Interleukin-8 released by cancer-associated fibroblasts attenuates the autophagy and promotes the migration of ovarian cancer cells

Abstract

The tumor microenvironment composed of a mixture of stromal cells and their secretions has a marked impact on cancer progression. In particular, soluble factors and metabolites contribute to malignancy through the dysregulation of autophagy in cancer cells. The present study investigated the effects of ovarian cancer-associated fibroblasts (OVCAFs) with their secretory substances on the autophagy and migration of ovarian cancer cells. The conditioned-medium (CM) of OVCAFs isolated from fresh human ovarian cancer tissues was analyzed for the levels of 27 common cytokines/chemokines using a cytokine array. Autophagy in cancer cells was assessed by determining the expression of the vacuolar form of LC3 by western blot analysis and immunofluorescence. Cancer cell migration was assessed by Transwell migration assay. Interleukin (IL)-8 was found to be the most highly upregulated cytokine among the cytokines/chemokines found in the OVCAF-CM. The role of IL-8 in ovarian cancer cell migration and its mechanistic link with autophagy was investigated. Recombinant human IL-8 (rhIL-8) stimulated the migration of SKOV3 and Kuramochi ovarian cancer cells, and concurrently downregulated basal autophagy, in concentration-dependent manner. Compared to the CM of control counterpart normal fibroblasts isolated from benign ovaries (OVNF-CM), the CM from 3 OVCAF isolates (namely, OVCAF-9, -20 and -43) exerted effects similar to rhIL-8 on both cancer cell lines. The pharmacological induction of autophagy with rapamycin or metformin attenuated the pro-migratory effects of IL-8. Neutralizing anti-IL-8 antibody counteracted the inhibitory effect of OVCAF-CM on basal autophagy. On the whole, the present study highlights the involvement of IL-8 released by CAFs in the ovarian tumor microenvironment in promoting cancer cell migration through the suppression of autophagy.