Quantitative Proteomic Profiling Identifies a Potential Novel Chaperone Marker in Resistant Breast Cancer.

Area of Science:

• Oncology
• Proteomics
• Molecular Biology

Background:

• Aromatase inhibitor resistance is a significant clinical challenge in postmenopausal breast cancer.
• Breast cancer progression involves increased growth factor signaling, cellular motility, and epithelial-mesenchymal transition (EMT).
• Cancer stem cells (CSCs) are implicated in endocrine resistance and EMT, necessitating investigation into their role.

Purpose of the Study:

• To investigate the contribution of cancer stem cells (CSCs) to the development of aromatase inhibitor resistance.
• To characterize the global proteomic signature of CSC-enriched letrozole-resistant breast cancer cells.
• To identify potential molecular mechanisms underlying endocrine resistance.

Main Methods:

• Global proteomic analysis of three-dimensionally cultured mammospheres from letrozole-resistant (LTLT-Ca) cells compared to adherent counterparts.
• Quantitative assessment of protein abundance ratios to identify significantly altered proteins.
• Protein expression analysis and functional enrichment analyses (Gene Ontology, KEGG pathway).

Main Results:

• Over 1000 proteins were quantified, with 359 significantly altered (173 upregulated, 186 downregulated).
• Midasin, a ribosome maturation chaperone, showed a 35-fold increase and was overexpressed in various breast cancer tissues and cell lines.
• Downregulated proteins were associated with protein synthesis pathways, while increased midasin correlated with decreased relapse-free survival in hormone-independent breast cancer.

Conclusions:

• The study characterized the proteomic signature of CSC-enriched, letrozole-resistant cells, highlighting alterations in protein synthesis.
• Increased midasin expression is linked to endocrine resistance and poorer survival outcomes in hormone-independent breast cancer.
• Midasin may play a crucial role in the development of aromatase inhibitor resistance, presenting a potential therapeutic target.