Nano-Inspired Biomedicine Lab, Fondazione Istituto di Ricerca Pediatrica Città della Speranza, Padova, 35127, Italy.
First Surgical Clinic Section, Department of Surgical, Oncological and Gastroenterological Sciences, University of Padua, Padua, Italy.
J Mass Spectrom. 2021 Jan;56(1):e4682. doi: 10.1002/jms.4682. Epub 2020 Dec 2.
5-Fluorouracil (5FU) is a widely employed antineoplastic agent that acts as antimetabolite. However, 5FU activity is strongly reduced against a subset of cancer cells called cancer stem cells (CSCs), which are believed to be responsible for chemoresistance and tumour recurrence. It was found that epigallocatechin-3-gallate (EGCG), the most abundant catechin present in green tea extract, suppresses CSCs grown in various cancers. This chemosensitizing effect of EGCG was investigated in 5FU-resistant (5FUR) CRC cells, showing that EGCG enhances 5FU-induced cytotoxicity. However, the real mechanism of an improved 5FU chemosensitivity in the presence of EGCG was not evaluated. Considering the capability of catechins to form bimolecular noncovalent complexes, in the present study, the interaction of catechins and 5FU was studied by different mass spectrometric approaches. The ESI(+) and ESI(-) spectra of [5FU-catechin] mixtures were studied, showing the formation of protonated and deprotonated bimolecular complexes, whose nature was confirmed by MS/MS experiments (product and precursor ion scans). To exclude the possible origin of these species as ESI artefacts, a further series of experiments were performed by high-resolution liquid chromatography-mass spectrometry. By this approach, bimolecular complexes have been detected at retention times different from those of free 5FU and catechins, proving their presence in the original solution. Analogous studies were performed on 5FU-green tea extract mixtures, showing that 5FU leads to complexes not only with EGCG but also with other catechins. These molecular species, differently to free 5FU drug alone, would in principle possess a new biological activity and could be an explanation of the described activity cited above.
5-氟尿嘧啶（5FU）是一种广泛应用的抗肿瘤药物，作为抗代谢物发挥作用。然而，5FU 的活性在称为癌症干细胞（CSC）的一小部分癌细胞中大大降低，CSC 被认为是导致化疗耐药和肿瘤复发的原因。研究发现，绿茶提取物中含量最丰富的儿茶素表没食子儿茶素没食子酸酯（EGCG）可抑制多种癌症中 CSC 的生长。研究了 EGCG 对 5FU 耐药（5FUR）CRC 细胞中 CSC 的化学增敏作用，结果表明 EGCG 增强了 5FU 诱导的细胞毒性。然而，在 EGCG 存在的情况下提高 5FU 化疗敏感性的真正机制尚未得到评估。考虑到儿茶素形成双分子非共价复合物的能力，本研究采用不同的质谱方法研究了儿茶素与 5FU 的相互作用。研究了[5FU-儿茶素]混合物的 ESI(+)和 ESI(-)光谱，显示形成了质子化和去质子化的双分子复合物，通过 MS/MS 实验（产物和前体离子扫描）证实了其性质。为了排除这些物质作为 ESI 伪影的可能来源，还进行了一系列高分辨液相色谱-质谱实验。通过这种方法，在与游离 5FU 和儿茶素不同的保留时间检测到双分子复合物，证明它们存在于原始溶液中。对 5FU-绿茶提取物混合物进行了类似的研究，结果表明 5FU 不仅与 EGCG 形成复合物，还与其他儿茶素形成复合物。与单独的游离 5FU 药物不同，这些分子物种原则上具有新的生物学活性，并且可以解释上述描述的活性。
