[Overexpression of NDRG1: relationship with proliferative activity and invasiveness of breast cancer cell line and breast cancer metastasis]

Abstract

Objective: To investigate the relationship between NDRG1 and metastasis of breast cancer and the effects of NDRG1 overexpression on the proliferation and invasion of breast cancer cells.

Methods: NDRG1 was detected at its protein level by immunohistochemistry (IHC) and its messenger RNA (mRNA) was detected by real-time reverse transcriptase-polymerase chain reaction (real time RT-PCR) in clinical breast cancer specimens. Liposome was used to transiently transfer NDRG1 into MDA-MB-231, a highly invasive human breast cancer cell line. The proliferation of MDA-MB-231 was measured by Bromodeoxy Uridine (BrdU) incorporation assay and the transfection effect on cell cycle distribution was determined by fluorescence assisted cell sorting (FACS). The invasive ability of the transfected cells was investigated by reconstituted matrigel invasion and polycarbonate filters migration experiments.

Results: NDRG1 expressions at protein and mRNA levels in tumors of patients with lymph node metastases were significantly lower as compared with those with localized breast cancers (P < 0.01). The amount of NDRG1 mRNA in MCF7, a relatively non-invasive breast cancer cell line, was 10.8 times higher than that in MDA-MB-231 cells (P < 0.01). The BrdU incorporation rate declined significantly (P < 0.05) in NDRG1 overexpressing MDA-MB-231 cells. An increase of the cell population at G(0)/G(1) phase was observed 48 hours post-transfection along with a decrease of cell population at S phase. Overexpression of NDRG1 significantly retarded the invasiveness of MDA-MB-231 cells in matrigel-coated invasion chambers (P < 0.05), when compared to cells transfected with control vectors. However, the migration abilities of cells with or without the transfection were virtually identical.

Conclusions: NDRG1 expression reversely correlates with breast cancer metastasis and progression, and may serve as a prognostic biomarker for predicting early metastasis. The inhibition of proliferation and invasion demonstrated by our MDA-MB-231 transfection experiments implies that NDRG1 is a tumor metastasis suppressor gene and may be a new candidate for gene therapy against human breast cancer.