ABSTRACT
The growth of disseminated tumor cells into metastatic lesions depends on the establishment of a favorable microenvironment in the stroma of the target organs. Here we show that mice treated with anakinra, an antagonist of the interleukin (IL)-1ß receptor (IL-1R), or harboring a targeted deletion of IL-1R are significantly less prone to develop bone tumors when inoculated in the arterial circulation with human prostate cancer (PCa) cells expressing IL-1ß. Interestingly, human mesenchymal stem cells exposed in vitro to medium conditioned by IL-1ß-expressing cancer cells responded by upregulating S100A4, a marker of cancer-associated fibroblasts (CAFs), and this effect was blocked by anakinra. Analogously, the stroma adjacent to skeletal metastases generated in mice by IL-1ß-expressing cancer cells showed a dramatic increase in S100A4, COX-2 and the alteration of 30 tumor-related genes as measured by Nanostring analysis. These effects were not observed in the stroma associated with the rare and much smaller metastases generated by the same cells in IL-1R knockout animals, confirming that tumor-secreted IL-1ß generates skeletal CAFs and conditions the surrounding bone microenvironment. In skeletal lesions from patients with metastatic PCa, histological and molecular analyses revealed that IL-1ß is highly expressed in cancer cells in which the androgen receptor (AR) is not detected (AR-), whereas this cytokine is uniformly absent in the AR-positive (AR+) metastatic cells. The stroma conditioned by IL-1ß-expressing cancer cells served as a supportive niche also for coexisting IL-1ß-lacking cancer cells, which are otherwise unable to generate tumors after independently seeding the skeleton of mice. This niche is established very early following tumor seeding and hints to a role of IL-1ß in promoting early colonization of PCa at the skeletal level.
Subject(s)
Bone Neoplasms/metabolism , Bone Neoplasms/secondary , Cell Communication , Prostatic Neoplasms/pathology , Tumor Microenvironment , Animals , Biomarkers , Cell Line, Tumor , Cell Proliferation , Disease Models, Animal , Gene Expression , Heterografts , Humans , Interleukin-1beta/metabolism , Male , Mesenchymal Stem Cells/metabolism , Mice , Neoplasm Metastasis , Phenotype , Receptors, Androgen/genetics , Receptors, Androgen/metabolism , Signal Transduction , Stromal Cells/metabolismABSTRACT
Cancer cells upregulate glycolysis, increasing glucose uptake to meet energy needs. A small fraction of a cell's glucose enters the hexosamine biosynthetic pathway (HBP), which regulates levels of O-linked beta-N-acetylglucosamine (O-GlcNAc), a carbohydrate posttranslational modification of diverse nuclear and cytosolic proteins. We discovered that breast cancer cells upregulate the HBP, including increased O-GlcNAcation and elevated expression of O-GlcNAc transferase (OGT), which is the enzyme catalyzing the addition of O-GlcNAc to proteins. Reduction of O-GlcNAcation through RNA interference of OGT in breast cancer cells leads to inhibition of tumor growth both in vitro and in vivo and is associated with decreased cell-cycle progression and increased expression of the cell-cycle inhibitor p27(Kip1). Elevation of p27(Kip1) was associated with decreased expression and activity of the oncogenic transcription factor FoxM1, a known regulator of p27(Kip1) stability through transcriptional control of Skp2. Reducing O-GlcNAc levels in breast cancer cells decreased levels of FoxM1 protein and caused a decrease in multiple FoxM1-specific targets, including Skp2. Moreover, reducing O-GlcNAcation decreased cancer cell invasion and was associated with the downregulation of matrix metalloproteinase-2, a known FoxM1 target. Finally, pharmacological inhibition of OGT in breast cancer cells had similar anti-growth and anti-invasion effects. These findings identify O-GlcNAc as a novel mechanism through which alterations in glucose metabolism regulate cancer growth and invasion and suggest that OGT may represent novel therapeutic targets for breast cancer.
