Motivation for Sensor bricks
Blood cancer stages a life threatening disease; leukemia is the highest occurring cancer among children and young adults under the age of twenty and in the recent years, it is even estimated to strike adults ten times more than children. The current detection systems are lengthy and not precise, which leads to the progress of the disease instead of taking immediate therapeutic actions. In our project we tackled some of the problems by producing a senisitve and fast detection system.
Due to its expression on normal myeloid cells and its presence on tumor cells of 85% to 90% of adult patients with acute myeloid leukemia (AML), CD33 has been exploited as a target for antibody based – AML therapies. During the past years, several receptors have been discovered in spite of the limited information that existed on the possible functions of CD33. Various identified surface molecules have been known to represent useful markers for cancer cell typing. Different monoclonal antibodies have been shown to present therapeutic activities over a broad range of malignancies. One good example is the use of rituximab in the therapy of CD20 – positive hemopathies.
Despite recent advances in patient clinical management such as high dose chemotherapy, the disease still remains highly lethal within variable periods of time, ranging from a few weeks to more than ten years. Hence, the need and search for potential therapeutic targets on cell surface of cancer cells is a significant objective in cancer research. The detection of CD33 cells and quantifying the same by means of an intermediate product like AHL and determining the production of AHL by the expression of a reporter protein holds an enormous significance in this regard.
Detection of cell surface cancer markers is a key diagnostic step during cancer therapy as it allows the efficiency of a therapy to be determined. Current antibody-based flow cytometric detection methods are the gold standard. For our 2010 iGEM project, we hope to develop SensorBricks as a reliable and modular system for antigen recognition, signal amplification and quantification. We want to push the boundaries of detection in order to allow earlier diagnosis and thus improve therapeutic prognosis in cancer therapy. Initial steps of SensorBricks will focus on the detection of CD33 and other leukemic markers to increase diagnostic stringency.
There are three major components in SensorBricks: (i) monoclonal antibodies that bind to an antigen of interest, (ii) a LuxI-Protein A fusion construct which non-specifically binds antibodies and produces the autoinducer N-Acyl homoserine lactone (AHL), and (iii) a Escherichia coli based biosensor which in the presence of AHL strongly amplifies the production of green fluorescence protein (GFP). By coupling signal detection to a genetic circuit, we will be able to amplify the signal in a quantifiable manner, allowing the identification of cancer markers expressed in minute quantities. The presence of CD33+ cells in the blood of a patient will trigger the production of AHL, which in turn, activates the production of GFP in our E. coli biosensor. As such, we should be able to correlate the concentration of CD33 as a function of GFP fluorescence.
The modularity of SensorBricks is a key feature as it allows the same system and protocols to be used in combination with any antibody of choice to detect any antigen of interest.