Can Energetic Capacity Help Explain Why Physical Activity Reduces Cancer Risk?

Authors: Peter A. Biro; FrédéricThomas; Beata Ujvari; Christa Beckmann

Source: Trends in Cancer (June 2020)

Brief summary of the paper:

Physical activity substantially reduces the risk of developing cancer. As such, exercise promises to be a powerful preventative measure against cancer.

However, if we are to ‘prescribe’ exercise, we should identify how and why exercise affects cancer risk to provide informed prescriptions.

We find that high energetic capacity is both a cause and consequence of high sustained activity levels, both at a genetic level and due to training effects.

High energetic capacity in turn can increase immune responses and reduce incidence and progression of cancer, and this effect can be independent of activity. Thus, exercise may reduce cancer risk via increasing one’s energetic capacity for immune function.

In light of this potential mechanism, prescriptions for exercise might consider those likely to increase one’s energetic capacity, which may differ among individuals given innate differences in our ability to generate energy on a sustained basis.

Increased physical activity reduces cancer risk in humans, but why this whole-organism attribute reduces cancer remains unclear. Active individuals tend to have high capacity to generate energy on a sustained basis, which in turn can permit greater immune responses crucial for fighting emerging neoplasia.

Thus, we suggest energetic capacity as a potential mechanism to explain the activity–cancer link, given that humans are intrinsically (not externally) energy limited.

Human and rodent studies show that individuals with high energetic capacity mount greater immune responses and have lower cancer incidence; these trends persist after controlling for actual physical activity, supporting a direct role of energetic capacity.

If true, exercise efforts might best target those that increase one’s energetic capacity, which may be both individual and exercise specific.

Transmissible Cancers in an Evolutionary Perspective

Authors: Antoine M. Dujon, Robert A. Gatenby, Georgina Bramwell, Nick MacDonald, Erin Dohrmann, Nynke Raven, Aaron Schultz, Rodrigo Hamede, Anne-Lise Gérard, Mathieu Giraudeau, Frédéric Thomas & Beata Ujvari

Source: iScience (June 2020)

Brief summary of the paper:

Graphical Abstract:

Inter-individual transmission of cancer cells represents an intriguing and unexplored host-pathogen system, with significant ecological and evolutionary ramifications. The pathogen consists of clonal malignant cell lines that spread horizontally as allografts and/or xenografts.

Although only nine transmissible cancer lineages in eight host species from both terrestrial and marine environments have been investigated, they exhibit evolutionary dynamics that may provide novel insights into tumor-host interactions particularly in the formation of metastases.

Here we present an overview of known transmissible cancers, discuss the necessary and sufficient conditions for cancer transmission, and provide a comprehensive review on the evolutionary dynamics between transmissible cancers and their hosts.

Demography and spatial requirements of the endangered northern quoll on Groote Eylandt

Authors: Jaime Heiniger, Skye F. Cameron, Thomas Madsen, Amanda C. Niehaus and Robbie S. Wilson

Source: Wildlife Research (May 2020)

Pic by: Wildlife Explorer / CC BY (https://creativecommons.org/licenses/by/3.0)

Brief summary of the paper:

Context: Australia has experienced the highest number of mammal extinctions of any continent over the past two centuries. Understanding the demography and spatial requirements of populations before declines occur is fundamental to confirm species trajectory, elucidate causes of decline and develop effective management strategies.

Aims: We evaluated the demography and spatial requirements of a northern quoll, Dasyurus hallucatus, population on Groote Eylandt, Northern Territory. Groote Eylandt is considered a refuge for the species because key threatening processes are absent or limited; cane toads and introduced ungulates are absent, feral cats are infrequently detected and the fire regime is benign compared with mainland Northern Territory.

Methods: We conducted a 4-year capture–mark–recapture study to monitor growth, reproduction and survival of northern quolls within a 128-ha area, and we evaluated spatial requirements by attaching GPS units to both sexes. To assess the status of the Groote Eylandt population, we compared the demographics with existing data from mainland populations.

Key results: The average density of northern quolls was 0.33 ha¯¹. However, there was a 58% decline in female density, primarily between 2012 and 2013, corresponding with a decrease in female body mass. Females survived and bred in up to 3 years and adult survival rates did not vary among years, suggesting that juvenile recruitment drives population fluctuations. Male quolls were semelparous, with die-off occurring in the months following breeding. The median female and male home ranges were 15.7 ha and 128.6 ha respectively, and male ranges increased significantly during breeding, with 1616 ha being the largest recorded.

Conclusions: The northern quoll population on Groote Eylandt had a higher density, female survival and reproductive success than has been previously recorded on the mainland. However, a marked decline was recorded corresponding with a decrease in female mass, indicating below-average rainfall as the likely cause.

Implications: Groote Eylandt remains a refuge for the endangered northern quoll. However, even in the absence of key threatening processes, the population has declined markedly, highlighting the impact of environmental fluctuations. Maintaining the ecological integrity of Groote Eylandt is imperative for population recovery, and managing threats on the mainland over appropriate spatial scales is necessary to increase population resilience.

High numbers of unrelated reproductives in the Australian ‘higher’ termite Nasutitermes exitiosus (Blattodea: Termitidae)

Authors: Montagu, A.; Lee, T. R. C.; Ujvari, B; et al.

Source: INSECTES SOCIAUX

Pic by: Forestry and Forest Products

Brief summary of the paper:

Social insect colonies are among the most complex social organisations in nature, with reproductive and non-reproductive individuals co-ordinating to maintain the survival of the colony.

Multiple reproductive schemes occur in social insects, from simple schemes with one founding reproductive pair, to more complex ones involving within-colony inbreeding and more than two unrelated reproductives.

Colony breeding schemes and genetic structure remain understudied in termites, compared to the Hymenoptera. In this study, we performed the first genetic characterisation of the colony breeding structure of Nasutitermes exitiosus (Blattodea: Termitidae), an endemic Australian termite with a broad distribution across southern mainland Australia.

We analysed the genetic structure of 60 N. exitiosus colonies from the Eastern part of its distribution, using microsatellites and mitochondrial sequence data. We found that most colonies were headed by one founding pair of reproductives, although some colonies exhibited a more complex breeding structure, including within-colony inbreeding and the presence of multiple unrelated reproductives.

We found evidence for the presence of seven unrelated queens in one colony, to our knowledge, the highest number of unrelated queens yet found in a termite from the family Termitidae. We found some evidence for genetic isolation by distance, indicating that the species is a relatively poor disperser over long ranges.

The evolution of resistance and tolerance as cancer defences

Authors: Thomas, Frederic; Giraudeau, Mathieu; Gouzerh, Flora; Boutry, Justine; Renaud, Francois; Pujol, Pascal; Tasiemski, Aurelie; Bernex, Florence; Maraver, Antonio; Bousquet, Emilie; Dormont, Laurent; Osterkamp, Jens; Roche, Benjamin; Hamede, Rodrigo; Ujvari, Beata.

Source: PARASITOLOGY

Brief summary of the paper:

Although there is a plethora of cancer associated-factors that can ultimately culminate in death (cachexia, organ impairment, metastases, opportunistic infections, etc.), the focal element of every terminal malignancy is the failure of our natural defences to control unlimited cell proliferation.

The reasons why our defences apparently lack efficiency is a complex question, potentially indicating that, under Darwinian terms, solutions other than preventing cancer progression are also important contributors. In analogy with host-parasite systems, we propose to call this latter option ‘tolerance’ to cancer.

Here, we argue that the ubiquity of oncogenic processes among metazoans is at least partially attributable to both the limitations of resistance mechanisms and to the evolution of tolerance to cancer.

Deciphering the ecological contexts of alternative responses to the cancer burden is not a semantic question, but rather a focal point in understanding the evolutionary ecology of host-tumour relationships, the evolution of our defences, as well as why and when certain cancers are likely to be detrimental for survival.

Will urbanisation affect the expression level of genes related to cancer of wild great tits?

Authors: Giraudeau, Mathieu; Watson, Hannah; Powell, Daniel; Vincze, Orsolya; Thomas, Frederic; Sepp, Tuul; Ujvari, Beata; et al.

Source: SCIENCE OF THE TOTAL ENVIRONMENT

Brief summary of the paper:

Recent studies suggest that oncogenic processes (from precancerous lesions to metastatic cancers) are widespread in wild animal species, but their importance for ecosystem functioning is still underestimated by evolutionary biologists and animal ecologists.

Similar to what has been observed in humans, environmental modifications that often place wild organisms into an evolutionary trap and/or exposes them to a cocktail of mutagenic and carcinogenic pollutants might favor cancer emergence and progression, if animals do not up-regulate their defenses against these pathologies.

Here, we compared, for the first time, the expression of 59 tumor-suppressor genes in blood and liver tissues of urban and rural great tits (Parus major); urban conditions being known to favor cancer progression due to, among other things, exposure to chemical or light pollution.

Contrary to earlier indications, once we aligned the transcriptome to the great tit genome, we found negligible differences in the expression of anti-cancer defenses between urban and rural birds in blood and liver. Our results indicate the higher expression of a single caretaker gene (i.e. BRCA1) in livers of rural compared to urban birds.

We conclude that, while urban birds might be exposed to an environment favoring the development of oncogenic processes, they seem to not upregulate their cancer defenses accordingly and future studies should confirm this result by assessing more markers of cancer defenses.

This may result in a mismatch that might predispose urban birds to higher cancer risk and future studies in urban ecology should take into account this, so far completely ignored, hazard.

Differences in mutational processes and intra-tumour heterogeneity between organs: The local selective filter hypothesis

Authors: Giraudeau, Mathieu; Sepp, Tuul; Ujvari, Beata; et al.

Source: EVOLUTION MEDICINE AND PUBLIC HEALTH

Brief summary of the paper:

Extensive diversity (genetic, cytogenetic, epigenetic and phenotypic) exists within and between tumours, but reasons behind these variations, as well as their consistent hierarchical pattern between organs, are poorly understood at the moment.

We argue that these phenomena are, at least partially, explainable by the evolutionary ecology of organs’ theory, in the same way that environmental adversity shapes mutation rates and level of polymorphism in organisms.

Organs in organisms can be considered as specialized ecosystems that are, for ecological and evolutionary reasons, more or less efficient at suppressing tumours.

When a malignancy does arise in an organ applying strong selection pressure on tumours, its constituent cells are expected to display a large range of possible surviving strategies, from hyper mutator phenotypes relying on bet-hedging to persist (high mutation rates and high diversity), to few poorly variable variants that become invisible to natural defences.

In contrast, when tumour suppression is weaker, selective pressure favouring extreme surviving strategies is relaxed, and tumours are moderately variable as a result. We provide a comprehensive overview of this hypothesis.

Lay summary: Different levels of mutations and intra-tumour heterogeneity have been observed between cancer types and organs. Anti-cancer defences are unequal between our organs. We propose that mostly aggressive neoplasms (i.e. higher mutational and ITH levels), succeed in emerging and developing in organs with strong defences.

Global meta‐analysis of over 50 years of multidisciplinary and international collaborations on transmissible cancers

Authors: Antoine M. Dujon, Gail Schofield, Georgina Bramwell, Nynke Raven, Rodrigo Hamede, Frédéric Thomas & Beata Ujvari

Source: Evolutionary Applications

Brief summary of the paper: Although transmissible cancers have, so far, only been documented in three independent animal groups, they not only impact animals that have high economic, environmental and social significance, but they are also one of the most virulent parasitic life forms.

Currently known transmissible cancers traverse terrestrial and marine environments, and are predicted to be more widely distributed across animal groups; thus, the implementation of effective collaborative scientific networks is important for combating existing and emerging forms.

Here, we quantify how collaborative effort on the three known transmissible cancers has advanced through the formation of collaborative networks among institutions and disciplines. These three cancers occur in bivalves (invertebrates—disseminated neoplasia; DN), Tasmanian devils (vertebrate—marsupial; devil facial tumour disease; DFTD) and dogs (vertebrate—eutherian mammal; canine transmissible venereal tumour; CTVT). Research on CTVT and DN has been conducted since 1876 and 1969, respectively, whereas systematic research on DFTD only started in 2006.

Yet, collaborative effort on all three diseases is global, encompassing six major Scopus subject areas. Collaborations steadily increased between 1963 and 2006 for CTVT and DN, with similar acceleration for all three cancers since 2006. Network analyses demonstrated that scientists are organizing themselves into efficient collaborative networks; however, these networks appear to be far stronger for DFTD and DN, possibly due to the recent detection of new strains adding impetus to research and associated publications (enhancing citation trajectories).

In particular, global and multidisciplinary collaborations formed almost immediately after DFTD research was initiated, leading to similar research effort and relatively greater research outputs compared to the other two diseases.

Therefore, in the event of outbreaks of new lineages of existing transmissible cancers, or the discovery of new transmissible cancers in the future, the rapid formation of international collaborations spanning relevant disciplines is vital for the efficient management of these diseases.

The potential of marginal coastal nursery habitats for the conservation of a culturally important Caribbean marine species

Authors: Thomas C. Stieglitz, Antoine M. Dujon, Joanne R. Peel, Erwan Amice

Source: Diversity and Distributions

Brief summary of the paper:

Aim: Identifying the potential of marginal habitats for species conservation is of key importance when their core high‐quality habitats are under substantial disturbances and threats. However, there is currently a knowledge gap on how useful marine marginal habitats may be for conserving endangered marine species. Here, we investigate the potential of groundwater‐fed coastal areas for the conservation of the queen conch, an economically and culturally important marine gastropod.

Location: The inlet of Xel‐Há, typical of groundwater‐fed coastal areas widely distributed along the Yucatan Peninsula coast in Mexico and partially protected by a network of marine protected areas.

Methods: We tracked 66 queen conchs (Lobatus gigas) using acoustic telemetry over a period of 3.5 years. We investigated for ontogenetic niche shift using a network analysis and by modelling their growth.

Results: The queen conchs exhibited the same ontogenetic niche shift required to complete their life cycle in this marginal habitat as they do in offshore core habitats. A total of 33 individuals departed the inlet and migrated from shallow groundwater‐affected nursery grounds to deeper marine habitats more suitable for breeding aggregation.

Main conclusions: As the broad‐scale movement behaviour of queen conch in this inlet is similar to that observed on the overfished core habitats, our findings suggest that groundwater‐fed coastal areas should be included in conservation planning for an effective management of this species within a network of marine protected areas.

Rare and unique adaptations to cancer in domesticated species: An untapped resource?

Authors: Thomas, Frederic; Giraudeau, Mathieu; Dheilly, Nolwenn M.; Gouzerh, Flora; Boutry, Justine; Beckmann, Christa; Biro, Peter A.; Hamede, Rodrigo; Abadie, Jerome; Labrut, Sophie; Bieuville, Margaux; Misse, Dorothee; Bramwell, Georgina; Schultz, Aaron; Le Loc’h, Guillaume; Vincze, Orsolya; Roche, Benjamin; Renaud, Francois; Russell, Tracey; Ujvari, Beata

Source: EVOLUTIONARY APPLICATIONS

Brief summary of the paper: Strong and ongoing artificial selection in domestic animals has resulted in amazing phenotypic responses that benefit humans, but often at a cost to an animal’s health, and problems related to inbreeding depression, including a higher incidence of cancer.

Despite high rates of cancer in domesticated species, little attention has been devoted to exploring the hypothesis that persistent artificial selection may also favour the evolution of compensatory anticancer defences.

Indeed, there is evidence for effective anti‐cancer defences found in several domesticated species associated with different cancer types.

We also suggest that artificial selection can favour the “domestication” of inherited oncogenic mutations in rare instances, retaining those associated to late and/or less aggressive cancers, and that by studying these seemingly rare anticancer adaptations, novel cancer treatments may be found.