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AZD1208 and quizartinib co-treatment was well tolerated in the orthotopic model.

The USP9X inhibitor WP1130 enhances induction of apoptosis of Ba/F3-ITD and MV4-11 cells by quizartinib in a concentration-dependent manner.

Pim kinase and FLT3 inhibition does not enhance induction of apoptosis of cells with FLT3-WT.

Quizartinib, sorafenib, crenolanib and gilteritinib cytotoxicity in cell lines with FLT3-ITD or FLT3-WT

Post-transcriptional regulation of Mcl-1 expression.

Purpose: fms-like tyrosine kinase 3 internal tandem duplication (FLT3-ITD) is present in 30% of acute myeloid leukemia (AML), and these patients have short disease-free survival. FLT3 inhibitors have limited and transient clinical activity, and concurrent treatment with inhibitors of parallel or downstream signaling may improve responses. The oncogenic serine/threonine kinase Pim-1 is upregulated downstream of FLT3-ITD and also promotes its signaling in a positive feedback loop, suggesting benefit of combined Pim and FLT3 inhibition.Experimental Design: Combinations of clinically active Pim and FLT3 inhibitors were studied in vitro and in vivo.Results: Concurrent treatment with the pan-Pim inhibitor AZD1208 and FLT3 inhibitors at clinically applicable concentrations abrogated in vitro growth of FLT3-ITD, but not wild-type FLT3 (FLT3-WT), cell lines. AZD1208 cotreatment increased FLT3 inhibitor–induced apoptosis of FLT3-ITD, but not FLT3-WT, cells measured by sub-G1 fraction, annexin V labeling, mitochondrial membrane potential, and PARP and caspase-3 cleavage. Concurrent treatment with AZD1208 and the FLT3 inhibitor quizartinib decreased growth of MV4-11 cells, with FLT3-ITD, in mouse xenografts, and prolonged survival, enhanced apoptosis of FLT3-ITD primary AML blasts, but not FLT3-WT blasts or remission marrow cells, and decreased FLT3-ITD AML blast colony formation. Mechanistically, AZD1208 and quizartinib cotreatment decreased expression of the antiapoptotic protein Mcl-1. Decrease in Mcl-1 protein expression was abrogated by treatment with the proteasome inhibitor MG132, and was preceded by downregulation of the Mcl-1 deubiquitinase USP9X, a novel mechanism of Mcl-1 regulation in AML.Conclusions: The data support clinical testing of Pim and FLT3 inhibitor combination therapy for FLT3-ITD AML. Clin Cancer Res; 24(1); 234–47. ©2017 AACR.

Supplementary figure legends

AZD1208 and quizartinib co-treatment does not increase celluar ROS generation, but increases mitochondrial ROS generation.

Enhanced apoptosis of Ba/F3-ITD and 32D/ITD cells treated with FLT3 inhibitors at serial concentrations in the presence of AZD1208.

Combined AZD1208 and quizartinib treatment does not abrogate growth of KG-1a cells, expressing FLT3-WT, in a xenograft model.

Ovarian carcinomas are categorized into five major histotypes, each characterized by distinct differences in grade at diagnosis, presentation with metastatic disease, and clinical responses to treatments. Microtentacles (McTNs), microtubule-based extensions of the plasma membrane, were initially described on cells of nongynecologic primaries with high metastatic potential but have not been extensively explored in ovarian carcinomas. In this study, we investigated whether ovarian cancer cells exhibit McTNs as well as the effect of microtubule-targeted drugs on ovarian cancer McTNs. We analyzed 3 immortalized ovarian surface epithelium cell lines (IOSE), 8 clear-cell (OCCC), 3 low-grade serous (LGS), and 6 high-grade serous (HGS) ovarian cancer cells for McTN phenotype, length, and number, using a novel tethering platform in which cells are suspended but stationary, allowing for analysis via confocal microscopy. Additionally, selected cell lines were also treated with microtubule-targeting agents, including paclitaxel, ixabepilone, vinblastine, and colchicine and the effects on McTN dynamics and functions were analyzed. Tubulin subtype expression and post-translational modifications (PTM) were characterized by Western blot. Unpaired t-tests were used to describe differences between McTN length and number. We observed 4 patterns of McTN expression: absent (A), symmetric-short (SS), symmetric-long (SL), and tufted (T). In some cases, multiple morphologies were observed within the same cell line. LGS and OCCC expressed fewer McTNs per cell than HSC. McTNs were shorter among OCCC compared to HGS; whereas LGS expressed a range of McTN lengths similar to those observed in HGS. We also observed differences in the expression of the PTM between the different ovarian cancer subtypes, including alterations in alpha tubulin-stabilizing modifications such as glu-tubulin and acetylated tubulin, as well as proteins involved in actin cortex stability. Increased acetylated tubulin was associated with increased McTN number and length in HGS cells. Microtubule-destabilizing drugs such as colchicine and vinblastine led to a decrease in McTN formation. Ovarian cancer metastasis typically occurs through shedding of the main tumor into the peritoneal space, and the spread of disease is the leading cause of mortality. Studying McTN function and response to chemotherapeutics allows us to improve our understanding of ovarian cancer metastasis and the effect of microtubule-targeting compounds on the spread of ovarian cancer. Citation Format: Cong (Ava) Fan, Sulan Wu, Jocelyn Reader, Eleanor Claire-Higgins Ory, Cornell Lee, McMillan Ching, Trevor Mathias, Julia Ju, Rachel Lee, Michele Vitolo, Stuart Martin, Christopher Jewell, Amy Fulton, Gautam Rao, Mark Carey, Dana M. Roque. Characterization of microtentacle phenotype and function in ovarian carcinomas [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research; 2019 Sep 13-16, 2019; Atlanta, GA. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(13_Suppl):Abstract nr B68.