Combination of Photon and Carbon Ion Irradiation with Targeted Therapy Substances Temsirolimus and Gemcitabine in Hepatocellular Carcinoma Cell Lines.

Sarah Dehne,Thomas Haberer,Stefan Rieken,Daniel Habermehl,Jürgen Debus,Clarissa Fritz,Klaus-Josef Weber,Thomas E Schmid,Stephan Brons,Stephanie E Combs,Daniela Baris

doi:10.3389/fonc.2017.00035

Abstract

This work investigates on putative cytotoxic effects in four different hepatocellular carcinoma (HCC) cell lines after irradiation with photons or carbon ions in combination with new targeted molecular therapy using either Temsirolimus (TEM) or Gemcitabine (GEM). The HCC cell lines HepG2, Hep3B, HuH7, and PLC were cultured and irradiated with photons or carbon ions at the Heidelberg Ion Beam Therapy Center using the raster-scanning method. For combination experiments, cell lines were first treated with Temsirolimus or GEM before irradiation. Cytotoxicity was measured by a clonogenic survival assay. The evaluation of the experiments and the obtained survival curves were based on the concept of additivity defined by Steel and Peckham. The results for the combination of carbon ions and both tested systemic substances TEM and GEM showed independent toxicities in all four cell lines. Supra-additive effects were observed in PLC cells for photon irradiation combined either with TEM or GEM and in HuH7 cells for the combination of photons with TEM. Addition of targeted therapy substances Temsirolimus and GEM to photon irradiation showed additive cytotoxicity in HCC cell lines, whereas independent toxicities where reached by the combination of carbon ions to these substances. It can be assumed that combining 12C with systemic substances only has independent effects because heavy ions cause direct damage because of their high-LET character resulting in complex and clustered double-strand breaks. Nonetheless, further investigations are warranted in order to determine whether addition of systemic therapy allows a reduction of radiation doses in combination therapy. This could possibly lead to better responses and tolerances in patients with HCC.

Highlights

Hepatocellular carcinoma (HCC) is the fifth most common cancer worldwide and makes up the second common cause of cancer-related death in males
Photon and 12C irradiation was performed with all four HCC cell lines Hep3B, HepG2, PLC, and HUH7 to determine clonogenic survival
The surviving fractions determined were used to perform linear-quadratic fits and calculate clonogenic survival curves for each cell line in order to compare the effectiveness of photon and 12C irradiation

Summary

Introduction

Hepatocellular carcinoma (HCC) is the fifth most common cancer worldwide and makes up the second common cause of cancer-related death in males. In women, it is the seventh most common cancer worldwide and the sixth leading cause of death. The challenge of every applied treatment is to preserve sufficient rest liver function. At this point, there are several therapy modalities, mainly surgical excision or liver transplantation, which provide the most mature outcome data [2, 3]. There is a limit to a surgical therapy for HCC, because patients often present with a poor liver function because of an underlying cirrhosis, macro-vascular tumor invasion or advanced stage of the disease. This work investigates on putative cytotoxic effects in four different hepatocellular carcinoma (HCC) cell lines after irradiation with photons or carbon ions in combination with new targeted molecular therapy using either Temsirolimus (TEM) or Gemcitabine (GEM)

Methods

Results

Conclusion