Targeting the SUMO pathway primes all-trans retinoic acid-induced differentiation of non-promyelocytic acute myeloid leukemias

Differentiation therapies using all-trans retinoic acid (ATRA) are highly efficient at treating acute promyelocytic leukemia (APL), a subtype of acute myeloid leukemia (AML). However, their efficacy, if any, is limited in the case of non-APL AML. We report here that inhibition of SUMOylation, a post-translational modification related to ubiquitination, restores the pro-differentiation and anti-proliferative activities of retinoids in non-APL AML. Controlled inhibition of SUMOylation with pharmacological inhibitors 2-D08 or anacardic acid, or via overexpression of SENP deSUMOylases, enhanced the ATRA-induced expression of key genes involved in differentiation, proliferation, and apoptosis in non-APL AML cells. This activated ATRA-induced terminal myeloid differentiation and reduced cell proliferation and viability, including in AML cells resistant to chemotherapeutic drugs. Conversely, enhancement of SUMOylation via overexpression of SUMO-conjugating enzyme Ubc9 dampened expression of ATRA-responsive genes and prevented differentiation. Thus, inhibition of the SUMO pathway is a promising strategy to sensitize non-APL AML patients to retinoids and improve the treatment of this poor-prognosis cancer.

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