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Pathology

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GIT

Question
46 out of 53
 

Colon carcinoma is associated with all except: (LQ)



A Rb

B Mismatch repair genes

C APC

D B-catenin

Ans. A RB

Two distinct genetic pathways are described in adenocarcinoma of colon:

Adenoma-carcinoma sequence: lt accounts for 80% of sporadic colon cancers. Mutation of APC gene occurs early or is inherited Whenever second allele of APC is mutated or inactivated, B-catenin accumulates [APC protein degrades B-catenin]. Beta-catenin translocates to nucleus and activates genes like myc and cyclin D1. Additional mutations occuring later are:

Kras

SMAD-2 and SMAD-4

p53

Microsatellite instability pathway: Mutations in DNA mismatch repair genes (MSH2 and MLHl) results in expansion of This microsatellite instability may result in decreased functioning of TGF- F type ll and bax proteins. Mutations in BRAF and silencing of genes by hypermethylation may also occur. Kras and p53 are not typically mutated.

Some people were of the opinion that Rb was not the option but the option in the exam was K-RAS. In such a situaticrr*can understand that the answer would be none.

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