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). This evidence concerns the gene FLT3LG and neoplasm.