Clinical evaluation and treatment in men with low testosterone levels and prostate cancer

INTRODUCTION

A high prevalence of low testosterone levels has been reported in men with prostate cancer. The use of testosterone therapy in men with a history of prostate cancer is still controversial, and there is uncertainty regarding the management of these patients.

METHODS

We analyzed the European and American guidelines on this topic and presented the clinical experience in the management of patients with low testosterone levels and a history of prostate cancer in one of the world's leading cancer centers.

RESULTS

According to the published evidence to date, testosterone therapy in men with prostate cancer does not increase the risk of prostate cancer recurrence in the short and medium term, but there is a lack of data on the long term. Symptomatic men with low testosterone levels who are candidates for this therapy need a thorough clinical evaluation before commencing testosterone therapy. Evaluation of prostate cancer history including type of treatment administered, pathologic stage of prostate cancer and prostate specific antigen should be requested before and during testosterone treatment to assess its trend.

CONCLUSION

Prostate-specific antigen should remain undetectable after radical prostatectomy or stable after radiotherapy. Otherwise, it would be a sign of uncontrolled prostate cancer, and the patient may require cessation of testosterone therapy and referral to oncology for further evaluation.

A mouse model for Li-Fraumeni-Like Syndrome with cardiac angiosarcomas associated to POT1 mutations

The shelterin protein POT1 has been found mutated in many different familial and sporadic cancers, however, no mouse models to understand the pathobiology of these mutations have been developed so far. To address the molecular mechanisms underlying the tumorigenic effects of POT1 mutant proteins in humans, we have generated a mouse model for the human POT1^R117C mutation found in Li-Fraumeni-Like families with cases of cardiac angiosarcoma by introducing this mutation in the Pot1a endogenous locus, knock-in for Pot1a^R117C. We find here that both mouse embryonic fibroblasts (MEFs) and tissues from Pot1a^+/ki mice show longer telomeres than wild-type controls. Longer telomeres in Pot1a^+/ki MEFs are dependent on telomerase activity as they are not found in double mutant Pot1a^+/kiTert^-/- telomerase-deficient MEFs. By using complementation assays we further show that POT1a pR117C exerts dominant-negative effects at telomeres. As in human Li-Fraumeni patients, heterozygous Pot1a^+/ki mice spontaneously develop a high incidence of angiosarcomas, including cardiac angiosarcomas, and this is associated to the presence of abnormally long telomeres in endothelial cells as well as in the tumors. The Pot1a^+/R117C mouse model constitutes a useful tool to understand human cancers initiated by POT1 mutations.

We have generated a mouse model for the human POT1^R117C mutation found in Li-Fraumeni-Like (LFL) families with cases of cardiac angiosarcoma by introducing this mutation in the Pot1a endogenous locus, knock-in for Pot1a^R117C. The Pot1a^+/ki mice show longer telomeres than wild-type controls. Longer telomeres in mutant mice are dependent on telomerase activity as they are not found in a telomerase deficient background. As in human Li-Fraumeni patients, heterozygous Pot1a^+/ki mice spontaneously develop a high incidence of angiosarcomas, including cardiac angiosarcomas, and this is associated to the presence of abnormally long telomeres in endothelial cells as well as in the tumors. The ki-Pot1a^R117C mouse constitutes a potential pre-clinical mouse model for LFL syndrome presenting with high angiosarcoma incidence that could provide in the future a very useful tool for the study of treatments for these tumors.

Stromal Oncostatin M cytokine promotes breast cancer progression by reprogramming the tumour microenvironment

The tumor microenvironment (TME) is reprogrammed by cancer cells and participates in all stages of tumor progression. The contribution of stromal cells to the reprogramming of the TME is not well understood. Here, we provide evidence of the role of the cytokine oncostatin M (OSM) as central node for multicellular interactions between immune and nonimmune stromal cells and the epithelial cancer cell compartment. OSM receptor (OSMR) deletion in a multistage breast cancer model halted tumor progression. We ascribed causality to the stromal function of the OSM axis by demonstrating reduced tumor burden of syngeneic tumors implanted in mice lacking OSMR. Single-cell and bioinformatic analysis of murine and human breast tumors revealed that OSM expression was restricted to myeloid cells, whereas OSMR was detected predominantly in fibroblasts and, to a lower extent, cancer cells. Myeloid-derived OSM reprogrammed fibroblasts to a more contractile and tumorigenic phenotype and elicited the secretion of VEGF and proinflammatory chemokines CXCL1 and CXCL16, leading to increased myeloid cell recruitment. Collectively, our data support the notion that the stromal OSM/OSMR axis reprograms the immune and nonimmune microenvironment and plays a key role in breast cancer progression.

Genetic manipulation of LKB1 elicits lethal metastatic prostate cancer

Gene dosage is a key defining factor to understand cancer pathogenesis and progression, which requires the development of experimental models that aid better deconstruction of the disease. Here, we model an aggressive form of prostate cancer and show the unconventional association of LKB1 dosage to prostate tumorigenesis. Whereas loss of Lkb1 alone in the murine prostate epithelium was inconsequential for tumorigenesis, its combination with an oncogenic insult, illustrated by Pten heterozygosity, elicited lethal metastatic prostate cancer. Despite the low frequency of LKB1 deletion in patients, this event was significantly enriched in lung metastasis. Modeling the role of LKB1 in cellular systems revealed that the residual activity retained in a reported kinase-dead form, LKB1^K78I, was sufficient to hamper tumor aggressiveness and metastatic dissemination. Our data suggest that prostate cells can function normally with low activity of LKB1, whereas its complete absence influences prostate cancer pathogenesis and dissemination.

SOX9 promotes tumor progression through the axis BMI1-p21CIP

The developmental regulator SOX9 is linked to cancer progression mainly as a result of its role in the regulation of cancer stem cells (CSCs). However, its activity in the differentiated cells that constitute the heterogeneous tumor bulk has not been extensively studied. In this work, we addressed this aspect in gastric cancer, glioblastoma and pancreatic adenocarcinoma. SOX9 silencing studies revealed that SOX9 is required for cancer cell survival, proliferation and evasion of senescence in vitro and tumor growth in vivo. Gain of-SOX9 function showed that high levels of SOX9 promote tumor cell proliferation in vitro and in vivo. Mechanistically, the modulation of SOX9 changed the expression of the transcriptional repressor BMI1 in the same direction in the three types of cancer, and the expression of the tumor suppressor p21^CIP in the opposite direction. In agreement with this, SOX9 expression positively correlated with BMI1 levels and inversely with p21^CIP in clinical samples of the different cancers. Moreover, BMI1 re-establishment in SOX9-silenced tumor cells restored cell viability and proliferation as well as decreased p21^CIPin vitro and tumor growth in vivo. These results indicate that BMI1 is a critical effector of the pro-tumoral activity of SOX9 in tumor bulk cells through the repression of p21^CIP. Our results highlight the relevance of the SOX9-BMI1-p21^CIP axis in tumor progression, shedding novel opportunities for therapeutic development.

Safety of Whole-Body Abrogation of the TRF1 Shelterin Protein in Wild-Type and Cancer-Prone Mouse Models

Telomeres are considered potential anti-cancer targets. Most studies have focused on telomerase inhibition, but this strategy has largely failed in clinical trials. Direct disruption of the shelterin complex through TRF1 inhibition can block tumorigenesis in cancer mouse models by a mechanism that involves DNA damage induction and reduction of proliferation and stemness. Any anti-cancer target, however, must fulfill the requisite of not showing deleterious effects in healthy tissues. Here, we show that Trf1 genetic deletion in wild-type and cancer-prone p53- and Ink4Arf-deficient mice does not affect organismal viability and only induces mild phenotypes like decreased body weight and hair graying or hair loss, the skin being the most affected tissue. Importantly, we found that Trf1 is essential for tumorigenesis in p53- and Ink4Arf-deficient mice, as we did not find a single tumor originating from Trf1-deleted cells. These findings indicate a therapeutic window for targeting Trf1 in cancer treatment.

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Trf1 deletion does not affect organism viability in WT and cancer-prone mouse models

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Trf1 deletion only induces mild phenotypes in adult tissues, especially in the skin

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No tumors originate from Trf1-deleted cells

Protective Role of Hepatocyte Cyclooxygenase-2 Expression Against Liver Ischemia-Reperfusion Injury in Mice

Liver ischemia and reperfusion injury (IRI) remains a serious clinical problem affecting liver transplantation outcomes. IRI causes up to 10% of early organ failure and predisposes to chronic rejection. Cyclooxygenase-2 (COX-2) is involved in different liver diseases, but the significance of COX-2 in IRI is a matter of controversy. This study was designed to elucidate the role of COX-2 induction in hepatocytes against liver IRI. In the present work, hepatocyte-specific COX-2 transgenic mice (hCOX-2-Tg) and their wild-type (Wt) littermates were subjected to IRI. hCOX-2-Tg mice exhibited lower grades of necrosis and inflammation than Wt mice, in part by reduced hepatic recruitment and infiltration of neutrophils, with a concomitant decrease in serum levels of proinflammatory cytokines. Moreover, hCOX-2-Tg mice showed a significant attenuation of the IRI-induced increase in oxidative stress and hepatic apoptosis, an increase in autophagic flux, and a decrease in endoplasmic reticulum stress compared to Wt mice. Interestingly, ischemic preconditioning of Wt mice resembles the beneficial effects observed in hCOX-2-Tg mice against IRI due to a preconditioning-derived increase in endogenous COX-2, which is mainly localized in hepatocytes. Furthermore, measurement of prostaglandin E₂ (PGE₂ ) levels in plasma from patients who underwent liver transplantation revealed a significantly positive correlation of PGE₂ levels and graft function and an inverse correlation with the time of ischemia. Conclusion: These data support the view of a protective effect of hepatic COX-2 induction and the consequent rise of derived prostaglandins against IRI.

Dairy cows fed on tropical legume forages: effects on milk yield, nutrients use efficiency and profitability

Two trials with multiparous dairy cows were conducted. Experiment 1 tested the effects of increasing forage proportion in the diet (500, 600, and 700 g/kg DM) when a mixed sorghum (Sorghum bicolor) and jackbean (Cannavalia ensiformis) silage was used as forage. Experiment 2 studied the substitution of sorghum silage and soybean meal by jackbean silage or fresh cowpea (Vigna unguiculata) forage in the diet. All diets were iso-energetic and iso-proteic. In each experiment, 30 cows were used and separated into three groups. In experiment 1, there were no differences in dry matter intake (DMI), milk yield (MY), or apparent total tract digestibility (aTTd) among the three diets, but milk fat content increased with increasing forage proportion, even though the similar neutral detergent fiber of all diets. Nitrogen use efficiency was highest in the diet containing 600 g forage/kg DM, and some evidence was observed for a better profitability with this forage proportion. In experiment 2, feeding legumes increased DMI despite no effects on aTTd. Milk yield increased in line with DMI, with a larger increase for the fresh cowpea. Nitrogen use efficiency and milk composition were not affected by the diets. The increased MY and lower feed costs increased the economic benefits when feeding legumes, particularly when feeding fresh cowpea. Feeding fresh cowpea or jackbean silage to dairy cows appears to be an alternative to soybean as protein source, ideally at a forage proportions of 600 g/kg DM, without altering milk yield and quality and increasing the farm profitability.

Targeted depletion of PIK3R2 induces regression of lung squamous cell carcinoma

Oncogenic mutations in the PI3K/AKT pathway are present in nearly half of human tumors. Nonetheless, inhibitory compounds of the pathway often induce pathway rebound and tumor resistance. We find that lung squamous cell carcinoma (SQCC), which accounts for ~20% of lung cancer, exhibits increased expression of the PI3K subunit PIK3R2, which is at low expression levels in normal tissues. We tested a new approach to interfere with PI3K/AKT pathway activation in lung SQCC. We generated tumor xenografts of SQCC cell lines and examined the consequences of targeting PIK3R2 expression. In tumors with high PIK3R2 expression, and independently of PIK3CA, KRAS, or PTEN mutations, PIK3R2 depletion induced lung SQCC xenograft regression without triggering PI3K/AKT pathway rebound. These results validate the use PIK3R2 interfering tools for the treatment of lung squamous cell carcinoma.

Low-dose statin treatment increases prostate cancer aggressiveness

Prostate cancer is diagnosed late in life, when co-morbidities are frequent. Among them, hypertension, hypercholesterolemia, diabetes or metabolic syndrome exhibit an elevated incidence. In turn, prostate cancer patients frequently undergo chronic pharmacological treatments that could alter disease initiation, progression and therapy response. Here we show that treatment with anti-cholesterolemic drugs, statins, at doses achieved in patients, enhance the pro-tumorigenic activity of obesogenic diets. In addition, the use of a mouse model of prostate cancer and human prostate cancer xenografts revealed that in vivo simvastatin administration alone increases prostate cancer aggressiveness. In vitro cell line systems supported the notion that this phenomenon occurs, at least in part, through the direct action on cancer cells of low doses of statins, in range of what is observed in human plasma. In sum, our results reveal a prostate cancer experimental system where statins exhibit an undesirable effect, and warrant further research to address the relevance and implications of this observation in human prostate cancer.

A genetic interaction between RAP1 and telomerase reveals an unanticipated role for RAP1 in telomere maintenance

RAP1 is one of the components of shelterin, the capping complex at chromosome ends or telomeres, although its role in telomere length maintenance and protection has remained elusive. RAP1 also binds subtelomeric repeats and along chromosome arms, where it regulates gene expression and has been shown to function in metabolism control. Telomerase is the enzyme that elongates telomeres, and its deficiency causes a premature aging in humans and mice. We describe an unanticipated genetic interaction between RAP1 and telomerase. While RAP1 deficiency alone does not impact on mouse survival, mice lacking both RAP1 and telomerase show a progressively decreased survival with increasing mouse generations compared to telomerase single mutants. Telomere shortening is more pronounced in Rap1^−/−Terc^−/− doubly deficient mice than in the single‐mutant Terc^−/− counterparts, leading to an earlier onset of telomere‐induced DNA damage and degenerative pathologies. Telomerase deficiency abolishes obesity and liver steatohepatitis provoked by RAP1 deficiency. Using genomewide ChIP sequencing, we find that progressive telomere shortening owing to telomerase deficiency leads to re‐localization of RAP1 from telomeres and subtelomeric regions to extratelomeric sites in a genomewide manner. These findings suggest that although in the presence of sufficient telomere reserve RAP1 is not a key factor for telomere maintenance and protection, it plays a crucial role in the context of telomerase deficiency, thus in agreement with its evolutionary conservation as a telomere component from yeast to humans.

Hoxa-10 and Cyclin D3 Overexpression in the Decidual Reaction in a Superovulation Protocol in Young Adult C57BL/6J Mice

Following the performance of a superovulation protocol, multiple nodules were observed bilaterally in the uterine horns of 31 of 276 (11.2%) C57BL/6 J female mice aged 8.5 ± 0.6 (mean and standard error of mean) weeks. These lesions prevented embryo collection, and the uterine decidual reaction was suspected. Samples of pathological uteri (n = 20) and the normal genital tracts of donors treated with a similar superovulation protocol (control group, n = 10) were collected. Immunohistochemistry was performed to evaluate pancytokeratin, desmin, vimentin, progesterone receptor (PR), estrogen receptor α (ERα), Ki-67, cyclin D3 and c-Myc expression, as well as quantitative polymerase chain reaction to assess cyclin D3, Hoxa-10 and heparin-binding epidermal growth factor-like growth factor (HB-EGF) mRNA expression. The uterine decidual reaction presented a high degree of structural organization and specifically affected the antimesometrial region of the endometrium. The abnormal decidual cells were large polygonal cells that were frequently polyploid or binucleated and strongly positive for desmin. Immunohistochemistry showed higher Ki-67 proliferation index and higher expression of PR and cyclin D3 in decidual cells in the antimesometrial aspect of the endometrium, compared to nondecidualized endometrial stromal cells in the mesometrial aspect of affected uteri, and compared to endometrial stromal cells in healthy uteri. High expression of cyclin D3 and Hoxa-10 mRNA was also observed in uteri affected by the decidual reaction. These results suggest that PR overexpression in endometrial stromal cells, likely due to high progesterone levels, triggers cyclin D3 and Hoxa-10 overexpression, which may be involved in the pathological mechanisms of the mouse uterine decidual reaction.

Disseminated histoplasmosis and AIDS: a prospective and multicentre study to evaluate the performance of different diagnostic tests

The burden of histoplasmosis has been poorly documented in most of the endemic areas for the disease, including Brazil. Also, modern non-culture-based diagnostic tests are often non-available in these regions. This was a prospective cohort study in HIV-infected patients with suspected disseminated disease evaluated with different diagnostic tests. Patients were enrolled in three referral medical centres in Porto Alegre, Brazil. Among 78 evaluated patients, disseminated histoplasmosis was confirmed in eight individuals (10.3%) by the means of classical (culture/histopathology) tests. Antigen detection in the urine was found to be more sensitive: IMMY^® ALPHA ELISA detected 13 positive cases (16.7%) and the in-house ELISA test developed by the Centers for Disease Prevention and Control (CDC) detected 14 (17.9%). IMMY^® and CDC tests provided concordant results in 96.2% of cases. This is the first study to compare the performance of the in-house CDC ELISA test with the IMMY^® commercial test for the diagnosis of histoplasmosis, and a high degree of concordance was observed. The study revealed that H. capsulatum is an important agent of disseminated disease in AIDS patients in Brazil, reinforcing the importance of making available modern diagnostic tests as well as safer antifungal agents for the treatment of histoplasmosis.

Therapeutic inhibition of TRF1 impairs the growth of p53-deficient K-RasG12V-induced lung cancer by induction of telomeric DNA damage

Telomeres are considered anti-cancer targets, as telomere maintenance above a minimum length is necessary for cancer growth. Telomerase abrogation in cancer-prone mouse models, however, only decreased tumor growth after several mouse generations when telomeres reach a critically short length, and this effect was lost upon p53 mutation. Here, we address whether induction of telomere uncapping by inhibition of the TRF1 shelterin protein can effectively block cancer growth independently of telomere length. We show that genetic Trf1 ablation impairs the growth of p53-null K-Ras^G12V-induced lung carcinomas and increases mouse survival independently of telomere length. This is accompanied by induction of telomeric DNA damage, apoptosis, decreased proliferation, and G2 arrest. Long-term whole-body Trf1 deletion in adult mice did not impact on mouse survival and viability, although some mice showed a moderately decreased cellularity in bone marrow and blood. Importantly, inhibition of TRF1 binding to telomeres by small molecules blocks the growth of already established lung carcinomas without affecting mouse survival or tissue function. Thus, induction of acute telomere uncapping emerges as a potential new therapeutic target for lung cancer.

G6PD protects from oxidative damage and improves healthspan in mice

Reactive oxygen species (ROS) are constantly generated by cells and ROS-derived damage contributes to ageing. Protection against oxidative damage largely relies on the reductive power of NAPDH, whose levels are mostly determined by the enzyme glucose-6-phosphate dehydrogenase (G6PD). Here, we report a transgenic mouse model with moderate overexpression of human G6PD under its endogenous promoter. Importantly, G6PD-Tg mice have higher levels of NADPH, lower levels of ROS-derived damage, and better protection from ageing-associated functional decline, including extended median lifespan in females. The G6PD transgene has no effect on tumour development, even after combining with various tumour-prone genetic alterations. We conclude that a modest increase in G6PD activity is beneficial for healthspan through increased NADPH levels and protection from the deleterious effects of ROS.

The enzyme G6PD generates the reductive metabolite NADPH, which has antioxidant effects, but has also been linked to tumour growth. Here the authors generate mice that modestly overexpress G6PD and report increased lifespan in females, and no negative effects on tumour formation in various genetic models.

Growth Arrest Specific 1 (Gas1) Gene Overexpression in Liver Reduces the In Vivo Progression of Murine Hepatocellular Carcinoma and Partially Restores Gene Expression Levels

The prognosis of hepatocellular carcinoma patients is usually poor, the size of tumors being a limiting factor for surgical treatments. Present results suggest that the overexpression of Gas1 (growth arrest specific 1) gene reduces the size, proliferating activity and malignancy of liver tumors. Mice developing diethylnitrosamine-induced hepatocellular carcinoma were subjected to hydrodynamic gene delivery to overexpress Gas1 in liver. This treatment significantly (p < 0.05) reduced the number of large tumors, while the difference in the total number of lesions was not significant. Moreover, the number of carcinoma foci in the liver and the number of lung metastases were reduced. These results are related with the finding that overexpression of Gas1 in Hepa 1-6 cells arrests cell cycle before S phase, with a significant (p < 0.01) and concomitant reduction in the expression of cyclin E2 gene. In addition, a triangular analysis of microarray data shows that Gas1 overexpression restores the transcription levels of 150 genes whose expression was affected in the diethylnitrosamine-induced tumors, thirteen of which are involved in the hedgehog signaling pathway. Since the in vivo Gas1 gene delivery to livers of mice carrying hepatocellular carcinoma reduces the size and proliferating activity of tumors, partially restoring the transcriptional profile of the liver, the present study opens promising insights towards a therapeutic approach for hepatocellular carcinoma.

Mice with Pulmonary Fibrosis Driven by Telomere Dysfunction

Idiopathic pulmonary fibrosis (IPF) is a degenerative disease of the lungs with an average survival post-diagnosis of 2-3 years. New therapeutic targets and treatments are necessary. Mutations in components of the telomere-maintenance enzyme telomerase or in proteins important for telomere protection are found in both familial and sporadic IPF cases. However, the lack of mouse models that faithfully recapitulate the human disease has hampered new advances. Here, we generate two independent mouse models that develop IPF owing to either critically short telomeres (telomerase-deficient mice) or severe telomere dysfunction in the absence of telomere shortening (mice with Trf1 deletion in type II alveolar cells). We show that both mouse models develop pulmonary fibrosis through induction of telomere damage, thus providing proof of principle of the causal role of DNA damage stemming from dysfunctional telomeres in IPF development and identifying telomeres as promising targets for new treatments.

TRIB3 suppresses tumorigenesis by controlling mTORC2/AKT/FOXO signaling

In a recent article, we found that Tribbles pseudokinase 3 (TRIB3) plays a tumor suppressor role and that this effect relies on the dysregulation of the phosphorylation of v-akt murine thymoma viral oncogene homolog (AKT) by the mammalian target of rapamycin complex 2 (mTORC2 complex), and the subsequent hyperphosphorylation and inactivation of the transcription factor Forkhead box O3 (FOXO3).

Role of cannabinoid receptor CB2 in HER2 pro-oncogenic signaling in breast cancer

BACKGROUND

Pharmacological activation of cannabinoid receptors elicits antitumoral responses in different cancer models. However, the biological role of these receptors in tumor physio-pathology is still unknown.

METHODS

We analyzed CB2 cannabinoid receptor protein expression in two series of 166 and 483 breast tumor samples operated in the University Hospitals of Kiel, Tübingen, and Freiburg between 1997 and 2010 and CB2 mRNA expression in previously published DNA microarray datasets. The role of CB2 in oncogenesis was studied by generating a mouse line that expresses the human V-Erb-B2 Avian Erythroblastic Leukemia Viral Oncogene Homolog 2 (HER2) rat ortholog (neu) and lacks CB2 and by a variety of biochemical and cell biology approaches in human breast cancer cells in culture and in vivo, upon modulation of CB2 expression by si/shRNAs and overexpression plasmids. CB2-HER2 molecular interaction was studied by colocalization, coimmunoprecipitation, and proximity ligation assays. Statistical tests were two-sided.

RESULTS

We show an association between elevated CB2 expression in HER2+ breast tumors and poor patient prognosis (decreased overall survival, hazard ratio [HR] = 0.29, 95% confidence interval [CI] = 0.09 to 0.71, P = .009) and higher probability to suffer local recurrence (HR = 0.09, 95% CI = 0.049 to 0.54, P = .003) and to develop distant metastases (HR = 0.33, 95% CI = 0.13 to 0.75, P = .009). We also demonstrate that genetic inactivation of CB2 impairs tumor generation and progression in MMTV-neu mice. Moreover, we show that HER2 upregulates CB2 expression by activating the transcription factor ELK1 via the ERK cascade and that an increased CB2 expression activates the HER2 pro-oncogenic signaling at the level of the tyrosine kinase c-SRC. Finally, we show HER2 and CB2 form heteromers in cancer cells.

CONCLUSIONS

Our findings reveal an unprecedented role of CB2 as a pivotal regulator of HER2 pro-oncogenic signaling in breast cancer, and they suggest that CB2 may be a biomarker with prognostic value in these tumors.

Distinct p21 requirements for regulating normal and self-reactive T cells through IFN-γ production

Self/non-self discrimination characterizes immunity and allows responses against pathogens but not self-antigens. Understanding the principles that govern this process is essential for designing autoimmunity treatments. p21 is thought to attenuate autoreactivity by limiting T cell expansion. Here, we provide direct evidence for a p21 role in controlling autoimmune T cell autoreactivity without affecting normal T cell responses. We studied C57BL/6, C57BL/6/lpr and MRL/lpr mice overexpressing p21 in T cells, and showed reduced autoreactivity and lymphadenopathy in C57BL/6/lpr, and reduced mortality in MRL/lpr mice. p21 inhibited effector/memory CD4(+) CD8(+) and CD4(-)CD8(-) lpr T cell accumulation without altering defective lpr apoptosis. This was mediated by a previously non-described p21 function in limiting T cell overactivation and overproduction of IFN-γ, a key lupus cytokine. p21 did not affect normal T cell responses, revealing differential p21 requirements for autoreactive and normal T cell activity regulation. The underlying concept of these findings suggests potential treatments for lupus and autoimmune lymphoproliferative syndrome, without compromising normal immunity.

In vivo role of checkpoint kinase 2 in signaling telomere dysfunction

Checkpoint kinase 2 (CHK2) is a downstream effector of the DNA damage response (DDR). Dysfunctional telomeres, either owing to critical shortening or disruption of the shelterin complex, activate a DDR, which eventually results in cell cycle arrest, senescence and/or apoptosis. Successive generations of telomerase-deficient (Terc) mice show accelerated aging and shorter lifespan due to tissue atrophy and impaired organ regeneration associated to progressive telomere shortening. In contrast, mice deficient for the shelterin component TRF1 in stratified epithelia show a rapid and massive induction of DDR, leading to perinatal lethality and severe skin defects. In both mouse models, p53 deficiency can rescue survival. Here, we set to address the role of CHK2 in signaling telomere dysfunction in both mouse models. To this end, we generated mice doubly deficient for Chk2 and either Terc (Chk2^−/−Terc^−/−) or Trf1 (Trf1^Δ/ΔK5Cre Chk2^−/−). We show that Chk2 deletion improves Terc-associated phenotypes, including lifespan and age-associated pathologies. Similarly, Chk2 deficiency partially rescues perinatal mortality and attenuates degenerative pathologies of Trf1^Δ/ΔK5Cre mice. In both cases, we show that the effects are mediated by a significant attenuation of p53/p21 signaling pathway. Our results represent the first demonstration of a role for CHK2 in the in vivo signaling of dysfunctional telomeres.

Essential role for the TRF2 telomere protein in adult skin homeostasis

TRF2 is a component of shelterin, the protein complex that protects the ends of mammalian chromosomes. TRF2 is essential for telomere capping owing to its roles in suppressing an ATM-dependent DNA damage response (DDR) at chromosome ends and inhibiting end-to-end chromosome fusions. Mice deficient for TRF2 are early embryonic lethal. However, the role of TRF2 in later stages of development and in the adult organism remains largely unaddressed, with the exception of liver, where TRF2 was found to be dispensable for maintaining tissue function. Here, we study the impact of TRF2 conditional deletion in stratified epithelia by generating the TRF2^∆/∆-K5-Cre mouse model, which targets TRF2 deletion to the skin from embryonic day E11.5. In marked contrast to TRF2 deletion in the liver, TRF2^∆/∆-K5-Cre mice show lethality in utero reaching 100% lethality perinataly. At the molecular and cellular level, TRF2 deletion provokes induction of an acute DDR at telomeres, leading to activation of p53 signaling pathways and to programed cell death since the time of Cre expression at E11.5. Unexpectedly, neither inhibition of the NHEJ pathway by abrogation of 53BP1 nor inhibition of DDR by p53 deficiency rescued these severe phenotypes. Instead, TRF2 deletion provokes an extensive epidermal cell death accompanied by severe inflammation already at E16.5 embryos, which are independent of p53. These results are in contrast with conditional deletion of TRF1 and TPP1 in the skin, where p53 deficiency rescued the associated skin phenotypes, highlighting the comparatively more essential role of TRF2 in skin homeostasis.

Exposure to the endocrine disruptor di(2-ethylhexyl)phthalate affects female reproductive features by altering pulsatile LH secretion

The patterns of growth of preovulatory follicles and corpora lutea, as well as plasma concentrations of estradiol, progesterone and LH were evaluated in sheep exposed to DEHP. There were not found effects on the preovulatory follicular dynamics nor on the ovulatory efficiency between DEHP-exposed and control sheep. However, plasma estradiol concentration was significantly higher in the ewes exposed to DEHP than in the control females (P<0.001). Afterwards, DEHP-exposed ewes had significantly higher plasma progesterone concentration from Day 2 of the luteal phase (P<0.05), although there were no differences between groups in the macro- and microscopic features of the corpora lutea. Analysis of mean basal concentrations of LH showed lower values in DEHP-exposed than in control sheep (0.3 ± 01 ng/mL vs. 0.7 ± 0.1; P<0.05). Moreover, the frequency of LH pulses was 0.3 pulses/4 h, with amplitude of 0.6 ng/mL, in the control group; on the other hand, the pulsatile secretion of LH in the DEHP-exposed group was undetectable during the period of sampling.

Cooperative role between p21cip1/waf1 and p27kip1 in premature senescence in glandular proliferative lesions in mice

Cellular senescence has been considered a novel target for cancer therapy. It has also been pointed out that p21(cip1/waf1) and p27(kip1) cyclin-dependent kinase inhibitors (CKIs) play a role in cellular senescence in some tumor types. Therefore, in order to address the possibility of a cooperative role between p21 and p27 proteins in senescence in vivo we analyzed cellular senescence in spontaneous glandular proliferative lesions (adrenal, thyroid and pituitary glands) in a double-KO mice model, using γH2AX, p53, p16, PTEN and Ki67 as senescence markers. The results obtained showed that p21p27 double-null mice had the lowest number of γH2AX positive cells in glandular hyperplasias and benign tumors. Also, in this group, Ki67 proliferation index correlated with a lower immunohistochemical expression of γH2AX and p53. The expression of p16 and PTEN do not seem to cause synergism of senescence in the benign lesions analyzed in p21p27 double-KO mice. These observations suggest an intrinsic cooperation between p21 and p27 CKIs in the activation of stress-induced cellular senescence and tumor progression in vivo, which would be a physiological mechanism to prevent tumor cell proliferation.

Different influence of ovine estrus synchronization treatments on caruncular early angiogenesis

The present study compares two protocols for ovine estrus synchronization by assessing the caruncular angiogenic response to the establishment of pregnancy. The analysis consisted of the immunohistochemical evaluation of Vascular Endothelial Growth Factor (VEGF), Platelet Endothelial Cell Adhesion Molecule-1 (PECAM-1, CD31) and Von Willebrand Factor (vWF) in ovine caruncular stroma. A flock of thirty-eight adult ewes was divided in two groups and synchronized with either progestagens (Group P) or prostaglandin analogues (Group PG). Immunohistochemistry was performed in uterine samples obtained from pregnant ewes (P, n=15; PG, n=13) on days 15 post coitus (pc), 17pc and 21pc (day 0 =day of estrus). Each factor was assessed by total vascular density (TVD, total positive blood vessels/mm2), capillary vascular density (CVD, positive blood capillaries/mm2) and arteriolar vascular density (AVD, positive arterioles/mm2). Group P demonstrated higher VEGF-CVD (P=0.045) when compared to prostaglandin treated animals. Vascular CD31-expression decreased on days 15pc and 21pc (TVD, P=0.007 and CVD, P=0.014) in both groups. vWF analysis did not show significant differences between groups or days of study. These results demonstrate a different influence of progestagen-based and prostaglandin analogues-based synchronization treatments over VEGF vascular expression during caruncular development taking place in response to pregnancy establishment. In addition, observations pointed out in this study support the involvement of CD31 in the angiogenic stimulus that occurs during early maternal placentation in the ewe.

RAP1 protects from obesity through its extratelomeric role regulating gene expression

RAP1 is part of shelterin, the protective complex at telomeres. RAP1 also binds along chromosome arms, where it is proposed to regulate gene expression. To investigate the nontelomeric roles of RAP1 in vivo, we generated a RAP1 whole-body knockout mouse. These mice show early onset of obesity, which is more severe in females than in males. Rap1-deficient mice show accumulation of abdominal fat, hepatic steatosis, and high-fasting plasma levels of insulin, glucose, cholesterol, and alanine aminotransferase. Gene expression analyses of liver and visceral white fat from Rap1-deficient mice before the onset of obesity show deregulation of metabolic programs, including fatty acid, glucose metabolism, and PPARα signaling. We identify Pparα and Pgc1α as key factors affected by Rap1 deletion in the liver. We show that RAP1 binds to Pparα and Pgc1α loci and modulates their transcription. These findings reveal a role for a telomere-binding protein in the regulation of metabolism.

Telomerase reverse transcriptase synergizes with calorie restriction to increase health span and extend mouse longevity

Caloric restriction (CR), a reduction of food intake while avoiding malnutrition, can delay the onset of cancer and age-related diseases in several species, including mice. In addition, depending of the genetic background, CR can also increase or decrease mouse longevity. This has highlighted the importance of identifying the molecular pathways that interplay with CR in modulating longevity. Significant lifespan extension in mice has been recently achieved through over-expression of the catalytic subunit of mouse telomerase (mTERT) in a cancer protective background. Given the CR cancer-protective effects in rodents, we set to address here whether CR impacts on telomere length and synergizes with mTERT to extend mouse longevity. CR significantly decreased tumor incidence in TERT transgenic (TgTERT) mice and extended their lifespan compared to wild-type (WT) controls under the same diet, indicating a synergy between TgTERT and CR in increasing mouse longevity. In addition, longitudinal telomere length measurements in peripheral blood leukocytes from individual mice showed that CR resulted in maintenance and/or elongation telomeres in a percentage of WT mice, a situation that mimics telomere dynamics in TgTERT cohorts. These results demonstrate that CR attenuates telomere erosion associated to aging and that synergizes with TERT over-expression in increasing "health span" and extending mouse longevity.

The rate of increase of short telomeres predicts longevity in mammals

Aberrantly short telomeres result in decreased longevity in both humans and mice with defective telomere maintenance. Normal populations of humans and mice present high interindividual variation in telomere length, but it is unknown whether this is associated with their lifespan potential. To address this issue, we performed a longitudinal telomere length study along the lifespan of wild-type and transgenic telomerase reverse transcriptase mice. We found that mouse telomeres shorten ∼100 times faster than human telomeres. Importantly, the rate of increase in the percentage of short telomeres, rather than the rate of telomere shortening per month, was a significant predictor of lifespan in both mouse cohorts, and those individuals who showed a higher rate of increase in the percentage of short telomeres were also the ones with a shorter lifespan. These findings demonstrate that short telomeres have a direct impact on longevity in mammals, and they highlight the importance of performing longitudinal telomere studies to predict longevity.

53BP1 deficiency combined with telomere dysfunction activates ATR-dependent DNA damage response

Loss of the telomere component TRF1 and the DNA repair mediator 53BP1 enhances the ATR-mediated DNA damage response, promotes the homology-directed repair of dysfunctional telomeres, and exacerbates DNA damage.

TRF1 protects mammalian telomeres from fusion and fragility. Depletion of TRF1 leads to telomere fusions as well as accumulation of γ-H2AX foci and activation of both the ataxia telangiectasia mutated (ATM)– and the ataxia telangiectasia and Rad3 related (ATR)–mediated deoxyribonucleic acid (DNA) damage response (DDR) pathways. 53BP1, which is also present at dysfunctional telomeres, is a target of ATM that accumulates at DNA double-strand breaks and favors nonhomologous end-joining (NHEJ) repair over ATM-dependent resection and homology-directed repair (homologous recombination [HR]). To address the role of 53BP1 at dysfunctional telomeres, we generated mice lacking TRF1 and 53BP1. 53BP1 deficiency significantly rescued telomere fusions in mouse embryonic fibroblasts (MEFs) lacking TRF1, but they showed evidence of a switch from the NHEJ- to HR-mediated repair of uncapped telomeres. Concomitantly, double-mutant MEFs showed evidence of hyperactivation of the ATR-dependent DDR. In intact mice, combined 53BP1/TRF1 deficiency in stratified epithelia resulted in earlier onset of DNA damage and increased CHK1 phosphorylation during embryonic development, leading to aggravation of skin phenotypes.

NOD1 activation induces cardiac dysfunction and modulates cardiac fibrosis and cardiomyocyte apoptosis

The innate immune system is responsible for the initial response of an organism to potentially harmful stressors, pathogens or tissue injury, and accordingly plays an essential role in the pathogenesis of many inflammatory processes, including some cardiovascular diseases. Toll like receptors (TLR) and nucleotide-binding oligomerization domain-like receptors (NLRs) are pattern recognition receptors that play an important role in the induction of innate immune and inflammatory responses. There is a line of evidence supporting that activation of TLRs contributes to the development and progression of cardiovascular diseases but less is known regarding the role of NLRs. Here we demonstrate the presence of the NLR member NOD1 (nucleotide-binding oligomerization domain containing 1) in the murine heart. Activation of NOD1 with the specific agonist C12-iEDAP, but not with the inactive analogue iE-Lys, induces a time- and dose-dependent cardiac dysfunction that occurs concomitantly with cardiac fibrosis and apoptosis. The administration of iEDAP promotes the activation of the NF-κB and TGF-β pathways and induces apoptosis in whole hearts. At the cellular level, both native cardiomyocytes and cardiac fibroblasts expressed NOD1. The NLR activation in cardiomyocytes was associated with NF-κB activation and induction of apoptosis. NOD1 stimulation in fibroblasts was linked to NF-κB activation and to increased expression of pro-fibrotic mediators. The down-regulation of NOD1 by specific siRNAs blunted the effect of iEDAP on the pro-fibrotic TGF-β pathway and cell apoptosis. In conclusion, our report uncovers a new pro-inflammatory target that is expressed in the heart, NOD1. The specific activation of this NLR induces cardiac dysfunction and modulates cardiac fibrosis and cardiomyocyte apoptosis, pathological processes involved in several cardiac diseases such as heart failure.

Endometrial expression of IFNAR-1 and oxytocin receptor (OTR) is not improved by prostaglandin analogues when compared to progestagens in ewes

The objective of this study was to investigate differences on the endometrial immunoexpression of type I IFN receptor subunit 1 (IFNAR1) and oxytocin receptor (OTR) during the time of maternal recognition of pregnancy in sheep, when oestrus is synchronized with either prostaglandin analogues (group PG) or conventional progestagens (group P). Plasma progesterone was measured from day 0 to 21 post-coitus (pc) (day 0 = day of oestrus). Immunohistochemistry was performed in samples of uterine horns from pregnant sheep on days 9pc, 13pc, 15pc, 17pc and 21pc to locate IFNAR1 and OTR expression in different endometrial compartments. Mean levels of plasma progesterone were different between treatments, obtaining higher levels in the PG group than in the P group (p < 0.05). Comparing days of pregnancy, IFNAR1 protein expression was different in the luminal epithelium (LE) (p < 0.05), while OTR was different in the LE and in the superficial glandular epithelium (SG) (p < 0.05). Temporal variation on the expression of both proteins from day 9pc to 21pc has been evidenced. IFNAR1 and OTR expression did not show significant differences between treatments. However, the response observed in the endometrium was highly inconsistent when prostaglandin analogues were used. Therefore, the protocol based on prostaglandin analogues still needs to be optimized before being considered as a better alternative to progestagens for oestrous synchronization in sheep.

Deleterious effects of progestagen treatment in VEGF expression in corpora lutea of pregnant ewes

The aim of the current study was to determine the possible effects of progestagen oestrous synchronization on vascular endothelial growth factor (VEGF) expression during sheep luteogenesis and the peri-implantation period and the relationship with luteal function. At days 9, 11, 13, 15, 17 and 21 of pregnancy, the ovaries from 30 progestagen treated and 30 ewes cycling after cloprostenol injection were evaluated by ultrasonography and, thereafter, collected and processed for immunohistochemical evaluation of VEGF; blood samples were drawn for evaluating plasma progesterone. The progestagen-treated group showed smaller corpora lutea than cloprostenol-treated and lower progesterone secretion. The expression of VEGF in the luteal cells increased with time in the cloprostenol group, but not in the progestagen-treated group, which even showed a decrease between days 11 and 13. In progestagen-treated sheep, VEGF expression in granulosa-derived parenchymal lobule capillaries was correlated with the size of the luteal tissue, larger corpora lutea had higher expression, and tended to have a higher progesterone secretion. In conclusion, the current study indicates the existence of deleterious effects from exogenous progestagen treatments on progesterone secretion from induced corpora lutea, which correlate with alterations in the expression of VEGF in the luteal tissue and, this, presumably in the processes of neoangiogenesis and luteogenesis.

Cannabinoids reduce ErbB2-driven breast cancer progression through Akt inhibition

Background

ErbB2-positive breast cancer is characterized by highly aggressive phenotypes and reduced responsiveness to standard therapies. Although specific ErbB2-targeted therapies have been designed, only a small percentage of patients respond to these treatments and most of them eventually relapse. The existence of this population of particularly aggressive and non-responding or relapsing patients urges the search for novel therapies. The purpose of this study was to determine whether cannabinoids might constitute a new therapeutic tool for the treatment of ErbB2-positive breast tumors. We analyzed their antitumor potential in a well established and clinically relevant model of ErbB2-driven metastatic breast cancer: the MMTV-neu mouse. We also analyzed the expression of cannabinoid targets in a series of 87 human breast tumors.

Results

Our results show that both Δ⁹-tetrahydrocannabinol, the most abundant and potent cannabinoid in marijuana, and JWH-133, a non-psychotropic CB₂ receptor-selective agonist, reduce tumor growth, tumor number, and the amount/severity of lung metastases in MMTV-neu mice. Histological analyses of the tumors revealed that cannabinoids inhibit cancer cell proliferation, induce cancer cell apoptosis, and impair tumor angiogenesis. Cannabinoid antitumoral action relies, at least partially, on the inhibition of the pro-tumorigenic Akt pathway. We also found that 91% of ErbB2-positive tumors express the non-psychotropic cannabinoid receptor CB₂.

Conclusions

Taken together, these results provide a strong preclinical evidence for the use of cannabinoid-based therapies for the management of ErbB2-positive breast cancer.

TPP1 is required for TERT recruitment, telomere elongation during nuclear reprogramming, and normal skin development in mice

The TPP1/ACD protein (hereafter TPP1) is a component of the shelterin complex at mammalian telomeres. Here we find that Tpp1-deficient mouse embryonic fibroblasts (MEFs) show increased chromosomal instability including sister chromatid fusions and chromosomes with multitelomeric signals related to telomere fragility. Tpp1 deletion decreases both TERT (the telomerase catalytic subunit) binding to telomeres in MEFs and telomerase function at chromosome ends in vivo. Abrogation of Tpp1 abolished net telomere elongation in the context of nuclear reprogramming of MEFs into induced pluripotent stem cells, whereas Tpp1 deletion in stratified epithelia of Tpp1(Delta/Delta)K5-Cre mice resulted in perinatal death, severe skin hyperpigmentation, and impaired hair follicle morphogenesis. p53 deficiency rescues skin hyperpigmentation and hair growth in these mice, indicating that p53 restricts proliferation of Tpp1-deficient cells. These results suggest a telomere-capping model where TPP1 protects telomere integrity and regulates telomerase recruitment to telomeres, thereby preventing early occurrence of degenerative pathologies.

Phosphatidylinositol 3-kinase gamma inhibition ameliorates inflammation and tumor growth in a model of colitis-associated cancer

BACKGROUND & AIMS

A large body of evidence supports a correlation between inflammation and cancer, although the molecular mechanisms that govern this process are incompletely understood. Phosphatidylinositol 3-kinase (PI3K) is an enzyme that regulates the immune response and contributes to cell transformation in several tumor types. Here, we address the role of the PI3Kgamma isoform in inflammatory bowel disease and in the development of colitis-associated cancer.

METHODS

PI3Kgamma(-/-) and control mice were repeatedly treated with dextran sulfate sodium to induce chronic colitis and colitis-associated cancer. Colorectal tumor burden and colon inflammation were evaluated in these mice. Leukocyte populations in colon were characterized by flow cytometry analysis.

RESULTS

PI3Kgamma-deficient mice had a lower incidence of colitis-associated tumors, as well as reduced tumor multiplicity and smaller tumor size compared with controls. Reduced tumor development paralleled less colon inflammation in PI3Kgamma-deficient mice. Analysis of leukocyte populations in the colon of PI3Kgamma-deficient mice showed defective activation and infiltration of myeloid cells and defective recruitment of T cells to the colon compared with controls.

CONCLUSIONS

PI3Kgamma regulates the innate immune response in a murine model of ulcerative colitis, thereby controlling colon inflammation and tumor formation.

Substantiation of ovarian effects of leptin by challenging a mouse model of obesity/type 2 diabetes

The goal of the current was to elucidate if treatment with gonadotrophins and leptin can circumvent infertility in obese mice and to establish whether reproductive effects of leptin are influenced at the hypothalamus-hypophysis or ovarian level by using a leptin deficient mouse model of obesity/type 2 diabetes (ob/ob) treated with leptin. The ovulatory response and the fertilization success were compared with the results obtained in ob/ob dams pretreated with a gonadotrophin-replacement therapy or in two groups (ob/ob and wild-type) of control non-pretreated females. The number of corpora lutea was significantly lower in control ob/ob mice than in wild-type dams. Treatment with gonadotrophin-replacement therapy did not increase significantly the ovulation rate in ob/ob, but the administration of leptin-replacement treatment allowed the authors to obtain a number of corpora lutea and oocytes/zygotes similar to those obtained in wild-type females. Furthermore, the leptin supply succeeded in producing fertilized zygotes, although in a lower number than found in the wild-type control. Thus, the hypogonadotrophic state in obese mice may be circumvented by the administration of a gonadotrophin-replacement therapy combined with a protocol for controlled ovarian stimulation, but fertile ovulations are only obtained after applying leptin-replacement therapy. Current results strongly support the existence of direct local effects of leptin on the ovary.

Loss of poly(ADP-ribose) polymerase-2 leads to rapid development of spontaneous T-cell lymphomas in p53-deficient mice

Poly(ADP-ribose) polymerase-2 (Parp-2) belongs to a family of enzymes that catalyse poly(ADP-ribosyl)ation of proteins. Parp-2 deficiency in mice (Parp-2(-/-)) results in reduced thymic cellularity associated with increased apoptosis in thymocytes, defining Parp-2 as an important mediator of T-cell survival during thymopoiesis. To determine whether there is a link between Parp-2 and the p53 DNA-damage-dependent apoptotic response, we have generated Parp-2/p53-double-null mutant mice. We found that p53(-/-) backgrounds completely restored the survival and development of Parp-2(-/-) thymocytes. However, Parp-2-deficient thymocytes accumulated high levels of DNA double-strand breaks (DSB), independently of the p53 status, in line with a function of Parp-2 as a caretaker promoting genomic stability during thymocytes development. Although Parp-2(-/-) mice do not have spontaneous tumours, Parp-2 deficiency accelerated spontaneous tumour development in p53-null mice, mainly T-cell lymphomas. These data suggest a synergistic interaction between Parp-2 and p53 in tumour suppression through the role of Parp-2 in DNA-damage response and genome integrity surveillance, and point to the potential importance of examining human tumours for the status of both genes.

Normal proliferation and tumorigenesis but impaired pancreatic function in mice lacking the cell cycle regulator sei1

Sei1 is a positive regulator of proliferation that promotes the assembly of Cdk4-cyclin D complexes and enhances the transcriptional activity of E2f1. The potential oncogenic role of Sei1 is further suggested by its overexpression in various types of human cancers. To study the role of Sei1, we have generated a mouse line deficient for this gene. Sei1-null fibroblasts did not show abnormalities regarding proliferation or susceptibility to neoplastic transformation, nor did we observe defects on Cdk4 complexes or E2f activity. Sei1-null mice were viable, did not present overt pathologies, had a normal lifespan, and had a normal susceptibility to spontaneous and chemically-induced cancer. Pancreatic insulin-producing cells are known to be particularly sensitive to Cdk4-cyclin D and E2f activities, and we have observed that Sei1 is highly expressed in pancreatic islets compared to other tissues. Interestingly, Sei1-null mice present lower number of islets, decreased beta-cell area, impaired insulin secretion, and glucose intolerance. These defects were associated to nuclear accumulation of the cell-cycle inhibitors p21(Cip1) and p27(Kip1) in islet cells. We conclude that Sei1 plays an important role in pancreatic beta-cells, which supports a functional link between Sei1 and the core cell cycle regulators specifically in the context of the pancreas.

Telomere shortening relaxes X chromosome inactivation and forces global transcriptome alterations

Telomeres are heterochromatic structures at chromosome ends essential for chromosomal stability. Telomere shortening and the accumulation of dysfunctional telomeres are associated with organismal aging. Using telomerase-deficient TRF2-overexpressing mice (K5TRF2/Terc(-/-)) as a model for accelerated aging, we show that telomere shortening is paralleled by a gradual deregulation of the mammalian transcriptome leading to cumulative changes in a defined set of genes, including up-regulation of the mTOR and Akt survival pathways and down-regulation of cell cycle and DNA repair pathways. Increased DNA damage from dysfunctional telomeres leads to reduced deposition of H3K27me3 onto the inactive X chromosome (Xi), impaired association of the Xi with telomeric transcript accumulations (Tacs), and reactivation of an X chromosome-linked K5TRF2 transgene that is subjected to X-chromosome inactivation in female mice with sufficiently long telomeres. Exogenously induced DNA damage also disrupts Xi-Tacs, suggesting DNA damage at the origin of these alterations. Collectively, these findings suggest that critically short telomeres activate a persistent DNA damage response that alters gene expression programs in a nonstochastic manner toward cell cycle arrest and activation of survival pathways, as well as impacts the maintenance of epigenetic memory and nuclear organization, thereby contributing to organismal aging.

Increased telomere fragility and fusions resulting from TRF1 deficiency lead to degenerative pathologies and increased cancer in mice

The telomere repeat-binding factor 1 (TERF1, referred to hereafter as TRF1) is a component of mammalian telomeres whose role in telomere biology and disease has remained elusive. Here, we report on cells and mice conditionally deleted for TRF1. TRF1-deleted mouse embryonic fibroblasts (MEFs) show rapid induction of senescence, which is concomitant with abundant telomeric gamma-H2AX foci and activation of the ATM/ATR downstream checkpoint kinases CHK1 and CHK2. DNA damage foci are rescued by both ATM and ATM/ATR inhibitors, further indicating that both signaling pathways are activated upon TRF1 deletion. Abrogation of the p53 and RB pathways bypasses senescence but leads to chromosomal instability including sister chromatid fusions, chromosome concatenation, and occurrence of multitelomeric signals (MTS). MTS are also elevated in ATR-deficient MEFs or upon treatment with aphidicolin, two conditions known to induce breakage at fragile sites, suggesting that TRF1-depleted telomeres are prone to breakage. To address the impact of these molecular defects in the organism, we deleted TRF1 in stratified epithelia of TRF1(Delta/Delta)K5-Cre mice. These mice die perinatally and show skin hyperpigmentation and epithelial dysplasia, which are associated with induction of telomere-instigated DNA damage, activation of the p53/p21 and p16 pathways, and cell cycle arrest in vivo. p53 deficiency rescues mouse survival but leads to development of squamous cell carcinomas, demonstrating that TRF1 suppresses tumorigenesis. Together, these results demonstrate that dysfunction of a telomere-binding protein is sufficient to produce severe telomeric damage in the absence of telomere shortening, resulting in premature tissue degeneration and development of neoplastic lesions.

Anti-aging activity of the Ink4/Arf locus

The proteins encoded by the Ink4/Arf locus, p16Ink4a, p19Arf and p15Ink4b are major tumour suppressors that oppose aberrant mitogenic signals. The expression levels of the locus are progressively increased during aging and genome-wide association studies have linked the locus to a number of aging-associated diseases and frailty in humans. However, direct measurement of the global impact of the Ink4/Arf locus on organismal aging and longevity was lacking. In this work, we have examined the fertility, cancer susceptibility, aging and longevity of mice genetically modified to carry one (Ink4/Arf-tg) or two (Ink4/Arf-tg/tg) intact additional copies of the locus. First, increased gene dosage of Ink4/Arf impairs the production of male germ cells, and in the case of Ink4/Arf-tg/tg mice results in a Sertoli cell-only-like syndrome and a complete absence of sperm. Regarding cancer, there is a lower incidence of aging-associated cancer proportional to the Ink4/Arf gene dosage. Interestingly, increased Ink4/Arf gene dosage resulted in lower scores in aging markers and in extended median longevity. The increased survival was also observed in cancer-free mice indicating that cancer protection and delayed aging are separable activities of the Ink4/Arf locus. In contrast to these results, mice carrying one or two additional copies of the p53 gene (p53-tg and p53-tg/tg) had a normal longevity despite their increased cancer protection. We conclude that the Ink4/Arf locus has a global anti-aging effect, probably by favouring quiescence and preventing unnecessary proliferation.

MSH2 deficiency abolishes the anticancer and pro-aging activity of short telomeres

Mutations in the mismatch repair (MMR) pathway occur in human colorectal cancers with microsatellite instability. Mounting evidence suggests that cell-cycle arrest in response to a number of cellular stresses, including telomere shortening, is a potent anticancer barrier. The telomerase-deficient mouse model illustrates the anticancer effect of cell-cycle arrest provoked by short telomeres. Here, we describe a role for the MMR protein, MSH2, in signaling cell-cycle arrest in a p21/p53-dependent manner in response to short telomeres in the context of telomerasedeficient mice. In particular, progressively shorter telomeres at successive generations of MSH2(-/-) Terc(-/--) mice did not suppress cancer in these mice, indicating that MSH2 deficiency abolishes the tumor suppressor activity of short telomeres. Interestingly, MSH2 deficiency prevented degenerative pathologies in the gastrointestinal tract of MSH2(-/-) Terc(-/-) mice concomitant with a rescue of proliferative defects. The abolishment of the anticancer and pro-aging effects of short telomeres provoked by MSH2 abrogation was independent of changes in telomere length. These results highlight a role for MSH2 in the organismal response to dysfunctional telomeres, which in turn may be important in the pathobiology of human cancers bearing mutations in the MMR pathway.

Telomerase reverse transcriptase delays aging in cancer-resistant mice

Telomerase confers limitless proliferative potential to most human cells through its ability to elongate telomeres, the natural ends of chromosomes, which otherwise would undergo progressive attrition and eventually compromise cell viability. However, the role of telomerase in organismal aging has remained unaddressed, in part because of the cancer-promoting activity of telomerase. To circumvent this problem, we have constitutively expressed telomerase reverse transcriptase (TERT), one of the components of telomerase, in mice engineered to be cancer resistant by means of enhanced expression of the tumor suppressors p53, p16, and p19ARF. In this context, TERT overexpression improves the fitness of epithelial barriers, particularly the skin and the intestine, and produces a systemic delay in aging accompanied by extension of the median life span. These results demonstrate that constitutive expression of Tert provides antiaging activity in the context of a mammalian organism.

Disruption of the endothelial nitric oxide synthase gene affects ovulation, fertilization and early embryo survival in a knockout mouse model

Two consecutive experiments determined whether disruption of the endothelial nitric oxide synthases (NOS) gene (Nos3) affects ovulation, fertilization, implantation, and embryo development. In the first trial, Nos3-knockout mice (groups Nos3(-/-)) and wild-type mice (groups Nos3(+/+)) showed significant differences in mean number of corpora lutea (9.7+/-1.2 in Nos3(-/-) versus 14.2+/-1.2 in Nos3(+/+); P<0.01), rate of anovulation (48.3+/-7.3% in Nos3(-/-) versus 29.7+/-6.3 in Nos3(+/+); P<0.05), total mean number of recovered oocytes/zygotes (4.0+/-1.1 in Nos3(-/-) versus 10.4+/-1.6 in Nos3(+/+); P<0.01), and non-fertilization rate (50.7 in Nos3(-/-) versus 3.3% in Nos3(+/+); P<0.001). In the second trial, implantation and early pregnancy losses in Nos3-knockout and wild-type dams were detected by real-time ultrasound imaging. The number of embryos reaching implantation was higher in Nos3(+/+) than in Nos3(-/-) mice (7.5+/-0.4 vs 4.0+/-0.4; P<0.005); thereafter, embryo losses were detected between days 8.5 and 13.5, in 62.5% of the Nos3-knockout dams and, at days 10.5 and 11.5, in 16.7% of the control females (P<0.005). Thus, NO and NOS3 deficiencies affect reproductive and developmental features in the Nos3-knockout mouse model.

The signaling adaptor p62 is an important NF-kappaB mediator in tumorigenesis

The balance between cell death and survival, two critical aspects of oncogenic transformation, determines the outcome of tumorigenesis. Nuclear factor-kappaB (NF-kappaB) is a critical regulator of survival; it is induced by the oncogene Ras and, when inhibited, accounts for the cell death response of Ras-transformed cells. Here, we show that the signaling adaptor p62 is induced by Ras, its levels are increased in human tumors, and it is required for Ras-induced survival and transformation. p62-/- mice are resistant to Ras-induced lung adenocarcinomas. p62 is necessary for Ras to trigger IkappaB kinase (IKK) through the polyubiquitination of tumor necrosis factor (TNF) receptor-associated factor 6 (TRAF6), and its deficiency produces increased reactive oxygen species (ROS) levels, which account for the enhanced cell death and reduced tumorigenicity of Ras in the absence of p62.

SNAI1 is required for tumor growth and lymph node metastasis of human breast carcinoma MDA-MB-231 cells

The transcription factor, SNAI1 (Snail), has recently been proposed as an important mediator of tumor invasion because of its role in E-cadherin down-regulation and induction of epithelial-mesenchymal transition. In human breast cancer, the expression of SNAI1 and/or the homologous SNAI2 (Slug) has been associated with E-cadherin repression, local or distant metastasis, tumor recurrence, or poor prognosis in different tumor series. However, the specific contribution of either factor to breast tumor progression is still unclear. We have analyzed the role of SNAI1 in human breast cancer by loss of function studies and provide evidence of a major role for SNAI1 in both primary tumor growth and metastasis of human breast carcinoma MDA-MB-231 cells. Specific silencing of SNAI1 by short hairpin RNA induces a decrease in mesenchymal and proinvasive markers (MMP9, ID1, SPARC) in MDA-MB-231 cells, concomitant with reduced in vitro invasive behavior. More importantly, stable SNAI1 silencing in MDA-MB-231 cells leads to a dramatic reduction of in vivo tumor incidence and growth rate. Tumors induced by MDA-MB-231-SNAI1-silenced cells show extensive necrotic regions and a significant decrease in invasive and angiogenic markers. Moreover, SNAI1 silencing increases the sensitivity of MDA-MB-231 cells to chemotherapeutics relevant in breast cancer treatments, gemcitabine and docetaxel. Remarkably, analysis of cell lines derived from lymph node metastasis indicates that SNAI1 expression is required for metastatic dissemination.

Deficient mismatch repair improves organismal fitness and survival of mice with dysfunctional telomeres

Mismatch repair (MMR) has important roles in meiotic and mitotic recombination, DNA damage signaling, and various aspects of DNA metabolism including class-switch recombination, somatic hypermutation, and triplet-repeat expansion. Defects in MMR are responsible for human cancers characterized by microsatellite instability. Intriguingly, MMR deficiency has been shown to rescue survival and proliferation of telomerase-deficient yeast strains. A putative role for MMR at mammalian telomeres that could have an impact on cancer and aging is, however, unknown. Here, we studied the role of MMR in response to dysfunctional telomeres by generating mice doubly deficient for telomerase and the PMS2 MMR gene (Terc-/-/PMS2-/- mice). PMS2 deficiency prolonged the mean lifespan and median survival of telomerase-deficient mice concomitant with rescue of degenerative pathologies. This rescue of survival was independent of changes in telomere length, in sister telomere recombination, and in microsatellite instability. Importantly, PMS2 deficiency rescued cell proliferation defects but not apoptotic defects in vivo, concomitant with a decreased p21 induction in response to short telomeres. The proliferative advantage conferred to telomerase-deficient cells by the ablation of PMS2 did not produce increased tumors. Indeed, Terc-/-/PMS2-/- mice showed reduced tumors compared with PMS2-/- mice, in agreement with a tumor suppressor role for short telomeres in the context of MMR deficiencies. These results highlight an unprecedented role for MMR in mediating the cellular response to dysfunctional telomeres in vivo by attenuating p21 induction.

Increased p53 gene dosage reduces neointimal thickening induced by mechanical injury but has no effect on native atherosclerosis

OBJECTIVE

The tumor suppressor p53 regulates cell proliferation and apoptosis, two key processes in the pathogenesis of occlusive vascular disease. Here, we examined the consequences of heightening p53 function on neointimal lesion formation in the setting of atherosclerosis and mechanical injury.

METHODS

For this study we employed immunohistopathological characterization of neointimal lesions in atherosclerosis-prone apolipoprotein E-null mice with normal p53 gene dosage (apoE-KO) and carrying a p53 transgene (Super-p53/apoE-KO). We also carried out molecular studies in macrophages and smooth muscle cells (SMCs) obtained from these mice.

RESULTS

The p53 transgene conferred p53 gain-of-function in cultured cells and mice. In vitro, survival of irradiated Super-p53 macrophages and femoral SMCs was reduced, but only Super-p53 SMCs exhibited attenuated proliferation. In vivo, whereas the size of spontaneously formed and diet-induced aortic atheromas was indistinguishable in apoE-KO and Super-p53/apoE-KO mice, the latter exhibited attenuated neointimal thickening in mechanically injured femoral artery. In both models, neither apoptosis nor cell proliferation were affected by additional p53 gene dosage when examined in established neointimal lesions. However, at 2 days after mechanical injury when neointimal lesions were not yet formed, cell proliferation was significantly attenuated within medial SMCs of Super-p53/apoE-KO mice.

CONCLUSION

Heightening p53 function has differential effects on in vitro proliferation of macrophages (unaffected) versus SMCs (reduced), and on native atherosclerosis (unaffected) versus mechanically induced neointimal thickening (reduced) in apoE-KO mice. The protective effect of p53 in mechanically injured femoral artery coincided with limited medial SMC proliferation at early time points preceding neointima formation, but neither medial nor neointimal cell proliferation was affected in vessels with established occlusive lesions. These findings corroborate p53 gain-of-function as a promising therapeutic strategy to limit post-angioplasty restenosis but not native atherosclerosis.