PTK2B and malignant colon neoplasm: Pawlikowski M et al. (1998) [50], studied the differential effects of somatostatin and octreotide on pituary tyrosin kinase (PTK), and showed that in the case of colonic cancer, the native somatostatin was more effective in inhibiting PTK than octreotide which is active only at the highest concentration studied (10-5 M) and surprisingly is much less active in comparison to native somatostatin.