Transcriptomic and functional characterization of megakaryocytic-derived platelet-like particles: impaired aggregation and prominent anti-tumor effects

Platelet-like particles (PLPs), derived from megakaryocytic cell lines MEG-01 and K-562, are widely used as a surrogate to study platelet formation and function. We demonstrate by RNA-Seq that PLPs are transcriptionally distinct from platelets. Expression of key genes in signaling pathways promoting platelet activation/aggregation, such as the PI3K/AKT, protein kinase A, phospholipase C, and α-adrenergic and GP6 receptor pathways, was missing or under-expressed in PLPs. Functionally, PLPs do not aggregate following epinephrine, collagen, or ADP stimulation. While PLPs aggregated in response to thrombin, they did not display enhanced expression of surface markers P-selectin and activated α_2bβ₃, in contrast to platelets. We have previously demonstrated that platelets physically couple to MDA-PCa-2b and RC77T/E prostate cancer (PCa) cells via specific ligand-receptor interactions, leading to platelet-stimulated cell invasiveness and apoptotic resistance, and reciprocal cell-induced platelet aggregation. In contrast, PLP interactions with PCa cells inhibited both cell invasion and apoptotic resistance while failing to promote PLP aggregation. Moreover, PLPs reduced platelet-PCa cell interactions and antagonized platelet-stimulated oncogenic effects in PCa cells. RNA-Seq analysis identified candidate ligand-transmembrane protein combinations involved in anti-tumorigenic signaling of PLPs to PCa cells. Antibody neutralization of the TIMP3-MMP15 and VEGFB-FGFR1 signaling axes reversed PLP-mediated anti-invasion and apoptotic sensitization, respectively. In summary, PLPs lack many transcriptomic, molecular and functional features of platelets and possess novel anti-tumorigenic properties. These findings indicate that PLPs may have a potential therapeutic role in targeting and disrupting the oncogenic signaling between platelets and cancer cells, offering a new avenue for anti-cancer strategies. <b>What is the context?</b>This study investigates the role of PLPs as substitutes for platelets in cancer biology, focusing on their ability to replicate platelet functions, particularly in stimulating cancer cell oncogenicity. Given the challenges of obtaining blood from volunteers in a timely manner and isolating a pure population of platelets, PLPs were explored as a potentially valuable alternative, though their biology as platelet surrogates remains untested. This study investigates the role of PLPs as substitutes for platelets in cancer biology, focusing on their ability to replicate platelet functions, particularly in stimulating cancer cell oncogenicity. Given the challenges of obtaining blood from volunteers in a timely manner and isolating a pure population of platelets, PLPs were explored as a potentially valuable alternative, though their biology as platelet surrogates remains untested. <b>What is new?</b>A comprehensive comparison of the transcriptome of PLPs compared to platelets.This research is the first to examine whether PLPs can communicate with cancer cells to promote oncogenicity and whether cancer cells can stimulate PLP aggregation. It provides novel insights into the potential of PLPs as a surrogate model in cancer studies. A comprehensive comparison of the transcriptome of PLPs compared to platelets. This research is the first to examine whether PLPs can communicate with cancer cells to promote oncogenicity and whether cancer cells can stimulate PLP aggregation. It provides novel insights into the potential of PLPs as a surrogate model in cancer studies. <b>What is the impact?</b>The study demonstrated that PLPs are transcriptionally distinct from platelets, lacking key genes in signaling pathways involved in platelet aggregation and cancer cell stimulation. Functionally, PLPs did not aggregate in response to agonists or cancer cells and instead exhibited anti-oncogenic effects on cancer cells. Moreover, PLPs functionally antagonized platelet-stimulated cancer cell oncogenicity. These findings suggest that PLPs could serve as a therapeutic tool to target and disrupt the oncogenic signaling between platelets and cancer cells. The study demonstrated that PLPs are transcriptionally distinct from platelets, lacking key genes in signaling pathways involved in platelet aggregation and cancer cell stimulation. Functionally, PLPs did not aggregate in response to agonists or cancer cells and instead exhibited anti-oncogenic effects on cancer cells. Moreover, PLPs functionally antagonized platelet-stimulated cancer cell oncogenicity. These findings suggest that PLPs could serve as a therapeutic tool to target and disrupt the oncogenic signaling between platelets and cancer cells.

源自巨核细胞系(megakaryocytic cell lines)MEG-01与K-562的血小板样颗粒(Platelet-like particles, PLPs)，常被用作研究血小板生成与功能的替代模型。本研究通过RNA测序(RNA-Seq)证实，PLPs在转录组层面与天然血小板存在显著差异。在调控血小板活化/聚集的信号通路关键基因表达上，PLPs存在缺失或低表达情况，这些通路包括PI3K/AKT通路、蛋白激酶A(protein kinase A)通路、磷脂酶C(phospholipase C)通路，以及α肾上腺素能受体(α-adrenergic)与GP6受体(GP6 receptor)通路。功能实验显示，PLPs在肾上腺素、胶原或二磷酸腺苷(ADP)刺激下无法发生聚集；尽管凝血酶刺激可诱导PLPs聚集，但与天然血小板不同的是，PLPs不会上调表面标志物P-选择素(P-selectin)与活化型α₂bβ₃(activated α₂bβ₃)的表达。
既往研究证实，血小板可通过特异性配体-受体相互作用，与MDA-PCa-2b及RC77T/E前列腺癌细胞(prostate cancer cells, PCa)发生物理结合，进而促进癌细胞侵袭能力与凋亡抵抗，并诱导癌细胞介导的血小板聚集。与之相反，PLPs与前列腺癌细胞的相互作用可同时抑制癌细胞侵袭与凋亡抵抗，且无法促进PLPs自身聚集。此外，PLPs可减少血小板与前列腺癌细胞的结合，并拮抗血小板对前列腺癌细胞的致癌刺激效应。RNA测序分析筛选出了参与PLPs向前列腺癌细胞传递抑癌信号的候选配体-跨膜蛋白组合。针对金属蛋白酶组织抑制剂3(TIMP3)-基质金属蛋白酶15(MMP15)与血管内皮生长因子B(VEGFB)-成纤维细胞生长因子受体1(FGFR1)信号轴的抗体中和实验，可分别逆转PLPs介导的抗侵袭效应与凋亡致敏效应。
综上，PLPs缺失天然血小板的诸多转录组、分子与功能特征，并具备全新的抑癌特性。上述结果表明，PLPs或可通过靶向并阻断血小板与癌细胞间的致癌信号通路发挥治疗作用，为抗癌策略提供了新的研究方向。
<b>研究背景</b>：本研究旨在探讨PLPs作为血小板替代模型在肿瘤生物学中的作用，重点考察其是否能够复刻血小板的相关功能，尤其是促进癌细胞致癌性的能力。鉴于临床中难以及时获取志愿者血液并分离得到高纯度血小板群体，PLPs被认为是极具应用价值的替代方案，但其作为血小板替代模型的生物学特性仍未得到充分验证。
<b>研究创新点</b>：本研究首次全面对比了PLPs与血小板的转录组差异；同时，本研究亦是首个探讨PLPs是否可与癌细胞相互作用以促进致癌性，以及癌细胞能否诱导PLPs聚集的相关研究，为PLPs作为肿瘤研究替代模型的潜力提供了全新的科学见解。
<b>研究意义</b>：本研究证实PLPs在转录组层面与血小板存在显著差异，缺失参与血小板聚集与癌细胞致癌刺激的关键信号通路基因。功能层面，PLPs无法在激动剂或癌细胞刺激下发生聚集，反而对癌细胞展现出抑癌效应；此外，PLPs可功能性拮抗血小板对癌细胞的致癌刺激作用。上述结果提示，PLPs可作为治疗工具，靶向并阻断血小板与癌细胞间的致癌信号通路，为抗癌治疗策略开辟了全新的研究路径。