Hi, I am dCasentry,

a T7—dCas9 multi-output DNA sensor designed to detect ctDNA!

Cancer is a leading cause of death worldwide, accounting for 8.8 million deaths in 2015, and the most common causes of cancer death is lung cancer (1.69 million deaths). Nowadays, multiple lung cancer detection methods are developed, and I can be an assistant in liquid biopsy whose detection minimizes trauma and pain. The tumor marker I detect is circulating tumor DNA (ctDNA), tumor-derived fragmented DNA in the bloodstream that is not associated with cells. It is released by the dying cells during the biological process of apotheosis and necrosis, or active release from viable tumor cells.

I am an improved version of the paired dCas9 system designed by 2015 Peking university iGEM, composing of sgRNA, a pair of dCas9 protein and a split T7 RNA polymerase switch connected to each dCas9 protein via a linker. The sgRNA is designed to detect target genes and I will complete my task according to this order: First, the sgRNA will instruct each sgRNA-dCas9 complex to certain locus. Next, unlike Peking University, a T7 RNA polymerase rather than a luciferase is split apart and connected to dCas9 protein via a linker. I call them NT7-dCas9 and CT7-dCas9. Once two sgRNA are attached to the target sequence, two split parts will reunion and reassemble to form a complete RNA polymerase and start transcription consistently, which means even though the initial ctDNA concentration is low, the signal will continue to be magnified until it can be observed. Also, there is no limit on the content I can transcribed, that is, I am able to give out many kinds of signals, including GFP, RFP or LacZ.

In this project my main goal is to detect the fusion gene EML4-ALK. Some of the cancer, including non small cell lung cancer (NSCLC), is caused by gene fusion. When two respective original genes fuse together, it produces the expression product of fusion gene, which induced the canceration of cells. EML4-ALK exists only in NSCLC patients’ blood which prevents false positive result during detection and there is a specific targeted drug for this mutation which means patients can have precise treatment as soon as possible when the detection result is positive. My work is meaningful.

Finally, as a well-rounded and efficient lung cancer fusion gene detection sentry, I am proud to point out this important reason why you can trust me —I can carry out a simpler liquid biopsy process. Although the liquid biopsy avoid copliacation, common liquid biopsy required laboratory apparatus such as PCR instrument during the detection of ctDNA. In my work, my DNA device and proteins that needed for detection will mixed in a E.coli cell-free system and freeze-dried on a paper screening chip. You will be seeing me in a convenient kit that contains all tools you need for detection, including hemostix, a hand power centrifuge, NASBA reaction system and the paper screening chip.

Please, click here and know more about me as well as the product!