CD24: A Promising Novel Immunotherapy Target for EGFR-Mutant Lung Cancer

In the field of lung cancer treatment, targeted therapies against epidermal growth factor receptor (EGFR) mutations, such as third-generation EGFR tyrosine kinase inhibitors (EGFR-TKIs) like osimertinib, have brought about revolutionary breakthroughs.However, like many precision therapies, drug resistance remains a persistent problem. Although the initial efficacy is significant, tumor cells quickly enter a state of drug tolerance and persistence (DTP), or eventually develop complete resistance, leading to tumor residue and recurrence. This has become a major challenge for clinicians.

The combination of traditional immune checkpoint inhibitors targeting PD-1/PD-L1 with EGFR-TKIs has shown poor efficacy and increased toxicity in clinical trials. Therefore, is there a new immunotherapy target that can synergistically combine with EGFR-TKIs to effectively eliminate these "stubborn cells"?

In a recent paper published in Cancer Communications, researchers discovered that a molecule called CD24 is a potential candidate for enhancing the efficacy of third-generation EGFR-TKIs. The study showed that CD24 is significantly upregulated after EGFR-TKI treatment. It not only helps tumor cell proliferation, but more importantly, it sends a "don't eat me" signal to macrophages in the tumor microenvironment, promoting immune evasion. Knocking out CD24 through genetic means, or using a novel anti-CD24 antibody called ATG-031, significantly reversed this situation, greatly improving the efficacy of osimertinib in various lung cancer mouse models.

To understand why tumor cells enter a drug-tolerant persistent (DTP) state after osimertinib treatment, researchers first started with cell models. They treated EGFR-mutated lung cancer cell lines with osimertinib, simulating different states of drug response, tolerance, and complete resistance.

Using RNA sequencing technology, they screened 11 cell surface/secreted protein-encoding genes that were upregulated in both responsive and resistant cells. Subsequently, they integrated single-cell RNA sequencing data from 29 clinical lung cancer samples and found that CD24 was the "best candidate," exhibiting the highest expression on tumor cells and almost no expression on hematopoietic cells. This suggested that targeting CD24 might have good safety, avoiding damage to normal immune cells.

This finding was quickly validated at the protein level. Whether in short-term drug-treated cells, long-term induced resistant cells, or residual tumor samples from clinical patients after TKI treatment, the expression level of CD24 was significantly higher than in untreated samples. More importantly, clinical data analysis showed that patients with high CD24 expression levels in surgically resected tumors had shorter recurrence-free survival after postoperative adjuvant TKI treatment. This confirms that CD24 is a reactive biomarker after EGFR-TKI treatment, with elevated levels after treatment and the ability to predict patient prognosis.

By combining gene knockout technology, researchers have revealed the mechanism by which CD24 helps tumor cells resist drug treatment. On one hand, CD24 helps tumor cells resist the lethal effects of TKIs. EGFR-TKI treatment suppresses the survival space of tumor cells by inhibiting key survival signaling pathways-the AKT and ERK pathways. Elevated levels of CD24 can maintain low-level activation of these pathways, thereby reducing the sensitivity of tumor cells to TKI treatment.

Another major "crime" of CD24 is mediating immune evasion. It can inhibit the phagocytic function of macrophages by binding to its receptor, Siglec-10, on macrophages. Further immunotherapy experiments used the first monoclonal antibody targeting CD24, ATG-031. Researchers found that this antibody effectively enhanced the phagocytic capacity of macrophages and significantly improved the therapeutic effect of EGFR-TKI by enhancing the immune response.

Figure 1. Knockdown of CD24 or using ATG-031 (anti-CD24 antibody) exhibited in vitro synergy with third-generation EGFR-TKIs by enhancing the phagocytosis of lung cancer cells. (Liang J, et al., 2025)

In mouse experiments using cell line-derived xenograft (CDX) models, spontaneous lung cancer models, and patient-derived xenograft (PDX) models, the combination therapy of osimertinib + ATG-031 showed a stronger anti-tumor effect and survival advantage than monotherapy. However, if macrophages were depleted in the model mice beforehand, this synergistic effect disappeared, proving that its efficacy indeed depends on macrophage-mediated phagocytosis.

Using methods such as DNA affinity precipitation and chromatin immunoprecipitation sequencing, they discovered that EGFR-TKIs activate JNK kinase, leading to phosphorylation of the transcription factor YY1 at the S247 site. This phosphorylation modification promotes YY1 dimerization, allowing it to bind simultaneously to both the promoter and enhancer regions of the CD24 gene, forming a structure called a chromatin loop, which enhances CD24 transcriptional activity. From this signaling axis, targeting YY1 phosphorylation could also be a promising research direction.

This study systematically reveals the crucial role of CD24 in EGFR-mutant lung cancer resistance to targeted therapy, both promoting tumor cell survival and helping them evade immune attack. Currently, ATG-031 has entered early clinical trials, and this robust preclinical study provides strong theoretical support for its application in lung cancer. Future research needs to further validate the predictive value of CD24 as a biomarker and explore its potential applications in the treatment of other targeted therapies (such as ALK or KRAS inhibitors).

Reference

Liang J, Bi G, et al. CD24 is a promising immunotherapeutic target for enhancing efficacy of third‐generation EGFR-TKIs on EGFR-mutated lung cancer. Cancer Communications, 2025.