Gene Expression Profiles of Acute Asthma: Subphenotypes of Treatment Response

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Gene Expression Profiles of Acute Asthma
Subphenotypes of Treatment Response

• Kelly Allred Metz, MD
• Cincinnati Childrens Hospital Medical Center

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Asthma Admissions

• At CCHMC, 3000 children are seen annually in the
  ED for acute asthma exacerbations
• 25 admitted
• 25 of admitted stay 24 hours
• Among hospitalized children for treatment of
  acute asthma exacerbation, up to 27 require
  longer than 3 day stay

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Heterogeneity of Asthma

• Heterogeneous phenotype among those admitted
• 75 discharged within 24 hours good
  responders
• 25 take longer poor responders
• Molecular classification of phenotypes may enable
  informed treatment plans

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Wheres Waldo?
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Wheres Waldo?
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Microarray

• Study expression of large numbers of genes
  simultaneously
• Identify gene expression profiles associated with
  disease states

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Microarray and Bronchial Tissue

• Comparison of gene expression profiles from
  bronchial tissues of asthmatics before and after
  treatment with ICS
• 79 known genes differentially expressed in
  asthmatics
• After 28 days of ICS treatment, 26 (33) of the
  genes responded to ICS
• Microarray studies can identify genes modulated
  by treatment in the context of asthma

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Youre going to do what?
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Nasal Epithelium and Asthma

• Upper airway reflects pathophysiologic changes in
  the lower airway

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Nasal Epithelium in Asthma

• Similar inflammatory processes underlie rhinitis
  and asthma
• Nasal allergen challenge initiates pulmonary
  inflammation
• Segmental allergen challenge in the lung induces
  inflammation in bronchial and nasal mucosa
• Eosinophil counts in the nose correlate with
  those in the lung in patients with nonallergic
  asthma

Multiple studies, see reference list
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Microarray and Nasal Epithelium

• There are consistent gene expression profile
  signatures that are present in nasal epithelial
  RNA samples from children experiencing an acute
  asthma attack (v. stable asthma) at the time they
  present in the ED

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Patient Group
non-asthma
stable-asthma
acute-asthma
OBSERVED PATTERN
down in acute
down in acute and stable
872 probesets
up in acute
up in acute and stable
down in stable
up in stable
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Summary

• Microarray has been used previously to identify
  gene profiles associated with asthma, but
  previous studies have been limited to adult
  patients and to RNA derived from peripheral blood
  cells or bronchial biopsy specimens
• Microarray is validated by fact that many genes
  found to be induced in childhood asthma have been
  implicated in the pathogenesis of asthma in other
  studies

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Summary (cont)

• Human studies are limited by access to tissue
• Nasal epithelial cells serve as an accessible
  alternative proxy for lower respiratory
  epithelium
• Exacerbated asthma status is distinguished from
  stable asthma based on strong gene expression
  signatures in nasal epithelial samples

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Hypothesis

• The gene expression profiles of children who
  respond to treatment quickly (different than children who take longer ( 24
  hours) to respond at 24 hours and 2 weeks
• The change in the gene expression profile of each
  individual will change from initial presentation
  (before steroid), to 24 hours, and 2 week follow
  up

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Hypothesis (cont.)
24 hrs
ED
2 weeks
A 2
A 3
A 1
discharge
B 3
B 1
B 2
discharge

• A 2 ? B 2
• A 1 ? A 2 ? A 3
• B 1 ? B 2 ? B 3

Faster
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Patient Populations

• Ongoing registry of children with asthma and
  children presenting to the ED with asthma
• Ages 5-18 years
• Greater Cincinnati Metropolitan area

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Fellowship Goal PILOT STUDY
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Sample Size

• 80-100 admitted patients (15-20 patients for
  pilot)
• Over-sample 320-400 patients in ED

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Inclusion/Exclusion Criteria

• Inclusion criteria
• Age 5-18 years
• History of asthma
• Acute Asthma Exacerbation

• Exclusion criteria
• Nasal or systemic steroids in past 30 days
• Nebulized or inhaled steroids with face mask in
  past 30 days (may use mouthpiece spacer)
• Received Magnesium sulfate or Heliox
• Nasal obstruction
• Comoribid lung condition (CF, congenital,
  bronchopulmonary dysplasia, etc)
• D/c from NICU on O2
• Dependence on oral steroid or immunosuppressant
• Bleeding diathesis

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Outcomes

• Profile RNA expression pattern from nasal
  epithelium of children admitted for asthma
  exacerbations at 3 time points
• Will compare to
• Pediatric Asthma Severity Score (PASS)
• Asthma Control Test score (ACT)
• PFTs
• FENO
• to determine molecular heterogeneity of response
  to therapy

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Why are gene expression changes important?

• Can it be predictive?
• Not designed to predict treatment response
• Is designed to determine heterogeneity of
  response as measured by changes in gene
  expression profile over time

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Why are gene expression changes important?

• Implications
• If identify a gene in poor responders that does
  not respond to current treatment, may become
  target for novel therapy
• If identify a poor responder based on profile, in
  future may consider using alternative existing
  treatment, different dosing of same treatment, or
  longer course

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Potential Issues

• Definitions
• Good ( 24 hours) vs. poor responder ( 24 hours)
• Time to response to treatment, or time when
  eligible for discharge, will be based on when
  patient gets to Q4h x 2
• Allows for increased length of stay due to social
  or hospital system issues

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Potential Issues (cont.)

• Variables affecting the gene expression profile
• Severity of asthma exacerbation
• Exclude ICU admissions
• Exclude those who receive magnesium or Heliox
• Exclude mild exacerbations that are discharged
  home
• Prior treatment
• Exclude nasal steroids in past 30 days
• Exclude inhaled steroids IF nebulized or via face
  mask
• Exclude systemic steroids in past 30 days

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Potential Issues (cont.)

• Variables affecting the gene expression profile
• Concomitant respiratory infection
• Viral PCR performed on each patient, in
  collaboration with James Gern, MD in Madison, WI
• Examine relationship of presence of virus to
  change in profile in analysis
• Allergic rhinitis
• Including AR patients, excluding nasal steroids
• Examine relationship of specific IgE to change in
  profile in analysis

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Potential Gene Targets?
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Cilia, flagella, motility, B cell differentiation
up in acute-1
down in acute
Apoptosis, angiogenesis, proteolysis, signaling
Epigenetic regulation, RNA metabolism, nucleolus,
B cell differentiation
up in acute-2
Epithelial, transcription, membrane protein
signaling, carbohydrate catabolism
up in stabilized
Transcription, membrane protein signaling,
adhesion
down in stabilized
up in stabilized and acute
Myeloid activation, K-channel adhesion,
endothelial cell regeneration
stabilized-asthma
stabilized-asthma
acute-asthma
acute-asthma
non-asthma
non-asthma
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Investigators

• Gurjit Hershey, MD, PhD Allergy Immunology
• Rick Strait, MD Emergency Medicine
• Richard Ruddy, MD Emergency Medicine
• Carolyn Kercsmar, MD Pulmonary
• Jeffrey Simmons, MD General Pediatrics
• Robert Kahn, MD General Pediatrics
• Dennis Drotar, PhD Adherence Psychology
• Bruce Aronow, PhD Bioinformatics

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Thanks

• Dr. Elizabeth Matsui, MD
• Dr. Gurjit Khurana Hershey, MD, PhD
• Dr. Umasundari Sivaprasad, PhD
• Hershey lab members

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Additional References

• Nasal Epithelium and Asthma

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Additional References (cont.)