INTRODUCTION: Epithelial ovarian cancer (EOC) is the most lethal gynecologic 
malignancy worldwide and despite an initial response to therapeutic agents, the 
majority of patients have chemoresistant disease. There is no treatment strategy 
with proven efficacy against chemoresistant EOC and in this setting, overcoming 
therapy resistance is the key to successful treatment.
METHODS: This study aimed to investigate expression of interleukin-6 (IL-6) 
(IL-6) and IL-6 receptor (IL-6R) in a panel of the EOC cell lines. To achieve 
this, the expression of IL-6 and its receptor were compared in the EOC cells 
using quantitative reverse transcription polymerase chain reaction. MTT assay 
was performed to obtain chemosensitivity of the EOC cells.
RESULTS: In this report, we show that expressions of IL6 and IL6R are higher in 
therapy-resistant EOC cells compared to sensitive ones. Higher expression of IL6 
and its receptor correlated with resistance to certain chemotherapeutic agents. 
Moreover, our findings showed that combination of tocilizumab (Actemra; Roche), 
an anti-IL-6R monoclonal antibody, with carboplatin synergistically inhibited 
growth and proliferation of the EOC cells and the most direct axis for IL-6 gene 
expression was NF-κB pathway.
CONCLUSION: Collectively, our findings suggest that blockade of the IL-6 
signaling pathway with anti-IL-6 receptor antibody tocilizumab might resensitize 
the chemoresistant cells to the current chemotherapeutics.