Abstract 2785: 13C-MRI detects increased lactate flux in HCC following hepatic thermal A\ablation and correlates with PFKFB3 Expression
Authors: Dou Qianhui , Grant Aaron K. , Callahan Cody , Mwin David , Ahmed Muneeb , Tsai Leo L. 
Published: September 2020

Abstract
Thermal ablation (TA) is an accepted therapy for early HCC and hepatic metastases from colorectal and breast cancers. However, suboptimal TA is a risk factor for early HCC recurrence and has been associated with a reduction in overall survival. This effect has been attributed to hypoxic response in periablative tissue mediated by HIF-1. Malignant transformation leads to increased anaerobic glycolysis even under normoxic conditions. This process is detectable by hyperpolarized 13C MRI (h13C MRI), which enables real-time high-resolution imaging of the conversion from pyruvate to lactate and may be used as a potential predictor for therapeutic response in HCC. We have identified two potential metabolic regulators and therapeutic targets with a direct link to lactate flux which may be monitored with h13C MRI. PFKFB3 has been identified as a crucial metabolic factor in several cancer types, encoding for inducible 6-phosphofructo-2-kinase and enhancing production of F2,6P2, consequently activating PK1 and glycolysis. Expression levels of PFKFB3 have been found to be higher in malignancies than in normal tissues, attributed to loss of glycolytic control and accelerating neoplastic activity. Hexokinase 3 (HK3), a key catalyst in the first committed steps in glucose metabolism, is also a key promoter involved in epithelial-mesenchymal transition. When we exposed an HCC rat cell line, N1S1, to heat stress, simulating the marginal zone of TA therapy, 20%-90% of cells survived at 40°C-50°C and there was no survival by 55°C. 5-8 days following this treatment, cell proliferation and mRNA expression of glycolysis-related genes were analyzed. Cellular proliferation rate was significantly higher in the heat-treated groups. mRNA expression of PFKFB3 was increased after thermal treatment, while HK3 expression was significantly decreased. We then developed an in vivo orthotopic rat model of a solitary N1S1 HCC and used h13C MRI to measure in vivo tumor lactate flux in response to radiofrequency ablation (RFA), a type of thermal ablation, of adjacent normal hepatic tissue, simulating local treatment of a distant lesion. h13C MRI demonstrated significantly increased tumor 13C lactate flux in the RFA arm relative to the control group (change in lactate-to-pyruvate ratio of 0.236±0.278 vs -0.035±0.107, p=0.0465, n=6), while background liver lactate flux was unchanged. We found that this correlated with mRNA expression of PFKFB3 and HK3, which was statistically significantly greater within tumors from the RFA group compared to control tumors (PFKFB3, 1.052±0.091 vs 0.655±0.294, p=0.0004, n=6; HK3, 0.751±0.130 vs 0.501±0.163, p=0.0036, n=6). The PFKFB3 expression patterns were concordant between in vitro and in vivo experiments. Our data shows that PFKFB3 may be an attractive treatment target for HCC, and h13C MRI may be a noninvasive technique well-suited to monitor treatment response.
Citation Format: Qianhui Dou, Aaron K. Grant, Cody Callahan, David Mwin, Muneeb Ahmed, Leo L. Tsai. 13C-MRI detects increased lactate flux in HCC following hepatic thermal A\ablation and correlates with PFKFB3 Expression [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2785.