- Chondroitin sulfate of appican, the proteoglycan form of amyloid precursor protein, produced by C6 glioma cells interacts with heparin-binding neuroregulatory factors. Umehara, Y., Yamada, S., Nishimura, S., Shioi, J., Robakis, N.K., Sugahara, K. FEBS Lett. (2004)