Background & objective: Estrogen directly up-regulates LRP16 gene expression via activating its receptor (ER), and the overexpression of LRP16 promotes the proliferation of human breast cancer cells. This study was to detect the mRNA level of LRP16 gene in breast cancer, and investigate its correlation to the clinicopathologic features.
Methods: The mRNA level of LRP16 in carcinoma and matched peritumor tissues from 22 breast cancer patients was detected by Northern blot, and that in the tissues from 30 patients was detected by semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR). The expression of Ki-67, ER, and progesterone receptor (PR) in the carcinoma tissues was detected by immunohistochemistry.
Results: According to the results of Northern blot, compared with that in peritumor tissues, LRP16 was overexpressed by 2 folds in 9 (40.9%) out of 22 breast cancer samples. Of the 9 samples with LRP16 overexpression, 7 were ER-positive, and 8 were PR-positive; of the 13 samples without LRP16 overexpression, 6 were ER-positive, and 5 were PR-negative. The positive rates of ER and PR were significantly higher in the samples with LRP16 overexpression than in the samples without LRP16 overexpression (P<0.05). Only 1 of the 9 samples with LRP16 overexpression was negative for both ER and PR, but 7 of the 13 without LRP16 overexpression were negative for both of them. The proportion of the tumors with diameters of 3.0-4.5 cm was significantly higher in the patients with LRP16 overexpression than in those without LRP16 overexpression (8/9 vs. 5/13, P=0.031). Axillary lymph node metastasis was detected in 12 out of 22 patients, including 8 of the 9 patients with LRP16 overexpression and 4 of the 13 without LRP16 overexpression (P=0.011). In addition, LRP16 overexpression was detected in 6 of the 8 patients with Ki-67 overexpression, and 2 of the 14 patients without Ki-67 overexpression (P=0.026). According to the results of RT-PCR, LRP16 was overexpressed in 9 (30%) out of 30 breast cancer samples. All of the 9 samples with LRP16 overexpression were positive for both ER and PR, with Ki-67 overexpression, tumor diameters of more than 3.5 cm and axillary lymph node metastasis. The differences between the patients with or without LRP16 overexpression were significant (P<0.05).
Conclusion: LRP16 overexpression is closely correlated to the positive rates of ER and PR, Ki-67 level, tumor diameter, and axillary lymph node metastasis of breast cancer, and might be involved in the proliferation and metastasis of human breast cancer.