Evaluation of Biomarkers

Most of the biomarkers listed in Table 17.1 were identified in studies of pathophysiology and epidemiology that demonstrated an association between the marker and the presence or prognosis of the underlying clinical condition. Once a putative biomarker is identified/ its subsequent evaluation consists of an analysis of its validity, in the traditional sense of precision/ biaS/ and reproducibility/ and of its -predictive utility. 

Further support for using blood pressure as a surrogate endpoint is provided by the concordance of evidence from a number of clinical trials in which blood pressure lowering with low-dose diuretics and P-blockers was shown to reduce the incidence of stroke/ coronary artery disease/ and congestive heart failure in hypertensive patients (19). Of particular interest is a meta-analysis that was conducted to compare the extent of blood pressure reduction achieved in different clinical trials with the maximum benefit that was anticipated on epidemiolgic grounds (Table 17.3) (20). The decrease in stroke incidence anticipated for a 5- to 6-mm Hg average reduction in diastolic blood pressure was fully realized with only 2 to 3 years of antihypertensive therapy. 

TABLE 17.3 Incidence Change Resulting from a 5-6-mm Hg Change in Diastolic Blood Pressure  

However, the reduction in coronary heart disease risk was substantially less than the maximum anticipated benefit/ perhaps reflecting the fact that atherosclerosis is a chronic and largely irreversible process with a multifactorial etiology. 

More recently, it has been shown that hypokalemia and other dose-related adverse metabolic effects of thiazide diuretics increase the risk of sudden death and negate the cardiovascular benefit of blood pressure lowering when high doses these drugs are prescribed (21). Hence, another explanation for the apparent inability of antihypertensive therapy to lower mortality in patients with coronary heart disease is that high thiazide doses were used in many of the trials that were analyzed. As pointed out by Temple (2), this explanation is supported by the results of a trial of antihypertensive therapy in elderly patients with isolated systolic hypertension (22). In this study, only low doses of a thiazide diuretic were prescribed and a 4-mm Hg average decrease in diastolic blood pressure was associated with a 36% reduction in the 

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This section describes the identification and evaluation of biomarkers (Section 26.3.1) and the major types of biomarkers—exposure, effect, and susceptibility (Sections 26.3.2 to 26.3.4) the subdiscipline of genetic susceptibility is discussed in greater detail in Section 26.4. 

Sepulveda, M.S., Johnson, W.E., et al. (2002) An evaluation of biomarkers of reproductive function and potential contaminant effects in Florida largemouth bass (Micropterus salmoides floridanus) sampled from the St. Johns River. Science of the Total Environment, 289(1-3) 133-144. 

Sohn SJ, Kim SY, Kim HS, Chun YJ, Han SY, Kim SH, Moon A (2013) In vitro evaluation of biomarkers far cisplatin-induced nephrotoxicity using HK-2 human kidney epithelial cells. Toxicol Lett 217( 3 ) 235-242.doi 10.1016/j. toxlet.2012.12.015... 

Bacus, J.W., Lagios, M.D., Johnson, K.A. and Browne, D. (2004) Breast cancer chemoprevention phase I evaluation of biomarker modulation by arzoxifene, a... 

Voshol, H., Brendlen, N., Muller, D., Inverardi, B., Augustin, A., Pally, C., Wieczorek, G., Morris, R. E., Raulf, F., and van Oostrum, J. Evaluation of biomarker discovery approaches to detect protein biomarkers of acute renal allograft rejection. J Proteome Res, 4 1192-1199, 2005. 

Huang, J.X., Kaelsin, G., RanaU, M.V., Blaskovich, M.A., Becker, B., Butler, M.S., Little, M.H., Lash, L.H., and Cooper, M.A. (2015) Evaluation of biomarkers for in vitro prediction of drug-induced nephrotoxicity Comparison of HK-2, immortalized human proximal tnbnle epithelial, and primary cnltures of human proximal tubnlar cells. Pharmacol. Res. Perspect., 3, e00148. 

WILD 0 p ANDERSSON 0, o brien n m, WILSON L and WOODS J A (2001) A critical evaluation of the application of biomarkers in epidemiological studies on diet and health. Br JNutr 86 (Suppl 1) S37-S53. 

Leonzio C, Monaci F. 1996. Multiresponse biomarker evaluation of interactions between mettiylmercury and Aroclor 1260 in quad. Ecotoxicology 5 365-376. 

Nielsen JB, Andersen O, Grandjean P. 1994. Evaluation of mercury in hair, blood and muscle as biomarkers for methylmercury exposure in male and female mice. Arch Toxicol 68 317-321. 

Because hexachlorobenzene can interfere with porphyrin metabolism and produce chemical porphyria, the evaluation of the urinary porphyrin pattern has been proposed as an early biomarker of effect (San Martin et al., 1977 Schmid, I960, 1966 Wray et al., 1962). However, apart from an outbreak of chemical porphyria which occurred in Turkey in the 1950s following ingestion of hexachlorobenzene-contaminated food, cases of chemical porphyria among... 

There is a growing need to better characterize the health risk related to occupational and environmental exposure to pesticides. Risk characterization is a basic step in the assessment and management of the health risks related to chemicals (Tordoir and Maroni, 1994). Evaluation of exposure, which may be performed through environmental and biological monitoring, is a fundamental component of risk assessment. Biomarkers are useful tools that may be used in risk assessment to confirm exposure or to quantify it by estimating the internal dose. Besides their use in risk assessment, biomarkers also represent a fundamental tool to improve the effectiveness of medical and epidemiological surveillance. 

Simmonds PL, Luckhurst CL, Woods JS. 1995. Quantitative evaluation of heme biosynthetic pathway parameters as biomarkers of low-level lead exposure in rats. J Toxicol Environ Health 44 351-367. 

Many diseases are characterized by the expression of specific proteins1 in some cases, malignant cells yield unique protein profiles when total cellular protein extracts are analyzed by proteomic methods such as two-dimensional gel electrophoresis or matrix-assisted laser desorption ionization-mass spectrometry (MALDI-MS).2 High-throughput proteomic studies may be useful to differentiate normal cells from cancer cells, to identify and define the use of biomarkers for specific cancers, and to characterize the clinical course of disease. Proteomics can also be used to isolate and characterize potential drug targets and to evaluate the efficacy of treatments. 

C.M. Leys, S. Nomura, E. Montogomery, and J.R. Goldenring, Tissue microarray evaluation of prothymosin as a biomarker for human gastric metaplasia and neoplasia. J. Surg. Res. 121, 327-328 (2004). 

Lecoeur S, Videmann B, Bemy P (2004) Evaluation of metallothionein as a biomarker of single and combined Cd/Cu exposure in Dreissena polymorpha. Environ Res 94(2) 184—191... 

The resulting device has demonstrated both FDG and FLT labelling at yields of 98% and 90%, respectively, in 100 s compared to typical macro-scale labelling of 65% in 45 min for FDG and 30% in 90 min for FLT. The use of acetonitrile, DMSO and HC1 have shown no degrading effect on the system. Extremely efficient labelling illustrates the effectiveness of flow-based micro-reactors for PET biomarker synthesis. Multiple biomarkers can be produced in 1-2 min, while using only micro-litres of precursor and can revolutionise the production of radiotracers. Small reaction volumes, improved yields, and the ability to synthesise small quantities of a variety of new compounds will allow preclinical and clinical evaluation of new PET agents with potential for clinical utilisation. 

Short-term non-invasive biomarkers for processes producing long-term lung damage-evaluation of the feasibility of candidate measurement systems. Toxicokinetic models have been developed to determine whether breath analysis of pentane and ethane can be used to estimate chronic lung damage from toxicants. 

In clinical trials, biomarkers are used to indicate a particular disease state and its progression. They may be used as surrogate markers in the evaluation of the effectiveness of a drug as representative of the natural endpoint such as survival rate or irreversible morbidity. 

In the past few years the use of rotifers in ecotoxicological studies has substantially increased. The main endpoints used are mortality, reproduction, behavior, cellular biomarkers, mesocosms, and species diversity in natural populations [126]. Several workers have used Brachionus calyciflorus for various types of toxicity assessments. Thus, comprehensive evaluation of approximately 400 environmental samples for the toxicity assessment of solid waste elutriates, monitoring wells, effluents, sediment pore water, and sewage sludge was carried out by Persoone and Janssen [127]. The mortality of rotifers hatched from cysts is evaluated after 24 hours exposure. This microbiotest has been commercialized in a Rotoxkit F [128,129]. 

An important qualification must be made. While a biomarker may be of proven value in establishing whether a drug has the desired effect in patients or healthy volunteers (see Section 4.6.3) and for evaluation of the dose-response relationship, a biomarker may not be a surrogate for the clinical endpoint. Thus, suppression of testosterone after an initial rise will give an almost immediate endpoint for the effect of GnRH analogues in prostate cancer but the relationship breaks down later in the disease. Measures of blood glucose control are vital... 

Table 4.5 Examples of biomarkers of established utility in early drug evaluation in patients ...

Of course, it is not always necessary to rely on biomarkers for rapid evaluation of dose-response relationships in ED. Thus, efficacy of new drugs is readily demonstrated in terms of the clinical endpoint for diseases, such as migraine, inflammatory pain, asthma, psoriasis, glaucoma and many others. 

Vainio H, Morgan G, Kleihues P. An international evaluation of the cancer-preventive potential of non-steroidal anti-inflammatory drugs. Cancer Epidemiol Biomarkers Prev 1997 6 749-753. 

The various organs of the immune system such as spleen, lymph nodes, thymus and bone marrow containing the cells involved in the various immune responses offer the possibility to harvest these cells and perform in vitro assays for evaluation of effects on the immune system. When part of an in vivo animal study this may indicate a direct toxic effect of pharmaceuticals, that is, immunosuppression (Table 18.2). So, it is feasible to obtain cell suspensions for further evaluation such as determination of cellular subsets of T and B leukocytes by fluorescent activated cell sorter analysis (FACS analysis), and determination of natural killer (NK) cell activity of the spleen cell population. An advantage of this approach is that it may lead to identification of a biomarker to be used in clinical studies. In addition, in vitro stimulation of spleen cells with mitogens activating specific subsets may indicate potential effects on the functionality of splenic cell populations. Concanavalin A (Con A) and phytohemagglutinin (PHA) activate Tcells, while lipopolysaccharide (LPS) activates primarily B cell populations. Blood is collected for total white blood cell (WBC) determination and blood cell differential count. In addition, serum can be obtained for determination of serum immunoglobulins. 

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