Breast cancer cell line MDA-MB-231 miRNA profile expression after BIK interference: BIK involvement in autophagy

Abstract

B-cell lymphoma 2 (BCL2)-interacting killer (apoptosis inducing) (BIK) has been proposed as a tumor suppressor in diverse types of cancers. However, BIK's overexpression in breast cancer (BC) and in non-small lung cancer cells (NSCLCs), associated with a poor prognosis, suggests its participation in tumor progression. In this study, we evaluated the global expression pattern of microRNAs (miRNAs), messenger RNA (mRNA) expression changes in autophagy, and autophagic flux after BIK interference. BIK gene expression was silenced by small interfering RNA (siRNA) in BC cell MDA-MB-231, and BIK interference efficiency was tested by real-time PCR and by Western blotting. BIK expression levels decreased by 75 ± 18 % in the presence of 600 nM siRNA, resulting in the abolishment of BIK expression by 94 ± 30 %. BIK interference resulted in the overexpression of 17 miRNAs that, according to the DIANA-miRPath v3.0 database, are mainly implied in the control of cell signaling, gene expression, and autophagy. The autophagy array revealed downregulation of transcripts which participate in autophagy, and their interactome revealed a complex network, where hepatocyte growth factor-regulated tyrosine kinase substrate (HGS), α-synuclein (SNCA), unc-51-like autophagy activating kinase 1/2 (ULK1/2), and mitogen-activated protein kinase 3 (MAPK3) were shown to be signaling hubs. LC3-II expression-an autophagy marker-was increased by 169 ± 25 % after BIK interference, which indicates the involvement of BIK in autophagy. Altogether, our results indicate-for the first time-that BIK controls the expression of miRNAs, as well as the autophagic flux in MDA-MB-231 cells.

The pro-apoptotic paradox: the BH3-only protein Bcl-2 interacting killer (Bik) is prognostic for unfavorable outcomes in breast cancer

“…In addition to stimulating apoptotic pathways, Bik facilitates autophagy [20–22] and enhanced autophagy is associated with poor clinical outcomes [23–25]. Thus, using the gene expression microarray as a screening tool, we looked for a correlation between high Bik expression levels and markers of autophagy.…”

“…Bik was a target of autophagy and also actively contributed to autophagy induction [16]. Finally, silencing of endogenous Bik expression in the breast cancer cell line MDA-MB-231 downregulated crucial components of autophagic machinery [22]. We found that high Bik expression in breast cancer patients was significantly correlated with increased levels of the autophagy marker, ATG5.…”

Star-PAP, a poly(A) polymerase, functions as a tumor suppressor in an orthotopic human breast cancer model

“…27 Moreover, BIK controls the expression of miRNAs as well as the autophagic flux in MDA-MB-231 cells. 28 Thus, it would be interesting to investigate whether Star-PAP is involved in these new functions of BIK.…”

SNCA Is a Functionally Low-Expressed Gene in Lung Adenocarcinoma

“…However, recent studies have demonstrated the potential role of SNCA in the pathological processes underlying human cancer. B-cell lymphoma 2 (BCL2)-interacting killer (apoptosis inducing) (BIK) controls the expression of autophagy-associated transcripts, such as SNCA , that participate in tumor progression in the breast cancer cell line MDA-MB-231 [ 34 ]. SNCA methylation in the stool could also serve as a promising biomarker for the detection of colorectal cancer [ 6 ].…”