Combinatorial Application of Papain and CD66B for Isolating Glioma- Associated Neutrophils.

BACKGROUND: Stromal cells in the tumor microenvironment play crucial roles in glioma development. Current methods for isolating tumor-associated stromal cells (such as neutrophils) are inefficient due to the conflict between tissue dissociation and cell surface protein protection, which hampers the research on patient-derived stromal cells. Our study aims to establish a novel method for isolating glioma-associated neutrophils (GANs). METHODS: To observe neutrophil-like polymorphonuclear cells, we performed Hematoxylin-Eosin staining on glioma tissues. For isolating single cells from glioma tissues, we evaluated the efficiency of tissue dissociation with FastPrep Grinder-mediated homogenization or proteases (trypsin or papain) digestion. To definite specific markers of GANs, fluorescence-activated cell sorting (FACS) and immunofluorescence staining were performed. FACS and Ficoll were performed for the separation of neutrophils from glioma tissue-derived single-cell or whole blood pool. To identify the isolated neutrophils, FACS and RT-PCR were carried out. RESULTS: Neutrophil-like cells were abundant in high-grade glioma tissues. Among the three tissue dissociation methods, papain digestion produced a 5.1-fold and 1.7-fold more living cells from glioma mass than physical trituration and trypsin digestion, respectively, and it preserved over 97% of neutrophil surface protein markers. CD66B could be adopted as a unique neutrophil surface protein marker for FACS sorting in glioma. Glioma-derived CD66B+ cells specifically expressed neutrophil marker genes. CONCLUSION: A combination of papain-mediated tissue dissociation and CD66B-mediated FACS sorting is an effective novel method for the isolation of GANs from glioma tissues.

CRISPR as a strong gene editing tool.

Clustered regularly-interspaced short palindromic repeats (CRISPR) is a new and effective genetic editing tool. CRISPR was initially found in bacteria to protect it from virus invasions. In the first step, specific DNA strands of virus are identified by guide RNA that is composed of crRNA and tracrRNA. Then RNAse III is required for producing crRNA from pre-crRNA. In The second step, a crRNA:tracrRNA:Cas9 complex guides RNase III to cleave target DNA. After cleavage of DNA by CRISPR-Cas9, DNA can be fixed by Non- Homologous End Joining (NHEJ) and Homology Directed Repair (HDR). Whereas NHEJ is simple and random, HDR is much more complex and accurate. Gene editing by CRISPR is able to be applied to various biological field such as agriculture and treating genetic diseases in human. [BMB Reports 2017; 50(1): 20-24].

SR proteins regulate V6 exon splicing of CD44 pre-mRNA.

CD44 pre-mRNA includes 20 exons, of which exons 1-5 (C1-C5) and exons 16-20 (C6-C10) are constant exons, whereas exons 6-15 (V1-V10) are variant exons. V6-exon-containing isoforms have been known to be implicated in tumor cell invasion and metastasis. In the present study, we performed a SR protein screen for CD44 V6 splicing using overexpression and lentivirus-mediated shRNA treatment. Using a CD44 V6 minigene, we demonstrate that increased SRSF3 and SRSF4 expression do not affect V6 splicing, but increased expression of SRSF1, SRSF6 and SRSF9 significantly inhibit V6 splicing. In addition, using a constitutive exon-specific primer set, we could not detect alterations of CD44 splicing after SR protein-targeting shRNA treatment. However, using a V6 specific primer, we identified that reduced SRSF2 expression significantly reduced the V6 isoform, but increased V6-10 and V6,7-10 isoforms. Our results indicate that SR proteins are important regulatory proteins for CD44 V6 splicing. [BMB Reports 2016; 49(11): 612-616].