Platelet Microparticles Decrease Daunorubicin-Induced DNA Damage and Modulate Intrinsic Apoptosis in THP-1 Cells

Influence on therapeutic outcome of platelet count at diagnosis in patients with de novo non-APL acute myeloid leukemia

BACKGROUND

Platelet (PLT) count at diagnosis plays an important role in cancer development and progression in solid tumors. However, it remains controversial whether PLT count at diagnosis influences therapeutic outcome in patients with non-acute promyelocytic leukemia (APL) acute myeloid leukemia (AML).

METHODS

This study analyzed the relationship between PLT count at diagnosis and genetic mutations in a cohort of 330 newly diagnosed non-APL AML patients. The impact of PLT count on complete remission, minimal residual disease status and relapse-free survival (RFS) were evaluated after chemotherapy or allogeneic hematopoietic stem cell transplantation (allo-HSCT).

RESULTS

Our studies showed that patients with DNMT3A mutations have a higher PLT count at diagnosis, while patients with CEBPA biallelic mutations or t(8;21)(q22; q22) translocation had lower PLT count at diagnosis. Furthermore, non-APL AML patients with high platelet count (> 65 × 109/L) at diagnosis had worse response to induction chemotherapy and RFS than those with low PLT count. In addition, allo-HSCT could not absolutely attenuated the negative impact of high PLT count on the survival of non-APL AML patients.

CONCLUSION

PLT count at diagnosis has a predictive value for therapeutic outcome for non-APL AML patients.

Proteomic and functional profiling of platelet-derived extracellular vesicles released under physiological or tumor-associated conditions

During hemostasis, thrombosis, and inflammation, activated blood platelets release extracellular vesicles (PEVs) that represent biological mediators of physiological and pathological processes. We have recently demonstrated that the activation of platelets by breast cancer cells is accompanied by a massive release of PEVs, evidence that matches with the observation that breast cancer patients display increased levels of circulating PEVs. A core concept in PEVs biology is that their nature, composition and biological function are strongly influenced by the conditions that induced their release. In this study we have performed a comparative characterization of PEVs released by platelets upon activation with thrombin, a potent thrombotic stimulus, and upon exposure to the breast cancer cell line MDA-MB-231. By nanoparticle tracking analysis and tandem mass spectrometry we have characterized the two populations of PEVs, showing that the thrombotic and tumoral stimuli produced vesicles that largely differ in protein composition. The bioinformatic analysis of the proteomic data led to the identification of signaling pathways that can be differently affected by the two PEVs population in target cells. Specifically, we have demonstrated that both thrombin- and cancer-cell-induced PEVs reduce the migration and potentiate Ca2+-induced apoptosis of Jurkat cells, but only thrombin-derived PEVs also potentiate cell necrosis. Our results demonstrate that stimulation of platelets by thrombotic or tumoral stimuli induces the release of PEVs with different protein composition that, in turn, may elicit selective biological responses in target cells.

Platelet-Acute Leukemia Interactions

Acute leukemia (AL) is a hematological malignancy with high morbidity and mortality that is caused by abnormal hematopoietic stem cells. AL can change the parameters, quality, and function of platelets through numerous mechanisms, resulting in bleeding and even death in AL patients. Hence, AL patients are often clinically treated using normal platelet transfusion. However, studies have found that platelets can also affect AL cells. This review discusses the changes occurring in platelet count, mean platelet volume, platelet distribution width, reticulated platelets, platelet membrane glycoprotein, platelet aggregation, and activation in AL patients, the causes of these changes, and the possible significance of these changes for patient prognosis. The effects of platelets on the proliferation and drug resistance of AL cells are also discussed.