Princeton/Project Description

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The majority of contemporary cancer treatments utilize rather unspecific approaches in targeting cancer cells. Such methods do not, and indeed cannot, specifically target a particular cancer cell type. As a result of their imprecision, these treatments tend to inflict almost as much damage upon healthy cells as cancerous ones. Such harmful side-effects often make cancer treatments such as chemotherapy or radiation therapy not only undesirable, but also less comprehensive, as their prolonged use is ultimately unsustainable.
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The majority of contemporary cancer treatments utilize rather unspecific approaches in targeting cancer cells. Such methods do not, and indeed cannot, specifically target a particular cancer cell type. As a result of their imprecision, these treatments tend to inflict almost as much damage upon healthy cells as cancerous ones. Such harmful side-effects often make cancer treatments such as chemotherapy or radiation therapy not only undesirable, but also less comprehensive, as their prolonged use is ultimately unsustainable. Our proposed, generalizable, system will resolve this unfortunate situation by enabling the detection and destruction of cancer cells in a tissue-specific manner.
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The Princeton University iGEM 2007 team envisions a paradigm shift in the way we envisage cancer cell targeting. Our objective is to design and develop a new system that utilizes RNA interference (RNAi) mechanisms that would enable the detection and destruction of cancer cells in a tissue-specific manner. We will interface RNAi components together with promoter and repressor elements to form logic circuits, which will allow for the use of multiple criteria to further specify cancer targets. In doing so, we hope to minimize adverse effects to healthy cells, and thereby allow for more extensive and comprehensive cancer treatments.
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Our system is engineered in such a fashion as to prevent any deleterious effects on non-cancerous cells or on cells that exhibit characteristics similar to cancer cells. To this end, RNA interference (RNAi) is employed to provide an additional level of regulation and prevent the apoptotic genes from being silenced by any epigenetic events. The added dimension of tissue-localization ensures that the system does not target any non-cancerous cell, thus, providing the most direct and effective cancer therapy.
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While there are many different approaches for recognizing cancer cells, our proposed design will concentrate on those cancers whose presence are marked by specific upregulated factors. These factors can be transcription factors or other gene products, and are typically isolatable proteins found within the cell. We are optimistic about the applicability of such an approach as literature has identified several instances of upregulated factors that are uniquely associated with certain types of cancer. Our logic circuit design will allow us to use a unique combination of upregulated factors as criteria to be identified by the RNAi mechanism to alert our system to the presence of the targeted cancer. Upon identification of the set of upregulated factors, the cancer cell with our construct will activate a pathway that results in apoptosis. While apoptosis should only ensue if a specific set of cancer markers is present, as an additional safety mechanism, we will also design and use a lentivirus that contains a mutant integrase, which will prevent the integration of our construct into the genomes of the affected cells. Instead, our construct will be inserted into the cell as a non-integrated plasmid.  This will prevent any disruptive effects that could be attributed to pseudorandom integration by the lentiviral delivery mechanism and will also ensure that the system will not be inherited by future generations of the affected cells, thus preventing unintended proliferation of our construct.
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The Princeton University iGEM 2007 team selected breast cancer as their initial target. In MCF-7 breast cancer cells, GATA3, a non-neuronal ectoderm cell fate regulator and a transcription factor present in and important for the maintenance of breast tissue cells, is upregulated to levels approximately thirty-two times those found in healthy cells. When present in large quantities, as in the case of cancerous cells, GATA3 will titrate away the small interfering RNA (siRNA) and allow transcription and translation of the pro-apoptotic factors Bax or Bak. When present in small quantities, Bax and Bak are repressed by binding of the siRNA to the engineered stretch of sequences located either 5' or 3' to the Bax or Bak gene. A helper plasmid containing a mutated pol gene will enable the transient transfection of the entire system into the cancer cells, as opposed to the integration that would occur with the wild type pol gene. This transient effect will ensure that the apoptotic genes are not propagated by further cell division, thus preventing unintended proliferation of our construct.
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Latest revision as of 15:55, 25 October 2007

Project description

A Lentivirus-Delivered, RNAi-Enhanced Logic Circuit for Cancer-Specific Detection and Destruction

Princeton University iGEM 2007 Team

Princeton University, Princeton, NJ 08544, USA

Ron Weiss rweiss@princeton.edu

The majority of contemporary cancer treatments utilize rather unspecific approaches in targeting cancer cells. Such methods do not, and indeed cannot, specifically target a particular cancer cell type. As a result of their imprecision, these treatments tend to inflict almost as much damage upon healthy cells as cancerous ones. Such harmful side-effects often make cancer treatments such as chemotherapy or radiation therapy not only undesirable, but also less comprehensive, as their prolonged use is ultimately unsustainable. Our proposed, generalizable, system will resolve this unfortunate situation by enabling the detection and destruction of cancer cells in a tissue-specific manner.
Our system is engineered in such a fashion as to prevent any deleterious effects on non-cancerous cells or on cells that exhibit characteristics similar to cancer cells. To this end, RNA interference (RNAi) is employed to provide an additional level of regulation and prevent the apoptotic genes from being silenced by any epigenetic events. The added dimension of tissue-localization ensures that the system does not target any non-cancerous cell, thus, providing the most direct and effective cancer therapy.
The Princeton University iGEM 2007 team selected breast cancer as their initial target. In MCF-7 breast cancer cells, GATA3, a non-neuronal ectoderm cell fate regulator and a transcription factor present in and important for the maintenance of breast tissue cells, is upregulated to levels approximately thirty-two times those found in healthy cells. When present in large quantities, as in the case of cancerous cells, GATA3 will titrate away the small interfering RNA (siRNA) and allow transcription and translation of the pro-apoptotic factors Bax or Bak. When present in small quantities, Bax and Bak are repressed by binding of the siRNA to the engineered stretch of sequences located either 5' or 3' to the Bax or Bak gene. A helper plasmid containing a mutated pol gene will enable the transient transfection of the entire system into the cancer cells, as opposed to the integration that would occur with the wild type pol gene. This transient effect will ensure that the apoptotic genes are not propagated by further cell division, thus preventing unintended proliferation of our construct.
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