Putative gene loci associated with carcinogenesis and metastasis of endocervical adenocarcinomas of uterus determined by conventional and array-based CGH

Progesterone receptor membrane component 2 is critical for human placental extravillous trophoblast invasion

Proper extravillous trophoblast invasion is essential for normal placentation and pregnancy. However, the molecular mechanisms by which cytotrophoblasts differentiate into extravillous trophoblast are unclear. We discovered that in the first-trimester placenta, progesterone receptor membrane component 2 was highly expressed in syncytiotrophoblast but significantly lower in extravillous trophoblast and cytotrophoblasts, indicating a divergent role for progesterone receptor membrane component 2 in trophoblast functions. We aim to examine the role of progesterone receptor membrane component 2 in extravillous trophoblasts invasion mediated by both intracellular and extracellular signals. Progesterone receptor membrane component 2 knockdown and overexpression cells were established in HTR8/SVneo cells, a first-trimester extravillous trophoblast-derived cell model, by transfection with small-interfering RNA or progesterone receptor membrane component 2 plasmids, respectively. Progesterone receptor membrane component 2 knockdown led to cellular morphological changes , enhanced trophoblast proliferation,invasion, and promoted tube formation. These effects were mediated by the activation of hypoxia-inducible factor 1alpha and an increased expression of vascular endothelial growth factor A. The culture supernatant collected from progesterone receptor membrane component 2 knockdown cells did not significantly affect extravillous trophoblast invasion compared to the controls, indicating that extracellular signaling did not robustly regulate extravillous trophoblast invasion in this study. In conclusion, attenuation of progesterone receptor membrane component 2 plays a role in placentation by promoting cell proliferation, invasion, and angiogenesis in extravillous trophoblasts via activation of hypoxia-inducible factor 1 alpha signaling. We thus identified a new function of progesterone receptor membrane component 2 and provide insights on understanding the mechanisms of trophoblast invasion.

The role of progesterone and the progesterone receptor in cancer: progress in the last 5 years

INTRODUCTION

Patients with various advanced cancers devoid of nuclear progesterone receptors (nPR) have demonstrated increased quality and length of life when treated with the PR modulator mifepristone, which likely works by interacting with membrane PRs (mPR).

AREAS COVERED

Two immunomodulatory proteins are discussed that seem to play a role in cancers that proliferate whether the malignant tumor is positive or negative for the nPR. These two proteins are the progesterone receptor membrane component-1 (PGRMC-1) and the progesterone-induced blocking factor (PIBF). Both PGRMC-1 and the parent form of PIBF foster increased tumor aggressiveness, whereas splice variants of the 90 kDa form of PIBF inhibit immune response against cancer cells.

EXPERT OPINION

The marked clinical improvement following 200-300 mg of mifepristone is likely related to blocking PIBF. In the low dosage used, mifepristone likely acts as an agonist for PGRMC-1 protein. Mifepristone may be less effective for cancers positive for the nPR because the nPR may be protective and blocking it may have detrimental effects. Based on this hypothetical model, the development of other potential treatment options to provide even greater efficacy for treating cancer are discussed.

Progesterone Receptor Membrane Component (PGRMC)1 and PGRMC2 and Their Roles in Ovarian and Endometrial Cancer

Cancers of the female reproductive tract are both lethal and highly prevalent. For example, the five-year survival rate of women diagnosed with ovarian cancer is still less than 50%, and endometrial cancer is the fourth most common cancer in women with > 65,000 new cases in the United States in 2020. Among the many genes already established as key participants in ovarian and endometrial oncogenesis, progesterone receptor membrane component (PGRMC)1 and PGRMC2 have gained recent attention given that there is now solid correlative information supporting a role for at least PGRMC1 in enhancing tumor growth and chemoresistance. The expression of PGRMC1 is significantly increased in both ovarian and endometrial cancers, similar to that reported in other cancer types. Xenograft studies using human ovarian and endometrial cancer cell lines in immunocompromised mice demonstrate that reduced expression of PGRMC1 results in tumors that grow substantially slower. While the molecular underpinnings of PGRMCs' mechanisms of action are not clearly established, it is known that PGRMCs regulate survival pathways that attenuate stress-induced cell death. The objective of this review is to provide an overview of what is known about the roles that PGRMC1 and PGRMC2 play in ovarian and endometrial cancers, particularly as related to the mechanisms through which they regulate mitosis, apoptosis, chemoresistance, and cell migration.

What Do We Know about Classical and Non-Classical Progesterone Receptors in the Human Female Reproductive Tract? A Review

The progesterone hormone regulates the human menstrual cycle, pregnancy, and parturition by its action via the different progesterone receptors and signaling pathways in the female reproductive tract. Progesterone actions can be exerted through classical and non-classical receptors, or even a combination of both. The former are nuclear receptors whose activation leads to transcriptional activity regulation and thus in turn leads to slower but long-lasting responses. The latter are composed of progesterone receptors membrane components (PGRMC) and membrane progestin receptors (mPRs). These receptors rapidly activate the appropriate intracellular signal transduction pathways, and they can subsequently initiate specific cell responses or even modulate genomic cell responses. This review covers our current knowledge on the mechanisms of action and the relevance of classical and non-classical progesterone receptors in female reproductive tissues ranging from the ovary and uterus to the cervix, and it exposes their crucial role in female infertility.

LRP1B: A Giant Lost in Cancer Translation

Low-density lipoprotein receptor-related protein 1B (LRP1B) is a giant member of the LDLR protein family, which includes several structurally homologous cell surface receptors with a wide range of biological functions from cargo transport to cell signaling. LRP1B is among the most altered genes in human cancer overall. Found frequently inactivated by several genetic and epigenetic mechanisms, it has mostly been regarded as a putative tumor suppressor. Still, limitations in LRP1B studies exist, in particular associated with its huge size. Therefore, LRP1B expression and function in cancer remains to be fully unveiled. This review addresses the current understanding of LRP1B and the studies that shed a light on the LRP1B structure and ligands. It goes further in presenting increasing knowledge brought by technical and methodological advances that allow to better manipulate LRP1B expression in cells and to more thoroughly explore its expression and mutation status. New evidence is pushing towards the increased relevance of LRP1B in cancer as a potential target or translational prognosis and response to therapy biomarker.

LRP1B mutations are associated with favorable outcomes to immune checkpoint inhibitors across multiple cancer types

BACKGROUND

Low-density lipoprotein receptor-related protein 1b (encoded by LRP1B) is a putative tumor suppressor, and preliminary evidence suggests LRP1B-mutated cancers may have improved outcomes with immune checkpoint inhibitors (ICI).

METHODS

We conducted a multicenter, retrospective pan-cancer analysis of patients with LRP1B alterations treated with ICI at Duke University, Johns Hopkins University (JHU) and University of Michigan (UM). The primary objective was to assess the association between overall response rate (ORR) to ICI and pathogenic or likely pathogenic (P/LP) LRP1B alterations compared with LRP1B variants of unknown significance (VUS). Secondary outcomes were the associations with progression-free survival (PFS) and overall survival (OS) by LRP1B status.

RESULTS

We identified 101 patients (44 Duke, 35 JHU, 22 UM) with LRP1B alterations who were treated with ICI. The most common tumor types by alteration (P/LP vs VUS%) were lung (36% vs 49%), prostate (9% vs 7%), sarcoma (5% vs 7%), melanoma (9% vs 0%) and breast cancer (3% vs 7%). The ORR for patients with LRP1B P/LP versus VUS alterations was 54% and 13%, respectively (OR 7.5, 95% CI 2.9 to 22.3, p=0.0009). P/LP LRP1B alterations were associated with longer PFS (HR 0.42, 95% CI 0.26 to 0.68, p=0.0003) and OS (HR 0.62, 95% CI 0.39 to 1.01, p=0.053). These results remained consistent when excluding patients harboring microsatellite instability (MSI) and controlling for tumor mutational burden (TMB).

CONCLUSIONS

This multicenter study shows significantly better outcomes with ICI therapy in patients harboring P/LP versus VUS LRP1B alterations, independently of TMB/MSI status. Further mechanistic and prospective validation studies are warranted.

Downregulation of CYB5D2 is associated with breast cancer progression

We report here that CYB5D2 is associated with tumor suppression function in breast cancer (BC). CYB5D2 expression was significantly reduced in tamoxifen resistant MCF7 cells and in MCF7 cell-derived xenografts treated with TAM. CYB5D2 overexpression induced apoptosis in MCF7 cells; CYB5D2 knockdown enhanced MCF7 cell proliferation. Using the TCGA and Curtis datasets within the Oncomine database, CYB5D2 mRNA expression was downregulated in primary BCs vs breast tissues and HER2-positive or triple negative BCs vs estrogen receptor (ER)-positive BCs. Using the TCGA and Metabric datasets (n = 817 and n = 2509) within cBioPortal, 660 and 4891 differentially expressed genes (DEGs) in relation to CYB5D2 were identified. These DEGs were enriched in pathways governing cell cycle progression, progesterone-derived oocyte maturation, oocyte-meiosis, estrogen-mediated S-phase entry, and DNA metabolism. CYB5D2 downregulation decreased overall survival (OS, p = 0.0408). A CYB5D2-derived 21-gene signature was constructed and robustly correlated with OS shortening (p = 5.72e-12), and independently predicted BC deaths (HR = 1.28; 95% CI 1.08–1.52; p = 0.004) once adjusting for known clinical factors. CYB5D2 reductions displayed relationship with mutations in PIK3CA, GATA3, MAP3K1, CDH1, TP53 and RB1. Impressively, 85% (560/659) of TP53 mutations occurred in the 21-gene signature-positive BC. Collectively, we provide the first evidence that CYB5D2 is a candidate tumor suppressor of BC.

Progesterone receptor membrane component 1 as a potential prognostic biomarker for hepatocellular carcinoma

AIM

To investigate the clinicopathological significance of progesterone receptor membrane component 1 (PGRMC1) and PGRMC2 in hepatocellular carcinoma (HCC).

METHODS

We performed immunohistochemical staining to evaluate the estrogen receptor (ER), progesterone receptor (PR), PGRMC1, and PGRMC2 in a clinical cohort consisting of 89 paired HCC and non-tumor liver samples. We also analyzed HCC data (n = 373) from The Cancer Genome Atlas (TCGA). We correlated the expression status of PGRMC1 and PGRMC2 with clinicopathological indicators and the clinical outcomes of the HCC patients. We knocked down or overexpressed PGRMC1 in HCC cell lines to evaluate its biological significance in HCC cell proliferation, differentiation, migration, and invasion.

RESULTS

We found that few HCC cases expressed ER (5.6%) and PR (4.5%). In contrast, most HCC cases expressed PGRMC1 (89.9%) and PGRMC2 (100%). PGRMC1 and PGRMC2 exhibited significantly lower expression in tumor tissue than in non-tumor tissue (P < 0.001). Lower PGRMC1 expression in HCC was significantly associated with higher serum alpha-fetoprotein expression (P = 0.004), poorer tumor differentiation (P = 0.045) and liver capsule penetration (P = 0.038). Low PGRMC1 expression was an independent predictor for worse disease-free survival (P = 0.002, HR = 2.384, CI: 1.377-4.128) in our cases, as well as in the TCGA cohort (P < 0.001, HR = 2.857, CI: 1.781-4.584). The expression of PGRMC2 did not relate to patient outcome. PGRMC1 knockdown promoted a poorly differentiated phenotype and proliferation of HCC cells in vitro, while PGRMC1 overexpression caused the opposite effects.

CONCLUSION

PGRMC1 is a non-classical hormonal receptor that negatively regulates hepatocarcinogenesis. PGRMC1 down-regulation is associated with progression of HCC and is a poor prognostic indicator.

Expression of a recombinant full-length LRP1B receptor in human non-small cell lung cancer cells confirms the postulated growth-suppressing function of this large LDL receptor family member

Low-density lipoprotein (LDL) receptor-related protein 1B (LRP1B), a member of the LDL receptor family, is frequently inactivated in multiple malignancies including lung cancer. LRP1B is therefore considered as a putative tumor suppressor. Due to its large size (4599 amino acids), until now only minireceptors or receptor fragments have been successfully cloned. To assess the effect of LRP1B on the proliferation of non-small cell lung cancer cells, we constructed and expressed a transfection vector containing the 13.800 bp full-length murine Lrp1b cDNA using a PCR-based cloning strategy. Expression of LRP1B was analyzed by quantitative RT-PCR (qRT-PCR) using primers specific for human LRP1B or mouse Lrp1b. Effective expression of the full length receptor was demonstrated by the appearance of a single 600 kDa band on Western Blots of HEK 293 cells. Overexpression of Lrp1b in non-small cell lung cancer cells with low or absent endogenous LRP1B expression significantly reduced cellular proliferation compared to empty vector-transfected control cells. Conversely, in Calu-1 cells, which express higher endogenous levels of the receptor, siRNA-mediated LRP1B knockdown significantly enhanced cellular proliferation. Taken together, these findings demonstrate that, consistent with the postulated tumor suppressor function, overexpression of full-length Lrp1b leads to impaired cellular proliferation, while LRP1B knockdown has the opposite effect. The recombinant Lrp1b construct represents a valuable tool to unravel the largely unknown physiological role of LRP1B and its potential functions in cancer pathogenesis.

Gynecologic Cancer InterGroup (GCIG) consensus review for small cell carcinoma of the cervix

Small cell carcinoma of the cervix (SCCC) is a rare histological entity of uterine cervical cancer. Compared with other common histological types, squamous cell carcinoma or adenocarcinoma, the outcome of SCCC is poor because of the high incidence of nodal or distant metastasis even with early stage. In this review, current consensus of epidemiology, pathology, and initial treatment for SCCC will be discussed.

Let-7a functions as a tumor suppressor in Ewing's sarcoma cell lines partly by targeting cyclin-dependent kinase 6

MicroRNAs play an important role in the development and progression of Ewing's sarcoma (ES). Especially, the expression of let-7a has been reported to be significantly downregulated in various cancers, and can affect the initiation and maintenance of tumor progression. However, the relative effects of let-7a on ES cells and relative mechanisms are largely unknown. In this study, we identified the underexpression of let-7a in human ES cells comparing with the human mesenchymal stem cells. Then, we sought to compensate for its loss through exogenous transfection with let-7a mimic into ES cell lines A673 and SK-ES-1. Restored let-7a expression inhibited cell proliferation, migration, as well as invasion; arrested cell cycle progression; and induced cell apoptosis of both cell lines. Moreover, bioinformatic prediction suggested that cyclin-dependent kinase 6 (CDK6), which is overexpressed and functions as an oncoprotein in ES cells, is a putative target gene of let-7a. Using mRNA and protein expression analysis and luciferase assays, we further identified the target role of CDK6. Finally, we found that restored CDK6 expression in ES cells that had been treated with let-7a mimic before could partly dampen let-7a-mediated tumor suppression. Taken together, our results showed that let-7a acted as a tumor suppressor in ES by targeting CDK6, and it may provide novel diagnostic and therapeutic options for human Ewing sarcoma clinical operation in future.

PGRMC2, a yet uncharacterized protein with potential as tumor suppressor, migration inhibitor, and regulator of cytochrome P450 enzyme activity

PGRMC2 (progesterone receptor membrane component 2) is highly homologous if compared with PGRMC1, a cytochrome-related protein, which is induced in several cancers and linked to cell growth in these cancers. Further it seems to be involved in progesterone signalling and cytochrome P450 binding. For PGRMC2 only sparse information is available. Recent data show that PGRMC1 and 2 share several similar characteristics, but there are also important differences in expression and function of the both proteins. Several findings point to the fact that PGRMC2 might play a role in cancer as well. The protein influences the migration rate of ovarian cancer cells and a loss of PGRMC2 might result in higher metastasis rates. In contrast to PGRMC1 it seems more likely to act as a tumor suppressor than a promoter. Altered PGRMC2 expression was further detected in the context of term and preterm labour, though the implications of this finding are currently unknown and need further examination. PGRMC2 further might play a role in gynaecologic diseases like preterm labour and endometriosis. PGRMC2 shares the cellular localisation and the ability to bind cytochrome enzymes with PGRMC1. Further the protein was shown to influence the activity of CYP3A4. In conclusion, though not much is known about PGRMC2 so far, it deserves further examination as data point to a role of PGRMC2 as tumor suppressor, migration inhibitor and regulator of cytochrome P450 proteins.

Human height genes and cancer

Body development requires the ability to control cell proliferation and metabolism, together with selective 'invasive' cell migration for organogenesis. These requirements are shared with cancer. Human height-associated loci have been recently identified by genome-wide SNP-association studies. Strikingly, most of the more than 100 genes found associated to height appear linked to neoplastic growth, and impose a higher risk for cancer. Height-associated genes drive the HH/PTCH and BMP/TGFβ pathways, with p53, c-Myc, ERα, HNF4A and SMADs as central network nodes. Genetic analysis of body-size-affecting diseases and evidence from genetically-modified animals support this model. The finding that cancer is deeply linked to normal, body-plan master genes may profoundly affect current paradigms on tumor development.

In vitro inhibition of SKOV-3 cell migration as a distinctive feature of progesterone receptor membrane component type 2 versus type 1

Progesterone receptor membrane component type 2 (PGRMC2) is strongly homologous to PGRMC1 which is highly expressed in ovarian cancer and other cancer cells and was claimed to play an important role in chemotherapy resistance. Whereas PGRMC1 has been extensively characterized in in vitro studies, comparably little is known about PGRMC2. To determine PGRMC2's role in ovarian cancer cell proliferation and mobility PGRMC1- and 2-depleted and -overexpressing SKOV-3 cells were generated. In electric cell-substrate impedance sensing studies, PGRMC2 negatively affects SKOV-3 migration rate if overexpressed; oppositely, depletion was associated with an increased migration rate. PGRMC1 had no effect in this assay. These effects were not associated with f-actin regulation or actin cytoskeleton reorganization. Yet, these highly homologous proteins share many properties. Both PGRMC1 and 2 are localized to the endoplasmic reticulum. As PGRMC1 was reported to interact with cytochrome P450 proteins (CYP) binding of two different CYPs to PGRMC2 was tested; a stable interaction of PGRMC2 with CYP3A4 and CYP21A2 was found in human embryonic kidney cells. For both PGRMC types, cell viability assays revealed no significant differences of SKOV-3 survival in overexpressing and depleted cells. PGRMC2 also does not seem to have any influence on the apoptotic effect of cisplatin or the antiapoptotic effect of progesterone which had been reported for PGRMC1. In contrast to PGRMC1, protein levels of PGRMC2 in SKOV-3 cells are reduced by treatment with cisplatin (30-60μM). In conclusion, we show for the first time that PGRMC2 inhibits migration of SKOV-3 ovarian cancer cells in vitro.

Colorectal cancer migration and invasion initiated by microRNA-106a

MicroRNAs have been implicated in the regulation of several cellular signaling pathways of colorectal cancer (CRC) cells. Although emerging evidence proves that microRNA (miR)-106a is expressed highly in primary tumor and stool samples of CRC patients; whether or not miR-106a mediates cancer metastasis is unknown. We show here that miR-106a is highly expressed in metastatic CRC cells, and regulates cancer cell migration and invasion positively in vitro and in vivo. These phenotypes do not involve confounding influences on cancer cell proliferation. MiR-106a inhibits the expression of transforming growth factor-β receptor 2 (TGFBR2), leading to increased CRC cell migration and invasion. Importantly, miR-106a expression levels in primary CRCs are correlated with clinical cancer progression. These observations indicate that miR-106a inhibits the anti-metastatic target directly and results in CRC cell migration and invasion.

Transcriptional analysis of novel hormone receptors PGRMC1 and PGRMC2 as potential biomarkers of breast adenocarcinoma staging

BACKGROUND

The expression of progesterone receptor membrane component 1 (PGRMC1) in breast cancer has generated interest in this recently discovered protein because of its role in tumorigenesis. However, correlations between patient age, PGRMC1 gene expression, breast cancer morphology, and breast cancer stage have not been adequately studied. Furthermore, very little is known about possible roles for other PGRMC isoforms in breast cancer, like PGRMC2. Thus, we examined the expression of PGRMC1 and PGRMC2 mRNA by relative quantitative PCR (RelqPCR) and determined whether transcript levels correlate with age, breast cancer staging, estrogen receptor alpha (ERα) status, and other morphometric features routinely used during the pathological examination of breast ductal adenocarcinomas.

METHODS

Twenty-eight frozen or paraffin embedded breast cancer samples (ductal carcinoma in situ and stages I thru IV invasive ductal adenocarcinoma) and 10 control benign breast tissue samples were randomly selected and interrogated by RelqPCR to determine PGRMC1, 2, and ERα mRNA transcript levels. To control for slight variations in sample preparation, receptor transcript was normalized to the housekeeping gene phosphoglycerate kinase 1 (PGK1). Descriptive statistics and ANOVA of multiparametric datasets were used to correlate transcript levels with pathological staging parameters.

RESULTS

PGRMC1 mRNA levels decreased significantly with patient age (Pearson's correlation -0.369; P=0.035), whereas PGRMC2 levels did not. Although the mean relative expression of PGRMC1 significantly decreased in stage II breast cancer compared with controls (P=0.050), it was no longer significant when age was considered a covariance (P=0.371). On the other hand, PGRMC2 mRNA transcript was significantly decreased in stage II breast cancer when compared to stage III cancer (P=0.028) in a manner independent of age (corrected model Bonferroni pair wise comparison, P=0.036). Furthermore, PGRMC2 levels positively correlated with ERα mRNA transcripts in patients with ER positive tumors (Pearson's correlation 0.503, P=0.096).

CONCLUSIONS

Decreases in PGRMC1 mRNA are partially explained by increasing patient age. On the other hand, compared to stage III, PCRMC2 mRNA was significantly decreased in stage II adenocarcinoma of the breast in an age-independent manner. Additionally, PGRMC2 mRNA levels displayed a positive correlation with ERα transcripts. Thus, in addition to morphometric pathologic staging criteria, measurements of PGRMC2 mRNA may be useful for distinguishing low stage tumors from higher stages that require more aggressive clinical management, and may be a useful test when tumor ER IHC results are equivocal.

Molecular markers of preterm labor in the choriodecidua

Because relevant biochemical changes are known to begin at the choriodecidual interface some weeks before actual clinical onset of labor, we hypothesized that the preterm choriodecidua may display gene and protein expression patterns specific to preterm labor. Transcriptomic (microarray) and proteomic (2-dimensional gel electrophoresis [2DGE]) profiling methodologies were used to compare changes in choriodecidual tissue collected from women who delivered before 35 weeks of gestation following spontaneous preterm labor (n = 12) and gestation-matched nonlaboring controls (n = 7). Additionally, 2DGE was used to compare differences in protein expression during term and preterm labor and to construct a choriodecidual proteome map. Overall, expressed transcripts and proteins indicated active tissue remodeling independent of labor status and an association with inflammatory processes during labor. Spontaneous, infection-induced and abruption-associated preterm deliveries were each defined by distinct transcriptional profiles. Proteins osteoglycin and progesterone receptor component 2 (PGRMC2) were upregulated during term and preterm labor while galectin 1, annexin 3, annexin 5, and protein disulfide isomerase (PDI) were upregulated only during preterm labor, suggesting a probable association with the underlying pathology. Together, these results represent novel data that warrant further investigations to elucidate plausible causal relationships of these molecules with spontaneous preterm delivery.

Physiological and pathological implications of laminins: From the gene to the protein

The extracellular matrix plays an important role in modulating the behavior of cells with which it interacts. There are a number of families of extracellular matrix (ECM) proteins including collagens, proteoglycans and laminins (LM). LM are the major component of the basal lamina (BL). Here, we review the current knowledge on their structure, self-assembly, binding mechanisms, diverse tissue-expression patterns and its impact on pathology. Studies and hypothesis exploring the role of LM and their polymorphic genes on autoimmune diseases (AIDs) such as systemic lupus erythematosus and Sjögren's syndrome (SS) are also discussed.

Is lobular endocervical glandular hyperplasia a cancerous precursor of minimal deviation adenocarcinoma?: a comparative molecular-genetic and immunohistochemical study

Although lobular endocervical glandular hyperplasia (LEGH) was originally described as a distinct hyperplastic glandular lesion of the uterine cervix, recent studies have raised a question that LEGH may be a cancerous precursor of minimal deviation adenocarcinoma (MDA) and other mucinous adenocarcinomas (MACs) of the uterine cervix. In the present study, we studied LEGH, MDA, and MAC by using molecular-genetic and immunohistochemical methods for chromosomal imbalance, microsatellite instability, human papillomavirus (HPV) infection, and gastric pyloric-type mucin secretion to clarify their relationship. Comparative genomic hybridization revealed recurrent chromosomal imbalances, that is, gains of chromosome 3q and a loss of 1p, which were common to MDA and MAC, in 3 of 14 LEGHs analyzed (21%). LEGHs with chromosomal imbalances showed a degree of cellular atypia in the hyperplastic glandular epithelium. Dual-color fluorescence in situ hybridization confirmed a gain of chromosome 3 fragment in these cervical glandular lesions. HPV in situ hybridization revealed that high-risk HPV (types 16 and 18) was positive in over 80% of MACs, but negative in all LEGHs and MDAs examined. Microsatellite instability was rarely detected in these cervical glandular lesions. Our present study results demonstrated a molecular-genetic link between LEGH and cervical mucinous glandular malignancies including MDA and MAC, and are thought to support the hypothesis that a proportion of LEGHs are cancerous precursors of MDA and/or MAC.

Non-genomic progesterone actions in female reproduction

BACKGROUND

The steroid hormone progesterone is indispensable for mammalian procreation by controlling key female reproductive events that range from ovulation to implantation, maintenance of pregnancy and breast development. In addition to activating the progesterone receptors (PRs)-B and -A, members of the superfamily of ligand-dependent transcription factors, progesterone also elicits a variety of rapid signalling events independently of transcriptional or genomic regulation. This review covers our current knowledge on the mechanisms and relevance of non-genomic progesterone signalling in female reproduction.

METHODS

PubMed was searched up to August 2008 for papers on progesterone actions in ovary/breast/endometrium/myometrium/brain, focusing primarily on non-genomic signalling mechanisms.

RESULTS

Convergence and intertwining of rapid non-genomic events and the slower transcriptional actions critically determine the functional response to progesterone in the female reproductive system in a cell-type- and environment-specific manner. Several putative progesterone-binding moieties have been implicated in rapid signalling events, including the 'classical' PR and its variants, progesterone receptor membrane component 1, and the novel family of membrane progestin receptors. Progesterone and its metabolites have also been implicated in the allosteric regulation of several unrelated receptors, such as gamma-aminobutyric acid type A, oxytocin and sigma(1) receptors.

CONCLUSIONS

Identification of the mechanisms and receptors that relay rapid progesterone signalling is an area of research fraught with difficulties and controversy. More in-depth characterization of the putative receptors is required before the non-genomic progesterone pathway in normal and pathological reproductive function can be targeted for pharmacological intervention.

Recurrent gene amplifications in human type I endometrial adenocarcinoma detected by fluorescence in situ hybridization

Determining what genes are actively involved in tumor development is important, because they may provide targets for directed therapy. Human tumors are greatly heterogeneous with respect to etiology and genetic background, which complicates the identification of common genetic aberrations. In contrast, genetic and environmental variation can be in part controlled in experimental animals, which facilitates identification of the important changes. In inbred BDII rats, which are genetically predisposed to endometrial adenocarcinomas (EAC), certain chromosome regions exhibit recurrent amplification in the tumors. Previous CGH analysis had shown that a subset of human EAC tumors exhibited increased copy numbers in the homologous chromosomal regions, located in human 2p21 approximately p25 and 7q21 approximately q31. Using fluorescence in situ hybridization analysis on imprints from 13 human EAC tumors, we determined the average copy numbers of each of 15 probes derived from cancer-related genes situated in these chromosome regions. Among the genes analyzed, those most often targeted by amplification were SDC1 and CYP1B1 in 2p21 approximately p25 and CDK6 and MET in 7q21 approximately q31, but all of the 15 genes tested were found to be amplified in at least two tumors.

Slow endocytosis of the LDL receptor-related protein 1B: implications for a novel cytoplasmic tail conformation

The LDL receptor-related protein 1B (LRP1B) is a putative tumor suppressor homologous to LRP1. Both LRP1 and LRP1B contain cytoplasmic tails with several potential endocytosis motifs. Although the positions of these endocytic motifs are similar in both receptors, LRP1B is internalized at a 15-fold slower rate than LRP1. To determine whether the slow endocytosis of LRP1B is due to the utilization of an endocytosis motif other than the YATL motif used by LRP1, we tested minireceptors with mutations in each of the five potential motifs in the LRP1B tail. Only mutation of both NPXY motifs together abolished LRP1B endocytosis, suggesting that LRP1B can use either of these motifs for internalization. LRP1B contains a unique insertion of 33 amino acids not present in LRP1 that could lead to altered recognition of trafficking motifs. Surprisingly, deletion of this insertion had no effect on the endocytosis rate of LRP1B. However, replacing either half of the LRP1B tail with the corresponding LRP1 sequence markedly accelerated LRP1B endocytosis. From these data, we propose that both halves of the LRP1B cytoplasmic tail contribute to a unique global conformation, which results in less efficient recognition by endocytic adaptors and a slow endocytosis rate.

Progesterone receptor membrane component 1: an integrative review

Progesterone receptor membrane component 1 (PGRMC1) contains a cytochrome b5 domain fold and belongs to the so-called membrane-associated progesterone receptor (MAPR) protein family that is widespread in eukaryotes. PGRMC1 and the related PGRMC2 mammalian family member diverged sometime after the evolution of segmented metazoan body plan and the appearance of vertebrates. Therefore PGRMC1 might be expected to be involved in some ancient eukaryotic processes, as well as more modern functions related to multicellularity and tissue interactions. Perhaps this explains the perplexing diversity of contexts where PGRMC1 has been observed, apparently being involved in different cellular processes at various sub-cellular locations. This review attempts to collate and interpret these observations. Ironically, despite being the archetypal member of the MAPR family, it has yet to be demonstrated that PGRMC1 exhibits specific progesterone binding. Potential roles of heme and steroid/sterol ligands are reviewed, as well as the implications of apparent target sequences within PGRMC1 for binding by SH2- and SH3-domain proteins as well as kinases. These motifs are modelled using the cytochrome b5 domain NMR structure of the Arabidopsis protein 1J03, implicating a possible function for PGRMC1 as an adaptor protein involved in regulating protein interactions and intracellular signal transduction and/or membrane trafficking. This interpretation is supported by the apparent presence of immunoreceptor tyrosine-based activation motif/ITAM sequences that are involved in endocytosis and vesicle targeting, and the colocalisation of PGRMC1 with caveolin and at the cytoplasmic membrane. Evidence for roles in disease, especially cancer, is also discussed.

gamma-Secretase-mediated release of the low density lipoprotein receptor-related protein 1B intracellular domain suppresses anchorage-independent growth of neuroglioma cells

The low density lipoprotein receptor related protein 1B (LRP1B) is a large endocytic receptor that was first identified as a candidate tumor suppressor gene. In the current investigation we demonstrate that LRP1B undergoes regulated intramembrane proteolysis in a gamma-secretase-dependent process. The released intracellular domain (ICD) then translocates to the nucleus via a nuclear localization signal that is present within this domain. ICD release first requires shedding of the LRP1B ectodomain, which appears to be catalyzed by a member of the metalloproteinase family. Employing site-directed mutagenesis studies, we identified lysine residues 4432 and 4435 and arginine 4442 as key amino acids important for ectodomain shedding of LRP1B. We also demonstrate that an LRP1B minireceptor as well as the ICD domain alone suppresses anchorage-independent growth of LRP1B-deficient neuroglioma cells (H4 cells). Interestingly, abrogating ectodomain shedding resulted in a loss of the ability of LRP1B minireceptors to suppress anchorage-independent growth. Together, these studies reveal that LRP1B has tumor suppression function that is mediated by proteolytic processing of the receptor resulting in ICD release.

Regulation of the G1/S phase of the cell cycle and alterations in the RB pathway in human lung cancer

The retinoblastoma (RB)-Cyclin (CCN)D1-p16 cell cycle pathway has a crucial role in lung tumorigenesis. Impairment of the RB pathway has been shown to occur in almost all lung tumors. A deregulation at any level of this core RB pathway seems to make cells insensitive to the mitogenic signaling that is required for cell cycle progression. To date, almost all participants in this pathway have been shown to be altered to a various degree in lung tumors. Some of the alterations are mutually exclusive, including RB and p16INK4A . In small cell lung cancer, the RB tumor suppressor gene is inactivated in almost 90% of the tumors, whereas in non-small cell lung cancer, the cyclin-dependent kinase (CDK)4 inhibitor p16INK4A is inactivated in 40-60% of the tumors. Many mechanisms may be responsible for activating the RB-Cyclin D1 pathway, including activating (CDK4) and inactivating mutations (p16INK4A ), deletions (RB and p16INK4A ), amplifications (CCND1 and CDK4), silencing methylation (p16INK4A and RB), and hyper-phosphorylation (RB). As some of these alterations, such as p16INK4A methylation, can also be detected in bronchial lavage and serum, they could potentially serve as useful markers for the early detection of lung cancer. This review summarizes recent experiments describing the variable roles of key-player molecules of the RB pathway and different mechanisms by which the RB pathway can be altered in lung cancer.

Striking differences of LDL receptor-related protein 1B expression in mouse and human

The low density lipoprotein (LDL) receptor-related protein 1B (LRP1B) is a member of the expanding LDL receptor family, and is closely related to LRP. It was discovered as a putative tumor suppressor, and is frequently inactivated in human malignant tissues. However, the expression pattern of LRP1B in normal human tissues was unclear. In the present study, we analyzed LRP1B expression in normal mouse and human tissues. By using RT-PCR, we found that, while mouse LRP1B expression is mostly restricted to the brain, human LRP1B expression is more widespread with highest expression levels detected in the brain, adrenal gland, salivary gland, and testis. Although mouse LRP1B expresses in the forms of both full-length receptor tail and an alternatively spliced form lacking a 33-amino acid insert, human LRP1B is expressed exclusively in the form of full-length receptor tail. Finally, we found that, unlike mouse LRP1B, human LRP1B is cleaved by furin. Taken together, these data demonstrate that there are striking differences between LRP1B expression in mouse and human tissues. The broader expression pattern of LRP1B in human tissues suggests that this putative tumor suppressor may play roles in several types of human cancer.