Berberine Induces Apoptosis In Acute Lymphoblastic Leukemia Cells by Demethylation of RASSF1A and Self-Ubiquitination of MDM2.

Abstract 3627

Berberine, an isoquinoline alkaloid derived from a plant used in Chinese herbal medicine, is reported to exhibit anti-proliferative and pro-apoptotic effects on human cancer; however, its mechanism of action is not clearly defined. Herein, we demonstrate that berberine induces apoptosis in acute lymphoblastic leukemia (ALL) cells by demethylation of the tumor suppressor RASSF1A, which results in self-ubiquitination and degradation of the oncoprotein MDM2. In contrast to the conventional chemotherapeutic drug doxorubicin, which directly induced p53 activation and a subsequent upregulation of MDM2, berberine strongly induced persistent downregulation of MDM2 followed by a steady-state activation of p53, which resulted in apoptosis of ALL cells tested, even if they were doxorubicin-resistant. Our investigation discovered that berberine but not doxorubicin can induce demethylation of RASSF1A in RASSF1A-methylated ALL. The result of RASSF1A demethylation was the increased expression of the tumor suppressor, which disrupted the MDM2-DAXX-HAUSP complex, thereby promoting MDM2 self-ubiquitination and subsequent MDM2 degradation. Consistent with this finding, the most potent apoptosis was induced by berberine in wild-type p53 ALL cells with both RASSF1A methylation and MDM2 overexpression, while no pro-apoptotic effect was detected in berberine-treated RASSF1A normal ALL cells that had no or low level of MDM2 expression. Given that ALL cells with RASSF1A methylation and MDM2 overexpression are commonly chemotherapy-resistant our finding that these cells can be potently killed by berberine through effective induction of RASSF1A and inhibition of MDM2 suggests that this naturally-derived agent may have a highly useful role in the treatment of patients with refractory ALL.