DDDR-07. FUNCTIONAL GENOMICS<i>IN VIVO</i> USING CRISPR/CAS9 IDENTIFIES POTENTIAL METABOLIC VULNERABILITIES WITHIN MELANOMA BRAIN METASTASIS

Abstract BACKGROUND Inhibition of the oxidative phosphorylation (OxPhos) pathway in mice suppressed the growth of melanoma brain metastasis but not extracranial or primary skin melanoma. This indicates that melanoma brain metastasis may have targetable metabolic vulnerabilities. Human clinical trials, however showed toxicities following OxPhos pathway inhibition. This suggests that more selective metabolic targets are needed to minimize off target effects. METHODS We designed a focused CRISPR guide RNA (gRNA) lentiviral knockout library targeting 106 metabolism genes significantly enriched in human melanoma brain metastasis (n=88) relative to extracranial (n=50) or primary skin melanoma (n=52). We infected mouse B16F10 melanoma cell lines with the CRISPR library and implanted 1X106 cells subcutaneously or intracerebrally into male (n=3) and female (n=3) C57/Bl6 mice. DNA from cell lines and tumor samples were sent for next generation sequencing. Candidate metabolism genes that may drive growth of melanoma lesion within the brain were identified based on loss of gRNA copies in brain relative to skin. RESULTS The CRISPR/Cas9 in vivo screen identified metabolic genes whose knockout resulted in loss of gRNA clones within established B16F10 melanoma brain lesions relative to skin lesions. These putative metabolism targets included specific components in the oxidative phosphorylation pathway, choline metabolism, and ubiquitin cascade activation. CONCLUSION Using a focused CRISPR/Cas9 in vivo screen, we uncovered potential metabolic targets within established mouse melanoma brain lesions. vWe are currently performing the in vivo screen in melanoma mouse models with spontaneous brain metastasis. Top 3 hits across all models will be validated individually prior to a compound screen for inhibitors.