CD44 splice isoform switching determines breast cancer stem cell state

Area of Science:

• Molecular Biology
• Cancer Research
• Genomics

Background:

• Alternative splicing changes are noted in cancer but their functional roles are unclear.
• CD44 is a known cancer stem cell (CSC) marker, but its specific splice isoform functions in breast cancer are not well understood.

Purpose of the Study:

• To investigate the distinct functional roles of CD44 splice isoforms in breast cancer stem cells.
• To elucidate the molecular mechanisms by which CD44 isoforms influence CSC properties and breast cancer phenotypes.

Main Methods:

• Bioinformatic analysis of The Cancer Genome Atlas (TCGA) database for CD44 isoform association with CSC gene signatures.
• Experimental manipulation of CD44 isoform expression and splicing regulators (ESRP1) in breast CSCs.
• Investigation of downstream signaling pathways, including PDGFRβ/Stat3.

Main Results:

• CD44 standard isoform (CD44s) positively correlates with CSC signatures, while variant isoforms (CD44v) show an inverse association.
• CD44s is the predominant isoform in breast CSCs and is essential for maintaining CSC traits.
• Shifting splicing towards CD44s via ESRP1 induction promotes CSC properties.
• CD44s activates the PDGFRβ/Stat3 pathway, contributing to CSC phenotypes.

Conclusions:

• CD44 splice isoforms exhibit opposing functions in breast cancer, with CD44s promoting CSC states.
• Alternative splicing of CD44 provides functional versatility crucial for distinct cancer cell states and overall cancer phenotype.
• Targeting CD44 isoform-specific functions presents a potential therapeutic strategy for breast cancer.