The contribution of platelets is well recognized in thrombosis and hemostasis. However, platelets also promote tumor progression and metastasis through their crosstalk with various cells of the tumor microenvironment (TME). For example, several cancer models continue to show that platelet functions are readily altered by cancer cells upon activation leading to the formation of platelet-tumor aggregates, triggering release of soluble factors from platelet granules and altering platelet turnover. Further, activated platelets protect tumor cells from shear forces in circulation and assault of cytotoxic natural killer (NK) cells. Platelet-secreted factors promote proliferation of malignant cells, metastasis, and chemoresistance. Much of our knowledge of platelet biology in cancer has been achieved with animal models, particularly murine. However, this preclinical understanding of the complex pathophysiology is yet to be fully realized and translated to clinical trials in terms of new approaches to treat cancer via controlling the platelet function. In this review, we summarize the current state of knowledge of platelet physiology obtained through existing in vivo and in vitro cancer models, the complex interactions of platelets with cancer cells in TME and the pathways by which platelets may confer chemoresistance. Since the FDA Modernization Act recently passed by the US government has made animal models optional in drug approvals, we critically examine the existing and futuristic value of employing bioengineered microphysiological systems and organ-chips to understand the mechanistic role of platelets in cancer metastasis and exploring novel therapeutic targets for cancer prevention and treatment.
Keywords: Cancer; drug discovery; microphysiological systems; organ-chips; platelets; tumor microenvironment.
The recent passage of the FDA Modernization Act by the US government has removed the requirement of the use of animal models in disease modeling and drug discovery process. This has resulted in a much-renewed excitement within engineers, scientists, and industry in applying in vitro cell biosystems as a platform technology that assists or replaces animals in reproducing human biology. The contribution of platelets is well recognized in thrombosis and hemostasis. However, platelets also promote tumor progression and metastasis through their crosstalk with various cells of the tumor microenvironment. In this review, we summarize the current state of knowledge of platelet physiology obtained through existing cancer models and also critically examine the existing and futuristic value of employing bioengineered organ-chips to improve the knowledge of the underlying biology.