Spontaneous cellular senescence and stress response heterogeneity in human vestibular schwannomas

Vestibular schwannomas (VS) are rare tumors of the eighth cranial nerve. Their complex etiology and not-well defined molecular basis prompted an investigation into cellular senescence as a contributing factor to tumor biology.

Human VS and healthy peripheral nerve (PN) tissue samples, along with primary VS cultures, were analyzed using RNA sequencing (RNA-seq), senescence-associated β-galactosidase (SA-β-GAL) activity assays, RT-qPCR, western blotting, immunofluorescence, and cell viability assays.

RNA-seq revealed differential expression of senescence-related genes in VS compared to normal Schwann cells. SA-β-GAL-positive cells were observed in VS tissues but absent in PN. Primary VS cultures exhibited canonical features of senescence, including elevated SA-β-GAL activity, increased p16 protein levels, and upregulation of senescence-associated secretory phenotype (SASP) markers such as IL8, IL1B, CCL2, and MMP3. The extent of spontaneous senescence varied among VS cultures and correlated with differential sensitivity to bleomycin-induced senescence: cultures with lower baseline SA-β-GAL activity were more responsive to bleomycin. In contrast, cultures with higher spontaneous senescence showed attenuated activation of the p53/p21 pathway and reduced sensitivity. Furthermore, VS cultures with low baseline senescence were susceptible to combined treatment with bleomycin and the senolytic agent navitoclax, which triggered apoptosis via the intrinsic pathway.

Spontaneous cellular senescence in VS is characterized by p16 upregulation and SASP amplification and is associated with impaired p53/p21 signaling and reduced responsiveness to senescence-inducing agents. These findings suggest that the senescent state of VS cells influences their stress response and may inform future strategies aimed at modulating senescence in tumor contexts.