This is an Investigator-initiated, Open-Label Clinical Study of a mRNA Vaccine Encoding Tumor-Specific Circular RNA Antigens in Combination with anti-PD-1 monoclonal antibody in Patients with Advanced Solid Tumors. Preclinical studies of this project have identified that circFAM53B, which is specifically overexpressed in tumor cells, possesses the ability to encode a cryptic peptide, FAM53B-219aa, representing a potential tumor vaccine target. In this study, the sequence encoding the cryptic antigen from circFAM53B will be linearized and formulated as an mRNA vaccine (circFAM53B mRNA injection). The vaccine will be administered via lipid nanoparticle (LNP) encapsulation, and its safety and efficacy will be evaluated in combination with anti-PD-1 monoclonal antibody therapy.