CANCER: immortal cells and their properties

As discussed in the follwing article; 
HOW NORMAL CELL CHANGE INTO CANCER

three steps lead to cancer; immortalization, transformation and metastasis.
This is a lead in the topic with me dealing with immortalization . Here it goes:-

IMMORTALIZATION -

• It is the process of becoming immortal. An immortal cell can indefinitely grow.
• Except for their capability to grow indefinitely,  they are very much similar to normal cells and behave normally, when cultured in vitro. 
• They don't form tumors when introduced in test animals like transformed cells do. 
• Their ability to grow indefinitely makes them very useful in lab because this makes them easy to maintain . They are mostly used for understanding the normal processes and physiology of cells and drug testing.

Scanning electron micrograph of He-La cell

                                                     
Advantages:

• The mutations required for immortality can occur naturally or can be intentionally induced.
• Immortalized cell lines can also be cloned giving rise to a clonal population which can, in turn, be propagated indefinitely. This allows an analysis to be repeated many times on genetically identical cells which is desirable for repeatable scientific experiments.
• Immortalized cell lines find use in biotechnology where they are a cost-effective way of growing cells similar to those found in a multicellular organism in vitro.
• The cells are used for a wide variety of purposes, from testing toxicity of compounds or drugs to production of eukaryotic proteins.

Limitations

• While immortalized cell lines often originate from a well-known tissue type they have undergone significant mutations to become immortal. This can alter the biology of the cell and must be taken into consideration.

Methods for generating immortalized cell lines:

There are several methods for generating immortalized cell lines:

• Isolation from a naturally occurring cancer. This is the original method for generating an immortalized cell line. Major examples include human He-La cells, obtained from a cervical cancer and mouse Raw 264.7 cells, obtained from a murine leukemia.
• Spontaneous or induced random mutagenesis and selection for cells which are able to undergo division.
• Introduction of a viral gene that partially deregulates the cell cycle (e.g., the adenovirus E1 gene was used to immortalize the HEK 293 cell line).
• Artificial expression of key proteins required for immortality, for example telomerase which prevents degradation of chromosome ends during DNA replication in eukaryotes
• Hybridoma technology, specifically used for the generation of immortalized antibody-producing B cell lines, where an antibody-producing B cell is fused with a myeloma (B cell cancer) cell.

Examples of immortalized cell lines
There are several examples of immortalized cell lines, each with different properties.
Most immortalized cell lines are classified by the cell type they originated from or are most similar to biologically.

A549 cells – derived from the tumor of a cancer patient
HeLa cells – an extremely widely used human cell line isolated from a cervical cancer, probably                              derived from epithelial cells
HEK 293 –  derived from aborted human fetal cells and a virus
Jurkat     –   a human T lymphocyte cell line isolated from a case of leukemia
3T3          –   a mouse fibroblast cell line derived from a spontaneous mutation in cultured mouse                                embryo tissue
Vero cells – a monkey cell line
F11 Cells -  a line of neurons from the dorsal root ganglia of rats.


NOTE: An immortalised cell line should not be confused with stem cells, which can also divide indefinitely, because stem cells form a normal part of the development of a multicellular organism. Whereas; immortalized cells are produced as a result of unpleasant mutation . Immortalization is an unfortunate situation and is an intial step towards TRANSFORMATION and then CANCER.


Well this was just a basic step into understanding the process of immortalization. A detailed discussion of the molecular level will be done in the coming articles. you can drop your queries or doubts in the comments; and if you want to discuss about something else. THANK YOU.