Co-localization and crosstalk between CD44 and RHAMM depend on hyaluronan presentation.

Area of Science:

• Biochemistry
• Cell Biology
• Cancer Research

Background:

• CD44 and RHAMM are key hyaluronan (HA) receptors often overexpressed in cancers.
• These receptors influence tumor progression, metastasis, and chemoresistance.
• The crosstalk between CD44 and RHAMM, and HA's role in it, is not well understood.

Purpose of the Study:

• To investigate the role of hyaluronan (HA) in the expression, co-localization, and crosstalk of CD44 and RHAMM.
• To determine how different forms of HA (soluble vs. immobilized) affect CD44/RHAMM interactions.
• To elucidate cell-specific feedback mechanisms involving HA and these receptors.

Main Methods:

• Immunocytochemistry
• Förster resonance energy transfer (FRET) microscopy
• Co-immunoprecipitation
• Study of breast cancer cell lines with varying invasiveness and receptor expression
• Comparison of cells with no exogenous HA, soluble HA, and immobilized HA.

Main Results:

• Cellular response to HA depends on its presentation (soluble vs. immobilized).
• CD44/RHAMM complexation was upregulated by immobilized HA but not by soluble HA across all tested cell lines.
• Expression of both CD44 and RHAMM is regulated by HA interactions, suggesting cell-specific feedback loops.

Conclusions:

• Immobilized HA promotes CD44/RHAMM complexation and influences their expression in breast cancer cells.
• HA presentation is critical for regulating the crosstalk and signaling pathways involving CD44 and RHAMM.
• Findings reveal novel insights into HA-mediated regulation of cancer cell signaling.