A genome-wide CRISPR activation screening identified that OCT4 and SOX2 co-regulate SIA-cIgG expression

Misplaced IgG expression in cancer cells has been implicated in exacerbated malignancy and poor clinical prognosis. Accumulating evidence indicate that a non-conventional sialylation modification is critical for the function of cancer-derived IgG, rendering the name sialylated cancer IgG (SIA-cIgG). However, our knowledge remains rudimentary about the regulatory mechanism that controls the expression and function of SIA-cIgG. To investigate the regulatory mechanisms of SIA-cIgG expression in lung cancer stem cells, we performed a genome-wide CRISPR activation screen in NCI-H520 cells by expressing a lentiviral library of 70,290 CRISPR-activating gRNAs targeting 23,430 genes. We investigated that the stemness-related transcriptional factors OCT4 (Gene name: POU5F1) and SOX2 were both among the top genes enriched in SIA-cIgG high cells, suggesting that OCT4 and SOX2 may serve as key factors promoting SIA-cIgG expression. A genome-wide CRISPR activation sgRNA library was transduced in NCI-H520 cells and screened by FACS sorting of SIA-cIgG high and SIA-cIgG low cells before sequencing to determine sgRNA distribution.