CD138, a cell surface protein marker, serves as an important tool in medical diagnostics. This protein helps identify specific cell types within the body. Its detection and quantification provide valuable information for understanding various health conditions. CD138 levels are examined in laboratory settings to aid in diagnosis.
What is CD138?
CD138, also known as Syndecan-1, is a type I transmembrane heparan sulfate proteoglycan. It is primarily found on the surface of plasma cells and various epithelial cells.
CD138 plays several roles in healthy tissues, including mediating cell adhesion and cell signaling. It also interacts with components of the extracellular matrix, the network of molecules providing structural and biochemical support to surrounding cells. Through its heparan sulfate chains, CD138 can bind to growth factors and chemokines, influencing processes such as cell proliferation and migration.
CD138 in Disease
CD138 is an important marker for plasma cell disorders. Malignant plasma cells, characteristic of multiple myeloma, frequently show high levels of CD138 expression. This makes CD138 a target for diagnosing and monitoring this blood cancer. It helps distinguish cancerous plasma cells from normal ones in many cases.
While primarily associated with multiple myeloma, CD138 expression can also be altered in other conditions. For example, it is expressed in some lymphomas and carcinomas, with varying levels depending on the tumor type. Changes in CD138 expression have been described in certain inflammatory processes and in conditions like type II diabetes. The protein’s involvement in molecular pathways related to cell proliferation, tumor invasion, and metastasis also highlights its role in carcinogenesis.
Measuring CD138
Detecting and quantifying CD138 involves specialized laboratory techniques. Immunohistochemistry (IHC) is one method, where antibodies designed to bind to CD138 are applied to tissue biopsies, such as bone marrow samples. This technique allows pathologists to visualize the presence and distribution of CD138-positive cells within the tissue.
Another widely used method is flow cytometry (FCM), which analyzes cells suspended in a fluid like blood or bone marrow aspirates. In flow cytometry, cells are labeled with fluorescent antibodies that attach to CD138, then passed through a laser beam. The scattered light and fluorescence signals provide information about the cells’ size, internal complexity, and the amount of CD138 present on their surface. Both IHC and FCM help identify and quantify CD138-positive cells, providing objective data for diagnostic purposes. These methods assess the presence and quantity of plasma cells, including those that may be malignant.
Understanding CD138 Test Results
Interpreting CD138 test results requires careful consideration by a healthcare professional, as they are integrated with other clinical findings. High levels of CD138 expression in bone marrow samples often suggest the presence of multiple myeloma or other plasma cell dyscrasias. For instance, an increase in CD138-negative cells has been observed in patients with relapsed or progressive multiple myeloma compared to newly diagnosed individuals. In some cases, patients with low CD138 expression have shown a worse overall survival.
The results help assess the burden of the disease and monitor how a patient responds to treatment. While CD138 is a common marker, some drug-resistant or hypoxic myeloma cells might express lower levels, suggesting the need for additional markers in certain situations. Therefore, CD138 test outcomes are always evaluated within the broader context of a patient’s medical history, physical examination, and other laboratory and imaging studies to establish an accurate diagnosis and guide treatment.