Platelet-T cell aggregates in lung cancer patients: Implications for thrombosis.

Platelet-leukocyte aggregates (PLAs) are associated with increased thrombosis risk. The influence of PLA formation is especially important for cancer patients, since thrombosis accounts for approximately 10% of cancer-associated deaths. Our objective was to characterize and quantify PLAs in whole blood samples from lung cancer patients compared to healthy volunteers with the intent to analyze PLA formation in the context of lung cancer-associated thrombosis. Consenting lung cancer patients (57) and healthy volunteers (56) were enrolled at the Dana Cancer Center at the University of Toledo Health Science Campus. Peripheral blood samples were analyzed by flow cytometry. Patient medical history was reviewed through electronic medical records. Most importantly, we found lung cancer patients to have higher percentages of platelet-T cell aggregates (PTCAs) than healthy volunteers among both CD4+ T lymphocyte and CD8+ T lymphocyte populations. Our findings demonstrate that characterization of PTCAs may have clinical utility in differentiating lung cancer patients from healthy volunteers and stratifying lung cancer patients by history of thrombosis.

Cancer and Thrombosis: The Platelet Perspective.

Platelets are critical to hemostatic and immunological function, and are key players in cancer progression, metastasis, and cancer-related thrombosis. Platelets interact with immune cells to stimulate anti-tumor responses and can be activated by immune cells and tumor cells. Platelet activation can lead to complex interactions between platelets and tumor cells. Platelets facilitate cancer progression and metastasis by: (1) forming aggregates with tumor cells; (2) inducing tumor growth, epithelial-mesenchymal transition, and invasion; (3) shielding circulating tumor cells from immune surveillance and killing; (4) facilitating tethering and arrest of circulating tumor cells; and (5) promoting angiogenesis and tumor cell establishment at distant sites. Tumor cell-activated platelets also predispose cancer patients to thrombotic events. Tumor cells and tumor-derived microparticles lead to thrombosis by secreting procoagulant factors, resulting in platelet activation and clotting. Platelets play a critical role in cancer progression and thrombosis, and markers of platelet-tumor cell interaction are candidates as biomarkers for cancer progression and thrombosis risk.

Optimal time-of-day and consolidation of learning in younger and older adults.

The current study investigated the relationship between intraindividual variability and associative learning in younger and older adults. The authors hypothesized that higher levels of intraindividual variability would be associated with a reduction in the benefits of practice during learning, and that nonoptimal testing times would magnify these effects. Results indicated that older adults showed an increase in reaction time (RT) standard deviation (SD) relative to mean RT in the evening. Although time-of-day did not have a significant effect on rate of learning or total learning, intraindividual variability did predict learning rate of younger adults at nonoptimal testing times. Results are discussed in light of theoretical models of aging and learning.

The effects of attention switching on encoding and retrieval of words in younger and older adults.

Two experiments examined the interaction between aging, attention switching, encoding process, and recognition memory using different versions of a cued attention switching paradigm. In Experiment 1, 30 younger and 35 older adults encoded words based on font color, meaning, or by explicit learning with a color response during performance of a choice-reaction time (RT) task. Attention switches were cued by means of stimulus location, and occurred on average every seven trials. In Experiment 2, attention switching was precued from a central fixation point and the number of critical switch trials was increased, occurring on average every four trials. Memory was assessed in both experiments by means of a forced-choice recognition task. Results indicated that, relative to color encoding, older adults benefited more than younger adults from semantic encoding, but less from explicit learning instructions. Attention switching disrupted encoding task performance of older adults more than that of younger adults, but recognition memory was generally unaffected. Results are discussed in light of theoretical models of aging memory that posit a role for executive control processing.