High grade gliomas (HGGs) are primary CNS cancers with more than 95% of patients experiencing tumor
recurrence following radiation therapy, chemotherapy, and/or an anti-angiogenic therapy. Populations of glioma
‘stem-like’ cells (GSCs) exist in both proliferative and non-proliferative states and are capable of tumor regrowth.
These GSCs survive within hypoxic tumor regions and avascular tumor margins, while retaining the capability to
regenerate. Successful treatment of HGGs depends on therapeutic targeting of GSCs to avert tumor regeneration.
Here, we review novel intracellular mechanisms by which 3-amino-5-arylamino-6-chloro-N-(diaminomethylene)
pyrazine-2-carboximide (UCD38B) and the much more potent 5’-substituted arylamino compounds (cmpd 10357)
irreversibly kill GSCs utilizing caspase-independent, programmed necrotic cell death. Drug-induced relocation of a
subset of endosomes to perinuclear mitochondria triggers the mitochondrial release and nuclear translocation of
apoptosis inducible factor (AIF) that is followed by nuclear condensation and cancer cell demise. This drug-induced
endosomal ‘mis-trafficking’ affects a subset of endosomes containing proteins belonging to the urokinase
plasminogen activator system (uPAS) and guided by lipoprotein receptor protein type 1 (LRP-1). UCD38B and
congeners act intracellularly and bind to intracellular urokinase plasminogen activator (uPA) to disrupt uPA binding
to PAI-1 and the endosomal LRP-1 guidance protein. These small molecules are cytotoxic to persistently hypoxic
and acidotic HGG cell lines and to high grade gliomas from patient derived xenografts (PDX). Immunodeficient
mice with intracerebral PDX glial tumors demonstrate drug-specific, AIF- mediated necrosis after 24h of treatment.
The propensity of these small molecules to kill non-proliferating and proliferating hypoxic GSCs, suggests a
potential synergistic therapeutic role with radiotherapy, anti-mitotic and anti-angiogenic therapies.
Keywords: Anti-cancer small molecules, high grade glioma ‘stem-like’ cells, endosomal urokinase proteins, programmed necrosis, 3-amino-5-arylamino-6-chloro-N-(diaminomethylene) pyrazine-2-carboximide.
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