Flora McKinney

Nonsmall-cell lung cancer (NSCLC) accounts for more than 80% of lung cancer cases. Epidermal growth factor receptor mutations (EGFRm) occur in 15 and 40% of NSCLC in Western and Asian populations, respectively. Current treatment for advanced NSCLC targets EGFRm with tyrosine kinase inhibitors (TKIs). Osimertinib is a third-generation EGFR-TKI now used as a first-line treatment in advanced/metastatic NSCLC; however, drug resistance frequently develops. Dysregulation of metabolism has been suggested to play a role in the development of drug resistance. Here, we investigated the role of lipid metabolism in the development of osimertinib resistance (OR) using pharmacologically-induced resistant cellular models. We used a multiomics approach, combining lipidomics with proteomics analyses. We found alterations in processes relating to metabolism, such as dysregulated sphingolipid metabolism. In particular, we identified that OR lines reduce free ceramides in favor of complex glycosphingolipids. Mechanistically, this metabolic shift avoids ceramide-mediated apoptosis via caspase-3 activation. Importantly, when we combined osimertinib with D-PDMP, an inhibitor of the key enzyme responsible for the conversion of ceramide to glucosylceramide, we increased the sensitivity to osimertinib. Overall, we have identified the glycosphingolipid metabolic pathway as a potential therapeutic target to reinstate sensitivity to osimertinib in NSCLC.

The combination of PARP and NAMPT inhibitors (PARPi/NAMPTi) has been explored for the treatment of TNBC, Ewing Sarcoma and high grade serous carcinoma (HGSC). However, dose limiting toxicity has hampered NAMPTi in clinical trials. To maximise the therapeutic window, we set out to identify predictive genomic biomarkers. Bioinformatic analysis and screening of a panel of epithelial ovarian cancer (EOC) cell lines revealed that cells with RAS/PI3K pathway mutations were sensitive to the NAMPTi FK866. Activity of olaparib and FK866 was associated with a reduction in nicotinamide mononucleotide (NMN) and the PARP substrate nicotinamide adenine dinucleotide (NAD ⁺ ), with coincident increases in ROS production, DNA damage and apoptosis induction. Caspase 3/7 activity was upregulated to a greater extent in RAS/PI3K mutant cell lines. Finally, the combination significantly reduced omental tumour weight and increased overall survival in mice injected with ID8 Trp53 ^-/- ;Pten ^-/- cells. This study highlights the potential of the PARPi/NAMPTi combination in RAS/PI3K pathway mutant EOC.

Ovarian high-grade serous carcinoma (HGSC) is the most common and lethal subtype of ovarian cancer with limited therapeutic options. In recent years, PARP inhibitors have demonstrated significant clinical benefits, especially in patients with BRCA1/2 mutations. However, acquired drug resistance and relapse is a major challenge. Therapies disrupting the spliceosome alter cancer transcriptomes and have shown potential to improve PARP inhibitor response. Indisulam (E7070) has been identified as a molecular glue that brings splicing factor RBM39 and DCAF15 E3 ubiquitin ligase in close proximity. Exposure to indisulam induces RBM39 proteasomal degradation through DCAF15-mediated polyubiquitination and subsequent RNA splicing defects. In this study, we demonstrate that loss of RBM39 induces splicing errors in DNA damage repair genes in ovarian cancer, leading to increased sensitivity to PARP inhibitors such as olaparib. Indisulam synergized with olaparib in multiple in vitro models of ovarian cancer regardless of PARP inhibitor sensitivity and improved olaparib response in mice bearing PARP inhibitor-resistant tumors. DCAF15 expression, but not BRCA1/2 mutational status, was essential for the synergy between indisulam and olaparib, suggesting that the combination therapy may benefit patients irrespective of their BRCA1/2 status. These findings demonstrate that combining RBM39 degraders and PARP inhibitors is a promising therapeutic approach to improving PARP inhibitor response in ovarian HGSC. Graphical One Sentence Summary: We identified a novel drug combination that may improve PARP inhibitor response and benefit a large group of ovarian cancer patients.

Cancer cells release extracellular vesicles, which are a rich target for biomarker discovery and provide a promising mechanism for liquid biopsy. Size-exclusion chromatography (SEC) is an increasingly popular technique, which has been rediscovered for the purposes of extracellular vesicle (EV) isolation and purification from diverse biofluids. A systematic review was undertaken to identify all papers that described size exclusion as their primary EV isolation method in cancer research. In all, 37 papers were identified and discussed, which showcases the breadth of applications in which EVs can be utilised, from proteomics, to RNA, and through to functionality. A range of different methods are highlighted, with Sepharose-based techniques predominating. EVs isolated using SEC are able to identify cancer cells, highlight active pathways in tumourigenesis, clinically distinguish cohorts, and remain functionally active for further experiments.