부산대학교 도서관

Arsenic trioxide (As[SUB2]O[SUB3]) is an effective treatment for acute) promyelocytic leukemia (APL), but is less effective against (other leukemias. Although the response of APL cells to As[SUB2]O[SUB3] has been linked to degradation of the PML/RARα fusion oncoprotein, there is evidence that PML/RARα expression is not the only mediator of arsenic sensitivity. Indeed, we found that exogenous expression of PML/RARα did not sensitize a non-APL leukemic line to As[SUB2]O[SUB3]. To evaluate possible other determinants of sensitivity of leukemic cells to As[SUB2]O[SUB3], we derived two arsenic-resistant NB4 subclones. Despite being approximately 10-fold more resistant to arsenic than their parental cell line, PML/RARα protein was still degraded by As[SUB2]O[SUB3] in these cells, providing further evidence that loss of expression of the oncoprotein does not confer arsenic sensitivity. Both arsenic-resistant clones contained high glu-tathione (GSH) levels, however, and we found that GSH depletion coupled with As[SUB2]O[SUB3] treatment dramatically inhibited their growth. Annexin V-staining and TUNEL analysis con-firmed a synergistic induction of apoptosis. In addition, these cells failed to accumulate ROS in response to arsenic treatment, in contrast to their arsenic-sensitive parental cells, unless cotreated with buthionine sulfoximine. While other malignant cells did not show a good correlation between arsenic sensitivity and GSH content, GSH depletion nevertheless sensitized all cell lines examined, regardless of their initial response to arsenic alone. These findings suggest that PML/RARα expression is not a determinant of arsenic sensitivity, and further support the coupling of GSH depletion and arsenic treatment as a novel treatment for human malignancies that are unresponsive to arsenic alone. [ABSTRACT FROM AUTHOR]