Targeting PP2A for cancer therapeutic modulation.

Protein phosphatases play essential roles as negative regulators of kinases and signaling cascades involved in cytoskeletal organization. Protein phosphatase 2A (PP2A) is highly conserved and is the predominant serine/threonine phosphatase in the nervous system, constituting more than 70% of all neuronal phosphatases. PP2A is involved in diverse regulatory functions, including cell cycle progression, apoptosis, and DNA repair. Although PP2A has historically been identified as a tumor suppressor, inhibition of PP2A has paradoxically demonstrated potential as a therapeutic target for various cancers. LB100, a water-soluble, small-molecule competitive inhibitor of PP2A, has shown particular promise as a chemo- and radio-sensitizing agent. Preclinical success has led to a profusion of clinical trials on LB100 adjuvant therapies, including a phase I trial in extensive-stage small-cell lung cancer, a phase I/II trial in myelodysplastic syndrome, a phase II trial in recurrent glioblastoma, and a completed phase I trial assessing the safety of LB100 and docetaxel in various relapsed solid tumors. Herein, we review the development of LB100, the role of PP2A in cancer biology, and recent advances in targeting PP2A inhibition in immunotherapy.

Acute worsening of CADASIL in a patient with COVID-19 infection: illustrative case.

BACKGROUND: Reports of cerebrovascular ischemia and stroke occurring as predominant neurological sequelae of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, which causes coronavirus disease 2019 (COVID-19), are increasingly evident within the literature. While various pathophysiological mechanisms have been postulated, including hypercoagulability, endothelial invasion, and systemic inflammation, discrete mechanisms for viral neurotropism remain unclear and controversial. OBSERVATIONS: The authors present a unique case study of a 64-year-old male with acute COVID-19 infection and acute worsening of previously stable cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), a rare heritable arteriopathy due to mutation in the Notch3 gene, which is critical for vascular development and tone. Delayed cranial neuropathies, brainstem fluid-attenuated inversion recovery signal, and enhancement of olfactory and vagus nerves on magnetic resonance neurography in this patient further support viral neurotropism via cranial nerves in addition to cerebral vasculature. LESSONS: To the authors' knowledge, this is the first case in the literature that not only demonstrates the consequences of COVID-19 infection in a patient with altered cerebrovascular autoregulation such as CADASIL but also highlights the tropism of SARS-CoV-2 for (1) cranial nerves as a mode of entry to the central nervous system and (2) vessels as a cause of cerebrovascular ischemia.

Anti-invasive efficacy and survival benefit of the YAP-TEAD inhibitor verteporfin in preclinical glioblastoma models.

BACKGROUND: Glioblastoma (GBM) remains a largely incurable disease as current therapy fails to target the invasive nature of glioma growth in disease progression and recurrence. Here, we use the FDA-approved drug and small molecule Hippo inhibitor Verteporfin (VP) to target YAP-TEAD activity, known to mediate convergent aspects of tumor invasion/metastasis, and assess the drug's efficacy and survival benefit in GBM models. METHODS: Up to 8 low-passage patient-derived GBM cell lines with distinct genomic drivers, including 3 primary/recurrent pairs, were treated with VP or vehicle (VEH) to assess in vitro effects on proliferation, migration, invasion, YAP-TEAD activity, and transcriptomics. Patient-derived orthotopic xenograft (PDX) models were used to assess VP's brain penetrance and effects on tumor burden and survival. RESULTS: VP treatment disturbed YAP/TAZ-TEAD activity; disrupted transcriptome signatures related to invasion, epithelial-to-mesenchymal, and proneural-to-mesenchymal transition, phenocopying TEAD1-knockout effects; and impaired tumor migration/invasion dynamics across primary and recurrent GBM lines. In an aggressive orthotopic PDX GBM model, short-term VP treatment consistently diminished core and infiltrative tumor burden, which was associated with decreased tumor expression of Ki67, nuclear YAP, TEAD1, and TEAD-associated targets EGFR, CDH2, and ITGB1. Finally, long-term VP treatment appeared nontoxic and conferred survival benefit compared to VEH in 2 PDX models: as monotherapy in primary (de novo) GBM and in combination with Temozolomide chemoradiation in recurrent GBM, where VP treatment associated with increased MGMT methylation. CONCLUSIONS: We demonstrate combined anti-invasive and anti-proliferative efficacy for VP with survival benefit in preclinical GBM models, indicating potential therapeutic value of this already FDA-approved drug if repurposed for GBM patients.