Isabella Orozco's GOx Aptamer Project (2016)

Breast cancer is the formation of a malignant tumor in the breasts. This cancer causes more deaths in the United States among women that any other cancer. In fact, 1 in 8 women will be diagnosed with breast cancer at some point in their lives (National Institutes of Health, 2012). In past years, risk factors identified for breast cancer included genetics, age, and personal factors such as beginning one’s menstrual period at an early age or beginning menopause at a late age.

Recently, newer studies have linked the high levels of a growth hormone known as insulin-like growth factor 1 as a risk factor for breast cancer. This growth hormone is produced in the liver in response to the production of somatotropin in the anterior pituitary gland. IGF-1 influences systemic growth in skeletal muscle, bone, liver, kidney, nerve, hematopoietic cells etc. IGF-1 can also regulate cell growth and development as well as cellular DNA synthesis (Christopoulos, Panagiotis F., Msaouel, Pavlos and Koutsilieris, Michael, 2015). Because IGF-1 has also been known to aid in the metastasis of malignant tumors, researchers believe the body utilizes insulin-like growth factor binding protein 3, which functions as an inhibitory protein to IGF-1, as a protective measure to regulate the activity of IGF-1 (Christopoulos, Panagiotis F., Msaouel, Pavlos and Koutsilieris, Michael, 2015). Studies have shown that it is in fact the high ratios of IGF-1 to IGFBP-3 that demonstrate a positive influence on increasing risks of breast cancer (The Endogenous Hormones and Breast Cancer Collaborative Group, 2010). The use of the ratio of IGF-1 to IGFBP-3 as an indicator for a risk of breast cancer has shown promising results. With the use of this indicator, breast cancer can be more accurately predicted and with success, invasive cancer can be prevented. There is currently already a standard blood test for IGF-1 in place but there is a lack of a standard blood test for IGFBP-3.

Glucose oxidase is a dimeric enzyme with two polymeric subunits each weighing approximately 80 kDa. This is a flavo-dependent enzyme that catalyzes the oxidation of beta-D-glucose to form gluconic acid and hydrogen peroxide. Glucose oxidase is one of the three main enzymes that contribute towards the function of glucometers. The concentration of glucose in the blood can be measured by measuring the concentration of hydrogen peroxide (Eun-Hyung Yoo and Soo-Youn Lee, 2010). This enzyme has a wide variety of other uses such as antibiotic activity, and food preservation due to the production of hydrogen peroxide (McDowall, 2006). Glucose oxidase can also be used to produce a colorimetric response through the breakdown of hydrogen peroxide into oxygen and water. Oxygen would then react with an oxygen accepter that would then be converted to a colored compound and allow the concentration to be measure colorimetrically.

An aptamer is an oligonucleotide sequence with a high binding affinity to a target. Aptamers have recently been developed as an alternative to antibodies because of the stability of RNA over proteins and their inexpensive development. Applications for aptamers include biomarker discovery, in vitro diagnosis, in vivo imaging, target inhibition, and many more. With the use of glucose oxidase and its function as a reporter molecule, a standard blood test can be developed for insulin-like growth hormone binding protein 3. By the use of an in-vitro bead-based selection using the SELEX process, an aptamer against glucose oxidase and an aptamer against IGFBP-3 will be developed to create an indirect ELISA. This will allow the concentration of insulin-like binding protein 3 to be identified in the blood. With the creating of a blood test for this protein, women can be tested for a risk of breast cancer and reduce the likelihood of the metastasis of a malignant tumor.

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References

"Breast Cancer Risk in American Women." National Cancer Institute. N.p., 24 Sept. 2012. Web. 29 July 2016.

Christopoulos, Panagiotis F., Pavlos Msaouel, and Michael Koutsilieris. "Molecular Cancer." The Role of the Insulin-like Growth Factor-1 System in Breast Cancer. BioMed Central, 15 Feb. 2015. Web. 29 Jul. 2016.

McDowall, Jennifer. "Glucose Oxidase and Biosensors." EMBL European Bioinformatics Institute. RCBS Protein Data Bank, May 2006. Web. 01 Aug. 2016.

The Endogenous Hormones and Breast Cancer Collaborative Group. "Insulin-like Growth Factor 1 (IGF1), IGF Binding Protein 3 (IGFBP3), and Breast Cancer Risk: Pooled Individual Data Analysis of 17 Prospective Studies." The Lancet Oncology. Lancet Pub. Group, June 2010. Web. 01 Aug. 2016.

"U.S. Breast Cancer Statistics | Breastcancer.org." Breastcancer.org. N.p., 23 June 2016. Web. 03 Sept. 2016.

vlab.amrita.edu,. (2012). Estimation of blood glucose by Glucose oxidase method. Retrieved 30 July 2016.

Yoo, Eun-Hyung, and Soo-Youn Lee. "Glucose Biosensors: An Overview of Use in Clinical Practice." Sensors (Basel, Switzerland). Molecular Diversity Preservation International (MDPI), 4 May 2010. Web. 01 Aug. 2016.