Fatty acid synthase is a metabolic marker of cell proliferation rather than malignancy in ovarian cancer and its precursor cells

Ovarian cancer (OC) is caused by genetic aberrations in networks that control growth and survival. Importantly, aberrant cancer metabolism interacts with oncogenic signaling providing additional drug targets. Tumors overexpress the lipogenic enzyme fatty acid synthase (FASN) and are inhibited by FASN blockers, whereas normal cells are FASN‐negative and FASN‐inhibitor‐resistant. Here, we demonstrate that this holds true when ovarian/oviductal cells reside in their autochthonous tissues, whereas in culture they express FASN and are FASN‐inhibitor‐sensitive. Upon subculture, nonmalignant cells cease growth, express senescence‐associated β‐galactosidase, lose FASN and become FASN‐inhibitor‐resistant. Immortalized ovarian/oviductal epithelial cell lines—although resisting senescence—reveal distinct growth activities, which correlate with FASN levels and FASN drug sensitivities. Accordingly, ectopic FASN stimulates growth in these cells. Moreover, FASN levels and lipogenic activities affect cellular lipid composition as demonstrated by thin‐layer chromatography. Correlation between proliferation and FASN levels was finally evaluated in cancer cells such as HOC‐7, which contain subclones with variable differentiation/senescence and corresponding FASN expression/FASN drug sensitivity. Interestingly, senescent phenotypes can be induced in parental HOC‐7 by differentiating agents. In OC cells, FASN drugs induce cell cycle blockade in S and/or G2/M and stimulate apoptosis, whereas in normal cells they only cause cell cycle deceleration without apoptosis. Thus, normal cells, although growth‐inhibited, may survive and recover from FASN blockade, whereas malignant cells get extinguished. FASN expression and FASN drug sensitivity are directly linked to cell growth and correlate with transformation/differentiation/senescence only indirectly. FASN is therefore a metabolic marker of cell proliferation rather than a marker of malignancy and is a useful target for future drug development.     

Life table tests of evolutionary theories of senescence

The phenomenon of senescence requires both evolutionary and proximate explanations. The most widely accepted evolutionary explanation for senescence is that it never gets exposed to natural selection because environmental hazards kill all individuals before the age at which senescence causes decreased fitness. If this explanation is sufficient, wild populations should not demonstrate senescence, and their mortality rates should therefore remain constant during adult life, except when environmental causes of mortality have recently decreased. The alternative explanation for the persistence of the genes that cause senescence is that they have been selected for because they have pleiotropic effects that are beneficial early in life when the force of selection is strongest. Where this is the case, mortality rates should increase with age in wild populations. A method is described for using life table data to calculate an estimate of the intensity of selection acting on senescence in wild populations. This method is applied to a variety of life tables. The results suggest that pleiotropic genes may be important causes of senescence in some populations, but not in others. This has implications for research on the proximate mechanisms of senescence.     

Melatonin reverses H2O2‐induced premature senescence in mesenchymal stem cells via the SIRT1‐dependent pathway

Mesenchymal stem cells (MSCs) represent an attractive source for stem cell‐based regenerative therapy, but they are vulnerable to oxidative stress‐induced premature senescence in pathological conditions. We previously reported antioxidant and antiarthritic effects of melatonin on MSCs against proinflammatory cytokines. In this study, we hypothesized that melatonin could protect MSCs from premature senescence induced by hydrogen peroxide (H₂O₂) via the silent information regulator type 1 (SIRT1)‐dependent pathway. In response to H₂O₂ at a sublethal concentration of 200 μm , human bone marrow‐derived MSCs (BM‐MSCs) underwent growth arrest and cellular senescence. Treatment with melatonin before H₂O₂ exposure cannot significantly prevent premature senescence; however, treatment with melatonin subsequent to H₂O₂ exposure successfully reversed the senescent phenotypes of BM‐MSCs in a dose‐dependent manner. This result was made evident by improved cell proliferation, decreased senescence‐associated β‐galactosidase activity, and the improved entry of proliferating cells into the S phase. In addition, treatment with 100 μm melatonin restored the osteogenic differentiation potential of BM‐MSCs that was inhibited by H₂O₂‐induced premature senescence. We also found that melatonin attenuated the H₂O₂‐stimulated phosphorylation of p38 mitogen‐activated protein kinase, decreased expression of the senescence‐associated protein p16^INK4α, and increased SIRT1. Further molecular experiments revealed that luzindole, a nonselective antagonist of melatonin receptors, blocked melatonin‐mediated antisenescence effects. Inhibition of SIRT1 by sirtinol counteracted the protective effects of melatonin, suggesting that melatonin reversed the senescence in cells through the SIRT1‐dependent pathway. Together, these findings lay new ground for understanding oxidative stress‐induced premature senescence and open perspectives for therapeutic applications of melatonin in stem cell‐based regenerative medicine.     

Functions of melatonin in plants: a review

The number of studies on melatonin in plants has increased significantly in recent years. This molecule, with a large set of functions in animals, has also shown great potential in plant physiology. This review outlines the main functions of melatonin in the physiology of higher plants. Its role as antistress agent against abiotic stressors, such as drought, salinity, low and high ambient temperatures, UV radiation and toxic chemicals, is analyzed. The latest data on their role in plant–pathogen interactions are also discussed. Both abiotic and biotic stresses produce a significant increase in endogenous melatonin levels, indicating its possible role as effector in these situations. The existence of endogenous circadian rhythms in melatonin levels has been demonstrated in some species, and the data, although limited, suggest a central role of this molecule in the day/night cycles in plants. Finally, another aspect that has led to a large volume of research is the involvement of melatonin in aspects of plant development regulation. Although its role as a plant hormone is still far of from being fully established, its involvement in processes such as growth, rhizogenesis, and photosynthesis seems evident. The multiple changes in gene expression caused by melatonin point to its role as a multiregulatory molecule capable of coordinating many aspects of plant development. This last aspect, together with its role as an alleviating‐stressor agent, suggests that melatonin is an excellent prospect for crop improvement.     

From the Cover: Reduced fitness in progeny from old parents in a natural population

A nongenetic, transgenerational effect of parental age on offspring fitness has been described in many taxa in the laboratory. Such a transgenerational fitness effect will have important influences on population dynamics, population age structure, and the evolution of aging and lifespan. However, effects of parental age on offspring lifetime fitness have never been demonstrated in a natural population. We show that parental age has sex-specific negative effects on lifetime fitness, using data from a pedigreed insular population of wild house sparrows. Birds whose parents were older produced fewer recruits annually than birds with younger parents, and the reduced number of recruits translated into a lifetime fitness difference. Using a long-term cross-fostering experiment, we demonstrate that this parental age effect is unlikely to be the result of changes in the environment but that it potentially is epigenetically inherited. Our study reveals the hidden consequences of late-life reproduction that persist into the next generation.Reproducing at old age is known to incur costs such as an increased risk of polysomy and higher infant and maternal mortality. One potential cost that is hard to estimate occurs when parental age influences the lifespan or fertility of the next generation and beyond. First described by Alexander Graham Bell (1), this negative influence of parental age on offspring fitness [known as the “Lansing effect” (2–6)] has been observed in humans and in many taxa in the laboratory. Such transgenerational effects might have an epigenetic cause and are critical for understanding the evolution of late reproduction and longevity (7–11). However, to our knowledge, an effect of parental age on fitness in the next generation has not yet been shown conclusively in the wild, perhaps because its detection requires an exact knowledge of parental age and of the lifetime fate of offspring, data that are difficult to gather in natural populations (12). We have data from a natural, pedigreed population of passerines, house sparrows (Passer domesticus), in which we know the life history and precise fitness estimates of nearly all individuals (13). We use these data to demonstrate that parental age has a negative effect on fitness. We complement this study with a long-term cross-fostering experiment (14) that allows us to demonstrate that this effect is not environmentally induced. Our study reveals the hidden consequences of late-life reproduction for the next generation. Such transgenerational effects have the potential to help us better understand the evolution of aging and lifespan.     

Rejuvenation of the disposable soma: Repeated injury extends lifespan in an asexual annelid

The disposable soma theory of senescence proposes that aging is the result of the accumulation of somatic damage with age resulting from insufficient somatic maintenance and repair. Comparative studies that show a positive correlation between longevity and DNA excision repair efficiency in mammals provide support for the theory but their validity has been questioned. A more satisfactory approach to investigate the role of somatic damage accumulation in aging would be to manipulate experimentally the levels of somatic repair and observe its effect on longevity. Here I report the results of studies in the asexual annelid Paranais litoralis where I have experimentally extended the worms' lifespan by subjecting them to repeated injury. I propose that repeated injury enhanced the normal level of repair of the worms, resulting in a rejuvenation of the soma. These results provide experimental support for the disposable soma theory of senescence.     

Enhanced expression of p16 in seborrhoeic keratosis; a lesion of accumulated senescent epidermal cells in G1 arrest

BACKGROUND: Seborrhoeic keratosis (SK) is a common skin disease associated with skin ageing and photoageing, but only limited studies have been performed on SK and the senescence of keratinocytes. OBJECTIVES: We sought to clarify the genetic basis of SK and the senescence of keratinocytes. METHODS: Expression of p16, cyclins A, D and E, p21, p53, retinoblastoma (Rb) gene product and telomerase-associated protein 1 (TP1) in SK was examined by immunohistochemistry. DNA fragmentation in SK was detected by the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end labelling method. We cultured keratinocytes from SK lesions and non-lesional epidermis and examined expression of p16, observed morphology of the cultured cells by light and electron microscopy and measured survival time. RESULTS: p16, a cyclin-dependent kinase inhibitor, was expressed in all cells from SK lesions, whereas normal keratinocytes expressed p16 only in the granular cells. Other factors such as cyclins A, D and E, p21, p53, Rb gene product, and TP1, were not expressed in SK cells. These results suggest that p16 expression is a marker of SK and that p16 has a role in the pathogenesis of SK. DNA fragmentation was not detected in four of five SK tissue samples; one of the SK tissue samples showed DNA fragmentation only in the superficial upper layer of an SK lesion, suggesting that apoptosis was inhibited in SK cells. In contrast, normal epidermis showed DNA fragmentation in the granular and squamous layers. Immunohistochemical examination of cultured SK cells also revealed the presence of p16. A greater number of SK cells survived after 3 weeks of culture in comparison with normal keratinocytes. Features of senescence, such as a balloon-like appearance after lengthy culture and increased amounts of tonofilaments in cytoplasm, were observed in SK cells in culture. CONCLUSIONS: These results suggest that SK is a benign neoplasm where keratinocytes in a senescent condition and G1 arrest are accumulated.     

Overexpression of p53 but not Rb in the cytoplasm of neurons and small vessels in an autopsy of a patient with Cockayne syndrome

Cockayne syndrome presents senescence‐like changes starting in early infancy; however, the mechanism of premature aging remains unclear. In an autopsy of a 23‐year‐old woman with Cockayne syndrome, we evaluated the correlation between Cockayne pathology and the expression patterns of the senescence‐associated proteins p53 and Rb. Neuropathological findings in this case revealed basal ganglia calcification, tigroid leukodystrophy, bizarre reactive astrocytes, severe cerebellar atrophy with loss of Purkinje cells, and arteriolar/neuronal calcifications in the hypothalamus. Multiple arteriolar calcifications and sclerotic changes were seen in the central nervous system and kidney, but the endothelium of the aorta and coronary arteries remained intact appropriately for the individual's age without any finding of arteriosclerosis. Overexpression of p53 protein was confirmed in the cytoplasm of neurons in the basal ganglia, thalamus, hypothalamus, hippocampus and cerebellum, of arteriolar endothelial cells of the cerebrum and renal glomerular capillaries, and of cutaneous epithelial cells. The distribution of p53 overexpression was coincident with that of pathological alteration, such as neuronal loss, calcification and atrophy. High expression of p53 was localized in the cytoplasm, not in the nucleus. In contrast to p53, Rb was not expressed in any senescence lesion. In terms of senescence, distinct differences are found among organs in a patient with Cockayne syndrome. This segmental progeria differs from natural aging, and implicates p53 overexpression in the etiology of CS.     

延缓性衰老方法初探

本文从性医学、性心理学、性社会学、老年学、遗传学、营养学等多角度,围绕"性衰老"这个主题进行分析与探讨。为探讨延缓性衰老的方法,本文先讨论影响性衰老的各有关因素,继而进一步提出从端正性观念入手,保持老年期的适度性生活、坚持老年期的良好生活方式,认真看待更年期、积极探讨新"基因疗法"等五种途径与方法,从而谋求延缓性衰老,使老年夫妻延年益寿,并将享受到性福与快乐。     

Potential efficacy of p16 gene therapy for EBV-positive nasopharyngeal carcinoma

The p16 cell cycle inhibitory gene is a potentially critical molecular abnormality in nasopharyngeal carcinoma (NPC). Its expression is silenced through either deletion or promoter methylation in the vast majority of NPC. This in turn is associated with absent or reduced protein expression, which has been previously demonstrated by our group to correlate with inferior clinical outcome. Therefore, we were interested in evaluating the potential of adenoviral mediated p16 gene therapy (adv.p16) in an EBV-positive NPC model (C666-1). We confirm that under basal conditions, p16 protein is undetectable in C666-1 cells, which, in turn, is associated with retention of retinoblastoma protein (pRb) expression. P16 expression was observed as early as 4 hr after infection of C666-1 cells with adv.p16 (10 pfu/cell) with no discernible perturbation in pRb for up to 24 hr. At 48 hr post-infection, p16 expression continued to increase, but at this point, pRb expression started to decline significantly. Cell viability decreased in a dose-dependent manner, down to 20% using 50 pfu/cell of adv.p16. The addition of radiation therapy (RT) administered 24 hr post-infection achieved only a slightly additive cytotoxicity. Adv.p16 therapy resulted in multiple mechanisms of cytotoxicity, including cell cycle arrest at the G0/G1 phase, induction of senescence, along with apoptosis. Ex vivo infection of C666-1 cells with adv.p16 (25 pfu/cell) with subsequent implantation into scid mice completely prevented tumor formation, followed for up to 51 days. Our study demonstrates the potential efficacy of adv.p16 gene therapy for NPC, mediated through multimodal mechanisms of cytotoxicity. Future evaluations will examine strategies to increase in vivo tumor transduction with a view towards future clinical applications.