MicroRNA let-7, T cells, and patient survival in colorectal cancer

Ruoxu Dou, Reiko Nishihara, Yin Cao, Tsuyoshi Hamada, Kosuke Mima, Atsuhiro Masuda, Yohei Masugi, Yan Shi, Mancang Gu, Wanwan Li, Annacarolina Da Silva, Katsuhiko Nosho, Xuehong Zhang, Jeffrey A. Meyerhardt, Edward L. Giovannucci, Andrew T. Chan, Charles S. Fuchs, Zhi Rong Qian, Shuji Ogino

Research output: Contribution to journalArticlepeer-review

44 Citations (Scopus)


Experimental evidence suggests that the let-7 family of noncoding RNAs suppresses adaptive immune responses, contributing to immune evasion by the tumor. We hypothesized that the amount of let-7a and let-7b expression in colorectal carcinoma might be associated with limited T-lymphocyte infiltrates in the tumor microenvironment and worse clinical outcome. Utilizing the molecular pathological epidemiology resources of 795 rectal and colon cancers in two U.S.-nationwide prospective cohort studies, we measured tumor-associated let-7a and let-7b expression levels by quantitative reverse-transcription PCR, and CD3+, CD8+, CD45RO (PTPRC)+, and FOXP3+ cell densities by tumor tissue microarray immunohistochemistry and computer-assisted image analysis. Logistic regression analysis and Cox proportional hazards regression were used to assess associations of let-7a (and let-7b) expression (quartile predictor variables) with T-cell densities (binary outcome variables) and mortality, respectively, controlling for tumor molecular features, including microsatellite instability, CpG island methylator phenotype, LINE-1 methylation, and KRAS, BRAF, and PIK3CA mutations. Compared with cases in the lowest quartile of let-7a expression, those in the highest quartile were associated with lower densities of CD3+ [multivariate odds ratio (OR), 0.40; 95% confidence interval (CI), 0.23-0.67; Ptrend = 0.003] and CD45RO+ cells (multivariate OR, 0.31; 95% CI, 0.17-0.58; Ptrend = 0.0004), and higher colorectal cancer-specific mortality (multivariate hazard ratio, 1.82; 95% CI, 1.42-3.13; Ptrend = 0.001). In contrast, let-7b expression was not significantly associated with T-cell density or colorectal cancer prognosis. Our data support the role of let-7a in suppressing antitumor immunity in colorectal cancer and suggest let-7a as a potential target of immunotherapy.

Original languageEnglish
Pages (from-to)927-935
Number of pages9
JournalCancer Immunology Research
Issue number11
Publication statusPublished - 2016 Nov
Externally publishedYes

ASJC Scopus subject areas

  • General Medicine


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