Recent molecular approaches to elucidate the mechanism of embryo implantation: trophinin, bystin, and tastin as molecules involved in the initial attachment of blastocysts to the uterus in humans

High trophinin-associated protein expression predicts good survival in acute myeloid leukemia with normal cytogenetics

BACKGROUND

Nearly half of adult acute myeloid leukemia (AML) patients were classified into cytogenetic normal acute myeloid leukemia (CN-AML). The expression level of Trophinin associated protein (TROAP) was proven to be associated with the prognosis of several cancers, but it is still unclear in the prognosis of patients with CN-AML.

METHODS

We integrated CN-AML patients samples from 4 datasets to analyze the relationship between TROAP expression and the survival of CN-AML. In addition, we investigated 92 AML patients of The Cancer Genome Atlas (TCGA) database to analyze the relationship between TROAP expression and the survival of AML patients received chemotherapy. We investigated the relationship between the expression of TROAP and drug sensitivity in AML cell lines.

RESULTS

CN-AML patients with high TROAP expression were related to good event-free survival (EFS) and overall survival (OS). In AML patients received chemotherapy, high TROAP expression was associated with good survival prognosis. Additionally, the expression of TROAP gene in leukemia stem cells (LSC) + group was lower. Among multiple drugs, the lower the expression of TROAP, the lower the IC50.

CONCLUSION

TROAP could serve as an independent predictor of CN-AML patients and could act as a potential biomarker for the prognosis of CN-AML. TROAP expression levels were closely correlated with the drug sensitivity of multiple drugs.

Early human trophoblast development: from morphology to function

Human pregnancy depends on the proper development of the embryo prior to implantation and the implantation of the embryo into the uterine wall. During the pre-implantation phase, formation of the morula is followed by internalization of blastomeres that differentiate into the pluripotent inner cell mass lineage, while the cells on the surface undergo polarization and differentiate into the trophectoderm of the blastocyst. The trophectoderm mediates apposition and adhesion of the blastocyst to the uterine epithelium. These processes lead to a stable contact between embryonic and maternal tissues, resulting in the formation of a new organ, the placenta. During implantation, the trophectoderm cells start to differentiate and form the basis for multiple specialized trophoblast subpopulations, all of which fulfilling specific key functions in placentation. They either differentiate into polar cells serving typical epithelial functions, or into apolar invasive cells that adapt the uterine wall to progressing pregnancy. The composition of these trophoblast subpopulations is crucial for human placenta development and alterations are suggested to result in placenta-associated pregnancy pathologies. This review article focuses on what is known about very early processes in human reproduction and emphasizes on morphological and functional aspects of early trophoblast differentiation and subpopulations.

The Upregulation of Trophinin-Associated Protein (TROAP) Predicts a Poor Prognosis in Hepatocellular Carcinoma

Purpose: Trophinin-associated protein (TROAP) is a cytoplasmic protein that plays a significant role in the processes of embryo transplantation and microtubule regulation. However, the relevant survival analysis and cancer progression analysis have not yet been reported.

Methods: Eighteen matched pairs of tumor and adjacent non-tumor samples were evaluated to detect the TROAP mRNA level. Immunohistochemistry (IHC) was used to evaluate the TROAP expression in 108 hepatocellular carcinoma patients who underwent surgical resection. Meanwhile, data from the TCGA database was statistically evaluated.

Results: In the present study, we detected a significant increase in the TROAP mRNA level in tumor tissues when compared with adjacent non-tumor tissues. Moreover, the upregulation of TROAP was associated with increased serum AFP and GGT; the greater the tumor number was, the larger the tumor size, differentiation grade, and cancer embolus in clinical analysis. In HCC patients, elevated TROAP expression in the primary tumor was positively related to clinical severity, such as poor overall survival and disease-free survival. In addition, both univariate and multivariate survival analysis validated that TROAP expression was a promising independent risk factor for overall survival and disease-free survival in HCC patients. Furthermore, the results derived from the analysis of data from the TCGA database were consistent with previous results. Altogether, our results show that TROAP is a novel crucial regulator of HCC progression and is a potential therapeutic biomarker for HCC patients.

Conclusions: Elevated TROAP expression predicted a poor prognosis, and TROAP may serve as a potential biomarker for application in oncotherapy.

High Trophinin-Associated Protein Expression Is an Independent Predictor of Poor Survival in Liver Cancer

BACKGROUND

Trophinin-associated protein (TROAP) is a cytoplasmic protein that functions as an adhesion molecule in processes such as embryo implantation, spindle formation, and cancer.

OBJECTIVE

To evaluate the relationship of TROAP expression in hepatocellular carcinoma (HCC) tissue with clinicopathologic parameters and survival time in liver cancer patients based on an analysis of The Cancer Genome Atlas Liver Hepatocellular Carcinoma (TCGA-LIHC) data.

METHODS

RNA-sequencing (RNA-Seq) expression data and clinical information were downloaded for the TCGA-LIHC cohort. Associations between TROAP expression in HCC tissues and clinical parameters were evaluated by Chi-square tests. Differences in survival between high and low expression groups (median expression cutoff) from Cox regression analysis were compared, and P values were calculated by a log-rank test. Kaplan-Meier curves were compared with the log-rank test.

RESULTS

Analysis of RNA-Seq gene expression data for 373 patients with primary tumors revealed overexpression of TROAP in liver cancer. High TROAP expression was associated with survival status (P = 0.015), T stage (P = 0.049), clinical stage (P = 0.048), and gender (P = 0.033). Patients with high TROAP-expressing liver cancers had a shorter median overall survival of 3.83 years compared with 5.80 years for patients with low TROAP-expressing liver cancers (P = 0.00422). Multivariate analysis identified TROAP expression as an independent prognostic variable for overall survival in liver cancer patients.

CONCLUSION

TROAP expression is an independent predictor of poor survival in liver cancer.

Mechanisms of cancer dissemination along nerves

The local extension of cancer cells along nerves is a frequent clinical finding for various tumours. Traditionally, nerve invasion was assumed to occur via the path of least resistance; however, recent animal models and human studies have revealed that cancer cells have an innate ability to actively migrate along axons in a mechanism called neural tracking. The tendency of cancer cells to track along nerves is supported by various cell types in the perineural niche that secrete multiple growth factors and chemokines. We propose that the perineural niche should be considered part of the tumour microenvironment, describe the molecular cues that facilitate neural tracking and suggest methods for its inhibition.

Natural selection of human embryos: decidualizing endometrial stromal cells serve as sensors of embryo quality upon implantation

Background

Pregnancy is widely viewed as dependent upon an intimate dialogue, mediated by locally secreted factors between a developmentally competent embryo and a receptive endometrium. Reproductive success in humans is however limited, largely because of the high prevalence of chromosomally abnormal preimplantation embryos. Moreover, the transient period of endometrial receptivity in humans uniquely coincides with differentiation of endometrial stromal cells (ESCs) into highly specialized decidual cells, which in the absence of pregnancy invariably triggers menstruation. The role of cyclic decidualization of the endometrium in the implantation process and the nature of the decidual cytokines and growth factors that mediate the crosstalk with the embryo are unknown.

Methodology/Principal Findings

We employed a human co-culture model, consisting of decidualizing ESCs and single hatched blastocysts, to identify the soluble factors involved in implantation. Over the 3-day co-culture period, approximately 75% of embryos arrested whereas the remainder showed normal development. The levels of 14 implantation factors secreted by the stromal cells were determined by multiplex immunoassay. Surprisingly, the presence of a developing embryo had no significant effect on decidual secretions, apart from a modest reduction in IL-5 levels. In contrast, arresting embryos triggered a strong response, characterized by selective inhibition of IL-1β, -6, -10, -17, -18, eotaxin, and HB-EGF secretion. Co-cultures were repeated with undifferentiated ESCs but none of the secreted cytokines were affected by the presence of a developing or arresting embryo.

Conclusions

Human ESCs become biosensors of embryo quality upon differentiation into decidual cells. In view of the high incidence of gross chromosomal errors in human preimplantation embryos, cyclic decidualization followed by menstrual shedding may represent a mechanism of natural embryo selection that limits maternal investment in developmentally impaired pregnancies.

Current knowledge of the aetiology of human tubal ectopic pregnancy

BACKGROUND An ectopic pregnancy is a pregnancy which occurs outside of the uterine cavity, and over 98% implant in the Fallopian tube. Tubal ectopic pregnancy remains the most common cause of maternal mortality in the first trimester of pregnancy. The epidemiological risk factors for tubal ectopic pregnancy are well established and include: tubal damage as a result of surgery or infection (particularly Chlamydia trachomatis), smoking and in vitro fertilization. This review appraises the data to date researching the aetiology of tubal ectopic pregnancy. METHODS Scientific literature was searched for studies investigating the underlying aetiology of tubal ectopic pregnancy. RESULTS Existing data addressing the underlying cause of tubal ectopic pregnancy are mostly descriptive. There are currently few good animal models of tubal ectopic pregnancy. There are limited data explaining the link between risk factors and tubal implantation. CONCLUSIONS Current evidence supports the hypothesis that tubal ectopic pregnancy is caused by a combination of retention of the embryo within the Fallopian tube due to impaired embryo-tubal transport and alterations in the tubal environment allowing early implantation to occur. Future studies are needed that address the functional consequences of infection and smoking on Fallopian tube physiology. A greater understanding of the aetiology of tubal ectopic pregnancy is critical for the development of improved preventative measures, the advancement of diagnostic screening methods and the development of novel treatments.

Proteomic analysis of endometrium from fertile and infertile patients suggests a role for apolipoprotein A-I in embryo implantation failure and endometriosis

Pregnancy is dependent upon the endometrium acquiring a receptive phenotype that facilitates apposition, adhesion and invasion of a developmentally competent embryo. Surface-enhanced laser desorption/ionization time-of-flight mass spectrometry of mid-secretory endometrial biopsies revealed a 28 kDa protein peak that discriminated highly between samples obtained from women with recurrent implantation failure and fertile controls. Subsequent tandem mass spectroscopy unambiguously identified this peak as apolipoprotein A-I (apoA-I), a potent anti-inflammatory molecule. Total endometrial apoA-I levels were, however, comparable between the study and control group. Moreover, endometrial apoA-I mRNA expression was not cycle-dependent although there was partial loss of apoA-I immunoreactivity in luminal and glandular epithelium in mid-secretory compared with proliferative endometrial samples. Because of its putative anti-implantation properties, we examined whether endometrial apoA-I expression is regulated by embryonic signals. Human chorionic gonadotrophin (hCG) strongly inhibited apoA-I expression in differentiating explant cultures but not when established from eutopic endometrium from patients with endometriosis. Pelvic endometriosis was associated with elevated apoA-I mRNA levels, increased secretion by differentiating eutopic endometrial explant cultures and lack of hCG-dependent down-regulation. To corroborate these observations, we examined endometrial apoA-I expression and its regulation by hCG in a non-human primate model of endometriosis. As in humans, hCG strongly inhibited endometrial apoA-I mRNA expression in disease-free baboons, but this response was entirely lost upon induction of pelvic endometriosis. Together, these observations indicate that perturbations in endometrial apoA-I expression, modification or regulation by paracrine embryonic signals play a major role in implantation failure and infertility.

Effect of low-dose mifepristone administration on day 2 after ovulation on transcript profiles in implantation-stage endometrium of rhesus monkeys

Progesterone is essential for endometrial receptivity in primates. In studies previously performed using global gene profiling based on microarray technology, attempts have been made to identify changes in gene expression between early luteal-phase and mid-luteal-phase endometria. However, the issue of the putative impact of preimplantation embryo-derived signal in the process of endometrial receptivity was missing in the previous studies. In the present study, an attempt has been made to delineate the transcripts profile in implantation-stage endometrium under combinatorial regulation of progesterone and embryo-derived signal in the rhesus monkey. To this effect, we have compared transcript profiles for 409 known genes between control receptive stage (n=13), and mifepristone-induced desynchronized and non-receptive stage (n=12) monkey endometrial samples collected on days 4 (n=12) and 6 (n=13) after ovulation from mated, potential conception cycles, using cDNA arrays containing sequence-verified clones. Statistical analysis of correlation of estimated transcript abundance between arrays and qRT-PCR for nine selected gene products yielded significant (P<0.05) concordance. Of 409 genes, a total of 40 gene transcripts were seen to be affected, nine gene transcripts in endometrial samples were found to progressively increase between days 4 and 6 following mifepristone treatment, while an additional five genes showed differential expression profile depending on the day after treatment. Additionally, different sets of 12 and 14 gene products showed changes in days 4 and 6 post-ovulation samples respectively. A new cohort of 28 gene products in implantation-stage endometrium was seen to be affected by luteal-phase mifepristone.

Society for Reproductive Biology Founders' Lecture 2009. Preparing fertile soil: the importance of endometrial receptivity

The human endometrium is receptive for implantation of a blastocyst for only 4–5 days in each menstrual cycle. Failure of implantation is a major reason for infertility in women and the inability to achieve endometrial receptivity is responsible for much of the failure of reproductive technologies. Endometrial receptivity requires changes in the uterine luminal and glandular cells, particularly in terms of their secretory capacity and altered expression of adhesion molecules. In parallel with these changes, decidualisation (differentiation) of the endometrial stroma is initiated in women during the receptive phase, regardless of the presence of a blastocyst. Increased leucocyte numbers are also important. The microenvironments provided by the endometrium during the receptive phase and that support implantation are highly complex and constantly changing as implantation progresses. The present review provides a comprehensive overview of the cellular and molecular events of human implantation. It also summarises work from our laboratories emphasising the functional importance of proprotein convertase 6, along with key cytokines (interleukin-11, leukaemia inhibitory factor, activin A) and chemokines (including CX3CL1 and CCL14), during implantation. Of particular importance is how these mediators contribute to receptivity and how they are disturbed in infertile women. Factors that are critical for uterine receptivity may also be manipulated to provide new contraceptive strategies for women.

The Bysl gene product, bystin, is essential for survival of mouse embryos

Human bystin is a cytoplasmic protein directly binding to trophinin, a cell adhesion molecule potentially involved in human embryo implantation. The present study shows that bystin is expressed in luminal and glandular epithelia in the mouse uterus at peri-implantation stages. In fertilized embryos, bystin was not seen until blastocyst stage. Bystin expression started during hatching and increased in expanded blastocyst. However, bystin apparently disappeared from the blastocyst during implantation. After implantation bystin re-appeared in the epiblast. Targeted disruption of the mouse bystin gene, Bysl, resulted in embryonic lethality shortly after implantation, indicating that bystin is essential for survival of mouse embryos.

Bystin in perineural invasion of prostate cancer

BACKGROUND

Bystin, Trophinin, and Tastin are component proteins of an adhesion molecule complex that plays a crucial role in the initial attachment of the embryo to the uterus.

METHODS

Profiling of genes differentially expressed in the perineural invasion (PNI) in vitro model by gene microarray analysis showed overexpression of bystin in prostate cancer cells co-cultured with nerves. Validation was performed at the RNA levels using quantitative PCR.

RESULTS

Bystin is overexpressed in cells co-cultured with nerves. Bystin is also present in human prostatic carcinoma (PCa) cells in PNI location in increasing gradient. Bystin is present in the supernatant of the PNI co-culture.

CONCLUSIONS

Their adhesive and invasive functions in the trophoblast suggest that they might also play a role in perineural adhesion. Bystin is, therefore, an important therapeutic target for neurotropic cancers.

Expression profile of an operationally-defined neural stem cell clone

Neural stem cells (NSCs) are the most primordial and least committed cells of the nervous system, the cells that exist before regional specification develops. Because immunocytochemically-detectable markers that are sufficiently specific and sensitive to define an NSC have not yet been fully defined, we have taken the strong view that, to be termed a "stem cell" in the nervous system--in contrast to a "progenitor" or "precursor" (whose lineage commitment is further restricted)--a single neuroectodermally-derived cell must fulfill an operational definition that is essentially similar to that used in hematopoiesis. In other words, it must possess the following functional properties: (1) "Multipotency", i.e., the ability to yield mature cells in all three fundamental neural lineages throughout the nervous system--neurons (of all subtypes), astrocytes (of all types), oligodendrocytes--in multiple regional and developmental contexts and in a region and developmental stage-appropriate manner. (2) The ability to populate a developing region and/or repopulate an ablated or degenerated region of the nervous system with appropriate cell types. (3) The ability to be serially transplanted. (4) "Self-renewal", i.e., the ability to produce daughter cells (including new NSCs) with identical properties and potential. Having identified a murine neural cell clone that fulfills this strict operational definition--in contrast to other studies that used less rigorous or non-operational criteria for defining an NSC (e.g., the "neurosphere" assay)--we then examined, by comparing gene expression profiles, the relationship such a cell might have to (a) a multipotent somatic stem cell from another organ system (the hematopoietic stem cell [HSC]); (b) a pluripotent stem cell derived from the inner cell mass and hence without organ assignment (an embryonic stem cell); (c) neural cells isolated and maintained primarily as neurospheres but without having been subjected to the above mentioned operational screen ("CNS-derived neurospheres"). ESCs, HSCs, and operationally-defined NSCs--all of which have been identified not only by markers but by functional assays in their respective systems and whose state of differentiation could be synchronized--shared a large number of genes. Although, as expected, the most stem-like genes were expressed by ESCs, NSCs and HSCs shared a number of genes. CNS-derived neurospheres, on the other hand, expressed fewer "stem-like" genes held in common by the other operationally-defined stem cell populations. Rather they displayed a profile more consistent with differentiated neural cells. (Genes of neural identity were shared with the NSC clone.) Interestingly, when the operationally-defined NSC clone was cultured as a neurosphere (rather than in monolayer), its expression pattern shifted from a "stem-like" pattern towards a more "differentiated" one, suggesting that the neurosphere, without functional validation, may be a poor model for predicting stem cell attributes because it consists of heterogeneous populations of cells, only a small proportion of which are truly "stem-like". Furthermore, when operational definitions are employed, a common set of stem-like genes does emerge across both embryonic and somatic stem cells of various organ systems, including the nervous system.

Drosophila Bys is nuclear and shows dynamic tissue-specific expression during development

Although the bys-like family of genes has been conserved from yeast to humans, it is not apparent to what extent the function of Bys-like proteins has been conserved across phylogenetic groups. Human Bystin is thought to function in a novel cell adhesion complex involved in embryo implantation. The product of the yeast bys-like gene, Enp1, is nuclear and has a role in pre-ribosomal RNA (pre-rRNA) splicing and ribosome biogenesis. To gain insight into the function of the Drosophila melanogaster bys-like family member, termed bys, we examined bys mRNA expression and the localization of Bys protein. In embryos, bys mRNA is expressed in a tissue-specific pattern during gastrulation. In the larval wing imaginal disc, bys mRNA is expressed in the ventral and dorsal regions of the wing pouch, regions that give rise to epithelia that adhere to one another after the wing disc everts. The bys mRNA expression patterns could be interpreted as being consistent with a role for Bys in events requiring cell-cell interactions. However, embryonic bys mRNA expression patterns mirror those of genes that are potential targets of the growth regulator Myc and encode nucleolar proteins implicated in cell growth. Additionally, in Schneider line 2 (S2) cells, an epitope-tagged Bys protein is localized to the nucleus, suggesting that Drosophila Bys function may be conserved with that of yeast Enp1.

In vitro studies on endometrial adhesiveness for trophoblast: cellular dynamics in uterine epithelial cells

Initiation of embryo implantation involves adhesion of trophoblast cells to the epithelial lining of the endometrium. The mechanisms regulating the adhesive properties of the uterine epithelium for trophoblast during initiation of human embryo implantation, however, are still incompletely understood. We report here on model studies that we have performed in our laboratory, and in particular on certain methodological approaches that seem to yield new insight into basic mechanisms involved. Of central interest is the ability of the uterine epithelium to develop an adhesion competence at its apical cell pole. This confronts us with a cell biological paradox in that adhesion must be established at the pole which in simple epithelia is typically specialized to resist adhesion. Gain of apical adhesion competence by uterine epithelial cells should be related to cellular rearrangements, i.e. a modulation of their apicobasal cell polarity. Here, we used monolayer-cultured uterine epithelial RL95-2 cells as an in vitro model for the human receptive uterine epithelium. We demonstrated that formation of stable cell-to-cell bonds between the free (apical) pole of these cells and attaching trophoblast (modelled by JAr cells) depends on a number of structural and functional peculiarities that RL95-2 cells have in contrast to other uterine epithelial cells (HEC-1-A cells) which resist attachment via this cell pole. RL95-2 cells were shown to lack tight junctions and to exhibit only rudimentary adherens junctions and a non-polar organization of the actin cytoskeleton. Using the atomic force microscope in a force spectroscopy mode, we exactly defined the time dependence of adhesive interactions between RL95-2 cells and trophoblast, measured the pressure force needed to initiate this process, and screened the buildup of the adhesive forces between the binding partners. A dynamic interaction between the actin cytoskeleton and integrins (a prerequisite for functional activity of integrins) was shown to be an important aspect of the adhesive properties of RL95-2 cells. In addition, at least two types of calcium channels in the plasma membrane of RL95-2 cells seem to play a role in activation of a variety of calcium-sensitive response mechanisms including adhesiveness for trophoblast, i.e. diltiazem-sensitive channels seem to contribute to the initiation of JAr cell binding and SKF-96365-sensitive channels to participate in a feedback loop that controls the balance of bonds. By extrapolation, these data suggest an active role of the uterine epithelium in the process of embryo implantation which we are just beginning to understand in terms of its cell biology.

Integrins and extracellular matrix proteins at the maternal-fetal interface in domestic animals

Establishment of pregnancy in mammals requires coordinated conceptus-maternal interactions involving numerous hormones, growth factors and cytokines acting via specific receptors in the uterus. Uterine secretions play an important role in establishing synchrony between development of the conceptus and uterine receptivity, as well as in conceptus remodeling, adhesion, implantation and placentation in domestic species. Studies of non-invasive implantation in domestic livestock provide valuable opportunities to investigate fundamental processes of the initial events of apposition, attachment and adhesive interactions that are shared among species. In pigs and sheep, it appears that integrins play a dominant role in these fundamental processes via interactions with extracellular matrix molecules and other ligands to transduce cellular signals in uterine epithelial cells and conceptus trophectoderm. This review considers several of the potential integrin-binding ligands involved in the complex implantation adhesion cascade in pigs and sheep along with in vitro evidence for the transduction of cytoplasmic signals that may be required to sustain fetal and maternal contributions to the formation of the epitheliochorial placenta.

Integrin-mediated adhesion and signaling during blastocyst implantation

Blastocyst implantation in rodents and primates depends on adhesive interactions between trophoblast cells and the endometrial extracellular matrix. As the blastocyst contacts the uterine basal lamina, cells of the trophectoderm become adhesion-competent and conclude their phenotypic conversion from a polarized epithelium to invasive trophoblast cells that anchor the embryo in the uterine wall and eventually infiltrate the endometrium. Trophoblast cells become capable of adhesion to fibronectin as alpha(5)beta(1) integrins traffick to their apical surfaces. While integrin trafficking may be required for trophoblast adhesion to the endometrium, accumulating evidence indicates that, in response to contact with the extracellular matrix, additional molecules must be recruited to the apical surface before strong adhesion is attained. Based on the known interactions of integrins with cytoplasmic regulatory proteins, we propose that extracellular matrix-bound integrins mediate intracellular signaling cascades that strengthen their adhesive activity. We will review some of the known integrin signaling pathways that could regulate trophoblast adhesion and differentiation.