ABSTRACT
BACKGROUND: Recently, we showed that melanoma brain metastases (MBMs) are characterized by increased utilization of the oxidative phosphorylation (OXPHOS) metabolic pathway compared to melanoma extracranial metastases (ECMs). MBM growth was inhibited by a potent direct OXPHOS inhibitor, but observed toxicities support the need to identify alternative therapeutic strategies. Thus, we explored the features associated with OXPHOS to improve our understanding of the pathogenesis and potential therapeutic vulnerabilities of MBMs. METHODS: We applied an OXPHOS gene signature to our cohort of surgically resected MBMs that had undergone RNA-sequencing (RNA-seq) (n = 88). Clustering by curated gene sets identified MBMs with significant enrichment (High-OXPHOS; n = 21) and depletion (Low-OXPHOS; n = 25) of OXPHOS genes. Clinical data, RNA-seq analysis, and immunohistochemistry were utilized to identify significant clinical, molecular, metabolic, and immune associations with OXPHOS in MBMs. Preclinical models were used to further compare melanomas with High- and Low-OXPHOS and for functional validation. RESULTS: High-OXPHOS MBMs were associated with shorter survival from craniotomy compared to Low-OXPHOS MBMs. High-OXPHOS MBMs exhibited an increase in glutamine metabolism, and treatment with the glutaminase inhibitor CB839 improved survival in mice with MAPKi-resistant, High-OXPHOS intracranial xenografts. High-OXPHOS MBMs also exhibited a transcriptional signature of deficient immune activation, which was reversed in B16-F10 intracranial tumors with metformin treatment, an OXPHOS inhibitor. CONCLUSIONS: OXPHOS is associated with distinct clinical, molecular, metabolic, and immune phenotypes in MBMs. These associations suggest rational therapeutic strategies for further testing to improve outcomes in MBM patients.
ABSTRACT
Leptomeningeal disease (LMD) is a devastating category of CNS metastasis with a very poor prognosis and limited treatment options. With maximal aggressive therapy, survival times remain short and, without treatment, prognosis is measured in weeks. Both LMD diagnosis and treatment are challenging topics within neuro-oncology. In this review, we discuss the advances in LMD diagnosis with a focus on the role of circulating tumor DNA (ctDNA) and discuss the role of targeted and immunotherapy in LMD treatment.
ABSTRACT
Extracellular acidity is associated with tumor progression. Elevated glycolysis and acidosis promote the appearance of aggressive malignant cells with enhanced multidrug resistance. Thus, targeting of tumor acidity can open new avenues in diagnosis and treatment of aggressive tumors and targeting metastatic cancers cells within a tumor. pH (low) insertion peptides (pHLIPs) belong to the class of pH-sensitive agents capable of delivering imaging and/or therapeutic agents to cancer cells within tumors. Here, we investigated targeting of highly metastatic 4T1 mammary tumors and spontaneous breast tumors in FVB/N-Tg (MMTV-PyMT)634Mul transgenic mice with three fluorescently labeled pHLIP variants including well-characterized WT-pHLIP and, recently introduced, Var3- and Var7-pHLIPs. The Var3- and Var7-pHLIPs constructs have faster blood clearance than the parent WT-pHLIP. All pHLIPs demonstrated excellent targeting of the above breast tumor models with tumor accumulation increasing over 4 h postinjection. Staining of nonmalignant stromal tissues in transgenic mice was minimal. The pHLIPs distribution in tumors showed colocalization with 2-deoxyglucose and the hypoxia marker, Pimonidazole. The highest degree of colocalization of fluorescent pHLIPs was shown to be with lactate dehydrogenase A, which is related to lactate production and acidification of tumors. In sum, the pHLIP-based targeting of breast cancer presents an opportunity to monitor metabolic changes, and to selectively deliver imaging and therapeutic agents to tumors.
