Recently, it has been discovered that some type of cancers (such as hepatocarcinoma, glioblastoma, bladder carcinoma) contained foci of non-tumoral TDO-expressing cells, which were identified as pericytes, that were found in high-grade tumours close to necrotic or hemorrhagic areas, characterized by neoangiogenesis (Hoffmann et al. 2020). This evidence concerns the gene TDO2 and glioblastoma.