Clonally transmissible cancer
A transmissible cancer is a
General mechanism
Transmissible cancers require a specific combination of related circumstances to occur. These conditions involve both the host species and the tumors being transferred. These typically include, low genetic diversity among individuals, effective physical and environmental transport system, effective dose of infective material and ideal micro-environments.[4] The cancers reproduce faster in larger quantities with different means of reproduction tend to be favored for transmission if host conditions are met. Transmissible cancers follow the general pattern of cancer spread, starting with the growth of primary cancer cells at tumor sites followed by invasion of surrounding tissue and subsequent spread throughout the organism.[5] The main hurdles for surviving cells of a successful spread to a new host are histocompatibility barriers. The cancers have to bypass the self recognition system, survive the difference in nutrients and induce the correct response in the new hosts to begin the cycle anew.[6]
Transmissible cancers behave as true parasites, relying primarily on transport systems like direct contact, environmental transport and vectors, rather than hematogenous and lymphatic carriers to spread between organisms.[4] The amount of shredded cancer cells from initial host has to be high enough to increase survival probability. Direct contact transmissions through sexual or general contact such as in DFTD and CVTD ensures a higher potential for transmission.[4] Population factors also play an important role. A dense population of available and uninfected potential hosts is ideal for the tumors given the complexity and difficulty of the overall process, hence its virulence and potency must be adequately controlled.[3]
Humans
In humans, a significant fraction of Kaposi's sarcoma occurring after transplantation may be due to tumorous outgrowth of donor cells.[7] Although Kaposi's sarcoma is caused by a virus (Kaposi's sarcoma-associated herpesvirus), in these cases, it appears likely that transmission of virus-infected tumor cells—rather than the free virus—caused tumors in the transplant recipients.[2]
In 2007, four people (three women and one man) received different
In 2014, a case of parasite-to-host cancer transmission occurred in a 41-year-old man in Colombia with a compromised immune system due to
Other animals
Contagious cancers are known to occur in
Clonally transmissible cancer, caused by a clone of malignant cells rather than a
Canine transmissible venereal tumor
Canine transmissible venereal tumor (CTVT) is sexually transmitted cancer which induces cancerous tumors on the genitalia of both male and female dogs, typically during mating. It was first described medically by a veterinary practitioner in London in 1810.[19] It was experimentally transplanted between dogs in 1876 by M. A. Novinsky (1841–1914). A single malignant clone of CTVT cells has colonized dogs worldwide, representing the oldest known malignant cell line in continuous propagation,[20] a fact that was uncovered in 2006. Researchers deduced that the CTVT went through 2 million mutations to reach its actual state, and inferred it started to develop in ancient dog species 11 000 years ago.[19]
Contagious reticulum cell sarcoma
Devil facial tumour disease
Devil facial tumour disease (DFTD) is a transmissible parasitic cancer in the Tasmanian devil.[23] Since its discovery in 1996, DFTD has spread and infected 4/5 of all Tasmanian devils and threatens them with extinction. DFTD has a near 100% fatality rate, and has killed up to 90% of Tasmanian devil populations living in some reserves.[24] A new DFTD tumor-type cancer was recently uncovered on 5 Tasmanian devils (DFT2), histologically different from DFT1, leading researchers to believe that the Tasmanian devil "is particularly prone to the emergence of transmissible cancers".[19]
Bivalves
Soft-shell clams, Mya arenaria, have been found to be vulnerable to a transmissible neoplasm of the hemolymphatic system — effectively, leukemia.[25][26] The cells have infected clam beds hundreds of miles from each other, making this clonally transmissible cancer the only one that does not require contact for transmission.[19]
Horizontally transmitted cancers have also been discovered in three other species of marine
See also
- Allotransplantation
- Anne-Maree Pearse, originator of the allograft theory of transmissible cancer
- Myxosporea – SCANDAL hypothesis
References
- ^ PMID 26686413.
- ^ PMID 21212437.
- ^ PMID 32592998.
- ^ PMID 26861618.
- PMID 19308067.
- PMID 18059462.
- S2CID 2527251.
- PMID 29633548.
- PMID 26535513.
- PMID 8890100.
- PMID 3785302.
- PMC 1717007.
- PMID 28948233.
- PMID 19453727.
- S2CID 21195930.
- PMID 31371581.
- S2CID 8303843.
- PMID 17911263.
- ^ a b c d Harrison C (May 2018). "Clonally transmissible cancers in nature". Cancer Therapy Advisor. Retrieved 2019-10-03.
- PMID 16901782.
- PMID 14220251.
- S2CID 12611674.
- ^
Pearse AM, Swift K (February 2006). "Allograft theory: transmission of devil facial-tumour disease". Nature. 439 (7076): 549. S2CID 4409863.
- PMID 27575253.
- National Geographic. Archived from the originalon 2015-09-05. Retrieved 2015-04-10.
- PMID 25860608.
- PMID 27338791.
- PMID 1255763.
External links
- Clonally transmissible cancers Archived 2017-11-15 at the Wayback Machine at plos.org.