Expression of cell cycle regulatory proteins (p53, pRb) in the human female genital tract

A critical evaluation of ovarian tissue cryopreservation and grafting as a strategy for preserving the human female germline

Ovarian tissue freezing has been used successfully in animals and it has recently begun to be offered clinically to young women who have medical conditions with a high risk of sterility. Although no frozen human ovarian grafts have yet been returned to the donor and resulted in a pregnancy, there are many indications that this procedure should be feasible. Although live young have been derived from frozen grafts in several species, research should aim to make further improvements to the cryopreservation and grafting procedures to optimize follicle survival, and hence minimize the amount of tissue that needs to be collected, stored and returned. Ovarian tissue freezing, particular if used in combination with egg and embryo freezing, should allow a patient to safeguard their chance of becoming a parent later (Table 1). In cases where the patient has a systemic cancer or infection and malignant cells or viruses may be present in the systemic circulation and the gonadal tissue, ovarian tissue could be collected and frozen, but grafting is not currently recommended (Table 3).

p16, retinoblastoma (pRb), and cyclin D1 protein expression in human endometriotic and adenomyotic lesions

OBJECTIVE

To investigate the expression of p16, retinoblastoma (pRb), and cyclin D1 oncoproteins in endometriomas and adenomyosis.

DESIGN

Immunohistochemical study for p16, pRb, and cyclin D1 proteins in formalin-fixed paraffin-embedded endometriotic and adenomyotic tissues.

SETTING

University hospital.

PATIENT(S)

Tissues from 25 women with endometriomas and 31 women with adenomyosis were evaluated.

INTERVENTION(S)

Tissue samples were collected during gynecologic surgery and confirmed by histology to have endometriosis or adenomyosis. Nuclear expression of p16, pRb, and cyclin D1 proteins was examined by immunohistochemistry.

MAIN OUTCOME MEASURE(S)

Distribution and intensity of immunostaining.

RESULT(S)

In the proliferative phase of the cycle, p16 was detected in 77% of adenomyosis tissues but in only 15% of endometriosis tissues. Moreover, in adenomyosis samples positive for p16, 100% of the adenomyotic cells expressed p16, whereas only 10%-20% of endometriosis cells from positive cases expressed p16. In contrast, pRb was detected in 28% of endometriosis cases but not in any adenomyotic tissues. Cyclin D1 was absent in both endometriotic and adenomyotic tissue samples.

CONCLUSION(S)

Differences in oncoprotein expression between endometriotic and adenomyotic tissues provide further evidence that the pathogenesis of endometriosis is different from that of adenomyosis.

Identification of cytoplasmic p53 protein in corneal epithelium of vertebrates

The tumour suppressor gene p53 encodes a phosphoprotein involved in the control of cell growth. It's expression and function have been documented in malignancy, apoptosis and the aging processes. Recently, p53 expression has been demonstrated in normal murine tissues, including whole eye. Currently, we intend to map and to characterize p53 expression in the normal cornea across different species. To do this, eyes of animals were enucleated after sacrifice by CO(2) narcosis and then p53 expression in whole eyes (cornea) was mapped by indirect immunohistochemical staining techniques using the anti-p53 monoclonal antibodies PAb 248, PAb 421 and PAb 240 (alternatively called mAb 248, mAb 421 and mAb 240, respectively). Additionally, eyes were freshly dissected to separate the corneas, for quantitating p53 expression, using Western blot analysis. We found strong cytoplasmic p53 expression in the corneal epithelium of various vertebrate species by immunohistochemistry and by Western analysis. High levels of cytoplasmic p53 protein were normally found in normal corneal epithelium of various vertebrate species. Hence, these data may indicate that p53 may have a new evolutionary significant function in the eye.

Expression patterns of retinoblastoma protein in Parkinson disease

Cellular mechanisms implicated in Parkinson disease (PD) include oxidative stress, inflammatory response, excess dopamine, DNA damage, and loss of trophic support. These stimuli have been observed to induce changes in cell cycle proteins in several cell types. One of the key regulators of cell cycle progression is the retinoblastoma protein (pRb); therefore, we assessed the staining for pRb and its inactive hyperphosphorylated isoform, ppRb, in autopsy tissue from patients with PD. In PD we found abundant pRb staining in neuronal cytoplasm of the substantia nigra, mid-frontal cortex, and hippocampus by immunohistochemistry. In controls, pRb weakly stained nucleoli of neurons in the substantia nigra and exhibited no detectable staining in mid-frontal cortex and hippocampus. Staining for ppRb resulted in a shift from weak cytoplasmic staining in neurons from control cases to strong nuclear staining in PD cases, especially within the substantia nigra, mid-frontal cortex, and hippocampus. In the substantia nigra, ppRb also co-localized to Lewy bodies, which are a pathologic feature of PD. Lewy bodies are also found in diffuse Lewy body disease (DLBD) that do not consistently exhibit changes in pRb or ppRb. These results indicate that there are changes in pRb and its inactive phospho-isoform in neurons responding to neurodegenerative stimuli associated with PD.

Stress-dependent nucleolin mobilization mediated by p53-nucleolin complex formation

We recently discovered that heat shock causes nucleolin to relocalize from the nucleolus to the nucleoplasm, whereupon it binds replication protein A and inhibits DNA replication initiation. We report that nucleolin mobilization also occurs following exposure to ionizing radiation (IR) and treatment with camptothecin. Mobilization was selective in that another nucleolar marker, upstream binding factor, did not relocalize in response to IR. Nucleolin relocalization was dependent on p53 and stress, the latter initially stimulating nucleolin-p53 complex formation. Nucleolin relocalization and complex formation in vivo were independent of p53 transactivation but required the p53 C-terminal regulatory domain. Nucleolin and p53 also interact directly in vitro, with a similar requirement for p53 domains. These data indicate a novel p53-dependent mechanism in which cell stress mobilizes nucleolin for transient replication inhibition and DNA repair.

Repression of RNA polymerase I transcription by the tumor suppressor p53

The tumor suppressor protein p53 is frequently inactivated in tumors. It functions as a transcriptional activator as well as a repressor for a number of viral and cellular promoters transcribed by RNA polymerase II (Pol II) and by RNA Pol III. Moreover, it appears that p53 also suppresses RNA Pol I transcription. In this study, we examined the molecular mechanism of Pol I transcriptional inhibition by p53. We show that wild-type, but not mutant, p53 can repress Pol I transcription from a human rRNA gene promoter in cotransfection assays. Furthermore, we show that recombinant p53 inhibits rRNA transcription in a cell-free transcription system. In agreement with these results, p53-null epithelial cells display an increased Pol I transcriptional activity compared to that of epithelial cells that express p53. However, both cell lines display comparable Pol I factor protein levels. Our biochemical analysis shows that p53 prevents the interaction between SL1 and UBF. Protein-protein interaction assays indicate that p53 binds to SL1, and this interaction is mostly mediated by direct contacts with TATA-binding protein and TAF(I)110. Moreover, template commitment assays show that while the formation of a UBF-SL1 complex can partially relieve the inhibition of transcription, only the assembly of a UBF-SL1-Pol I initiation complex on the rDNA promoter confers substantial protection against p53 inhibition. In summary, our results suggest that p53 represses RNA Pol I transcription by directly interfering with the assembly of a productive transcriptional machinery on the rRNA promoter.

Drosophila p53 is a structural and functional homolog of the tumor suppressor p53

The importance of p53 in carcinogenesis stems from its central role in inducing cell cycle arrest or apoptosis in response to cellular stresses. We have identified a Drosophila homolog of p53 ("Dmp53"). Like mammalian p53, Dmp53 binds specifically to human p53 binding sites, and overexpression of Dmp53 induces apoptosis. Importantly, inhibition of Dmp53 function renders cells resistant to X ray-induced apoptosis, suggesting that Dmp53 is required for the apoptotic response to DNA damage. Unlike mammalian p53, Dmp53 appears unable to induce a G1 cell cycle block when overexpressed, and inhibition of Dmp53 activity does not affect X ray-induced cell cycle arrest. These data reveal an ancestral proapoptotic function for p53 and identify Drosophila as an ideal model system for elucidating the p53 apoptotic pathway(s) induced by DNA damage.

New approaches to increasing oocyte yield from ruminants

Artificial insemination, superovulation and embryo transfer have had beneficial impacts on animal production but a limiting factor to realizing the full potential of these techniques and of other reproductive technologies is the availability of fertile oocytes. To overcome this problem, methods for maturing oocytesin vitro(IVM) have been developed. The production of bovine embryos by IVM is in commercial use but the rate of success and quality of embryos is low. The lack of success may be due to the quality of oocytes that are being matured and it would be preferable to utilize the abundant source of immature oocytes from preantral and primordial follicles by developing systems forin vitrogrowth (IVG). Several culture systems that utilize early growing follicles as a source of oocytes have been developed for laboratory species and these have been successful in producing live young. IVG in association with IVM and cryopreservation have the potential to maximize the genetic potential of high genetic merit females and shorten generation intervals. This paper presents the current status of technology for thein vitrogrowth and development of immature oocytes,in vitromaturation and cryopreservation of germ cells in domestic ruminants.

Autoantibodies to p53 in ovarian cancer patients and healthy women: a comparison between whole p53 protein and 18-mer peptides for screening purposes

Autoantibodies against complete p53 protein and 18-mer peptides of p53 in ovarian cancer patients and healthy women were examined. Sera from 9% (4/46) of ovarian cancer patients but none (0/51) of healthy women recognized complete p53 protein. The antibodies were mainly of the IgG1 isotype. Two patients had also IgG2 antibodies. Sera from 28% (13/46) of cancer patients and 21% (11/52) of healthy women contained either IgM, or IgM plus IgG2 antibodies against 18-mer p53 peptides. Screening against complete p53 protein instead of peptides seems necessary for identifying patients with tumor-related antibodies. IgG2 antibodies against p53 suggest p53-specific CD4+ T helper 1 cell activity in some of the ovarian cancer patients.