Cyclooxygenase-1 inhibition prolongs postnatal ovarian follicle lifespan in mice

Menopause is the permanent cessation of menstruation that results from depletion of ovarian germ cells and follicles. Although most animals experience reproductive senescence, the mechanisms differ from that in women, who may live more than one-third of their lives after menopause and consequently face the risk of a number of menopause-associated health problems. Understanding factors that influence ovarian aging may provide strategies to delay or alleviate physiological alterations that take place in postmenopausal women. The germ cell-deficient Wv mice recapitulate follicle loss, prolong postreproductive lifespan, and model many physiological changes that take place in postmenopausal women. Here, using genetic and pharmacological approaches, we found that inhibition of cyclooxygenase-1 but not cyclooxygenase-2 in Wv mice delays germ cell depletion and preserves ovarian follicles. Cyclooxygenase-1 inhibition slows down follicle maturation at the conversion of primary to secondary follicles and prolongs postnatal ovarian follicle lifespan. The current study suggests that inhibition of cyclooxygenase-1 may be able to delay ovarian aging and modulate menopausal timing.

Differential requirement for Dab2 in the development of embryonic and extra-embryonic tissues

BACKGROUND

Disabled-2 (Dab2) is an endocytic adaptor protein involved in clathrin-mediated endocytosis and cargo trafficking. Since its expression is lost in several cancer types, Dab2 has been suggested to be a tumor suppressor. In vitro studies indicate that Dab2 establishes epithelial cell polarity and organization by directing endocytic trafficking of membrane glycoproteins. Dab2 also modulates cellular signaling pathways by mediating the endocytosis and recycling of surface receptors and associated signaling components. Previously, two independent gene knockout studies have been reported, with some discrepancies in the observed embryonic phenotypes. To further clarify the in vivo roles of Dab2 in development and physiology, we designed a new floxed allele to delete dab2 gene.

RESULTS

The constitutive dab2 deleted embryos showed a spectrum in the degree of endoderm disorganization in E5.5 and no mutant embryos persisted at E9.5. However, the mice were grossly normal when dab2 deletion was restricted to the embryo proper and the gene was retained in extraembryonic tissues using Meox2-Cre and Sox2-Cre. Adult Dab2-deficient mice had a small but statistically significant increase in serum cholesterol levels.

CONCLUSION

The study of the new dab2 mutant allele in embryos and embryoid bodies confirms a role for Dab2 in extraembryonic endoderm development and epithelial organization. Experimental results with embryoid bodies suggest that additional endocytic adaptors such as Arh and Numb could partially compensate for Dab2 loss. Conditional deletion indicates that Dab2 is dispensable for organ development, when the vast majority of the embryonic cells are dab2 null. However, Dab2 has a physiological role in the endocytosis of lipoproteins and cholesterol metabolism.

Abstract PD08-02: Disparities in the Utilization of Reconstruction after Mastectomy: The California Teachers Study

Background: For breast cancer patients undergoing mastectomy, factors such as insurance status, race/ethnicity, age, and type of hospital influence whether post-mastectomy reconstruction (PMR) is performed. This study was undertaken to determine if additional patient variables and clinicopathologic features also influence the utilization of PMR using the California Teachers Study (CTS).

Methods: Patients were identified from the CTS, a cohort of approximately 133,000 female public school teachers and administrators, followed prospectively from 1995 forward to investigate exposures associated with incident cancer and other outcomes. All in situ and invasive breast cancers were identified through linkage with the California Cancer Registry, as well as with the California Office of Statewide Health Planning and Development (OSHPD) hospital discharge database to determine the rates of mastectomy with and without reconstruction. Patterns in PMR rates were examined by calendar year, age, race/ethnicity, type of insurance, type of hospital, tumor stage, body mass index (BMI), family history of breast cancer (FH), smoking history, physical activity, and prior breast implant status using a chi-square test. Univariable and multivariable-adjusted odds ratios (OR) with 95% confidence intervals (CI) were estimated for relative odds of immediate reconstruction vs. mastectomy only.

Results: During follow-up, 1,253 CTS participants with incident breast cancer underwent mastectomy with (N = 368) and without (N = 885) reconstruction. In multivariable stepwise logistic regression analyses, calendar year, age, type of insurance, tumor stage, and prior breast implant were statistically significantly associated with use of reconstruction. The proportion of patients undergoing immediate PMR increased from 21.8% during 1995–1999 to 26.4% during 2005–2009. A statistically significant dose-response was apparent between older age at surgery and decreased likelihood of post-mastectomy reconstruction (Ptrend<0.001). Race/ethnicity was not significantly associated with the use of PMR because the majority of patients were non-Hispanic white (89.5%). Most participants either had private insurance (56.8%) or Medicare (42.4%); those with private insurance were twice as likely to undergo PMR compared to patients with Medicare (OR 2.23: 95%CI 1.25–4.00, p = 0.01). Compared to participants with in situ and stage I breast cancer combined, participants with stage II or stage III breast cancer had one-third to one-half lower odds of postmastectomy reconstruction relative to mastectomy only (ORstageII = 0.67, 95% CI = 0.49–0.90, p = 0.01; ORstageIII=0.47, 95% CI=0.29–0.77, p = 0.002). Participants with a prior history of a breast implant were 7 times more likely to undergo PMR than participants with no such history (OR 7.14: 95%CI 2.38–21.41, p < 0.001).

Conclusions: In the CTS population, having a prior breast implant and lower tumor stage were additional variables associated with increased odds of PMR. This study validates previous studies which have shown that private insurance and younger age are associated with the use of reconstruction after mastectomy. Patient and health care provider education is warranted to ensure that all patients undergoing mastectomy are offered and have access to PMR.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr PD08-02.

Loss of A-type lamin expression compromises nuclear envelope integrity in breast cancer

Through advances in technology, the genetic basis of cancer has been investigated at the genomic level, and many fundamental questions have begun to be addressed. Among several key unresolved questions in cancer biology, the molecular basis for the link between nuclear deformation and malignancy has not been determined. Another hallmark of human cancer is aneuploidy; however, the causes and consequences of aneuploidy are unanswered and are hotly contested topics. We found that nuclear lamina proteins lamin A/C are absent in a significant fraction (38%) of human breast cancer tissues. Even in lamin A/C–positive breast cancer, lamin A/C expression is heterogeneous or aberrant (such as non-nuclear distribution) in the population of tumor cells, as determined by immunohistology and immunofluorescence microscopy. In most breast cancer cell lines, a significant fraction of the lamin A/C– negative population was observed. To determine the consequences of the loss of lamin A/C, we suppressed their expression by shRNA in non-cancerous primary breast epithelial cells. Down-regulation of lamin A/C in breast epithelial cells led to morphological deformation, resembling that of cancer cells, as observed by immunofluorescence microscopy. The lamin A/C–suppressed breast epithelial cells developed aneuploidy as determined by both flow Cytometry and fluorescence in situ hybridization. We conclude that the loss of nuclear envelope structural proteins lamin A/C in breast cancer underlies the two hallmarks of cancer aberrations in nuclear morphology and aneuploidy.

Src Inhibition with saracatinib reverses fulvestrant resistance in ER-positive ovarian cancer models in vitro and in vivo

PURPOSE

More effective, less toxic treatments for recurrent ovarian cancer are needed. Although more than 60% of ovarian cancers express the estrogen receptor (ER), ER-targeted drugs have been disappointing due to drug resistance. In other estrogen-sensitive cancers, estrogen activates Src to phosphorylate p27 promoting its degradation and increasing cell-cycle progression. Because Src is activated in most ovarian cancers, we investigated whether combined Src and ER blockade by saracatinib and fulvestrant would circumvent antiestrogen resistance.

EXPERIMENTAL DESIGN

ER and Src were assayed in 338 primary ovarian cancers. Dual ER and Src blockade effects on cell cycle, ER target gene expression, and survival were assayed in ERα+ ovarian cancer lines, a primary human ovarian cancer culture in vitro, and on xenograft growth.

RESULTS

Most primary ovarian cancers express ER. Src activity was greater in ovarian cancer lines than normal epithelial lines. Estrogen activated Src, ER-Src binding, and ER translocation from cytoplasm to nucleus. Estrogen-mediated mitogenesis was via ERα, not ERβ. While each alone had little effect, combined saracatinib and fulvestrant increased p27 and inhibited cyclin E-Cdk2 and cell-cycle progression. Saracatinib also impaired induction of ER-target genes c-Myc and FOSL1; this was greatest with dual therapy. Combined therapy induced autophagy and more effectively inhibited ovarian cancer xenograft growth than monotherapy.

CONCLUSIONS

Saracatinib augments effects of fulvestrant by opposing estrogen-mediated Src activation and target gene expression, increasing cell-cycle arrest, and impairing survival, all of which would oppose antiestrogen resistance in these ER+ ovarian cancer models. These data support further preclinical and clinical evaluation of combined fulvestrant and saracatinib in ovarian cancer.

White spotting variant mouse as an experimental model for ovarian aging and menopausal biology

OBJECTIVE

Menopause is a unique phenomenon in modern women, as most mammalian species possess a reproductive period comparable with their life span. Menopause is caused by the depletion of germ cell-containing ovarian follicles and in laboratory studies is usually modeled in animals in which the ovarian function is removed through ovariectomy or chemical poisoning of the germ cells. Our objective was to explore and characterize the white spotting variant (Wv) mice that have reduced ovarian germ cell abundance, a result of a point mutation in the c-kit gene that decreases kinase activity, as a genetic model for use in menopause studies.

METHODS

Physiological and morphological features associated with menopause were determined in female Wv/Wv mice compared with age-matched wildtype controls. Immunohistochemistry was used to evaluate the presence and number of follicles in paraffin-embedded ovaries. Bone density and body composition were evaluated using the PIXImus x-ray densitometer, and lipids, calcium, and hormone levels were determined in serum using antigen-specific enzyme immunoassays. Heart and body weight were measured, and cardiac function was evaluated using transthoracic echocardiography.

RESULTS

The ovaries of the Wv/Wv females have a greatly reduced number of normal germ cells at birth compared with wildtype mice. The remaining follicles are depleted by around 2 months, and the ovaries develop benign epithelial lesions that resemble morphological changes that occur during ovarian aging, whereas a normal mouse ovary has numerous follicles at all stages of development and retains some follicles even in advanced age. Wv mice have elevated plasma gonadotropins and reduced estrogen and progesterone levels, a significant reduction in bone mass density, and elevated serum cholesterol and lipoprotein levels. Moreover, the Wv female mice have enlarged hearts and reduced cardiac function.

CONCLUSIONS

The reduction of c-kit activity in Wv mice leads to a substantially diminished follicular endowment in newborn mice and premature depletion of follicles in young mice, although mutant females have a normal life span after cessation of ovarian function. The Wv female mice exhibit consistent physiological changes that resemble common features of postmenopausal women. These alterations include follicle depletion, morphological aging of the ovary, altered serum levels of cholesterol, gonadotropins and steroid hormones, decreased bone density, and reduced cardiac function. These changes were not observed in male mice, either age-matched male Wv/Wv or wildtype mice, and are improbably caused by global loss of c-kit function. The Wv mouse may be a genetic, intact-ovary model that mimics closely the phenotypes of human menopause to be used for further studies to understand the mechanisms of menopausal biology.

Immobilizing natural macromolecule on PLGA electrospun nanofiber with surface entrapment and entrapment-graft techniques

Surface entrapment is a convenient method to immobilize the natural macromolecules on the surface of synthetic polymers. In this study, the gelatin modified and sodium alginate/gelatin modified PLGA nanofibrous membranes were fabricated via surface entrapment and entrapment-graft techniques. The surface morphology of the each single modified PLGA nanofiber was as smooth as that of untreated PLGA nanofibers. The results of water angle contact measurements and tensile tests showed that the surface entrapment cannot only improve the hydrophilicity but also enhance mechanical properties of the modified nanofibrous membranes. In addition, the sodium alginate/gelatin modified electrospun PLGA nanofibrous membrane exhibited higher hydrophilicity and better biocompatibility than the simply gelatin modified PLGA nanofibrous membrane, which suggested the surface entrapment is a facile and efficient approach to surface modification for electrospun nanofibours membranes.

Toll-like receptor 4 signaling promotes the immunosuppressive cytokine production of human cervical cancer

OBJECTIVES

To investigate the expression of TLR-4 (toll-like receptor) on human cervical cancer and find the biological function of the TLR-4 signal system.

METHODS

The immunohistochemistry method was performed to study the protein expression and distribution of TLR-4. The viability of HeLa cells was determined by cell viability assay. Cell proliferation was detected by FCM, ELISA and Western blot were used to observe the gene and protein expression of IL-6 and TGF-beta1 in Hela cell lines.

RESULTS

TLR-4 was over-expressed in cervix cancer, and its activation by LPS promotes proliferation and anti-apoptosis in Hela cells in vitro. Moreover the cell line proliferation increased in a dose- and time-dependent manner. The production of IL-6 and TGF-beta1 were promoted through the activation of the NF-kappaB signaling pathway.

Potential of vesicular stomatitis virus as an oncolytic therapy for recurrent and drug-resistant ovarian cancer

In the last decade, we have gained significant understanding of the mechanism by which vesicular stomatitis virus (VSV) specifically kills cancer cells. Dysregulation of translation and defective innate immunity are both thought to contribute to VSV oncolysis. Safety and efficacy are important objectives to consider in evaluating VSV as a therapy for malignant disease. Ongoing efforts may enable VSV virotherapy to be considered in the near future to treat drug-resistant ovarian cancer when other options have been exhausted. In this article, we review the development of VSV as a potential therapeutic approach for recurrent or drug-resistant ovarian cancer.

Increased expression of Syne1/nesprin-1 facilitates nuclear envelope structure changes in embryonic stem cell differentiation

We found by electron microscopy that the inter-membrane space of embryonic stem cells is irregular and generally wider than in differentiated cells. Among a panel of nuclear envelope structural proteins examined, the expression of Syne1/nesprin-1 was found to be greatly induced upon differentiation. Down-regulation of Syne1 by siRNA in differentiated embryonic stem cells caused the nuclear envelope to adopt a configuration resembling that found in undifferentiated embryonic stem cells. Suppression of Syne1 expression did not produce a detectable impact on the retinoic acid-induced differentiation of embryonic stem cells; however, forced expression of Syne1 enhanced the tendency of the cells to lose pluripotency. Thus, we found that low expression of Syne1 splicing isoforms accounts for the wider and irregular nuclear envelope inter-membrane space in embryonic stem cells. We conclude that the nuclear envelope structural change accompanying differentiation likely participates in promoting the differential chromatin organization of the differentiated cells.

Ectopic expression of GATA6 bypasses requirement for Grb2 in primitive endoderm formation

Gene knockouts in mice have showed that Grb2 and GATA6 are essential for the formation of primitive endoderm in blastocysts. Here, we confirmed that implanted Grb2-null blastocysts lack primitive or extraembryonic endoderm cells either at E4.5 or E5.5 stages. We analyzed the relationship between Grb2 and GATA6 in the differentiation of embryonic stem (ES) cells to primitive endoderm in embryoid body models. Upon transfection with GATA6 expression vector, Grb2-null ES cells underwent endoderm differentiation as indicated by the expression of the extraembryonic endoderm markers Dab2 and GATA4. Transfection of GATA4 expression vector also had the same differentiation potency. When GATA6- or GATA4-transfected Grb2-null ES cells were allowed to aggregate, fragments of an endoderm layer formed on the surface of the spheroids. The results suggest that GATA6 is downstream of Grb2 in the inductive signaling pathway and the expression of GATA6 is sufficient to compensate for the defects caused by Grb2 deficiency in the development of the primitive and extraembryonic endoderm.

Alteration of Differentiation Potentials by Modulating GATA Transcription Factors in Murine Embryonic Stem Cells

Background. Mouse embryonic stem (ES) cells can be differentiated in vitro by aggregation and/or retinoic acid (RA) treatment. The principal differentiation lineage in vitro is extraembryonic primitive endoderm. Dab2, Laminin, GATA4, GATA5, and GATA6 are expressed in embryonic primitive endoderm and play critical roles in its lineage commitment. Results. We found that in the absence of GATA4 or GATA5, RA-induced primitive endoderm differentiation of ES cells was reduced. GATA4 (-/-) ES cells express higher level of GATA5, GATA6, and hepatocyte nuclear factor 4 alpha marker of visceral endoderm lineage. GATA5 (-/-) ES cells express higher level of alpha fetoprotein marker of early liver development. GATA6 (-/-) ES cells express higher level of GATA5 as well as mesoderm and cardiomyocyte markers which are collagen III alpha-1 and tropomyosin1 alpha. Thus, deletion of GATA6 precluded endoderm differentiation but promoted mesoderm lineages. Conclusions. GATA4, GATA5, and GATA6 each convey a unique gene expression pattern and influences ES cell differentiation. We showed that ES cells can be directed to avoid differentiating into primitive endoderm and to adopt unique lineages in vitro by modulating GATA factors. The finding offers a potential approach to produce desirable cell types from ES cells, useful for regenerative cell therapy.

Nuclear entry of activated MAPK is restricted in primary ovarian and mammary epithelial cells

Background

The MAPK/ERK1/2 serine kinases are primary mediators of the Ras mitogenic signaling pathway. Phosphorylation by MEK activates MAPK/ERK in the cytoplasm, and phospho-ERK is thought to enter the nucleus readily to modulate transcription.

Principal Findings

Here, however, we observe that in primary cultures of breast and ovarian epithelial cells, phosphorylation and activation of ERK1/2 are disassociated from nuclear translocalization and transcription of downstream targets, such as c-Fos, suggesting that nuclear translocation is limited in primary cells. Accordingly, in import assays in vitro, primary cells showed a lower import activity for ERK1/2 than cancer cells, in which activated MAPK readily translocated into the nucleus and activated c-Fos expression. Primary cells express lower levels of nuclear pore complex proteins and the nuclear transport factors, importin B1 and importin 7, which may explain the limiting ERK1/2 import found in primary cells. Additionally, reduction in expression of nucleoporin 153 by siRNA targeting reduced ERK1/2 nuclear activity in cancer cells.

Conclusion

ERK1/2 activation is dissociated from nuclear entry, which is a rate limiting step in primary cells and in vivo, and the restriction of nuclear entry is disrupted in transformed cells by the increased expression of nuclear pores and/or nuclear transport factors.

Cell adhesive affinity does not dictate primitive endoderm segregation and positioning during murine embryoid body formation

The classical cell sorting experiments undertaken by Townes and Holtfreter described the intrinsic propensity of dissociated embryonic cells to self-organize and reconcile into their original embryonic germ layers with characteristic histotypic positioning. Steinberg presented the differential adhesion hypothesis to explain these patterning phenomena. Here, we have reappraised these issues by implementing embryoid bodies to model the patterning of epiblast and primitive endoderm layers. We have used combinations of embryonic stem (ES) cells and their derivatives differentiated by retinoic acid treatment to model epiblast and endoderm cells, and wild-type or E-cadherin null cells to represent strongly or weakly adherent cells, respectively. One cell type was fluorescently labeled and reconstituted with another heterotypically to generate chimeric embryoid bodies, and cell sorting was tracked by time-lapse video microscopy and confirmed by immunostaining. When undifferentiated wild-type and E-cadherin null ES cells were mixed, the resulting cell aggregates consisted of a core of wild-type cells surrounded by loosely associated E-cadherin null cells, consistent with the differential adhesion hypothesis. However, when mixed with undifferentiated ES cells, the differentiated primitive endoderm-like cells sorted to the surface to form a primitive endoderm layer irrespective of cell-adhesive strength, contradicting the differential adhesion hypothesis. We propose that the primitive endoderm cells reach the surface by random movement, and subsequently the cells generate an apical/basal polarity that prevents reentry. Thus, the ability to generate epithelial polarity, rather than adhesive affinity, determines the surface positioning of the primitive endoderm cells.

Explicit targeting of transformed cells by VSV in ovarian epithelial tumor-bearing Wv mouse models

OBJECTIVE

Current treatment options for epithelial ovarian cancer are limited and therapeutic development for recurrent and drug-resistant ovarian cancer is an urgent agenda. We investigated the potential use of genetically engineered Vesicular Stomatitis Virus (VSV) to treat ovarian cancer patients who fail to respond to available therapies. Specifically, we examined the toxicity to hosts and specificity of targeting ovarian tumors using a Wv ovarian tumor model.

METHODS

We first tested recombinant VSV for oncolytic activity in a panel of human ovarian epithelial cancer, immortalized, and primary ovarian surface epithelial cells in culture. Then, we tested VSV oncolytic therapy using the immune competent Wv mice that develop tubular adenomas, benign tumor lesions derived from ovarian surface epithelial cells.

RESULTS

The expression of GFP encoded by the recombinant VSV genome was detected in about 5% of primary ovarian surface epithelial cells (3 lines) up to 30 days without significantly altering the growth pattern of the cells, suggesting the lack of toxicity to the normal ovarian surface epithelial cells. However, VSV-GFP was detected in the majority (around 90%) of cells that are either "immortalized" by SV40 antigen expression or cancer lines. Some variation in killing time courses was observed, but all the transformed cell lines were killed within 3 days. We found that regardless of the inoculation route (intra bursal, IP, or IV), VSV specifically infected and replicated in the in situ ovarian tumors in the Wv mice without significant activity in any other organs and tissues, and showed no detectable toxicity. The epithelial tumor lesions were greatly reduced in VSV-targeted ovarian tumors in the Wv mice.

CONCLUSIONS

VSV oncolytic activity depends on a cell autonomous property distinguishing primary and transformed cells. The efficient oncolytic activity of VSV for the "immortalized" non-tumorigenic ovarian surface epithelial cells suggests that the selective specificity extends from pre-neoplastic to overt cancer cells. The results demonstrated the explicit targeting of ovarian epithelial tumors by VSV in immune competent, ovarian tumor-bearing mouse models, and further support the utility of VSV as an effective and safe anti-cancer agent.

Loss of GATA4 and GATA6 expression specifies ovarian cancer histological subtypes and precedes neoplastic transformation of ovarian surface epithelia

BACKGROUND

The family of zinc finger-containing GATA transcription factors plays critical roles in cell lineage specification during early embryonic development and organ formation. GATA4 and GATA6 were found to be frequently lost in ovarian cancer, and the loss is proposed to account for dedifferentiation of the cancer cells.

METHODOLOGY/PRINCIPAL FINDINGS

We further investigated the expression of GATA4 and GATA6 in ovarian surface epithelial lesions and histological subtypes of ovarian carcinomas by immunostaining. GATA4 and GATA6 were found to be absent in high percentages (80 to 90%) of serous, clear cell, and endometrioid ovarian cancer examined. In contrast, both were found positive in 11 out of 12 cases of mucinous carcinomas, suggesting the expression of the GATA factors can distinguish mucinous cancer from other histological subtypes. GATA4 was frequently lost in preneoplastic lesions such as morphologically normal inclusion cysts and epithelial hyperplasia adjacent to malignant cells. The loss of GATA6 correlates closely with neoplastic morphological transformation of ovarian surface epithelia. In culture, GATA4 expression was progressively reduced upon passaging primary ovarian surface epithelial cells, which correlated with changes in histone modification of the GATA4 locus. A reduced GATA6 gene dosage as in GATA6 (+/-) mice led to an increased pre-neoplastic changes and inclusion cysts in the ovaries, suggesting the loss of GATA6 contributes to ovarian cancer development.

CONCLUSIONS/SIGNIFICANCE

This study suggests that the expression status of GATA4 and GATA6 may dictate distinct pathologic pathways leading to serous or mucinous ovarian carcinomas. The readily loss of GATA4 expression through changes in chromatin conformation suggests a potential non-phenotypic initiating event, leading to subsequent loss of GATA6, morphological transformation, and ultimate tumorigenesis.

C-Fos elimination compensates for disabled-2 requirement in mouse extraembryonic endoderm development

Disabled-2 (Dab2) is expressed in primitive endoderm cells as they are differentiating from the inner cell mass and dab2 deficiency in mice results in lethality at E5.5-E6.5 due to the disorganization of the endoderm layers. Here we show that Dab2 suppresses c-Fos expression in endoderm cells. A morphological normal primitive endoderm layer was observed in putative E5.5 dab2 (-/-):c-fos (-/-) embryos, indicating that the primitive endoderm defect due to the loss of Dab2 is rescued by deletion of the c-fos gene. The lethality of the double knockout embryos was delayed until E9.5-E10.5 and the defective embryos failed to undergo organogenesis. We conclude that Dab2 plays a role in epithelial organization by suppression of c-Fos expression and suggest that unsuppressed c-Fos can lead to disruption of primitive endoderm epithelial organization, yet an additional dab2 function is required for later organogenesis.

Acquisition of a second mutation of the Tp53 alleles immediately precedes epithelial morphological transformation in ovarian tumorigenicity

OBJECTIVE

Tp53 mutation is frequent and associates with malignant, high-grade ovarian cancer. However, the details about the progression of Tp53 mutation from heterozygous to homozygous, and association between genotypes and morphological transformation are not clear. We further investigated the expression and mutation of Tp53 and associated markers such as p21 and HDM2 in ovarian cancer.

METHOD

Areas of contiguous ovarian surface epithelia linking morphological normal monolayer to multilayer neoplastic cells were analyzed for the correlation of Tp53 pathway alteration in relation to morphological transformation, by immunostaining and sequencing of Tp53 gene in cells from laser captured microdissection.

RESULTS

Consistent with previous reports, Tp53 staining is positive in 78% of the tumors. The staining of p21 is positive in about 12%, and HMD2 is positive in only 1% of the tumors. In 9 out of 10 cases of p21-positive tumors, p53 is also positive. In the majority of cases of epithelial histological transitions, overexpression of Tp53 correlates with morphological transformation: Tp53 is negative in monolayered cells and positive in neoplastic lesions. Morphological transformation also closely correlates with cell proliferation as indicated by Ki-67 staining and loss of p21 expression. We detected heterozygous mutation of Tp53 in the monolayers adjacent to neoplastic cells.

CONCLUSIONS

p21 expression is an indicator of a wild type Tp53 and lack of p21 in the presence of Tp53 expression predicts an inactivated Tp53. Tp53 inactivation immediately precedes morphological transformation of the ovarian surface epithelium in most cases, and the histological transitional epithelia containing a heterozygous Tp53 mutation are thus pre-neoplastic lesions. We propose that the loss of a second allele of Tp53 leading to the loss of p21 expression, and subsequent cell proliferation, compose a sequence of events that lead to morphological transformation and instigation of ovarian epithelial tumor development.

Ovarian ageing, follicle depletion, and cancer: a hypothesis for the aetiology of epithelial ovarian cancer involving follicle depletion

The association between ovarian cancer risk and reproductive factors has been well established, and two main theories, incessant ovulation and gonadotropin stimulation, have been proposed to explain the mechanism. Recent studies using animal models of ovarian tumorigenesis, and analysis of ovarian tissues from prophylactic oophorectomies, suggest that depletion of ovarian follicles might underlie the epidemiological findings linking reproductive history and ovarian cancer risk.

Dynamic GATA6 expression in primitive endoderm formation and maturation in early mouse embryogenesis

The derivation of the primitive endoderm layer from the pluripotent cells of the inner cell mass is one of the earliest differentiation and morphogenic events in embryonic development. GATA4 and GATA6 are the key transcription factors in the formation of extraembryonic endoderms, but their specific contribution to the derivation of each endoderm lineage needs clarification. We further analyzed the dynamic expression and mutant phenotypes of GATA6 in early mouse embryos. GATA6 and GATA4 are both expressed in primitive endoderm cells initially. At embryonic day (E) 5.0, parietal endoderm cells continue to express both GATA4 and GATA6; however, visceral endoderm cells express GATA4 but exhibit a reduced expression of GATA6. By and after E5.5, visceral endoderm cells no longer express GATA6. We also found that GATA6 null embryos did not form a morphologically recognizable primitive endoderm layer, and subsequently failed to form visceral and parietal endoderms. Thus, the current study establishes that GATA6 is essential for the formation of primitive endoderm, at a much earlier stage then previously recognized, and expression of GATA6 discriminates parietal endoderm from visceral endoderm lineages.

Mammalian target of rapamycin is the key effector of phosphatidylinositol-3-OH-initiated proliferative signals in the thyroid follicular epithelium

Activation of the phosphatidylinositol-3-OH kinase (PI3K) signaling cascade is becoming increasingly recognized as a common feature of thyroid follicular neoplasms. We have recently shown that conditional loss of Pten in the mouse thyroid follicular cells is sufficient to stimulate continuous autonomous growth, leading to a homogeneously hyperplastic gland and to the development of follicular adenomas. Because the PI3K/AKT cascade can activate a plethora of different signaling pathways, it is still unclear which of these may represent the key mitogenic output of PI3K-initiated signaling. Here, we show that the in vivo proliferative response to chronic PI3K activation profoundly relies on the activation of the mammalian target of rapamycin (mTOR)/S6K1 axis, and that mTOR inhibition in Pten mutant mice and cells restores virtually normal proliferation rates, despite the presence of still elevated Akt activity, at least in part by down-regulating cyclins D1 and D3, and without affecting cell survival.