Logozzi Mariantonia, Angelini Daniela F, Iessi Elisabetta, Mizzoni Davide, Di Raimo Rossella, Federici Cristina, Lugini Luana, Borsellino Giovanna, Gentilucci Alessandro, Pierella Federico, Marzio Vittorio, Sciarra Alessandro, Battistini Luca, Fais Stefano
Department of Oncology and Molecular Medicine, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy.
Neuroimmunology Unit, IRCCS Santa Lucia Foundation, 00179 Rome, Italy.
Cancer Lett. 2017 Sep 10;403:318-329. doi: 10.1016/j.canlet.2017.06.036. Epub 2017 Jul 8.
Prostate specific antigen (PSA) test is the most common, clinically validated test for the diagnosis of prostate cancer (PCa). While neoplastic lesions of the prostate may cause aberrant levels of PSA in the blood, the quantitation of free or complexed PSA poorly discriminates cancer patients from those developing benign lesions, often leading to invasive and unnecessary surgical procedures. Microenvironmental acidity increases exosome release by cancer cells. In this study we evaluated whether acidity, a critical phenotype of malignancy, could influence exosome release and increase the PSA expression in nanovesicles released by PCa cells. To this aim, we exploited Nanoparticle Tracking Analysis (NTA), an immunocapture-based ELISA, and nanoscale flow-cytometry. The results show that microenvironmental acidity induces an increased release of nanovesicles expressing both PSA and the exosome marker CD81. In order to verify whether the changes induced by the local selective pressure of extracellular acidity may correspond to a clinical pathway we used the same approach to evaluate the levels of PSA-expressing exosomes in the plasma of PCa patients and controls, including subjects with benign prostatic hypertrophy (BPH). The results show that only PCa patients have high levels of nanovesicles expressing both CD81 and PSA. This study shows that tumor acidity exerts a selective pressure leading to the release of extracellular vesicles that express both PSA and exosome markers. A comparable scenario was shown in the plasma of prostate cancer patients as compared to both BPH and healthy controls. These results suggest that microenvironmental acidity may represent a key factor which determines qualitatively and quantitatively the release of extracellular vesicles by malignant tumors, including prostate cancer. This condition leads to the spill-over of nanovesicles into the peripheral blood of prostate cancer patients, where the levels of tumor biomarkers expressed by exosomes, such as PSA-exosomes, may represent a novel, non-invasive clinical tool for the screening and early diagnosis of prostate cancer.
前列腺特异性抗原（PSA）检测是诊断前列腺癌（PCa）最常用且经过临床验证的检测方法。虽然前列腺的肿瘤性病变可能导致血液中PSA水平异常，但游离或复合PSA的定量检测难以区分癌症患者与发生良性病变的患者，这常常导致侵入性且不必要的外科手术。微环境酸度会增加癌细胞释放外泌体。在本研究中，我们评估了酸度这种恶性肿瘤的关键表型是否会影响外泌体释放，并增加PCa细胞释放的纳米囊泡中PSA的表达。为此，我们采用了纳米颗粒跟踪分析（NTA）、基于免疫捕获的ELISA和纳米级流式细胞术。结果表明，微环境酸度会诱导表达PSA和外泌体标志物CD81的纳米囊泡释放增加。为了验证细胞外酸度的局部选择性压力所诱导的变化是否对应一种临床途径，我们采用相同方法评估了PCa患者和对照组（包括良性前列腺增生症（BPH）患者）血浆中表达PSA的外泌体水平。结果表明，只有PCa患者有高水平表达CD81和PSA的纳米囊泡。本研究表明，肿瘤酸度施加了一种选择性压力，导致释放同时表达PSA和外泌体标志物的细胞外囊泡。与BPH患者和健康对照组相比，前列腺癌患者血浆中也呈现出类似情况。这些结果表明，微环境酸度可能是定性和定量决定包括前列腺癌在内的恶性肿瘤释放细胞外囊泡的关键因素。这种情况导致纳米囊泡溢出到前列腺癌患者的外周血中，其中外泌体所表达的肿瘤生物标志物（如PSA-外泌体）的水平可能代表一种用于前列腺癌筛查和早期诊断的新型非侵入性临床工具。
