Simvastatin treatment varies the radiation response of human breast cells in 2D or 3D culture

Abstract

SummaryBackground Statins inhibit the cholesterol biosynthesis and are used as cholesterol-lowering agents in fat-metabolism disorders. Furthermore, several studies state that statins have supportive functions in breast cancer treatment. Therefore, simvastatin (SVA) as a potential radiosensitizer should be investigated on the basis of human breast cells. Methods First, an optimal concentration of SVA for normal (MCF10A) and cancer (MCF-7) cells was identified via growth and cytotoxicity assays that, according to the definition of a radiosensitizer in the narrower sense, enhances the effect of radiation therapy but has no cytotoxic effect. Next, in combination with radiation SVA’s influence on DNA repair capacity and clonogenic survival in 2D and 3D was determined. Furthermore cell cycle distribution, expression of survivin and connective tissue growth factor (CTGF) as well as ERK1 map kinase were analysed. Results 1 μM SVA was identified as highest concentration without an influence on cell growth and cytotoxicity and was used for further analyses. In terms of early and residual γH2AX-foci, SVA affected the number of foci in both cell lines with or without irradiation. Different radiation responses were detected in 2D and 3D culture conditions. During the 2D cultivation, a radiosensitizing effect within the clonogenic survival was observable, but not in 3D. Conclusion The present study suggests that SVA may have potential for radiosensitization. Therefore, it is important to further investigate the role of SVA in relation to the extent of radiosensitization and how it could be used to positively influence the therapy of breast cancer or other entities.

Statins Alleviate Tumor Hypoxia in Prostate Cancer Models by Decreasing Oxygen Consumption: An Opportunity for Radiosensitization?

“…Because a meta-analysis described a beneficial effect of statins on prostate cancer patients treated with RT [ 18 ], it seemed crucial to investigate the mechanisms underlying the radiosensitizing properties of statins. Intriguingly, a recent study suggested that simvastatin (µM range) combined with irradiation slightly affects cell growth, clonogenic survival, and the DNA repair capacity of the breast cancer cell line MCF-7 in 2D-culture, but, surprisingly, not in 3D-culture [ 59 ]. Another study described that simvastatin (10 to 500 µM) compromises DNA double-strand break repair by triggering the expression of histone 2A family member X (γ-H2AX) and phospho-checkpoint kinase 1 (p-CHK1), suggesting an underlying mechanism for this radiosensitization of prostate cancer cells (PC3 model) [ 60 ].…”

“…A limitation of our study relies on the statin dosage that has been used in vitro to study the effect of oxygen utilization. While our present study was performed using concentrations consistent with those used in other studies evaluating the impact of statins on tumor cell response [ 3 , 4 , 5 , 6 , 59 , 60 , 61 ], their relevance for immediate translation in humans is debatable. A publication performed a systematic literature search identifying in vitro experiments, where mechanistic insights behind the pleiotropic effects of statins were claimed [ 67 ].…”

3D Breast Tumor Models for Radiobiology Applications

“…In 3D radiobiology studies, researchers have worked with scaffolds, hydrogels, and spheroids to incorporate the third dimension for a wide range of cancers including breast cancers [ 92 ], brain tumors [ 93 , 94 ], lung cancers [ 95 , 96 ], bladder cancer [ 97 ], chondrosarcoma [ 98 ] and oral squamous cell carcinoma [ 99 , 100 ]. The majority of these studies have demonstrated the differential effects of RT on 2D vs 3D cultures.…”

“…Like the 2D studies discussed in the previous section, the 3D studies have also been targeted towards identification and evaluation of radiosensitizers. Complementing radiation treatment with drugs including Olaparib [ 105 ], Valproic acid [ 106 ], Mebendazole [ 46 ], Vinblastine [ 107 ], Trastuzumab [ 108 ], Vorinostat [ 109 ], Simvastatin [ 92 ], has been shown to affect the radiosensitivity of breast cancer cells. Interestingly, some of these studies have shown varying responses to the same drug in the monolayer culture vs 3D cultures.…”

“…This difference in observed effects of Valproic acid has been attributed to the self-renewal promoting culture conditions in 3D when compared to the differentiated cell cultures of 2D [ 106 ]. In another study, Simvastatin could effectively radiosensitize monolayer cultures of normal and cancerous breast cells but did not elicit a radiation response in 3D cultures [ 92 ]. Again, these results highlight the importance of working with physiologically relevant 3D models during the preclinical phase.…”