Cytokine analysis as a tool to understand tumour-host interaction in ovarian cancer

Epithelial ovarian cancer (EOC) is an immunogenic tumour and exploits many suppressive ways to escape immune eradication. EOC is known to spread primarily by tumour cell implantations in peritoneal cavity. Therefore, ascites may be an ideal fluid compartment to unravel the immune status of the peritoneal cavity. We analysed the expression of IL-1β, IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, IL-12p70, IFN-γ, TNF-α, TNF-β, TGF-β and CCL22 in ovarian cancer ascites, representing immune activating and suppressing cytokines. We observed high expression of pro-inflammatory cytokines IL-6, IL-8 and immune suppressive cytokines IL-10, CCL22 and TGF-β in most samples whereas Th1 (IL-12p70, IFN-γ) and Th2 (IL-4, IL-5) cytokines were only detectable in 13% of the samples. TGF-β was only detected in latent form, questioning its immune suppressive role. CCL22 was in similar levels present in early stage compared to advanced stage tumours. At advanced stage, we observed a negative correlation with CCL22 levels and Th1/2 cytokine expression. We found a positive correlation between IL-6 concentration in ascites and residual disease after debulking. Additionally, IL-6 levels were remarkably higher at recurrence compared to primary advanced disease, which opens an opportunity for inhibition of IL-6 expression in the prevention of recurrence. Despite the heterogeneity of EOC and the complexity of cytokine functions, our results show that cytokine analysis in ascites may aid in understanding tumour-host interaction in EOC.