A diagnosis of amyotrophic lateral sclerosis typically means a person will survive for only two or three years—but some people live a decade or more. Patients, and their physicians, could benefit from a method that would help them predict how much time the person has left to live. In the December JAMA Neurology, researchers from the Pennsylvania State College of Medicine in Hershey present a step forward in the form of a panel of inflammatory biomarkers in both blood and cerebrospinal fluid (CSF). By analyzing half a dozen biomolecules, the researchers correctly predicted disease duration in 94 percent of cases in a small cohort. “Nothing is 100 percent certain,” cautioned senior author James Connor, "but a test like this could help people understand if their disease is likely to move quickly or slowly."

ALS researchers have been searching urgently for biomarkers for the diagnosis and prognosis. One hurdle, Connor suggested, has been the focus on single parameters. Researchers now realize that because ALS likely describes a syndrome with multiple etiologies, one biomarker may not fit all. The Hershey researchers, and others, have begun to compile lists of biomarkers that, together, could diagnose ALS, though no clinically validated test exits yet (Mitchell et al., 2009Mitchell et al., 2010Ranganathan et al., 2005). In the current study, they turn their attention to prognosis. Defining a panel of prognostic ALS markers, particularly by combining two different body fluids, is a relatively new approach, commented Robert Bowser of the Barrow Neurological Institute in Phoenix, who was not involved in the study.

First author Xiaowei “Bill” Su and colleagues examined plasma from 29 people and CSF from 33, all of whom had donated the fluids at the time of diagnosis and had since died. Some lived as little as nine months after diagnosis, others 16 years. The researchers genotyped the participants for the hemochromatosis gene (HFE), in which polymorphisms appear in about one-third of people with ALS, but only in one-tenth of the general population (Wang et al., 2004Goodall et al., 2005). Too few subjects were mutation carriers to make any inference about the gene’s effect on survival. HFE encodes an iron sensor. None of the people in the study had a family history of ALS and the researchers checked no other known ALS mutations, which are quite rare.

Because the immune system is known to play a role in ALS (see Oct 2008 news story; Sep 2009 news storyNov 2009 news story), Su and colleagues selected a commercial immunoassay kit to  measure 27 cytokines and growth factors in the fluid samples. HFE variants are somewhat prevalent in ALS and Connor has a longstanding interest in this gene (see Alzforum Webinar), hence the scientists also quantified eight molecules involved in iron metabolism.

Then, Su used multivariant modeling to identify biomarker panels that would best predict disease duration. The model started with the biomarker that correlated most tightly with survival, then successively added the next-best biomarkers, re-evaluating the correlation at each turn until it identified the most predictive set. Considering the 29 plasma samples, the model identified a panel that predicted disease duration “right on” in 18 cases, Connor said. For the 33 CSF samples, the computer came up with a panel that hit the mark in 21 cases. Eighteen participants donated both plasma and CSF, and for those the model accurately predicted the survival of all but one person, who passed away sooner than predicted.

The panel included six markers; high levels of these five predicted longer survival:

  • Plasma interferon-g-inducible protein 10 (IP-10), an anti-inflammatory cytokine that suppresses macrophages and antigen-presenting cells.
  • Plasma interleukin-5, a cytokine that promotes differentiation of white blood cells.
  • Plasma L-ferritin, the light chain of the iron storage molecule ferritin.
  • CSF monocyte chemoattractant protein-1 (MCP-1), which attracts certain immune cell types and is also implicated in Alzheimer’s disease.
  • CSF:Plasma ratio of Interferon-g (IFN-g), a pro-inflammatory molecule that activates macrophages and IP-10 production.

In contrast, high CSF interleukin 8 (IL-8), a pro-inflammatory cytokine that activates neutrophils, predicted shorter lifespan.

Overall, the results indicate that an increase in pro-inflammatory molecules combined with a decrease in anti-inflammatory mediators predicts faster ALS progression, Connor said.

Plenty Left To Do
“It is an interesting paper that needs to be replicated in a much larger set of samples,” commented Merit Cudkowicz of Massachusetts General Hospital in Boston in an email to Alzforum. “It is too preliminary to be conclusive,” agreed Stanley Appel of The Methodist Hospital Research Institute in Houston. In addition, Connor and Bowser said it would be important to examine these biomarkers in a longitudinal study.

Connor and colleagues hope that a panel like this, if verified, could aid clinical trials. By comparing a volunteer’s predicted to actual survival, researchers might be better able to determine if a drug worked. Trialists might also find that patients on a slow or fast track respond differently to medicines, suggested Lucie Bruijn of the ALS Association. While this would not necessarily allow researchers to plan smaller or shorter trials, Connor said, it would enable them to analyze or reanalyze results with a clearer understanding of predicted disease duration. Notably, past data from several trials are now available to researchers (see Dec 12 news story). Appel cautioned that a biomarker based on inflammatory molecules likely would be a poor general outcome measure for all ALS clinical trials. It could be useful for medicines that specifically target that immune state (for example, see Mar 2010 news storyFeb 2012 news storyJan 2013 news story).

In addition to traditional fluid biomarkers, scientists are testing novel measures of muscle physiology (see Oct 2011 news story) and brain imaging (see Jan 2009 news story).

Several roadblocks are slowing the development of robust biomarkers. Standardization is one challenge, noted Bowser. To identify and confirm biomarkers, investigators need large sets of samples that were all collected in a standardized manner. A biorepository managed by the Northeast ALS Consortium can help here, he noted (Sherman et al., 2011). In addition, commercial assays used in discovery, such as the kit Su worked with, typically vary between lots and are unsuitable for clinical applications, Bowser said (see Nov 2009 news series on biomarker quality control in Alzheimer's).

Even if those difficulties are surmounted, the best proof of a biomarker would be to show it correlates with survival benefits in a successful drug trial, noted Bruijn. Catch 22: That requires a good treatment.—Amber Dance

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References

News Citations

  1. Microglia in ALS: Helpful, Harmful, or Neutral?
  2. ALS: T Cells Step Up
  3. Peripheral Innate Immunity—Not So Peripheral to ALS?
  4. Chicago—ALS Database Opens for Business
  5. ALS-TDI Scours Transcriptome, Targets CD40L
  6. ALS: Speeding Ahead With Trial of Immunomodulator
  7. Chicago—ALS Clinical Trials: New Hope After Phase 3 Setbacks
  8. NEALS: Desperately Seeking ALS Biomarkers
  9. Portrait of a Motor Neuron Disease: Focus on Imaging for ALS
  10. Worldwide Quality Control Set to Tame Biomarker Variation

Webinar Citations

  1. Hemochromatosis as a Factor in AD

Paper Citations

  1. . A CSF biomarker panel for identification of patients with amyotrophic lateral sclerosis. Neurology. 2009 Jan 6;72(1):14-9. PubMed.
  2. . Plasma biomarkers associated with ALS and their relationship to iron homeostasis. Muscle Nerve. 2010 Jul;42(1):95-103. PubMed.
  3. . Proteomic profiling of cerebrospinal fluid identifies biomarkers for amyotrophic lateral sclerosis. J Neurochem. 2005 Dec;95(5):1461-71. PubMed.
  4. . Increased incidence of the Hfe mutation in amyotrophic lateral sclerosis and related cellular consequences. J Neurol Sci. 2004 Dec 15;227(1):27-33. PubMed.
  5. . Association of the H63D polymorphism in the hemochromatosis gene with sporadic ALS. Neurology. 2005 Sep 27;65(6):934-7. PubMed.
  6. . Proposed BioRepository platform solution for the ALS research community. Amyotroph Lateral Scler. 2011 Jan;12(1):11-6. PubMed.

Further Reading

Papers

  1. . Inflammatory mediators as biomarkers in brain disorders. Inflammation. 2014 Jun;37(3):639-48. PubMed.
  2. . Amyotrophic lateral sclerosis: Problems and prospects. Ann Neurol. 2013 Sep;74(3):309-16. PubMed.
  3. . Mechanisms, models and biomarkers in amyotrophic lateral sclerosis. Amyotroph Lateral Scler Frontotemporal Degener. 2013 May;14 Suppl 1:19-32. PubMed.
  4. . pNfH is a promising biomarker for ALS. Amyotroph Lateral Scler Frontotemporal Degener. 2013 Mar;14(2):146-9. PubMed.
  5. . Proteome analysis of body fluids for amyotrophic lateral sclerosis biomarker discovery. Proteomics Clin Appl. 2013 Jan;7(1-2):123-35. PubMed.
  6. . Roadmap and standard operating procedures for biobanking and discovery of neurochemical markers in ALS. Amyotroph Lateral Scler. 2012 Jan;13(1):1-10. PubMed.
  7. . Phosphorylated neurofilament heavy subunit (pNF-H) in peripheral blood and CSF as a potential prognostic biomarker in amyotrophic lateral sclerosis. J Neurol Neurosurg Psychiatry. 2013 Apr;84(4):467-72. Epub 2012 Oct 31 PubMed.

Primary Papers

  1. . Biomarker-Based Predictive Models for Prognosis in Amyotrophic Lateral Sclerosis. JAMA Neurol. 2013 Oct 21; PubMed.