Dynamic interactions between skeletal muscle and breast cancer cells following chemotherapeutic treatment

[摘要] ENGLISH ABSTRACT: Background: Breast cancer is the most common cancer found among women of SouthAfrica with the prominent effective form of treatment being chemotherapy. Many cancerpatients receiving chemotherapeutic treatment experience skeletal muscle wasting,however, the contribution of muscle wasting to the metastatic properties of breast cancerand response to current treatment strategies has not yet been fully investigated. The aims ofthis 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 theseinteractions.Methods: Conditioned media was collected from two separate cycles. The initial cycle ofconditioned media was collected from E0771 breast cancer cells after treatment with/without1.6 μM of DXR. Myotubes were then treated with/without DXR as well as conditioned mediacollected during the initial cycle from the E0771 cells. A new series of E0771 cells were thentreated with/without DXR as well as with the second cycle of conditioned media collectedfrom 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 themigratory properties (wound closure) using a migration scratch assay. Western blot analyseswere used to determined alterations in proliferation, apoptotic, and epithelial-mesenchymaltransition (EMT) signaling pathways.Results: Treatment of myotubes with 1.6 μM of DXR significantly induced mitochondrialROS production (5.580 ± 0.4, p<0.001) when compared to Control but myotube integrity wasmaintained. Treatment of E0771 cells with 1.6 μM of DXR compared to Control significantlydecreased cell viability (60.354% ± 1.237, p<0.001), significantly increased thephosphor/total ERK expression ratio (3.946 ± 0.520, p<0.001), and significantly decreasedthe cleaved/total PARP expression ratio (0.651 ± 0.027, p<0.001). Additionally, a significantincrease 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 myotubeconditioned media after treatment of DXR (C.DXR), induced a significant decrease inexpression of the cleaved/total PARP ratio (0.662 ± 0.097, p<0.01) as well as a significantdifference 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 significantincrease 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 inexpression of total Akt (65.554% ± 17.55, p<0.05), MCM2 (55.167% ± 14.64, p<0.05), andthe cleaved/total PARP ratio (0.456 ± 0.111, p<0.001) was observed.Conclusion: Investigation of the dynamic interactions between myotubes and breast cancercells revealed novel evidence of the influence of the myotube environments on cancerprogression. Our study also revealed novel evidence that this myotube environmentsignificantly affected the response of breast cancer cells to the chemotherapeutic treatmentof DXR. These findings identified new mechanisms that may promote breast cancermetastasis, which can be utilized to improve chemotherapy in cancer patients.

[发布机构] Stellenbosch University