Investigating the effects of the ketone body ß-hydroxybutyrate and the anti-cancer compound MHP88 on glioblastoma multiforme cells in vitro

Abstract

Introduction: Glioblastoma multiforme (GBM) is the most aggressive human brain tumor with a mean survival of 15 months. It is therefore necessary to explore new treatment strategies, and to study how different hallmarks of cancer can be utilized in this regard. The marine natural product mimic MHP88 can attack the cancer cells’ ability to evade immune destruction by inducing immunogenic cell death and hence work as immunotherapy. The cancer cells’ reprogrammed energy metabolism, including the Warburg effect, can possibly be utilized simultaneously. This hallmark makes the cancer cells highly dependent on glucose for energy production. A ketogenic diet can target this feature by reducing the blood levels of glucose and increasing the blood levels of ketone bodies and may work as an adjuvant treatment for GBM.

Aims: Investigate if the ketone body ß-hydroxybutyrate (BHB) had an adjuvant effect to MHP88 on GBM cells. Examine if the expression of luc2 in the murine glioblastoma cell line GL261-luc2 was constant to prepare for future mouse studies with the ketogenic diet and MHP88.

Method: Five cell lines (two murine glioblastoma, one human glioblastoma, one human fibroblast, one murine cardiac muscle) and primary murine hepatocytes were used. Live-cell imaging, MTS assay, Western blot and bioluminescence measurements were performed.

Results: GL261-luc2 cells died of a glucose deprivation but survived in 3.5 mmol/l glucose. The cell cytotoxicity of MHP88 was either unaffected or decreased when the three glioblastoma cell lines and the fibroblast cell line were cultured in 3.5 mmol/l glucose with 5 or 10 mmol/l BHB. The presence of BHB in the cell media lowered the pH and hence reduced the number of active MHP88 molecules. Expression of the rate-limiting ketolytic enzyme, SCOT, appeared to be low in the GBM cells. The luminescence signal from GL261-luc2 cells varied after selection with G418.

Conclusion: The reduced cell cytotoxicity of MHP88 in the presence of BHB could be attributed to a pH reduction in the cell media. However, additional research is needed. Expression of luc2 in the cell line GL261-luc2 is dependent on selection with G418.