Department of Pathology and Neuropathology, University Hospital Essen, University of Duisberg-Essen, Essen, Germany.
J Thorac Oncol. 2013 May;8(5):644-53. doi: 10.1097/JTO.0b013e318287c224.
Malignant mesothelioma is a highly aggressive tumor arising from mesothelial-lined surfaces, most often in the pleura cavities. Antifolates belong to the most effective cytotoxic drugs for malignant pleural mesothelioma (MPM) treatment. Pemetrexed is an antifolate inhibiting different folate pathway genes (thymidylate synthase [TS], dihydrofolate reductase, glycinamide ribonucleotide formyltransferase [GARFT], and aminoimidazole carboxamide ribonucleotide formyltransferase, [AICARFT]). Increased activity of pemetrexed occurs by folylpolyglutamate synthetase (FPGS), intracellular transport by reduced folate carrier (RFC). The aim of the study was to explore potential correlations between TS, GARFT, AICARFT, RFC, and FPGS levels in MPM and associations with clinical benefit from pemetrexed treatment.
Samples from 63 patients were tested using immunohistochemistry (IHC) and quantitative polymerase chain reaction(qPCR) for expression levels of TS, GARFT, AICARFT, RFC, and FPGS. Clinical data were evaluated to determine associations between efficacy of pemetrexed and enzyme expression levels. Evaluation of expression levels was done through TaqMan-based qPCR, and IHC was evaluated semiquantitatively by using the H-score.
qPCR analysis showed no difference in expression pattern of GARFT and AICARFT. IHC analysis revealed a heterogeneous staining pattern for all the enzymes. No significant association was found between TS expression and survival or objective response of the tumors after pemetrexed treatment. FPGS (p = 0.0111) and RFC (p = 0.0088) mRNA expression levels were strongly associated with overall survival in these patients.
Our results reveal that in pemetrexed-treated MPMs TS expression levels have no influence on patient outcome. Furthermore, GARFT and AICARFT were homogeneously expressed in the patient samples. Folate uptake mechanisms by RFC and activation by FPGS were associated with clinical benefit from pemetrexed treatment.
恶性间皮瘤是一种源自间皮衬里表面的高度侵袭性肿瘤，最常见于胸膜腔。叶酸拮抗剂属于治疗恶性胸膜间皮瘤（MPM）最有效的细胞毒性药物。培美曲塞是一种叶酸拮抗剂，可抑制不同的叶酸途径基因（胸苷酸合成酶[TS]、二氢叶酸还原酶、甘氨酰胺核苷酸 formyltransferase [GARFT]和氨基咪唑羧酰胺核苷酸 formyltransferase [AICARFT]）。培美曲塞的活性增加是由叶酸多聚谷氨酸合成酶（FPGS）引起的，通过还原叶酸载体（RFC）进行细胞内转运。本研究旨在探讨 MPM 中 TS、GARFT、AICARFT、RFC 和 FPGS 水平与临床获益之间的潜在相关性。
使用免疫组织化学（IHC）和定量聚合酶链反应（qPCR）检测 63 例患者的 TS、GARFT、AICARFT、RFC 和 FPGS 表达水平。评估临床数据以确定培美曲塞疗效与酶表达水平之间的关联。通过 TaqMan 定量 PCR 评估表达水平，通过 H 评分半定量评估 IHC。
qPCR 分析显示 GARFT 和 AICARFT 的表达模式无差异。免疫组织化学分析显示所有酶的染色模式均存在异质性。TS 表达与培美曲塞治疗后肿瘤的生存或客观反应之间未发现显著关联。在这些患者中，FPGS（p = 0.0111）和 RFC（p = 0.0088）mRNA 表达水平与总生存期强烈相关。
我们的结果表明，在培美曲塞治疗的 MPM 中，TS 表达水平对患者预后没有影响。此外，GARFT 和 AICARFT 在患者样本中均匀表达。RFC 摄取叶酸的机制和 FPGS 的激活与培美曲塞治疗的临床获益相关。
