Thim E Andrew, Fox Todd, Deering Tye, Vass Luke R, Sheybani Natasha D, Kester Mark, Price Richard J
Department of Biomedical Engineering, University of Virginia, Charlottesville, VA 22908.
Department of Pharmacology, University of Virginia, Charlottesville, VA 22908.
bioRxiv. 2023 Mar 23:2023.03.23.532394. doi: 10.1101/2023.03.23.532394.
Sparse scan partial thermal ablation (TA) with focused ultrasound (FUS) may be deployed to treat solid tumors and increase delivery of systemically administered therapeutics. Further, C6-ceramide-loaded nanoliposomes (CNLs), which rely upon the enhanced permeation and retention (EPR) effect for delivery, have shown promise for treating solid tumors and are being tested in clinical trials. Here, our objective was to determine whether CNLs synergize with TA in the control of 4T1 breast tumors. CNL-monotherapy of 4T1 tumors yielded significant intratumoral bioactive C6 accumulation by the EPR effect, but tumor growth was not controlled. TA increased bioactive C6 accumulation by ∼12.5-fold over the EPR effect. In addition, TA+CNL caused shifts in long-chain to very-long-chain ceramide ratios (i.e., C16/24 and C18/C24) that could potentially contribute to tumor control. Nonetheless, these changes in intratumoral ceramide levels were still insufficient to confer tumor growth control beyond that achieved when combining with TA with control "ghost" nanoliposomes (GNL). While this lack of synergy could be due to increased "pro-tumor" sphingosine-1-phosphate (S1P) levels, this is unlikely because S1P levels exhibited only a moderate and statistically insignificant increase with TA+CNL. In vitro studies showed that 4T1 cells are highly resistant to C6, offering the most likely explanation for the inability of TA to synergize with CNL. Thus, while our results show that sparse scan TA is a powerful approach for markedly enhancing CNL delivery and generating "anti-tumor" shifts in long-chain to very-long-chain ceramide ratios, resistance of the tumor to C6 can still be a rate-limiting factor for some solid tumor types.
聚焦超声（FUS）的稀疏扫描部分热消融（TA）可用于治疗实体瘤，并增加全身给药疗法的递送。此外，依赖增强渗透与滞留（EPR）效应进行递送的载有C6-神经酰胺的纳米脂质体（CNL），已显示出治疗实体瘤的前景，并且正在进行临床试验。在此，我们的目标是确定CNL与TA联合使用在控制4T1乳腺肿瘤方面是否具有协同作用。4T1肿瘤的CNL单药治疗通过EPR效应在肿瘤内产生了显著的生物活性C6积累，但肿瘤生长未得到控制。与EPR效应相比，TA使生物活性C6积累增加了约12.5倍。此外，TA+CNL导致长链神经酰胺与极长链神经酰胺的比例（即C16/24和C18/C24）发生变化，这可能有助于肿瘤控制。尽管如此，肿瘤内神经酰胺水平的这些变化仍不足以实现超过TA与对照“空壳”纳米脂质体（GNL）联合使用时所达到的肿瘤生长控制。虽然这种缺乏协同作用可能是由于“促肿瘤”的1-磷酸鞘氨醇（S1P）水平升高，但这种可能性不大，因为TA+CNL处理后S1P水平仅出现适度且无统计学意义的增加。体外研究表明，4T1细胞对C6具有高度抗性，这为TA无法与CNL协同作用提供了最可能的解释。因此，虽然我们的结果表明稀疏扫描TA是显著增强CNL递送并使长链神经酰胺与极长链神经酰胺比例产生“抗肿瘤”变化的有效方法，但肿瘤对C6的抗性仍然可能是某些实体瘤类型的限速因素。
