Spermine enhances oxidative phosphorylation independently of translation in glioblastoma

Glioblastoma (GBM) is the most aggressive and lethal primary malignant brain tumor, with a mean survival of only 15 months, emphasizing the need for novel therapeutic strategies. Polyamines, small positively charged molecules necessary for cell proliferation, are frequently dysregulated in multiple cancer types, including GBM. Despite this, their distinct role in tumorigenesis has not been well characterized. There are three major polyamines: putrescine, spermidine, and spermine. Putrescine is converted into spermidine, which is further converted into spermine. The role of spermidine has been well defined, as it serves as a precursor for eIF5a-deoxyhypusine, which undergoes hypusination to promote translation of growth factors. Spermine Synthase (SMS), the enzyme that catalyzes the conversion of spermidine to spermine, is upregulated in high-grade gliomas. Preliminary data suggests that SMS is necessary for GBM tumor development and growth, supporting the idea that polyamine metabolism can be a targetable vulnerability in GBM. However, the specific role of spermine, the product of SMS, in GBM remains unknown. We hypothesize that spermine has distinct, non-redundant cellular functions in GBM and aim to elucidate its role using a CRISPR-mediated autochthonous mouse model of GBM. In this model, a plasmid encoding Cas9 and guide RNAs targeting the tumor suppressors PTEN, P53, and NF1 along with polyamine-related genes of interest are introduced into mouse embryos via intrauterine electroporation (IUE), leading to GBM tumor development. Utilizing this system, we have found that SMS knockout (KO) significantly inhibits GBM growth in vitro and in vivo . Interestingly, supplementing physiological concentrations of spermine failed to restore cell viability and oxidative phosphorylation (OCR) in SMS KO cells, while wild-type cells exhibited a robust increase in OCR upon spermine supplementation. Further investigation revealed spermine enhances OCR independently of translation, suggesting that it may function through a post-translational modification (PTM) mechanism. Ongoing studies aim to further characterize the role of SMS and spermine in GBM metabolism and tumor growth. These findings suggest that spermine is a critical regulator of GBM development and progression and may offer a novel metabolic target for therapeutic intervention.