Introduction/Purpose:
Pancreatic cancer (PaC) remains one of the most lethal malignancies, with a 5-year survival rate of approximately 10%. The tumour microenvironment (TME) is integral to PaC progression, particularly via exosome-mediated communication. This study investigated the metastasis suppressor NDRG1 and its role in regulating exosome biogenesis, cargo packaging, and uptake in both PaC cells and pancreatic stellate cells (PSCs ). Under the influence of cancer, PSCs can transition into cancer-associated fibroblasts (CAFs), a key contributor to tumour metastasis and immune suppression in the TME of PaC . This study aims to uncover the underling mechanism for which NDRG1 can disrupt the oncogenic cross-talk within the TME of PDAC.
Materials & Methods:
Exosomes were isolated from the conditioned media of PaC cells and PSCs using gradient ultracentrifugation. Their size distribution and concentration were characterized by nanoparticle tracking analysis, and peptide cargo determined using quantitative proteomics. The influence of NDRG1 on the expression, localization and degradation of vesicular trafficking proteins including the ESCRT and RAB families, was also examined. . In addition, we assessed the effect of exosomes from NDRG1-overexpressing PaC cells on PSC signalling and function. The uptake of labelled PSC-derived exosomes by PaC cells was also investigated, with live cell confocal imaging used to determine how NDRG1 affects the intracellular fate of exogenous exosomes.
Results:
Elevated NDRG1 in PaC cells disrupted exosome biogenesis and release, resulting in decreased exosome production and altered protein expression. This was mediated by a direct interaction between NDRG1 and ALIX, which led to ALIX proteasomal degradation. Exosomes from NDRG1-overexpressing cells had significantly fewer CAF-activation proteins (i.e. TGF-β), leading to attenuated ERK1/2 and p38 activation in PSCs, and reduced expression of key fibrotic markers (αSMA, FAP, and collagen 1A). In PaC cells, NDRG1 also impaired the uptake of exogenous exosomes, and redirected them into lysosomes for degradation.
Conclusions:
These findings reveal a novel mechanism by which NDRG1 modulates the TME in pancreatic cancer via exosome-mediated pathways. By disrupting oncogenic exosome production, cargo loading, and cellular uptake, NDRG1 represents a promising therapeutic target for combating this highly aggressive malignancy.