Diagnostic biomarkers

On the basis of our current knowledge, it is conceivable that K+ channels are viable diagnostic biomarkers and therapeutic targets for human cancers. Nonetheless, it should be emphasized that there is still a long way to go towards obtaining solid proof for this hypothesis. There are many unanswered questions and unsolved problems, and answering these questions will shape the future directions of the research field. Not until the key issues will have been resolved, will the clinical implications of K+ channels in cancer therapy be a reality. 

A few years ago, surface plasmon resonance imaging (SPRi) has been implemented in biomarker discovery (30,31). Ladds et al. employed SPRi for detection of candidate diagnostic biomarkers in cancer in combination with antibody arrays (32). Basically, SPRi is a SPR device coupled with a CCD camera, which obtains a slide image when a polarized light is reflected depending on the interaction on the surface. In fact, it is based on surface plas-mons as SPR however, SPRi can analyze hundreds of samples on a single experiment. 

Briefly, BM can be classified as diagnostic biomarkers, which are molecules that help to discriminate between healthy and one or more pathological states prognostic biomarkers are molecules that follow disease evolution. Predictive biomarkers are defined as the molecules that could provide relevant information to predict response or resistance to therapy they also could be used to monitor the response, as well as, in some cases, as diagnostic and prognostic biomarkers. 

There are several performance specifications that need to be considered in the use of a particular bio-marker. Each depends on the question being addressed. Both diagnostic and prognostic biomarkers are used for patient selection. Diagnostic biomarkers either identify a disease process, specific patient characteristics, or establish the severity and extent of involvement, or disease burden. Prognostic biomarkers help predict which patients will progress most rapidly, respond to a particular therapy, or develop complications. 

Reference J. R. Denery, A. A. K. Nunes, M. S. Hixon, T. J. Dickerson, and K. D. Janda, Metabolomics-based discovery of diagnostic biomarkers for onchocerciases, PLoSNegl. Trap. Dis., 4 e834 (2010). 

Surface-enhanced laser desorption ionization (SELDI) uses so-called protein chips for the detection of peptides and proteins from complex biological fluids such as blood or urine, often for the identification of diagnostic biomarkers for specific carcinomas [156, 157]. These protein chips can contain various media for positive or negative ion exchange or reverse-phase chromatography, as well as specific antibodies or DNA. The functionaUzed surface is immobihzed on a MALDl sample plate for the selective enrichment of constituents of the complex mixture applied, whereas the not bound supernatant is removed by washing. Unfortunately, a large number of unsubstantiated claims for the detection of disease-related biomarkers has discredited this approach, mostly as a result of poor mass spectrometric performance. 

Golden, A. L., Battrell, C. E, Pennell, S., Hoffman, A. S., J. Lai, J. and Stayton, P. S. (2010) Simple fluidic system for purifying and concentrating diagnostic biomarkers using stimuli-responsive antibody conjngates and membranes . Bioconjugate Chemistry, 21,1820-1826. 

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