At its core, cancer is a genetic disease. Unregulated growth, inappropriate growth signals, blunted or absent response to “death” signals—all of these characteristics are regulated by genes. For this reason, the promise of genomics in oncology is huge. The expectation of improved diagnostics, prognostics and therapeutics are shared by patients and oncologists alike.
Gene expression analysis is widely used in human oncology.
In the diagnostic phase of oncology, we certainly understand that an accurate diagnosis is necessary in order to prescribe the optimal therapy. A fantastic paper published in the Proceedings of the National Academy of Sciences (http://www.pnas.org/content/98/26/15149.short) reported that gene profiling was incredibly accurate in determining the type of cancer spanning 14 of the most common cancers. In addition, gene expression analysis showed that undifferentiated cancers based upon histology had gene expression patterns unlike their tissue of origin. The dramatically different gene expression accurately predicts the aggressive, abnormal biologic behavior of these tumors, similar to what most oncologists observe in the clinic.
Gene expression patterns can also aid in the prognostic phase of oncology. Accurate prognostication is important, as it allows the clinician to identify patients who will likely do well or those who will do poorly. In a highly cited paper in Nature (http://www.nature.com/nature/journal/v415/n6871/full/415530a.html) the authors evaluate the gene expression pattern of 117 patients and they were able to conclude that “This gene expression profile will outperform all currently used clinical parameters in predicting disease outcome. Our findings provide a strategy to select patients who would benefit from adjuvant therapy.” The number of genes that need to be evaluated does not have to be large. In one paper (http://www.sciencedirect.com/science/article/pii/S1535610804001412) the authors prove that the ratio of only TWO genes was prognostic in breast cancer patients. As a clinician, the question of “how will MY pet do” is one I hear every day. Wouldn’t it be wonderful to be able to accurately answer these pet owners?
When it comes to the cancer that is most treated in the veterinary world, lymphoma, can gene expression analysis help? The answer is a resounding yes. Diffuse large B-cell lymphoma (DLBCL) is the most common type of lymphoma in dogs and is very similar to DLBCL in humans. Gene expression analysis has proven useful in this disease for BOTH dogs and people (http://cancerres.aacrjournals.org/content/73/16/5029.abstract and http://www.nature.com/nature/journal/v403/n6769/full/403503a0.html). By routinely performing gene expression analysis on the lymphomas that we diagnose in dogs, it is possible, indeed expected, that therapy will be more effective. And at the end of the day, isn’t more effective therapy what we all want?