New relationship between IL-6 and Gemcitabine resistant cholangiocarcinoma cells

Introduction:

Cholangiocarcinoma (CC) has limited palliative treatment options. Gemcitabine plus Cisplatin is the current standard of care for inoperable patients, however the treatment outcome still has limitations due to resistance. Interleukin 6 (IL-6) signaling involves in chemotherapy-resistant mechanism. The aim of this study is to establish and characterize Gemcitabine resistant CC cells (GRCCs) as well as to investigate the role of IL-6 and other pathways in Gemcitabine resistant mechanism on CC.

Methods:

CC cells were continuously exposed to gradually increase concentrations of Gemcitabine to created resistant cells and resistant level was determined by IC₅₀ test. Invasion, MTT, colony formation assays were used to characterize and confirm resistance. Western Blot and qPCR were applied to investigate molecular variety of resistant and parental cells. In parallel, parental cells (co-treated by IL-6 stimulants or placebo) were treated by Gemcitabine, followed by investigation cell viability. Additionally, the effect of Siltuximab, an IL-6 antibody on CC parental cells was measure by invasion assay.

Results:

We established GRCCs with high level of resistance (IC₅₀ increased 10⁴ times). We found that Gemcitabine prevented migration and colony formation of CC parental cells but not of the resistant cells. Interestingly, Gemcitabine induced parental cells invasion. GRCCs proliferated more slowly, created less colonies and showed stronger invasion. Correspondingly, SZ1 resistant cells reduced E-Cadherin level compared to parental cells. Gemcitabine treatment increased IL-6 mRNA. Additionally, the presence of IL-6 stimulants protected the cells from Gemcitabine treatment. Siltuximab showed anti-invasive effect on both CC parental cells.

Conclusions:

GRCCs invaded more aggressively and Gemcitabine treatment highly induced parental CC cell invasion, which properly implies that Gemcitabine monotherapy can accelerate invasiveness and metastasis. Moreover, IL-6 stimulants protected CC cells from Gemcitabine therapy, Gemcitabine treatment increased IL-6 mRNA and IL-6 antibody prevented invasion on CC cell lines. Which reveal new relationship of IL-6 signaling and Gemcitabine resistance. Combination of IL-6 inhibitor and Gemcitabine might benefit for CC patients.