Pathology

CONTEXT.—

Gestational trophoblastic tumors include 3 distinct entities: gestational choriocarcinoma, placental site trophoblastic tumor, and epithelioid trophoblastic tumor. Accurate diagnosis is important for clinical management of the patient.

OBJECTIVE.—

To review clinical features and pathologic diagnosis of gestational trophoblastic tumors.

DATA SOURCES.—

Literature and personal experience are the sources for this study.

CONCLUSIONS.—

Trophoblastic tumors are rare encounters in modern medicine, as a result of clinical practice of molar surveillance programs and early chemotherapeutic intervention for persistent gestational trophoblastic neoplasia. Diagnostic recognition of these tumors requires a high index of suspicion, awareness of their histologic characteristics, and appropriate application of immunohistochemical and molecular biomarkers. Recent attention has been given to a few precursor lesions of gestational trophoblastic tumors, including early/in situ choriocarcinoma and atypical placental site nodule.

Analysis of PD-L1 expression in trophoblastic tissues and tumors

The immune checkpoint proteins, programmed death receptor 1 (PD-1) and programmed death ligand 1 (PD-L1), are crucial for maintaining fetomaternal immune tolerance and immune escape in cancers. In this study, we performed a comprehensive immunohistochemical study of PD-L1 expression in a large cohort of trophoblastic tissues and tumors. We found that normal villi and hydatidiform moles showed a heterogeneous PD-L1 staining among trophoblast (strong in syncytiotrophoblast, moderate in intermediate trophoblast, and weak/negative in cytotrophoblast). Eleven exaggerated placental sites (100%) showed variable PD-L1 staining, whereas 7 (36.8%) of 19 placental site nodules/plaques were weakly positive for PD-L1 (P < .001). All gestational choriocarcinomas (CCs; n = 63), epithelioid trophoblastic tumors (n = 12), and placental site trophoblastic tumors (n = 41) were PD-L1 positive, with most showing strong staining. However, PD-L1 expression was lower in epithelioid trophoblastic tumors compared with placental site trophoblastic tumors and CCs (P = .004). Three presumably germ cell-derived pure CCs, the CC elements in 13 mixed germ cell tumors, and 4 gastric/rectal CCs were also positive for PD-L1, with widespread staining. The background nontrophoblastic tissues, such as endometrial glands, squamous cells, and adenocarcinomas, were PD-L1 negative. Western blot analysis showed that PD-L1 was expressed in all 3 trophoblastic cell lines. We conclude that PD-L1 is a sensitive but nonspecific marker for trophoblast and related tumors. The frequent strong PD-L1 expression suggests that immune checkpoint blockade could be a promising approach in treating trophoblastic tumors that merits further investigation.

Clinicopathologic significance of HLA-G and HLA-E molecules in Tunisian patients with ovarian carcinoma

BACKGROUND

The human leukocyte antigen (HLA)-G and HLA-E, non classical HLA class I molecules, have been highly implicated in immune tolerance. HLA-G and HLA-E molecules were proposed as putative markers of several advanced cancers. As a step towards a better understanding of ovarian carcinoma, we evaluated the expression of both HLA-G and HLA-E molecules and explored their prognostic implication.

METHODS

HLA-G and HLA-E expression were studied by immunohistochemistry on ovarian carcinoma tissues. This expression was semi-quantitatively scored into four expression groups and correlated to clinicopathological parameters and patients' survival.

RESULTS

HLA-G and HLA-E have been found to be highly expressed in ovarian carcinoma tissues (Respectively, 72.4% and 96.8%). They are frequently co-expressed. Univariate and multivariate analysis revealed that a positive HLA-G expression status in tumor tissue is a promising candidate parameter to predict disease recurrence in addition to the disease status in Tunisian patients with ovarian carcinoma. Moreover, the elevated HLA-E expression was associated with serous ovarian carcinoma subtype as well as with advanced stages of ovarian carcinoma.

CONCLUSION

HLA-G and HLA-E are highly represented in ovarian carcinoma suggesting a potential association with progressive disease mechanism. HLA-G and HLA-E molecules might be new candidates' markers for ovarian carcinoma progression.

Immunohistochemistry in Gynecologic Pathology: An Example-Based Practical Update

CONTEXT

- Immunohistochemical stains are routinely applied in the pathology diagnostic workup of gynecologic lesions. The rapidly expanding repertoire of available markers helps in refining the diagnostic criteria for each disease entity; however, limitations and pitfalls exist.

OBJECTIVE

- To provide a practical, relevant update on the use of immunohistochemistry for commonly encountered differential diagnoses in gynecologic pathology.

DATA SOURCES

- Literature review and authors' diagnostic experience.

CONCLUSIONS

- Immunohistochemistry is a helpful adjunct tool in gynecologic pathology. Although the primary application is in the diagnostic workup, novel prognostic and predictive markers, and immunostains to screen for genetic cancer syndromes, have also been recently introduced in the field.

PD-L1 Expression in Human Placentas and Gestational Trophoblastic Diseases

One of the major immune checkpoints responsible for immune evasion in cancer cells is the interaction between programmed cell death-1 (PD-1) and its ligand (PD-L1). As human trophoblastic cells display many of the features of malignant cells such as the ability to invade normal tissue including blood vessels and are apparently not eradicated by the host immune system, we undertook the present study to determine whether PD-L1 was upregulated in different types of trophoblastic cells during normal pregnancy and in gestational trophoblastic diseases. Immunohistochemistry using an anti-PD-L1-specific antibody demonstrated that in early and term normal placentas, PD-L1 was highly expressed in syncytiotrophoblast and to a much lower extent in intermediate trophoblastic cells located in the chorion laeve and implantation site. PD-L1 immunoreactivity was undetectable in cytotrophoblastic cells. This staining pattern in normal placenta was recapitulated in various types of gestational trophoblastic disease. PD-L1 was highly expressed by syncytiotrophoblast in complete moles and choriocarcinomas. The intermediate trophoblastic neoplasms, placental site trophoblastic tumors, and epithelioid trophoblastic tumors showed variable PD-L1 immunoreactivity but at a lower intensity than in the neoplastic syncytiotrophoblast in choriocarcinoma. In addition, we observed PD-1-positive lymphocytes located within the implantation site and in trophoblastic tumors. In summary, this study describes a novel mechanism for trophoblastic cells to create a tolerogenic feto-maternal interface by upregulating PD-L1 in syncytiotrophoblast and in intermediate trophoblast. Trophoblastic tumors may also use PD-L1 expression to evade the host immune response thereby promoting their survival.

Low molecular weight hyaluronan induces migration of human choriocarcinoma JEG-3 cells mediated by RHAMM as well as by PI3K and MAPK pathways

Hyaluronan (HA) is the major glycosaminoglycan present in the extracellular matrix. It is produced by some tumours and promotes proliferation, differentiation and migration among others cellular processes. Gestational trophoblastic disease (GTD) is composed by non-tumour entities, such as hydatidiform mole (HM), which is the most common type of GTD and also malignant entities such as choriocarcinoma (CC) and placental site trophoblastic tumour (PSTT), being CC the most aggressive tumour. Although there is a growing understanding of GTD biology, the role of HA in the pathogenesis of this group of diseases remains largely unknown. The aim of this work was to study the role of HA in the pathogenesis of GTD by defining the expression pattern of HA and its receptors CD44 and RHAMM, as well as to determine if HA can modulate proliferation, differentiation and migration of CC cells. Receptors and signalling pathways involved were also analyzed. We demonstrated that HA and RHAMM are differently expressed among GTD entities and even among trophoblast subtypes. We also showed that HA is able to enhance the expression of extravillous trophoblast markers and also to induce migration of JEG-3 cells, the latter mediated by RHAMM as well as PI3K and MAPK pathways. These findings indicate a novel regulatory mechanism for CC cell biology and also contribute to the understanding of GTD pathophysiology.

A 20-year retrospective study of histopathologic patterns of gonadal germ cell tumors in males in the University of Benin Teaching Hospital

BACKGROUND

Localization of germ cells tumors to the gonads is not uncommon and has been shown to possess good prognosis with appropriate treatment. Studies on the prevalence and histopathologic features of these tumors in Nigerians are, however, rare. This study was, therefore, aimed at determining the pattern of gonadal germ cell tumors (GGCTs) in Benin and environs.

MATERIALS AND METHODS

This was a 20-year retrospective study conducted at the University of Benin Teaching Hospital 9-(UBTH), a tertiary health facility in Benin City. Data were obtained from the histopathology day book of the Department of Morbid Anatomy of the UBTH, and permission was obtained from the UBTH Ethics Committee protocol number ADM/E 22/A/VOL.VH/928 with results displayed in tables and figures.

RESULTS

Intratubular germ cell neoplasms (ITGN) was the most common GGCT with about 33.3% of the total and was distributed within the fourth to fifth decades of life; benign cystic teratoma and choriocarcinoma were observed to have a low occurrence with 8.3% each found in age groups 11-20 and 21-30 years, respectively. The studied gonadal lesions were most frequent at the left testis and were predominantly premalignant forms.

CONCLUSION

This was an index study on patterns of GGCTs in males in UBTH, and it showed that GGCTs in males were predominantly premalignant with ITGN as the most common type of testicular germ cell tumors.

Association of HLA-G*01:01:02:01/G*01:04:01 polymorphism with gastric adenocarcinoma

Human leukocyte antigen-G (HLA-G) plays an important role in tumor cell escape from immune surveillance and HLA-G polymorphisms might service as a potential risk factor for clinical outcomes in GAC (gastric adenocarcinoma). We investigated the association between HLA-G polymorphisms as well as soluble HLA-G level and accordance of GAC. This case-control study included 100 GAC patients and 102 unrelated Iranian individual's samples as control. The clinical stages ranged from I to IV. PCR-RFLP method was carried out in order to specify the genotypes of the HLA-G gene. Concentrations of sHLA-G in serum were determined with the sHLA-G-specific enzyme linked immunosorbent assay (ELISA) kit. The G*01:04:01 and G*01:01:02:01 alleles were the predominant alleles in GAC patients and healthy controls. The G*01:01:03:01 and G*01:01:08 allele distributions are significantly higher among controls comparing to cases and seem to have protective effect (P value=0.026 and 0.007 respectively). There is a substantial differences in G*01:01:02:01/G*01:04:01 genotype frequencies between cases and controls (OR=2.8, P value<0.001). The G*01:01:03:01/G*01:04:01 and G*01:01:02:01/G*01:01:08 genotypes frequency are higher among controls in comparison to patients (P value=0.028 and 0.007 respectively). The polymorphisms in HLA-G could affect GAC induction and its outcome. Also, increased sHLA-G levels in serum might be a useful biomarker for diagnosis.

GATA-3 expression in trophoblastic tissues: an immunohistochemical study of 445 cases, including diagnostic utility

Immunohistochemical expression of GATA-3 is seen predominantly in non-neoplastic bladder and breast epithelium and their respective carcinomas; however, data on expression in normal and lesional trophoblastic tissues are limited. Immunohistochemical staining for GATA-3 was assessed in a range of normal/lesional trophoblastic tissues and tumors in the differential diagnosis (n=445), including nonmolar products of conceptions/second and third trimester placentas/ectopic pregnancies, hydatidiform moles, placental site nodules, normal/exaggerated implantation sites, choriocarcinomas, epithelioid trophoblastic tumors, placental site trophoblastic tumors, atypical smooth muscle tumors (including leiomyosarcoma), and cervical and pulmonary squamous cell carcinomas. The extent of expression (0 to 4+) and intensity (weak to strong) were recorded. All cases with developing trophoblast/non-neoplastic trophoblastic proliferation and 81% of trophoblastic neoplasms were positive. Of all non-neoplastic trophoblast cell types, expression was observed in cytotrophoblast in 89% of cases, syncytiotrophoblast in 50%, intermediate trophoblast in 100%, and villous trophoblastic columns in 100%. Increasing gestational age was associated with a decrease in extent/intensity of expression in non-neoplastic cytotrophoblast and syncytiotrophoblast, whereas intermediate trophoblast maintained diffuse and strong expression from early to late gestation (P<0.0001). Eighty-nine percent of normal/exaggerated implantation sites showed 3+ or 4+ expression, whereas staining in 55% of placental site nodules was 1+ or 2+. Staining for GATA-3 was present in 78% of choriocarcinomas, 95% of epithelioid trophoblastic tumors, and 71% of placental site trophoblastic tumors. Although the number of choriocarcinomas and placental site trophoblastic tumors that showed a spectrum of expression ranging from negative to diffuse was relatively evenly distributed, 81% of epithelioid trophoblastic tumors had 3+ or 4+ staining. None of the atypical smooth muscle tumors and 3% of squamous cell carcinomas were positive, all of which exhibited weak staining. We conclude that GATA-3 is frequently expressed in normal and lesional trophoblastic tissues. It is also differentially expressed in intermediate trophoblast and cytotrophoblast/syncytiotrophoblast, which varies according to time during pregnancy. This study expands the spectrum of neoplasms known to express GATA-3. Thus, recognition of expression in trophoblastic tumors is important, because it can present a diagnostic pitfall in the assessment of suspected metastatic bladder or breast carcinomas involving the gynecologic tract. In the evaluation of diagnostically problematic tumors for which trophoblastic neoplasms are in the differential diagnosis, such as leiomyosarcoma and squamous cell carcinoma, GATA-3 can be included as part of an immunohistochemical panel particularly when other trophoblastic markers are either not available or yield ambiguous results.

The Utility of Immunohistochemistry in the Differential Diagnosis of Gynecologic Disorders

Context

Immunohistochemistry has assumed an increasing role in the identification and characterization of gynecologic disorders including lesions with deceptively bland morphology, uncommon and underdiagnosed neoplasms, and neoplasms with specific genetic alterations associated with overexpression or loss of expression of specific proteins. The diagnostic accuracy has been significantly improved owing to the discovery and increasing experience with the tumor-associated biomarkers, and the increasing demand for precise tumor classification to assess suitability for the expanding therapeutic modalities including clinical trials.

Objective

To differentiate lesions of the gynecologic tract through the use of effective immunohistochemical panels.

Data Sources

Literature review and authors' personal practice experience.

Conclusions

The application of diagnostic and prognostic immunohistochemical panels has enabled pathologists to better guide therapeutic decisions and to better predict the clinical outcome. It is now well established that the use of ancillary testing, including immunohistochemistry, has a significant power in the identification, differentiation, and classification of reactive, premalignant, and malignant gynecologic disorders. This article discusses the utilities and pitfalls of the commonly used immunohistochemical markers in the context of overlapping morphologic features encountered in the uterus, ovaries, and fallopian tubes.

A case report of complete mole with co-existent exaggerated placental site reaction and review of the literature

Exaggerated placental site (EPS) is defined as a non-neoplastic trophoblastic lesion, which intermediate trophoblasts infiltrate exaggeratedly into endometrium and myometrium. These lesions may occur following normal pregnancy, ectopic pregnancy, abortus or molar pregnancy. Herein we share a case of EPS detected after evacuation due to molar pregnancy. We also review the related literature, where only a few reports exist describing the clinical course, histopathology and differential diagnosis of EPS.

Reassessment of HLA-G isoform specificity of MEM-G/9 and 4H84 monoclonal antibodies

Human leukocyte antigen (HLA)-G is a non-classical HLA class I molecule thought to play a key role in maternal-fetal tolerance. Although initial studies suggested that HLA-G expression is restricted to extravillous cytotrophoblasts, expression was subsequently reported in a wide variety of other human tissues and tumor cells. However, consensus as to the validity of these collective findings has proven difficult because the antibodies used to define the temporal and spatial expression patterns of HLA-G remain incompletely characterized. The aim of our study was to reassess two of the most widely used HLA-G antibodies (MEM-G/9 and 4H84) in HLA-G-positive (JEG-3 and HLA-G transduced) and -negative (dermal fibroblast, mesenchymal stem cell, K562, and Jurkat) lines using flow cytometry, immunofluorescence, and western blotting. We found that MEM-G/9 recognized HLA-G3 by flow cytometry, indicating that its epitope is present on the α1 domain of HLA-G. Although 4H84 preferably recognized unfolded HLA-G-free chains, it showed strong non-specificity under certain methodological conditions.

Establishment of a choriocarcinoma model from immortalized normal extravillous trophoblast cells transduced with HRASV12

Gestational choriocarcinoma is a malignant trophoblastic tumor. The development of novel molecular-targeted therapies is needed to reduce the toxicity of current multiagent chemotherapy and to treat successfully the chemoresistant cases. The molecular mechanisms underlying choriocarcinoma tumorigenesis remain uncharacterized, however, and appropriate choriocarcinoma animal models have not yet been developed. In this study, we established a choriocarcinoma model by inoculating mice with induced-choriocarcinoma cell-1 (iC³-1) cells, generated from HTR8/SVneo human trophoblastic cells retrovirally transduced with activated H-RAS (HRASV12). The iC³-1 cells exhibited constitutive activation of the mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-kinase (PI3K) pathways and developed into lethal tumors in all inoculated mice. Histopathological analysis revealed that the tumors consisted of two distinct types of cells, reminiscent of syncytiotrophoblasts and cytotrophoblasts, as seen in the human choriocarcinoma. The tumors expressed HLA-G and cytokeratin (trophoblast markers) and hCG (a choriocarcinoma marker). Comparative analysis of gene expression profiles between iC³-1 cells and parental HTR8/SVneo cells revealed that iC³-1 cells expressed matrix metalloproteinases, epithelial-mesenchymal transition-related genes, and SOX3 at higher levels than parental trophoblastic cells. Administration of SOX3-specific short-hairpin RNA decreased SOX3 expression and attenuated the tumorigenic activity of iC³-1 cells, suggesting that SOX3 overexpression might be critically involved in the pathogenesis of choriocarcinoma. Our murine model represents a potent new tool for studying the pathogenesis and treatment of choriocarcinoma.

Trophoblastic vasculogenic mimicry in gestational choriocarcinoma

Angiogenesis is a characteristic feature of solid tumors, which depend on the newly formed vasculature to prevent hypoxia and to sustain uncontrolled tumor cell proliferation. In this study, we investigated the blood supply system in 10 gestational choriocarcinomas on the basis of histopathological and immunohistochemical features. In all examined cases, morphological analysis demonstrated that blood channels within the center of choriocarcinomas were surrounded by neoplastic trophoblastic cells rather than by endothelial cells. Similarly, there was a lack of CD31 and CD34-positive endothelial cells within choriocarcinomas. In the periphery of choriocarcinomas, tumor cells invaded uterine stroma-derived blood vessels where trophoblastic cells replaced endothelial cells, forming anastomoses between endothelium-lined blood vessels and trophoblast-lined pseudovascular channels. Masson's trichrome staining revealed minimal amounts of connective tissue within choriocarcinomas. In contrast, CD31 and CD34-positive blood vessels were present in other types of gestational trophoblastic neoplasms including 8 placental site trophoblastic tumors and 12 epithelioid trophoblastic tumors. These findings provide cogent evidence that choriocarcinoma represents one of a few human tumor types that utilizes vasculogenic mimicry by tumor cell in supporting tumor development.

Human leukocyte antigen G expression in breast cancer: role in immunosuppression

Human leukocyte antigen G (HLA-G) is an immunotolerant nonclassical major histocompatibility complex Class Ib molecule. It is expressed by trophoblastic placental cells during pregnancy to protect the fetus from maternal alloreactivity. HLA-G is overexpressed in tumors and involved in cancer immune evasion. Reverse transcription-polymerase chain reaction and immunohistochemistry (IHC) were used to examine HLA-G expression in normal mammary and breast cancer cell lines and normal and human breast cancer tissues. Reverse transcription-polymerase chain reaction confirmed that normal epithelial MCF-12A cells had no HLA-G mRNA expression, whereas cancer cell lines MCF-7, T47D, and MDA-MB-231 and NCI/Adr-Res had various levels of HLA-G mRNA expression. Twelve (12) normal and 38 breast cancer tissues were examined by IHC. Fifty-eight (58) percent (22/38) of cancers had medium to strong staining to HLA-G, whereas only 8% (1/12) of normal breast tissues had medium to strong staining, and the difference was significant (p < 0.05). HLA-G staining was found in the membranes and cytoplasm of cancer cells. In conclusion, breast cancer cells overexpress HLA-G mRNA and protein, and this probably contributes to immune evasion.

Expression of glypican 3 in placental site trophoblastic tumor

Background

Glypican-3 (GPC3) is a membrane-bound heparan sulfate proteoglycan that functions in embryonic cell growth and differentiation and is highly expressed in the placenta. GPC3 is mutated in Simpson-Golabi-Behmel syndrome, which is characterized by tissue overgrowth and an increased risk of embryonal malignancies. GPC3 has also been implicated in sporadic cancer, particularly hepatocellular carcinoma, for which it has been shown to be a useful diagnostic marker. Although GPC3 expression has been studied in non-neoplastic placental tissue, its presence in gestational trophoblastic diseases has not been previously explored. The purpose of this study was to investigate the immunohistochemical expression of GPC3 in placental site trophoblastic tumor (PSTT), a very rare gestational trophoblastic neoplasm which may be morphologically confused with non-trophoblastic tumors, and to assess its possible utility as a diagnostic marker.

Methods

Fifteen cases of PSTT, as well as samples from placental site nodule (PSN) (n = 2), leiomyosarcoma (n = 1), leiomyoma (n = 1), invasive cervical squamous cell carcinoma (n = 7) and endometrial adenocarcinoma (n = 11) were examined. Immunoreactivity was semi-quantitatively evaluated as negative (0, < 5% of cells stained), focally positive (1+, 5-10% of cells stained), positive (2+, 11-50% of cells stained) or diffusely positive (3+, > 50% of cells stained). Staining intensity for each subtype was graded from 0 to 3 and a mean intensity was calculated.

Results

Eighty percent of PSTT (12/15) were immunoreactive for GPC3 (0, 20; 1+, 20%; 2+, 40%; 3+, 20%) with a mean intensity of 1.3. Stronger, predominately cytoplasmic staining was seen in larger multi- and mononucleated cells with smaller mononucleate cells showing weak muddy cytoplasmic staining. Both PSN cases were positive (1+, 50%; 2+, 50%) and two of nine invasive cervical squamous cell carcinomas showed staining (0, 57%; 1+, 29%; 2+, 14%), predominately in a basal distribution. Other uterine tumors and non-neoplastic tissues were negative.

Conclusions

Identification of GPC3 in PSTT and PSN is consistent with the derivation of these lesions from intermediate trophoblasts, which have been described to express GPC3. GPC3 may be a useful adjunct immunohistochemical marker in differentiating PSTT from non-trophoblastic tumors.

HLA-G and immune evasion in cancer cells

Acquisition of novel gene products or new antigens in cancer cells elicits a host immune response that results in selection pressure for tumor clones to evade immunosurveillance. Similar to maternal-fetal tolerance and allotransplantation acceptance, upregulation of HLA-G expression has been found as one of the mechanisms that are programmed in cancer cells. HLA-G expression is frequently detected in a wide variety of human cancers and its protein levels negatively correlate with poor clinical outcome. The immune inhibitory effect can be achieved by binding of HLA-G molecules to the immunoglobulin-like inhibitory receptors that are expressed on the immunocompetent cells at all stages of the immune response. This review summarizes recent studies of HLA-G expression in human cancer, with a special focus on the molecular mechanisms that underlie how HLA-G molecules facilitate tumor cell evasion of the host immune response, and presents new directions for developing HLA-G-based diagnosis/therapeutics.

Current issues in the histopathology of gestational trophoblastic tumors

Gestational trophoblastic neoplasia (GTN) encompasses several entities including complete (CHM) and partial (PHM) hydatidiform mole (HM) and the malignant gestational trophoblastic tumors (GTTs), choriocarcinoma (CC), and placental-site trophoblastic tumor (PSTT), including epithelioid trophoblastic tumor (ETT). To detect pGTN, postmolar surveillance by measurement of maternal human chorionic gonoadotropin (hCG) levels should be performed. With such a protocol, many cases of pGTN are identified early at a presymptomatic stage based on plateuing or rising hCG concentrations and subsequently treated successfully with chemotherapy. In such cases, histopathological confirmation of the precise nature of the pGTN usually is not available. However, GTT also may present clinically with primary or metastatic disease, either following and unrecognized HM or developing from a nonmolar gestation. Due to their distinctive clinical and histological features, malignant GTTs are generally clearly subdivided into CC and PSTT (including ETT). CC essentially represents malignant trophoblastic tumors with differentiation toward villous trophoblast, with extensive hematogenous spread and high hCG levels, which are highly chemoresponsive. However, PSTTs, represent malignant differentiation toward implantation-site type trophoblast, with lower hCG levels and less response to chemotherapy. Current issues regarding the clinical and histological features of CC and PSTT/ETT are discussed.

Chorangiocarcinoma: a case report and review of the literature

Chorangiocarcinoma is the name designated to a chorangioma with trophoblastic proliferation manifesting increased proliferative activity. Only 3 such cases have been published so far. Other studies challenged this entity by demonstrating that proliferation of the trophoblast around chorangioma is a common phenomenon. We present a case of a unique vascular lesion in a term placenta with a malignant trophoblastic component. Microscopic examination of a well-demarcated placental mass revealed a chorangioma with multiple nodules composed of pleomorphic cells displaying focal multinucleation, large areas of necrosis, and high mitotic activity. Immunohistochemical stains of these cells were strongly positive for pancytokeratin and the beta subunit of human chorionic gonadotropin and focally positive for HSD3B1. There was no invasion of the basement membrane, and no free-floating tumor cells in the intervillous space. No evidence of metastasis was found on follow-up of the mother and newborn. It is concluded that the tumor presented herein, displaying a histologically unequivocal malignant trophoblastic component in a benign chorangioma, is a true chorangiocarcinoma, and should be included within the category of gestational neoplasia as a tumor closely related to choriocarcinoma.

Pathogenesis of choriocarcinoma: clinical, genetic and stem cell perspectives

Choriocarcinoma is a unique malignant neoplasm composed of mononuclear cytotrophoblasts and multinucleated syncytiotrophoblasts that produce human chorionic gonadotrophin. Choriocarcinoma can occur after a pregnancy, as a component of germ cell tumors, or in association with a poorly differentiated somatic carcinoma, each with distinct clinical features. Cytogenetic and molecular studies, predominantly on gestational choriocarcinoma, revealed the impact of oncogenes, tumor suppressor genes and imprinting genes on its pathogenesis. The role of stem cells in various types of choriocarcinoma has been studied recently. This review will discuss how such knowledge can enhance our understanding of the pathogenesis of choriocarcinoma, enable exploration of novel anti-choriocarcinoma targeted therapy and possibly improve our insight on embryological and placental development.

Immunohistochemical studies of trophoblastic tumors

Although intermediate trophoblastic tumors (ITTs) are rare forms of trophoblastic neoplasia, their recognition is important as they require distinct therapeutic approaches. We have noted mixed trophoblastic tumors, with a combination of placental site trophoblastic tumor and epithelioid trophoblastic tumor patterns within the same case, and more frequently a combination of ITT with choriocarcinoma, which can create difficulty in the classification of these tumors. The distinction of the ITTs from choriocarcinoma is important because ITTs do not respond as well to chemotherapy as choriocarcinoma. In addition, ITTs can be confused with a variety of malignant neoplasms, the most common of which is poorly differentiated carcinoma of the cervix. Immunohistochemistry is one means of identifying trophoblastic tumors and of distinguishing them from other entities. We investigated the immunophenotype of 15 ITTs, 11 choriocarcinomas, and 10 primary cervical carcinomas using a panel of human placental lactogen, p63, CK5/6, CK18, human chorionic gonadotropin (hCG), human leukocyte antigen (HLAG), Mel-CAM, (CD146) carcinoembryonic antigen, CD10, inhibin, p16, and pan-keratin. CD10 was positive in all the cases of ITT and choriocarcinoma. HLA-G expression was present in 93% of ITTs and all choriocarcinoma cases. hCG was positive in 87% of ITTs and 100% of choriocarcinomas. We concluded that a panel consisting of HLA-G, CD10, and hCG can be very helpful in the identification of the ITTs. Adding CK5/6 to these markers can help to differentiate ITT from primary cervical carcinoma. However, the distinction of ITTs from choriocarcinoma cannot be accomplished on immunohistochemical studies, as they have similar immunophenotypes.

Lack of genetic association between exaggerated placental site reaction and placental site trophoblastic tumor

Exaggerated placental site (EPS) reaction is a reactive or an exuberant physiologic process involving intermediate trophoblasts infiltrating the underlying endomyometrium at the implantation site. Sharing similar cytological and immunohistochemical features with the tumor cells of placental site trophoblastic tumor, a biological link between the 2 lesions can be speculated. Because placental site trophoblastic tumor has a unique sex chromosomal requirement in its genome that requires a paternal X chromosome (i.e. a female antecedent gestation), we investigated whether EPS carries the similar genetic profile by DNA genotypic analysis. Twenty cases of EPS were reviewed and analyzed by AmpFlSTR Identifiler polymerase chain reaction amplification system (Applied Biosystems, Inc., Foster City, CA). The genetic profile of all cases demonstrated unique paternal alleles to that of the paired maternal tissue, confirming the trophoblastic origin of EPS. The presence of an XY genome (male) was identified in 11 cases (55%), and an XX genome (female) was seen in the rest of 9 cases (45%). Therefore, EPS is a trophoblastic lesion that can arise from either male or female gestations. The assignment of sex chromosomes in our study (XY, 55% and XX, 45%) does not support a neoplastic association between placental site trophoblastic tumor and EPS.

Placental site trophoblastic tumor with multiple metastases and complete response to salvage BEP regimen: a case report and review of the literature

Placental site trophoblastic tumor is a rare form of gestational trophoblastic disease, derived from invasive implantation site (intermediate) trophoblastic cells. It is frequently resistant to chemotherapy. Patients with metastases, however, frequently have progressive disease and die despite surgery and multiagent chemotherapy. In this case, a 24-year-old woman was referred because of intermittent vaginal bleeding episodes for 5 months following delivery. Multiple metastases in lungs, liver, kidneys, breast, pancreas, and adrenal and thyroid glands were detected. Combination therapy including surgery and multiagent chemotherapy was planned. Hysterectomy and pelvic lymph node dissection were performed. All metastatic lesions disappeared with EMA-CO treatment. However four courses of BEP regimen, salvage therapy, was performed for plateauing hCG level. Surgery and multiagent chemotherapy seem mainstay of treatment of cases having multiple metastases of PSTTs.

Use of reticulin stain in the diagnosis of intra-uterine gestation

AIMS

The diagnosis of intra-uterine gestation may be problematic when specimens from clinically suspected products of conception lack chorionic villi and/or fetal somatic tissues, since the distinction of intermediate trophoblast from decidual or myometrial elements can be difficult. The placental site is also characterised by stromal changes, including the deposition of a characteristic extracellular fibrinoid matrix. We have noted that these stromal changes may be highlighted by a simple reticulin stain; therefore, we have evaluated reticulin staining in a series of endometrial biopsy specimens from patients with intra-uterine and ectopic gestations.

METHODS

Reticulin staining was performed in 28 endometrial specimens from patients with first trimester intra-uterine gestations, including 14 cases that lacked chorionic elements. Eight endometrial samples from patients with concurrent histologically verified tubal ectopic pregnancy were also examined. Selected cases were also studied using a Masson trichrome stain, and immunohistochemically with antisera to cytokeratin and HPL.

RESULTS

There was a distinct increase in reticulin staining, usually evident at low power magnification, in most areas of decidua showing implantation site. Prominent reticulin staining was present around the decidual and trophoblast cells and there was also accentuation around stromal vessels, glands and myometrial cells. There was no clear difference in staining within areas of decidua including only rare intermediate trophoblast cells but this pattern was seldom seen in isolation. Minimal changes were seen in the placental site using the Masson trichrome stain.

CONCLUSION

Reticulin stains may prove useful in the assessment of endometrial specimens from patients with purported intra-uterine gestations when chorionic elements are not identified. Since the staining technique is simple and can be quickly performed, it could be used as an adjunct to conventional H&E assessment and to select appropriate specimen blocks for additional more sensitive studies, including immunohistochemistry.

Application of Immunohistochemistry to the Genitourinary System (Prostate, Urinary Bladder, Testis, and Kidney)

Context.—The variety of morphologic patterns of different entities of the genitourinary tract can present a diagnostic dilemma for the pathologist. This is especially true in cases of mimics of cancer, a cancer of unknown primary, or poorly differentiated tumors, in which it is hard to assign histogenesis needed to plan the correct therapy for the patient. Immunohistochemistry offers a better capacity than hematoxylin-eosin staining alone to differentiate human tissue types. Also, in the past decades, several techniques had been developed to differentiate between benign and malignant processes with morphologic overlap. By using immunohistochemistry in selected cases, the rate of false-negative and false-positive diagnoses can be reduced, and some patients are afforded the opportunity to get more specific or effective therapy as a result.

Objective.—For each subgroup of genitourinary system tumors, common diagnostic problems are reviewed, and immunohistochemical markers useful in addressing these problems are discussed, along with expected patterns of immunoreactivity.

Data Sources.—The pertinent literature, with focus on immunohistochemical staining of tumors of the genitourinary tract.

Conclusions.—The addition of immunohistochemistry to the diagnostic armamentarium for genitourinary pathologic diagnosis has increased the sensitivity and specificity of diagnoses and aided in the selection of optional therapeutic regimens in selected cases.

Diagnostic problems with trophoblastic lesions

The purpose of this review is to address some common problems involving the diagnosis of trophoblastic lesions.

Soluble HLA-G in the peritoneal fluid of women with endometriosis

The aim of this study was to determine the level of soluble HLA-G molecules in the peritoneal fluid of endometriosis patients. The findings demonstrate that a soluble HLA-G level in the peritoneal fluid of women with endometriosis is similar to that of the control group.

Immunohistochemistry of choriocarcinoma: an aid in differential diagnosis and in elucidating pathogenesis

Choriocarcinoma is traditionally described as being composed of cytotrophoblast and syncytiotrophoblast. Microscopically, these 2 types of cells are intimately associated with each other, forming a characteristic biphasic plexiform pattern, however, the nature of these 2 types of trophoblastic cells is not well understood. In this study, we used immunohistochemistry for several trophoblastic markers to analyze the trophoblastic subpopulations in 36 gestational choriocarcinomas. Eighty-one specimens including placenta, complete mole, placental site nodule, epithelioid trophoblastic tumor, and placental site trophoblastic tumor were analyzed. The antibodies included Mel-CAM, HLA-G, MUC-4, and beta-catenin. A semiquantitative assessment of positive cells and the cellular localization of these markers were recorded. We found diffuse strong membranous and cytoplasmic staining for MUC-4 in mononucleate cells in all 36 cases (100%) and a similar pattern of localization in 28 cases (78%) for HLA-G. This distribution was similar to that in normal placentas, where MUC-4 and HLA-G are expressed in the trophoblastic cells of the trophoblastic columns and implantation site. In choriocarcinoma, mononucleate trophoblastic cells showed moderate immunoreactivity for Mel-CAM, a specific marker for implantation site intermediate trophoblast, in 78% of the cases. The MUC-4, HLA-G, and Mel-CAM-positive trophoblastic cells were larger than cytotrophoblastic cells, with more abundant cytoplasm, consistent with the morphology of intermediate trophoblast. In contrast, 31% of the choriocarcinomas contained a very small proportion (<5%) of mononucleate trophoblastic cells compatible with cytotrophoblast that was positive for nuclear beta-catenin, a cytotrophoblast-associated marker. These results suggest that choriocarcinoma is composed predominantly of a mixture of syncytiotrophoblast and intermediate trophoblast with only a small proportion of cytotrophoblast. The presence of nuclear beta-catenin staining in the cytotrophoblast of choriocarcinoma is consistent with the view that choriocarcinoma develops from transformed cytotrophoblastic cells which are presumably the cancer stem cells that differentiate into either intermediate trophoblast or syncytiotrophoblast.

Clinical and biological significance of HLA-G expression in ovarian cancer

Ovarian cancer is the most lethal gynecologic neoplastic disease in which the molecular etiology remains largely unclear. Like other cancer types, evolution of ovarian tumor cell species is accompanied by acquisition of novel gene products and these new tumor-associated antigens elicit a host immune response that creates selection pressure upon the emerging tumor clones. One of the mechanisms that ovarian cancer cells evade immune surveillance is by upregulating human leukocyte antigen-G (HLA-G) expression. HLA-G is a non-classical MHC class I molecule and accumulated evidence has suggested its biological role in inactivating immune response. It has been well known that HLA-G expression is frequently detected in the most aggressive type of ovarian cancer, i.e., high-grade serous carcinoma, and measurement of HLA-G protein levels has shown promise for detection and prognosis prediction in ovarian cancer. This review summarizes those recent studies on HLA-G expression in ovarian cancer with special focus on its clinical and biological significance which is fundamental to elucidate the molecular mechanisms in ovarian cancer development and paves the foundation for future HLA-G-based diagnostics and therapeutics.

The role of HLA-G in gastrointestinal inflammatory disease and malignancy

Human leukocyte antigen (HLA)-G has been shown to act as an immune-inhibitory molecule and to interfere with the normal functions of natural killer (NK) cells and T-cells, conferring a potential route for HLA-G expressing cells to escape host immune surveillance. These findings have led to the rather intense study of HLA-G expression in several different arenas, including organ transplantation, inflammatory conditions, and in a wide variety of neoplasms including hematolymphoid neoplasms, visceral carcinomas, gliomas, and dermal-based neoplasms. This review will focus on the role of HLA-G in inflammatory conditions of the bowel, which can serve as an initiator of neoplastic alterations, as well as examine HLA-G expression and function in a variety of gastrointestinal malignancies. Although there are only a limited number of studies that have examined HLA-G in the gastrointestinal tract, the role of HLA-G has been controversial in this organ system with conflicting results reported even within the same tumor type.

Expression of human leucocyte antigen G (HLA-G) is associated with prognosis in non-small cell lung cancer

In a previous study, we demonstrated that human leucocyte antigen G (HLA-G) was aberrantly expressed in a majority of primary colorectal carcinomas, and that the detection of HLA-G expression had a strong and independent prognostic value in human colorectal cancer. In the current study, we look into whether the aberrant expression of HLA-G is also related to non-small cell lung cancer (NSCLC). The expression of HLA-G was investigated immunohistochemically in 106 patients with NSCLC. The correlation between HLA-G status and various clinicopathological parameters was analysed. As well, the level of HLA-G expression was also compared to the survival rate of patients with NSCLC. In total, we found that in 75% (79/106) of the primary site of NSCLC, an aberrant HLA-G expression was detected. However, this expression was not observed in the normal lung tissues. HLA-G expression in NSCLC was significantly correlated with lymph nodal metastasis, clinical stages of the disease, and host immune response (P = 0.0001, 0.0001, and 0.027, respectively). Patients with HLA-G positive tumours had a significantly shorter survival time than those with tumours that were HLA-G negative (P = 0.001). In addition, through multivariate analysis, HLA-G exhibited an independent prognostic factor (P = 0.01, relative risk 4.09; 95% confidence interval 1.40-11.9). All in all, our results indicate that the expression of HLA-G is a characteristic feature of NSCLC, and they suggest that immunostaining by anti-HLA-G antibodies may be a potentially useful prognostic indicator.