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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 longevity. Recent studies have increasingly implied the importance of Aldehyde dehydrogenase enzyme as a marker for cancer stem cells 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. We have set out 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. A number of isoforms of ALDH exist, and three of the most common occurring form in cancer will be isolated. The isoforms selected are ALDH1A1, ALDH1A3 and ALDH3A1. These isoforms show increased activity in recurrent forms of cancer. We have also identified ALDH2, which will be used as the control isoform, as this form is involved in ethanol metabolism and it will be easily induced 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 cancer cell lines. This will provide a powerful tool for researchers in the field of cancer Biology.

Assembly System

One challenge we had was finding parts for mammalian expression. We have opted to use the Plug and Play system of assembly created by DTU-Denmark for the 2011 iGEM competition. In addition, we have designed all our constructs to conform to biobrick standard parts. Due to the scarcity of available mammalian in the registry, we had to source parts from outside the parts registry. We were fortunate to obtain parts from DTU-Denmark which they had made in 2011, as they were not available in the Parts Registry. 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.