Browsing by Author "Conradie, Daleen"

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    Dynamic interactions between skeletal muscle and breast cancer cells following chemotherapeutic treatment
    (Stellenbosch : Stellenbosch University, 2019-04) Conradie, Daleen; Engelbrecht, Anna-Mart; Isaacs, Ashwin; Davis, Tanja; Stellenbosch University. Faculty of Science. Dept. of Physiological Sciences.
    ENGLISH ABSTRACT: Background: Breast cancer is the most common cancer found among women of South Africa with the prominent effective form of treatment being chemotherapy. Many cancer patients receiving chemotherapeutic treatment experience skeletal muscle wasting, however, the contribution of muscle wasting to the metastatic properties of breast cancer and response to current treatment strategies has not yet been fully investigated. The aims of this study were to investigate the reciprocal interactions between mouse breast cancer cells (E0771) and mouse myotubes (C2C12) as well as the effects of doxorubicin (DXR) on these interactions. Methods: Conditioned media was collected from two separate cycles. The initial cycle of conditioned media was collected from E0771 breast cancer cells after treatment with/without 1.6 μM of DXR. Myotubes were then treated with/without DXR as well as conditioned media collected during the initial cycle from the E0771 cells. A new series of E0771 cells were then treated with/without DXR as well as with the second cycle of conditioned media collected from the myotubes. Mitochondrial integrity of myotubes was investigated using MitoSOX™ stain analysis while myotube cell viability and integrity was assessed using a Cell Tracker™ stain analysis. Cell viability of E0771 cells was assessed with an MTT assay and the migratory properties (wound closure) using a migration scratch assay. Western blot analyses were used to determined alterations in proliferation, apoptotic, and epithelial-mesenchymal transition (EMT) signaling pathways. Results: Treatment of myotubes with 1.6 μM of DXR significantly induced mitochondrial ROS production (5.580 ± 0.4, p<0.001) when compared to Control but myotube integrity was maintained. Treatment of E0771 cells with 1.6 μM of DXR compared to Control significantly decreased cell viability (60.354% ± 1.237, p<0.001), significantly increased the phosphor/total ERK expression ratio (3.946 ± 0.520, p<0.001), and significantly decreased the cleaved/total PARP expression ratio (0.651 ± 0.027, p<0.001). Additionally, a significant increase in the percentage of wound closure was also observed in the DXR group (16.049% ± 1.11, p<0.01) compared to Control after 24-hours. E0771 cells treated with myotube conditioned media after treatment of DXR (C.DXR), induced a significant decrease in expression of the cleaved/total PARP ratio (0.662 ± 0.097, p<0.01) as well as a significant difference in percentage of wound closure (17.19 ± 0.758, p<0.001) compared to C.Control. Following treatment of the E0771 cells with myotube conditioned media, harvested after the treatment of conditioned media from DXR treated E0771 cells (C.C.DXR), a significant increase in cell viability (121.743% ± 3.442, p<0.05) when compared to C.C.Control. Additionally, comparison of C.C.DXR to C.C.Control observed a significant decrease in expression of total Akt (65.554% ± 17.55, p<0.05), MCM2 (55.167% ± 14.64, p<0.05), and the cleaved/total PARP ratio (0.456 ± 0.111, p<0.001) was observed. Conclusion: Investigation of the dynamic interactions between myotubes and breast cancer cells revealed novel evidence of the influence of the myotube environments on cancer progression. Our study also revealed novel evidence that this myotube environment significantly affected the response of breast cancer cells to the chemotherapeutic treatment of DXR. These findings identified new mechanisms that may promote breast cancer metastasis, which can be utilized to improve chemotherapy in cancer patients.
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    Insulin as an immunomodulatory hormone
    (Elsevier, 2019) Van Niekerk, Gustav; Christowitz, Claudia; Conradie, Daleen; Engelbrecht, Anna-Mart
    Insulin plays an indispensable role in the management of hyperglycaemia that arises in a variety of settings, including Type I and II diabetes, gestational diabetes, as well as is in hyperglycaemia following a severe inflammatory insult. However, insulin receptors are also expressed on a range of cells that are not canonically implicated in glucose homeostasis. This includes immune cells, where the anti-inflammatory effects of insulin have been repeatedly reported. However, recent findings have also implicated a more involved role for insulin in shaping the immune response during an infection. This includes the ability of insulin to modulate immune cell differentiation and polarisation as well as the modulation of effector functions such as biocidal ROS production. Finally, inflammatory mediators can through both direct and indirect mechanisms also regulate serum insulin levels, suggesting that insulin may be co-opted by the immune system during an infection to direct immunological operations. Collectively, these observations implicate insulin as a bona fide immune-modulating hormone and suggest that a better understanding of insulin’s immunological function may aid in optimising insulin therapy in a range of clinical settings.