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A Michigan oncologist recently devised a simple experiment to help treat seven patients with advanced, incurable cancer. The experiment used DNA microarray technology to analyze each patient’s tumors for the expression of genes associated with positive response to anti-cancer drugs. The oncologist, Dr. Eric Lester, M.D., then based his drug treatment plans on the results. Four of seven patients are reported to have had a better outcome than expected [1].

Although every cell in the body contains identical genetic material, the same genes are not active in every cell. Tumor cells are no exception. Cancer refers to any one of a large number of diseases characterized by abnormal cell growth and proliferation. Few of these diseases can be treated in the same way, since the genes responsible for a variety of biological processes — DNA duplication, cellular proliferation, cell death — are different from one tumor to the next.

DNA microarray technology enables scientists to examine how active thousands of genes are at a given time. A DNA microarray (also known as a DNA chip, gene chip or gene array) is a collection of over a million DNA spots called probes – small fragments of DNA – attached at one end to known positions on a solid support such as a glass slide or silicon chip. These probes are used to measure the expression level of over 47,000 gene transcripts, with multiple probes per gene (and in some cases more than one probe set per gene) in order to provide measurement reproducibility within a single experiment.

This technology allows physicians to personalize medication regimens based an individual’s unique gene expression profile, enabling them to choose drugs and dosages most likely to have a positive effect. With personalized medicine, therapeutic options can be chosen based on evidence, rather than instinct.

This report is interesting because oncologists don’t yet base treatment decisions on gene expression profiling. The results demonstrate that a personalized molecular oncology approach, basing chemotherapy on tumor gene expression, has a great deal of promise. Dr. Lester is eager to collaborate with other oncologists to build a database of information about genetic mutations seen in tumors and the drugs that work best against each.

The experimental findings were presented last week in Atlanta, GA. at the American Association for Cancer Research’s second International Conference on Molecular Diagnostics in Cancer Therapeutic Development [2]. Researchers have been using DNA chips for years to study the etiology of disease, but only recently have they been used in a clinical setting as a basis for therapeutic decisions.

References

1. Gene Chip Data Improved Therapy in Some Patients with Incurable Cancer. American Association for Cancer Research. 2007 Sept 19.
2. Molecular Diagnostics in Cancer Therapeutic Development: Maximizing Opportunities for Personalized Treatment. American Association for Cancer Research.