Colorectal cancer is the third most incident cancer and cause of cancer-related death in the United States. MicroRNAs, a class of small non-coding RNAs, have been implicated in the pathogenesis and prognosis of colorectal cancer, although few studies have examined the relationship between germline mutation in the microRNAs with risk and prognosis. We therefore investigated the association between a SNP in hsa-mir-608, which lies within the 10q24 locus, and colorectal cancer. A cohort consisting of 245 cases and 446 controls was genotyped for rs4919510. The frequency of the GC genotype was significantly higher in African Americans (15%) compared to Caucasians (3%) controls. There was no significant association between rs4919510 and colorectal risk (African American: OR (GC vs. CC) 0.89 [95% CI, 0.41-1.80]) (Caucasian: OR (GG vs. CC) 1.76 CI, 0.48-6.39]). However, we did observe an association with survival. The GC genotype was associated with an increased risk of death in Caucasians (HR (GG vs. CC) 3.54 ([95% CI, 1.38-9.12]) and with a reduced risk of death in African Americans (HR (GG vs. CC) 0.36 ([95% CI, 0.12-1.07]). These results suggest that rs4910510 may be associated with colorectal cancer survival in a manner dependent on race.Because chronic intestinal inflammation is a risk factor for colorectal cancer, we hypothesized that genetic variants of inflammatory mediators, such as mannose-binding lectin 2 (MBL2), are associated with colon cancer susceptibility. Here, we report the association of 24 MBL2 single-nucleotide polymorphisms (SNP) and corresponding haplotypes with colon cancer risk in a case-control study. Four SNPs in the 3'-untranslated region (UTR) of the gene (rs10082466, rs2120132, rs2099902, and rs10450310) were associated with an increased risk of colon cancer in African Americans. ORs for homozygous variants versus wild-type ranged from 3.17 [95% confidence interval (CI), 1.57-6.40] to 4.51 (95% CI, 1.94-10.50), whereas the 3'-UTR region haplotype consisting of these four variants had an OR of 2.10 (95% CI, 1.42-3.12). The C allele of rs10082466 exhibited a binding affinity of miR-27a and this allele was associated with both lower MBL plasma levels and activity. We found that 5'secretor haplotypes known to correlate with moderate and low MBL serum levels exhibited associations with increased risk of colon cancer in African Americans, specifically as driven by two haplotypes, LYPA and LYQC, relative to the referent HYPA haplotype (LYPA: OR, 2.60;95% CI, 1.33-5.08 and LYQC: OR, 2.28;95% CI, 1.20-4.30). Similar associations were not observed in Caucasians. Together, our results support the hypothesis that genetic variations in MBL2 increase colon cancer susceptibility in African Americans.MicroRNAs play a prominent role in a variety of physiological and pathological biological processes, including cancer. For rectal cancers, only limited data are available on microRNA expression profiles, while the underlying genomic and transcriptomic aberrations have been firmly established. In collaboration with Thomas Reid, we therefore aimed to comprehensively map the microRNA expression patterns of this disease. Experimental design: Tumor biopsies and corresponding matched mucosa samples were prospectively collected from 57 patients with locally advanced rectal cancers. Total RNA was extracted, and tumor and mucosa microRNA expression profiles were subsequently established for all patients. The expression of selected microRNAs was validated using semi-quantitative real-time PCR. Forty-nine microRNAs were significantly differentially expressed (log2-fold difference greater than 0.5 and p less than 0.001) between rectal cancer and normal rectal mucosa. The predicted targets for these microRNAs were enriched for the following KEGG pathways: Wnt, TGF-beta, mTOR, insulin, MAPK, and ErbB signaling. Thirteen of these 49 microRNAs seem to be rectal cancer-specific, and have not been previously reported for colon cancers: miR-492, miR-542-5p, miR-584, miR-483-5p, miR-144, miR-2110, miR-652*, miR-375, miR-147b, miR-148a, miR-190, miR-26a/b, and miR-338-3p. Of clinical impact, miR-135b expression correlated significantly with disease-free and cancer-specific survival in an independent multicenter cohort of 116 patients. This comprehensive analysis of the rectal cancer microRNAome uncovered novel microRNAs and pathways associated with rectal cancer. This information contributes to a detailed view of this disease. Moreover, the identification and validation of miR-135b may help to identify novel molecular targets and pathways for therapeutic exploitation.

National Institute of Health (NIH)
National Cancer Institute (NCI)
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National Cancer Institute Division of Basic Sciences
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Schetter, Aaron J; Okayama, Hirokazu; Harris, Curtis C (2012) The role of microRNAs in colorectal cancer. Cancer J 18:244-52
Ryan, Brid M; McClary, Andrew C; Valeri, Nicola et al. (2012) rs4919510 in hsa-mir-608 is associated with outcome but not risk of colorectal cancer. PLoS One 7:e36306
Schetter, Aaron J; Harris, Curtis C (2011) Alterations of microRNAs contribute to colon carcinogenesis. Semin Oncol 38:734-42
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