Functional analysis of HOXB9 expression in HL cell lines. (A) HL cells (HDLM-2 and KM-H2) and NHL cells (SC-1) were treated with antisense oligonucleotide (AS) directed against HOXB9. In contrast to SC-1, HL cell lines showed reduced growth after 3 days of incubation with AS-HOXB9. (B) KM-H2 cells were electroporated with siRNA directed against HOXB9 or control siRNA and were subsequently incubated in the presence/absence of fetal bovine serum (FBS) or with TPA. Cell counts indicate 60% reduction of viability in the absence of FBS and about 25% in the other settings. Cell counts are related to control siRNA treatment in the presence of FBS. (C) In KM-H2 and HELA cells HOXB9 was overexpressed using expression construct pcHOXB9 in the presence or absence of FBS, respectively. Cell counts of treatments with control vector pcDNA3 in the presence of FBS were set at 100%. In the absence of FBS, both cell lines showed enhanced growth/survival following HOXB9 overexpression. In the presence of FBS only KM-H2 cells showed increased cell counts, indicating cell-type–specific differences. All experiments were performed twice with similar results; error bars indicate SD.