User:Daniel Fafemi/Clonally transmissible cancer

A transmissible cancer is a cancer cell or cluster of cancer cells that can be transferred between individuals without the involvement of an infectious agent, such as an Oncovirus. The evolution of transmissible cancer has occurred naturally in other animal species, but human cancer transmission is rare. They transfer between members of the same species or closely related species.

Mechanism
Transmissible cancers require a specific combination of related circumstances to occur. These conditions involve both the host species and the tumors being transferred. They are typically low genetic diversity among individuals, effective physical and environmental transport system, effective dose of infective material and ideal micro-environments. 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. 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.

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. 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. 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.