This study reveals the antibody response repertoire of tumor-infiltrating plasma cells in NSCLC patients following PD-1 blockade, providing a novel strategy for developing CAR-T therapies targeting citrullinated proteins, and highlighting the therapeutic potential of B-cell responses within the tumor microenvironment.
Literature Overview
The study, 'Tumor-Infiltrating Plasma Cell Profiling after PD-1 Blockade Reveals Tumor-Specific Antibodies,' published in the journal Cancer Cell, systematically investigates the antibody responses of B cells, particularly plasma cells, within the tumor microenvironment of non-small cell lung cancer (NSCLC) patients following PD-1 blockade therapy. Using single-cell sequencing and recombinant antibody screening, the research team successfully isolated a monoclonal antibody, PC-1, capable of specifically recognizing citrullinated proteins on tumor cell surfaces, and validated its potential for use in CAR-T therapy. This work expands our understanding of humoral immune responses post-PD-1 blockade, suggesting that tumor-infiltrating B cells (TIL-Bs) are not merely participants in the immune response but may also serve as sources of therapeutic antibodies.Background Knowledge
Although PD-1/PD-L1 blockade has significantly improved outcomes for some NSCLC patients, a large proportion still exhibit primary or acquired resistance, primarily due to heterogeneity in the tumor immune microenvironment and immune escape mechanisms. Traditional research has largely focused on T-cell exhaustion and inhibitory signaling, while the role of B cells in antitumor immunity has long been underestimated. Recent evidence indicates that intratumoral tertiary lymphoid structures (TLS) and CD138+ plasma cell infiltration are associated with favorable prognosis, yet it remains unclear whether these B cells produce functional antitumor antibodies. Furthermore, current CAR-T therapies for solid tumors are limited by the lack of specific targets, often leading to on-target, off-tumor toxicity. Thus, identifying truly tumor-selective antigens remains a major bottleneck. This study focuses on leveraging surgical samples from NSCLC patients treated with PD-1 blockade in the TOP1501 clinical trial to systematically analyze the BCR repertoire of TIL-Bs, particularly antibodies derived from plasma cells, aiming to discover naturally occurring, tumor-specific antibodies for developing new targets and tools for CAR-T or antibody-based therapeutics. This strategy directly links clinical treatment responses with humoral immune responses, offering high translational value.
Research Methods and Experiments
The study utilized tumor samples from NSCLC patients in the TOP1501 clinical trial (NCT02818920) who received neoadjuvant pembrolizumab treatment. By integrating multiplex CODEX imaging, single-cell transcriptomics, and BCR sequencing, the researchers systematically analyzed the phenotypes and clonal architectures of TIL-Bs. CD138+ plasma cells were isolated via fluorescence-activated cell sorting, followed by high-throughput BCR sequencing, enabling the construction of 15 recombinant monoclonal antibodies from expanded clones. Using immunofluorescence and mass spectrometry, the antibody PC-1 was identified to specifically bind citrullinated proteins, particularly vimentin. Further validation via HuProt microarray and functional assays confirmed its high-affinity binding to citrullinated vimentin, calreticulin, and p53. To evaluate its therapeutic potential, the team generated CAR-T cells expressing the PC-1 scFv and assessed their cytotoxic activity in multiple NSCLC and ovarian cancer models. Additionally, PAD2-knockout tumor cells were generated to confirm the antigen dependency of PC-1.Key Conclusions and Perspectives
Research Significance and Prospects
This study provides a novel pathway for target discovery in CAR-T therapy for solid tumors—mining natural antibodies directly from patients’ tumor-infiltrating plasma cells. Compared to traditional screening methods, this strategy offers greater clinical relevance, as the resulting antibodies have undergone natural immune selection in humans, potentially reducing toxicity. Moreover, targeting citrullinated proteins represents a new class of tumor-associated antigens widely present across multiple cancers, suggesting that PC-1 or its derived CAR-T may have broad-spectrum potential. Future work may explore developing PC-1 as an ADC or bispecific antibody, or combining it with PD-1 blockade to enhance therapeutic efficacy.
Conclusion
This study systematically characterizes the antibody responses of plasma cells within the tumor microenvironment of NSCLC patients following PD-1 blockade, successfully isolating the therapeutic antibody PC-1 that targets citrullinated proteins. This antibody not only recognizes tumor cells but also binds to tumor-associated myeloid cells, enabling a dual antitumor mechanism. By constructing PC-1 CAR-T cells, the study demonstrates safe and effective antitumor activity in immunocompetent mouse models, independent of MHC presentation and overcoming T-cell exhaustion. These findings redefine the role of TIL-Bs in antitumor immunity—not merely as antigen-presenting cells, but also as sources of therapeutic antibodies. From bench to bedside, this strategy offers a practical pathway for personalized CAR-T or antibody drug development, particularly for solid tumors lacking clear driver mutations. In the future, combining single-cell BCR sequencing with functional screening may enable the establishment of a 'tumor antibody library,' advancing precision immunotherapy into a new era and offering renewed hope for patients with NSCLC and other solid tumors.
