WNT8B and WNT9B signaling promote the survival of dormant HGSOC cells through a non-canonical pathway that regulates cancer stem cell phenotypes.

Cancer cell dormancy and the resultant resistance to conventional therapies present significant challenges for the successful treatment of high-grade serous ovarian cancer (HGSOC). We used genome wide and specialized sgRNA libraries in CRISPR-based screens to identify critical features of dormancy and metastasis. Our findings demonstrate that Wnt ligands WNT8B and WNT9B are essential for sustaining cell survival during prolonged dormant spheroid culture conditions. Inhibition of Wnt signaling by WNT8B/9B knock out not only compromised spheroid cell viability, but also negatively affected spheroid formation. These Wnt ligands utilize a non-canonical signaling pathway to activate expression of stem cell genes during spheroid dormancy. Overall design: We constructed a sgRNA library targeting a selected list of 2,740 genes and non-targeting controls. CRISPR screen was conducted in OVCAR8 cells. sgRNA identity and abundance were determined in three replicates for each condition: adherent (ADH), which involved initially infected cells expanded under adherent culture conditions, and spheroid (SPH) cells following 48 hours of suspension culture. Each condition contains data for cells expressing Cas9 (Cas9-positive) and those not expressing Cas9 (Cas9-negative). The sgRNA abundance for the initial plasmid library preparation are also provided in the readcounts table. The CRISPR screen was analyzed using the TRACS software package as described in GSE150246.