NMR detection of tumor differentiation

描述(由申请人提供)：NCI在癌症治疗领域建立的最重要的目标之一是将癌症从一种急性和致命的疾病转变为一种可以长期控制的慢性疾病。实现这一目标需要两个条件：1)开发新的抗癌药物和利用这些药物的治疗方案，以及2)准确和非侵入性地评估这些治疗方案的有效性。分化药物在这一癌症治疗领域是一个有吸引力的可能性，因为它们既可以导致恶性表型的逆转，也可以触发细胞凋亡。我们在这个项目中的目标是阐明苯乙酸酯(PA)和苯丁酸酯(PB)这两种目前处于第二阶段临床试验的分化药物抑制癌细胞增殖的机制。我们将集中于利用体内磁共振波谱(MRS)观察到的磷脂酰胆碱(PtdCho)代谢产物的变化，目的是确定能够可靠地作为PA和PB抑制增殖和诱导凋亡的指标的光谱指标。这可能为临床监测1H-MRS对分化治疗的反应提供基础。体内动物肿瘤研究将与灌流细胞的机制研究相结合，使用荧光显微镜、流式细胞仪和分子生物学技术的磁共振光谱来确定与分化治疗相关的PtdCho分解代谢的关键检查点。我们的初步研究表明，PA和PB引起MR可见磷脂代谢产物水平的变化，这与诱导相关 对细胞凋亡的影响。使用荧光磷脂酶激活的磷脂类似物，我们已经在前列腺癌细胞中鉴定出两种不同的磷脂酶活性：一种是结构性的，主要是核的；另一种是细胞质的，可以被PA或PB诱导。因此，这项应用的目的是：i)测量体外和体内由分化剂诱导的磷脂酶活性；ii)确定导致PBI诱导的细胞凋亡光谱变化的磷脂酶亚型；iii)检测磷脂酶抑制对肿瘤细胞凋亡过程中MR可见代谢物的影响；以及iv)研究MR可见共振作为小鼠肿瘤模型分化治疗反应的标记的可能性。这些研究为分化治疗诱导磷脂代谢的改变提供了机制基础，从而在理解胆碱代谢方面取得了重要进展，有助于解释体内肿瘤的磁共振波谱。

DESCRIPTION (provided by applicant): One of the most important goals that NCI has established in the area of cancer treatment has been for the conversion of cancer from an acute and lethal disease to a chronic condition that can be managed long term. Two requirements are needed to achieve this goal: 1) the development of new anticancer drugs and treatment regimens utilizing these drugs, and 2) the ability to accurately and non-invasively assess the effectiveness of these treatment regimens. Differentiating agents are an attractive possibility in this area of cancer treatment, for they are agents that can either cause reversion of the malignant phenotype or the triggering of apoptosis. Our goal in this project is to delineate the mechanisms by which phenylacetate (PA) and phenylbutyrate (PB), two differentiating agents currently under Phase II clinical trials, inhibit the proliferation of cancer cells. We will concentrate on the changes in phosphatidylcholine (PtdCho) metabolites that can be observed using in vivo magnetic resonance spectroscopy (MRS) with the goal of determining the spectroscopic indicators that can reliably be used as an index for the inhibition of proliferation and induction of apoptosis by PA and PB. This could provide a basis for clinical monitoring of response to differentiation therapy by 1H MRS. In vivo animal tumor studies will be combined with mechanistic studies on perfused cells, using MR spectroscopy with fluorescence microscopy, flow cytometry and molecular biology techniques to identify key checkpoints in PtdCho catabolism associated with differentiation therapy. Our preliminary studies indicate that PA and PB induce changes in MR-visible phospholipid metabolite levels that correlate with the induction of apoptosis. Using fluorescent phospholipase-activated phospholipid analogues, we have identified two different phospholipase activities in prostate cancer cells: one that is constitutive and primarily nuclear, and one that is cytoplasmic and inducible by PA or PB. Thus, the aims of this application are to i) measure in vitro and in vivo phospholipase activation induced by differentiating agents, ii) identify the phospholipase isoform contributing to spectral changes in PBinduced apoptosis; iii) examine the effects of phospholipase inhibition on the MR-visible metabolites in tumor cells undergoing apoptosis and iv) to investigate the potential of MR-visible resonances as a marker for response to differentiation therapy in murine tumor models. These studies provide a mechanistic underpinning for the changes induced in phospholipid metabolism by differentiation therapy and therefore constitute an important advance in the understanding of choline metabolism for the interpretation of in vivo MR spectra of tumors.