Objective  To investigate microRNA-30b (miRNA-30b) and integrin β3 (ITGB3) expression in breast cancer, and their effects on the biological behavior of breast cancer cells.

  Methods  One hundred and forty-four breast cancer tissue samples and their corresponding adjacent tissues, including in situ breast cancer and invasive and metastatic breast cancer tissues, were collected from the First Affiliated Hospital of Chengdu Medical College, from March 2016 to March 2019. Clinicopathological data were collected, and reverse transcription polymerase chain reaction (RT-PCR) was used to detect miRNA-30b and ITGB3 mRNA expression. Vectors for high miRNA-30b mimetic expression and high expression of ITGB3 (miRNA-30b-mimetic-pc DNA3.1-ITGB3) were constructed and stably transfected into MCF-7 cells, which were subcutaneously injected into nude mice. A 5-bromine deoxyuridine nucleoside (BrdU) labeling experiment, flow cytometry, and Transwell chamber invasion experiments were used to assess the proliferation ability, apoptosis rate, and invasion ability of each stable cell line. Western blot was used to detect ITGB3 expression.

  Results  RT-PCR results indicated that the relative expression of miRNA-30b in the original tumor, infiltrating cells, and metastatic breast cancer tissue were 0.75, 0.52, and 0.23, respectively, and ITGB3 mRNA levels were 2.17, 3.76, and 5.43, respectively, compared to that in normal tissues. Observed differences were statistically significant (all P<0.001). BrdU, flow cytometry, Transwell chamber invasion experiments, and Western blot showed that in breast cancer cells, proliferation, invasion, and ITGB3 expression were significantly reduced, and the apoptosis rate was increased (all P<0.001).

  Conclusions  The expressions of miRNA-30b and ITGB3 are abnormal in breast cancer tissues. miRNA-30b overexpression can significantly downregulate ITGB3 expression, inhibit breast cancer cell proliferation and invasion, and promote their apoptosis.