In Situ Hydrogel Modulates cDC1‐Based Antigen Presentation and Cancer Stemness to Enhance Cancer Vaccine Efficiency

Effective presentation of antigens by dendritic cells (DC) is essential for achieving a robust cytotoxic T lymphocytes (CTLs) response, in which cDC1 is the key DC subtype for high‐performance activation of CTLs. However, low cDC1 proportion, complex process, and high cost severely hindered cDC1 generation and application. Herein, the study proposes an in situ cDC1 recruitment and activation strategy with simultaneous inhibiting cancer stemness for inducing robust CTL responses and enhancing the anti‐tumor effect. Fms‐like tyrosine kinase 3 ligand (FLT3L), Poly I:C, and Nap‐CUM (NCUM), playing the role of cDC1 recruitment, cDC1 activation, inducing antigen release and decreasing tumor cell stemness, respectively, are co‐encapsulated in an in situ hydrogel vaccine (FP/NCUM‐Gel). FP/NCUM‐Gel is gelated in situ after intra‐tumoral injection. With the near‐infrared irradiation, tumor cell immunogenic cell death occurred, tumor antigens and immunogenic signals are released in situ. cDC1 is recruited to tumor tissue and activated for antigen cross‐presentation, followed by migrating to lymph nodes and activating CTLs. Furthermore, tumor cell stemness are inhibited by napabucasin, which can help CTLs to achieve comprehensive tumor killing. Collectively, the proposed strategy of cDC1 in situ recruitment and activation combined with stemness inhibition provides great immune response and anti‐tumor potential, providing new ideas for clinical tumor vaccine design. An in situ hydrogel vaccine is fabricated by co‐encapsulating Fms‐like tyrosine kinase 3 ligand (FLT3L), Poly I:C, and Nap‐Ce6/UCM (NCUM). Ce6 triggered Photodynamic therapy (PDT) induces tumor antigens release in situ. cDC1 is recruited to tumor tissue and activated for cross‐presentation, followed by migrating to lymph nodes and activating CTLs. Tumor stemness is inhibited by napabucasin, which helps CTLs to achieve comprehensive tumor killing.