Increased megakaryocytic proliferation, pro-platelet deposition and expression of fibrosis-associated factors in children with chronic myeloid leukaemia with bone marrow fibrosis

Abstract

Paediatric chronic myeloid leukaemia (ped-CML) is rare and ped-CML with fibre accumulation in the bone marrow (MF) is thought to be even rarer. In adults (ad-CML), fibrosis represents an adverse prognostic factor. So far, the pro-fibrotic changes in the bone marrow microenvironment have not been investigated in detail in ped-CML. From a total of 66 ped-CML in chronic phase, biopsies were analysable and 10 had MF1/2 (MF1, n=8/10; MF2, n=2/10). We randomly selected 16 ped-CML and 16 ad-CML cases with and without fibrosis (each n=8) as well as 18 non-neoplastic controls. Bone marrow samples were analysed with a real-time PCR-based assay (including 127 genes for paediatric cases) and by immunohistochemistry. We found increased expression of megakaryocytic genes in ped-CML. The number of megakaryocytes and pro-platelets are increased in CML patients, but the most significant increase was noted for ped-CML-MF1/2. Anti-fibrotic MMP9 expression was lower in children than in adults. Cell mobilisation-related CXCL12 was decreased in young and adult patients with CML but not the corresponding receptor CXCR4. In summary, fibre accumulation in ped-CML-MF1/2 is associated with increased megakaryocytic proliferation and increased interstitial pro-platelet deposition. Deregulated expression of matrix-modulating factors shifts the bone marrow microenvironment towards fibrosis.

Molecular profile of inflammatory and megakaryocytic factors in pediatric myelodysplastic syndrome with acute myelofibrosis

“…Comparison with the other two cases showed that megakaryocytic morphology at MF0 stage in case #1 was similar to ped‐MDS‐MF2 in case #2, while at MF2 stage, proplatelet deposition was similar to ped‐PMF in case #3 (Figure ). Adult patients with PMF and children with chronic myeloid leukemia with MF1/2 show a similar increase of proplatelets . The increase in proplatelet deposition within 4 months in case #1 was paralleled by a decrease in peripheral blood platelets and a 12.8‐fold decrease in tubulin beta class I (TUBB).…”

“…A relative transcript expression level of >1 at MF2 stage was detected for THBS1 (3.1‐fold increase), transforming growth factor beta 1 (TGFB1, 3.1‐fold), TIMP metallopeptidase inhibitor 1 (TIMP1, 5.6‐fold), platelet and endothelial cell adhesion molecule 1 (PECAM1, 2.5‐fold), integrin subunit beta 3 (ITGB3, 1.3‐fold) matrix metallopeptidase 9 (MMP9, 4.5‐fold), C‐C motif chemokine ligand 5 (CCL5, 2.8‐fold), and C‐X‐C motif chemokine ligand 12 (CXCL12, 2.6‐fold). THBS1, TIMP1, PECAM1, and ITGB3 are produced by megakaryocytes, a cell type which is thought to be a major contributor to fibrosis . Conventional histology showed no change in megakaryocytic dysplasia; but immunohistochemistry revealed a massive increase in the quantity and density of THBS1 − /CD42b + proplatelets, from a few scattered round depositions to dense nets of elongated proplatelets (Figure ).…”

“…We investigated the gene expression profile of 119 fibrosis/angiogenesis‐related factors and performed immunohistochemistry as described …”

“…Biopsy of case #2 had been taken at presentation, and in case #3, 20 months after presentation (this first biopsy was not suitable for molecular analysis). These three cases were compared to 10 pediatric control cases which have been analyzed previously …”

“… SUPPLEMENTARY TABLE S1 Molecular expression profile in bone marrow samples from acute fibrosis in ped‐MDS. Note that profiles of controls refer to previously published data with the same real‐time quantitative PCR assay . ND, not detectable…”