Understanding the Mechanisms of Diminished Ovarian Reserve: Insights from Genetic Variants and Regulatory Factors

Delaying childbearing age has become a trend in modern times, but it has also led to a common challenge in clinical reproductive medicine-diminished ovarian reserve (DOR). Since the mechanism behind DOR is unknown and its clinical features are complex, physicians find it difficult to provide targeted treatment. Many factors affect ovarian reserve function, and existing studies have shown that genetic variants, upstream regulatory genes, and changes in protein expression levels are present in populations with reduced ovarian reserve function. However, existing therapeutic regimens often do not target the genetic profile for more individualized treatment. In this paper, we review the types of genetic variants, mutations, altered expression levels of microRNAs, and other related factors and their effects on the regulation of follicular development, as well as altered DNA methylation. We hope this review will have significant implications for the future treatment of individuals with reduced ovarian reserve.

Precision nutrition to reset virus-induced human metabolic reprogramming and dysregulation (HMRD) in long-COVID

SARS-CoV-2, the etiological agent of COVID-19, is devoid of any metabolic capacity; therefore, it is critical for the viral pathogen to hijack host cellular metabolic machinery for its replication and propagation. This single-stranded RNA virus with a 29.9 kb genome encodes 14 open reading frames (ORFs) and initiates a plethora of virus-host protein-protein interactions in the human body. These extensive viral protein interactions with host-specific cellular targets could trigger severe human metabolic reprogramming/dysregulation (HMRD), a rewiring of sugar-, amino acid-, lipid-, and nucleotide-metabolism(s), as well as altered or impaired bioenergetics, immune dysfunction, and redox imbalance in the body. In the infectious process, the viral pathogen hijacks two major human receptors, angiotensin-converting enzyme (ACE)-2 and/or neuropilin (NRP)-1, for initial adhesion to cell surface; then utilizes two major host proteases, TMPRSS2 and/or furin, to gain cellular entry; and finally employs an endosomal enzyme, cathepsin L (CTSL) for fusogenic release of its viral genome. The virus-induced HMRD results in 5 possible infectious outcomes: asymptomatic, mild, moderate, severe to fatal episodes; while the symptomatic acute COVID-19 condition could manifest into 3 clinical phases: (i) hypoxia and hypoxemia (Warburg effect), (ii) hyperferritinemia ('cytokine storm'), and (iii) thrombocytosis (coagulopathy). The mean incubation period for COVID-19 onset was estimated to be 5.1 days, and most cases develop symptoms after 14 days. The mean viral clearance times were 24, 30, and 39 days for acute, severe, and ICU-admitted COVID-19 patients, respectively. However, about 25-70% of virus-free COVID-19 survivors continue to sustain virus-induced HMRD and exhibit a wide range of symptoms that are persistent, exacerbated, or new 'onset' clinical incidents, collectively termed as post-acute sequelae of COVID-19 (PASC) or long COVID. PASC patients experience several debilitating clinical condition(s) with >200 different and overlapping symptoms that may last for weeks to months. Chronic PASC is a cumulative outcome of at least 10 different HMRD-related pathophysiological mechanisms involving both virus-derived virulence factors and a multitude of innate host responses. Based on HMRD and virus-free clinical impairments of different human organs/systems, PASC patients can be categorized into 4 different clusters or sub-phenotypes: sub-phenotype-1 (33.8%) with cardiac and renal manifestations; sub-phenotype-2 (32.8%) with respiratory, sleep and anxiety disorders; sub-phenotype-3 (23.4%) with skeleto-muscular and nervous disorders; and sub-phenotype-4 (10.1%) with digestive and pulmonary dysfunctions. This narrative review elucidates the effects of viral hijack on host cellular machinery during SARS-CoV-2 infection, ensuing detrimental effect(s) of virus-induced HMRD on human metabolism, consequential symptomatic clinical implications, and damage to multiple organ systems; as well as chronic pathophysiological sequelae in virus-free PASC patients. We have also provided a few evidence-based, human randomized controlled trial (RCT)-tested, precision nutrients to reset HMRD for health recovery of PASC patients.

Supplementation with fibroblast growth factor 7 during in vitro maturation of porcine cumulus-oocyte complexes improves oocyte maturation and early embryonic development

In vitro generation of porcine embryos is an indispensable method in the realms of both agriculture and biomedicine. Nonetheless, the extant procedures encounter substantial obstacles pertaining to both the caliber and efficacy of the produced embryos, necessitating extensive research to in vitro maturation (IVM), the seminal commencement phase. One potentially fruitful approach may lie in refining the media and supplements composition utilized for oocyte maturation. Fibroblast growth factor-7 (FGF7), alternatively termed keratinocyte growth factor, is a theca-derived cytokine integral to folliculogenesis. This study aimed to examine the ramifications of supplementing FGF7 during the IVM phase. To determine the FGF7 location and its receptor in porcine ovaries, immunohistochemistry was executed based on follicle size categories (1-2, 3-6, and 7-9 mm). Regardless of follicle size, it was determined that FGF7 was expressed in theca and granulosa cells (GCs), whereas the FGF7 receptor was only expressed in the GCs of the larger follicles. During the IVM process, the maturation medium was supplied with various concentrations of FGF7, aiming to mature porcine cumulus-oocyte complexes (COCs). The data indicated a significant augmentation in the nuclear maturation rate only within the group treated with 10 ng/mL of FGF7 (p < 0.05). Post-IVM, the oocytes diameter exhibited a significant expansion in all groups that received FGF7 supplementation (p < 0.05). Additionally, all FGF7-supplemented groups exhibited a substantial elevation in intracellular glutathione levels, coupled with a noticeable reduction in reactive oxygen species levels (p < 0.05). With respect to gene expressions related to apoptosis, FGF7 treatment elicited a downregulation of pro-apoptotic genes and an upregulation of anti-apoptotic genes. The expression of genes associated with antioxidants underwent a significant enhancement (p < 0.05). In terms of the FGF7 signaling pathway-associated genes, there was a significant elevation in the mRNA expression of ERK1, ERK2, c-kit, and KITLG (p < 0.05). Remarkably, the group of 10 ng/mL of FGF7 demonstrated an appreciable uptick in the blastocyst formation rate during embryonic development post-parthenogenetic activation (p < 0.05). In conclusion, the FGF7 supplementation during IVM substantially augments the quality of matured oocytes and facilitates the subsequent development of parthenogenetically activated embryos. These results offer fresh perspectives on improved maturation and following in vitro evolution of porcine oocytes.

Tissue Transglutaminase Knock-Out Preadipocytes and Beige Cells of Epididymal Fat Origin Possess Decreased Mitochondrial Functions Required for Thermogenesis

Beige adipocytes with thermogenic function are activated during cold exposure in white adipose tissue through the process of browning. These cells, similar to brown adipocytes, dissipate stored chemical energy in the form of heat with the help of uncoupling protein 1 (UCP1). Recently, we have shown that tissue transglutaminase (TG2) knock-out mice have decreased cold tolerance in parallel with lower utilization of their epididymal adipose tissue and reduced browning. To learn more about the thermogenic function of this fat depot, we isolated preadipocytes from the epididymal adipose tissue of wild-type and TG2 knock-out mice and differentiated them in the beige direction. Although differentiation of TG2 knock-out preadipocytes is phenotypically similar to the wild-type cells, the mitochondria of the knock-out beige cells have multiple impairments including an altered electron transport system generating lower electrochemical potential difference, reduced oxygen consumption, lower UCP1 protein content, and a higher portion of fragmented mitochondria. Most of these differences are present in preadipocytes as well, and the differentiation process cannot overcome the functional disadvantages completely. TG2 knock-out beige adipocytes produce more iodothyronine deiodinase 3 (DIO3) which may inactivate thyroid hormones required for the establishment of optimal mitochondrial function. The TG2 knock-out preadipocytes and beige cells are both hypometabolic as compared with the wild-type controls which may also be explained by the lower expression of solute carrier proteins SLC25A45, SLC25A47, and SLC25A42 which transport acylcarnitine, Co-A, and amino acids into the mitochondrial matrix. As a consequence, the mitochondria in TG2 knock-out beige adipocytes probably cannot reach the energy-producing threshold required for normal thermogenic functions, which may contribute to the decreased cold tolerance of TG2 knock-out mice.

The effects of H22 tumor on the quality of oocytes and the development of early embryos from host mice: A single-cell RNA sequencing approach

The association between cancer and female reproduction remains largely unknown. Here we investigated the quality of oocytes and the developmental potential of zygotes using H22 tumor-bearing mice model. The results showed that the number of oocytes was decreased in tumor-bearing mice compared with the control mice, and accompanied scattered chromosomes was observed. Further study revealed an abnormal epigenetic reprogramming occurred in the zygotes from the H22 tumor-bearing mice, as exemplified by the aberrant 5hmC/5mC modifications in the pronuclei. Finally, single-cell RNA sequencing was performed on the oocytes collected from the H22 tumor-bearing mice. Our data showed that 45 of the 202 differentially expressed genes in tumor-bearing group were closely associated with oocyte quality. Protein interaction analysis indicated that the potential interaction among these 45 genes. Collectively, our study uncovered that the quality of oocytes and early embryonic development were affected by H22 tumor bearing via the altered expression patterns of genes related with reproduction, providing new insights into the reproductive capability of female cancer patients.

Comparative transcriptomic analysis reveals the gonadal development-related gene response to environmental temperature in Mauremys mutica

The Asian yellow pond turtle (Mauremys mutica) displays temperature-dependent sex determination (TSD), in which incubation temperature during embryonic development determines the sexual fate of the individual. However, the mechanism of the sex determination/differentiation of Mauremys mutica remains a mystery. Here, we first analyzed the temperature-specific gonadal transcriptomes of Mauremys mutica prior to gonad formation and gonads during the thermosensitive period. We uncovered a list of candidates that respond to temperature stimuli enriched in several categories, such as heat shock protein family members dnajb6a, dnaja4, hspa8 and hsp90aa1, temperature sensor genes mmp17 and mmp28, and putative novel temperature-responsive genes tmco6, gria3 and eif3f. Notably, striking differences were identified in the expression profiles of genes underlying sexual development, such as tex15, insr, igf1r, cirbp, esr1, dmrt2 and Serpinh1. Moreover, we analyzed the similarity and divergence of the timecourse of gene expression among Mauremys mutica and two other reported TSD turtles (Trachemys scripta and Chrysemys picta). The shared genes revealed the common gonad-specific regulatory mechanisms existing in these three TSD turtles that initiate their sexual development. Therefore, our findings could provide basic data to elucidate the mechanisms of sex determination/differentiation of M. mutica, even contributing to further understanding of these mechanisms in other TSD turtles.

Gm364 coordinates MIB2/DLL3/Notch2 to regulate female fertility through AKT activation

Many integral membrane proteins might act as indispensable coordinators in specific functional microdomains to maintain the normal operation of known receptors, such as Notch. Gm364 is a multi-pass transmembrane protein that has been screened as a potential female fertility factor. However, there have been no reports to date about its function in female fertility. Here, we found that global knockout of Gm364 decreased the numbers of primordial follicles and growing follicles, impaired oocyte quality as indicated by increased ROS and γ-H2AX, decreased mitochondrial membrane potential, decreased oocyte maturation, and increased aneuploidy. Mechanistically, Gm364 directly binds and anchors MIB2, a ubiquitin ligase, on the membrane. Subsequently, membrane MIB2 ubiquitinates and activates DLL3. Next, the activated DLL3 binds and activates Notch2, which is subsequently cleaved within the cytoplasm to produce NICD2, the intracellular active domain of Notch2. Finally, NICD2 can directly activate AKT within the cytoplasm to regulate oocyte meiosis and quality.

Furin is involved in uterine activation for labor

The uterus undergoes distinct molecular and functional changes during pregnancy and parturition. These processes are associated with the dramatic changes in various proteins. Given that the maturation and activation of many proteins require proteolytic processing by proprotein convertases (PCs), we sought to explore the role of PCs in uterine activation for labor. First, we found that furin was the most dramatically increased PC member in myometrial tissues from the pregnant women after onset of labor at term. Using the model of cultured human myometrial smooth muscle cells (HMSMCs), we showed that furin inhibitor CMK, D6R treatment and furin siRNA transfection suppressed contractility. Inhibition of furin activity or interfering furin expression decreased connexin 43 (CX43), prostaglandin (PG) endoperoxide synthase-2 (COX-2) and PGF2α receptor (FP) expression and NF-κB activation. In mouse model, administration of furin inhibitors prolonged gestational length. However, D6R treatment did not affect RU38486- and lipopolysaccharides (LPS)-induced preterm birth. Furthermore, D6R and furin siRNA treatment reduced the release of soluble form of tumor necrosis factor (TNF)-related weak inducer of apoptosis (TWEAK), while furin overexpression led to an increase in soluble TWEAK release in cultured HMSMCs. D6R treatment decreased TWEAK level in blood of pregnant mice. TWEAK treatment promoted contractility and NF-κB activation, while TWEAK receptor fibroblast growth factor-inducible 14 (FN14) antagonist treatment inhibited contractility and NF-κB activation in HMSMCs. In pregnant mice, administration of FN14 antagonist prolonged gestational length. Our data suggest that furin can act as a stimulator for uterine activation for labor at term. TWEAK is one of the potential substrates which mediate furin regulation of parturition initiation.

Placenta-specific protein 1 promotes cell proliferation via the AKT/GSK-3β/cyclin D1 signaling pathway in gastric cancer

Gastric cancer is a malignant tumor with a poor prognosis. Therefore, it is important to search for molecules that play a vital role in the development, diagnosis, and treatment of this disease. Placenta-specific 1 (PLAC1) is one of the cancer-testis antigens; it plays an important role in both placental development and tumorigenesis. However, the role of PLAC1 in gastric cancer has not been fully investigated, and its underlying mechanism needs further study. We first explored the expression and clinical relevance of PLAC1 in gastric cancer and performed gene set enrichment analysis of PLAC1-related genes using online databases. Subsequently, we studied the function and mechanism of PLAC1 in gastric cancer cells through in vitro experiments. Our results showed that PLAC1 is highly expressed in gastric cancer, is associated with poor prognosis, and can promote gastric cancer cell proliferation through the AKT/GSK-3β/cyclin D1 signaling pathway. Moreover, we discovered that AKTi attenuates the effect of PLAC1. Our study further revealed the role and mechanism of PLAC1 in gastric cancer and suggested that this antigen might be a useful molecular marker for gastric cancer diagnosis, prognosis, and treatment.

GTPases Arf5 and Arl2 function partially distinctly during oocyte meiosis

Mammalian female meiosis must be tightly regulated to produce high-quality mature oocytes for subsequent regular fertilization and healthy live birth of the next generation. GTPases control many important signal pathways involved in diverse cellular activities. ADP-ribosylation factor family members (Arfs) in mice possess GTPase activities, and some members have been found to function in meiosis. However, whether other Arfs play a role in meiosis is unknown. In this study, we found that Arl2 and Arf5 are the richest among Arfs in mouse oocytes, and they are more abundant in oocytes than in granular cells. Furthermore, Arl2 and Arf5 depletion both impeded meiotic progression, but by affecting spindles and microfilaments, respectively. Moreover, Arl2 and Arf5 depletion both significantly increased regular reactive oxygen species levels and decreased mitochondrial membrane potential and autophagy, indicating that oocyte quality was damaged by Arl2 and Arf5 depletion. These results suggest that Arl2 and Arf5 are two novel essential GTPases required for oocyte meiosis and quality control.

Aryl hydrocarbon receptor (AhR) agonist β-naphthoflavone regulated gene networks in human primary trophoblasts

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that is highly expressed in placenta. AhR belongs to a class of transcriptional regulators that control many developmental and physiological events (e.g. xenobiotic metabolism). Our study describes AhR regulated transcriptional responses in human primary trophoblast by using the AhR agonist, β-naphthoflavone (BNF). Human primary trophoblast cells were isolated from full term placenta after delivery. The trophoblasts were exposed to 25 μM of AhR agonist, BNF, for 72 hours. Gene expression profiling was conducted with Illumina HT-12 expression beadchips. Expression of selected genes was confirmed with RT-qPCR. Ingenuity pathway analysis (IPA) was used to predict functional pathways and upstream regulators of differentially expressed genes in order to identify regulatory networks associated with AhR. In response to BNF exposure, 64 genes were upregulated, and 257 genes were downregulated compared to control trophoblasts (±1.5-fold, p < 0.05). BNF regulated genes included placental hormones and genes implicated in immune- and inflammatory responses in addition to their well-known effects on xenobiotic metabolism, oxidative stress, antioxidant defense. In conclusion, these results show that BNF has wide-ranging effects on placental gene expression beyond xenobiotic metabolism e.g. disruption of inflammatory processes and hormones in the placenta.

Fam70A binds Wnt5a to regulate meiosis and quality of mouse oocytes

OBJECTIVES

Little is known about the roles of integral membrane proteins beyond channels, carriers or receptors in meiotic oocytes. The transmembrane protein Fam70A was previously identified as a likely "female fertility factor" in Fox3a-knockout mouse ovaries where almost all follicles underwent synchronous activation and the mice became infertile very early. However, whether Fam70A functions in oocyte meiosis remains unknown. Therefore, the present study aimed to address this question.

MATERIALS AND METHODS

Co-immunoprecipitation, immunogold labelling-electron microscopy, co-localization and yeast two-hybrid assays were used to verify the interaction. Antibody or small interfering RNA transfection was used to deplete the proteins. Immunofluorescence, immunohistochemistry and live tracker staining were used to examine the localization or characterize phenotypes. Western blot was used to examine the protein level.

RESULTS

Fam70A was enriched in oocyte membranes important for normal meiosis. Fam70A depletion remarkably disrupted spindle assembly, chromosome congression and first polar body extrusion, which subsequently increased aneuploidy and abnormal fertilization. Moreover, Fam70A directly bound Wnt5a, the most abundant Wnt member within oocytes. Depletion of either Fam70A or Wnt5a remarkably increased adenomatous polyposis coli (APC), which stabilizes active β-catenin and microtubules. Consequently, depletion of either Fam70A or Wnt5a remarkably increased p-β-catenin (inactive form) and acetylated tubulin, while APC knockdown remarkably decreased these two. Furthermore, Fam70A depletion remarkably reduced Akt phosphorylation.

CONCLUSIONS

Fam70A regulates meiosis and quality of mouse oocytes through both canonical and non-canonical Wnt5a signalling pathways.

High-throughput sequencing analysis identified microRNAs associated with egg production in ducks ovaries

BACKGROUND

MicroRNAs (miRNAs) exist widely and are involved in multiple biological processes in ducks, whereas the regulatory mechanism of miRNAs in egg laying of ducks has remained unclear. This study aims to reveal key miRNAs involved in the regulation of egg production in duck ovaries.

METHODS

High-throughput sequencing was performed on four egg-type duck ovaries and four egg-meat-type duck ovaries at the start of the egg-laying stage. Quantitative reverse transcription PCR (qRT-PCR) validation was performed on differentially expressed miRNAs (DE miRNAs). Gene network of DEmiRNA-mRNA-pathway was constructed by Cytoscape.

RESULTS

A total of 251 know miRNAs and 1,972 novel miRNAs were obtained from whole clean reads. Among the known miRNAs, we identified 21 DEmiRNAs, including eight down-regulated and 13 up-regulated miRNAs in egg-type ducks compared with egg-meat-type ducks. Among the novel miRNAs, we identified 70 DEmiRNAs, including 58 down-regulated and 12 up-regulated in egg-type ducks compared with egg-meat-type ducks. The expression patterns of four miRNAs were verified by qRT-PCR. The DEmiRNAs were involved in the function of response to folic acid and the pathway of valine, leucine and isoleucine degradation. Specific target genes of DEmiRNAs enrichment was found in some egg-laying regulation pathways, such as dopaminergic synapse, ovarian steroidogenesis and oocyte meiosis. The DEmiRNA-mRNA-pathway network including three DEmiRNAs, nine mRNAs and 11 pathways. apl-miR-194-5p and apl-miR-215-5p may be potential key miRNAs in regulating egg laying.

CONCLUSIONS

This study provided miRNAs profiles in ducks about egg laying and establish a theoretical basis for subsequent selection or modification of duck phenotypes at the molecular level.

The 5.8S pre-rRNA maturation factor, M-phase phosphoprotein 6, is a female fertility factor required for oocyte quality and meiosis

Objectives

M‐phase phosphoprotein 6 (MPP6) is important for 5.8S pre‐rRNA maturation in somatic cells and was screened as a female fertility factor. However, whether MPP6 functions in oocyte meiosis and fertility is not yet known. We aimed to address this.

Materials and Methods

Mouse oocytes with surrounded nucleus (SN) or non‐surrounded nucleus (NSN) were used for all experiments. Peptide nanoparticle‐mediated antibody transfection was used to deplete MPP6. Immunofluorescence staining, immunohistochemistry and live tracker staining were used to examine MPP6 localization and characterize phenotypes after control or MPP6 depletion. High‐fidelity PCR and fluorescence in situ hybridization (FISH) were used to examine the localization and level of 5.8S rRNAs. Western blot was used to examine the protein level. MPP6‐EGFP mRNA microinjection was used to do the rescue.

Results

MPP6 was enriched within ovaries and oocytes. MPP6 depletion significantly impeded oocyte meiosis. MPP6 depletion increased 5.8S pre‐rRNA. The mRNA levels of MPP6 and 5.8S rRNA decreased within ageing oocytes, and MPP6 mRNA injection partially increased 5.8S rRNA maturation and improved oocyte quality.

Conclusions

MPP6 is required for 5.8S rRNA maturation, meiosis and quality control in mouse oocytes, and MPP6 level might be a marker for oocyte quality.

Placenta specific protein-1 in recurrent pregnancy loss and in In Vitro Fertilisation failure: a prospective observational case-control study

Observations from studies have provided evidence that Placenta-specific protein1 (PLAC1) is important for the establishment and maintenance of pregnancy and suggest it as a potential biomarker for gestational pathologies. The aim of this study is to investigate whether maternal serum PLAC1 levels have any impact on etiopathogenesis of recurrent pregnancy loss (RPL) and repeated implantation failure after In Vitro Fertilisation (RIF). We conducted a prospective observational case-control study in a Research Hospital. Twenty-eight patients with RPL (group 1), 30 patients with unexplained infertility and RIF (group 2), 29 fertile patients (group 3) were included. The demographic features and serum PLAC1 levels were compared. There was a significant difference in PLAC1 levels between the groups (group 1 = 19.71 + 16.55 ng/ml; group 2 = 4.82 + 1.44 ng/ml; group 3 = 0.89 + 0.62 ng/ml, respectively) (p=.001). Positive correlation was found between serum PLAC1 levels and abortion rates (r = 0.64; p=.001), a negative correlation was found between serum PLAC1 levels and live birth rates (r = -0.69; p=.001). PLAC1 might have a negative effect on implantation in RPL and RIF. There may be a subgroup of PLAC with different bioactivity. There are no relevant studies conducted among these populations, further large-scale studies are needed to assess the molecular role of PLAC1 on implantation.IMPACT STATEMENTWhat is already known about this subject? PLAC1 (placenta-specific protein-1) gene is located on the X chromosome which encodes for a protein that is thought to be important for placental development although its role has not been clearly defined. Studies in the literature have provided evidence that PLAC1 has an important role in the establishment and maintenance of pregnancy and suggest it as a potential biomarker for gestational pathologies. Several reports over the past few years have demonstrated PLAC1 expression in a variety of human tumours including lung cancers, breast cancer, hepatocellular and colorectal cancers, gastric cancers and uterine cancers.What do the results of this study add? There have been no previous studies conducted among patients with recurrent pregnancy loss (RPL) or repeated implantation failure after In Vitro Fertilisation (RIF) that have searched for any association between PLAC1 levels and implantation failure. This study has demonstrated higher PLAC1 levels in infertile women with RIF and RPL for the first time; suggesting that it could have a negative effect on implantation in these populations. PLAC1 could be detected in the serum as a biomarker that is associated with RIF and RPL. What are the implications of these findings for clinical practice and/or further research? Defining the precise role of PLAC1 during implantation will provide new insight into understanding of poor reproductive outcomes such as RIF and RPL and help in developing treatment strategies. Further large-scale studies with more patients are needed to uncover the clinical value of PLAC1 as a biomarker to predict repeated implantation failure and RPL.

PLAC1: biology and potential application in cancer immunotherapy

The emergence of immunotherapy has revolutionized medical oncology with unprecedented advances in cancer treatment over the past two decades. However, a major obstacle in cancer immunotherapy is identifying appropriate tumor-specific antigens to make targeted therapy achievable with fewer normal cells being impaired. The similarity between placentation and tumor development and growth has inspired many investigators to discover antigens for effective immunotherapy of cancers. Placenta-specific 1 (PLAC1) is one of the recently discovered placental antigens with limited normal tissue expression and fundamental roles in placental function and development. There is a growing body of evidence showing that PLAC1 is frequently activated in a wide variety of cancer types and promotes cancer progression. Based on the restricted expression of PLAC1 in testis, placenta and a wide variety of cancers, we have designated this molecule with new terminology, cancer-testis-placenta (CTP) antigen, a feature that PLAC1 shares with many other cancer testis antigens. Recent reports from our lab provide compelling evidence on the preferential expression of PLAC1 in prostate cancer and its potential utility in prostate cancer immunotherapy. PLAC1 may be regarded as a potential CTP antigen for targeted cancer immunotherapy based on the available data on its promoting function in cancer development and also its expression in cancers of different histological origin. In this review, we will summarize current data on PLAC1 with emphasis on its association with cancer development and immunotherapy.