CHARACTERISTICS OF CANCER CELLS:
A) MORPHOLOGICAL CHARACTERS:
Study of cancer cells under the Electron Microscope reveals many fine structural abnormalities of the cellular organelles. A tumour or cancerous growth consists of undifferentiated cells which grow and disorganize the tissue in which it occurs. Electron microscopy of cancer tissues and cancer cells has visualized many fine structural variations or abnormalities of cellular organelles.
1) Nucleus:
The nuclei of the cancer cells are usually enlarged with irregularly distributed chromatin. The nuclear membrane is pushed into deep infoldings (blebs) containing cytoplasmic material. The nucleus of cancer cells may also contain proteins, glycogen, lipids and viruses.
The nucleolus of cancer cells display hypertrophy. It becomes more irregular and enlarged. The shape of nucleolus is more irregular than in normal cells and quite frequently several nucleoli present within ones nucleus.
2) Cytoplasm :
In the cytoplasm of a cancer cell following alterations have been frequently observed:
A) Ribosomes and Ergastoplasm:
Ribosomes are more abundant in cancer cells. Formation of polysomes is more frequent. This is associated with the increase in protein synthesis necessary for the rapid growth and proliferation of cancer cells. Usually the cytoplasm of cancer cells is filled with ergastoplasm and ribosomes.
B) Golgi complex:
The Golgi complex of a cancer cell of an exocrine gland (e.g. pancreas, thyroid, etc.) has been found considerably developed. They also increase in number since more enzymes are for the hyperactive cancer cells. But as a rule the cancer cells have a poorly developed Golgi complex.
C) Mitochondria:
Among all the fine structural changes in tumour cells, mitochondrial alterations are the most frequent and striking once. Mitochondria of cancer cells are often swollen (due to over activity) and lack various structural details.
D) Disorganized cytoskeleton:
The cytoskeleton gets depolymerized due to which the cancer cells become independent and their movements become uncoordinated.
E) Other cytoplasmic organelles:
Annulate lamellae and paired cisternae are more frequently found in cancer cells.
F) Pathological cytoplasmic inclusions:
The cytoplasm of cancer cells from different regions is found to contain different types of inclusions. For e.g., milk is found in mammary tumor-cells, colloidal substance in thyroid cancer, etc.
Many cancer cells have phagocytic activity. Cell debris of all kinds may be found in the cytoplasm in various stages of disintegration and digestion. Certain cancer cells have many lysosomes.
3) Plasma membrane:
Usually the plasma membrane remains unchanged except that the intercellular connections may increase in number in cancerous epithelial cells. Intercellular connections may be normal or desmosomes may be more numerous in keratinizing epitheliomas. The cancer cells show no intercellular coupling and they fail to communicate with normal cells.
4) Anaplasia:
In the rapidly growing tumours, a very low degree of differentiation of cancer cells occurs. This is known as anaplasia. Malignant tissues gradually lose the architecture of the normal homologous tissue. On cellular level the fine structure of cytoplasm is much less organized.
5) In cancer cells, the mitotic rate is not inhibited and in cultures the cells tend to pile up, forming irregular masses several layers deep. These cells show less adhesion to the solid support or among themselves and motility is more pronounced.
