Researchers have discovered that cancer cells expressing Her2 gene are often sen

Question

Researchers have discovered that cancer cells expressing Her2 gene are often sensitive to the drug trastuzumab, but not cancer cells that lack Her2 expression. You have obtained a sample of mRNA isolated from a patient's breast tumor.   

a) Name an assay that you can perform with the sample to determine whether or not her doctor should recommend trastuzumab treatment.

b) What makes your assay specific for Her2?

c) Describe or sketch the possible assay results and corresponding treatment recommendation.

Explanation / Answer

ANSWER:

A) HercepTest

The most common test, accounting for 80% of HER2 assessments in the United States, is the HercepTest, manufactured by Dako, in Glosgrup, Denmark. Approved concurrently with trastuzumab.

The HercepTest is based on immunohistochemical (IHC) methods—clinicians using it evaluate staining reactions between HER2 proteins and an antibody on slides of breast tissue.

B) HER2 is a receptor on the surface of all breast cells. To assess HER2 status, those running the test look for binding reactions (or signals) between the genes and a red fluorescent tag. Elevated HER2 more than two binding signals suggests positivity, but cancer cells can also have aneuploid chromosomes, meaning that all their DNA, including their HER2 genes, are amplified.

C) The location of HER2 on the cell surface has contributed to its appeal as an immunotherapy target. Trastuzumab has provided a distinct therapeutic advantage in not only breast cancer but in other tumor types.

A positive finding is contingent on staining intensity, which ranges from 0 (negative) to 1+ (weakly positive) to 2+ (moderately positive) and finally to 3+ (strongly positive).

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