Hagai Yanai

Common gene signature of cancer and longevity

An association between aging/longevity and cancer has long been suggested, yet the evolutionary and molecular links between these complicated traits remain elusive. Here, we analyze the relationship between longevity- and cancer-associated genes/proteins (LAGs/LAPs and CAGs/CAPs, respectively). Specifically, we address the following questions: (1) to what extent the CAGs and LAGs are evolutionary conserved and how they (or their orthologs) are related to each other in diverse species? (2) Could they act in cooperative manner at a protein level via protein-protein interactions (PPIs) and, if so, by forming a PPI network? We found that (i) the common genes (both LAGs and CAGs) show the same remarkable trend from yeast to humans: tumor suppressors are associated with lifespan extension, whereas the oncogenes are associated with reduced lifespan; (ii) LAPs and CAPs have a significantly higher average connectivity than other proteins in the human interactome; and (iii) LAPs and CAPs may act in cooperative manner via numerous direct and indirect PPIs between themselves and eventually by forming a PPI network. Altogether, the results of this study provide strong evidence for the existence of evolutionary and molecular links between longevity and cancer.

Is rate of skin wound healing associated with aging or longevity phenotype

Wound healing (WH) is a fundamental biological process. Is it associated with a longevity or aging phenotype? In an attempt to answer this question, we compared the established mouse models with genetically modified life span and also an altered rate of WH in the skin. Our analysis showed that the rate of skin WH in advanced ages (but not in the young animals) may be used as a marker for biological age, i.e., to be indicative of the longevity or aging phenotype. The ability to preserve the rate of skin WH up to an old age appears to be associated with a longevity phenotype, whereas a decline in WH—with an aging phenotype. In the young, this relationship is more complex and might even be inversed. While the aging process is likely to cause wounds to heal slowly, an altered WH rate in younger animals could indicate a different cellular proliferation and/or migration capacity, which is likely to affect other major processes such as the onset and progression of cancer. As a point for future studies on WH and longevity, using only young animals might yield confusing or misleading results, and therefore including older animals in the analysis is encouraged.

Cellular Senescence Markers p16INK4a and p21CIP1/WAF Are Predictors of Hodgkin Lymphoma Outcome

Purpose: There is evidence that Hodgkin Reed-Sternberg (HRS) cells in classical Hodgkin lymphoma (cHL) could display some molecular and morphologic markers of cellular senescence (CS). We hypothesized that CS mechanisms may have potential prognostic relevance in cHL and investigated whether the expression of the well-established CS biomarkers p21CIP1/WAF1 and p16INK4a by HRS cells might be predictive of the probability of event-free survival (EFS). Experimental Design: The study analyzed a retrospective cohort of 147 patients and the results were validated on a cohort of 91 patients independently diagnosed and treated in a different institution. p16INK4a and p21CIP1/WAF1 were categorized as dichotomous variables (< or ≥ 30% of HRS cells at diagnosis) and evaluated in univariate and multivariate analysis. Results: Both molecules were independent prognostic factors. A positive staining of one of the two molecules in more than 30% HRS cells predicted a better EFS (P < 0.01). p16INK4a/p21CIP1/WAF1 together as a unique categorical variable (both <30%, either <30%, both ≥ 30%) sorted out three prognostic groups with better, intermediate, or worse outcome either overall or within I–II, bulky and advanced stages. The presence or the lack of the robust expression of p21CIP1/WAF1 and/or p16INK4a defined the prognosis in our series. Conclusions: These findings point to (i) the relevance of CS-related mechanisms in cHL, and to (ii) the prognostic value of a simple, reproducible, and low-cost immunohistochemical evaluation of p16INK4a and p21CIP1/WAF1 expression. Clin Cancer Res; 21(22); 5164–72. ©2015 AACR.

Tissue repair genes: the TiRe database and its implication for skin wound healing

Wound healing is an inherent feature of any multicellular organism and recent years have brought about a huge amount of data regarding regular and abnormal tissue repair. Despite the accumulated knowledge, modulation of wound healing is still a major biomedical challenge, especially in advanced ages. In order to collect and systematically organize what we know about the key players in wound healing, we created the TiRe (Tissue Repair) database, an online collection of genes and proteins that were shown to directly affect skin wound healing. To date, TiRe contains 397 entries for four organisms: Mus musculus, Rattus norvegicus, Sus domesticus, and Homo sapiens. Analysis of the TiRe dataset of skin wound healing-associated genes showed that skin wound healing genes are (i) over-conserved among vertebrates, but are under-conserved in invertebrates; (ii) enriched in extracellular and immuno-inflammatory genes; and display (iii) high interconnectivity and connectivity to other proteins. The latter may provide potential therapeutic targets. In addition, a slower or faster skin wound healing is indicative of an aging or longevity phenotype only when assessed in advanced ages, but not in the young. In the long run, we aim for TiRe to be a one-station resource that provides researchers and clinicians with the essential data needed for a better understanding of the mechanisms of wound healing, designing new experiments, and the development of new therapeutic strategies. TiRe is freely available online at http://www.tiredb.org.

Wide‐scale comparative analysis of longevity genes and interventions

Hundreds of genes, when manipulated, affect the lifespan of model organisms (yeast, worm, fruit fly, and mouse) and thus can be defined as longevity‐associated genes (LAGs). A major challenge is to determine whether these LAGs are model‐specific or may play a universal role as longevity regulators across diverse taxa. A wide‐scale comparative analysis of the 1805 known LAGs across 205 species revealed that (i) LAG orthologs are substantially overrepresented, from bacteria to mammals, compared to the entire genomes or interactomes, and this was especially noted for essential LAGs; (ii) the effects on lifespan, when manipulating orthologous LAGs in different model organisms, were mostly concordant, despite a high evolutionary distance between them; (iii) LAGs that have orthologs across a high number of phyla were enriched in translational processes, energy metabolism, and DNA repair genes; (iv) LAGs that have no orthologs out of the taxa in which they were discovered were enriched in autophagy (Ascomycota/Fungi), G proteins (Nematodes), and neuroactive ligand–receptor interactions (Chordata). The results also suggest that antagonistic pleiotropy might be a conserved principle of aging and highlight the importance of overexpression studies in the search for longevity regulators.

Uncovering the Geroprotective Potential of Medicinal Plants from the Judea Region of Israel

Plants growing in the Judea region are widely used in traditional medicine. This phytogeographic zone stands out in its climatic conditions and biodiversity. Consequently, both endemic and widely distributed Mediterranean plants growing in the area have unique chemotypes characterized by accumulation of relatively high levels of phytosteroids. Our comprehensive analysis revealed that many of the plants growing in the Judea region may hold a geroprotective potential. With this in mind, we undertook a wide screen of dozens of candidate herbal extracts for their cell protective, wound-healing, anti-inflammatory, and anti-cancer activities. The results obtained thus far have clearly shown that the extracts tested (1) protect normal human fibroblasts from genotoxic stress (prevent DNA double-strand beaks, increase cell survival and reduce the number of cells undergoing cellular senescence), (2) decrease secretion of pro-inflammatory cytokines, (3) promote wound healing, and (4) exert more pronounced cytotoxicity toward cancer cells.

Differential decrease in soluble and DNA-bound telomerase in senescent human fibroblasts

The role of telomere shortening in the induction of replicative cellular senescence (CS) is well known and as a result, the involvement of telomerase and in particular its catalytic subunit, the telomerase reverse transcriptase (TERT) in CS has also been investigated. However, the majority of studies were conducted on cells that generally express high levels of TERT (cancer and immortalized cells) while the role of telomerase in CS in normal cells has been investigated to a much lesser extent. In particular, it was reported that active TERT is expressed in early passages of cultured human keratinocytes but rapidly diminished towards entry to CS, without telomere shortening. With the putative importance of TERT/telomerase in CS and the aging process in mind, we investigated the expression of TERT and telomerase activity in primary cultures of adult human dermal fibroblasts (HDFs) in the in vitro model of replicative CS. We found that (i) HDFs expressed active TERT; (ii) TERT protein levels and telomerase activity were markedly decreased in senescent HDFs; and (iii) the reduction of TERT in the soluble fraction was more pronounced than in the DNA-bound one. The results suggest the importance of the non-canonical (telomere-unrelated) functions of TERT in cellular senescence.

Middle age enhances expression of innate immunity genes in a female mouse model of pulmonary fibrosis.

The lungs are highly sensitive to tissue fibrosis, with a clear age-related component. Among the possible triggers of pulmonary fibrosis are repeated inhalations of fine organic particles. How age affects this response, is still far from being fully understood. We examined the impact of middle-age on gene expression in pulmonary fibrosis, using the novel “inhalation challenge set” mouse model. Our results demonstrate that the response of female mice to exposure of Pantoea agglomerans extract primarily involves various immune-related pathways and cell–cell/cell–extracellular matrix interactions. We found that middle-age had a strong effect on the response to the P. agglomerans-induced lung fibrosis, featured by a more rapid response and increased magnitude of expression changes. Genes belonging to innate immunity pathways (such as the TLR signaling and the NK-cell mediated cytotoxicity) were particularly up-regulated in middle-aged animals, suggesting that they may be potential targets for the treatment of pulmonary fibrosis caused by inhalations of organic particles. Our analysis also highlights the relevance of the “inhalation challenge set” mouse model to lung aging and related pathology.

Middle age has a significant impact on gene expression during skin wound healing in male mice.

The vast majority of research on the impact of age on skin wound healing (WH) compares old animals to young ones. The middle age is often ignored in biogerontological research despite the fact that many functions that decline in an age-dependent manner have starting points in mid-life. With this in mind, we examined gene expression patterns during skin WH in late middle-aged versus young adult male mice, using the head and back punch models. The rationale behind this study was that the impact of age would first be detectable at the transcriptional level. We pinpointed several pathways which were over-activated in the middle-aged mice, both in the intact skin and during WH. Among them were various metabolic, immune-inflammatory and growth-promoting pathways. These transcriptional changes were much more pronounced in the head than in the back. In summary, the middle age has a significant impact on gene expression in intact and healing skin. It seems that the head punch model is more sensitive to the effect of age than the back model, and we suggest that it should be more widely applied in aging research on wound healing.

WIDE-SCALE COMPARATIVE ANALYSIS OF LONGEVITY GENES AND GENETIC INTERVENTIONS

Hundreds of genes have been identified as being involved in the control of lifespan in the four common model organisms (yeast, worm, fruit fly and mouse). A major challenge is to determine if longevity-associated genes (LAGs) are model-specific or may play a universal role as longevity regulators across diverse taxa. A wide-scale comparative analysis of the 1,805 known LAGs across 205 species revealed that (i) LAG orthologs are substantially over-represented, from bacteria to mammals, especially noted for essential LAGs; (ii) the effects on lifespan, when manipulating orthologous LAGs in different model organisms, were mostly concordant, despite of a high evolutionary distance between them; (iii) the most conserved LAGs were enriched in translational processes, energy metabolism, development, and DNA repair. The least conserved LAGs were enriched in autophagy (Fungi), G-proteins (Nematodes), and neuroactive ligand-receptor interactions (Chordata). The results also suggest that antagonistic pleiotropy is a conserved principle of aging.