RESUMO
Hyperpolarized 129Xe (HP 129Xe) MRI enables functional imaging of various lung diseases but has been scarcely applied to lung cancer imaging. The aim of this study is to investigate the feasibility of targeted imaging of lung cancer with HP 129Xe MRI using surface-modified iron oxide nanoparticles (IONPs) as molecular targeting contrast agents. A mouse model of lung cancer (LC) was induced in nine mice by intra-peritoneal injection of urethane. Three months after the urethane administration, the mice underwent lung imaging with HP 129Xe MRI at baseline (0 h). Subsequently, the LC group was divided into two sub-groups: mice administered with polyethylene glycol-coated IONPs (PEG-IONPs, n = 4) and folate-conjugated dextran-coated IONPs (FA@Dex-IONPs, n = 5). The mice were imaged at 3, 6, and 24 h after the intravenous injection of IONPs. FA@Dex-IONPs mice showed a 25% reduction in average signal intensity at cancer sites at 3 h post injection, and a 24% reduction at 24 h post injection. On the other hand, in PEG-IONPs mice, while a signal reduction of approximately 28% was observed at cancer sites at 3 to 6 h post injection, the signal intensity was unchanged from that of the baseline at 24 h. Proton MRI of LC mice (n = 3) was able to detect cancer five months after urethane administration, i.e., later than HP 129Xe MRI (3 months). Furthermore, a significant decrease in averaged 1H T2 values at cancer sites was observed at only 6 h post injection of FA@Dex-IONPs (p < 0.05). As such, the targeted delivery of IONPs to cancer tissue was successfully imaged with HP 129Xe MRI, and their surface modification with folate likely has a high affinity with LC, which causes overexpression of folate receptors.
RESUMO
This study aimed to assess the suitability of hyperpolarized 129Xe (HPXe) MRI for noninvasive longitudinal evaluation of pulmonary function in preclinical lung cancer models. A mouse model of lung cancer (LC) was induced in 5 mice by intraperitoneal injection of urethane, while a negative-control (NC) mice (N = 5) was prepared by injection of saline solution. Longitudinal HPXe MRI was performed over a 5-month period to monitor lung ventilation and gas exchange. The treatment efficacy of ethyl pyruvate (EP), an anti-inflammatory drug, to the mouse LC model was monitored using HPXe MRI by commencing administration of EP pre (early-phase) and 1-month post (late-phase) injection of urethane (N = 5 mice for each group). Gas-exchange function in LC mice was significantly reduced at 1-month after urethane injection compared with NC mice administered with saline (P < 0.01). Thereafter, it remained consistently lower than that of the NC group for the full 5-month measurement period. In contrast, the ventilation function of the LC model mice was not significantly different to that of the NC mice. Histological analysis revealed alveolar epithelial hyperplasia in LC mice alveoli at 1 month after urethane injection, and adenoma was confirmed 3 months after the injection. The early- and late-phase EP interventions were found to improve HPXe MRI metrics (reduced at 1 month postinjection of urethane) and significantly inhibit tumor growth. These results suggest that HPXe MRI gas-exchange metrics can be used to quantitatively assess changes in the precancerous lesion microenvironment and to evaluate therapeutic efficacy in cancer. Thus, HPXe MRI can be utilized to noninvasively monitor pulmonary pathology during LC progression and can visualize functional changes during therapy.
