Enzyme promoting recurrent colorectal adenoma! - USMLE Forums
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  #1  
Old 11-27-2011
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GIT Enzyme promoting recurrent colorectal adenoma!

A 65-year-old Caucasian female had her sigmoid colon resected after an adenoma with severe dysplasia was discovered. Her carcinoembryonic antigen (CEA) level and liver ultrasonography are normal one year later. Which of the following enzyme activities is most likely to promote recurrent adenoma development in this patient?

A. Xanthine oxydase
B. Cyclooxygenase —2
C. Phospholipase C
D. Angiotension converting enzyme
E. NO synthase
F. Superoxide dismutase
G. Caspase
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  #2  
Old 11-27-2011
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I think its B. I read once something about COX 2 being associated with colon malign.
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Old 11-27-2011
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ill 2 go wit B. COX 2 related 2 inflmation

superoxide is wit free radical injury
caspase is antiapoptic
so cod b still wit go wit B
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Old 11-29-2011
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i guess b too
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Old 11-29-2011
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Sure its B its from uw !
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Old 11-30-2011
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B. Cyclooxygenase —2
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  #7  
Old 11-30-2011
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definitely B,that's y aspirin decreases it's incidence , ,
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Old 11-30-2011
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Correct Answer you guys are set :)

Explanation:
Adenomatous polyps contain dysplastic mucosa and are considered premalignant. They tend to develop in people older than 50 years old as a result of APC gene mutation. Stepwise progression to adenocarcinoma may follow. This progression includes a series of other gene mutations, such as R-ras, p53 and DCC. This accumulation of gene mutations is called the “adenoma-to-carcinoma sequence”.
The best prevention of malignant transformation of adenomatous polyps is regular screening and timely excision of adenomas. Recent studies, however, have shown increased activity of enzyme cyclooxygenase-2 (COX-2) in some colon adenocarcinomas and in inherited polyposes syndromes. Patients taking NSAIDs regularly have been shown to have a lower incidence of adenomas compared to the general population, perhaps because of the COX-2 inhibitory effect of NSAIDs. The full effects of the COX-2 enzyme (and its modification) are still under investigation.
(Choice A) Xanthine oxidase is an enzyme that participates in the synthesis of uric acid. Allopurinol is a xanthine oxidase inhibitor. It is used to lower levels of serum uric acid in gout and tumor lysis syndrome.
(Choice D) Angiotensin-converting enzyme (ACE) converts angiotensin into angiotensin II, which plays an important role in pathogenesis of hypertension and congestive heart failure. ACE inhibitors are widely used.
Phospholipase C (Choice C), NO synthase (Choice E), superoxide dismutase (Choice F), and caspase (Choice G) are not found to play any role in the development of adenomatous polyps.

Educational Objective:
Adenomatous polyps contain dysplastic mucosa and are premalignant. Screening for polyps with excision is an effective prevention of colon adenocarcinoma. Recent discoveries suggest that COX-2 inhibitors may decrease adenomatous polyp formation.
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  #9  
Old 12-01-2011
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my guess is B, COX-2
Multiple trials have proven that long term treatment with NSAIDs are associated with a reduced incidence of adenomas and colorectal cancer.
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Gastrointestinal-Tract-, Molecular-Biology-, Pathology-, Pharmacology-, Step-1-Questions

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