MammostratTM, developed by Applied Genomics[1], is a five-antibody prognostic test for estrogen receptor-expressing, hormone-receptor treated (tamoxifen)breast cancer patients with node-negative disease. The test performed by the Molecular Profiling Institute[2], Phoenix, AZ.
Procedure
editStandard paraffin-embedded tissue is stained with five monoclonal antibodies to determine a Risk Index (RI).1 The RI classifies patients into one of three risk categories: low-, moderate-, or high-risk of recurrence based on validated criteria. Postmenopausal patients in the low-risk category have a seven-percent probability of distant recurrence over a 10-year period1
Development and Clinical Validation
editThe technology used in the Mammostrat test was developed by Applied Genomics, Inc.[3] in collaboration with Stanford University. Initially, a large series of antibodies was tested for its ability to predict breast cancer recurrence in a patient cohort from the Clearview Cancer Institute. Five antibodies from this series were selected as the best predictors when analyzed together. This antibody panel was then validated using independent cohorts from the British Columbia Cancer Center, the Cleveland Clinic Foundation, and the University of Alabama at Birmingham. The development and institutional validation studies were published in the Journal of Clinical Oncology in July of 2006.
The definitive Mammostrat validation was performed by Applied Genomics, Inc.[4] using samples from the National Surgical Adjuvant Breast and Bowel Project (NSABP)[5] B14 and B20 clinical trials of adjuvant therapy for node-negative breast cancer.
How Does Mammostrat Work?
editMammostrat categorizes a breast cancer patient into a distinct risk group by measuring the expression of the five selected proteins in the patient's tumor. The expression levels of these proteins are combined to assess the patient's risk of recurrence. These biomarkers were selected by a rigorous process that entailed the screening of hundreds of gene candidates.
Mammostrat Biomarkers
editp53 is known to play a central role in cell cycle regulation and mutations in p53 can contribute to tumor formation.
HTF9C is coexpressed with proteins that are involved in DNA replication, implicating HTF9C in DNA replication and cell cycle regulation.
CEACAM5 is normally expressed in embryonic tissue and is aberrantly expressed in some cancers.
NDRG1 is expressed under conditions of hypoxia and other stresses. It may have a role in helping tumors survive under the hypoxic, stressful environment confronting agressive tumors.
SLC7A5 is involved in nutrient transport. Overexpression of SLC7A5 could help sustain the high growth rate of cancer cells by increasing their ability to consume nutrients.
How is Mammostrat Testing Performed?
editMammostrat is performed on samples submitted either as a paraffin block or eight unstained slides. The block or slides are sent to the Molecular Profiling Institute[6] for testing.
Sources
edit1. Ross, D.T., et al. "Validation of a prognostic algorithm based upon a five-antibody immunohistochemisty test in tamoxifen-treated, node-negative breast cancer: NSABP B14 and B20 studies." Annual San Antonio Breast Cancer Symposium, San Antonio, TX, December 2006.
2. Ring, B.Z., et al. 2006. Novel prognostic immunohistochemical biomarker panel for estrogen receptor-positive breast cancer. Journal of Clinical Oncology 24(19):3039-47