The hunt for cancer and infectious disease biomarkers

Current research is filled with examples of potential new biomarkers. The discovery of biomarkers leads to development of new laboratory tests to aid with earlier and more accurate disease detection. The definition of a biomarker is an “objective quantifiable characteristic of biological processes.”1 The most useful biomarkers demonstrate specificity and sensitivity, and have the capability to detect a disease at the earliest stage.1 Common biomarkers include proteins, antibodies, enzymes, cell receptors, metabolites, and molecular markers including microRNAs.

Introduction of biomarkers to clinical laboratory

Translating biomarker research into a test platform that is used in clinical laboratories is an arduous process. Early steps include developing a robust approach in each study, starting with target sample matrix and pre-analytical collection. Biomarkers must undergo rigorous analytical validation that produce statistically valid performance including accuracy, precision, and linearity calculations. In research settings, studies often have low numbers that require repeat studies with more numbers to prove stable and consistent performance.2 The best guide for determining the depth of analytical validation is to compare similar tests already being used in the clinical setting.2 In addition, biomarkers are tested clinically against previously diagnosed patients and those without the disease. Clinical validation for diagnostic accuracy includes sensitivity, specificity, odds ratios, positive predictive value, and negative predictive value statistics.2 As indicated above, the data requirements for clinically relevant biomarkers is expansive, and this is just the base level of the steps needed to translate biomarkers into lab tests. Research studies that are searching for clinical biomarkers must anticipate errors like bias and problem solving2 in their study design. Even after all the data collection and proving that the research has discovered a stable and reproducible biomarker, studies still have to evaluate if a test has clinical utility.2 As one can imagine, the lengthy approval process is further increased at the regulatory approval step. The approval process is accomplished through the Food and Drug Administration (FDA) or Laboratory Developed Test (LDT) routes.2 The FDA approval process depends on the risk to the patient and if there are similar tests in the market. LDTs are tests that are developed and tested in Clinical Laboratory Improvement Amendment (CLIA) accredited laboratories. Biomarkers are then evaluated through post-market testing to establish quality process and to determine if they are still clinically relevant.2 With such a long list of requirements, it is important to track the quality of biomarker studies—research groups are encouraged to register biomarker studies in a registry.2 The aim of the registry is to encourage biomarker research and guide the study designs to reduce poor study results. The wealth of opportunities in research reveals that the hunt for biomarkers is still worth the scientific rigors that biomarker testing presents.

Recent biomarker indicators

A recently identified biomarker being explored is microRNA, a byproduct of RNA transcription that are small sequences approximately 22 nucleotides long. These small sequences bind with messenger RNA (mRNA) eventually leading to the breakdown of mRNA and blocking translation of gene products. Naturally, microRNAs are found intracellularly; but microRNAs are also present and stable in circulating extracellular fluid.1 Circulating microRNA discovered in tuberculosis (TB) infections are among the first of these types of biomarkers being analyzed to help distinguish active from latent TB, as well as screen for non-pulmonary TB. There have also been studies looking at microRNA to evaluate sepsis, hepatitis B virus, Bordetella pertussis, Human Immunodeficiency Virus (HIV)-Associated Neurological Disorders (HAND), varicella zoster virus, influenza virus, and Hand, Foot, and Mouth Disease (HFMD)1—to name a few.

Another example is a Hepatocellular Cancer (HCC) biomarker study. Patients typically demonstrate risk factors which include hepatitis C virus infection and liver cirrhosis. These patients also present with late stage symptoms3 that include jaundice, enlarged liver, pain, and fever. HCC is the most lethal type of liver cancer with a five year survival rate.3 In a study by Di Poto et al. 2018, research evaluated alpha-fetoprotein (AFP), the standard biomarker for HCC with the intent to discover metabolites for newer biomarkers associated with high risk racial groups. AFP testing has demonstrated poor sensitivity in predicting HCC for patients with hepatitis C viral infections. More specifically, AFP is unable to distinguish between patients with cirrhosis and patients with HCC.3 The study discovered three metabolites of interest- alpha tocopherol (vitamin E), valine, and glycine. The metabolites showed different levels according to racial risk groups, specifically European and African American cohorts. Glycine was decreased in the European risk group and valine was increased in the African American risk group. Both risk groups demonstrated an increase in alpha tocopherol. The data in this study highlights some future biomarkers for HCC treatment and diagnosis.3

Biomarkers are also looked at to assist with studying different aspects of a disease. In one example, a study by Lin, Franceschi, and Clifford (2018) researched human papillomavirus (HPV) and its association with HIV leading to anal cancer. It is notable that 90 percent of anal cancers are attributed to HPV.4 Presence of HPV16, specifically, leads to a higher risk of cancer. HPV16 historically has been linked to cervical cancer. In this study, it is apparent that HPV16 was also a risk factor in both HIV positive and HIV negative patients that develop anal cancer as well. This study points to the possibility of using HPV biomarkers as a screening for anal cancer.4

Recently discovered biomarkers have been utilized to enhance the diagnosis of gastric cancer. Walker et al. 2018 explored biomarkers for gastric cancer following Helicobacter pylori infection.5 The study looked at tissue biomarkers Lgr5, CD133, and CD44, to use for stage assessment and help clinicians set follow up care timeframes.5 The study showed an increase in tissue levels as gastric cancer progressed from normal, intestinal metaplasia, dysplasia, and gastric cancer. Lgr5, CD133, and CD44 are unregulated and found in increased quantities in gastric cancer tissue epithelial cells.4 CD133 and CD44 are located in the cytoplasm of gastric epithelial cells.5 Lgr5 is located on the epithelial cell membrane.4 All three targets present opportunities for biomarker development to include research into improved histological stains. The need for early detection is still essential; most patients currently present with symptoms indicating tissue inflammation that manifest late in the disease process—too late for them to receive early, preventable treatments.

Following biomarker research is important to medical laboratory scientists. Each study reveals a little more of the puzzle surrounding bacterial or viral infections that lead to cancer. It opens up more questions about the possibility of routine screening for infections or public health interventions that could include implementing sanitation improvements in high risk populations. One well-known infection that research has shown to lead to gastric cancer, H. pylori, can develop antibiotic resistance, especially in high risk populations.6 Where do increased patient risk and biomarker opportunities meet? What about these populations specifically increases their risk for infection and cancer? These are questions yet to be fully realized. Staying current on the latest research can help educate clinical labs on new directions in testing in the future. Although it takes years to develop biomarkers into a useable lab test, knowing the latest research on biomarkers can guide clinical labs in test selection, or new testing algorithms.

  1. Correia C.N., Nalpas N.C.,, Circulating microRNAs as Potential Biomarkers of infectious Disease. Frontiers in Immunology. 16 February 2017. doi: 10.3389/fimmu.2017.00118.
  2. Duffy M.J., Sturgeon C.M.,, Validation of New Cancer Biomarkers: A Position Statement from the European Group on Tumor Markers. 2 April 2015. Clinical Chemistry. 61:6 809-820 (2015),
  3. Di Poto C., He S.,, Identification of race-associated metabolite biomarkers for hepatocellular carcinoma in patients with liver cirrhosis and hepatitis C virus infection. PLoS ONE. 2018 Mar 14. 13(3): e0192748. 
  4. Lin C., Franceschi S., Clifford G.M., Human papillomavirus types from infection to cancer in the anus, according to sex and HMLIV status: a systematic review and meta-analysis. Lancet Infect Dis. 2017 Nov 17. 18: 198–206.
  5. Walker R., Poleszczuk J.,, Toward early detection of Helicobacter pylori‑associated gastric cancer. Cross Mark, Gastric Cancer. 2017 July 19, 21:196–203.
  6. Duck W.M., Sobel J.,, Antimicrobial Resistance Incidence and Risk Factors among Helicobacter pylori–Infected Persons, United States. Emerging Infectious Disease, Centers for Disease Control. 2004 June; Volume 10, Number 6.