Combination of Imatinib Mesylate and AKT Inhibitor Provides Synergistic Effects in Preclinical Study of Gastrointestinal Stromal Tumor

Abstract

Purpose Gastrointestinal stromal tumors (GIST) generally harbor activating mutations in the receptor tyrosine kinase KIT or in the related platelet derived growth factor receptor alpha (PDGFRA). GIST treated with imatinib mesylate (IM) or second-line therapies that target mutant forms of these receptors generally escape disease control and progress over time. Inhibiting additional molecular targets may provide more substantial disease control. Recent studies have implicated the PI3-kinase/AKT pathway in the survival of IM-resistant GIST cell lines and tumors. Experimental Design Here, we performed in vitro and in vivo studies evaluating the novel combination of IM with the AKT inhibitor MK-2206 in GIST. Whole-transcriptome sequencing (WTS) of xenografts was performed to explore the molecular aspects of tumor response to this novel combination and to potentially identify additional therapeutic targets in GIST. Results This drug combination demonstrated significant synergistic effects in a panel of IM-sensitive and -resistant GIST cell lines. Furthermore, combination therapy provided significantly greater efficacy, as measured by tumor response and animal survival, in IM-sensitive GIST xenografts as compared to treatment with IM or MK-2206 alone. WTS implicated two neural genes, brain expressed X-linked 1 (BEX1) and neuronal pentraxin I (NPTX1), whose expression was significantly up-regulated in combination-treated tumors compared to tumors treated with the two monotherapies. Conclusion These studies provide strong preclinical justification for combining IM with an AKT inhibitor as a front-line therapy in GIST. In addition, the WTS implicated the BCL-2/BAX/BAD apoptotic pathway as a potential mechanism for this enhanced combination effect.

Role of PI3K/AKT pathway in cancer: the framework of malignant behavior

“…MiR-374b modulates proliferation and apoptosis of GIST cells through PI3K/AKT pathway [137]. Combination of imatinib mesylate (IM) and MK2206 provide obviously greater efficacy than treatment with IM or MK2206 alone in vitro and vivo preclinical study of GIST [138]. Furthermore, clinical trials of combination of Imatinib and BKM120 (NCT01468688) or BYL719 (NCT01735968, Table 2) were tested in GIST patients.…”

Identification of Wee1 as Target in Combination with Avapritinib for the Treatment of Gastrointestinal Stromal Tumor

“…Reverse transfection mixtures were assembled in 96-well with final siRNA concentration of 50nM. After seventy-two hours, plates were assayed for cell viability using the CellTiter Blue (CTB) Viability Assay (Promega, Madison, WI) as previously described (47).…”

“…All studies involving animals followed procedures approved by the FCCC Institutional Animal A total of 64 mice were used in this study. Tumor volume was calculated as described previously (47). When tumors reached approximately 300 mm 3 xenograft tumor growth were observed due to treatment with avapritinib (*p = 0.05 , black) and avapritinib+MK-1775 combination (**p = 0.002, green) compared with vehicle group (blue) at day 11.…”

“…Spheroids were treated with appropriate drug(s) and were imaged at 4× magnification by EVOS FL Digital Inverted Microscope after 120 hours of treatment. Spheroid surface area and viability were measured and statistical analyses were conducted as described previously(47). Three independent biological replicate experiments were performed with minimum of three technical replicates in each treatment arm.BrdU incorporation assayDNA synthesis proliferation rate was measured using BrdU Flow kit (BD Biosciences, San Jose, CA) according to manufacturer's protocol.…”

Evolutionary scalpels for dissecting tumor ecosystems

“…In both three-dimensional culture and xenografts of GIST cells, combination therapy manages to control tumor growth and improve survival beyond what was achieved by either drug alone 70 . This work built on previous studies showing efficacy of imatinib when combined with one of several PI3K/AKT inhibitors, in xenografted tumors.…”