Migrasome-mediated clearance of excess PLK4 defines a targetable vulnerability.

BACKGROUND: Centrosome amplification caused by Polo-like kinase 4 (PLK4) overexpression promotes tumour initiation, yet sustained PLK4 accumulation is detrimental to cancer cell viability. While proteasomal degradation limits PLK4 levels, whether alternative clearance mechanisms exist remains unknown. METHODS: We established inducible PLK4-overexpressing breast cancer cells and employed live-cell imaging, vesicular marker profiling, immunoprecipitation-mass spectrometry, and in vivo patient-derived xenograft models to investigate how cancer cells eliminate excess PLK4. FINDINGS: In this study, we identified a previously unrecognised mechanism in which excess PLK4 is rapidly expelled via migrasomes. The tetraspanin protein TSPAN6 directly binds PLK4 with high affinity and mediates its incorporation into migrasomes for extracellular release. In breast cancer samples, PLK4 expression decreased while TSPAN6 increased during progression. TSPAN6 knockdown blocked PLK4 expulsion, leading to multipolar spindle formation, apoptosis, and suppression of tumour growth and metastasis in vivo. INTERPRETATION: Migrasome-mediated clearance represents a non-proteasomal pathway maintaining centrosome homoeostasis in cancer cells. Targeting TSPAN6 to prevent PLK4 elimination selectively triggers mitotic catastrophe in PLK4-high tumours, highlighting a previously unrecognised therapeutic vulnerability. FUNDING: This work was supported by the National Natural Science Foundation of China (NSFC) (T2225006, T2488301, and 82272948 to ML), Beijing Municipal Natural Science Foundation (Key program Z220011 to ML, 5254051 to TW), NSFC (82371640 to BX, 82403693 to PW), and the "Clinic + X" program of Peking University (to PW).