Extrachromosomal circular DNA: a potential clinical therapeutic target in malignant tumors

Malignant tumors, commonly referred to as cancer, are pathological conditions distinguished by the unregulated growth and infiltration of malignant cells into adjacent tissues or remote organs. This uncontrolled cell proliferation results in continuous tumor cell division and proliferation in the body. The tumor invades surrounding tissues and spreads to other body parts through the bloodstream or lymphatic system. This forms distant metastases that can influence several systems and organs, seriously affecting the health and life of patients. Effective treatment methods are still lacking owing to their complex mechanism of action. With the continuous development of precision medicine, research on the correlation between extrachromosomal circular DNA (eccDNA) and malignant tumors has become a hot topic. The eccDNA is a circular DNA molecule independent of chromosomes, more stable, and less susceptible to nuclease degradation. Increasing evidence has shown that eccDNA has a function in malignant tumor heterogeneity, invasiveness, evolution, and chemical resistance. It drives tumor heterogeneity so that cancer cells can quickly adapt to treatment plans and environmental changes. Compared with linear chromosomal DNA, eccDNA has an open structure, carries active histone modifications, and can facilitate long-range gene interactions, significantly improving the transcriptional activity of genes and playing an essential regulatory role in disease progression. It also serves as a biological marker for diagnosing and predicting malignant tumors, thus attracting increasing attention. This article reviews its role, mechanism, and value in malignant tumors, providing a new perspective for diagnosing and treating this disease.