mTOR kinase inhibition disrupts neuregulin 1-ERBB3 autocrine signaling and sensitizes NF2-deficient meningioma cellular models to IGF1R inhibition.

Meningiomas (MNs), arising from the arachnoid/meningeal layer, are nonresponsive to chemotherapies, with ∼50% showing loss of the Neurofibromatosis 2 (NF2) tumor suppressor gene. Previously, we established NF2 loss activates mechanistic target of rapamycin complex 1 (mTORC1) and mechanistic target of rapamycin complex 2 (mTORC2) signaling, leading to clinical trials for NF2 and MN. Recently our omics studies identified activated ephrin (EPH) receptor and Src family kinases upon NF2 loss. Here, we report increased expression of several ligands in NF2-null human arachnoidal cells (ACs) and the MN cell line Ben-Men-1, particularly neuregulin-1/heregulin (NRG1), and confirm increased NRG1 secretion and activation of V-ERB-B avian erythroblastic leukemia viral oncogene homolog 3 (ERBB3) receptor kinase. Conditioned-medium from NF2-null ACs or exogenous NRG1 stimulated ERBB3, EPHA2, and mTORC1/2 signaling, suggesting pathway crosstalk. NF2-null cells treated with an ERBB3-neutralizing antibody partially downregulated mTOR pathway activation but showed no effect on viability. mTORC1/2 inhibitor treatment decreased NRG1 expression and downregulated ERBB3 while re-activating pAkt T308, suggesting a mechanism independent of NRG1-ERBB3 but likely involving activation of another upstream receptor kinase. Transcriptomics after mTORC1/2 inhibition confirmed decreased ERBB3/ERBB4 while revealing increased expression of insulin-like growth factor receptor 1 (IGF1R). Drug treatment co-targeting mTORC1/2 and IGF1R/insulin receptor attenuated pAkt T308 and showed synergistic effects on viability. Our findings indicate potential autocrine signaling where NF2 loss leads to secretion/activation of NRG1-ERBB3 signaling. mTORC1/2 inhibition downregulates NRG1-ERBB3, while upregulating pAkt T308 through an adaptive response involving IGF1R/insulin receptor and co-targeting these pathways may prove effective for treatment of NF2-deficient MN.

CUE-101, a Novel E7-pHLA-IL2-Fc Fusion Protein, Enhances Tumor Antigen-Specific T-Cell Activation for the Treatment of HPV16-Driven Malignancies.

PURPOSE: To assess the potential for CUE-101, a novel therapeutic fusion protein, to selectively activate and expand HPV16 E711-20-specific CD8+ T cells as an off-the shelf therapy for the treatment of HPV16-driven tumors, including head and neck squamous cell carcinoma (HNSCC), cervical, and anal cancers. EXPERIMENTAL DESIGN: CUE-101 is an Fc fusion protein composed of a human leukocyte antigen (HLA) complex, an HPV16 E7 peptide epitope, reduced affinity human IL2 molecules, and an effector attenuated human IgG1 Fc domain. Human E7-specific T cells and human peripheral blood mononuclear cells (PBMC) were tested to demonstrate cellular activity and specificity of CUE-101, whereas in vivo activity of CUE-101 was assessed in HLA-A2 transgenic mice. Antitumor efficacy with a murine surrogate (mCUE-101) was tested in the TC-1 syngeneic tumor model. RESULTS: CUE-101 demonstrates selective binding, activation, and expansion of HPV16 E711-20-specific CD8+ T cells from PBMCs relative to nontarget cells. Intravenous administration of CUE-101 induced selective expansion of HPV16 E711-20-specific CD8+ T cells in HLA-A2 (AAD) transgenic mice, and anticancer efficacy and immunologic memory was demonstrated in TC-1 tumor-bearing mice treated with mCUE-101. Combination therapy with anti-PD-1 checkpoint blockade further enhanced the observed efficacy. CONCLUSIONS: Consistent with its design, CUE-101 demonstrates selective expansion of an HPV16 E711-20-specific population of cytotoxic CD8+ T cells, a favorable safety profile, and in vitro and in vivo evidence supporting its potential for clinical efficacy in an ongoing phase I trial (NCT03978689).

EPH receptor signaling as a novel therapeutic target in NF2-deficient meningioma.

Background: Meningiomas are the most common primary brain tumor in adults, and somatic loss of the neurofibromatosis 2 (NF2) tumor suppressor gene is a frequent genetic event. There is no effective treatment for tumors that recur or continue to grow despite surgery and/or radiation. Therefore, targeted therapies that either delay tumor progression or cause tumor shrinkage are much needed. Our earlier work established mammalian target of rapamycin complex mTORC1/mTORC2 activation in NF2-deficient meningiomas. Methods: High-throughput kinome analyses were performed in NF2-null human arachnoidal and meningioma cell lines to identify functional kinome changes upon NF2 loss. Immunoblotting confirmed the activation of kinases and demonstrated effectiveness of drugs to block the activation. Drugs, singly and in combination, were screened in cells for their growth inhibitory activity. Antitumor drug efficacy was tested in an orthotopic meningioma model. Results: Erythropoietin-producing hepatocellular receptor tyrosine kinases (EPH RTKs), c-KIT, and Src family kinase (SFK) members, which are biological targets of dasatinib, were among the top candidates activated in NF2-null cells. Dasatinib significantly inhibited phospho-EPH receptor A2 (pEPHA2), pEPHB1, c-KIT, and Src/SFK in NF2-null cells, showing no cross-talk with mTORC1/2 signaling. Posttreatment kinome analyses showed minimal adaptive changes. While dasatinib treatment showed some activity, dual mTORC1/2 inhibitor and its combination with dasatinib elicited stronger growth inhibition in meningiomas. Conclusion: Co-targeting mTORC1/2 and EPH RTK/SFK pathways could be a novel effective treatment strategy for NF2-deficient meningiomas.