Overhauser Enhanced Magnetic Resonance Imaging (OMRI)

代谢核磁共振对HSP70抑制剂JG-98的评价：雄激素受体是前列腺癌的关键调节因子，也是目前前列腺癌治疗的主要靶点，统称为雄激素剥夺疗法。对这些药物不敏感是进展到称为去势抵抗前列腺癌的晚期疾病状态的标志。因此，迫切需要新的治疗方案来减缓去势耐受前列腺癌的进展，并有效地与现有药物相结合。我们发现，HSP70的变构抑制剂JG-98通过靶向线粒体HSP70(HSPA9)抑制有氧呼吸，使去势抵抗的前列腺癌对雄激素剥夺药物重新敏感。JG-98‘S的主要作用不是像前面描述的那样影响雄激素受体的稳定性，而是抑制线粒体的翻译，导致电子传输链活性的中断，如超极化133C标记丙酮酸的13C磁共振显示的那样。尽管HSPA9抑制在功能上与HSPA9抑制不同，但用复合I或II抑制剂直接抑制电子传输链会产生类似的生理状态，能够使去势抵抗的前列腺癌对雄激素剥夺疗法重新敏感。这些数据确定了HspA9在线粒体核糖体功能中的重要作用，并强调了去势抵抗前列腺癌的可操作代谢脆弱性。α-酮戊二酸是一种关键的生物分子，参与了许多代谢途径的水平线，尤其是TCA循环。α-酮戊二酸代谢异常也与癌症有关。在这里，利用同位素标记合成了[1-(13)C，5-(12)C，D(4)]α-酮戊二酸，以期利用其[1-(13)C]-超极化状态在体内对α-酮戊二酸分析物及其下游代谢物进行实时代谢成像。通过屏蔽层中的可逆交换进行信号放大，使排列转移到异核(剑鞘)。采用超极化技术，在1分钟内产生9.7%[1-(13)C]极化。利用对氢作为核自旋有序源的(13)C超极化也得到了在0.4mut场(最佳极化转移场)下的有利驰豫动力学的支持：指数(13)C极化建立常数T(B)为11.0+/-0.4 S，而(13)C极化衰减常数T(1)为18.5+/-0.7 S。用天然丰度的α-酮戊二酸二钠获得了更高的(13)C极化值17.3%，在0.4mut场下的驰豫动力学总体上与之相似。这表明，衬底氚只导致被三个化学键隔开的(13)C核的驰豫速率略有增加(约1.2倍)。相反，极化(自然丰度与[1-(13)C]标记)的增益是通过包含可用(13)C自旋的较小热容量来合理化的，这些自旋必须通过每个样品中存在的相同数量的仲氢超极化，这与之前的(15)N军刀鞘研究一致。值得注意的是，在所研究的两种α-酮戊二酸同位素制剂中，C-2碳没有超极化；这一观察结果与先前报道的刀鞘丙酮酸研究形成了鲜明对比，表明在α-酮戊二酸和丙酮酸中，C-2的催化剂结合动力学不同。我们还证明，α-酮戊二酸和丙酮酸分析物的(13)C光谱表征可以在自然的(13)C丰度下进行，估计检测下限为80微摩尔浓度x*%P(13C)。总而言之，这里报道的基础研究使广泛的研究团体能够使用一种新的超极化造影剂，这种造影剂可能用于脑功能、癌症和其他代谢挑战疾病的代谢成像

Evaluation of JG-98, inhibitor of HSP70 by metabolic MRI: The androgen receptor is a key regulator of prostate cancer and the principal target of current prostate cancer therapies collectively termed androgen deprivation therapies. Insensitivity to these drugs is a hallmark of progression to a terminal disease state termed castration-resistant prostate cancer. Therefore, novel therapeutic options that slow progression of castration-resistant prostate cancer and combine effectively with existing agents are in urgent need. We show that JG-98, an allosteric inhibitor of HSP70, re-sensitizes castration-resistant prostate cancer to androgen deprivation drugs by targeting mitochondrial HSP70 (HSPA9) to suppress aerobic respiration. Rather than impacting androgen receptor stability as previously described, JG-98's primary effect is inhibition of mitochondrial translation, leading to disruption of electron transport chain activity as shown by 13C MRI using hyperpolarized 133C labeled pyruvate. Although functionally distinct from HSPA9 inhibition, direct inhibition of the electron transport chain with a complex I or II inhibitor creates a similar physiological state capable of re-sensitizing castration-resistant prostate cancer to androgen deprivation therapies. These data identify a significant role for HspA9 in mitochondrial ribosome function and highlight an actionable metabolic vulnerability of castration-resistant prostate cancer. a-Ketoglutarate is a key biomolecule involved in a number of metabolic pathways horizontal line most notably the TCA cycle. Abnormal alpha-ketoglutarate metabolism has also been linked with cancer. Here, isotopic labeling was employed to synthesize [1-(13)C,5-(12)C,D(4)]alpha-ketoglutarate with the future goal of utilizing its [1-(13)C]-hyperpolarized state for real-time metabolic imaging of alpha-ketoglutarate analytes and its downstream metabolites in vivo. The signal amplification by reversible exchange in shield enables alignment transfer to heteronuclei (SABRE-SHEATH) hyperpolarization technique was used to create 9.7% [1-(13)C] polarization in 1 minute in this isotopologue. The efficient (13)C hyperpolarization, which utilizes parahydrogen as the source of nuclear spin order, is also supported by favorable relaxation dynamics at 0.4 muT field (the optimal polarization transfer field): the exponential (13)C polarization buildup constant T(b) is 11.0 +/- 0.4 s whereas the (13)C polarization decay constant T(1) is 18.5 +/- 0.7 s. An even higher (13)C polarization value of 17.3% was achieved using natural-abundance alpha-ketoglutarate disodium salt, with overall similar relaxation dynamics at 0.4 muT field, indicating that substrate deuteration leads only to a slight increase ( approximately 1.2-fold) in the relaxation rates for (13)C nuclei separated by three chemical bonds. Instead, the gain in polarization (natural abundance versus [1-(13)C]-labeled) is rationalized through the smaller heat capacity of the "spin bath" comprising available (13)C spins that must be hyperpolarized by the same number of parahydrogen present in each sample, in line with previous (15)N SABRE-SHEATH studies. Remarkably, the C-2 carbon was not hyperpolarized in both alpha-ketoglutarate isotopologues studied; this observation is in sharp contrast with previously reported SABRE-SHEATH pyruvate studies, indicating that the catalyst-binding dynamics of C-2 in alpha-ketoglutarate differ from that in pyruvate. We also demonstrate that (13)C spectroscopic characterization of alpha-ketoglutarate and pyruvate analytes can be performed at natural (13)C abundance with an estimated detection limit of 80 micromolar concentration x *%P(13C). All in all, the fundamental studies reported here enable a wide range of research communities with a new hyperpolarized contrast agent potentially useful for metabolic imaging of brain function, cancer, and other metabolically challenging diseases