Exosome proteomes reveal glycolysis-related enzyme enrichment in primary canine mammary gland tumor compared to metastases.

Objective: Numerous evidence has highlighted the differences between primary tumors and metastases. Nonetheless, the differences in exosomal proteins derived from primary tumor and metastases remain elusive. Here, we aimed to identify differentially expressed exosomal proteins from primary canine mammary gland tumor and metastases to understand how they shape their own tumor microenvironment.

Methods: We clearly distinguished primary canine mammary gland tumors (CHMp) from metastases (CHMm) and profiled the proteins within their secreted exosomes using LC-MS/MS. Moreover, the abundance of glycolysis enzymes (GPI, LDHA) in CHMp exosome was verified with Western blotting, To broaden the scope, we extended to human colorectal cancer-derived exosomes (SW480 vs. SW620) for comparison.

Results: We identified significant differences in 87 and 65 proteins derived from CHMp and CHMm, respectively. Notably, glycolysis enzymes (GPI, LDHA, LDHB, TPI1, and ALDOA) showed specific enrichment in exosomes from the primary tumor.

Conclusion: We observed significant differences in the cellular proteome between primary tumors and metastases, and intriguingly, we identified a parallel heterogeneity the protein composition of exosomes. Specifically, we reported that glycolysis enzymes were significantly enriched in CHMp exosomes compared to CHMm exosomes. We further demonstrated that this quantitative difference in glycolysis enzymes persisted across primary and metastases, extending to human colorectal cancer-derived exosomes (SW480 vs. SW620). Our findings of the specific enrichment of glycolysis enzymes in primary tumor-derived exosomes contribute to a better understanding of tumor microenvironment modulation and heterogeneity between primary tumors and metastases.