Membrane and Endosome Isolation Defines a New Immune Evasion Pathway in Breast Cancer

A recent study in Cancer Research (10.1158/0008-5472.CAN-25-1223) identifies Tetraspanin 13 (TSPAN13) as a key driver of immune evasion in breast cancer. The researchers show that TSPAN13 reduces surface expression of Major Histocompatibility Complex class I (MHC-I), preventing CD8⁺ T cells from recognizing tumor cells. High TSPAN13 levels correlate with poor T-cell infiltration and worse patient survival, while TSPAN13 deletion restores MHC-I and enhances anti-PD-L1 therapy response.

The decisive evidence came from compartment-specific protein isolation.

Using the spin column-based plasma membrane isolation kit (SM-005, Invent Biotechnologies, Inc.), the team successfully isolated plasma membrane fraction instead of relying on whole-cell lysates - demonstrating that MHC-I loss occurs specifically at the cell surface, not merely at the transcriptional or total protein level.

Further fractionation of endosome-enriched compartments using the endosome fractionation kit (ED-028, Invent Biotechnologies, Inc.)  revealed the mechanism: TSPAN13 promotes internalization of MHC-I and redirects it toward lysosomal degradation rather than recycling. Native membrane preparations also enabled co-immunoprecipitation experiments showing that TSPAN13 recruits the E3 ubiquitin ligase STUB1 to ubiquitinate MHC-I, marking it for degradation.

By separating plasma membrane and endosomal fractions, the researchers mapped a surface-to-lysosome pathway of immune escape. The study highlights that precise membrane and vesicular isolation was essential for transforming an observation of reduced MHC-I into a clearly defined trafficking mechanism—establishing TSPAN13 as a promising target for breast cancer immunotherapy.