68Ga-PFA2 PET Imaging for the Diagnosis of Annexin A2-Positive Tumors

Tumor metastasis and invasion are the leading causes of cancer-related deaths, with over 90% of cancer patients dying from distant metastasis. Tumor cells spread to distant organs through local infiltration, hematogenous metastasis, or lymph node metastasis, complicating treatment and severely affecting the prognosis and survival rate of patients. Therefore, precise and early assessment of tumor invasion and metastasis is crucial for optimizing personalized treatment plans and improving patient survival.

Currently, the detection of tumor metastasis primarily relies on imaging examinations, blood biomarkers, and histopathological analysis. Among these, 18F-FDG PET/CT plays a key role in tumor staging and distant metastasis evaluation. However, its sensitivity is low for certain tumors, such as well-differentiated hepatocellular carcinoma, colorectal cancer, and glioblastoma, and factors like inflammation can lead to false positives. Additionally, serum tumor markers (such as AFP, CEA, and CA19-9) often lack specificity in some patients, and histopathological analysis requires invasive sampling, making real-time monitoring difficult. Therefore, the development of non-invasive methods based on molecular targets for early and precise detection of tumor invasion and metastasis holds significant clinical value.

Tumor invasion and metastasis is a complex process involving multiple molecules that drive cancer cell proliferation, invasion of surrounding tissues, and the formation of secondary tumors in distant organs. During invasion and metastasis, cancer cells are often subjected to mechanical stress, such as compression and shear forces, making the repair of cell membrane damage crucial for the survival of invasive cancer cells. Annexin A2 (ANXA2) is a multifunctional protein that plays a key role in cancer cell membrane repair, proliferation, migration, invasion, and metastasis. Studies have shown that silencing ANXA2 or inhibiting its function with neutralizing antibodies reduces the ability of cancer cells to repair membrane damage, thereby limiting tumor cell dissemination. Abnormal expression of ANXA2 is a common feature in many types of tumors. The expression level of ANXA2 in tumors is closely associated with the growth, invasion, and metastasis of pancreatic cancer, colorectal cancer, breast cancer, gliomas, and other tumors.

Furthermore, ANXA2 promotes tumor cell proliferation by facilitating DNA replication, cell cycle progression, and neovascularization, thereby supporting tumor growth and progression. For instance, in breast cancer, ANXA2 promotes STAT3 activation through Tyr23 phosphorylation, upregulating cyclin D1 and MMP2/9, which accelerates breast cancer proliferation, invasion, and metastasis. In pancreatic cancer, ANXA2 regulates the Src/ANXA2/STAT3 signaling pathway to promote epithelial-mesenchymal transition (EMT), enhancing cellular invasiveness. In non-small cell lung cancer (NSCLC), ANXA2 overexpression correlates with tumor staging, lymph node metastasis, and distant metastasis, and can serve as an independent prognostic marker. In hepatocellular carcinoma (HCC), high ANXA2 expression is not only associated with higher tumor recurrence rates but also promotes angiogenesis, further driving tumor progression. In glioblastoma (GBM) and colorectal cancer, ANXA2 has also been shown to accelerate disease progression through mechanisms such as extracellular matrix degradation, angiogenesis, and tumor microenvironment regulation.

ANXA2 not only serves as a poor prognostic factor for various cancers but also holds potential as a therapeutic target. Several monoclonal antibodies targeting ANXA2 have shown significant antitumor and antiangiogenic effects. Rajkumar et al. demonstrated that the monoclonal antibody mAb150, targeting the N-terminal epitope of ANXA2, enhances cancer stem cells' re-entry into the cell cycle, reducing migration and EMT in activated cancer cells, ultimately inhibiting ascites formation and extending survival in a mouse ovarian cancer model. Another monoclonal antibody, ch2448, targets the unique glycan epitope of ANXA2, triggering antibody-dependent cell-mediated cytotoxicity, effectively inhibiting tumor formation and delaying or preventing teratoma development. In addition to large molecular antibodies, the first small-molecule inhibitor of ANXA2 in triple-negative breast cancer, 5α-epoxyalantolactone (5-EAL), has been discovered. 5-EAL selectively binds to the conserved cysteine residue of ANXA2, inhibiting the formation of the ANXA2-S100A10 heterotetramer complex, effectively suppressing TNBC proliferation and metastasis. These findings highlight the enormous diagnostic and therapeutic potential of ANXA2 as a biomarker for malignant cancers.

Given the high expression of ANXA2 in various tumors and