Platelets and cancer: a casual or causal relationship: revisited

Abstract

Human platelets arise as subcellular fragments of megakaryocytes in bone marrow. The physiologic demand, presence of disease such as cancer, or drug effects can regulate the production circulating platelets. Platelet biology is essential to hemostasis, vascular integrity, angiogenesis, inflammation, innate immunity, wound healing, and cancer biology. The most critical biological platelet response is serving as “First Responders” during the wounding process. The exposure of extracellular matrix proteins and intracellular components occurs after wounding. Numerous platelet receptors recognize matrix proteins that trigger platelet activation, adhesion, aggregation, and stabilization. Once activated, platelets change shape and degranulate to release growth factors and bioactive lipids into the blood stream. This cyclic process recruits and aggregates platelets along with thrombogenesis. This process facilitates wound closure or can recognize circulating pathologic bodies. Cancer cell entry into the blood stream triggers platelet-mediated recognition and is amplified by cell surface receptors, cellular products, extracellular factors, and immune cells. In some cases, these interactions suppress immune recognition and elimination of cancer cells or promote arrest at the endothelium, or entrapment in the microvasculature, and survival. This supports survival and spread of cancer cells and the establishment of secondary lesions to serve as important targets for prevention and therapy.

The Novel Association of Circulating Tumor Cells and Circulating Megakaryocytes with Prostate Cancer Prognosis

“…This is consistent to the finding of CD34 expression in mature-appearing megakaryocytes in reactive and disorders of bone marrows (40), and increased ploidization of megakaryocytes has been reported in patients with metastatic tumors (43). Platelets, which are released from megakaryocytes in bone marrow, have recently been recognized to play an important role in cancer metastasis (44,45), and the gene expression profile of platelets has been shown to efficiently distinguish individuals with or without cancers (46). Platelet counts have also been investigated for cancer prognosis, and the data are still in conflict (47).…”

Platelet‐to‐lymphocyte ratio predicts the prognosis of patients with non‐small cell lung cancer treated with surgery and postoperative adjuvant chemotherapy

“…The elevation of platelets could promote the metastatic potential of tumor cells through several pathways 21. Platelets have been reported to promote the development and enlargement of tumors by non‐inflammatory mechanisms, including stimulation of MM9 synthesis and production of adhesive molecules and growth factors (e.g.…”

White blood cell and platelet indices as prognostic markers in patients with invasive ductal breast carcinoma

“…Furthermore, it has been observed that platelets interact with malignant cells and suppress the inflammatory response against them. In addition, platelets secrete various growth factors and cytokines that promote angiogenesis, tumor growth, invasion and metastasis either directly or indirectly (4)(5)(6). Several clinical studies (7-10) have aimed to evaluate whether these interactions between white blood cells and platelets on one side and tumor cells on the other side may cause measurable alterations in blood parameters, as they are depicted in the complete blood count test.…”

“…White blood cells are key mediators in this response (2), in addition to platelets, which are involved in mechanisms promoting tumor growth and metastasis (4)(5)(6). Various white blood cell and platelet indices, including neutrophil-to-lymphocyte ratio, platelet count, mean platelet volume and platelet-to-lymphocyte ratio, have been reported as potential markers for predicting the progression or recurrence of disease and/or overall survival in several forms of cancer (7)(8)(9)(10).…”