Non-Invasive Molecular-Genetic Imaging.

Juri G. Gelovani, MD, PhD.  MD Anderson Cancer Center, Houston, TX.

Molecular-genetic imaging can be defined as the non-invasive visualization of normal, as well as abnormal, cellular processes at molecular–genetic, signal transduction and metabolic levels. Molecular imaging is deeply rooted in chemistry, molecular and cellular biology, genetics, as well as different imaging technologies. Such ‘cross-fertilization’ of various disciplines has generated a strong driving force for rapid advances in this new and exciting field. Novel molecular-genetic and cellular imaging methods add both spatial and temporal dimensions to the established molecular–biological in situ assays. Versatile and sensitive non-invasive imaging assays that do not require tissue biopsies are becoming extremely important for monitoring different molecular–genetic, signalling and metabolic processes involved in oncogenesis, progression, and maintenance of cancer. Such imaging assays require a multitude of novel target-specific imaging probes labelled with various radionuclides for gamma camera and PET imaging, different magnetic labels for MR imaging, or fluorescent tags for minimally invasive confocal endo-microscopic imaging. Several molecular imaging probes are being developed to assess the level of expression and activity of specific signalling proteins involved in various oncogenic pathways. These probes will allow for imaging-based pre-selection of patients that may have a better response to a particular target-specific drug. Repetitive imaging during the course of therapy will provide unique information about the dynamics of target activity and help to optimize and individualize therapy. Already, several molecular imaging methods have been developed for monitoring tumor targeted gene therapies using cell specific, replication-conditional and drug-controlled expression systems. Also, molecular imaging is being rapidly becoming an integral part of different cancer immunotherapies and adoptive cell therapies. It is conceivable, that in combination with novel genomic and proteinomic biomarkers for cancer screening, non-invasive molecular imaging could help early cancer detection and monitoring of anti-cancer therapies by pin-pointing the location of various genetic, signal transduction, and biochemical abnormalities that lead to malignant transformation and preferential survival of malignanices.