Abstract 3346: The ketone body β-hydroxybutyrate increases radiosensitivity in glioma cell lines in vitro

Abstract

Glioblastoma (GB) is the most common and aggressive primary malignant brain tumor. Despite aggressive treatment, including maximum surgical resection followed by both chemotherapy and radiotherapy, median survival for patients remains at approximately 1.5 years after diagnosis. Recent preclinical studies examining the potential of the ketogenic diet (KD) as an adjuvant therapy for the treatment of malignant gliomas demonstrated that animals fed a KD and treated with chemotherapy or radiation survived significantly longer than those treated with chemotherapy or radiation and fed a standard diet. One of the key results of the KD is an increase in the blood level of the ketone body β-hydroxybutyrate (BHB). To more fully examine the mechanism through which the KD potentiates radiation, we examined the potential of BHB to increase radiosensitivity in mouse glioma cells in vitro. Plating cells in 10mM BHB followed by treatment for 2 weeks following radiation prevented colony formation in both the control and the radiation groups. We therefore assessed the effect of pretreatment with 5mM or 10mM BHB alone prior to radiation with 4 Gy. A statistically significant change in survival was observed when cultures were pre-treated with 10mM BHB for 24 hours prior to irradiation but not with 5mM BHB. However, significant changes in clonogenic survival were observed with a dose of 5mM BHB when cells were treated for 7 days post irradiation, starting 24 hours after irradiation. The effect of BHB on cell growth was then assessed using live cell counts. Both 5mM and 10mM BHB were effective in significantly reducing the cell number by 192 hours post plating. Growth was similarly affected by 10mM BHB or 2 Gy of radiation alone; however, when 10mM BHB was added to 2 Gy of radiation there was a very strong potentiating effect. These data suggest that BHB is an effective radiosensitizer for mouse glioma cells when used alone. In addition, they provide evidence that the extended survival seen in our in vivo mouse model of glioma when radiation is used in addition to the ketogenic diet may be modulated, to a large extent, by blood ketone levels. Whether this is due to differences in radiation-induced DNA damage, DNA repair or changes in the growth rate of the tumor cells is currently under investigation. Citation Format: Alex P. Rossi, Eric C. Woolf, Kenneth S. Brooks, Marshall J. Fairres, Adrienne C. Scheck. The ketone body β-hydroxybutyrate increases radiosensitivity in glioma cell lines in vitro. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3346. doi:10.1158/1538-7445.AM2015-3346

Targeting the Warburg effect for cancer treatment: Ketogenic diets for management of glioma

“…Indeed, preliminary studies have demonstrated that the KD enhances OxS-mediated radiation-induced DNA damage in glioma, but reduces it in surrounding healthy tissue [58]. However, Scheck and colleagues recently presented findings that βHB itself potentiates radiation therapy and increases radiosensitivity of glioma cells in vitro, regardless of glucose concentration [121]. A reduction in c-Myc expression, an oncogene known to play a vital role in DNA repair, was also observed thus suggesting ketone-enhancement of radiotherapy may be mediated via a signaling mechanism [116].…”

“…Scheck and colleagues reported in a series of studies that the KD fed ad libitum increases median survival time by approximately 20-30% in the GL-261 malignant glioma model [63,117,121]. Poff et al reported that two KDs tested prolonged survival time by approximately 45% and 55% in a glioma-derived mouse model of metastatic cancer [12,126].…”

Tumor Metabolism, the Ketogenic Diet and β-Hydroxybutyrate: Novel Approaches to Adjuvant Brain Tumor Therapy

“…In vitro investigations demonstrated that βHB is able to recapitulate, in part, the in vivo effects of the full KD (Skinner et al, 2009; Rossi et al, 2015). This suggests that the ketone bodies themselves possess antitumor effects, and that perhaps the effects of the KD are mediated, at least in part, by the ketone bodies.…”

“…In vitro studies using βHB demonstrated that, even in the presence of high glucose, physiologically relevant doses of βHB reduced proliferation of several human glioblastoma cell lines, two human cancer stem cell lines, and a murine glioma cell line. Additionally, similar treatment with βHB resulted in potentiation of low doses of ionizing radiation therapy in both sensitive and resistant populations (Rossi et al, 2015; Silva-Nichols et al, 2015). Further, in a separate study βHB potentiated the chemotherapeutic agent 1,3-bis(2-chloroethyl)-1 nitrosourea (BCNU, carmustine) in a cell line derived from a recurrent human glioblastoma (Scheck et al, 2012).…”

Combination of Thymoquinone and Intermittent Fasting as a Treatment for Breast Cancer Implanted in Mice

“…This heightened glycolytic activity stimulates the pentose phosphate pathway, generating two molecules of nicotinamide adenine dinucleotide phosphate (NADPH), which are crucial for mitigating oxidative stress within cancer cells [40]. Physiologically relevant doses of β-HB effectively restrained the growth of various human glioblastoma cell lines and a murine glioma cell line in vitro, despite high glucose levels, as demonstrated by earlier studies [41,42]. In our study, the levels of β-HB were increased using IF (Figure 5).…”