LRP1B and neoplasm: To further determine whether this observation was linked to the regulated intramembrane proteolysis of LRP1B, the authors performed a soft agar assay with cells transfected with the intracellular domain of LRP1B, and discovered that the intracellular domain of LRP1B per se was able to suppress anchorage-independent growth similar to mLRP1B4 [57], suggesting that LRP1B tumor suppressor activity requires its proteolytic processing.