'FAP' AND COLON CANCER

In the 'FAP' Associated Model , spontaneous cases of 'Colon Cancer' begin with a Mutation in the APC gene. Which maps to the long arm of chromosome 5 .

 This mutation occurs in a normal epithelial cell in the living of the colon ,In spontaneous causes ,an APC Mutation causes epithelial cells to partially escape cell cycle control .These cells divide to form a small cluster called polyp .those who inherit a mutant APC allele have the mutation in all cells of their body .As a result , APC Hetero Zygotes from hundreds or thousand of polyps .

   In either case ,polyps are clones ,all of which carry an APC Mutation .The loss of corresponding allele on the homologous copy of Chromosome 5 is not necessary for polyp formation .The first step and the relative order of subsequent mutations .Subsequent Mutations in polyp cells causes Intermediate stages of tumor formation .Mutations in the ras onco gene on chromosome 12 ,cause polyp to grow larger and to devlop finger like outgrowths .This is the Intermediate adenoma stage .

  To progress further ,a polyp cell must acquire Mutations in the DCC (Detected Colon Cancer) gene on chromosome 18 .
Mutations in both DCC alleles results in late - stage adeno-mas .Finally ,Mutation of the p53 gene causes the transition to a cancerous call .As described earlier , Mutations in p53 are pivotal to cancers including LUNG ,BRAIN as well as Colon Cancer .
Metastasis occurs after the formation of Colon Cancer ,and it's involves an unknown number of Mutational steps .