Interventional Optical Imaging-Monitored Synergistic Effect of Radio-Frequency Hyperthermia and Oncolytic Immunotherapy.

Hui Zheng,Hongxiu Ji,Xiaoming Yang,Weizhu Yang,Wayne Monsky,Feng Zhang

doi:10.3389/fonc.2021.821838

Abstract

PurposeTo develop a new interventional oncology technique using indocyanine green (ICG)-based interventional optical imaging (OI) to monitor the synergistic effect of radiofrequency hyperthermia (RFH)-enhanced oncolytic immunotherapy.Materials and MethodsThis study included (1) optimization of ICG dose and detection time-window for intracellular uptake by VX2 tumor cells; (2) in-vitro confirmation of capability of using ICG-based OI to assess efficacy of RFH-enhanced oncolytic therapy (LTX-401) for VX2 cells; and (3) in-vivo validation of the interventional OI-monitored, intratumoral RFH-enhanced oncolytic immunotherapy using rabbit models with orthotopic liver VX2 tumors. Both in-vitro and in-vivo experiments were divided into four study groups (n=6/group) with different treatments: (1) combination therapy of RFH+LTX-401; (2) RFH alone at 42°C for 30 min; (3) oncolytic therapy with LTX-401; and (4) control with saline. For in-vivo validation, orthotopic hepatic VX2 tumors were treated using a new multi-functional perfusion-thermal radiofrequency ablation electrode, which enabled simultaneous delivery of both LTX-401 and RFH within the tumor and at the tumor margins.ResultsIn in-vitro experiments, taking up of ICG by VX2 cells was linearly increased from 0 μg/mL to 100 μg/mL, while ICG-signal intensity (SI) reached the peak at 24 hours. MTS assay and apoptosis analysis demonstrated the lowest cell viability and highest apoptosis in combination therapy, compared to three monotherapies (P<0.005). In in-vivo experiments, ultrasound imaging detected the smallest relative tumor volume for the combination therapy, compared to other monotherapies (P<0.005). In both in-vitro and in-vivo experiments, ICG-based interventional optical imaging detected a significantly decreased SI in combination therapy (P<0.005), which was confirmed by the “gold standard” optical/X-ray imaging (P<0.05). Pathologic/laboratory examinations further confirmed the significantly decreased cell proliferation with Ki-67 staining, significantly increased apoptotic index with TUNEL assay, and significantly increased quantities of CD8 and CD80 positive cells with immunostaining in the combination therapy group, compared to other three control groups (P<0.005).ConclusionsWe present a new interventional oncology technique, interventional optical imaging-monitored RFH-enhanced oncolytic immunotherapy, which may open new avenues to effectively manage those patients with larger, irregular and unresectable malignancies, not only in liver but also the possibility in other organs.

Highlights

Advanced techniques of interventional oncology, including tumor ablation and embolization, have become important tools in managing patients with primary and secondary malignancies
Fluorescence microscopic images of VX2 cells incubated with indocyanine green (ICG) at different concentrations from 0 mg/ml to 125 mg/ml, showing that ICG-emitting pink fluorescent signals became more intense as ICG concentration increases (Figure 3A)
The optimal time point of 24 hours post treatment of VX2 cells with ICG was selected as the optimum parameter for the in-vitro interventional optical imaging

Summary

Introduction

Advanced techniques of interventional oncology, including tumor ablation and embolization, have become important tools in managing patients with primary and secondary malignancies. These efficacious interventional therapies have prominent advantages, including being minimally invasive and repeatable, offering low risk of complications, and requiring only a short hospital stay. One example is to administer chemoembolization prior to RFA, which reduces downstream hepatic arterial blood flow and thereby diminishes the “heat-sink” effect [7] This combination requires two consecutive treatment sessions, which poses additional operational risks, longer hospital stays and higher hospital costs for patients. This bears the limitations of systemic chemotherapy, i.e., less than adequate therapeutic drug dose reaching the tumor site, toxicity to other vital organs, and, most importantly, frequent development of multi-drug resistance

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