Team:CSU CHINA/Description

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DESCRIPTION

Overall Introduction

Based on the high heterogeneity and invasiveness of TNBC, our team has characterized a gene circuit with three modules. Controlled by TNBC-specific promoter 1, module 1 includes a miRNA binding site(BS) and a transcription factor which drives Module3 --- expression of a fusion protein composed of HIF1-αoDDD and yeast cytosine deaminase (yCD) working under hypoxia conditions. Module 2 includes several sponge-like domains effectively down-regulating specific miRNA when promoter 2 is driven. Supposing the miRNA is highly expressed in the normal cells and low in most cancer cells, this circuit could trigger highly selective cytotoxicity of cancer cells. Once optimized, our design could be applied to current treatments, allowing for a more powerful therapeutic effect with a comparatively low risk.

Status 1(in TNBC cells)

High efficiency of P1 + low miRNA expression + hypoxia=kill

Status 2(in TNBC cells)

High efficiency of P1&P2 + relatively high expression of miRNA + hypoxia=kill

Status 3(in normal cells)

Little expression of GAD nor sponge=not kill

Status 4(in normal cells)

Relative high efficiency of P1 + low efficiency of P2 +high level of miRNA + normoxia=not kill

INSPIRATION

Cancer treatment has always been the hottest issue in society, and a medical documentary called "The World" has recently attracted public attention. Through it, we see disease, death, and people who never give up hope. One episode tells the story of a triple-negative breast cancer patient, whose story is moving but struggle. Chemotherapy once a week and review once a forty-two day is the routine of chemotherapy for a cancer patient. Chemotherapeutic drugs cause vomiting, hair loss, skin darkening, nails, skin decay, and normal cells in the body to collapse which aims to kill the cancer cells that are latent in them.And even if we treat in this way ,it is still ineffective for some cancer cells.

In this documentary, we feel the happiness and sadness when suffering and waiting of a family of triple negative breast cancer patients. Her anti-cancer story has attracted a lot of people including us. After consulting the teachers, we determined that the general direction of the subject was related to the treatment of triple negative breast cancer.

It hurts to see that thousands of women as well as men each year tormented by breast cancer both physically and mentally. Despite success in several clinical trials, triple negative breast cancer（TNBC ）still remains a major challenge in fundamental research. So our goal is to design a genetic gene circuit which is able to trigger cancer specific cytotoxicity in TNBC.

For our project, we consulted Professor Guang Wenyan of the Third Xiangya Hospital. Professor Wen said that in our experiments, it is important to find transcription factors or promoters specifically expressed in the breast so that the system can be specifically expressed in breast cells. If it's not targeted at the breast, it doesn't make sense.Indeed, synthetic biology is not a subject created from scratch, it’s the subtle combination of nature organism and laboratory trials . So ,we utilize the nature marker of TNBC, such as miRNA and cancer specific promoter to guarantee a cancer specific circuit.

As for the safety of gene therapy, Professor Wen said that the main problem lies in the carrier, followed by specificity .The carrier like viral bacterial vectors may be prone to problems. So instead of using viral bacterial vectors, we use transferrin combined with liposomes to directly target cancer cells. In this way, targeting can be very good with transduction efficiency being relatively high thus to reduce the risk.

On the issue of specificity, we introduce Boolean logic——AND gate to initiate our three modules, which generates combinatorial outputs only when all three promoters are mutually active. With mathematical modeling and systematical calculation, this genetic circuit with efficiency and specificity could be promising in future treatment.