Breast cancer – gene expression

Sarah was devastated when she received a diagnosis of breast cancer. It did not seem to run in her family, so she assumed she did not have to worry about it. She is grateful for the support of her friends, especially Molly, who is a clinical lab pathologist. Molly is helping her think about the difficult decisions about how aggressive her treatment should be, in terms of surgery, chemotherapy, etc. She explained that the oncologist recommended running a lab test that uses a microarray to measure the expression of specific genes. The pattern of gene expression can predict how quickly the tumor cells will grow and whether they will respond to treatments. Sarah is meeting with the oncologist to review the results, and she has asked Molly to go with her.

Researchers have identified genes whose increased expression is associated with increased proliferation, or rapid growth in breast cancer tumors: Ki-67, STK15, Survivin, Cyclin B1, MYLB2. Other genes are associated with increased tumor cell invasion if their expression is increased: Stomelysin 3 and Cathepsin L2. Some breast cancers cells respond to the hormone estrogen by proliferating, which provides a possible mechanism for treatment since estrogen receptors can be blocked. Increases in the expression of estrogen receptor genes might indicate these cells are responsive to the hormone.

A microarray will be used to compare the levels of gene expression, indicated by fluorescence intensity corresponding to specific gene probes, in the sample from Sarah’s normal breast epithelium to a sample of the tumor tissue. Click here for more information about microarrays.

Run the microarray

Questions:

• What genes are elevated in the tumor tissue? What genes are decreased?
• What are the function of the genes with the most significant difference in expression between normal and tumor tissue?
• Does that pattern of gene expression provide any information about Sarah’s prognosis or treatment possibilities?