ENTPD1 and glioblastoma: While the CD73 and CD39 mediated pathway of adenosine production are the most relevant to glioblastoma, extracellular adenosine may also be generated via ecto-phosphodiesterase/pyrophosphatase family proteins, nicotinamide adenine dinucleotide glycohydrolases, prostatic acid phosphatase, and alkaline phosphatase (99, 100).