Effective treatment of psoriasis with etanercept is linked to suppression of IL-17 signaling, not immediate response TNF genes

Abstract

Background: TNF inhibitors have revolutionized the treatment of psoriasis vulgaris as well as psoriatic and rheumatoid arthritis and Crohn disease. Despite our understanding that these agents block TNF, their complex mechanism of action in disease resolution is still unclear.

Objective: To analyze globally the genomic effects of TNF inhibition in patients with psoriasis, and to compare genomic profiles of patients who responded or did not respond to treatment.

Methods: In a clinical trial using etanercept TNF inhibitor to treat psoriasis vulgaris (n = 15), Affymetrix gene arrays were used to analyze gene profiles in lesional skin at multiple time points during drug treatment (baseline and weeks 1, 2, 4, and 12) compared with nonlesional skin. Patients were stratified as responders (n = 11) or nonresponders (n = 4) on the basis of histologic disease resolution. Cluster analysis was used to define gene sets that were modulated with similar magnitude and velocity over time.

Results: In responders, 4 clusters of downregulated genes and 3 clusters of upregulated genes were identified. Genes downmodulated most rapidly reflected direct inhibition of myeloid lineage immune genes. Upregulated genes included the stable dendritic cell population genes CD1c and CD207 (langerin). Comparison of responders and nonresponders revealed rapid downmodulation of innate IL-1beta and IL-8 sepsis cascade cytokines in both groups, but only responders downregulated IL-17 pathway genes to baseline levels.

Conclusion: Although both responders and nonresponders to etanercept inactivated sepsis cascade cytokines, response to etanercept is dependent on inactivation of myeloid dendritic cell genes and inactivation of the T(H)17 immune response.

Figure 1. Consensus clustering grouped genes down-regulated by etanercept into 4 clusters

(a) Consensus clustering of genes down-modulated in patients who responded to etanercept treatment (n=11) identified 4 gene clusters that were down-modulated at different time points during the course of etanercept treatment: “immediate”, “early”, “mid”, and “late” clusters. Gene expression in lesional skin at weeks 0, 1, 2, 4 and 12 was normalized to non-lesional gene expression, and shown as average cluster gene expression +/− SEM. (b) Heat map of each down-modulated gene cluster.

Figure 2. Consensus clustering grouped genes up-regulated by etanercept into 3 clusters

(a) Consensus clustering of genes up-regulated in patients who responded to etanercept treatment (n=11) identified 3 clusters, “up early”, up mid”, and up late”. (b) Cell counts for CD1c and CD207 (Langerin) for psoriasis lesional skin, week 2 and at wk 12. Mean cell counts indicated. *p<0.05, ***p<0.001.

Figure 3. Mean gene expression profile for “sepsis cascade” genes IL-1β and IL-8

(a) Down-modulation of gene expression for IL-1β and IL-8 in both responders (n=11, filled line) and non-responders (n=4, dashed line) (microarray data). (b) Mean log2 expression normalized to HARP for IL-1β and IL-8 in responders (filled line) and non-responders (dashed line) during etanercept treatment (RT-PCR data). At week 12 there was significant reduction of IL-1β in responders (p<0.0001), and non-responders (p=0.020). Similarly, at week 12 there was significant reduction of IL-8 in responders (p<0.0001), and non-responders (p=0.004).

Figure 4. Consensus clustering grouped genes that were different in responders and non-responders

(a) Consensus clustering of genes that were different in responders and non-responders grouped genes into 4 clusters. (b) Heat map of cluster 1. There was a group of genes that were down-regulated at baseline in non-responders but not responders (black box).

Figure 5. Profiles of “cytokine pathways” in etanercept gene sets in responders and non-ersponders, using GSEA analysis

Keratinocyte cytokine “pathways” were created by culturing primary human keratinocytes with either IL-17, TNF, or IFNγ and defining cytokine pathway gene sets (“IL-17”, “TNF specific”, “IL-17 & TNF”, and “IFNγ”) . (a, b, c, d) Genes modulated by etanercept over time were analyzed by GSEA. Average normalized expression (+/− 95% confidence interval) was plotted over time. Responders showed significant down-modulation of IL-17 pathway genes compared to non-responders.