EGFR and glioblastoma: In response to GBM radioresistance, radiosensitizing drugs are being developed with a variety of modes of action, aimed at altering the activity of cellular factors, targeting the epidermal growth factor receptor (EGFR), histone deacetylase, DNA damage pathways, cell cycle regulators, cell death receptors, and modulating angiogenesis or tumor hypoxic conditions.