CCCTC-binding factor (CTCF), a ubiquitous 11-zinc finger multifunctional protein, has distinct molecular functions, such as transcriptional activation, repression, and chromatin barrier activity, in a locus-specific manner. Elevated CTCF levels in breast cancer cells are known to contribute to tumorigenesis; however, the underlying mechanism remains elusive. We investigated the effect of CTCF expression on breast cancer cell survival and elucidated its mechanism. CTCF depletion in MCF-7 cells led to a decreased cell growth and proliferation, surpassing the growth of normal cells under co-culture system of MCF-7-GFP and MCF10A. Here we propose that the phenotypes observed in CTCF-depleted MCF-7 cancer cells, such as reduced cell proliferation, increased apoptosis, and cell cycle arrest, are closely linked with the activation of p53. The consensus CTCF-binding site, located approximately 800 bp upstream of the first exon of TP53, was marked by H3K27me3, but not by the active mark H3K4me3, although CTCF is expressed. Knockdown of CTCF conversely led to the recruitment of H3K4me3 instead of H3K27me3, accompanying with the higher enrichment of PolII in the proximal promoter region of TP53. With the activation of p53, increased p21 and Bax expressions were observed in CTCF knockdown MCF-7 cells. Elucidating functional roles of CTCF and regulation mechanisms may help to guide CTCF and/or its related molecules as a therapeutic target to prevent cancer cell growth.
Lactobacillus acidophilus is a rod-shaped, Gram-positive bacterium generally found in the normal flora of the oropharynx, gastrointestinal, and genitourinary tracts. It is commonly known as nonpathogen in the human body. Endocarditis due to Lactobacillus is rarely encountered and associated with impaired immunity. Splenic abscess is also an uncommon infection that classically results from endocarditis or another source of hematogenous seeding. Here, we present the case of bioprosthetic aortic valve endocarditis and associated splenic abscess caused by Lactobacillus acidophilus. The source of the Lactobacillus bacteremia should be investigated because of the risk of life-threatening conditions. Most of the time, identifying Lactobacillus species is challenging and can cause a delay in diagnosis and timely treatment. Especially in patients who have significant underlying clinical conditions, physicians should consider Lactobacillus species as a causative microorganism.
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