On the other hand, Wadhwa et al. (2003) have found a high TrkA and TrkB expression in low grade astrocytic tumors (grade I and grade II) and a down regulation of both Trk receptors in high grade tumors (grade III and grade IV) and concluded that these receptors may contribute to progression towards malignancy [17]. Here, NTRK1 is linked to astrocytic tumor.