BSC 422 Lecture Notes - Lecture 20: Angiogenesis, Collagenase, Metastasis
Development of Cancer Continued
Invasiveness:
One of the most important characteristics of cancer cells is their invasiveness. It
is the ability to invade other tissues. Malignant cells generally secrete proteases
that digest extracellular matrix components, allowing the cancer cells to invade
adjacent normal tissues. For example, secretion of collagenase by the cancer cells
helps to digest and penetrate through basal laminae to invade the underlying
connective tissue.
Cancer cells also secrete growth factors that promote the formation of new blood
vessels. This is known as angiogenesis. Angiogenesis is necessary to support the
growth of tumor beyond the size of about a million cells at which point new blood
vessels are needed to supply oxygen and nutrients to the multiplying tumor cells.
As a result, new outgrowth of the capillaries is formed into the tumor. These
outgrowths of capillaries are also helpful for metastasis of malignant cells.
Therefore, angiogenic stimulation induces the growth of new blood capillaries
which penetrate easily in the tumor tissue and provide the opportunity for the
cancer cells to enter the circulatory system. As a result, metastasis process begins.
Failure to Differentiate:
Another general characteristic of most of the cancer cells is that they fail to
differentiate. This property is closely related with the abnormal proliferation.
Normal cells are fully differentiated. In most fully differentiated cells, cell
division ceases. In case of cancer-cells, normal differentiation program is blocked
at the early stages of differentiation. The relationship between defective
differentiation and rapid proliferation is clearly noted in case of leukemia.
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