Pezzuto Federica, Lunardi Francesca, Vedovelli Luca, Fortarezza Francesco, Urso Loredana, Grosso Federica, Ceresoli Giovanni Luca, Kern Izidor, Vlacic Gregor, Faccioli Eleonora, Schiavon Marco, Gregori Dario, Rea Federico, Pasello Giulia, Calabrese Fiorella
Department of Cardiac, Thoracic, Vascular Sciences and Public Health, University of Padova, Padova, Italy.
Department of Surgery, Oncology and Gastroenterology, University of Padova, Padova, Italy.
Front Oncol. 2021 Mar 22;11:653497. doi: 10.3389/fonc.2021.653497. eCollection 2021.
The CDKN2A gene plays a central role in the pathogenesis of malignant pleural mesothelioma (MPM). The gene encodes for two tumor suppressor proteins, p16/INK4A and p14/ARF, frequently lost in MPM tumors. The exact role of p14/ARF in MPM and overall its correlation with the immune microenvironment is unknown. We aimed to determine whether there is a relationship between p14/ARF expression, tumor morphological features, and the inflammatory tumor microenvironment.
Diagnostic biopsies from 76 chemo-naive MPMs were evaluated. Pathological assessments of histotype, necrosis, inflammation, grading, and mitosis were performed. We evaluated p14/ARF, PD-L1 (tumor proportion score, TPS), and Ki-67 (percentage) by immunohistochemistry. Inflammatory cell components (CD3+, CD4+, CD8+ T lymphocytes; CD20+ B-lymphocytes; CD68+ and CD163+ macrophages) were quantified as percentages of positive cells, distinguishing between intratumoral and peritumoral areas. The expression of p14/ARF was associated with several clinical and pathological characteristics. A random forest-based machine-learning algorithm (Boruta) was implemented to identify which variables were associated with p14/ARF expression.
p14/ARF was evaluated in 68 patients who had a sufficient number of tumor cells. Strong positivity was detected in 14 patients (21%) (11 epithelioid and 3 biphasic MPMs). At univariate analysis, p14/ARF-positive epithelioid mesotheliomas showed higher nuclear grade (G3) (p = 0.023) and higher PD-L1 expression (≥50%) (p = 0.042). The percentages of CD4 and CD163 in peritumoral areas were respectively higher and lower in p14/ARF positive tumors but did not reach statistical significance with our sample size (both p = 0.066). The Boruta algorithm confirmed the predictive value of PD-L1 percentage for p14/ARF expression in all histotypes.
p14/ARF-positive epithelioid mesotheliomas may mark a more aggressive pathological phenotype (higher nuclear grade and PD-L1 expression). Considering the results regarding the tumor immune microenvironment, p14/ARF-negative tumors seem to have an immune microenvironment less sensitive to immune checkpoint inhibitors, being associated with low PD-L1 and CD4 expression, and high CD163 percentage. The association between p14/ARF-positive MPMs and PD-L1 expression suggests a possible interaction of the two pathways. Confirmation of our preliminary results could be important for patient selection and recruitment in future clinical trials with anticancer immunotherapy.
CDKN2A基因在恶性胸膜间皮瘤（MPM）的发病机制中起核心作用。该基因编码两种肿瘤抑制蛋白，p16/INK4A和p14/ARF，在MPM肿瘤中经常缺失。p14/ARF在MPM中的确切作用及其与免疫微环境的整体相关性尚不清楚。我们旨在确定p14/ARF表达、肿瘤形态特征与炎性肿瘤微环境之间是否存在关联。
对76例未经化疗的MPM诊断活检标本进行评估。进行组织学类型、坏死、炎症、分级和有丝分裂的病理评估。我们通过免疫组织化学评估p14/ARF、PD-L1（肿瘤比例评分，TPS）和Ki-67（百分比）。炎性细胞成分（CD3 +、CD4 +、CD8 + T淋巴细胞；CD20 + B淋巴细胞；CD68 +和CD163 +巨噬细胞）以阳性细胞百分比进行定量，区分瘤内和瘤周区域。p14/ARF的表达与多种临床和病理特征相关。实施基于随机森林的机器学习算法（Boruta）以确定哪些变量与p14/ARF表达相关。
对68例有足够数量肿瘤细胞的患者评估了p14/ARF。在14例患者（21%）（11例上皮样和3例双相MPM）中检测到强阳性。单因素分析显示，p14/ARF阳性的上皮样间皮瘤显示出更高的核分级（G3）（p = 0.023）和更高的PD-L1表达（≥50%）（p = 0.042）。p14/ARF阳性肿瘤瘤周区域的CD4和CD163百分比分别较高和较低，但在我们的样本量下未达到统计学意义（p均 = 0.066）。Boruta算法证实了PD-L1百分比对所有组织学类型中p14/ARF表达的预测价值。
p14/ARF阳性的上皮样间皮瘤可能标志着一种更具侵袭性的病理表型（更高的核分级和PD-L1表达）。考虑到关于肿瘤免疫微环境的结果，p14/ARF阴性肿瘤似乎具有对免疫检查点抑制剂不太敏感的免疫微环境，与低PD-L1和CD4表达以及高CD163百分比相关。p14/ARF阳性MPM与PD-L1表达之间的关联表明这两条途径可能存在相互作用。证实我们的初步结果对于未来抗癌免疫治疗临床试验中的患者选择和招募可能很重要。
