IL-6 mediates platinum-induced enrichment of ovarian cancer stem cells
Yinu Wang, Xingyue Zong, Sumegha Mitra, Anirban Kumar Mitra, Daniela Matei, Kenneth P. Nephew
Yinu Wang, Xingyue Zong, Sumegha Mitra, Anirban Kumar Mitra, Daniela Matei, Kenneth P. Nephew
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Research Article Inflammation Stem cells

IL-6 mediates platinum-induced enrichment of ovarian cancer stem cells

Abstract

In high-grade serous ovarian cancer (OC), chemotherapy eliminates the majority of tumor cells, leaving behind residual tumors enriched in OC stem cells (OCSC). OCSC, defined as aldehyde dehydrogenase–positive (ALDH+), persist and contribute to tumor relapse. Inflammatory cytokine IL-6 is elevated in residual tumors after platinum treatment, and we hypothesized that IL-6 plays a critical role in platinum-induced OCSC enrichment. We demonstrate that IL-6 regulates stemness features of OCSC driven by ALDH1A1 expression and activity. We show that platinum induces IL-6 secretion by cancer-associated fibroblasts in the tumor microenvironment, promoting OCSC enrichment in residual tumors after chemotherapy. By activating STAT3 and upregulating ALDH1A1 expression, IL-6 treatment converted non-OCSC to OCSC. Having previously shown altered DNA methylation in OCSC, we show here that IL-6 induces DNA methyltransferase 1 (DNMT1) expression and the hypomethylating agent (HMA) guadecitabine induced differentiation of OCSC and reduced — but did not completely eradicate — OCSC. IL-6 neutralizing antibody (IL-6-Nab) combined with HMA fully eradicated OCSC, and the combination blocked IL-6/IL6-R/pSTAT3–mediated ALDH1A1 expression and eliminated OCSC in residual tumors that persisted in vivo after chemotherapy. We conclude that IL-6 signaling blockade combined with an HMA can eliminate OCSC after platinum treatment, supporting this strategy to prevent tumor recurrence after standard chemotherapy.

Authors

Yinu Wang, Xingyue Zong, Sumegha Mitra, Anirban Kumar Mitra, Daniela Matei, Kenneth P. Nephew

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Figure 7

Normal omental fibroblasts (NOFs) enhance IL-6 secretion.

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Normal omental fibroblasts (NOFs) enhance IL-6 secretion. (A) Baseline I...
(A) Baseline IL-6 secretion level by Kuramochi, OVCAR4, A2780, and NOFs (n = 3). (B) NOFs cells were cultured alone or cocultured with OCs (Kuramochi + NOFs, OVCAR4 + NOFs, A2780 + NOFs) under starving condition for 24 hours and then treated with CDDP (IC50 or half of IC50). IL-6 levels in the conditioned media were measured at 24 hours after exposure to CDDP by ELISA. IL-6 secretion (pg/ml/1 × 105 cells) was determined and normalized to the cell number. Average relative IL-6 secretion (± SD) of CDDP-treated cells compared with control-treated is shown in the graph (n = 3, 2-tailed Student’s t test, *P < 0.05, **P < 0.01, and ***P < 0.001). (C) Schematic diagram of transwell coculture system. In this 0.45-μm transwell coculture system, OC cells (Kuramochi_ALDH–/A2780_ALDH– cells) with starving medium (DMEM supplemented with 0.5% FBS) were seeded in the upper chambers alone (top) or with NOFs, which were seeded on the bottom chamber in DMEM supplemented with 0.5% FBS (bottom). (D and E) Average fold change with range of mRNA ALDH1A1, Sox2, and Bmi1 expression in (D) Kuramochi- and (E) A2780-derived ALDH– cells cocultured with NOFs compared with respective ALDH– cells alone shown in the graph (average fold change ± SD). Two-tailed Student’s t test was used to analyze statistical significance (n = 3, *P < 0.05, **P < 0.01, and ***P < 0.001).