Potential for modulation of cancer-associated oxidative stress : an in vitro investigation

Tunstall, Rebecca (2019-04)

Thesis (MSc)--Stellenbosch University, 2019.

Thesis

ENGLISH ABSTRACT: While cancer is a chronic, complex disease associated with a multitude of steps in its initiation and progression, all cancers generally have similar underlying maladaptive physiological mechanisms which may be addressed in order to prevent or treat this disease. Interest in the context of this thesis was in two of these maladaptive mechanisms, namely inflammation and oxidative stress. Both unresolved or severe inflammation and oxidative stress have been associated with cancer aetiology, and therefore administration of an anti-inflammatory or antioxidant could potentially prevent the initiation and progression of cancer. Current conventional cancer therapies are associated with a wide range of adverse side effects, leading to much interest in plant-based alternatives. For the purpose of this thesis, Δ-7 mesembrenone, a potent antioxidant isolated from Sceletium tortuosum and Cannabidiol, an antioxidant and anti-inflammatory extracted from Cannabis sativa, were studied in the context of breast cancer treatment. The potential anti-cancer activity of Δ-7 mesembrenone and Cannabidiol were investigated in three breast cell models in vitro. MCF12A, MCF7 and MDA-MB-231 cells were treated with varying doses of Δ-7 mesembrenone and Cannabidiol in isolation or in combination for a period of 24 hours, and the effects on cell viability and mitochondrial reductive capacity were assessed. Following this, the ROS production and the GSH/GSSG ratio were determined. Δ-7 mesembrenone in isolation resulted in cytotoxicity and increased ROS production across all cell models. Cannabidiol exposure in estrogen receptor positive breast cancer resulted in reductions in cell viability and mitochondrial reductive capacity, corresponding to an increased ROS production in these cells. No toxic effects of CBD were evident in the estrogen receptor negative breast cancer or normal breast cells at lower doses. Finally, combination treatments resulted in adverse effects across all cell models and at combined high doses, the negative effects were cumulative. We conclude that Δ-7 mesembrenone has no benefit in the context of breast cancer, as it exhibited significant levels of cytotoxicity in normal healthy breast cells at all concentrations reducing cancer cell survival, which could not be countered by Cannabidiol co-treatment. Cannabidiol showed more promise as an anti-cancer drug due to its high levels of cytotoxicity and the increased ROS production it induced in the estrogen receptor positive breast cancer cell line. Both the normal breast cells and the estrogen receptor negative cells exhibited little side effects than can be ascribed to Cannabidiol, illustrating the importance of this treatment in certain types of breast cancer only. Further research is warranted to better elucidate the cellular mechanisms involved and potential for treatment with this extract.

AFRIKAANSE OPSOMMING: Hoewel kanker ‘n chroniese en komplekse toestand is wat gepaardgaan met verskeie stappe in terme van oorsprong en progressive, het all kankers ooreenstemmende onderliggende wanaanpassings van fisiologiese sisteme wat geaddresseer kan word om die siekte te behandel of te voorkom. In die konteks van hierdie tesis is twee van hierdie wanaangepaste meganismes, inflammasie en oksidatiewe stres, van spesifieke belang. Beide hierdie meganismes word geassosieer met kanker etiologie. Dus kan toediening van anti-inflammatoriese or anti-oksidant middels potensieel teen kanker beskerm. Huidige konvensionele kankerterapie word gekenmerk deur ‘n verskeidenheid newe-effekte, wat gelei het na belangstelling in plantverwante alternatiewe. Vir die doel van hierdie tesis, is Δ-7 mesembrenoon, ‘n sterk anti-oksidant geïsoleer uit Sceletium tortuosum, en kannabidiool, ‘n anti-oksidant en anti-inflammatoriese middel uit Cannabis sativa, in die konteks van borskanker bestudeer. Die moontlike teenkanker aktiwiteit van Δ-7 mesembrenoon en kannabidiool is in vitro in drie borskanker selmodelle ondersoek. MCF12A, MCF7 en MDA-MB-231 selle is met ‘n verskeidenheid dosisse van Δ-7 mesembrenoon en kannabidiool, in isolasie of in kombinasie, behandel vir 24 uur, gevolg deur ‘n assessering van die effekte op sel lewensvatbaarheid en mitokondriale reduktiewe kapasiteit . Hierna is reaktiewe suurstof spesie (RSS) produksie en die GSH/GSSG verhouding bepaal. Δ-7 mesembrenoon op sy eie was sitotoksies en het verhoogde RSS produksie in alle seltipes tot gevolg gehad. Kannabidiool blootstelling in estrogeen reseptor positiewe borskankerselle het verlaagde seloorlewing en mitokondriale reduktiewe kapasiteit veroorsaak, wat ooreenstem met die verhoogde RSS produksie in hierdie sellyn. Geen toksiese effekte van kannabidiool was sigbaar in estrogeen negatiewe selle by laer dosisse nie. Laastens het die kombinasie behandeling newe-effekte gehad in alle modelle – hierdie effekte was kumulatief by hoër dosisse. Ons gevolgtrekking is dat Δ-7 mesembrenoon geen voordeel in die konteks van borskanker inhou nie, aangesien dit toksies was vir normale selle by alle konsentrasies wat kankersel oorlewing beperk het. Hierdie negatiewe effek kon nie voorkom word deur byvoeging van kannabidiool nie. Kannabidiool het meer belofte ingehou as teenkankermiddel deur verhoogde sitotoksisiteit en RSS produksie wat dit in estrogeen reseptor positiewe selle tot gevolg gehad het. Beide normale en estrogeen negatiewe selle het min newe-effekte op kannabidiool gewys, wat die potensiaal van kannabidiool behandeling in sekere kankertipes uitwys. Verdere navorsing sal help om die meganismes betrokke op sellulêre vlak, verder te belig.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/106063
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