Genome-wide association studies (GWAS) and fine-mapping efforts to date have identified more than 100 prostate cancer (PrCa)-susceptibility loci. We meta-analyzed genotype data from a custom high-density array of 46,939 PrCa cases and 27,910 controls of European ancestry with previously genotyped data of 32,255 PrCa cases and 33,202 controls of European ancestry. Our analysis identified 62 novel loci associated (P < 5.0 × 10) with PrCa and one locus significantly associated with early-onset PrCa (≤55 years). Our findings include missense variants rs1800057 (odds ratio (OR) = 1.16; P = 8.2 × 10; G>C, p.Pro1054Arg) in ATM and rs2066827 (OR = 1.06; P = 2.3 × 10; T>G, p.Val109Gly) in CDKN1B. The combination of all loci captured 28.4% of the PrCa familial relative risk, and a polygenic risk score conferred an elevated PrCa risk for men in the ninetieth to ninety-ninth percentiles (relative risk = 2.69; 95% confidence interval (CI): 2.55-2.82) and first percentile (relative risk = 5.71; 95% CI: 5.04-6.48) risk stratum compared with the population average. These findings improve risk prediction, enhance fine-mapping, and provide insight into the underlying biology of PrCa.

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.