Biological subtypes and survival outcomes in breast cancer patients with brain metastases in the targeted therapy era

A risk stratification model for predicting brain metastasis and brain screening benefit in patients with metastatic triple-negative breast cancer

BACKGROUND

Patients with metastatic triple-negative breast cancer (mTNBC) frequently experience brain metastasis. This study aimed to identify prognostic factors and construct a nomogram for predicting brain metastasis possibility and brain screening benefit in mTNBC patients.

METHODS

Patients with mTNBC treated at our institution between January 2011 and December 2018 were retrospectively analyzed. Fine and Gray's competing risks model was used to identify independent prognostic factors. By integrating these prognostic factors, a competing risk nomogram and risk stratification model were developed and evaluated with concordance index (C-index) and calibration curves.

RESULTS

A total of 472 patients were retrospectively analyzed, including 305 patients in the training set, 78 patients in the validation set I and 89 patients in the validation set II. Four clinicopathological factors were identified as independent prognostic factors in the nomogram: lung metastasis, number of metastatic organ sites, hilar/mediastinal lymph node metastasis and KI-67 index. The C-indexes and calibration plots showed that the nomogram exhibited a sufficient level of discrimination. A risk stratification was further generated to divide all the patients into three prognostic groups. The cumulative incidence of brain metastasis at 18 months was 5.3% (95% confidence interval [CI], 2.5%-9.7%) for patients in the low-risk group, while 14.3% (95% CI, 9.3%-20.4%) for patients with intermediate risk and 34.3% (95% CI, 26.8%-41.9%) for patients with high risk. Routine brain MRI screening improved overall survival in high-risk group (HR 0.67, 95% CI 0.46-0.98, P = .039), but not in low-risk group (HR 0.93, 95% CI 0.57-1.49, P = .751) and intermediate-risk group (HR 0.83, 95% CI 0.55-1.27, P = .386).

CONCLUSIONS

We have developed a robust tool that is able to predict subsequent brain metastasis in mTNBC patients. Our model will allow selection of patients at high risk for brain metastasis who might benefit from routine bran MRI screening.

PRMT5 Promotes Aerobic Glycolysis and Invasion of Breast Cancer Cells by Regulating the LXRα/NF-κBp65 Pathway

Objective

To explore the effects of protein arginine methyltransferase 5 (PRMT5) on the biological function of breast cancer cells (BCCs) by regulating the liver X receptor α (LXRα)/NF-κBp65 pathway.

Methods

A total of 80 patients with breast cancer (BC) admitted to our hospital were collected, and 80 breast cancer tissue specimens and 80 corresponding tumor-adjacent tissue specimens were sampled from them for analysis. The reverse transcription-polymerase chain reaction (RT-PCR) was employed to determine the expression of PRMT5 mRNA in the sampled tissues, and the Western blot to determine the expression of LXRα and NF-κBp65 proteins in the tissues and cells. The patients were followed up to analyze their 3-year survival rate. Stable and transient overexpression vectors and inhibition vectors were constructed and transfected into BCCs. The cell counting kit-8 (CCK8), transwell, and flow cytometry were adopted to analyze the proliferation, invasion, and apoptosis of transfected cells, on which the effects of PRMT5 on LXRα and NF-κBp65 proteins were analyzed.

Results

PRMT5 was highly expressed in BC patients, and LXRα was lowly expressed in them, which had a high diagnostic value. Patients with high expression of PRMT5 showed a poor prognosis, and the expression of PRMT5 was related to the tumor size, pathological stage, differentiation, and metastatic in BC patients. Overexpressed PRMT5 enhanced the cell proliferation, invasion, and glycolysis abilities, weakened apoptosis ability, further lowered expression of LXRα and increased expression of NF-κBp65, while inhibited PRMT5 caused opposite results in those aspects. Up-regulating the expression of LXRα suppressed the proliferation, invasion, and aerobic glycolysis of BCCs and promoted their apoptosis, while inhibiting it posed opposite effects. The rescue experiment revealed that down-regulating the expression of PRMT5 could counteract the promotion of down-regulation of LXRα on proliferation, invasion and glycolysis of BCCs, and the nude mouse tumorigenesis test revealed that PRMT5 induced tumor on nude mice by mediating LXRα/NF-κBp65.

Conclusion

Inhibition of the PRMT5 expression can accelerate apoptosis of BCCs and weaken their proliferation, invasion, and aerobic glycolysis through the LXRα/NF-κBp65 pathway.