INTRODUCTION ROLE IN CELL LINE CHARACTERIZATION CAUSES OF TRANSFORMATION METHODS OF TRANSFECTION CHARACTERISTICS OF TRAANSFORMED CELLS GENETIC INSTABILITY IMMORTALIZATION ABRERANT GROWTH CONTROL TUMORIGENECITY CHROMOSOMAL ABERATION APPLICATION CONCLUSION REFERENCE

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CELL TRANSFORMATION
By
KAUSHAL KUMAR SAHU
Assistant Professor (Ad Hoc)
Department of Biotechnology
Govt. Digvijay Autonomous P. G. College
Raj-Nandgaon ( C. G. )

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SYNOPSIS
CELL TRANSFORMATION 02
INTRODUCTION
ROLE IN CELL LINE CHARACTERIZATION
CAUSES OF TRANSFORMATION
METHODS OF TRANSFECTION

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CELL TRANSFORMATION 02
CHARACTERISTICS OF TRAANSFORMED CELLS
GENETIC INSTABILITY
IMMORTALIZATION
ABRERANT GROWTH CONTROL
TUMORIGENECITY
CHROMOSOMAL ABERATION
APPLICATION
CONCLUSION
REFERENCE

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INTRODUCTION
Transformation of cultured cells implies a spontaneous or induced
permanent phenotypic change resulting from a heritable change in
DNA and gene expression.

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Transformation is associated with genetic instability and three
major classes of phenotypic change:
immortalization, the acquisition of an infinite life span.
Malignancy
aberrant growth control, the loss of contact inhibition of cell
motility, density limitation of cell proliferation, and anchorage
dependence,

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It is important that transformation characteristics be included
when a cell line is validated to determine whether it originates from
neoplastic cells or has undergone transformation in culture.
The transformation status must be known when culturing cells
from tumours, in order to confirm that the cells are derived from the
neoplastic component of the tumour, rather than from normal
equivalent cells, infiltrating fibroblasts, blood vessel cells, or
inflammatory cells.
ROLE IN CELL LINE CHARACTERIZATION

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CAUSES OF TRANSFORMATION
Spontaneous
Infection with transforming virus
From gene transfection
Exposure to ionizing radiations.

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METHODS OF TRANSFECTION

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CHARACTERISTICS OF TRANSFORMED CELLS

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GENETIC INSTABILITY
The characteristics of a cell line do not always remain stable. In
addition to the phenotypic alterations , cell lines are prone to genetic
instability.
Normal human finite cell lines are usually genetically stable, but
cell lines from other species, particularly the mouse, are genetically
unstable and transform quite readily.

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CHROMOSOMAL ABERRATION
Evidence of genetic rearrangement can be seen in chromosome
counts and karyotype analysis.
Although the mouse karyotype is made up exclusively of small
telocentric chromosomes, several metacentrics arise in many
continuous murine cell lines due to Robertsonian fusion of the
telomeres.

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IMMORTALIZATION
The acquisition of an infinite life span by a cell is referred to as
immortalization.
Most normal cells have a finite life span of 20 to 100 generations ,
but some cells, notably those from rodents and from most tumours,
have indefinite life span, as they go on producing continuous cell line.

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CONTROL OF SENECENCE
The finite life span of cultured cell is regulated by about 10
senescence genes. These dominantly acting genes synthesize product
which inhibit the cell cycle progression.
It is strongly believed that immortalization occurs due to
inactivation of the some of the cell cycle regulatory genes eg. Rb, p53
genes.

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IMMORTALIZATION WITH VIRAL GENE
A number of viral genes have been used to immortalize cells . It
has been recognized for some time that SV40 can be used to
immortalize cells, and the gene responsible for this appears to be the
large T (LT) gene .
Other viral genes that have been used to immortalize cells are
adenovirus E1a, human papilloma virus (HPV) E6 and E7 etc.

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TELOMERASE INDUCED IMMORTALIZATION
The most important causes of finite life span of cells (i.e.
Senescence) is due to telomeric shortening, followed by cell
death (apoptosis).
If the cells are transfected with telomerase gene htrt, the
life span of cells can be extended. And a small population of
these cell become immortal.

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ANCHORAGE INDEPENDENCE
There occur several changes on the cell surfaces of transformed cells.
These include alteration in the cell surface glycoprotein and integrins,
and loss of fibronectin. Some of the transformed cell may totally lack
cell adhesion molecules (CAMs)surface of transformed .
The modification on the surface of transformed cells leads to
decrease in cell -cell and cell substrate adhesion. The net result is that
there is a reduced requirement for attachment and spreading of the
cells to proliferate.

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CONTACT INHIBITION
The transformed cells are characterized by loss of contact
inhibition .This can be observed by the morphological changes
in the disorientad and disorganized monolayer cells.
This result in a reduced density limitation of growth,
consequently leading to higher saturation density compared to
normal cell.

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SERUM DEPENDENCE
Transformed cells have a lower serum dependence than their
normal counterparts due to , in part, to the secretion of growth
factors by tumor cells . These factors have been collectively
described as autocrine growth factors.

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ONCOGENES
Autonomous growth control is also achieved in
transformed cells by oncogenes.
And the modified G protein, such as mutant ras, or by the
overexpression of genes regulating stages in signal
transduction (e.g., src kinase).

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TUMORIGENICITY
Cell transformation is a complex process that often result in
the formation of neoplastic cells .The cell line obtained from
malignant tumor are already transformed. Such cells may
undergo further transformation in vitro culture due to
Increased growth rate
Immortalization
Reduced anchored dependence

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APPLICATION
Cell line preservation:
Animal cell culture and maintenance require expertise and experience. These
cell lines cannot be maintained for a long time, in some cases fresh batch of cell
cultures have to be initiated and some has to be transferred to fresh media for
some period of time . Some of the cell lines are genetically transformed. One
has to use all his ingenuity to keep them intact and functional.
Study of Genotype and Phenotype:
The study of transformation has implications for cell line characterization,
helps to identify genotypic and phenotypic changes relating to cancer, and
provides technology which can be used to immortalize cell lines

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The transformation of animal cells with foreign genetic material
offers an important mechanism for advancing knowledge about
the structure and function of animal genomes, as well as for the
generation of animals with new traits.

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References
1. CULTURE OF ANIMAL CELLS 5TH EDITION : BY R. IAN
FRESHNEY
2. BIOTECHNOLOGY BY U. STAYANARAYAN.