Anti-Leukemic Effects of Velcrin in SLFN12-Expressing Acute Myeloid Leukemia
Schlafen 12 (SLFN12) is a member of the Schlafen (SLFN) family of proteins, a group of interferon-stimulated genes with diverse roles in cellular regulation with implications for human malignancies. Accumulating evidence indicates that SLFN family proteins may serve as prognostic markers across various cancer types. In acute myeloid leukemia (AML), SLFN12 is notably overexpressed, which prompted us to investigate its potential as a therapeutic target. Employing a panel of leukemia cell lines, we explored the effects of velcrins, a class of small molecules able to modulate SLFN12 biological activity. Mechanistic studies showed that velcrin treatment increases expression of SLFN12 and promotes SLFN12 complex formation with PDE3A or PDE3B. Functionally, these effects were associated with growth inhibition and induction of apoptosis. Further, velcrin treatment induced potent suppressive effects on the clonogenic capability of primary human AML progenitors and suppressed tumor growth and significantly extended survival in a mouse AML xenograft model. Taken together, these findings highlight the potential of using velcrins as a promising therapeutic strategy for the treatment of AML patients. Overall design: Animal experiment protocols were approved by the Northwestern University Institutional Animal Care and Use Committee and performed accordingly. 5–6-week-old NU/NU nude female mice were acquired from Charles River laboratories (Strain Code 088). To induce flank tumors, 5x106 early passage HEL cells in the logarithmic growth phase were collected, washed, and resuspended in a final volume of 100 µL in PBS and loaded into a U-100 insulin syringe with an attached 27-gauge needle and injected into the right flank.  Approximately 13 days after injection, once tumors were palpable, tumor measurements were collected and mice were randomized into two treatment groups: vehicle control or treatment with a velcrin (BAY 2666605), with 5 mice per group. Mice were treated with vehicle control or BAY 2666605 (5 mg/kg), which was administered orally, twice daily for 2 weeks, with two days off. Tumor size was measured three times per week by caliper and the formula was calculated as follows (D × d2)* p/6, where D is the longest diameter and d is the shorter diameter.  Body weights and clinical observations were recorded 3 times per week.  For survival, mice were observed daily and all animals were compassionately euthanized 30 minutes following the last treatment dose. Tumor sections (n=4 per experimental group) were subsequently processed for SDS page or RNA-seq analysis.