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Sialic acid - tumor marker

2024/05/23

What’s N-acetylneuraminic Acid?

 

Serum sialic acid (SA), also known as N-acetylneuraminic acid, exists in various tissues of the human body, mainly in the cell membrane. It is an important component of glycoproteins and glycolipids on the eukaryotic cell membrane and participates in various physiological functions of the body.

SA plays a special role in the malignant transformation of cells. Its content is closely related to the proliferation, metastasis, infiltration, reduced cell adhesion, tumor antigenicity and escape from the immune surveillance of host cells of malignant tumor cells. It is a widely effective tumor marker.

The serum SA content is stable during normal metabolism. When normal cells are transformed into malignant tumor cells, the increased synthesis of glycolipids on the cell membrane and the abnormal conversion of glycolipids on the cell membrane and more shedding or secretion into the blood are the main mechanisms leading to the increase of SA content in the serum of tumor patients.

Clinical diagnostic significance of sialic acid

① Used for auxiliary diagnosis of digestive system malignant tumors

Currently, in addition to endoscopy, imaging examination and pathological section examination, the detection of serum tumor markers has also become one of the commonly used clinical detection methods for the diagnosis of digestive system malignant tumors.

② Auxiliary diagnosis of lung cancer

In lung cancer patients, the SA positive rate was 80.4% and the diagnostic accuracy rate was 87.3% (with histological or cytological results as the gold standard). Combined detection of SA and TSGF (tumor-specific growth factor) can increase the lung cancer positive rate to 89.8%.

When the serum concentration of SA and TSGF decreased significantly after tumor resection, the positive rate decreased significantly. Determining the serum SA and TSGF content before and after lung cancer surgery helps to understand the patient's prognosis and has important clinical significance for monitoring the efficacy of surgery.

③ Leukemia auxiliary diagnosis

The SA positive rate of leukemia patients is 70-80%, and it is even higher in acute leukemia.

For patients with leukemia, the improvement of bone marrow images indicates that the clinical symptoms and signs are stable or improved, and the serum SA content has decreased significantly.

For patients with worsening bone marrow images, the serum SA content has increased significantly, indicating worsening of the disease or death.

④ Head and neck tumors

The anatomical morphology of the head and neck is complex, and tumors in many parts are not easy to detect early. Testing sialic acid (SA) can diagnose and monitor some malignant tumors.

The SA content of patients with oral and maxillofacial malignancies is significantly higher than that of normal people and patients with benign tumors, and that of patients with stage III and IV malignancies is higher than that of patients with stage I and II.

Moreover, the SA content decreases and then increases and continues to remain at a high level, indicating the possibility of recurrence and metastasis, and a poor prognosis. If it remains at a normal level, it indicates that the condition is stable and the prognosis is good.

⑤ Type II diabetes

The increase in SA content is because SA is a basic component of the receptor and participates in the signal regulation process after insulin binds to the receptor.

When diabetic patients develop the disease, the decomposition and release of SA in the insulin receptor on the surface of fat cells in the body increases, and the SA content in the circulating blood increases. Therefore, receptor abnormality is an important factor affecting the SA level of diabetic patients.

It has been reported in the literature that the mean serum SA value of diabetic patients is significantly higher than that of the control group. Serum SA detection can be used as a reference indicator for diabetic patients.

⑥ Used for cancer antigen detection

In addition to the above, the clinical application of SA has also been reported in ovarian cancer, cervical cancer, etc. The detection of serum SA combined with CEA, AFP (alpha-fetoprotein), CA125 (cancer antigen 125), CA50 (cancer antigen 50), etc. can further improve the sensitivity and specificity of the detection, and can more accurately diagnose and treat tumors, making up for the missed diagnosis and misdiagnosis of a single measurement.

The positive rate is high in lung cancer, leukemia, intestinal cancer, etc., indicating that SA is closely related to malignant tumors and is a good tumor marker.

⑦ Used for postoperative observation

Serum SA detection is also of certain value for dynamic observation of patients after surgery. After clinical cure by surgical resection, serum SA content can be reduced or even reach the normal range. This shows that serum SA is not only an objective indicator for auxiliary diagnosis of malignant tumors, but also a reliable indicator for monitoring changes in the course of surgical treatment.

Summary

Since serum SA levels do not change with age and gender, their expression varies in different types of malignant tumors, but they are closely related to cell-cell adhesion and aggregation, contact inhibition, cell transformation, metastasis, recurrence and spread of malignant tumors.

Therefore, serum SA can be used to screen for a variety of malignant tumors (especially lung cancer) and is suitable for health screening of a large number of people, so as to achieve early detection, early diagnosis and treatment of tumor patients. Serum SA can also be used as an indicator for observing tumor efficacy, monitoring the growth and decline of tumors, estimating prognosis, and whether they spread, relapse and metastasize.