The chemokine CXCL12 and its receptor CXCR4 are expressed widely in human cancers including ovarian cancer, where they are associated with disease progression at the levels of tumor cell proliferation, invasion, and angiogenesis. Here we used an immunocompetent mouse model of intraperitoneal papillary epithelial ovarian cancer to demonstrate that modulation of the CXCL12/CXCR4 axis in ovarian cancer has multimodal effects on tumor pathogenesis associated with induction of antitumor immunity. siRNA-mediated knockdown of CXCL12 in BR5-1 cells that constitutively express CXCL12 and CXCR4 reduced cell proliferation in vitro and tumor growth in vivo. Similarly, treatment of BR5-1-derived tumors with AMD3100, a selective CXCR4 antagonist, resulted in increased tumor apoptosis and necrosis, reduction in intraperitoneal dissemination, and selective reduction of intratumoral FoxP3+ regulatory T-cells (T-regs). Compared to controls, CXCR4 blockade greatly increased T cell-mediated antitumor immune responses, conferring a significant survival advantage to AMD3100-treated mice. In addition, the selective effect of CXCR4 antagonism on intratumoral T regulatory cells was associated with both higher CXCR4 expression and increased chemotactic responses to CXCL12, a finding that was also confirmed in a melanoma model. Together, our findings reinforce the concept of a critical role for the CXCL12/CXCR4 axis in ovarian cancer pathogenesis, and they offer a definitive preclinical validation of CXCR4 as a therapeutic target in this disease.

While agents that inhibit specific oncogenic kinases have been successful in a subset of cancers, there are currently few treatment options for malignancies that lack a targetable oncogenic driver. Nevertheless, during tumor evolution cancers engage a variety of protective pathways, which may provide alternative actionable dependencies. Here we identify a promising combination therapy that kills NF1-mutant tumors by triggering catastrophic oxidative stress. Specifically, we show that mTOR and HDAC inhibitors kill aggressive nervous system malignancies and shrink tumors in vivo by converging on the TXNIP/thioredoxin anti-oxidant pathway, through cooperative effects on chromatin and transcription. Accordingly, TXNIP triggers cell death by inhibiting thioredoxin and activating Apoptosis Signal-regulating Kinase 1 (ASK1). Moreover, this drug combination also kills NF1-mutant and KRAS-mutant non-small cell lung cancers. Together these studies identify a promising therapeutic combination for several currently untreatable malignancies, and reveal a protective nodal point of convergence between these important epigenetic and oncogenic enzymes.

NF1 encodes a RAS GTPase-Activating Protein. Accordingly, aberrant RAS activation underlies the pathogenesis of NF1-mutant cancers. Nevertheless, it is unclear which RAS pathway components represent optimal therapeutic targets. Here we identify mTORC1 as the key PI3K effector in NF1-mutant nervous system malignancies and conversely show that mTORC2 and AKT are dispensable. However, we find that tumor regression requires sustained inhibition of both mTORC1 and MEK. Transcriptional profiling studies were therefore used to establish a signature of effective mTORC1/MEK inhibition in vivo. We unexpectedly found that the glucose transporter, GLUT1, was potently suppressed but only when both pathways were inhibited. Moreover, unlike VHL and LKB1 mutant cancers, reduction of 18F-FDG uptake required the suppression of both mTORC1 and MEK. Together these studies identify optimal and sub-optimal therapeutic targets in NF1-mutant malignancies and define a non-invasive means of measuring combined mTORC1/MEK inhibition in vivo, which can be readily incorporated into clinical trials.

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<p>PDF file - 58KB</p>

<p>Supplementary Figure S1. MPNSTs are sensitive to combined HDAC and mTOR inhibtion; Supplementary Figure S2. Change in animal weight while on combiniation treatment; Supplementary Figure S3. A) 90-8TL cells were treated with Nexturastat A at concentration indicated, with (black) or without (white) 100nM sapanisertib; Supplementary Figure S4. Combined HDAC and mTOR inhibition increases reactive oxygen species in MPNSTs;Supplementary Figure S5. TXNIP is required for combination induced MPNST cell death;Supplementary Table S1. Differentially expressed gene sets in MPNSTs treated with HDAC and mTOR inhibitors</p>

<p>Supplementary Materials PDF file - 126K, supplementary methods and figure legends</p>

<p>PDF file - 89K</p>