Radiogenomics: Creating a link between molecular diagnostics and diagnostic imaging
Introduction
With the relatively recent advent of high-throughput biological methods, biomedical research has seen many changes. High-throughput tools are able to provide a global snapshot of cellular physiology, allowing massively parallel assessment of thousands of genes and gene products. Gene expression profiling of various human tissues has led to a better understanding of cellular pathways and various pathological conditions on a biomolecular level. Analysis of different cancerous tissues in relation to samples of normal organ tissue has permitted an enhanced understanding of tumorogenic processes and aided in improved staging and sub-classification of various malignancies. Numerous studies have also shown that gene expression signatures, each comprised of dozens to hundreds of genes, can significantly improve diagnostic classification, prognostication, and prediction of therapeutic response in cancer [1], [2], [3], [4], [5], [6].
However, gene expression profiling is dependent on the surgical procurement of tissue, yielding a host of risks and potential complications, and making it an unrealistic option for every cancer patient. In contrast to genetic profiling studies, radiographic imaging studies are part of routine clinical care. While it is accepted that imaging can provide important anatomical and morphological information, it is not perceived to imply much consequential molecular detail. However, several studies have recently introduced novel methods for correlating unique features of tumor morphology and physiology garnered through non-invasive imaging with specific patterns of gene expression on a genome-wide scale, thereby introducing the field of “radiogenomics” [7], [8], [9]. These researchers propose that specific radiological tumor phenotypes, or “radiophenotypes,” can serve as surrogates for gene expression signatures, informing a non-invasive yet accurate diagnosis of tumor subtype and molecular biology. Further, if imaging traits can be associated with previously determined treatment-response gene-expression patterns, then non-invasive, routine clinical studies can inform the likely response to specific chemotherapeutics and aid in the decision making process towards an optimal form and duration of treatment. Such methods will potentially allow diagnostic imaging to augment or supplant current techniques that utilize surgical biopsy and pathohistologic analysis, and contribute to a shift towards a more fundamental genetic-based and personalized medicine. The following discussion will center on the promise of high-throughput biological techniques and the emerging field of radiogenomics—an emerging technology that has the potential to link high-throughput molecular diagnostics and diagnostic imaging.
Section snippets
High-throughput biology and gene expression profiling of cancer
With the monumental undertaking of the Human Genome Project largely completed, the accessibility of genomic information has over the last decade brought a prodigious transformation to biomedical research. Investigators are now faced with an array of new tools that allow for the simultaneous measurement of thousands of biological molecules. These high-throughput methods (which are in various stages of maturity) include many novel platforms for profiling each fundamental stage in the flow of
Diagnostic imaging as a surrogate for gene expression profiling
Growth in the clinical utility of imaging modalities to non-invasively characterize disease and guide clinical management in parallel with the development of functional genomic tools such as microarrays provides powerful methods for dissecting both the clinical phenotype in vivo and the molecular basis of disease on a genome-wide level. While gene expression profiling can reveal important information related to underlying biology and its relationship to diagnosis, prognosis, and optimal
Conclusion
Over the last decade, high-throughput biological techniques have reshaped the perspective of biomedical research, allowing efficient and rapid assessment of the entire biological and molecular topography of a cell's physiology. These tools have contributed to a better understanding of cellular pathways and the pathophysiology that leads to tumorogenesis. Gene expression profiling of malignant tissue samples has permitted the elucidation of tumor gene expression signatures across a variety of
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