Molecular diagnostics analyzes how these genes and proteins are interacting inside a
cell. The focus is on patterns--gene and protein activity patterns--in different types
of cancerous or precancerous cells. Molecular diagnostics uncovers these sets of
changes and captures this information as expression patterns. Also called
"molecular signatures," these expression patterns are improving the clinicians' ability
to diagnose cancer and to recommend more targeted therapies based on an
individuals molecular signature.
What is the role of gene analysis in molecular diagnostics?
DNA microarrays, sometimes called "gene chips," allow researchers to see the
expression of hundreds or thousands of genes at one time. A DNA microarray is a
thin-sized chip with thousands of single-stranded DNA fragments corresponding to
various genes of interest that have been inserted into "spots" in the microarray.
A single microarray may contain 10,000 or more spots with each spot containing
pieces of DNA from a different gene. A single gene chip can even hold representative
fragments from the entire human genome.
What is the role of protein analysis in molecular diagnostics?
Molecular diagnostics evaluates proteins in a cell, tissue, or organism, including the
shape, function, and patterns of expression. Research seeks to identify proteins
involved when normal cellular pathways support malignant growth. In cancerous
tissue, some of the proteins critical for normal communication are damaged,
inactive, overactive, or missing entirely.
The full set of proteins disrupting cellular communications may vary from one cancer
type to another, and they may also vary somewhat from one patient to another with
that type of cancer.
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| Image courtesy of the National Cancer Institute |
The discovery that there are significantly fewer genes in the human genome than
initially estimated has placed more emphasis on the role of proteins, not genes, in
conferring biocomplexity to an organism. Proteins are generally considered one
step closer to biological function than genes and their analysis provides a more
direct link making proteomics the key to understanding health and disease.
In order for proteomics to be useful in molecular diagnostics, many basic biological
questions remain to be answered beginning with understanding the 'normal' protein
architecture in a cell and then how and why that goes wrong in cancer.
In addition the application of proteomics to molecular diagnostics has two major
hurdles to overcome.
- The first and most formidable is identification and analysis of relevant tumor
markers.
- The second is developing portable, sensitive, accurate instruments that can be
used in the clinic.
