Testing for Cancer Agressiveness

Gene expression assays are panels of markers that can predict the likelihood of cancer recurrence in various populations. Functional tumor cell profiling tests for drug activity against a tumor.

By testing the gene expression markers of a patient, researchers can identify those patients unlikely to benefit from adjuvant chemotherapy from those that would. If the patient needs adjuvant chemotherapy, by testing the patient's live tumor cells, the oncologist can select drugs that have a higher probability of being effective for an individual patient.

Gene expression markers can be calibrated to provide information both about the possibility of recurrence and also chemosensitivity. The problem is dissecting one from the other.

You can identify gene expression patterns which correlate with this. But it can be hard and even impossible to tell what exactly you are measuring: is it intrinsic aggressiveness of the tumor? sensitivity to adriamycin? sensitivity to cyclophosphamide? sensitivity to taxol? You find a gene expression panel which correlates with something, but picking apart the pieces is hard.

You can begin to do this if you combine gene expression studies with functional profiling studies. Use functional profiling assays to find a sample which is sensitive to treatment with a specific drug, and then look at a broad range of candidate genes (sequencing the genes in the tumor cells) to see if any can be identified which correlate with patterns of resistance and sensitivity to that specific drug, as observed in vitro in the functional profiling assay, to see if any recognizable patterns of gene expression emerge.

What effect will the different individual drugs have in combination in different, individual tumors? This is where functional profiling assays will always be able to provide uniquely valuable information. The best thing is to combine these different tests in ways which make the most sense, to improve the efficiency of chemotherapy without changing the drugs currently used in standard practice. It will simply provide an approach to better select a repertoire of available drugs.

Sources:
Human Genome Project Information
Functional Profiling Analysis