GSHield: A Glutathione Patch for Treating Oral Mucositis
Oral mucositis (OM) is a common complication of cancer therapies characterized by the breakdown of epithelial cells in the oral cavity, which results in the release of inflammation-promoting reactive oxygen species (ROS) and subsequent DNA damage. This leads to the death of surrounding oral epithelial cells, which manifests as extremely painful sores in the mouth and leaves the mucosal tissue susceptible to infection and ulceration. From our discussion with numerous faculty, some of whom received cancer treatment themselves and have experienced oral mucositis, we were strongly motivated to address this problem and increase the quality of life of cancer patients.
Current therapeutics revolve around improving oral hygiene and treating the symptoms. However, these treatments neither reduce the accumulation of ROS nor prevent the development of OM into more severe stages. Therefore, our team aims to address the problem of ROS accumulation in hopes of reducing surrounding non-cancerous cell death, as well as provide a protective barrier between the oral cavity and potential irritants such as food/drink.
Our project’s goal is to produce a bacterial cellulose (BC) patch functionalized with glutathione-producing engineered yeast. Glutathione is an antioxidant that can decrease cellular ROS concentration in its reduced form (GSH). We designed a way to engineer S. cerevisiae to increase extracellular GSH production by knocking out genes that encode for glutathione degradation and overexpressing genes important for glutathione export and synthesis. Our system was also created to be able to sense and respond to environmental signals under an oxidative stress-responsive promoter. We will then co-culture this yeast with engineered BC-producing E. coli, generating a patch coated with our engineered yeast.
We are confident in this approach as we’ve found that exogenous administration of glutathione in rats reduces induced oral mucositic phenotype (Jain et al. 2010). In this paper, researchers made a hydrogen containing L-glutamine and tested it in an in vivo model. Their results show that adding glutamine helps the oral mucositis healing process by, according to the researchers, “enhanc[ing] DNA synthesis, cell proliferation, and glutathione production,” resulting in the most weight gain in rats treated in with the hydrogel. The researchers also find that the “administration of glutamine increased the mucosal tissue glutathione stores in 5-FU treated rats” indicating a strong correlation between increased glutathione and a faster oral mucositis healing process.
Our project will first entail engineering S. cerevisiae to increase extracellular glutathione production via knocking out a gene that encodes a glutathione degradation protein and overexpressing two genes important for glutathione export and synthesis, ADP1 and GSH1, as outlined in a paper by Kiriyama, Hara and Kondo (2012). However, our system will be able to sense and respond to environmental signals as we plan to overexpress these genes under an oxidative stress-responsive promoter. We will then co-culture this yeast with E. coli that we will engineer to produce BC in hopes of generating a BC patch coated with our engineered yeast as described in the paper, “Living materials with programmable functionalities grown from engineered microbial co-cultures” (Gilbert et al. 2021). We also plan to characterize glutathione production levels and the ROS scavenging activity of the released glutathione in further in vitro experiments both within and out the BC patch. To ensure the safety of our solution, we plan on exploring the effects of locally increasing glutathione levels in silico to demonstrate that our proposed solution does not contribute to further cancer development.
While existing solutions such as local rinses and painkillers aim to reduce pain, our solution includes a protective BC patch that would act as a physical barrier to prevent irritation in the mouth without promoting the tumor resistance associated with glutathione therapies. Ideally, our patch is a safer and more effective alternative to existing options to reduce pain, prevent mechanical irritation and infection, and ultimately encourage continuation of treatment.
Side effects do not receive a level of attention comparable to how much they affect patient lives. Yet, there are multiple severe consequences of oral mucositis including dosage reduction, delay, or termination of treatment due to the increased pain levels reported by patients. There is also evidence of an economic burden caused by OM. One estimate suggested an incremental cost of hospitalization exceeding $3500 per cycle in patients with mucositis (Elting 2003). Sociodemographic factors such as family income have also been shown to increase the risk of OM (Abdelaziz 2020). We hope that our project can provide a simple and, eventually, affordable way to prevent and reduce OM, preventing this additional burden on already disadvantaged groups.
Citations
Abdelaziz SH (2020). Oral Care And Its Association With Socio-Demographic Characteristics In Leukemic Patients Receiving Chemotherapy. The Malaysian Journal of Nursing (MJN), 12(1), 98-105.https://doi.org/10.31674/mjn.2020.v12i01.012
Elting LS, Cooksley C, Chambers M, Cantor SB, Manzullo E, and Rubenstein EB (2003). The burdens of cancer therapy. Cancer, 98: 1531-1539. https://doi.org/10.1002/cncr.11671
Jain P, Keservani RK, Dahima R (2010). In-vivo Characterization of Hydrogen for Treatment of Chemo-Therapy Induced Oral Mucositis. Pharmacology, 1: 1016-1025.