Genetic diversity, inbreeding and cancer

Authors: Beata Ujvari, Marcel Klaassen, Nynke Raven, Tracey Russell, Marion Vittecoq, Rodrigo Hamede, Frédéric Thomas, Thomas Madsen

SourceProceedings of the royal society B, Volume 285, issue 1875, 28 March 2018

Brief summary of the paper: Genetic diversity is essential for adaptive capacities, providing organisms with the potential of successfully responding to intrinsic and extrinsic challenges. Although a clear reciprocal link between genetic diversity and resistance to parasites and pathogens has been established across taxa, the impact of loss of genetic diversity by inbreeding on the emergence and progression of non-communicable diseases, such as cancer, has been overlooked.

Here we provide an overview of such associations and show that low genetic diversity and inbreeding associate with an increased risk of cancer in both humans and animals. Cancer being a multifaceted disease, loss of genetic diversity can directly (via accumulation of oncogenic homozygous mutations) and indirectly (via increased susceptibility to oncogenic pathogens) impact abnormal cell emergence and escape of immune surveillance.

The observed link between reduced genetic diversity and cancer in wildlife may further imperil the long-term survival of numerous endangered species, highlighting the need to consider the impact of cancer in conservation biology.

Finally, the somewhat incongruent data originating from human studies suggest that the association between genetic diversity and cancer development is multifactorial and may be tumour specific. Further studies are therefore crucial in order to elucidate the underpinnings of the interactions between genetic diversity, inbreeding and cancer.

The importance of cancer cells for animal evolutionary ecology

Authors: Frédéric Thomas, Camille Jacqueline, Tazzio Tissot, Morgane Henard, Simon Blanchet, Géraldine Loot, Erika Dawson, Frédéric Mery, François Renaud, Jacques Montagne, Christa Beckmann, Peter A. Biro, Rodrigo Hamede & Beata Ujvari

Source: Nature Ecology & Evolution, Vol 1, Nov 2017

Brief summary of the paper: Reciprocal interactions between hosts, their symbionts and their oncobiota (cancer cell communities) are yet to be studied in detail. Considering malignant cells in addition to the holobiont perspective allows greater understanding of the processes governing both host phenotypes and cancer dynamics.

Oncogenesis as a Selective Force: Adaptive Evolution in the Face of a Transmissible Cancer

Nynke R., Thomas M. and Beata U.

Authors: Tracey Russell, Thomas Madsen, Frédéric Thomas, Nynke Raven, Rodrigo Hamede & Beata Ujvari

Source: BioEssays, Volume 40, Issue 3, March 2018

Brief summary of the paper: Similar to parasites, malignant cells exploit the host for energy, resources and protection, thereby impairing host health and fitness. Although cancer is widespread in the animal kingdom, its impact on life history traits and strategies have rarely been documented.

Devil facial tumour disease (DFTD), a transmissible cancer, afflicting Tasmanian devils (Sarcophilus harrisii), provides an ideal model system to monitor the impact of cancer on host life‐history, and to elucidate the evolutionary arms‐race between malignant cells and their hosts.

Here we provide an overview of parasite‐induced host life history (LH) adaptations, then both phenotypic plasticity of LH responses and changes in allele frequencies that affect LH traits of Tasmanian devils in response to DFTD are discussed.

We conclude that akin to parasites, cancer can directly and indirectly affect devil LH traits and trigger host evolutionary responses. Consequently, it is important to consider oncogenic processes as a selective force in wildlife.

Faced with extinction, the devils fight back

Devil with DFTD

The researchers looked at animals at risk of catching transmissible cancer, known as devil facial tumour disease (DFTD), which has been driving the species toward possible extinction over the past two decades, and found unexpected signs of immunity, including elevated levels of certain immune system molecules which reduce their likelihood of getting the disease.

Active immune responses to DFTD and even tumour regression have recently been observed in several animals, showing a very promising sign that could be exploited for the management of the species,” says lead author Beata Ujvari from Deakin University’s School of Life and Environmental Sciences in Melbourne, Australia.

Read all about it: Research finds clues that Tasmanian devils are adapting to the cancer that threatens their existence by Andrew P Street @ Cosmos – The Science of Everything.

Evolved Dependence in Response to Cancer

Authors: Frédéric Thomas, Irina Kareva, Nynke Raven, Rodrigo Hamede, Pascal Pujol, Benjamin Roche & Beata Ujvari

Source: Trends in Ecology and Evolution (Available online 20 February 2018)

Brief summary of the paper: Evolved dependence is frequent in evolutionary interactions between hosts and parasites. Similar to pathogens, oncogenic manifestations drive host adaptive responses. Multicellular organisms display evolved dependence in response to oncogenic processes. Evolved dependence in response to cancer has implications for prevention and treatment.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Evolved dependence is a process through which one species becomes ‘dependent’ on another following a long evolutionary history of interaction. This happens when adaptations selected in the first species for interacting lead to fitness costs when the second species is not encountered.

Evolved dependence is frequent in host–parasite interactions, where hosts may achieve a higher fitness in the presence of the parasite than in its absence. Since oncogenic manifestations are (i) ubiquitous across multicellular life, (ii) involved in parasitic-like interactions with their hosts, and (iii) have effectively driven the selection of numerous adaptations, it is possible that multicellular organisms display evolved dependence in response to oncogenic processes.

We provide a comprehensive overview of the topic, including the implications for cancer prevention and treatment.

Cancer Is Not (Only) a Senescence Problem

Authors: Frédéric Thomas, Fabrice Vavre, Tazzio Tissot, Marion Vittecoq, Mathieu Giraudeau, Florence Bernex, Dorothée Misse, François Renaud, Nynke Raven, Christa Beckmann, Rodrigo Hamede, Peter A. Biro & Beata Ujvari

Source: Trends in Cancer, Volume 4, Issue 3, p169–172, March 2018

Brief summary of the paper: Age is one of the strongest predictors of cancer and risk of death from cancer. Cancer is therefore generally viewed as a senescence-related malady.

However, cancer also exists at subclinical levels in humans and other animals, but its earlier effects on the body are poorly known by comparison.

We argue here that cancer is a significant but ignored burden on the body and is likely to be a strong selective force from early during the lifetime of an organism. It is time to adopt this novel view of malignant pathologies to improve our understanding of the ways in which oncogenic phenomena influence the ecology and evolution of animals long before their negative impacts become evident and fatal.

Turning natural adaptations to oncogenic factors into an ally in the war against cancer

Beata U.

Authors: Marion Vittecoq, Mathieu Giraudeau, Tuul Sepp, David J. Marcogliese, Marcel Klaassen, François Renaud, Beata Ujvari & Frédéric Thomas

Source: Evolutionary Applications (14 March 2018)

Brief summary of the paper: Both field and experimental evolution studies have demonstrated that organisms naturally or artificially exposed to environmental oncogenic factors can, sometimes rapidly, evolve specific adaptations to cope with pollutants and their adverse effects on fitness.

Although numerous pollutants are mutagenic and carcinogenic, little attention has been given to exploring the extent to which adaptations displayed by organisms living in oncogenic environments could inspire novel cancer treatments, through mimicking the processes allowing these organisms to prevent or limit malignant progression.

Building on a substantial knowledge base from the literature, we here present and discuss this progressive and promising research direction, advocating closer collaboration between the fields of medicine, ecology, and evolution in the war against cancer.

Cancer adaptations: Atavism, de novo selection, or something in between?

Authors: Frédéric Thomas, Beata Ujvari, François Renaud, Mark Vincent

Source: BioEssays Volume 39, Issue 8, August 2017

Brief summary of the paper: From an evolutionary perspective, both atavism and somatic evolution/convergent evolution theories can account for the consistent occurrence, and astounding attributes of cancers: being able to evolve from a single cell to a complex organized system, and malignant transformations showing significant similarities across organs, individuals, and species.

Here, we first provide an overview of these two hypotheses, including the possibility of them not being mutually exclusive, but rather potentially representing the two extremes of a continuum in which the diversity of cancers can emerge.

In reviewing the current literature, we also discuss the criteria that should be applied to discriminate between the two competing theories and to determine their relevant contributions to oncogenesis and cancer progression.

Finally, we deliberate on the potential applications of this conceptual framework in developing novel treatment strategies.

Changes in diet associated with cancer: An evolutionary perspective

Beata U.

Authors: Frédéric Thomas, Sophie Rome, Frédéric Mery, Erika Dawson, Jacques Montagne, Peter A. Biro, Christa Beckmann, François Renaud, Robert Poulin, Michel Raymond, Beata Ujvari

SourceEvolutionary Applications, Volume 10, Issue 7, Pages 651–657, August 2017

Brief summary of the paper: Changes in diet are frequently correlated with the occurrence and progression of malignant tumors (i.e., cancer) in both humans and other animals, but an integrated conceptual framework to interpret these changes still needs to be developed.

Our aim is to provide a new perspective on dietary changes in tumor-bearing individuals by adapting concepts from parasitology. Dietary changes may occur alongside tumor progression for several reasons: (i) as a pathological side effect with no adaptive value, (ii) as the result of self-medication by the host to eradicate the tumor and/or to slow down its progression, (iii) as a result of host manipulation by the tumor that benefits its progression, and finally (iv) as a host tolerance strategy, to alleviate and repair damages caused by tumor progression.

Surprisingly, this tolerance strategy can be beneficial for the host even if diet changes are beneficial to tumor progression, provided that cancer-induced death occurs sufficiently late (i.e., when natural selection is weak).

We argue that more data and a unifying evolutionary framework, especially during the early stages of tumorigenesis, are needed to understand the links between changes in diet and tumor progression. We argue that a focus on dietary changes accompanying tumor progression can offer novel preventive and therapeutic strategies against cancer.

What can Tasmanian devils teach us about cancer?

Something extraordinary is evolving among the feisty inhabitants of the remote north-west coast of Tasmania. Something that’s both astounding and delighting the researchers monitoring them.

For more than 20 years, these apple-isle locals have been suffering an ugly cancer that’s caused population numbers to rapidly decline. The problem has raised many complex questions and stirred urgent conservation efforts among research institutions around the world. But now, in an unprecedented and ground-breaking discovery, an isolated colony of Tasmanian devils appear to be saving themselves from extinction.

Having immersed herself and her research in the devil’s world for a number of years, Dr Beata Ujvari, an evolutionary ecologist and Senior Lecturer in Bioinformatics and Genetics at Deakin University, is excited by the new findings. ‘Encouragingly, the results suggest the devils may be able to overcome the extinction threat of the disease that has devastated the population for over two decades.’

Read more on this new and exciting research by Dr Beata Ujvari via Deakin (this.)