MicroRNA-155 (miR-155) is overexpressed in many human cancers; however, the mechanisms by which miR-155 functions as a putative oncomiR are largely unknown. Here, we report that the tumor suppressor gene suppressor of cytokine signaling 1 (socs1) is an evolutionarily conserved target of miR-155 in breast cancer cells. We found that mir-155 expression is inversely correlated with socs1 expression in breast cancer cell lines as well as in a subset of primary breast tumors. We also identified a 24A→G mutation in the miR-155 binding site of the SOCS1 3′ untranslated region in a breast tumor that reduced miR-155 repression, implicating a mechanism for miRNA targets to avoid repression. Ectopic expression of miR-155 significantly promoted the proliferation of breast cancer cells, the formation of soft agar foci in vitro, and the development of tumors in nude mice. In breast cancer cells, RNA interference silencing of socs1 recapitulates the oncogenic effects of miR-155, whereas restoration of socs1 expression attenuates the protumorigenesis function of miR-155, suggesting that miR-155 exerts its oncogenic role by negatively regulating socs1. Overexpression of miR-155 in breast cancer cells leads to constitutive activation of signal transducer and activator of transcription 3 (STAT3) through the Janus-activated kinase (JAK) pathway, and stimulation of breast cancer cells by the inflammatory cytokines IFN-γ and interleukin-6 (IL-6), lipopolysaccharide (LPS), and polyriboinosinic:polyribocytidylic acid [poly(I:C)] significantly upregulates mir-155 expression, suggesting that miR-155 may serve as a bridge between inflammation and cancer. Taken together, our study reveals that miR-155 is an oncomiR in breast cancer and that miR-155 may be a potential target in breast cancer therapy. Cancer Res; 70(8); 3119–27. ©2010 AACR.

Cancer cells preferentially metabolize glucose through aerobic glycolysis. This phenomenon, known as the Warburg effect, is an anomalous characteristic of glucose metabolism in cancer cells. Chronic inflammation is a key promoting factor of tumourigenesis. It remains, however, largely unexplored whether and how pro‐tumourigenic inflammation regulates glucose metabolism in cancer cells. Here, we show that pro‐inflammatory cytokines promote glycolysis in breast cancer cells, and that the inflammation‐induced miR‐155 functions as an important mediator in this process. We further show that miR‐155 acts to upregulate hexokinase 2 ( hk2 ), through two distinct mechanisms. First, miR‐155 promotes hk2 transcription by activation of signal transducer and activator of transcription 3 (STAT3), a transcriptional activator for hk2 . Second, via targeting C / EBP β (a transcriptional activator for mir‐143 ), miR‐155 represses mir‐143 , a negative regulator of hk2 , thus resulting in upregulation of hk2 expression at the post‐transcriptional level. The miR‐155‐mediated hk2 upregulation also appears to operate in other types of cancer cells examined. We suggest that the miR‐155/miR‐143/HK2 axis may represent a common mechanism linking inflammation to the altered metabolism in cancer cells.

Hepatocellular carcinoma (HCC) is the third leading cause of cancer deaths worldwide. The HCC diagnosis is usually achieved by biomarkers, which can also help in prognosis prediction. Furthermore, it might represent certain therapeutic interventions through some combinations of biomarkers. Here, we review on our current understanding of HCC biomarkers.