OVEREXPRESSION OF THE HOX4A (HOXD3) HOMEOBOX GENE IN HUMAN ERYTHROLEUKEMIA HEL CELLS RESULTS IN ALTERED ADHESIVE PROPERTIES

We previously isolated the human homeobox gene HOX4A (HOXD3) on chromo some 2 from a human genomic library and determined its nucleotide sequ ence. In the present study, expression of the HOX4A gene was investiga ted in human hematopoietic cell lines. Reverse transcriptase-mediated polymerase chain reaction analysis showed that the HOX4A gene was expr essed in erythroleukemia HEL and K562 cells but not in promyelocytic l eukemia HL-60 cells. To study the role of the HOX4A gene in erythropoi esis, expression vectors containing the HOX4A gene in the sense or ant isense orientation were introduced into HEL cells. The sense transfect ants overexpressing the HOX4A gene formed aggregates, which were compo sed of densely associated cells adhering to tissue-culture dishes, whe reas the parental HEL cells and antisense transfectants adhered poorly to the dishes. Furthermore, the sense transfectants overexpressing th e HOX4A gene attached more efficiently to fibronectin and collagen tha n did the antisense transfectants and parental HEL cells. Northern blo t analysis showed that integrin beta 3 mRNA levels were significantly increased in the HEL cells overexpressing the HOX4A gene, whereas the integrin beta 1 and alpha IIb mRNA levels did not show a distinct corr elation with HOX4A mRNA levels. Fluorescence-activated cell sorting an alysis showed that the sense transfectants overexpressing the HOX4A ge ne expressed increased levels of integrin alpha IIb beta 3 (GP IIb-III a) complex as compared with the parental HEL cells and antisense trans fectants. These results implicate the homeobox gene HOX4A in the regul ation of cell adhesion processes. (C) 1995 by The American Society of Hematology.