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Prostate. 2019 Feb;79(2):215-222. doi: 10.1002/pros.23726. Epub 2018 Oct 21.

A role for paracrine interleukin-6 signaling in the tumor microenvironment in prostate tumor growth.

Author information

1
Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, Maryland.
2
Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University School of Medicine, Baltimore, Maryland.
3
Department of Urology, James Buchanan Brady Urological Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland.

Abstract

BACKGROUND:

Interleukin-6 (IL-6) is a mediator of inflammation that can facilitate prostate cancer progression. We previously demonstrated that IL-6 is present in the prostate tumor microenvironment and is restricted almost exclusively to the stromal compartment. The present study examined the influence of paracrine IL-6 signaling on prostate tumor growth using allograft models of mouse prostate cancer (TRAMP-C2), colon cancer (MC38), and melanoma (B16) cell lines in wildtype (WT) and IL-6 knockout (IL-6-/- ) mice.

METHODS:

Cells were implanted into WT or IL-6-/- mice and tumor sizes were measured at a 3 to 4 day interval. Serum, tumors, and other organs were collected for IL-6 analysis by ELISA and RNA in situ hybridization (RISH).

RESULTS:

There was a significant reduction in TRAMP-C2 and B16 tumor size grown in IL-6-/- mice versus WT mice (P = 0.0006 and P = 0.02, respectively). This trend was not observed for the MC38 cell line. RISH analysis of TRAMP-C2 tumors grown in WT mice showed that cells present in the tumor microenvironment were the primary source of IL-6 mRNA, not the TRAMP-C2 cells. Serum IL-6 ELISA analyses showed an increase in the circulating levels of IL-6 in WT mice bearing TRAMP-C2 tumors. Similar phospho-STAT3 expression and tumor vascularization were observed in TRAMP-C2 tumors grown in WT and IL-6-/- mice.

CONCLUSIONS:

Our results are consistent with previous studies in prostate cancer patients demonstrating that paracrine IL-6 production in the tumor microenvironment may influence tumor growth. Additionally, these data provide evidence that elevated systemic IL-6 levels may be involved in tumor growth regulation in prostate cancer, and are not simply caused by or indicative of tumor burden.

KEYWORDS:

inflammation; interleukin 6; microenvironment; prostate cancer; tumor growth

PMID:
30345534
DOI:
10.1002/pros.23726

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