Megakaryocyte Diversity in Ontogeny, Functions and Cell-Cell Interactions

Hematopoietic stem cells (HSCs) rely on local interactions in the bone marrow (BM) microenvironment with stromal cells and other hematopoietic cells that facilitate their survival and proliferation, and also regulate their functions. HSCs and multipotent progenitor cells differentiate into lineage-specific progenitors that generate all blood and immune cells. Megakaryocytes (Mks) are hematopoietic cells responsible for producing blood platelets, which are essential for normal hemostasis and blood coagulation. Although the most prominent function of Mks is platelet production (thrombopoiesis), other increasingly recognized functions include HSC maintenance and host immune response. However, whether and how these diverse programs are executed by different Mk subpopulations remains poorly understood. This Perspective summarizes our current understanding of diversity in ontogeny, functions and cell-cell interactions. Cumulative evidence suggests that BM microenvironment dysfunction, partly caused by mutated Mks, can induce or alter the progression of a variety of hematologic malignancies, including myeloproliferative neoplasms (MPNs) and other disorders associated with tissue scarring (fibrosis). Therefore, as an example of the heterogeneous functions of Mks in malignant hematopoiesis, we will discuss the role of Mks in the onset and progression of BM fibrosis. In this regard, abnormal interactions between of Mks and other immune cells might directly contribute to fibrotic diseases. Overall, further understanding of megakaryopoiesis and how Mks interact with HSCs and immune cells has potential clinical implications for stem cell transplantation and other therapies for hematologic malignancies, as well as for treatments to stimulate platelet production and prevent thrombocytopenia.

Presence of intra-tumoral CD61+ megakaryocytes predicts poor prognosis in non-small cell lung cancer

Background

Lung is a reservoir for megakaryocytes (MKs). The relationship between intra-tumoral MKs and non-small cell lung cancer (NSCLC) is unknown. We investigate relationship between high intra-tumoral MKs with the recurrence of NSCLC.

Methods

The tissue sections of 629 patients with resected NSCLC were stained with hematoxylin, anti-CD61, anti-CD34 and stromal cell-derived factor-1 (SDF-1). CD61+ giant cells localized in CD34+ capillaries were identified as MKs. The impact of MKs and preoperative platelet count on disease-free survival (DFS) was investigated.

Results

Overall, 18.9% of patients were positive for the presence of MKs. In univariate analysis, the median DFS of the MK+ group was shorter than the median DFS of the MK- group (69.1 vs. 80.5 months; P=0.021). Multivariate analysis indicated that MKs in tumor tissue was an unfavorable prognostic factor for DFS (HR 1.351, P=0.065), the impact of which was more significant in non-squamous cell carcinoma (NSCC) (HR 1.710, P=0.008) and in patients with N0 (HR 1.883, P=0.009). Although systemic platelet count of the MK+ group was significantly higher than the MK- group (270.6×10⁹ vs. 243.6×10⁹/L, P=0.007), the stratified subgroup DFS curves (P=0.003) showed that the effect of MKs on prognosis was independent of the blood platelet count.

Conclusions

Our results demonstrate that CD61+ MKs in tumor tissue predict unfavorable prognosis in NSCLC.