When scientists block a cellular cleanup system in liver cancer cells, they see more of two proteins (HNF1α and PCSK9) and less of another (LDL receptor), which suggests that this cleanup system normally keeps these proteins in check—and by messing with it, they can change how the body handles bad cholesterol.

Assessment Explanation

The claim describes a direct mechanistic relationship observed in a controlled in vitro system using specific inhibitors. The use of two distinct proteasome inhibitors (bortezomib and MG132) strengthens internal validity, and the observed changes in protein levels (HNF1α↑, PCSK9↑, LDLR↓) are consistent with a proposed regulatory cascade. The verb 'demonstrating' is appropriate because the experimental design (inhibiting proteasome → measuring protein changes) supports causal inference within the system studied. However, the claim generalizes to 'direct regulation' without ruling out indirect effects (e.g., transcriptional feedback), so 'suggests' or 'indicates' would be more cautious. Still, given the specificity of the inhibitors and the protein-level measurements, 'demonstrating' is acceptable in the context of mechanistic cell biology papers.