HURP Silencing Differentially Impacts Spindle Architecture and Metastatic Behavior in Breast Cancer Cell Lines

Chromosomal instability (CIN) arising from mitotic errors is a hallmark of cancer progression. Hepatoma Upregulated Protein (HURP), a microtubule-associated protein essential for spindle assembly, is frequently overexpressed in aggressive cancers. Here, we investigated HURP's role in breast cancer progression using a cell line model of increasing metastatic potential: immortalized MCF10A, low-metastatic T47D, and highly metastatic MDA-MB-231 cells. Elevated HURP expression was observed in cancer cells, with MDA-MB-231 showing the highest levels. Paradoxically, spindle-bound HURP was reduced in MDA-MB-231 cells despite increased total protein, suggesting cytoplasmic mislocalization. HURP silencing induced cell line-specific effects: moderate spindle defects in MCF10A and T47D cells, but severe abnormalities, apoptosis, and G2/M arrest in MDA-MB-231 cells. Mechanistically, HURP depletion perturbed spindle-bound NuMA, TPX2, and Aurora-A levels, implicating HURP in mitotic regulation and metastatic behavior. HURP silencing also impaired collective migration and converted MDA-MB-231 cells from super-diffusive to sub-diffusive motility, while having minimal effects on less aggressive cell lines. These findings establish HURP as a multifunctional regulator coordinating mitotic fidelity, migration plasticity, and tissue architecture in breast cancer, with pronounced effects in highly metastatic cells, positioning it as a promising therapeutic target for aggressive breast cancers.