STAT3 and central nervous system cancer: Glioma cell treatment with N6,2′-O-dibutyryl cAMP (Bt2AMP) and theophylline caused delayed phosphorylation of the signal transducer and the activator of transcription-3 (STAT3) as well as expression of an astrocyte marker, glial fibrillary acidic protein (GFAP) [17].