Gerontology as oncology. Research on aging as the key to the understanding of cancer

Aging and Cancer: The Waning of Community Bonds

Cancer often arises in the context of an altered tissue landscape. We argue that a major contribution of aging towards increasing the risk of neoplastic disease is conveyed through effects on the microenvironment. It is now firmly established that aged tissues are prone to develop clones of altered cells, most of which are compatible with a normal histological appearance. Such increased clonogenic potential results in part from a generalized decrease in proliferative fitness, favoring the emergence of more competitive variant clones. However, specific cellular genotypes can emerge with reduced cooperative and integrative capacity, leading to disruption of tissue architecture and paving the way towards progression to overt neoplastic phenotypes.

Autoimmune hemolytic anemia, autoimmune neutropenia and aplastic anemia in the elderly

The physiology of the immune system involves morphologic and functional changes occurring along ageing, with a decrease in immune response and an increase in autoimmune phenomena, even in the absence of overt disese. Autoimmune cytopenias, namely autoimmune hemolytic anemia (AIHA), chronic idiopathic neutropenia (CIN) and aplastic anemia (AA), show different epidemiologic predilection, but are increasingly diagnosed in the elderly, where complications and comorbidities are more frequent. A systematic review of recent literature, shows that comorbidities as well as underlying deficiencies, medications, neoplasms, and, pathophysiologic chronic organ failures, frequently challenge the differential diagnosis in this setting and should always be evaluated and excluded. Complications, particularly infections and thrombosis for AIHA, and bleeding for AA, should be monitored and promptly treated. Treatment choice should be carefully weighed on the individual general condition and comorbidities, granted that intense primary care and support (including evidence-based transfusion policies) are provided. Finally, bone marrow histology is highly advisable in the elderly, both at diagnosis to detect underlying conditions, and along the follow-up to monitor possible bone marrow failure or neoplastic evolution.

The Aged Microenvironment Influences the Tumorigenic Potential of Malignant Prostate Epithelial Cells

The incidence of prostate cancer is directly linked to age, but age-associated changes that facilitate prostate cancer development and progression are poorly understood. This study investigated age-related changes in the prostate microenvironment for their influence on prostate cancer behavior. Prostate cancer cells implanted orthotopically into the prostate demonstrated accelerated tumor growth in aged compared with young mice. Metastatic lesions following intravenous injection were also more numerous in aged mice. Tumors from young and aged mice showed no significant differences concerning their proliferation index, apoptosis, or angiogenesis. However, analysis of tumor-infiltrating immune cells by IHC and RNA sequencing (RNA-seq) revealed elevated numbers of macrophages in prostates from aged mice, which are quickly polarized towards a phenotype resembling protumorigenic tumor-associated macrophages upon tumor cell engraftment. Older patients with prostate cancer (>60 years old) in The Cancer Genome Atlas Prostate Adenocarcinoma (TCGA-PRAD) dataset displayed higher expression of macrophage markers (CD163 and VSIG4) which associated with higher rates of biochemical relapse. Remodeling of the collagenous extracellular matrix (ECM) was associated with prostate cancer growth and invasion in the aged microenvironment. Moreover, the collagen matrix extracted from aged mice enhanced the invasiveness and proliferation of prostate cancer cells in vitro. Together, these results demonstrate that the aged prostatic microenvironment can regulate the growth and metastasis of malignant prostate cells, highlighting the role of resident macrophages and their polarization towards a protumorigenic phenotype, along with remodeling of the ECM. IMPLICATIONS: These findings demonstrate the importance of age-associated tumor microenvironment alterations in regulating key aspects of prostate cancer progression.

The impact of the sequence of pulmonary vessel ligation during anatomic resection for lung cancer on long-term survival--a prospective randomized trial

PURPOSE

The aim of this prospective randomized trial was to assess the influence of the sequence of pulmonary vessel ligation, during anatomic resection, on long term survival in patients with NSCLC.

MATERIAL/METHODS

This prospective randomized study included 385 patients treated surgically with lobectomy or pneumonectomy and standard lymphadenectomy between 1999 and 2003. Patients were randomly assigned to either primary ligation of the pulmonary artery or arteries (group A - 215 patients) or of the pulmonary vein or veins (group V - 170 patients). Patients were excluded if the sequence of vessel ligation was affected by technical difficulties or anatomic limitations. Univariate and multivariate analyses included: the sequence of vessel ligation, age, gender, tumor histology, stage (TNM), and cause of death (cancer related or non-cancer related).

RESULTS

Median follow-up was 63 months. The groups were comparable regarding gender, histology, type of resection, and T, N, and overall stage. Overall, 5-year survival reached 50% in group A and 54% in group V (p = 0.82) and did not differ significantly in cancer related and non-cancer related deaths (p = 0.67 and p = 0.26, respectively). Univariate analysis identified higher T and N factors, advanced stage, pneumonectomy, male sex, and older age as negative prognostic factors. Multivariate analysis demonstrated that age, T3-4 disease, and nodal involvement were associated with inferior survival.

CONCLUSIONS

The sequence of pulmonary vessel ligation during anatomic resection for non-small cell lung cancer does not significantly affect long-term survival.

Aging, nutrient signaling, hematopoietic senescence, and cancer

It is well known that cancer is one of the main causes of mortality in the aged population. Recent studies suggest that oncogenic pathways, such as the insulin-like growth factor-1 (IGF-I), Ras, and Akt/PKB, can contribute to both aging and cancer not only by promoting growth and preventing apoptosis, but also by promoting DNA damage and genomic instability. Epidemiological studies suggest that the chronic, low-grade inflammation that accompanies aging also contributes to tissue damage and tumor progression. Coupled with the accumulation of senescent cells and declining immune function, this leads to the generation and survival of cancer cells, possibly explaining why advanced age is the primary risk factor for cancer.

Predictors of survival among older adults with ependymoma

The biological process of aging encompasses a multitude of complex physiological and lifestyle changes that may alter the way typical prognostic factors affect survival among older ependymoma patients. Because very little is known about the clinical significance of traditional prognostic factors and the magnitude of their effects among older individuals, the purpose of this study was to evaluate the associations between survival and demographic and tumor characteristics among patients with ependymoma who were 60 years of age or older. Using the 1973-2007 dataset from the Surveillance, Epidemiology and End Results (SEER) program, we evaluated the impact of several factors on both overall and ependymoma-specific survival, utilizing multivariable Cox proportional hazards regression. We identified 367 ependymoma cases who were 60 years of age or older at diagnosis and had complete data from SEER. Of these, 19 (5.2%) had anaplastic tumors; all others were low-grade tumors. Age, tumor site, extent of surgery, and tumor histology were found to be significant predictors of ependymoma prognosis. The strongest predictor of poor outcome was supratentorial tumor location (adjusted HR: 6.94, 95% CI: 3.19-15.08, compared to spinal cord tumors). Our study suggests that tumor location, tumor histology, and surgical margin may be key predictors of survival among older ependymoma patients. We believe our study is one of the first to assess the prognostic value of these factors for ependymoma survival exclusively in an older patient population.

Comparative endocrinology of aging and longevity regulation

Hormones regulate growth, development, metabolism, and other complex processes in multicellular animals. For many years it has been suggested that hormones may also influence the rate of the aging process. Aging is a multifactorial process that causes biological systems to break down and cease to function in adult organisms as time passes, eventually leading to death. The exact underlying causes of the aging process remain a topic for debate, and clues that may shed light on these causes are eagerly sought after. In the last two decades, gene mutations that result in delayed aging and extended longevity have been discovered, and many of the affected genes have been components of endocrine signaling pathways. In this review we summarize the current knowledge on the roles of endocrine signaling in the regulation of aging and longevity in various animals. We begin by discussing the notion that conserved systems, including endocrine signaling pathways, "regulate" the aging process. Findings from the major model organisms: worms, flies, and rodents, are then outlined. Unique lessons from studies of non-traditional models: bees, salmon, and naked mole rats, are also discussed. Finally, we summarize the endocrinology of aging in humans, including changes in hormone levels with age, and the involvement of hormones in aging-related diseases. The most well studied and widely conserved endocrine pathway that affects aging is the insulin/insulin-like growth factor system. Mutations in genes of this pathway increase the lifespan of worms, flies, and mice. Population genetic evidence also suggests this pathway's involvement in human aging. Other hormones including steroids have been linked to aging only in a subset of the models studied. Because of the value of comparative studies, it is suggested that the aging field could benefit from adoption of additional model organisms.

Cancer, aging and immunotherapy: lessons learned from animal models

Aging of the immune system is associated with a dramatic reduction in responsiveness as well as functional dysregulation. This deterioration of immune function with advancing age is associated with an increased incidence of cancer. Although there is a plethora of reports evaluating the effect of immunotherapy in stimulating antitumor immune responses, the majority of these studies do not pay attention to the effect aging has on the immune system. Studies from our group and others indicate that immunotherapies could be effective in the young, are not necessarily effective in the old. To optimally stimulate an antitumor immune response in the old, it is necessary to (1) identify and understand the intrinsic defects of the old immune system and (2) use relevant models that closely reflect those of cancer patients, where self-tolerance and aging are present simultaneously. The present review summarizes some defects found in the old immune system affecting the activation of antitumor immune responses, the strategies used to activate stronger antitumor immune response in the old and the use of a tolerant animal tumor model to target a self-tumor antigen for the optimization of immunotherapeutic interventions in the old.

Relationships between cancer and aging: a multilevel approach

The incidence of cancer increases with age in humans and in laboratory animals alike. There are different patterns of age-related distribution of tumors in different organs and tissues. Aging may increase or decrease the susceptibility of various tissues to initiation of carcinogenesis and usually facilitates promotion and progression of carcinogenesis. Aging may predispose to cancer in two ways: tissue accumulation of cells in late stages of carcinogenesis and alterations in internal homeostasis, in particular, alterations in immune and endocrine systems. Increased susceptibility to the effects of tumor promoters is found both in aged animals and aged humans, as predicted by the multistage model of carcinogenesis. Aging is associated with a number of events at the molecular, cellular and physiological levels that influence carcinogenesis and subsequent cancer growth. An improved understanding of age-associated variables impacting on the tumor microenvironment, as well as the cancer cells themselves, will result in improved treatment modalities in geriatric oncology.

Implications of aging and self-tolerance on the generation of immune and antitumor immune responses

Cancer statistics show a disproportionately higher burden of tumors in the old. Most of the studies evaluating vaccination strategies have not taken into consideration the effect that aging has on the immune system. For the first time, we describe an animal tumor model in which self-tolerance and aging are present at the same time. FVB-Her-2/neu mice which are tolerant to neu antigens crossed with HLA-A2/Kb mice (A2xneu) develop spontaneous tumors when they are more than 22 months old. Analysis of CD8(+) T-cell-specific responses in A2xneu mice indicated that the priming activity of old A2xneu mice to induce an immune response was diminished compared with young animals. Following intratumoral injections of CpG-ODN, approximately 30% of young A2xneu mice rejected the tumor; however, no antitumor effect was observed in old A2xneu mice. Analysis of T regulatory cells (Treg) indicated that there are significantly more Tregs in old animals. After CpG-ODN vaccination plus Treg depletion, 70% of young A2xneu mice rejected the tumor. The same treatment prolonged survival in old A2xneu mice, but none of the animals rejected the tumor. Even though CpG-ODN injections plus Treg depletion could rescue the antitumor responses against self-tumor antigens in young tolerant mice, the same therapy is not as effective in old tolerant hosts. Relevant tumor models such as the A2xneu mice in which self-tolerance and aging are present at the same time are critical to allow the optimization of vaccination strategies to effectively stimulate immune responses against self-tumor antigens in the young and the old.

A statistical model for the identification of genes governing the incidence of cancer with age

The cancer incidence increases with age. This epidemiological pattern of cancer incidence can be attributed to molecular and cellular processes of individual subjects. Also, the incidence of cancer with ages can be controlled by genes. Here we present a dynamic statistical model for explaining the epidemiological pattern of cancer incidence based on individual genes that regulate cancer formation and progression. We incorporate the mathematical equations of age-specific cancer incidence into a framework for functional mapping aimed at identifying quantitative trait loci (QTLs) for dynamic changes of a complex trait. The mathematical parameters that specify differences in the curve of cancer incidence among QTL genotypes are estimated within the context of maximum likelihood. The model provides testable quantitative hypotheses about the initiation and duration of genetic expression for QTLs involved in cancer progression. Computer simulation was used to examine the statistical behavior of the model. The model can be used as a tool for explaining the epidemiological pattern of cancer incidence.

Carcinogenesis and aging 20 years after: escaping horizon

Carcinogenesis is a multistage process: neoplastic transformation implies the engagement of a cell through sequential stages, and different agents may affect the transition between continuous stages. Multistage carcinogenesis is accompanied by disturbances in tissue homeostasis and perturbations in nervous, hormonal, and metabolic factors which may affect antitumor resistance. The development of these changes depends on the susceptibility of various systems to a carcinogen and on the dose of the carcinogen. Changes in the microenvironment may condition key carcinogenic events and determine the duration of each carcinogenic stage, and sometimes they may even reverse the process of carcinogenesis. These microenvironmental changes influence the proliferation rate of transformed cells, the total duration of carcinogenesis and, consequently, the latent period of tumor development. Aging may increase or decrease the susceptibility of various tissues to initiation of carcinogenesis and usually facilitates promotion and progression of carcinogenesis. Aging may predispose to cancer by two mechanisms: tissue accumulation of cells in late stages of carcinogenesis and alterations in internal homeostasis, in particular, alterations in immune and endocrine system. Aging is associated with number of events at molecular, cellular and physiological levels that influence carcinogenesis and subsequent cancer growth.

Biology of aging and cancer

BACKGROUND

The incidence of cancer increases with age in both humans and laboratory animals. A clear understanding of the causes of the age-related increase in cancer incidence is needed to develop a strategy for primary cancer prevention.

METHODS

We summarized the data available in the literature and our own experience in hormonal metabolic shifts in organisms and disturbances at tissue and cellular levels observed in natural aging and in different types of carcinogenesis in vivo.

RESULTS

There are incongruent patterns of age-related distribution of tumors in different organs and tissues. Aging may increase or decrease the susceptibility of various tissues to initiation of carcinogenesis and usually facilitates promotion and progression of carcinogenesis. Aging may predispose to cancer by at least two mechanisms: tissue accumulation of cells in late stages of carcinogenesis and alterations in internal homeostasis, in particular, alterations in immune and endocrine system. Increased susceptibility to the effects of tumor promoters is found in both aged animals and aged humans, as predicted by the multistage model of carcinogenesis.

CONCLUSIONS

Aging is associated with a number of events at the molecular, cellular and physiologic levels that influence carcinogenesis and subsequent cancer growth. A clearer understanding of these events will help in predicting and treating cancer more effectively.

Molecular signaling and genetic pathways of senescence: Its role in tumorigenesis and aging

In response to progressive telomere shortening in successive cell divisions, normal somatic cells enter senescence, during which they cease to proliferate irreversibly and undergo dramatic changes in gene expression. Senescence can also be activated by various types of stressful stimuli, including aberrant oncogenic signaling, oxidative stress, and DNA damage. Because of the limited proliferative capacity imposed by senescence, as well as the ability of senescent cells to influence neighboring non-senescent cells, senescence has been proposed to play an important role in tumorigenesis and to contribute to aging. Considerable effort has been put into elucidating the molecular mechanisms of senescence, including the signals that trigger senescence, the molecular pathways by which cells enter senescence, and evidence that supports its role in tumorigenesis and aging.

Cancer and aging: symposium of the 27th annual meeting of the Japanese society for biomedical gerontology, Tokyo

Although many hypotheses have been proposed to explain the strong link between aging and cancer, the exact mechanisms responsible for the increased frequency of occurrence of cancer with advancing age have not been fully defined. Recent evidence indicates that malregulation of the apoptotic process may be involved in some aging process as well as in the development of cancer. Although it is still under debate how apoptosis is expressed during aging in vivo, this phenomenon is an important factor in unwinding the complicated mechanisms that link cancer and aging. In this review, we report on the discussion at the symposium of the 27th annual meeting of the Japanese society for biomedical gerontology, regarding recent findings from aging and carcinogenesis studies using animal models, the characteristics of cancer in patients with Werner's syndrome, the epigenetic changes in human cancers and aging, and the characteristics of human cancers in the elderly. It was concluded that apoptosis plays a role in the aging process and carcinogenesis in vivo, likely as an inherent protective mechanism against various kinds of damages to genes/chromosomes.

Aging, tumor suppression and cancer: high wire-act!

Evolutionary theory holds that aging is a consequence of the declining force of natural selection with age. We discuss here the evidence that among the causes of aging in complex multicellular organisms, such as mammals, is the antagonistically pleiotropic effects of the cellular responses that protect the organism from cancer. Cancer is relatively rare in young mammals, owing in large measure to the activity of tumor suppressor mechanisms. These mechanisms either protect the genome from damage and/or mutations, or they elicit cellular responses-apoptosis or senescence--that eliminate or prevent the proliferation of somatic cells at risk for neoplastic transformation. We focus here on the senescence response, reviewing its causes, regulation and effects. In addition, we describe recent data that support the idea that both senescence and apoptosis may indeed be the double-edged swords predicted by the evolutionary hypothesis of antagonistic pleiotropy-protecting organisms from cancer early in life, but promoting aging phenotypes, including late life cancer, in older organisms.

Non-neutral role of replicative senescence in tissue homeostasis and tumorigenesis

Normal somatic cells divide only a limited number of times reaching a state known as replicative senescence. This restraint in reproductive potential has been proposed as a mechanism evolved in higher eukaryotes to protect the organism from developing cancer. However, despite this protection there is a positive correlation between tumor incidence and organism aging when cells are potentially closer to their replication limit. We use simple mathematical models derived from quasispecies theory to analyse the role of senescence in various scenarios with different cell types according to their replicative capacity. The models predict that a situation with cells launching more often the senescence response plays against tissue homeostasis favoring tumor initiation. It is also shown that cancer cells arising early in organism life are more sensitive to genetic instabilities progressing less often toward tissue invasion. The passage of cells through crisis emerges as a mechanism to maintain tissue homeostasis that is weakened in aged individuals. The models introduced, though simple, help to integrate experimental information relating tumorigenesis with cellular and organism aging phenomena.

The surgical management of elderly cancer patients

Although cancer in the elderly is extremely common, few health professionals in oncology are familiar with caring for series of oncogeriatric patients. Surgery is at present the first choice, but is frequently delivered suboptimally: under-treatment is justified by concerns about unsustainable toxicity, whilst over-treatment is explained by the lack of knowledge in optimising preoperative risk assessment. This article summarises the point of view of the Surgical Task Force @ SIOG (International Society for Geriatric Oncology), pointing out differences from, and similarities to, the younger cohorts of cancer patients, and highlighting the latest updates and trends specifically related to senior cancer patients.

The role of methods in maintaining orthodox beliefs in health research

Views about correct ways of obtaining knowledge develop from socially constructed tenets and beliefs. The dominant beliefs about how health research should be conducted are derived from the biomedical model of human health. The beliefs are maintained by traditions developed in support of the orthodox model and by power relationships. This paper examines the impact of the orthodox views of the biomedical model on the research methods used to investigate population health issues. Experimental design is the "gold standard" for research in the biomedical model. Beliefs about the superiority of experimental research have affected most types of health research. The role that methods assume in maintaining the orthodoxy is examined. Acceptance in other health disciplines of the attitudes of the dominant paradigm and limited options for research and training in alternatives to the orthodoxy became major influences reinforcing orthodox beliefs about health research.

Autoimmunity and geriatrics: clinical significance of autoimmune manifestations in the elderly

The immune system undergoes continuous morphologic and functional changes throughout the years, and it is now believed that the immune response has its peak function in puberty and gradually decreases with age (immunosenescence). Recent studies in healthy octogenarian patients suggest that the immune system, instead of suffering a generalized deterioration, undergoes a remodelling/readjustment of its major functions. Increase in two contrasting phenomena coexist in immunosenescence: on the one hand, a decrease in the capacity of the immune response and, on the other hand autoantibody production. The possible consequences of this progressive 'ageing' of the immune system are the increase in autoimmune phenomena, incidence of neoplasia and predisposition to infections. The study of autoimmune manifestations in elderly populations should be considered a priority for future medical research because of increasing life expectancy, especially in developed countries. This review analyses the main immune disorders associated with immunosenescence, the prevalence and clinical significance of autoantibodies in the elderly and the clinical expression of the main autoimmune diseases in older patients.

Cancer and ageing: rival demons?

Organisms with renewable tissues use a network of genetic pathways and cellular responses to prevent cancer. The main mammalian tumour-suppressor pathways evolved from ancient mechanisms that, in simple post-mitotic organisms, act predominantly to regulate embryogenesis or to protect the germline. The shift from developmental and/or germline maintenance in simple organisms to somatic maintenance in complex organisms might have evolved at a cost. Recent evidence indicates that some mammalian tumour-suppressor mechanisms contribute to ageing. How might this have happened, and what are its implications for our ability to control cancer and ageing?

The relationship between aging and carcinogenesis: a critical appraisal

The incidence of cancer increases with age in humans and in laboratory animals alike. There are different patterns of age-related distribution of tumors in different organs and tissues. Aging may increase or decrease the susceptibility of various tissues to initiation of carcinogenesis and usually facilitates promotion and progression of carcinogenesis. Aging may predispose to cancer by several mechanisms: (1) tissue accumulation of cells in late stages of carcinogenesis; (2) alterations in homeostasis, in particular, alterations in immune and endocrine system and (3) telomere instability linking aging and increased cancer risk. Increased susceptibility to the effects of tumor promoters is found both in aged animals and aged humans, as predicted by the multistage model of carcinogenesis. Available evidence supporting the relevance of replicative senescence of human cells and telomere biology to human cancer seems quite strong, however, the evidence linking cellular senescence to human aging is controversial and required additional studies. Data on the acceleration of aging by carcinogenic agents as well as on increased cancer risk in patients with premature aging are critically discussed. In genetically modified mouse models (transgenic, knockout or mutant) characterized by the aging delay, the incidence of tumors usually similar to those in controls, whereas the latent period of tumor development is increased. Practically all models of accelerated of aging in genetically modified animals show the increase in the incidence and the reduction in the latency of tumors. Strategies for cancer prevention must include not only measures to minimize exposure to exogenous carcinogenic agents, but also measures to normalize the age-related alterations in internal milieu. Life-span prolonging drugs (geroprotectors) may either postpone population aging and increase of tumor latency or decrease the mortality in long-living individuals in populations and inhibit carcinogenesis. At least some geroprotectors may increase the survival of a short-living individuals in populations but increase the incidence of malignancy.

Cancer and aging: a model for the cancer promoting effects of the aging stroma

The incidence of cancer rises exponentially with age in humans and many other mammalian species. Malignant tumors are caused by an accumulation of oncogenic mutations. In addition, malignant tumorigenesis requires a permissive tissue environment in which mutant cells can survive, proliferate, and express their neoplastic phenotype. We propose that the age-related increase in cancer results from a synergy between the accumulation of mutations and age-related, pro-oncogenic changes in the tissue milieu. Most age-related cancers derive from the epithelial cells of renewable tissues. An important element of epithelial tissues is the stroma, the sub-epithelial layer composed of extracellular matrix and several cell types. The stroma is maintained, remodeled and repaired by resident fibroblasts, supports and instructs the epithelium, and is essential for epithelial function. One change that occurs in tissues during aging is the accumulation of epithelial cells and fibroblasts that have undergone cellular senescence. Cellular senescence irreversibly arrests proliferation in response to damage or stimuli that put cells at risk for neoplastic transformation. Senescent cells secrete factors that can disrupt tissue architecture and/or stimulate nearby cells to proliferate. We therefore speculate that their presence may create a pro-oncogenic tissue environment that synergizes with oncogenic mutations to drive the rise in cancer incidence with age. Recent evidence lends support to this idea, and suggests that senescent stromal fibroblasts may be particularly adept at creating a tissue environment that can promote the development of age-related epithelial cancers.

Updates in surgical oncology for elderly patients

Elderly patients affected by solid tumours are frequently encountered on the surgical ward. Prejudice regarding operative risks and long term outcomes may alter their surgical management. Large series of elderly cancer subjects have been analysed and conclusive data are now available, to better tailor their management. Specific epidemiological data are presented in this review, screening programs critically considered, treatment procedures discussed, and the effectiveness of follow-up protocols is analysed together with cost effectiveness issues. Quality of life issues should not be neglected, and a continuous educational endeavour targeted at specialists and general practitioners is desirable.

Telomeres, aging and cancer: in search of a happy ending

Telomeres are distinctive structures, composed of a repetitive DNA sequence and associated proteins, that cap the ends of linear chromosomes. Telomeres are essential for maintaining the integrity and stability of eukaryotic genomes. In addition, under some circumstances, telomeres can influence cellular gene expression. In mammals, the length, structure, and function of telomeres have been proposed to contribute to cellular and organismal phenotypes associated with cancer and aging. Here, we discuss what is known about the basis for the links between telomeres, aging and cancer, and some of the known and proposed consequences of telomere dysfunction and maintenance for mammalian cells and organisms.

Cellular senescence, cancer and aging: the telomere connection

Telomeres are the repetitive DNA sequences and specialized proteins that form the distinctive structure that caps the ends of linear chromosomes. Telomeres allow cells to distinguish the chromosome ends from double strand DNA breaks. The telomeric structure prevents the degradation or fusion of chromosome ends, and thus is essential for maintaining the integrity and stability of eukaryotic genomes. In addition, and perhaps less widely appreciated, telomeres may also indirectly influence gene expression. The length, structure and organization of telomeres are regulated by a host of telomere-associated proteins, and can be influenced by basic cellular processes such as cell proliferation, differentiation, and DNA damage. In mammalian cells, telomere length and/or telomere structure have been linked to both cancer and aging. Here, we briefly review what is known about mammalian telomeres and the proteins that associate with them, and discuss the cellular and organismal consequences of telomere dysfunction and the evidence that cells with dysfunctional telomeres can contribute to cancer and aging phenotypes.

Mutant and genetically modified mice as models for studying the relationship between aging and carcinogenesis

Increased interest is emerging in using mouse models to assess the genetics of aging and age-related diseases, including cancer. However, only limited information is available regarding the relationship between aging and spontaneous tumor development in genetically modified mice. Analysis of various transgenic and knockout rodent models with either a shortened or an extended life span, provides a unique opportunity to evaluate interactions of genes involved in the aging process and carcinogenesis. There are only a few models which show life span extension. Ames dwarf mutant mice, p66(-/-) knockout mice, alpha MUPA and MGMT transgenic mice live longer than wild-type strains. The incidence of spontaneous tumors in these mutant mice was usually similar to those in controls, whereas the latent period of tumor development was increased. Practically all models of accelerated aging showed increased incidence and shorter latency of tumors. This phenomenon has been observed in animals which display a phenotype that more closely resembles natural aging, and in animals which manifest only some features of the normal aging process. These observations are in agreement with an earlier established positive correlation between tumor incidence and the rate of tumor incidence increase associated with aging and the aging rate in a population. Thus, genetically modified animals are a valuable tool in unravelling mechanisms underlying aging and cancer. Systemic evaluation of newly generated models should include onco-gerontological studies.

Changes in immune function with age

Aging is associated with a decline in immune function in humans and animals. The primary defects appear to reside in the T-cell compartment. Improving understanding of the mechanisms underlying the general decline in immune functions with age may enhance our ability to prevent and treat age-associated illnesses. Development of biomarker(s) of immune senescence may eventually help clinicians to identify subpopulations of the elderly who are at risk for infections, malignancies, and possibly autoimmune diseases.

New surgical options for elderly lung cancer patients

To understand the size of the aging population in the United States, the imminent need to include the elderly in clinical studies on lung cancer, and the safe potential of video-assisted thoracic surgery, and to change awareness of the elderly's need for and ability to undergo treatment for lung cancer, clinical studies of video-assisted thoracic surgery in patients > or = 70 years of age are presented. The elderly are a fast-growing part of the American population who are at high risk for lung cancer and should be included in clinical studies. Age alone should not be a contradiction to thoracic surgical interventions when video thoracoscopy is performed as treatment.

Predictors of cancer mortality in elderly subjects

Cancer mortality was analysed in 3282 elderly subjects aged > or =65 years from 2 cohorts of general population having different life-style patterns. They took part in the CASTEL (CArdiovascular STudy in the ELderly), a 12-year lasting prospective Italian study. The aim of the present analysis was to identify the items able to influence cancer mortality. A biochemical profile and a questionnaire on lifestyle were collected. Continuous items were averaged and compared with analysis of variance, frequencies with the Pearson's chi2 test. Mortality was recorded yearly for 12 years from the Registrar's Office and causes of death double-checked by consulting medical case sheets and family doctors' files. The influence of items on mortality was evaluated with the Cox multivariate analysis. Relative risk (RR) of each item was adjusted for confounders. Age, gender, tobacco smoking, the presence of respiratory symptoms, low body mass index in males, serum alanine transaminase (ALT) and alkaline phosphatase (ALP), as well as the town of residence, were powerful predictors of cancer mortality. In the entire population, 12-year overall mortality was 49.4%, cardiovascular 22.8%, and neoplastic 11%; the latter was higher in males than in females (15.7% vs. 7.9%, p < 0.00001). In subjects with respiratory symptoms neoplastic mortality was 11.6% (RR: 1.47) vs. 9.7% in those without symptoms (p < 0.01). Subjects with very low cholesterol (< or = 178 mg/dl), those with high uric acid (> or =8.7 mg/ dl) and males with low body mass index (< or =22.7 kg/ m2) has an increased risk of cancer mortality. RR of cancer mortality increased with increasing ALT or ALP. It was approximately 1 in those having ALT and ALP between 9 and 41.2 U/I, 1.41 in those exceeding this latter level and < 1 in those below 9 U/I. RR of ALP had a similar trend, the best protective cut-off value being < 106 and the worst one > 177 U/I. When both serum enzymes were simultaneously raised, RR of cancer mortality increased to 2.84.

The role of interleukin-1 in interactive senescence and age-related human endometrial cancer

The causes of the age-related increase in cancer rates are poorly understood. One cause could be age-related changes in the stromal/epithelial cell interactions that facilitate tumorigenesis. We tested the hypothesis that aging of human endometrial stromal fibroblasts (ESF) alters their influence over endometrial epithelial cells. ESF from adults were found to inhibit anchorage-independent proliferation, to restrain colony outgrowth, and to induce formation of normal tissue architecture by human endometrial cancer cells. As ESF age, these inhibitory influences on malignant-like behaviors by epithelial cells are altered, becoming stimulatory. Age-related change in interleukin-1alpha (IL-1alpha) expression is a molecular determinant of ESF/epithelial cell interactions. Levels of IL-1alpha and IL-1-induced mRNAs increase in ESF with age. Treatment with IL-1 accelerates age-related changes in mRNA abundance and loss of ESF restraint over malignancy-associated behaviors by epithelial cells. Transfection of ESF with the intracellular IL-1 receptor antagonist preserved the young phenotype with respect to interactions with epithelial cells and prevented age-associated increases in groalpha and IL-8 mRNA levels. Our results indicate that aging of ESF is accompanied by an interactive senescence that alters ESF signaling to cancer cells and could contribute to increased cancer rates by providing a microenvironment that is more conducive to tumorigenesis.

Age-related expression of PEDF/EPC-1 in human endometrial stromal fibroblasts: implications for interactive senescence

Aging is the major risk factor for many cancers, and age-related changes in the tissue microenvironment can facilitate tumor growth. This study uses human endometrial cells to begin to test the hypothesis that age-related changes in pigment epithelium-derived factor/early population doubling cDNA-1 (PEDF/EPC-1) levels create an environment that is more permissive to tumor growth. Endometrial stromal fibroblasts (ESF) are the predominant cell type in the human endometrium and exert regulatory control over the glandular epithelial cells, which are the source of most tumors. As ESF age in vitro, their ability to regulate appropriate growth and differentiation of epithelial cells declines. Endometrial epithelial cells in primary culture expressed relatively low levels of PEDF/EPC-1 mRNA. In contrast, early passage quiescent ESF from adult donors produce higher levels of the 1.5-kb PEDF/EPC-1 mRNA and 50-kDa secreted protein than epithelial cells. As ESF age in vitro the relative abundance of PEDF/EPC-1 mRNA declines, as does the level of PEDF/EPC-1 protein secreted into cell culture medium. Treatment with PEDF/EPC-1 protein had no effect on ESF proliferation but did inhibit anchorage-dependent and anchorage-independent proliferation of endometrial carcinoma cells in a dose- and time-dependent manner. These findings imply that an age-related loss of PEDF/EPC-1 expression by ESF could eliminate a negative regulator of cancer cell growth and, thereby, contribute to the age-related increase in cancer incidence.

Plasticity of the neoplastic phenotype in vivo is regulated by epigenetic factors

Age of host and transplantation-site microenvironment influence the tumorigenic potential of neoplastically transformed liver epithelial cells. Tumorigenic BAG2-GN6TF rat liver epithelial cells consistently form tumors at ectopic sites, but differentially express tumorigenicity or hepatocytic differentiation in the liver depending on host age and route of cell transplantation into the liver. Direct inoculation into host livers concentrates tumor cells locally, resulting in undifferentiated tumors near the transplantation site in both young (3-month-old) and old (18-month-old) rats. Transplantation-site tumors regress within 1 month in the livers of young rats, but grow progressively in old rats. However, inoculation of cells into the spleen distributes transplanted cells individually throughout the liver, resulting in hepatocytic differentiation by tumor cells with concomitant suppression of their tumorigenicity in young rats. When transplanted into livers of old rats by splenic inoculation, or when young hepatic-transplant recipients are allowed to age, hepatocytic progeny of BAG2-GN6TF cells proliferate to form foci, suggesting that the liver microenvironment of old rats incompletely regulates the proliferation and differentiation of tumor cell-derived hepatocytes. Upon removal from the liver, BAG2-GN6TF-derived hepatocytes revert to an undifferentiated, aggressively tumorigenic phenotype. We posit that the spectrum between normal differentiation and malignant potential of these cells reflects the dynamic interaction of the specific transformation-related genotype of the cells and the characteristics of the tissue microenvironment at the transplantation site. Changes in the tissue milieu, such as those that accompany normal aging, may determine the ability of a genetically aberrant cell to produce a tumor.

Epidemiology of cancer of the lip in The Netherlands

Descriptive epidemiological data of new cases of squamous cell carcinoma of the vermilion border of the lip in the Netherlands from 1989-94 inclusive are presented. Lip cancer represented 0.47 and 0.09% of all new malignancies in males and females, respectively. The lower lip was the most frequently affected site. The majority of the lip cancers were diagnosed in tumour stage I. The median age at diagnosis in males was 68 years, 5 years less than in females. The overall male-to-female ratio was 5.7. Age-adjusted incidence rates in males and females were 2.2 and 0.3 per 100,000 (ESR), respectively. The cumulative lifetime risk for developing lip cancer was 0.15 for males and 0.03 for females. Mortality/incidence ratios in males and females were 0.05 and 0.07, respectively. Differences in lip cancer incidence were observed between an urban and a rural area. There was a positive association between the occurrence of lip cancer and rural residence; rate ratios were 3.3 among males and 3.5 among females.

Aging and cancer: the double-edged sword of replicative senescence

Normal cells do not divide indefinitely. This trait, termed the finite replicative life span of cells, limits the capacity for cell division by a process termed cellular or replicative senescence. Replicative senescence is thought to be a tumor suppression mechanism and also a contributor to organismic aging. This article reviews what is known about the genetics and molecular biology of cell senescence. It discusses the evidence that replicative senescence suppresses tumorigenesis, at least in young organisms, and that it also contributes to the aging of mitotic tissues. Finally, it puts forth the somewhat unorthodox view that, in older organisms, senescent cells may actually contribute to carcinogenesis.

Creating knowledge relevant for public health applications in immunology and aging

New types of knowledge are needed to meet public health challenges that are growing in scope and complexity. While contemporary life exposes people to interactions among an increasingly complex array of biological and psychosocial influences that can damage health, the complexity inherent in disease processes is generally neglected in research for public health applications. Health promotion and the prevention and control of diseases, including chronic diseases that develop over long periods of time, depend on strengthening the resistance of human hosts. The effective functioning of the immune system is an essential pathway through which host defenses operate to protect health. Research on immunology and aging can help to provide the types of new knowledge needed for effective health promotion to meet public health challenges in a period of global aging.

Telomerase: anti-cancer target or just a fascinating enzyme?

Telomerase activity is upregulated in most types of malignant tumor. Highly selective small molecule inhibitors will be needed to understand the biological basis for this observation and to determine if telomerase is a viable target for chemotherapy.

Glucocorticoids and aging

Information on the role of glucocorticoids in the aging of vertebrate species is reviewed. There is strong evidence that elevated plasma glucocorticoid levels have a causal role in the rapid deterioration following reproduction in semelparous vertebrate species. If this deterioration is an example of rapid senescence, then it is clear that glucocorticoids can promote aging processes in vertebrate species. However, the evidence that glucocorticoids promote aging in the gradual senescence characteristic of most vertebrate species is not robust. Indeed, there is reason to believe that periods of moderately elevated plasma glucocorticoid levels may retard aging processes in rats, mice, and humans.

Squamous cell carcinoma of the lips in a northern Greek population. Evaluation of prognostic factors on 5-year survival rate--I

The purpose of this study was to determine the clinical features of squamous cell carcinoma (SCC) of the lips, along with its prognostic factors, in order to extend and update the information related to lip cancer in northern Greece and to provide a basis for international comparison. Records of 1510 patients with SCC of the oral cavity presented at the Theagenion Anticancer Institute of Thessaloniki, Greece from 1979 and 1989 were reviewed. The most common site for oral squamous cell carcinoma (OSCC) was found to be the lips (59.4%) as compared to 40.5% of intra-oral SCC. Males were affected more frequently, presenting a ratio of 9.2:1. The peak age of incidence was found to be the 6th decade for men and the 8th for women. Rural residents and outdoor workers were affected more than urban residents (79.9% versus 28.1%). Most of the patients were diagnosed in early categories and early clinical stages of the disease. Almost all (98.5%) were classified into T1 and T2 categories, and 92.9% into stages I and II. A total of 7.59% of patients presented with clinically-positive lymph-node involvement. Most of them were classified as an advanced stage of the disease. Primary surgical excision was performed on 60.14%, radiotherapy on 35.14%, a combination of these on 2.47%, and chemotherapy alone or in combination with the above regimens in 2.22% of the cases. The outcome was adequate for surgery, radiotherapy, and the combination of the two, since 91.3, 74, and 90%, respectively, survived for more than 5 years. An overall 5-year survival rate of 83.3% was found. Our findings showed that the survival rate was significantly influenced by the main prognostic factors, such as the size of the tumour, the lymph-node involvement, the clinical stage of the disease and the histologic differentiation. SCC of the lips continues to be the most common site of oral cancer development amongst the Greek population. The aetiologic significance of actinic radiation for SCC of the lips is confirmed by our findings. The main prognostic factors proved to significantly influence the survival of our patients. Our results support the fundamental principal of head and neck cancer, i.e. that early detection of the primary tumour is the best prognostic factor for increasing survival rates. Therefore, public awareness concerning the disease, and better education for health care workers which will provide a thorough knowledge for the prognosis of oral cancer and the factors influencing it, is necessary.

The RNA component of human telomerase

Eukaryotic chromosomes are capped with repetitive telomere sequences that protect the ends from damage and rearrangements. Telomere repeats are synthesized by telomerase, a ribonucleic acid (RNA)-protein complex. Here, the cloning of the RNA component of human telomerase, termed hTR, is described. The template region of hTR encompasses 11 nucleotides (5'-CUAACCCUAAC) complementary to the human telomere sequence (TTAGGG)n. Germline tissues and tumor cell lines expressed more hTR than normal somatic cells and tissues, which have no detectable telomerase activity. Human cell lines that expressed hTR mutated in the template region generated the predicted mutant telomerase activity. HeLa cells transfected with an antisense hTR lost telomeric DNA and began to die after 23 to 26 doublings. Thus, human telomerase is a critical enzyme for the long-term proliferation of immortal tumor cells.

Cancer in older persons. Magnitude of the problem--how do we apply what we know?

The elderly experience the major impact of cancer. The incidence rate for those aged 65 and older is 2085.3 per 100,000 as compared with 193.9 per 100,000 for those younger than 65. Overall, 58% of all cancer incidence is in the older segment of the population. Cancer mortality in the elderly now accounts for 67% of all cancer deaths. Data from the National Cancer Institute Surveillance, Epidemiology, and End Results program for 1985-1989 reveal many salient facts. Older persons have a risk of developing cancer 10 times greater than that for individuals younger than 65. This paper outlines the magnitude of the major cancers that affect the elderly. Incidence and mortality data are presented according to individual tumors (colon, rectum, lung/bronchus, pancreas, stomach, urinary bladder, breast, ovary, and prostate). Demographic data from the U.S. Bureau of the Census focus on the expanding elderly population in the United States and projections for the future. Needs for cancer care and treatment for the elderly, already great, are likely to increase. It is imperative that older persons receive special attention for cancer prevention, early diagnosis, and treatment efforts, especially because there is almost always an overlay of other chronic diseases and age-associated declines concurrent with the diagnosis of cancer in the elderly. This paper highlights issues unique to older persons as individuals at high risk for cancer and suggests research strategies that should be made in anticipation of the even greater cancer burden for the elderly as this subset of the population expands.