Cloning, expression and cytotoxicity of granulin A, a novel polypeptide contained in human progranulin.

In our previous study, we isolated an antitumor polypeptide, CS5931, from the sea squirt Ciona savignyi; it shares high homology with Ciona intestinalis Granulin A (GRN A). However, little is known about the anticancer effect of GRN A. In the present study, GRN A was cloned and expressed in the yeast Pichia pastoris. The polypeptide was purified to almost homogeneity using a Ni-NTA column. MTT [3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide] assay reveals that GRN A displays potent cytotoxicity to several human cancer cells. The polypeptide induces cell apoptosis as analyzed by morphological observation and flow cytometry assays. This study provides evidence that GRN A possesses potential to be developed as a novel anticancer agent.