NEOPLASIA Expression of Human Inducible Nitric Oxide Synthase Gene in T-Cell Lines Infected With Human T-Cell Leukemia Virus Type-I and Primary Adult T-Cell Leukemia Cells

We examined the expression of messenger RNA (mRNA) of the human inducible nitric oxide synthase (hiNOS) gene in a panel of human T-cell lines. Reverse transcriptase-polymerase chain reaction showed that human T-cell leukemia virus type-I (HTLV-I)–infected T-cell lines (MT-1, SLB-1, and C5/MJ) expressed mRNA for the hiNOS, but TL-Om1 or uninfected Jurkat, H9, and CCRF-CEM did not. The MT-1, SLB-1, and C5/MJ cell lines are infected with HTLV-I and express the viral transactivator Tax, whereas TL-Om1 cells, although derived from adult T-cell leukemia (ATL) leukemic cells, do not express Tax. There was, thus, a correlation between Tax and hiNOS mRNA expression. The transcriptional regulatory region of the hiNOS gene was activated by Tax in Jurkat, in which endogenous hiNOS is induced by Tax. Deletion analysis showed that the region of hiNOS encompassing nucleotides 2159 to 2111 contained the minimum Tax-responsive elements. Mutations in the NF-kB element at position 2115 and 2106 bp in the hiNOS promoter were still activated by Tax, and a Tax mutant defective for activation of the NF-kB pathway retained the ability to activate the hiNOS promoter. In addition, overexpression of the dominant-negative mutants of IkBa and I kBb failed to reduce Tax-induced activation of hiNOS gene. Furthermore, hiNOS mRNA was detected in leukemic cells from ATL patients. Our results show that the hiNOS promoter contains a minimum Tax-responsive element located between nucleotides 2159 and 2111, and imply that the expression of the hiNOS gene is involved in the pathogenesis of HTLV-I–associated diseases. r 1999 by The American Society of Hematology.