High Platelet Levels Attenuate the Efficacy of Platinum-Based Treatment in Non-Small Cell Lung Cancer.

BACKGROUND/AIMS: The correlation between platelet levels and clinical outcomes has received increasing attention, but it is not yet clear whether and how platelet levels affect the therapeutic response in non-small cell lung cancer (NSCLC). In the current study, we aimed to explore the role of platelet levels in responsive to platinum-based chemotherapy and investigated the underlying mechanism.

METHODS: We evaluated the possibility of platelet level as a biomarker for response to platinum-based therapy in NSCLC by retrospective analysis of NSCLC patients. Cell proliferation was evaluated using cell counter and flow cytometry. Cell capillary-like structures of HPMEC were estimated with ECMatrix. The effect of platelets on A549, H1299, and HPMEC apoptosis was measured by flow cytometry. A A549-bearing NOD/ SCID mice model was employed to determine whether platelets could counteract cisplatin-induced apoptosis in vivo. In vivo cell proliferation and apoptosis were evaluated with Ki-67 antibody and TUNEL staining respectively. The angiogenesis of tumor was estimated by CD31 microvessel density. The protein levels of Akt, Bad and Bcl-2 were assessed by western blot. To further examine platelet-driven effects of the chemotherapeutic response, we used platelet depletion and platelet transfusion in A549-bearing NOD/SCID mice.

RESULTS: Thrombocytosis at NSCLC diagnosis was associated with lower progression-free survival and median overall survival. Platelet levels before chemotherapy in the no response group were markedly higher than in the responsive group. Platelets rescued the inhibition of cell proliferation and angiogenesis and protected against cell apoptosis induced by cisplatin, platelets rescued cisplatin-induced apoptosis via the Akt/Bad/Bcl-2 signaling pathway under endoplasmic reticulum stress. Platelet transfusion decreased the therapeutic effect of cisplatin, while it was increased by platelet depletion.

CONCLUSION: We confirmed an important anti-apoptosis mechanism mediated by platelets and found that platelets could counteract cisplatin-induced apoptosis. Reducing platelet levels or blocking platelet-based cytoprotection may represent new methods for improving the chemotherapeutic effect.