Overexpression of the homeobox gene DLX-7 inhibits apoptosis by induced expression of intercellular adhesion molecule-1.
OBJECTIVE
DLX genes constitute a subfamily of divergent homeobox genes. We have previously reported that inhibition of DLX-7 expression by an antisense oligonucleotide caused apoptosis in the K562 erythroleukemia cell line, which highly expresses DLX-7. In this study, we have constructed an expression vector encoding human DLX-7, and examined the effects of overexpression of DLX-7 in the IL-3-dependent lymphoid precursor cell line Ba/F3.


METHODS
DLX-7 expression vector was electroporated into Ba/F3 cells, and generate a DLX-7 expressing Ba/F3 cells. Northern blot analysis was performed to determine DLX-7 gene expression. WST-1 assay was used to cell proliferation assay. To detect apoptosis, we performed TUNEL assay. Expression of cell surface adhesion molecules was examined by FACS analysis.


RESULTS
Growth properties of DLX-7-transfected Ba/F3 cells in the presence of IL-3, did not differ from those of control Ba/F3 cells. However, in the absence of IL-3, DLX-7-transfected cells abrogated growth dependence on cytokines due to inhibition of apoptosis. Because adhesion properties of DLX-7-transfected cells increase, we examined expression of adhesion molecules in these cells. Expression of intercellular adhesion molecule (ICAM)-1 and ICAM-2 were markedly upregulated in DLX-7-transfected cells. Both anti-ICAM-1 antibody and anti-LFA-1 antibody blocked the aggregation of DLX-7-transfected cells. Moreover, in the absence of IL-3, cytokine-independent cell growth was blocked by anti-ICAM-1 antibody.


CONCLUSIONS
These results indicate that DLX-7 overexpression blocks apoptosis and that ICAM-1 expression induced by DLX-7 contributes to this antiapoptotic effect.
Shimamoto
T
T
First Department of Internal Medicine, Tokyo Medical University, Tokyo, Japan. takashis@cb3.so-net.ne.jp
Ohyashiki
K
K
Takeshita
K
K
D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D017209:Apoptosis; D002448:Cell Adhesion / Q000187:drug effects / Q000235:genetics; D015815:Cell Adhesion Molecules / Q000096:biosynthesis / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects / Q000235:genetics; D002460:Cell Line; D048429:Cell Size / Q000235:genetics; D016044:Fusion Proteins, bcr-abl / Q000096:biosynthesis; D015870:Gene Expression / Q000235:genetics; D018398:Homeodomain Proteins / Q000096:biosynthesis* / Q000235:genetics; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000096:biosynthesis* / Q000187:drug effects; D007377:Interleukin-3 / Q000494:pharmacology; D051379:Mice; D008819:Mice, Nude; D012333:RNA, Messenger / Q000096:biosynthesis; D014157:Transcription Factors; D014162:Transfection
D000911:Antibodies, Monoclonal; D015815:Cell Adhesion Molecules; C104149:Dlx4 protein, mouse; D018398:Homeodomain Proteins; D007377:Interleukin-3; D012333:RNA, Messenger; D014157:Transcription Factors; D018799:Intercellular Adhesion Molecule-1; D016044:Fusion Proteins, bcr-abl