Preprint / Version 1

Synergistic Inhibition of Glioma Cell Proliferation by Withaferin A and Tumor Treating Fields

Authors

  • Edwin Chang Department of Radiology, Molecular Imaging Program at Stanford, Canary Center for Early Cancer Detection, Stanford University, Palo Alto, California, USA
  • Christoph Pohling Department of Radiology, Molecular Imaging Program at Stanford, Canary Center for Early Cancer Detection, Stanford University, Palo Alto, California, USA
  • Nooshin Beygui Scripps College, Claremont, California, USA
  • Chirag Patel Department of Radiology, Molecular Imaging Program at Stanford, Canary Center for Early Cancer Detection, Stanford University, Palo Alto, California, USA
  • Jarrett Rosenberg Department of Radiology, Molecular Imaging Program at Stanford, Canary Center for Early Cancer Detection, Stanford University, Palo Alto, California, USA
  • Dong Ha Department of Radiology, Molecular Imaging Program at Stanford, Canary Center for Early Cancer Detection, Stanford University, Palo Alto, California, USA
  • Sanjiv Gambhir Department of Radiology, Molecular Imaging Program at Stanford, Canary Center for Early Cancer Detection, Stanford University, Palo Alto, California, USA

Keywords:

Alternating electric fields, combination therapy, glioblastoma, synergy, tumor treating fields, Withaferin A

Abstract

BACKGROUND Glioblastoma (GBM) is the most aggressive and lethal form of brain cancer. Standard therapies are non-specific and often of limited effectiveness; thus, efforts are underway to uncover novel, unorthodox therapies against GBM. In previous studies, we investigated Withaferin A, a steroidal lactone from Ayurvedic medicine that inhibits proliferation in cancers including GBM. Another novel approach, tumor treating fields (TTFields), is thought to disrupt mitotic spindle formation and stymie proliferation of actively dividing cells. We hypothesized that combining TTFields with Withaferin A would synergistically inhibit proliferation in glioblastoma. METHODS Human glioblastoma cells (GBM2, GBM39, U87-MG) and human breast adenocarcinoma cells (MDA-MB-231) were isolated from primary tumors. The glioma cell lines were genetically engineered to express firefly luciferase. Proliferative potential was assessed either by bioluminescence imaging or cell counting via hemocytometer. RESULTS TTFields (4 V/cm) significantly inhibited growth of the four cancer cell lines tested (n=3 experiments per time point, 4 measurements per sample, p<0.02 at least; 2-way ANOVA, control vs. treatment). The combination of Withaferin A (10–100 nM) with TTFields significantly inhibited the growth of the glioma cells to a degree beyond that of Withaferin A or TTFields alone. The interaction of the Withaferin A and TTFields on glioma cells was found to be synergistic in nature (p<0.01, n=3 experiments). These findings were validated by both bioluminescence and hemocytometric measurements. CONCLUSIONS The combination of Withaferin A with TTFields represents a novel approach to treat GBM in a manner that is likely better than either treatment alone and that is synergistic. Keywords: Alternating electric fields, combination therapy, glioblastoma, synergy, tumor treating fields, Withaferin A

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