RB1 Knockout PC-9 Cell Line

The RB1 Knockout PC-9 Cell Line is a CRISPR/Cas9-edited knockout cell line featuring targeted disruption of the RB1 gene in the human lung adenocarcinoma PC-9 cell background. This loss-of-function model eliminates expression of the retinoblastoma protein (pRb), a critical tumor suppressor that governs cell cycle progression, and provides a defined genetic system for dissecting RB1-dependent pathways in non-small cell lung cancer (NSCLC). Generated through CRISPR/Cas9-mediated gene disruption, the cell line serves as a stable, isogenic tool for studying the consequences of RB1 inactivation in a well-characterized, EGFR-mutant epithelial context.

PC-9 cells were originally derived from a 45-year-old Japanese male with lung adenocarcinoma and carry an activating EGFR exon 19 deletion (delE746-A750), rendering them dependent on EGFR signaling for growth and survival. This genetic background makes PC-9 an extensively used model for EGFR-mutant NSCLC, including studies of kinase inhibitor sensitivity and resistance. The introduction of an RB1 knockout into this EGFR-addicted background creates a compound mutant system that recapitulates a clinically relevant subset of lung tumors where concurrent RB1 loss modulates therapeutic response and disease progression.

The RB1 gene encodes pRb, a transcriptional corepressor that negatively regulates E2F family transcription factors and controls the G1/S cell cycle transition. In its active, hypophosphorylated state, pRb binds E2F1/2/3 in complex with DP1 and represses transcription of S-phase genes such as Cyclin E, Cyclin A, PCNA, DNA polymerases, and CDC25A. Phosphorylation by CDK4/6-Cyclin D and CDK2-Cyclin E complexes, under regulation by p16INK4a (CDKN2A) and mitogenic signals from EGFR and MAPK pathways, inactivates pRb, releasing E2F to promote cell cycle progression. pRb also interacts with chromatin remodelers like BRG1, HDAC1/2, and RbAp48 to silence target loci. Knockout of RB1 ablates this gatekeeper function, leading to constitutive E2F activation, unscheduled S-phase entry, and unchecked proliferation irrespective of upstream growth-inhibitory cues.

In the context of EGFR-mutant lung adenocarcinoma, RB1 loss is increasingly recognized as a mechanism of resistance to EGFR tyrosine kinase inhibitors and as a driver of histological transformation to more aggressive phenotypes. The RB1 Knockout PC-9 Cell Line therefore provides a physiologically relevant platform to explore how pRb deficiency cooperates with oncogenic EGFR signaling to alter cell cycle control, bypass senescence, and promote tumor progression. This model allows dissection of signaling crosstalk between EGFR-driven mitogenic pathways and the RB-E2F axis, and enables investigation of how loss of RB1 rewires cellular networks, including PI3K/AKT and p53 pathways.

Researchers can employ this knockout cell line in a variety of applications such as investigating RB1 tumor suppressor function, mapping cell cycle dysregulation, and performing synthetic lethality screens to identify targets in RB1-deficient cancers. Representative assays include Western blotting for pRb, Cyclin E, and E2F1; RT-qPCR quantitation of E2F target genes; flow cytometric analysis of cell cycle distribution; BrdU incorporation; colony formation assays; and drug sensitivity profiling with CDK4/6 inhibitors or EGFR TKIs. Apoptosis assays and RNA-seq further support mechanistic and transcriptomic studies. For additional technical information or to inquire about this product, please contact Ascent Research.