Expression Profiling of SWI/SNF Complex Subunits in Triple-Negative Breast Cancer Using Tissue Microarray and...

The SWI/SNF (SWItch/Sucrose Non - Fermentable) complex is a multi - subunit, ATPase - dependent chromatin - remodeling complex involved in regulating key cellular processes. Tumors with SWI/SNF loss tend to be poorly differentiated and aggressive. Triple - negative breast cancer (TNBC) typically has a high histological grade and a poor prognosis. Given the limited reports on the SWI/SNF complex in breast cancer, we focused on its role in TNBC.

Using tissue microarray and immunohistochemistry (IHC), we evaluated the expression of four important subunits of the SWI/SNF complex (SMARCB1, SMARCA2, ARID1A, and SMARCA4) in 104 TNBC tissues, which included 96 cases of conventional TNBC and 8 cases of low - grade TNBC. Additionally, we evaluated the endogenous expression of the four subunits in five breast cancer cell lines by real - time quantitative PCR (RT - qPCR). These cell lines consisted of two TNBC cell lines (MDA - MB - 231, MDA - MB - 468) and three non - TNBC cell lines (MCF - 7, T47D, and MDA - MB - 453).

The IHC results indicated that the deletion rate of SMARCA2 was the highest in TNBC compared with other subunits (91/104, 87.5%) (p < 0.0001), and SMARCA4 had the highest retention rate (98/104, 94.2%). Whether low - grade TNBC was excluded or not, there was no significant difference between the deletion rate and various clinicopathological parameters. Consistently, we found that SMARCA2 exhibited the lowest expression level across all five cell lines (p < 0.01). SMARCA4 showed the highest expression in all cell lines except MDA - MB - 453, in which ARID1A expression was the highest.

These results indicate that TNBC is characterized by a high proportion of SMARCA2 deletion and positive expression of SMARCA4, which are significant molecular features. The roles and potential mechanisms of these two factors in TNBC require further investigation.