# Morphology, Morphometry, and Immunohistochemical Profile of Megakaryocytes and Bone Marrow Microenvironment in Disease Progression and Therapy Resistance in Chronic Myeloid Leukemia

## TL;DR

This study explores how megakaryocyte features and bone marrow environment relate to treatment resistance and disease progression in chronic myeloid leukemia.

## Contribution

The study identifies CD44-positive megakaryocytes as a novel marker linked to poor treatment outcomes in CML.

## Key findings

- Megakaryocyte morphology and size were heterogeneous in CML but did not differ significantly between disease phases.
- CD44-positive megakaryocytes were associated with disease progression during therapy.
- Other markers like VEGF and FOXP3 showed variable expression but no significant link to treatment outcomes.

## Abstract

Background

Tyrosine kinase inhibitors have revolutionized the treatment of chronic myeloid leukemia (CML) since the beginning of the century. However, resistance to therapy and the progression of disease tend to occur in certain patients. The bone marrow microenvironment may play a role in the disease outcome. Megakaryocytes have multiple roles in the regulation and maintenance of the hematopoietic stem cell microenvironment. In the current study, we evaluated the association of megakaryocyte morphology, morphometry, and microenvironment with disease progression and therapy resistance in CML.

Methodology

Megakaryocyte morphology and morphometry were analyzed and compared between the different phases (chronic and advanced) at diagnosis in 150 cases of BCR-ABL-positive CML. All CML-CP patients (n = 119) were followed up on tyrosine kinase inhibitor therapy for a minimum of 15 months and classified based on their treatment outcome as a response, resistance to therapy, or progression of disease based on standard criteria. Immunohistochemistry on a bone marrow trephine biopsy was done for vascular endothelial growth factor (VEGF), FOXP3, CD150, CD48, CD44, osteopontin, CXCL12, N-cadherin, PDL-1, and IL-7, and their expression on megakaryocytes and their association with treatment outcome was evaluated.

Results

The morphology and morphometry of megakaryocytes showed a heterogeneous population in CML. Morphology and morphometric parameters, when compared between the chronic and advanced phases of disease at diagnosis, did not show any statistical difference. Megakaryocytes were variably positive for VEGF, FOXP3, CD150, CD48, osteopontin, N-cadherin, CXCL12, CD44, PDL-1, and IL-7. However, only CD44-positive megakaryocytes were statistically associated with the treatment outcome. The patients with a higher expression of CD44 megakaryocytes progressed to the advanced phase of the disease during therapy compared to those who responded.

Conclusion

Megakaryocyte morphology and morphometry were heterogeneous in CML; however, they did not show any significant difference with either the phase of the disease or with treatment outcomes. Among the various immunohistochemical markers of the microenvironment, only CD44-positivity on megakaryocytes was associated with poor treatment outcomes.