Chemotherapeutic response assessment in cancer cells using a microcavity array-based bioreactor system and sodium triple-quantum MR signal

细胞内低钠浓度对细胞活力至关重要。化疗反应表现为诱导细胞凋亡，从而使细胞内钠、钾离子浓度反转，随后形成凋亡小体。钠磁共振(MR)作为一种非侵入性技术，可作为早期治疗反应评估的潜在生物标志物。钠离子与蛋白质的相互作用产生了一种独特的细胞内敏感的三量子(TQ)信号。这种TQ信号与灌流心脏中的细胞内钠浓度呈线性相关，因此代表了量化细胞反应的一个吸引人的特征。TQ信号与生物反应器系统的结合，使我们能够在两次Na/K-ATPase抑制期间监测癌细胞细胞内钠浓度的变化。因此，由于其独特的细胞内敏感性和细胞内钠离子变化在细胞凋亡过程中的重要性，我们建议将钠离子TQ信号作为早期治疗反应评估的生物标志物。为了确定这一点，我们将使用改进的钠TQ信号和生物反应器系统来监测器官型3D细胞培养的化疗治疗。我们提出的固定TQ时间比例相位增量(TQTPPI)脉冲序列的进一步改进将使我们能够以尽可能高的TQ信噪比进行定量和快速的TQ测量。因此，我们将结合非相干欠采样技术来评估一种新的TQTPPI数据重建技术。将已建立的生物反应器系统扩展到测定细胞内钠离子浓度的方法，将加深我们对化疗过程中细胞水平上的TQ信号变化的理解。此外，我们将验证在不同的Na/K-ATPase抑制期间TQ信号与细胞内钠浓度的线性相关性，以利用TQ信号来量化化疗期间的细胞反应。最后，我们将使用改进的TQ信号和生物反应器系统来监测具有良好特性的大鼠9L胶质肉瘤细胞系对1，3-二(2-氯乙基)-1-亚硝脲(BCNU)治疗的化疗反应。BCNU处理大鼠9L细胞对细胞内钠离子浓度和单量子磁共振信号的影响是众所周知的。因此，TQ信号可作为早期治疗反应评估的生物标志物。此外，大鼠9L细胞系和BCNU的处理将使我们能够在未来的研究中利用TQ信号来研究低细胞内钠浓度对化疗耐药性的至关重要的作用。我们工作的长期目标是建立TQ信号和生物反应器系统的组合，作为以翻译方法开发抗癌药物的新工具。

A low intracellular sodium concentration is of vital importance for cell viability. Chemotherapeutic response manifests itself in the induction of apoptosis and, thus, in the ionic reversal of intracellular sodium and potassium concentrations followed by apoptotic body formation. Sodium magnetic resonance (MR) as a non-invasive technique can be a potential biomarker for early treatment response assessment. Interactions of sodium ions with proteins create a unique intracellular sensitive triple-quantum (TQ) signal. This TQ signal correlated linearly with the intracellular sodium concentration in perfused hearts and, hence, represents an attractive feature to quantify cellular responses. The combination of TQ signal and bioreactor system featuring an organotypic 3D cell culture in a finely controllable environment allowed us to monitor changes in the intracellular sodium concentration of cancer cells during two Na/K-ATPase inhibitions. Therefore, we propose the sodium TQ signal as a biomarker for early treatment response assessment due to its unique intracellular sensitivity and the importance of intracellular sodium changes during apoptosis. To establish this, we will monitor the chemotherapeutic treatment of organotypic 3D cell cultures using an improved setup of sodium TQ signal and bioreactor system. Further improvements of our proposed fixed TQ time proportional phase incrementation (TQTPPI) pulse sequence will enable us quantitative and fast TQ measurements with the highest possible TQ signal-to-noise ratio. Therefore, we will evaluate a novel reconstruction technique of TQTPPI data combined with incoherent undersampling techniques. Extension of the established bioreactor system by a method for the determination of the intracellular sodium concentration per cell will deepen our understanding of TQ signal changes on a cellular level during chemotherapeutic treatment. In addition, we will verify the linear correlation of TQ signal with intracellular sodium concentration during various Na/K-ATPase inhibitions to quantify cellular responses during chemotherapeutic treatment using the TQ signal. Finally, we will monitor the chemotherapeutic response of the well-characterized rat 9L gliosarcoma cell line to 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) treatment using the improved setup of the TQ signal and bioreactor system. The effects of BCNU treatment of rat 9L cells on intracellular sodium concentration and single-quantum MR signal are well known. Hence, the TQ signal can be established as a biomarker for early treatment response assessment. Furthermore, the rat 9L cell line and BCNU treatment will allow us in future studies to investigate the vital importance of a low intracellular sodium concentration on chemotherapeutic resistance using TQ signal. The long-term goal of our work is to establish the combination of TQ signal and bioreactor system as a novel tool for anticancer drug development in a translational approach.