An investigation of the antitumor peptidoglycan fraction from squid ink.

Squid ink, which has little commercial use and is usually discarded, was extracted using a Tris-HCl buffer (pH 6.8). The extract was fractionated using DEAE Sephacel ion-exchange chromatography and Sephacryl S-300 gel filtration to give a peptidoglycan fraction which exhibited strong antitumor activity against Meth-A fibrosarcoma in BALB/c mice following intraperitoneal administration. The fraction was composed of 7.8% peptide, 57% polysaccharide and 30% pigment. The polysaccharide component had a unique structure with equimolar ratios of GlcA, GalNAc and Fuc. Since the fraction has no direct cytotoxic effect on Meth-A cells, inhibition of tumor growth may be due to stimulation of host-mediated responses.