Why do some cancer cells spread so easily to nearby tissues?
The answer often involves enzymes that change the cellular environment. Cathepsin B is one such enzyme that has gained the researchers attention. Cathepsin B (CTSB) is a lysosomal cysteine protease responsible for breaking down proteins during cellular turnover. However, this can also lead to cancer. Whenever these enzymes are overproduced, they become highly expressed, and due to this, tumor growth increases. Studies done by researchers show it may support tumor growth, invasion, and metastasis.
That’s why they are investigating how Cathepsin B contributes to tumor biology and disease progression.
What role does Cathepsin B play in cancer research?
Cathepsin B works mainly in lysosomes inside a healthy cell. It works by breaking down proteins into smaller components. The routine process supports cellular recycling and keeps the internal environment stable.
A study conducted by the National Library of Medicine has shown that Cathepsin B is often overexpressed in many tumors. Although this enzyme stays inside the lysosome, whenever the enzyme appears outside the lysosome, it begins interacting with extracellular proteins and signaling molecules. As a result, it causes tumor growth, tissue invasion, and eventually metastasis.
How Does Cathepsin B Help Cancer Cells Spread?
Before the tumors spread, they first cross a physical barrier. That barrier is known as the extracellular matrix (ECM). It helps surround cells while keeping the tissues organized. However, Cathepsin B can disturb the structure.
The enzyme breaks down ECM proteins such as collagen, elastin, and fibronectin. As the matrix breaks down, cancer cells find paths to move through nearby tissues. Wherever CTSB levels increase, this process becomes more active. That is why many aggressive cancers show increased Cathepsin B activity.
What Role Does Cathepsin B Play in Protease Activation?
In cancer research, a single enzyme can sometimes trigger a whole chain of events. Cathepsin B is an important example. In cancer biology, it helps begin proteolytic cascades, where one protease activates another. It also activates enzymes such as matrix metalloproteinases (MMPs) and urokinase-type plasminogen activator (uPA).
Although these proteases act independently, they work together once activated. Their main work is to break down protein into the extracellular matrix. However, this process weakens the structure that holds tissue together. Research shows that Cathepsin B plays an important role in starting and regulating this enzyme network.
Can Cathepsin B Trigger Growth Signals in Cancer Cells?
Tumor cells need strong signaling networks to survive. Interestingly, Cathepsin B can play a role in these pathways. Although it’s mainly a lysosomal enzyme, its activity can extend beyond protein breakdown.
For example, it may activate the PI3K/Akt pathway, which supports cell survival and promotes cell proliferation.
Furthermore, Cathepsin B can also help activate latent TGF-β (a signaling molecule often linked with tumor development). These signals together help cancer cells to avoid apoptosis, the natural process of cell death. As a result, wherever these signals remain active, cancer cells continue to grow and adapt to stressful conditions.
How Does Cathepsin B Support Metastasis and Angiogenesis?
Metastasis happens when cancer cells move from the original tumor to other parts of the body. However, angiogenesis refers to the formation of new blood vessels. These two processes often work together during cancer progression. One important molecule involved in this process is Cathepsin B Protein (CTSB).
It helps cancer cells break through surrounding tissues and migrate to nearby areas. This protein also supports signals that encourage new blood vessels to grow around tumors.
Although it supports tumor growth, it can also make the cancer more aggressive and difficult to manage.
Final Thought
Cells normally use enzymes to maintain balance and recycle proteins. Cathepsin B is one of these enzymes. It usually works inside lysosomes and helps break down proteins during routine cellular processes. However, when its levels increase, the enzyme starts affecting other cellular components. As a result, tumor cells may grow faster and spread more easily to other tissues.