Effect of CRISPR MIEN1 knockout in metastatic breast cancer cells




Van Treuren, Timothy


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Migration and Invasion Enhancer 1 (MIEN1) is an oncogene which is involved in facilitating the migration and invasion of cancer cells through actin dynamics and gene expression. Increased MIEN1 expression in many types of tumors correlates with disease progression and metastatic propensity. The precise mechanism by which MIEN1 functions is yet to be understood. The goal of these studies is to progress toward determination of the mechanisms and genetic context in which MIEN1 functions contribute to cancer progression. It was hypothesized that Clustered Regularly Interspaced Short Palindromic Repeat (CRISPR) mediated knockout of MIEN1 in metastatic breast cancer cells would result in reduced migration and invasion. CRISPR genome editing effectively produced specific genomic deletions in the MIEN1 gene which led to the elimination of its expression in these breast cancer cells. Migration in MDA-MB-231 (231) MIEN1 knockout (MIEN1-KO) cells exhibited no difference when compared to parental 231, which was in contrast with previous siRNA studies. Signaling in several MIEN1-KO pools was inconsistent. Knocking out MIEN1 in 231 derivative cell lines showed few significant alterations in the growth, migration, invasion, signaling, despite significant changes in metabolism. However, re-expression of the MIEN1 protein containing a mutant immunoreceptor tyrosine-based activation motif (ITAM) domain resulted in significantly decreased invasion. This revealed that MIEN1-KO 231 derivative cells were susceptible to interference of compensatory mechanisms and demonstrates the importance of the migration and invasion pathways in which MIEN1 participates in breast cancer metastasis. These findings also suggest MIEN1 may still be a promising therapeutic target to inhibit metastasis if inhibitors can be developed which block ITAM function without affecting localization or expression.