Gene expression profiling distinguishes prefibrotic from overtly fibrotic myeloproliferative neoplasms and identifies disease subsets with distinct inflammatory signatures

Abstract

The Philadelphia chromosome-negative myeloproliferative neoplasms (MPN) share similar molecular characteristics in that they frequently harbor hotspot mutations in JAK2 , CALR or MPL , leading to activated JAK/STAT signaling. However, these MPN have distinct symptoms, morphology, and natural histories, including different tendencies to progress to fibrosis. Although the role of inflammation in tissue fibrosis is well recognized, inflammatory gene expression in bone marrows involved by MPN has been understudied. We analyzed the expression of inflammatory genes by directly measuring RNA transcript abundance in bone marrow biopsies of 108 MPN patients. Unsupervised analyses identified gene expression patterns that distinguish prefibrotic (grade 1–2) MPN from overtly fibrotic (grade 2–3) MPN with high sensitivity and specificity in two independent cohorts. Furthermore, prefibrotic and overtly fibrotic MPN are separable into subsets with different activities in biological pathways linked to inflammation, including cytokines, chemokines, interferon response, and toll-like receptor signaling. In conclusion, this study demonstrates that MPN with overt fibrosis is associated with significant inflammatory gene upregulation in the bone marrow, revealing potential roles for multiple pro-inflammatory signaling networks in the development of myelofibrosis and suggesting potential therapeutic mechanisms to alleviate this process in the bone marrow microenvironment.

Cytokine Profiling in Myeloproliferative Neoplasms: Overview on Phenotype Correlation, Outcome Prediction, and Role of Genetic Variants

“…In their gene expression analysis, Wong and colleagues observed that TGFB2 was significantly up-regulated by 3.1-fold in MPL-mutated patients [80]. Finally, Barosi et al demonstrated the prognostic impact of increased sIL2RA levels only in JAK2V617F-and not in CALR-mutated PMF patients [74].…”

“…In 2019, Wong et al [80] analyzed the expression of inflammatory genes in 108 MPNs (N = 13 prePMF, N = 23 overtPMF, N = 31 ET, N = 25 PV, and N = 16 MPN-unclassifiable) by directly measuring RNA transcript abundance in bone marrow biopsies using Nanostring technology, and demonstrated that the inflammatory gene expression profile differs significantly between MPNs with fibrosis grade 0-1 (pre-fibrotic) and MPNs with grade 2-3 (overtly fibrotic). Indeed, pre-fibrotic MPNs display a "low" cytokine gene expression profile, while overtly fibrotic MPNs have marked up-regulation of inflammatory genes.…”

“…This suggests how distinct inflammatory pathways can lead to a common phenotype of clonal-derived bone marrow fibrosis. On the other hand, it should also be considered that fibrosis itself induces an alteration of bone marrow spatial architecture and cellular composition that may influence inflammatory gene expression profile (up-regulation of genes involved in myofibroblast proliferation, osteoclast differentiation, and angiogenesis) [80].…”

“…Then, if we compare PMF with ET and PV (Table 2), surprisingly, not all inflammatory mediators are increased. Indeed, of the 29 cytokines whose levels and/or expression have been investigated in PMF as compared to the other two MPNs, 15 are increased (IL-2, sIL-2R, IL-6, IL-12, IL-17, TNF-α, INF-α, IL1RA, IL-4, IL-10, MIP-1β, RANTES, FGF, TPO, TGF-β) [63,70,72,80], IL1-α is similar [63], MCP-1 similar or increased, according to different studies [72,80], five cytokines are decreased (IL-7, VEGF, MIG, GRO-α, and CCL11) [70,75,79], and five show contradictory findings (both increased and decreased according to different reports: INF-γ, MIP-1α, IP-10, GM-CSF, EGF) [70,72,75,80]. The only mediators that are steadily elevated are pro-fibrotic cytokines, such as TGF-β, MCP-1, and FGF ( Table 2), suggesting that while inflammation is a common denominator of all three MPNs, PMF is characterized by a unique fibrogenic cytokine signature.…”

“…Furthermore, Wong et al observed an overexpression of fibrogenic genes-particularly of CCL2-is not strictly related to overt-PMF per se, but in general to MPNs at overtly fibrotic stage (i.e., MPN-unclassifiable with ≥2 degree of bone marrow fibrosis) [80].…”