Freebase(0.00 / 0 votes)Rate this definition: Arbol is a programming language which has been primarily developed for use in Genetic Programming experiments. It is a functional programming language inspired by the ideas of other small and esoteric languages.
Causes. In most cases of colon or rectal cancers, the cause or causes are unknown. Defects in genes that normally protect against cancer play the major role in causing polyp cells to continuously change and become cancerous.
Mutations in either the EGFR or KRAS gene lead to the production of a protein that is constantly turned on (constitutively activated). As a result, cells are signaled to constantly proliferate, leading to tumor formation. When these gene changes occur in cells in the lungs, lung cancer develops.