Modified screening of MYC promotor region elements using the CRISPR library in ovarian cancer

Ovarian cancer remains one of the most lethal gynecological malignancies owing to its high recurrence rate and chemotherapeutic resistance. MYC is a well-known proto-oncogene that is frequently amplified in ovarian cancer and has been implicated in drug resistance. Previously, we established a new promoter-reporter system combined with a CRISPR activation library to identify unknown MYC regulators, and M1AP was identified as a novel MYC regulator. However, considering the insufficient explanation for the absence of guide RNA (gRNA) of MYC, this present study explored methods to prevent the gRNA of MYC itself from binding. This study first modified the promoter-reporter vector to improve its quality, then conducted CRISPR screening and analyzed candidate genes as MYC promoter regulators using next-generation sequencing in OVSAHO ovarian cancer cells. Eighty-six genes had ≥ 1000 reads, and Pearson's correlation coefficient analysis was performed on the cBioPortal of the Cancer Genomics database. Fourteen genes were identified as candidate MYC regulators with positive and significant correlations with MYC. Seven genes, including CYP4v2, ASPH, ANP32D, PCED1A, ABI1, FUZ, and HOOK2, demonstrated significantly higher luciferase activity than the control genes. Four genes, including ABI1, PCED1A, HOOK2, and CYP4v2, activated the MYC promoter, which showed over twofold higher activity than the control when overexpressed using a vector. In conclusion, four genes that activate MYC promoters were identified in an ovarian cancer cell line using the CRISPR library system with a modified promoter-reporter tool. These results will prove helpful in the development of novel treatment strategies for ovarian cancer.