Genome-wide screen identifies cullin-RING ligase machinery required for lenalidomide-dependent CRL4CRBN activity

Target identification and elucidation of the mechanism of action of degraders via functional genomics was initially mostly driven by pooled CRISPR/Cas9 screens with a positive selection readout based on cellular fitness.

“Target identification and elucidation of the mechanism of action of degraders via functional genomics was initially mostly driven by pooled CRISPR/Cas9 screens with a positive selection readout based on cellular fitness (“drug resistance screens”).168,232,233”

Most emerging mutations occur directly in the SR of the involved E3 ligase.

“In line with previous studies that employed CRISPR/Cas9 screens13–15, we show that most emerging mutations occur directly in the SR of the involved E3 ligase.”

Several functional genomics campaigns have helped map how the repertoire of CRLs and their regulators shape degrader efficacy, outlining putative resistance mechanisms.

“Several functional genomics campaigns in recent years have helped map how the repertoire of CLRs and their regulators shape degrader efficacy, thus also outlining putative resistance mechanisms.141-151”

A number of COP9 signalosome subunits were identified by Sievers et al. as factors affecting lenalidomide efficacy.

“Concordant with our findings, a number of COP9 signalosome subunits were identified by Sievers et al.17, supporting the idea that an appropriate level of CUL4 neddylation is necessary in order for CRL4CRBN to mediate the efficacy of lenalidomide and pomalidomide (Fig. 1d).”

An appropriate level of CUL4 neddylation is necessary for CRL4CRBN to mediate the efficacy of lenalidomide and pomalidomide.

“Concordant with our findings, a number of COP9 signalosome subunits were identified by Sievers et al.17, supporting the idea that an appropriate level of CUL4 neddylation is necessary in order for CRL4CRBN to mediate the efficacy of lenalidomide and pomalidomide (Fig. 1d).”

The two studies identified UBE2D3 and UBE2G1 as E2 ubiquitin-conjugating enzymes specific to CRL4CRBN.

“The two studies also identified UBE2D3 and UBE2G1 as E2 ubiquitin-conjugating enzymes specific to CRL4CRBN.”

Two recent studies independently conducted genome-wide CRISPR knockout screens to identify factors affecting the efficacy of lenalidomide.

“Two recent studies independently conducted genome-wide CRISPR knockout screens to identify factors affecting the efficacy of lenalidomide17,18.”

Mutations in CRBN, including missense mutations in the thalidomide analogue binding domain, are associated with progressive thalidomide analogue exposure and occur in up to a third of patients with pomalidomide-refractory disease.

“Mutations in CRBN, including missense mutations in the thalidomide analogue binding domain, are associated with progressive thalidomide analogue exposure, and ultimately occur in up to a third of patients with pomalidomide-refractory disease146–148 (FIG. 3a).”