Abstract
Cancer remains one of the deadliest diseases in the world despite the advances in current diagnosis and treatment1. Current challenges in onco-therapy include targeting, specificity, and side effects1. With that in mind, we are focused on applying synthetic biology to develop a live bacteria-based antitumor therapeutic vaccine delivered in situ to solid carcinomas by a thermosensitive hydrogel. We will use a non-pathogenic strain of E.coli BL21 (DE3) to produce a native to the bacteria pore-forming toxin, Colicin E1, expressed in response to a high lactate presence in the tumor microenvironment. To prevent a harsh immune reaction, we encapsulate bacteria into a chitosan-based thermosensitive and biodegradable hydrogel, solidifying in situ upon injection. As a result of the project, a smart, localized, and controlled therapeutic vaccine will be developed to be injected once and ensure sustainable drug release for a determined period.
What is the problem?
Modern conventional methods of cancer treatment, such as Radiotherapy, where the patient is exposed to high doses of X-rays, and Chemotherapy, in which the whole body is systemically exposed to cell-killing medications, do not exhibit high specificity for cancer cells. Therefore, these methods are not safe enough for normal tissues and organs. Of course, when a person's life is threatened by an uncontrolled disease that spreads at an alarming rate, a patient will choose the most effective methods regardless of their consequences. It has been proven many times that radiotherapy can lead to severe and undesirable side effects such as diarrhea, vomiting, hair loss, headaches, weakness, fatigue, etc2. Chemotherapy, in turn, is predominantly done by injecting the therapeutic component into the blood vessels, through which it spreads over the body, which can cause massive damage not only to cancerous tissues but also to normal cells. Aside from that, chemotherapy exposes the body to infections because it damages the rapidly dividing stem cells that produce immune components and eventually can lead to neutropenia. Also, chemotherapy has all the other side effects observed after radiation therapy3,4.
So, when it comes down to the core of the issue, it is a problem of specifically affecting the tumor, causing little or no damage to healthy cells, and minimizing possible side effects. Also, a secondary problem is to make sure that a single dose of medicine has a long-term therapeutic effect since frequent drug injections or irradiations can cause mental and physical complications in patients and negatively affect their lives. Our project aims to propose a solution to all these issues simultaneously.
Novel drug delivery approach
The use of hydrogels to deliver bacteria as drug-releasing agents is a novel approach that offers many advantages5,6, including localized administration to solid tumors with targeted transfer of drugs to cancer cells only, sustained release of anti-cancer toxins produced by bacteria, controlled payload of drug concentration, and biocompatible, biodegradable, and FDA-approved materials that maintain the biochemical activity of the embedded bacteria7. Our objective is to create a living bacteria-mediated drug-release machinery against carcinoma delivered by the in situ forming hydrogel. The outcome of the project is a novel, affordable, efficient, safe, and specific therapeutic treatment against solid tumors.
Proposed solution (implementation)
We developed the Cellcare therapeutics - a system, which is composed of genetically modified anticancer drug producing bacteria embedded into the in situ forming temperature-sensitive hydrogel. The kit will consist primarily of glycerol stocks of genetically modified E. coli cells and reagents required for hydrogel synthesis. The system can be easily synthesized and assembled in any laboratory since its main player is bacteria, which are relatively easy to maintain, and the hydrogel consists of relatively affordable and widely available reagents. The synthesis procedure is very straightforward and simplistic. The Cellcare system will allow direct intratumoral injection of the in situ forming hydrogel that will solidify in response to increase in the temperature. The porous nature of the hydrogel will allow the Colicin E1 toxin, which is produced by genetically modified bacteria, to escape through the pores and cause cancer cell death. Hydrogel does not allow bacterial cell leakage and unwanted spread in the body. More importantly, the hydrogel is degradable, and the whole system has immunomodulatory properties, enhancing the immune response at the site of injection. This is very important because traditional therapies, on the contrary, cause suppression of the immune system and are susceptible to various diseases.
Find the results of our project on the Results page
How does it work?
Specially trained personnel prepare a hydrogel, encapsulate genetically modified bacteria in the required volumes, and inject the system into the site of the tumor. Then, lactate in the tumor microenvironment freely diffuses into the hydrogel and enters the bacteria, where it binds to AlPaGA, which in turn allows the transcription and translation of Colicin E1 and Immunity proteins. Colicin E1 is exported from the cell, diffuses out of the gel, and reaches the cancer tumor, where it destroys the cancer cells. After some time, the hydrogel disintegrates, and the genetically modified bacteria are destroyed by the immune system, providing a safe and long-lasting therapeutic effect.
Why carcinoma tumors?
The project's main goal required us to select a type of cancer that was very common, highly lethal, and readily accessible for local administration of the hydrogel via injection. In light of this, we opted to concentrate on solid tumors that are easy to detect and pinpoint. Consequently, we chose to study carcinomas, which include lungs, breasts, prostate, colon, skin, and many other major types of cancer8. Unlike lymphomas or central nervous system tumors, carcinomas are easier to treat locally, and our hydrogel-embedded bacteria will be directly injected into the tumor cells.
1.Chakraborty, S., & Rahman, T. (2012). The difficulties in cancer treatment. Ecancermedicalscience, 6, ed16. https://doi.org/10.3332/ecancer.2012.ed16
2.Radiation therapy side effects. (2022, January 11). National Cancer Institute. https://www.cancer.gov/about-cancer/treatment/types/radiation-therapy/side-effects
3.Pearce, A., Haas, M., Viney, R., Pearson, S. A., Haywood, P., Brown, C., & Ward, R. (2017). Incidence and severity of self-reported chemotherapy side effects in routine care: A prospective cohort study. PloS one, 12(10), e0184360. https://doi.org/10.1371/journal.pone.0184360
4.Why People with Cancer Are More Likely to Get Infections. (n.d.). American Cancer Society. https://www.cancer.org/cancer/managing-cancer/side-effects/low-blood-counts/infections/why-people-with-cancer-are-at-risk.html
5.Shin, G. R., Kim, H. E., Kim, J. H., Choi, S., & Kim, M. S. (2021). Advances in Injectable In Situ-Forming Hydrogels for Intratumoral Treatment. Pharmaceutics, 13(11), 1953. MDPI AG. http://dx.doi.org/10.3390/pharmaceutics13111953
6.Yu, S., Sun, H., Li, Y., Wei, S., Xu, J., & Liu, J. (2022). Hydrogels as promising platforms for engineered living bacteria-mediated therapeutic systems. Materials Today Bio, 16, 100435. https://doi.org/10.1016/j.mtbio.2022.100435
7.Ahsan, A., Farooq, M., & Parveen, A. (2020). Thermosensitive Chitosan-Based Injectable Hydrogel as an Efficient Anticancer Drug Carrier. ACS Omega, 5(32), 20450–20460. https://doi.org/10.1021/acsomega.0c02548
8.Zhang, P. W., Chen, L., Huang, T., Zhang, N., Kong, X. Y., & Cai, Y. D. (2015). Classifying ten types of major cancers based on reverse phase protein array profiles. PloS one, 10(3), e0123147. https://doi.org/10.1371/journal.pone.0123147>
