Is MUC1 polymorphism associated with female infertility?

Chimeric virus-like particles presenting tumour-associated MUC1 epitope result in high titers of specific IgG antibodies in the presence of squalene oil-in-water adjuvant: towards safe cancer immunotherapy

Background

Immunotherapy is emerging as a powerful treatment approach for several types of cancers. Modulating the immune system to specifically target cancer cells while sparing healthy cells, is a very promising approach for safer therapies and increased survival of cancer patients. Tumour-associated antigens are favorable targets for cancer immunotherapy, as they are exclusively expressed by the cancer cells, minimizing the risk of an autoimmune reaction. The ability to initiate the activation of the immune system can be achieved by virus-like particles (VLPs) which are safe and potent delivery tools. VLP‐based vaccines have evolved dramatically over the last few decades and showed great potential in preventing infectious diseases. Immunogenic potency of engineered VLPs as a platform for the development of effective therapeutic cancer vaccines has been studied extensively. This study involves recombinant VLPs presenting multiple copies of tumour-specific mucin 1 (MUC1) epitope as a potentially powerful tool for future immunotherapy.

Results

In this report VLPs based on the structural protein of Norovirus (NoV VP1) were genetically modified to present multiple copies of tumour-specific MUC1 epitope on their surface. Chimeric MUC1 particles were produced in the eukaryotic Leishmania tarentolae expression system and used in combination with squalene oil-in-water emulsion MF59 adjuvant to immunize BALB/c mice. Sera from vaccinated mice demonstrated high titers of IgG and IgM antibodies which were specifically recognizing MUC1 antigen.

Conclusions

The obtained results show that immunization with recombinant chimeric NoV VP1- MUC1 VLPs result in high titers of MUC1 specific IgG antibodies and show great therapeutic potential as a platform to present tumour-associated antigens.

Graphical Abstract

Endometrial receptivity and pregnancy outcome

Human implantation is a highly complex and multifactorial process. Successful implantation requires the presence of a healthy embryo, a receptive endometrium, and a synchronized molecular dialogue between the two, as well as immune tolerance/protection from the host. The endometrial receptivity refers to a hormonally limited period in which the endometrial tissue acquires a transient functional status allowing blastocyst implantation and pregnancy initiation. Global knowledge of endometrial receptivity grew up in recent years. Improvements in genetics, new biomarkers, noninvasive methods, new advanced techniques (Endometrial receptivity assay - the ERA system, proteomic analysis) offer the possibility to evaluate the endometrial status and to manage patients with infertility problems, especially women undergoing assisted reproductive treatment. This overview reports the most relevant knowledge and recent advances in the study of implantation processes from the perspective of the endometrium, often considered as being the main barrier for a successful pregnancy initiation. Endometrial receptivity is a topic of great interest and further studies are needed for the early identification of endometrial abnormalities and the discovery of new strategies for increasing the chance for the establishment of pregnancy.

Single domain based bispecific antibody, Muc1-Bi-1, and its humanized form, Muc1-Bi-2, induce potent cancer cell killing in muc1 positive tumor cells

Muc1 is one of the most studied tumor antigens. However, antibodies or antibody-toxin conjugates against Muc1 have not shown significant efficacy for tumors with Muc1 overexpression. In this study, we employed bispecific antibody approach to target Muc1 positive tumor cells. A novel bispecific antibody, Muc1-Bi-1, was constructed by linking single domain antibodies, anti-Muc1-VHH and anti-CD16-VHH. Muc1-Bi-2, the humanized form of Muc1-Bi-1, was also constructed by grafting. Both Muc1-Bi bispecific antibodies can be efficiently expressed and purified from bacteria. In vitro, the Muc1-Bi bispecific antibodies can recruit Natural Killer (NK) cells to drive potent and specific cell killing of Muc1-overexpressing tumor cells. In xenograft model, the Muc1-Bi bispecific antibodies can suppress tumor growth in the presence of human peripheral blood mononuclear cells (PBMC). These data suggested that the single domain based Muc1-Bi may provide a valid strategy for targeting tumors with Muc1 overexpression.

Molecular basis of thyrotropin and thyroid hormone action during implantation and early development

BACKGROUND

Implantation and early embryo development are finely regulated processes in which several molecules are involved. Evidence that thyroid hormones (TH: T4 and T3) might be part of this machinery is emerging. An increased demand for TH occurs during gestation, and any alteration in maternal thyroid physiology has significant implications for both maternal and fetal health. Not only overt but also subclinical hypothyroidism is associated with infertility as well as with obstetric complications, including disruptions and disorders of pregnancy, labor, delivery, and troubles in early neonatal life.

METHODS

We searched the PubMed and Google Scholar databases for articles related to TH action on ovary, endometrium, trophoblast maturation and embryo implantation. In addition, articles on the regulation of TH activity at cellular level have been reviewed. The findings are hereby summarized and critically discussed.

RESULTS

TH have been shown to influence endometrial, ovarian and placental physiology. TH receptors (TR) and thyrotropin (thyroid-stimulating hormone: TSH) receptors (TSHR) are widely expressed in the feto-maternal unit during implantation, and both the endometrium and the trophoblast might be influenced by TH either directly or through TH effects on the synthesis and activity of implantation-mediating molecules. Interestingly, due to the multiplicity of mechanisms involved in TH action (e.g. differential expression of TR isoforms, heterodimeric receptor partners, interacting cellular proteins, and regulating enzymes), the TH concentration in blood is not always predictive of their cellular availability and activity at both genomic and nongenomic level.

CONCLUSIONS

In addition to the known role of TH on the hormonal milieu of the ovarian follicle cycle, which is essential for a woman's fertility, evidence is emerging on the importance of TH signaling during implantation and early pregnancy. Based on recent observations, a local action of TH on female reproductive organs and the embryo during implantation appears to be crucial for a successful pregnancy. Furthermore, an imbalance in the spatio-temporal expression of factors involved in TH activity might induce early arrest of pregnancy in women considered as euthyroid, based on their hormonal blood concentration. In conclusion, alterations of the highly regulated local activity of TH may play a crucial, previously underestimated, role in early pregnancy and pregnancy loss. Further studies elucidating this topic should be encouraged.

Molecular aspects of implantation failure

Despite expanding global experience with advanced reproductive technologies, the majority of IVF attempts do not result in a successful pregnancy, foremost as a result of implantation failure. The process of embryo implantation, a remarkably dynamic and precisely controlled molecular and cellular event, appears inefficient in humans and is poorly understood. However, insights gained from clinical implantation failure, early pregnancy loss, and emerging techologies that enable molecular interrogation of endometrial-embryo interactions are unravelling this major limiting step in human reproduction. We review current molecular concepts thought to underlie implantation failure, consider the contribution of embryonic and endometrial factors, and discuss the clinical value of putative markers of impaired endometrial receptivity. Finally we highlight the nature of the dialogue between the maternal endometrium and the implanting embryo and discuss the concept of natural embryo selection. This article is part of a Special Issue entitled: Molecular Genetics of Human Reproductive Failure.

Effect of VNTR polymorphism of the Muc1 gene on litter size of pigs

An investigation was undertaken to study the association between the variable number of tandem repeats polymorphism of the Muc1 gene and the litter size in pigs. Four different alleles were found in three breeds. The sequence analysis shows that the repetitive region of pig Muc1 gene is an array of 108-bp repeats. A total of 2,430 litter records from 897 sows genotyped at Muc1 gene were used to analyze the total number born (TNB) and number born alive (NBA). The study of the effects on litter size suggests that TNB and NBA of genotype AA are the highest in Large White, and the TNB and NBA of the third to ninth parities are 1.61 and 2.29 piglets per litter higher (P < 0.05) than those of the genotype DD, respectively. In Landrace, TNB and NBA of the genotype AA are 1.68 (P < 0.01) and 1.58 (P < 0.05) piglets per litter higher than those of the BB genotype in the third to ninth parities, but for all parities the TNB of genotype AA were 0.76 piglets per litter (P < 0.05) higher than BB. In Duroc, the TNB and NBA of genotype AA are about 1.5 piglets per litter more than those of DD in the third to ninth parities, though not significantly. The research suggests that the smaller allele tends to have higher litter size. The results indicate that Muc1 gene is significantly associated with litter size in pigs.

MUC1 gene polymorphism in three Nelore lines selected for growth and its association with growth and carcass traits

The objective of this study was to describe the VNTR polymorphism of the mucin 1 gene (MUC1) in three Nelore lines selected for yearling weight to determine whether allele and genotype frequencies of this polymorphism were affected by selection for growth. In addition, the effects of the polymorphism on growth and carcass traits were evaluated. Birth, weaning and yearling weights, rump height, Longissimus muscle area, backfat thickness, and rump fat thickness, were analyzed. A total of 295 Nelore heifers from the Beef Cattle Research Center, Instituto de Zootecnia de Sertãozinho, were used, including 41 of the control line, 102 of the selection line and 152 of the traditional. The selection and traditional lines comprise animals selected for higher yearling weight, whereas control line animals are selected for yearling weight close to the average. Five alleles were identified, with allele 1 being the most frequent in the three lines, especially in the lines selected for higher means for yearling weight. Heterozygosity was significantly higher in the control line. Association analyses showed significant effects of allele 1 on birth weight and weaning weight while the allele 3 exert significant effects on yearling weight and back fat thickness. Despite these findings, application of this marker to marker-assisted selection requires more consistent results based on the genotyping of a larger number of animals in order to increase the accuracy of the statistical analyses.

No evidence of association of MUC-1 genetic polymorphism with embryo implantation failure

Pregnancy loss can be caused by several factors involved in human reproduction. Although up to 50% of cases remain unexplained, it has been postulated that the major cause of failed pregnancy is an error of embryo implantation. Transmembrane mucin-1 (MUC-1) is a glycoprotein expressed on the endometrial cell surface which acts as a barrier to implantation. The gene that codes for this molecule is composed of a polymorphic tandem repeat of 60 nucleotides. Our objective was to determine if MUC-1 genetic polymorphism is associated with implantation failure in patients with a history of recurrent abortion. The study was conducted on 10 women aged 25 to 35 years with no history of successful pregnancy and with a diagnosis of infertility. The control group consisted of 32 patients aged 25 to 35 years who had delivered at least two full-term live children and who had no history of abortions or fetal losses. MUC-1 amplicons were obtained by PCR and observed on agarose and polyacrylamide gel after electrophoresis. Statistical analysis showed no significant difference in the number of MUC-1 variable number of tandem repeats between these groups (P > 0.05). Our results suggest that there is no effect of the polymorphic MUC-1 sequence on the implantation failure. However, the data do not exclude MUC-1 relevance during embryo implantation. The process is related to several associated factors such as the mechanisms of gene expression in the uterus, specific MUC-1 post-translational modifications and appropriate interactions with other molecules during embryo implantation.

The polymorphism in MUC1 gene in Nelore cattle

MUC1 is a transmembrane glycoprotein expressed on the apical surfaces of the uterine epithelial tissue with predicted functions in protection and cell-cell adhesion. These properties are closely related with the repetitive region [variable number of tandem repeats (VNTR)] of the extracellullar domain and with the O-glycosylation in their serine and threonine residues. This study describes a polymerase chain reaction (PCR) protocol to analyse MUC1 bovine genetic polymorphism and demonstrates the existence of a VNTR within the sites for O-glycosylation. Oligonucleotide primers based on the Bos taurus mucin (MUC1) gene sequence GenBank AF399757 were used to amplify five VNTR MUC1 alleles from a study group of 56 pure Nelore bovines. The number of repeats varied between 10 and 24, being more prevalent than the alleles with less number of repeats. The DNA sequence analysis revealed two repeats and one of them presented 100% homology with the bovine consensus sequence already reported. The second repeat showed codons that translate to serine and proline amino acids, which are conserved in the MUC1 of several species. This study is the first description of allelic variation and the VNTR structure in the Nelore breed MUC1 gene, and we suggest that this genetic variability can be tested for association with variation in reproductive traits in Nelore cattle.

Embryo implantation: the molecular mechanism remains elusive

Low rates of implantation are an impediment to more efficient assisted reproduction techniques. Improved endometrial receptivity and embryo preparation should lead to higher pregnancy rates, lower rates of early pregnancy failure and fewer multiple pregnancies. As the first site of contact between embryo and endometrium, the luminal epithelium (LE) is responsible for the non-receptive status of proliferative and early secretory tissue, and transformation to receptivity in the mid-secretory phase presumably requires alterations in expression, organization or activation of adhesion systems. Luminal cells are less abundant than their glandular counterparts, and are under-represented in global tissue datasets. Furthermore, alterations in cell surface composition can be readily accomplished by mechanisms that do not rely on altered transcription or translation. Current data from in-vitro models are consistent with initial attachment to mucin in the apical glycocalyx, perhaps via a carbohydrate-mediated interaction, after which the epithelial phenotype is modified by a medium- or short-range embryonic signal. A cascade of interactions follows, mediating embryo migration across the epithelium. Strikingly, numerous potential mediators of adhesion at implantation are located in the lateral rather than the apical surface of LE cells. Attached embryos appear to gain rapid access to this highly adhesive lateral membrane domain.

MUC1 as a target antigen for cancer immunotherapy

The cancer-associated antigen MUC1 is overexpressed and modified by tumor cells in over half of all cancer cases. Despite various complexities associated with this antigen, it is well worth pursuing as a vaccine for the immunotherapy of cancer. In this review, the authors describe the discovery of MUC1 and its association with cancer, recent observations showing that the immunology of MUC1 is complicated, animal data showing that it can be a target for immune-mediated tumor rejection, and finally, preliminary clinical results to show that vaccine-based immunotherapy with MUC1 does have an impact on the therapy of cancer.

Clinical value of endometrial pinopodes detection in artificial donation cycles

The aim of the study was to investigate the clinical value of pinopode detection in women with a history of multiple implantation failures after participation in assisted reproduction programmes. Forty-six women with primary infertility, three or more previous implantation failures in assisted reproduction programmes and indication for the use of donated oocytes underwent a mock cycle of endometrial preparation, based on a standard protocol. Endometrial samples were taken on days 6 and 8 of progesterone administration, and were examined under scanning electron microscope for detection and evaluation of pinopodes. The most receptive endometrial day (the day on which fully developed pinopodes can be demonstrated) was determined for each woman. In 73.91%, a new modified transfer cycle was suggested and applied by altering the timing between IVF and progesterone commencement days; 76.47% achieved a clinical pregnancy within two attempts and 67.64% delivered a healthy baby. Among women with no indication for modification of their transfer cycle, only 33.33% achieved a pregnancy and 25% delivered a healthy baby. The difference in the outcomes between transfer cycles with and without modification was significant. In conclusion, detection of pinopodes in women with multiple implantation failures can be of great clinical value.