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Despite recent relevant therapeutic progresses, chronic lymphocytic leukemia (CLL) remains an incurable disease. Selinexor, an oral inhibitor of the nuclear export protein XPO1, is active as single agent in different hematologic malignancies, including CLL. The purpose of this study was to evaluate the anti-tumor effects of selinexor, used in combination with chemotherapy drugs (i.e. fludarabine and bendamustine) or with the PI3Kδ inhibitor idelalisib in CLL. Our results showed a significant decrease in CLL cell viability after treatment with selinexor-containing drug combinations compared to each single compound, with demonstration of synergistic cytotoxic effects. Interestingly, this drug synergism was exerted also in the presence of the protective effect of stromal cells. From the molecular standpoint, the synergistic cytotoxic activity of selinexor plus idelalisib was associated with increased regulatory effects of this drug combination on the tumor suppressors FOXO3A and IkBα compared to each single compound. Finally, selinexor was also effective in potentiating the in vivo anti-tumor effects of the PI3Kδ inhibitor in mice treated with the drug combination compared to single agents. Our data provide preclinical evidence of the synergism and potential efficacy of a combination treatment targeting XPO1 and PI3Kδ in CLL. [ABSTRACT FROM AUTHOR]

Despite recent relevant therapeutic progresses, chronic lymphocytic leukemia (CLL) remains an incurable disease. Selinexor, an oral inhibitor of the nuclear export protein XPO1, is active as single agent in different hematologic malignancies, including CLL. The purpose of this study was to evaluate the anti-tumor effects of selinexor, used in combination with chemotherapy drugs (i.e. fludarabine and bendamustine) or with the PI3Kδ inhibitor idelalisib in CLL. Our results showed a significant decrease in CLL cell viability after treatment with selinexor-containing drug combinations compared to each single compound, with demonstration of synergistic cytotoxic effects. Interestingly, this drug synergism was exerted also in the presence of the protective effect of stromal cells. From the molecular standpoint, the synergistic cytotoxic activity of selinexor plus idelalisib was associated with increased regulatory effects of this drug combination on the tumor suppressors FOXO3A and IkBα compared to each single compound. Finally, selinexor was also effective in potentiating the in vivo anti-tumor effects of the PI3Kδ inhibitor in mice treated with the drug combination compared to single agents. Our data provide preclinical evidence of the synergism and potential efficacy of a combination treatment targeting XPO1 and PI3Kδ in CLL. [ABSTRACT FROM AUTHOR]

The genetic lesions identified in chronic lymphocytic leukemia (CLL) do not entirely recapitulate the disease pathogenesis and the development of serious complications, such as chemorefractoriness. While investigating the coding genome of fludarabine-refractory CLL, we observed that mutations of SF3B1, encoding a splicing factor and representing a critical component of the cell spliceosome, were recurrent in 10 of 59 (17%) fludarabine-refractory cases, with a frequency significantly greater than that observed in a consecutive CLL cohort sampled at diagnosis (17/301, 5%; P = .002). Mutations were somatically acquired, were generally represented by missense nucleotide changes, clustered in selected HEAT repeats of the SF3B1 protein, recurrently targeted 3 hotspots (codons 662, 666, and 700), and were predictive of a poor prognosis. In fludarabine-refractory CLL, SF3B1 mutations and TP53 disruption distributed in a mutually exclusive fashion (P = .046). The identification of SF3B1 mutations points to splicing regulation as a novel pathogenetic mechanism of potential clinical relevance in CLL. [ABSTRACT FROM AUTHOR]