Our designed BioBricks containing the gene for the mature region of mouse Bone Morphogenetic Protein 2 (BMP2) all possess a level of risk. As a mammalian biochemical agent, it is known to elicit a wide variety of biological effect on human tissue organs, of which the most well known are bone and cardiac cell differentiation induction. However, as a defining member of the Transforming Growth Factor Beta (TGF-β) pathway, it also plays important roles in cell proliferation. Thus, induction of excess (or otherwise external) BMP2 may lead to undesirable tissue behavior in mammalian systems.

Documented adverse effects of recombinant human BMP2 used in spinal fusion therapy include cyst-like bony formations and soft swelling with hematomas. Further research using mice with spine defects as test subjects indicates that occurrence and severity of said adverse effects increases with BMP2 dosage. Though we have selected BMP2 for its documented properties of retarding the growth of and induction of cell death in colon carcinoma cells, BMP2 receptor transcription has been found up-regulated in other cancer cell types, including pancreatic cancer. Thus, confined delivery of the chemokine becomes critical.

See relevant documents by following links below:
High Doses of Bone Morphogenetic Protein 2 Induce Structurally Abnormal Bone and Inflammation In Vivo
Bone morphogenetic protein signaling and growth suppression in colon cancer

We highly recommend that future teams intending to use this gene simultaneously incorporate methods to control production of BMP2 to minimize its release into the environment or contact with researchers and the public. Our strategy described in module 3 – ‘control and regulation system’ may be taken as an initial attempt to achieve this.

BioBricks for expression of the lytC protein cell wall binding domain with the RPMrel phage display peptide attached at its C-terminus results in RPMrel peptides anchored to the chassis cell wall. It is known that phages displaying this peptide bind preferentially to the highly tumorigenic HT29 colorectal cell line by at least 10-fold higher than the less tumorigenic HCT116 colorectal cell line. As expression of this peptide in bacterial cells is novel, steps should be taken to minimize the chance of its horizontal transfer to pathogenic bacterial species, which could result in increased infection activity of that species. Integration of this gene into the bacterial genome, an approach taken by our team, would be one way to work towards reducing horizontal gene transfer.

Please refer to the document below:
Isolation of a Colon Tumor Specific Binding Peptide Using Phage Display Selection

Elements of our toxin-antitoxin system for control over cell lysis comprise the ydcDE operon of Bacillus subtilis. The ydcE gene encodes an endoribonuclease targeting regular regions of cellular mRNA. The gene ydcD has been shown to inhibit the function of said endonuclease in vivo. Our system employs those same gene products recombined with different promoters: pVeg promoter for ydcD, pXyl promoter for ydcE. An investigation to determine whether expression of the E. coli ydcE homolog (mazF) in macaque monkeys is safe yielded results indicating an absence of tissue damage and antigen-specific antibody production. We therefore consider the ydcE product to be non-toxic to humans.

Again refer to the document by clicking here.

Construction and characterization of our project’s assorted constructs involves working with two non-pathogenic bacterial strains: Escherichia coli DH10B and Bacillus subtilis 168. Both strains are commonly used in research, education and industry sectors. Characterization also required the use of human colon carcinoma HT29 cells. Bacterial strains were manipulated in accordance with Biosafety Level 1. The HT29 cells were manipulated in a designated tissue culture room within laminar flow hoods by team members trained for tissue work. Biosafety Level 2 was observed. In the lab, gloves and lab coats were worn.

Notably toxic and/or mutagenic substances used in the lab include phenol, chloroform and ethidium bromide. They were used only by members of the team who had received safety training to recognize the associated hazards and handle them appropriately.

Working on B. subtilis brings with it the risk of endospore inhalation. B. subtilis regularly forms spores in the environment when under stress. However the low toxicity of the organism to humans suggests that debilitating infection is extremely rare.

Hypersensitive responses to the subtilisin enzyme excreted by B. subtilis found in detergent form are more likely. Standard precautions for handling microorganisms such as proper wearing of gloves to prevent direct contact will help to alleviate this risk.

Of the few documented cases of B. subtilis infection, the vast majority involved severely immunocompromised patients. Should one of our researchers enter such a state, they will not be allowed into the lab and will be expected to rest and seek treatment.

The ultimate aim of our team’s biological system is to perform a task acting as an anti-cancer agent within the human digestive tract. Direct interaction with live human cells is a requirement of its function thus demanding particular considerations for safety. Similar precautions to protect cancer patients for whom the treatment is intended will also help in protecting the public in the off-chance our system enters the environment beyond the lab.

Firstly it must be made clear that no patient exhibiting immunodeficiency or under immunosuppression should be recommended for this treatment or any subsequent approved derivative of this treatment. There is the likelihood these patients will suffer B. subtilis infection.

B. subtilis is a known normal gut commensal and is considered a minimal risk bacterial species. It produces no particles considered toxic to humans. Enzymes produced by B. subtilis, including carbohydrases and proteases contributing to its function as a part of the gut microbiome, are classified ‘Generally Recognized As Safe’ (GRAS) by the FDA. The species has also been proven to function as a probiotic when consumed in certain food stuffs, most notably fermented soy bean. No recombined component of our biological system is known to confer negative effects on gut microbiome function.

Two regulatory functions were put in place to control BMP-2 production by the system and minimize its potential negative effects. Firstly, the BMP-2 construct makes use of a xylose-inducible promoter. This induction system greatly reduces the chance of BMP-2 production in any unintended circumstance. Secondly, a cap is placed on maximum BMP-2 production per cell by incorporating a toxin-antitoxin cassette with toxin transcription in direct correlation with BMP-2 transcription. This cap is intended to prevent the onset of adverse effects caused by excessive BMP-2 signalling.  More information on these regulatory functions can be found at the module 3.