Panoply™ Human TNFSF10 Knockdown Stable Cell Line

Cancer cells sustain growth, evade immune surveillance, and resist therapy by circumventing apoptosis. However, the mechanisms by which they evade specific extrinsic death signals remain unclear. Here, researchers discovered that certain epithelial-derived cancers exploit the death receptor ligand Apo2L/TRAIL to inhibit apoptosis while simultaneously acquiring cytotoxic capabilities. By analyzing CRISPR knockout screening data from the Cancer Dependency Map, they identified TRAIL/TNFSF10 as a key member of the tumor necrosis factor superfamily in epithelial-derived malignancies. Both renal cell carcinoma (RCC) and squamous cell carcinoma (SCC) express TRAIL in their malignant and non-malignant tissue components. In RCC, loss of the tumor suppressor gene VHL induces HIF2α-dependent TRAIL transcription, whereas in SCC, amplification of the 3q26 region elevates TRAIL expression levels. Experiments involving partial TRAIL silencing revealed that TRAIL-expressing cells kill TRAIL-deficient cells, whereas complete silencing renders cells sensitive to exogenous TRAIL. Mechanistic studies indicate that endogenous TRAIL inhibits apoptosis by inducing the lysosomal degradation of its cognate death receptors. Collectively, these findings demonstrate that cancer cells can repurpose TRAIL through an unexpected "cloak-and-dagger" mechanism that holds significant therapeutic potential.

Researchers hypothesized that endogenous TRAIL might downregulate DR4/5 levels by reducing DR4/5 mRNA transcription or stability, or by promoting their post-translational degradation. Quantitative RT-qPCR analysis revealed no significant changes in DR4 or DR5 mRNA levels in TRAIL-knockdown 786-O, TUHR4-TKB, and 769-P cells (Figure 1A), suggesting the involvement of post-translational inhibition. To identify the relevant regulatory pathway, researchers treated cells with inhibitors targeting various protein degradation mechanisms, including the proteasome inhibitor bortezomib (Btz), the neddylation inhibitor MLN4924 (NAE1), and the lysosome inhibitor bafilomycin A1 (BafA1). The results showed that only BafA1 caused a significant accumulation of DR4/5 protein levels at the cell surface and intracellularly (Figure 1B, C), a finding observed across multiple cell lines. These results indicate that endogenous TRAIL suppresses DR4/5 protein levels primarily by targeting the receptors for lysosomal degradation.

Figure 1. TRAIL inhibits death receptor signaling by promoting lysosomal degradation of DR4 and DR5. (Canty J, et al., 2026)