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The Cancer Stem Cell Theory

Many tumours contain a sub-population of self-renewing and expanding stem cells known as cancer stem cells whose symmetric division result in tumour growth. These cancer stem cells can be identified using molecular determinants or markers which have properties such as self-renewal, clonogenicity, multipotentiality, and adherence to the niche, and longevity. Recent studies have increasingly implied the importance of Aldehyde dehydrogenase enzyme as a marker owing to their ability to detoxify potential cytotoxins, thus making them resistant to chemotherapy.

Our Project

Our iGEM project taps into the cancer stem cell theory to synthesise a genetic construct that can identify, isolate and destroy cancer stem cells. Three different genetic constructs which serve different purposes are to be synthesised, using the promoters for different isoforms of the aldehyde dehydrogenase. The isoforms selected are ALDH1A1, ALDH1A3 and ALDH3A1 for being the main three types that show increased activity in recurrent forms of cancer. We also use ALDH2 as control construct, as this form is involved in ethanol metabolism and it will be easy to induce by the addition of ethanol.

The second part of our project was to create constructs to selectively isolate cancer stem cells in a range of tumors and cancer cell lines. This will provide a powerful tool for researchers in the field of cancer Biology. To do this, we chose to use the Plug and Play system of assembly created by DTU-Denmark for the 2011 iGEM competition and then make our biobricks RFC-21 compatible according to the guidelines for iGEM submission. To achieve this plug and play system, we contacted DTU and had them send us some of the parts they had made last year, as they were not available in the Parts Registry.

Mammalian Expression

Because cancer is a human disease, we decided to test our constructs in mammalian cells. One challenge we had was finding parts for mammalian expression. For this reason, we contacted the Serrano labs and had them send us their entire eukaryotic promoter database. The aim was to use and modify these parts to function in a way that will identify putative cancer stem cells.