LRP-1 Commands Two Parallel Signalling Mechanisms to Support Constitutive Tumour Cell Motility in the Absence of Blood Supply

Abstract

Tumour cells often face the stress of ischemic (nutrient paucity and hypoxia) environment and must act self-sufficient to migrate toward the nearest blood supply or die. The mechanism that supports the constitutive motility of tumour cells under stress is poorly understood. We and others have previously shown that the low-density lipoprotein receptor-related protein 1 (LRP-1) plays a critical role in tumour cell migration and invasion in vitro and tumour formation in mice. Herein we show that depletion of LRP-1 completely abolishes the self-supported and serum-independent tumour cell motility. More intriguingly, we demonstrate that LRP-1 commands the full tumour cell motility by connecting with two independent cell surface signalling pathways. First, LRP-1 mediates secreted Hsp90 signalling via the "Hsp90 > LRP-1 receptor autocrine loop" for a half of tumour cell motility. Second, LRP1 stabilizes constitutively activated EGFR signalling that contributes the other half of tumour cell motility. Only combined inhibitions of the secreted Hsp90 autocrine and the EGFR signalling reproduces the effect of LRP1 down-regulation on constitutive tumour cell motility. This study reveals a novel mechanism of how tumour cells migrate in the absence of blood support.