Transmissible cancers in mammals and bivalves: How many examples are there?

Abstract

Transmissible cancers are elusive and understudied parasitic life forms caused by malignant clonal cells (nine lineages are known so far). They emerge by completing sequential steps that include breaking cell cooperation, evade anti‐cancer defences and shedding cells to infect new hosts. Transmissible cancers impair host fitness, and their importance as selective force is likely largely underestimated. It is, therefore, crucial to determine how common they might be in the wild. Here, we draw a parallel between the steps required for a transmissible cancer to emerge and the steps required for an intelligent civilisation to emerge in the Milky Way using a modified Drake equation. Using numerical analyses, we estimate the potential number of extant marine and bivalve species in which transmissible cancers might exist. Our results suggest that transmissible cancers are more common than expected, and that new lineages can be found by screening a large number of species.

Gut cancer increases the risk forDrosophilato be preyed upon by hunting spiders

“…On the other hand, in the same way that some parasites evolved to manipulate their host to increase transmission to intermediate hosts (Hughes & Libersat, 2019), parasites may have evolved to make their hosts less conspicuous to predation, for example, by interfering with the search for mates or by lessening the effects of the disease on the host; for example, by reducing symptoms. Because cancer progression generally results in the death of the organism, we cannot expect the incidence of lethal cancer to have evolved in the same way as parasites, except for transmissible cancers such as in Tasmanian devils (Dujon, Bramwell, Roche, Thomas, & Ujvari, 2021). We argue that selective predation on prey with cancer may be one of the reasons why tumours are commonly tolerated in animals, where advanced cancer is only rarely detected.…”

Between the Devil and the Deep Blue Sea: Non-Coding RNAs Associated with Transmissible Cancers in Tasmanian Devil, Domestic Dog and Bivalves

“…This contrasts at least nine naturally occurring transmissible cancers in dogs, Tasmanian devils and bivalves that infect multiple individuals in the population (Figure 1). In fact, transmissible cancers may be more common in nature than represented in the literature [11]. The number of bivalve species affected by BTN is likely to be underestimated [11].…”

“…In fact, transmissible cancers may be more common in nature than represented in the literature [11]. The number of bivalve species affected by BTN is likely to be underestimated [11].…”

On the need for integrating cancer into the One Health perspective

“…A second reason for elevating the importance of cancers in the One Health approach concerns cancers that can themselves become transmissible. There are currently nine known transmissible cancer lineages (one in dogs, two in Tasmanian devil populations, and six in marine bivalves; Dujon, Bramwell, et al, 2020 ; Dujon, Gatenby, et al, 2020 ), some of which threaten the survival of animal populations (and species) and are detrimental to ecosystem stability (see, for instance, Hamede et al, 2020 ). Indubitably, this number is a gross underestimate due to poor monitoring of cancer in wildlife (Dujon, Bramwell, et al, 2020 ; Dujon, Gatenby, et al, 2020 ; Dujon, Ujvari, et al, 2020 ; Ujvari et al, 2016 ).…”

“…There are currently nine known transmissible cancer lineages (one in dogs, two in Tasmanian devil populations, and six in marine bivalves; Dujon, Bramwell, et al, 2020 ; Dujon, Gatenby, et al, 2020 ), some of which threaten the survival of animal populations (and species) and are detrimental to ecosystem stability (see, for instance, Hamede et al, 2020 ). Indubitably, this number is a gross underestimate due to poor monitoring of cancer in wildlife (Dujon, Bramwell, et al, 2020 ; Dujon, Gatenby, et al, 2020 ; Dujon, Ujvari, et al, 2020 ; Ujvari et al, 2016 ). The conditions for the emergence of transmissible cancers, while poorly understood, require a perfect storm of sequential steps that is reminiscent of a parasitic lifestyle.…”