BLM knockdown promotes cells autophagy via p53-AMPK-mTOR pathway in triple negative breast cancer cells.

Objective: This study investigated the function of the Bloom syndrome RecQ helicase-like gene (BLM) in triple-negative breast cancer (TNBC).

Methods: The expression levels of BLM in breast cancer cells were assessed using quantitative reverse transcription polymerase chain reaction (qRT-PCR), Western blotting, and immunohistochemical analysis. Cell proliferation, apoptosis, migration, and invasion were evaluated using the CCK-8 assay, clonogenic assay, flow cytometry, wound healing assay, and Transwell assay, respectively. Autophagosomes were observed via transmission electron microscopy (TEM). The expression levels of LC3B, Beclin1, and p62 were also measured. A murine xenograft model was employed to examine the impact of BLM on TNBC tumor growth, with tumor weight and volume recorded. Hematoxylin and eosin (H&E) staining and immunohistochemistry were utilized to assess pathological changes and Ki67 expression in tumor tissues. Additionally, Western blotting analysis was conducted to determine the expression of p53, AMPK, phosphorylated AMPK (p-AMPK), mTOR, and phosphorylated mTOR (p-mTOR).

Results: The expression of BLM was elevated in BT549 cells compared to normal cells. Following BLM knockdown, BT549 cell proliferation was significantly reduced, while apoptosis was enhanced. The migration rate of cells in the siBLM group was markedly decreased, as were the invasion and metastasis rates. TEM results indicated an increased presence of autophagosomes in the siBLM group, with significantly elevated expression levels of LC3B and Beclin1, and a decreased expression level of p62. Tumor volume and weight in the shBLM group were significantly lower than those in the shCtrl group. The number of intratumoral cells decreased, with most exhibiting nucleolysis or disintegration. Ki67 expression in the tumor tissue was also notably reduced. Additionally, the expression levels of p-mTOR, p-AMPK, and P53 proteins in the shBLM group were decreased.

Conclusion: The knockdown of BLM significantly inhibited cell proliferation, migration, and invasion, while promoting apoptosis. This effect may be mediated through the regulation of the p53-AMPK-mTOR pathway.