MiR-29a belongs to one of the subtypes of
miRNAs known as non-coding single-stranded RNAs and is preferentially expressed in normal tissues. B7-H3, a member of the B7/CD28
immunoglobulin superfamily, was shown to be overexpressed in several solid malignant
tumors, including
colon cancer. In addition, it is associated with
tumor progression and poor prognosis. We used immunohistochemical and Western blotting to assess B7-H3
protein expression levels in
colon cancer and adjacent normal tissues and then compared their relationships with clinicopathological factors. Quantitative real-time reverse-transcription PCR was used to assess B7-H3 and miRNA-29a
mRNA expression levels, and then their relationship and clinical significance were evaluated. In addition,
colon cancer Caco-2 cells, which constitutively overexpress B7-H3, were transfected with lentivirus particles for miR-29a upregulation. Invasion and migration assays were carried out in vitro along with the establishment of a subcutaneous xenograft model in vivo to determine the role of miRNA-29a in
colon cancer progression. The B7-H3
protein showed elevated expression in colon
carcinoma and was relevant to TNM staging,
lymph node metastasis, and reduced survival. Meanwhile, miR-29a was preferentially expressed in normal colon tissues, while B7-H3 transcript levels had no marked differences between
tumor and normal tissue specimens. In vitro, miR-29a upregulation resulted in reduced B7-H3 expression. Furthermore, miR-29a upregulation reduced the invasive and migratory abilities of colon
carcinoma cells. In animal models, upregulation of miR-29a slowed down the growth of subcutaneous xenotransplanted
tumors and resulted in prolonged survival time. MiR-29a downregulates B7-H3 expression and accordingly inhibits
colon cancer progression, invasion, and migration, indicating miR-29a and B7-H3 might represent novel molecular targets for advanced
immunotherapy in
colon cancer.