Chesnokov Mikhail S, Khesina Polina A, Shavochkina Darya A, Kustova Inna F, Dyakov Leonid M, Morozova Olga V, Mugue Nikolai S, Kudashkin Nikolay E, Moroz Ekaterina A, Patyutko Yuri I, Lazarevich Natalia L
Institute of Carcinogenesis, FSBI "N.N. Blokhin National Medical Research Center of Oncology" of the Ministry of Health of the Russian Federation, Moscow, Russian Federation.
Biological Faculty, M.V. Lomonosov Moscow State University, Moscow, Russian Federation.
PeerJ. 2018 Jun 5;6:e4915. doi: 10.7717/peerj.4915. eCollection 2018.
Hepatocellular carcinoma (HCC) is the most common and aggressive type of malignant liver tumor. HCC progression depends significantly on its vascularization and formation of new blood vessels. Vascular endothelial growth factor A (VEGFA) is a crucial regulator of tumor vascularization and components of VEGF-induced cell signaling pathways are important targets of therapeutical drugs that demonstrated the highest efficiency in case of advanced HCC (sorafenib and regorafenib). VEGFA is expressed as a set of isoforms with different functional properties, thus VEGFA isoform expression pattern may affect tumor sensitivity to anti-angiogenic drugs. However, information about VEGFA isoforms expression in HCC is still incomplete and contradictory. The present study aims to quantitatively investigate VEGFA isoform expression aberrations in HCC tissue.
A total of 50 pairs of HCC and non-tumor tissue samples were used to evaluate the VEGFA isoform spectrum using RT-PCR and quantitatively estimate changes in isoform expression using RT-qPCR. Correlations between these changes and tumor clinicopathological characteristics were analyzed.
We identified VEGFA-189, VEGFA-165, and VEGFA-121 as predominant isoforms in liver tissue. Anti-angiogenic VEGFA-xxxb variants constituted no more than 5% of all mature VEGFA transcripts detected and their expression was not changed significantly in HCC tissue. We demonstrated for the first time that the least active variant VEGFA-189 is frequently repressed in HCC ( < 0.001), while no uniform changes were detected for potent angiogenesis stimulators VEGFA-165 and VEGFA-121. Isoform balance in HCC shifts from VEGFA-189 towards VEGFA-165 or VEGFA-121 in the majority of cases ( < 0.001). Changes in fractions, but not expression levels, of VEGFA-189 (decrease) and VEGFA-121 (increase) correlated with advanced Tumor-Node-Metastasis (TNM) and Barcelona Clinic Liver Cancer (BCLC) tumor stages ( < 0.05), VEGFA-189 fraction reduction was also associated with poor tumor differentiation ( < 0.05).
A distinct shift in VEGFA isoform balance towards more pro-angiogenic variants occurs in HCC tissue and may modulate overall impact of VEGFA signaling. We suppose that the ratio between VEGFA isoforms is an important parameter governing HCC angiogenesis that may affect HCC progression and be used for optimizing the strategy of HCC therapy by predicting the response to anti-angiogenic drugs.
肝细胞癌（HCC）是最常见且侵袭性最强的恶性肝肿瘤类型。HCC的进展在很大程度上取决于其血管生成和新血管的形成。血管内皮生长因子A（VEGFA）是肿瘤血管生成的关键调节因子，VEGF诱导的细胞信号通路的组成部分是治疗药物的重要靶点，这些药物在晚期HCC（索拉非尼和瑞戈非尼）治疗中显示出最高的疗效。VEGFA以一组具有不同功能特性的异构体形式表达，因此VEGFA异构体的表达模式可能会影响肿瘤对抗血管生成药物的敏感性。然而，关于HCC中VEGFA异构体表达的信息仍然不完整且相互矛盾。本研究旨在定量研究HCC组织中VEGFA异构体表达异常情况。
共使用50对HCC和非肿瘤组织样本，通过逆转录聚合酶链反应（RT-PCR）评估VEGFA异构体谱，并通过逆转录定量聚合酶链反应（RT-qPCR）定量估计异构体表达的变化。分析这些变化与肿瘤临床病理特征之间的相关性。
我们确定VEGFA-189、VEGFA-165和VEGFA-121是肝组织中的主要异构体。抗血管生成的VEGFA-xxxb变体在所有检测到的成熟VEGFA转录本中占比不超过5%，且其在HCC组织中的表达无显著变化。我们首次证明，活性最低的变体VEGFA-189在HCC中经常受到抑制（<0.001），而强效血管生成刺激剂VEGFA-165和VEGFA-121未检测到一致的变化。在大多数情况下（<0.001），HCC中的异构体平衡从VEGFA-189向VEGFA-165或VEGFA-121转移。VEGFA-189（降低）和VEGFA-121（升高）的比例变化而非表达水平变化与晚期肿瘤-淋巴结-转移（TNM）和巴塞罗那临床肝癌（BCLC）肿瘤分期相关（<0.05），VEGFA-189比例降低也与肿瘤低分化相关（<0.05）。
HCC组织中VEGFA异构体平衡明显向促血管生成变体转移，这可能会调节VEGFA信号的整体影响。我们推测VEGFA异构体之间的比例是控制HCC血管生成的一个重要参数，可能影响HCC的进展，并可用于通过预测对抗血管生成药物的反应来优化HCC治疗策略。
