Platelet proteome and tumor dormancy: can platelets content serve as predictive biomarkers for exit of tumors from dormancy?

Abstract

Although tumor dormancy is highly prevalent, the underling mechanisms are still mostly unknown. It is unclear which lesions will progress and become a disseminated cancer, and which will remain dormant and asymptomatic. Yet, an improved ability to predict progression would open the possibility of timely treatment and improvement in outcomes. We have recently described the ability of platelets to selectively uptake angiogenesis regulators very early in tumor growth, and proposed their use as an early marker of malignancy. In this review we will summarize current knowledge about these processes and will discuss the possibility of using platelet content to predict presence of occult tumors.

Figure 1

Schematic presentation of changes in the balance of angiogenic factors in circulating platelets, which reflect the presence of tumors. Presence of even a microscopic dormant tumor can induce an increase in level of antiangiogenic factors in platelets, while presence of large, fast growing and angiogenic tumor results in an increase of angiogenic factors [4,5]. It should be recognized that this overall decrease or increase in the respective angiogenesis phenotype represent a change in the overall angiogenic function and that platelets of dormant tumor bearing mice may have a significant amount of pro-angiogenic proteins that are balanced by sufficient numbers of inhibitors.