To describe the clinical management of ovarian stromal cell tumors, which are a heterogeneous group of neoplasms that develop from the sex cords and the ovarian stroma.
We reviewed the current ...evidence on the clinical management of these relatively rare ovarian malignancies, which are typically detected at an early stage and may recur as late as 30 years following the initial treatment. The overall prognosis is favorable with a long-term survival ranging from 75% to 90% for all stages. Adult granulosa cell tumor (GCT) is the most common malignancy among these tumors.
Surgery is the cornerstone of initial treatment. In women of childbearing age and with disease limited to one ovary, a fertility-sparing surgery can be a reasonable approach. Tumor stage represents the most important clinical parameter of prognostic relevance. The value of postoperative adjuvant therapy for high-risk patients has not been proven by prospective randomized studies. Platinum-based chemotherapy is used currently for patients with advanced stages or recurrent disease, with an overall response rate of 63% to 80%. Taxane and platinum combination chemotherapy seems to be a reasonable candidate for future trials. Little evidence exists for the use of radiation or hormonal therapy, and these modalities should be restricted to selected cases. Given the propensity of GCT for late relapse, prolonged follow-up is required.
Surgery remains the most effective treatment for ovarian stromal tumors and, whenever feasible, for relapsing disease. Platinum-based chemotherapy is currently used in metastatic or recurrent tumors.
DNA damage leads to a halt in proliferation owing to apoptosis or senescence, which prevents transmission of DNA alterations. This cellular response depends on the tumor suppressor p53 and functions ...as a powerful barrier to tumor development. Adult stem cells are resistant to DNA damage-induced apoptosis or senescence, however, and how they execute this response and suppress tumorigenesis is unknown. We show that irradiation of hematopoietic and mammary stem cells up-regulates the cell cycle inhibitor p21, a known target of p53, which prevents p53 activation and inhibits p53 basal activity, impeding apoptosis and leading to cell cycle entry and symmetric self-renewing divisions. p21 also activates DNA repair, limiting DNA damage accumulation and self-renewal exhaustion. Stem cells with moderate DNA damage and diminished self-renewal persist after irradiation, however. These findings suggest that stem cells have evolved a unique, p21-dependent response to DNA damage that leads to their immediate expansion and limits their long-term survival.
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Histone deacetylases (HDACs) regulate transcription and specific cellular functions, such as tumor suppression by p53, and are frequently altered in cancer. Inhibitors of HDACs (HDACIs) possess ...antitumor activity and are well tolerated, supporting the idea that their use might develop as a specific strategy for cancer treatment. The molecular basis for their selective antitumor activity is, however, unknown. We investigated the effects of HDACIs on leukemias expressing the PML-RAR or AML1-ETO oncoproteins, known to initiate leukemogenesis through deregulation of HDACs. Here we report that: (i) HDACIs induce apoptosis of leukemic blasts, although oncogene expression is not sufficient to confer HDACI sensitivity to normal cells; (ii) apoptosis is p53 independent and depends, both in vitro and in vivo, upon activation of the death receptor pathway (TRAIL and Fas signaling pathways); (iii) TRAIL, DR5, FasL and Fas are upregulated by HDACIs in the leukemic cells, but not in normal hematopoietic progenitors. These results show that sensitivity to HDACIs in leukemias is a property of the fully transformed phenotype and depends on activation of a specific death pathway.
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DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Mutations of p53 are remarkably rare in acute promyelocytic leukemias (APLs). Here, we demonstrate that the APL‐associated fusion proteins PML–RAR and PLZF‐RAR directly inhibit p53, allowing leukemic ...blasts to evade p53‐dependent cancer surveillance pathways. PML–RAR causes deacetylation and degradation of p53, resulting in repression of p53 transcriptional activity, and protection from p53‐dependent responses to genotoxic stress. These phenomena are dependent on the expression of wild‐type PML, acting as a bridge between p53 and PML–RAR. Recruitment of histone deacetylase (HDAC) to p53 and inhibition of p53 activity were abrogated by conditions that either inactivate HDACs or trigger HDAC release from the fusion protein, implicating recruitment of HDAC by PML–RAR as the mechanism underlying p53 inhibition.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Histone deacetylases (HDACs) regulate transcription and specific functions, such as tumor suppression by p53, and are frequently altered in cancer. Inhibitors of HDACs (HDACI) possess anti-tumor ...activity and are well tolerated, suggesting that they might develop into a specific strategy for cancer treatment. Indeed, HDACIs have successfully entered clinical trials, but the molecular basis for their selective anti-tumor activities is not clear. Recent work on leukemias expressing the PML-RAR or AML1-ETO oncogenes, known to initiate leukemogenesis through deregulation of HDACs, shows that HDACIs induce massive blast-cell apoptosis. Interestingly, the pro-apoptotic activity of the drug is not due to the relief of oncogene-mediated inhibition of the p53 tumor-suppressor pathway but, instead, relies on the selective upregulation of the death receptors DR5 and Fas and their cognate ligands TRAIL and FasL. Significantly, normal myeloid progenitors are not sensitive to HDACI-induced apoptosis and oncogene expression is not sufficient to confer HDACI-sensitivity to normal cells, demonstrating that sensitivity to HDACI is a property of the fully transformed phenotype. In principle, our findings could thus apply to other cancers, where the contribution of HDACs to tumorigenesis is not yet defined.
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Human herpesvirus 6 (HHV-6) employs the complement regulator CD46 (membrane cofactor protein) as a receptor for fusion and entry into target cells. Like other known herpesviruses, HHV-6 encodes ...multiple glycoproteins, several of which have been implicated in the entry process. In this report, we present evidence that glycoprotein H (gH) is the viral component responsible for binding to CD46. Antibodies to CD46 co-immunoprecipitated an ∼110-kDa protein band specifically associated with HHV-6-infected cells. This protein was identified as gH by selective depletion with an anti-gH monoclonal antibody, as well as by immunoblot analysis with a rabbit hyperimmune serum directed against a gH synthetic peptide. In reciprocal experiments, a monoclonal antibody against HHV-6 gH was found to co-immunoprecipitate CD46. Studies using monoclonal antibodies directed against specific CD46 domains, as well as engineered constructs lacking defined CD46 regions, demonstrated a close correspondence between the CD46 domains involved in the interaction with gH and those previously shown to be critical for HHV-6 fusion (i.e. short consensus repeats 2 and 3).
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The emerging role of p53 in stem cells Bonizzi, Giuseppina; Cicalese, Angelo; Insinga, Alessandra ...
Trends in molecular medicine,
01/2012, Volume:
18, Issue:
1
Journal Article
Peer reviewed
Open access
Among the hundreds of oncogenes and tumor suppressors that have been identified in the past 50 years, p53 is probably the best characterized; nevertheless, new functions are constantly being ...discovered. As a tumor suppressor, p53 regulates cellular responses to different stress stimuli by inducing reversible cell cycle arrest and DNA repair, or triggering senescence or apoptosis. Recent findings on the regulation of stem cell (SC) division and reprogramming suggest the intriguing possibility that p53 also carries out its tumor suppression function by regulating SC homeostasis. Specifically, p53 activation may counteract SC expansion by several emerging mechanisms including restriction of self-renewing divisions, inhibition of symmetric division and block of reprogramming of somatic/progenitor cells into SCs.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
DNA damage response in adult stem cells Insinga, Alessandra; Cicalese, Angelo; Pelicci, Pier Giuseppe
Blood cells, molecules, & diseases,
04/2014, Volume:
52, Issue:
4
Journal Article
Peer reviewed
This review discusses the processes of DNA-damage-response and DNA-damage repair in stem and progenitor cells of several tissues. The long life-span of stem cells suggests that they may respond ...differently to DNA damage than their downstream progeny and, indeed, studies have begun to elucidate the unique stem cell response mechanisms to DNA damage. Because the DNA damage responses in stem cells and progenitor cells are distinctly different, stem and progenitor cells should be considered as two different entities from this point of view. Hematopoietic and mammary stem cells display a unique DNA-damage response, which involves active inhibition of apoptosis, entry into the cell-cycle, symmetric division, partial DNA repair and maintenance of self-renewal. Each of these biological events depends on the up-regulation of the cell-cycle inhibitor p21. Moreover, inhibition of apoptosis and symmetric stem cell division are the consequence of the down-regulation of the tumor suppressor p53, as a direct result of p21 up-regulation. A deeper understanding of these processes is required before these findings can be translated into human anti-aging and anti-cancer therapies. One needs to clarify and dissect the pathways that control p21 regulation in normal and cancer stem cells and define (a) how p21 blocks p53 functions in stem cells and (b) how p21 promotes DNA repair in stem cells. Is this effect dependent on p21s ability to inhibit p53? Such molecular knowledge may pave the way to methods for maintaining short-term tissue reconstitution while retaining long-term cellular and genomic integrity.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Leukemic cells are defined by two main biological features: arrest ofdifferentiation at a specific stage compatible with continuedproliferation, and enhanced resistance to stress. Recent work ...showsthat the leukemia-associated fusion protein PML-RAR can mediate bothbiological effects targeting independent pathways, through a unifyingmechanism. Differentiation block is achieved through transcriptionalsilencing of genes physiologically regulated by RAR, which are involvedin hematopoietic differentiation. In contrast, enhanced resistance tostress is due to the capacity of the fusion protein to cause degradationof the tumor suppressor p53, thus explaining the puzzling observationthat mutations of p53 are remarkably rare in acute myeloid leukemias(AMLs). Interestingly, this latter phenomenon depends on expression ofwild-type PML, acting as a molecular bridge between p53 and the fusionprotein. Strikingly, both effects require a unifying molecular mechanism:aberrant recruitment of histone deacetylases (HDACs). Therefore, thestudy of this form of leukemia appears also of interest for a betterunderstanding of the action of HDAC inhibitors, potential antitumordrugs that are at the early stages of clinical studies.
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BFBNIB, GIS, IJS, KISLJ, NUK, PNG, UL, UM, UPUK
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