p21-Positive Senescent Stromal Cells Promote Prostate Cancer Immune Suppression and Progression That Can Be Reversed...

Cellular senescence is a well-established tumor-suppressive cell-cycle arrest program. However, chronic inflammation through the senescence-associated secretory phenotype (SASP) can alternatively drive immune suppression and cancer progression. Using prostate cancer patient samples and murine models, we find p16+ and p21+ senescent cells accumulate throughout malignant progression and associate with immune suppression. Single-cell sequencing revealed that p16 and p21 mark distinct epithelial and stromal senescent populations, with p21+ nontumor cells expressing the highest SASP. p21+ stromal cell removal blocked the SASP to reverse immune suppression and slow tumor growth. Senolytic BCL-xL inhibitor treatment could clear p21+ stromal senescent cells, reactivating antitumor CD8+ T-cell immunity and inhibiting prostate tumor progression in mice. Suppression of BCL-xL or p21 also potentiated anti-PD-1 immune checkpoint blockade (ICB) in preclinical prostate cancer models. Our findings demonstrate that targeting p21+ senescent stromal populations can yield therapeutic benefits in advanced prostate cancer through activating antitumor immunity and enhancing immunotherapy outcomes.

Senescent cells accumulate in the tumor and stroma throughout prostate cancer progression and are associated with immune suppression in patients and mice. Senolytic strategies to clear p21+ senescent stromal cells can prevent prostate cancer progression and reactive cytotoxic T-cell immunity to potentiate anti-PD-1 ICB in advanced disease.