Differential expression of nucleostemin in the cytoplasm and nuclei of normal and cancerous cell lines

Abstract

Studies conducted in the past decade have reported nucleostemin (NS) as a nucleolar protein that has a role in self-renewaland cell cycle regulation in cancer/stem cells, but is absent in differentiated cells. The localization and expression patterns of NS havealways been disputed, as reports indicate its varied levels among tissues and cells. This study evaluates the expression and localizationpattern of NS in normal cells, cancer cell lines, and stem cells. Our findings revealed that the expression of NS was high in cancersoriginating from the skin and liver compared to the normal cell lines. NS knockdown affects the proliferation of normal cell lines,similar to cancerous cell lines. The localization pattern of NS was analyzed by immunofluorescence, which showed that NS was localizedin the nuclei of normal cell lines but is present both in the nucleus and the cytoplasm of cancerous/stem cell lines. Interestingly, weobserved that siNS cancerous cell lines had lower NS in the cytoplasm, which did not salvage the reduction in proliferation caused bysiNS. We postulate that the loss of NS in the nucleus inhibits the proliferative ability of both normal and cancerous cells at similar rates,although the role of NS in the cytoplasm apart from proliferation needs to be further explored.