Nucleophosmin (NPM, also known as B23), mainly localized in the nucleolus, has been reported to be overexpressed in many types of human
cancer, including colon, ovarian, prostate and
gastric cancer. NPM was identified while screening the differential
nuclear matrix proteins during
HMBA-induced differentiation of human
liver cancer cells. We investigated the aberrant expression and subcellular localization of NPM in clinical
liver cancer tissues and a cell line with the aim of providing more evidence for revealing the roles of NPM on regulating
liver cancer cell proliferation and differentiation. In addition, we studied the potential interaction between NPM and several important
proteins. Our results revealed that NPM
protein was overexpressed in
cancer cells, which was in accordance with the overexpressed
mRNA in
cancer tissues compared to the corresponding non-
cancer tissues. We also found a decrease of NPM in
protein and
mRNA levels upon treatment with the differentiation
reagent HMBA. We focused on the aberrant localization of NPM. Immunochemistry and immunofluorescence revealed aberrant cytoplasmic and nucleoplasm localization of NPM in
liver cancer tissues and its colocalization with c-Myc, c-Fos, P53 and Rb in the SMMC-7721 cell line. The interactions between NPM and the above
proteins were confirmed by GST pull-down assay and co-immunoprecipitation assay. These findings indicate that NPM plays a regulatory role in
liver cancer, which deserves in-depth investigation.