Know about special characteristics of cancer cells

Cancer cells have special characteristics than the normal cells and you can know what are the special characteristics of the cancer cells below.

The special characteristics of cancer cells are:

  • Uncontrolled proliferation
  • Apoptosis and genesis of a cancer cell
  • Expression of Telomerases
  • Control of tumor related blood vessels
  • Dedifferentiation and loss of function
  • Invasiveness
  • Metastases

Uncontrolled proliferation:

Some of the healthy cells like neurons have a little or no capacity of cell division and proliferation. Some other cells in the bone marrow and epithelium of the gastro intestinal tract divide rapidly and continuously. Some of the cancer cells in the plasma cell tumors multiply slowly and those cells in the Burkitt’s lymphoma divide rapidly. Thus cancer cells shows altered cell division and tissue growth. In this way they can be distinguished from the normal cells.

Changes that lead to uncontrolled proliferation of tumor cells:

  1. Growth factors, receptors and signalling pathways
  2. Cell cycle transducers like cyclins, cyclin dependant kinases (cdks) or the cyclin dependent kinase inhibitors
  3. Apoptotic machinery, which normally dispose abnormal cells
  4. Telomerase expression
  5. Local blood vessels, which result from tumor directed angiogenesis

Malignant transformation of several above components is required for the development of cancer.

Apoptosis and genesis of a cancer cell:

Apoptosis signaling pathways
Apoptosis signaling pathways (Photo credit: AJC1)

Apoptosis means programmed cell death. Genetic mutations in the anti-apoptotic genes are required for the development of cancer. Resistance to apoptosis is a hallmark of the cancer. It is brought about by activation of anti-apoptotic factors or by inactivation of pro-apoptotic factors.

Expression of Telomerases:

Telomerases are the specialized structures which cap the ends of the chromosomes for protecting them from degradation, rearrangement and fusion with other chromosomes. DNA polymerase cannot duplicate easily the last few nucleotides present at the ends of DNA, telomerases prevent the loss of ‘end’ genes. During each round of cell division, a portion of the telomere is eroded and it becomes non-functional eventually. At this point, DNA replication stops and cells become senescent..

Telomerase is an enzyme, whose function is to maintain and stabilize telomeres. The rapidly dividing cells such as stem cells and cells from the bone marrow, the germline and the epithelium of gastro intestinal tract express this enzyme. This enzyme is absent in fully differentiated somatic cells. Most of the late stage malignant tumors express this enzyme, this confers the immortality on the cancer cells.

Control of tumor related blood vessels:

The growth of a solid tumor depends on the development of its own blood supply. Small tumors of size about 1-2mm diameter obtain the nutrients by diffusion mechanism. But for a tumor to expand it has to undergo angiogenesis. The term angiogenesis means the development of new blood vessels and it occur in response to growth factors produced by the developing tumor.

Dedifferentiation and loss of function:

The normal cells of a tissue multiply by division of undifferentiated stem cells and give rise to daughter cells. These daughter cells eventually differentiate to transform into mature cells of a relevant tissue to perform their programmed function. Cancer cells have the characteristics of varying degrees of dedifferentiation. Generally poorly differentiated cancers multiply faster and carry a worse prognosis than well-differentiated cancers.

Invasiveness:

The normal cells develop certain spatial relationship with respect to each other, which are maintained by various tissue specific survival factors preventing apoptosis. Whereas cancer cells secrete enzymes like metalloproteinases, which break down the extracellular matrix and enables them to move around.

Metastases:

Metastases are the secondary tumors that are formed by the cells released from the initial or primary tumors. They reach other sites through blood vessels or lymphatic system or they may be shed into the body cavities.

Metastases are the main cause of mortality and morbidity in most of the cases and constitute a major problem for cancer therapy.

Dislodgement or aberrant migration of normal cells leads to apoptosis due to with drawl of necessary anti-apoptotic factors. Apoptosis means programmed cell death.

Cancer cells which metastasise undergoes a series of genetic changes which alters their response to regulatory factors that control the cellular architecture of normal tissues and enables them to establish themselves ‘extraterritorially’.

Secondary tumors occur more frequently in some tissues than the others.

For e.g. Metastases of mammary cancers are often found in the lungs, brain and bones. This is because the breast cancer cells express the chemokine receptors like CXR4 on their surfaces. The selective accumulation of the cells takes place at this site because the chemokines that recognize these receptors will be expressed in high levels in these tissues and does not express in other tissues like kidney etc.

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