RB1 and cancer: For this, we investigated (i) whether ICBP90 shares structural features with other proteins exhibiting known properties; (ii) the expression of ICBP90, TopoIIα and pRB in various cell lines; (iii) the effects of E2F-1 overexpression on TopoIIα and ICBP90 expression; (iv) the cell-cycle-dependent expression of ICBP90 in normal cells vs cancer cells; and (v) the ICBP90 expression in primary breast carcinoma tissue vs noncancer breast tissue.