Background The loss of neurogenic tumor suppressor microRNAs miR-124, miR-128, and miR-137 is associated with glioblastoma’s undifferentiated state. Most of their impact comes via the repression of a network of oncogenic transcription factors. We conducted a high-throughput functional siRNA screen in glioblastoma cells and identify E74 like ETS transcription factor 4 (ELF4) as the leading contributor to oncogenic phenotypes. Methods In vitro and in vivo assays were used to assess ELF4 impact on cancer phenotypes. We characterized ELF4’s mechanism of action via genomic and lipidomic analyses. A MAPK reporter assay verified ELF4’s impact on MAPK signaling, and qRT-PCR and western blotting were used to corroborate ELF4 regulatory role on most relevant target genes. Results ELF4 knockdown resulted in significant proliferation delay and apoptosis in GBM cells and long-term growth delay and morphological changes in glioma stem cells (GSCs). Transcriptomic analyses revealed that ELF4 controls two interlinked pathways: 1) Receptor tyrosine kinase signaling, and 2) Lipid dynamics. ELF4 modulation directly affected Receptor Tyrosine Kinase (RTK) signaling, as mitogen-activated protein kinase (MAPK) activity was dependent upon ELF4 levels. Furthermore, shotgun lipidomics revealed that ELF4 depletion disrupted several phospholipid classes, highlighting ELF4’s importance in lipid homeostasis. Conclusions We found that ELF4 is critical for the GBM cell identity by controlling genes of two dependent pathways: RTK signaling (SRC, PTK2B, TNK2) and lipid dynamics (LRP1, APOE, ABCA7, PLA2G6, and PITPNM2). Our data suggests that targeting these two pathways simultaneously may be therapeutically beneficial to GBM patients.

PurposeThe majority of breast cancers are estrogen receptor (ERα) positive making endocrine therapy a mainstay for these patients. Unfortunately, resistance to endocrine therapy is a common occurrence. Fatty acid synthase (FASN) is a key enzyme in lipid biosynthesis and its expression is commensurate with tumor grade and resistance to numerous therapies. MethodsThe effect of the FASN inhibitor TVB-3166 on ERα expression and cell growth was characterized in tamoxifen resistant cell lines, xenografts, and patient explants. Subcellular localization of ERα was assessed using a combination of immunofluorescence and subcellular fractionations. Palmitoylation and ubiquitination of ERα were assessed by immunoprecipitation. ERα and p-eIF2α protein levels were analyzed by western blotting after treatment with TVB-3166 with or without the addition of palmitate or BAPTA. ResultsTVB-3166 treatment leads to a marked inhibition of proliferation in tamoxifen-resistant cells compared to the parental cells. Additionally, TVB-3166 significantly inhibited tamoxifen-resistant breast tumor growth in mice and decreased proliferation of primary tumor explants compared to untreated controls. FASN inhibition significantly reduced ERα levels most prominently in endocrine resistant cells and altered its subcellular localization. Furthermore, we showed that the reduction of ERα expression upon TVB-3166 treatment is mediated through the induction of endoplasmic reticulum stress. ConclusionOur preclinical data provide evidence that FASN inhibition by TVB-3166 presents a promising therapeutic strategy for treatment of endocrine-resistant breast cancer. Further clinical development of FASN inhibitors for endocrine resistant breast cancer should be considered.

Introduction Leptomeningeal metastases (LM) is a clinical complication that occurs when cancer cells invade the leptomeninges and cerebrospinal fluid of patients with malignant tumors. Once diagnosed, limited treatment options exist, and survival is poor. Rhenium-186 Nanoliposome (186RNL) is a liposomal encapsulated beta emitter with a short path length of 1.8 mm, thereby allowing high specific activity brachytherapy with limited exposure to surrounding tissues. Methods To establish the maximum tolerated dose (MTD) of 186RNL by intraventricular (IT) injection, eight cohorts of Wistar rats (n=3 each) were injected IT with increasing activity of 186RNL at doses of 0 (control), 0.480, 0.800, 1.000, 1.150, and 1.340 mCi. Toxicity was assessed by daily food and water intake, daily weights, and observing for neurological deficits. To assess efficacy, C6-Luc glioma cells were injected IT and 15 days post inoculation the animals were treated with 0.69 mCi of 186RNL. Absorbed doses were assessed with gamma camera imaging at 0h, 24h, and 48h post-treatment. Tumor growth was assessed by luciferase bioluminescence. Results No evidence of adverse 186RNL-related effects was observed in rats through 3 months following administration of up to 1.34 mCi with an absorbed dose of up to 1075 Gy. Hence, the MTD exceeded the doses evaluated in this study. A significant difference in survival between the control and treatment groups (n=8 each) was observed at 2 weeks post treatment, with 50% survival in the control group and 100% survival in the treatment group (p=0.0087). The only significant treatment-related histologic finding among treated rats was slight focal thickening of the leptomeninges, suggesting a mild reactive hypertrophy. Conclusion Intraventricular delivery of 186RNL is well tolerated and improves animal survival at 2 weeks in a rat model of LM.

Purpose: Sacituzumab govitecan has shown efficacy and acceptable tolerability in a multicenter phase I/II clinical trial (NCT01631552) in patients with advanced epithelial cancers. Our study was initiated to determine the bioavailability of Sacituzumab govitecan (SG) in breast brain metastasis and glioblastoma. The goals were to evaluate the extent by which SG can penetrate the blood brain barrier and access tumor tissues by testing free SN-38, SN-38G and total SN-38 concentrations in tumor tissue, serum, and CSF. Patients and methods: Patients diagnosed with brain metastatic breast cancer and recurrent glioblastoma were enrolled in a single-center clinical phase 0 study to receive a single intravenous dose of SG at 10 mg/kg one day before surgical resection. Tumor and corresponding serum were collected during surgery to measure their levels of SN-38 and its metabolites. Following recovery, patients resumed SG treatment at 10 mg/kg on days 1 and 8 of 21-day cycles and were assessed for responses by MRI every third cycle using response assessment in neuro-oncology (RANO) criteria. Total Sn-38 levels were quantified in tumor tissue and corresponding serum from the patients. Trop-2 and carbonic anhydrase IX (CAIX) expression was investigated by IHC. SG activity was tested in a breast cancer intracranial mouse model. Results: An average of 2365 ng/ml in serum and 132 ng/g in tissue of total SN-38 was quantified in our patient samples. Trop-2 expression was observed in 90% of patient tumors. 40% of the samples showed high expression of CAIX. SG significantly inhibited tumor growth in vivo and increased overall survival. 20% of patients in the breast cancer arm of the trial demonstrated a complete response by RANO criteria and the remaining 80% of patients demonstrated a partial response. Ultimately, 80% of the patients in the breast cancer metastasis arm survived. Conclusion: Sacituzumab govitecan is an effective drug that crosses the blood brain barrier to inhibit the growth of metastatic breast cancer to the brain after tumor resection surgery. Citation Format: Pegah Ghamasaee, Henriette Balinda, Andrew Brenner, John Floyd. A Phase 0 Clinical trial of Sacituzumab Govitecan in Patients with Breast Cancer Brain Metastases and Recurrent Glioblastoma [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P1-14-04.