Roles of MALAT1 in development and migration of triple negative and Her-2 positive breast cancer

As a type of new targets for prognosis of malignancies, long non-coding RNA MALAT1 (metastasis-associated lung adenocarcinoma transcription 1) is associated with proliferation and metastatic abilities of several malignancies. However, its relations to development and migration of triple negative and human epidermal growth factor receptor 2 (Her-2) positive breast cancers haven't been reported.

In this paper, we aimed to discuss how MALAT1 is connected with and affects proliferation and invasion abilities of cells in Her-2 positive and triple-negative breast cancers (TNBC).

The expression of MALAT1 in clinical samples with TNBC and Her-2 positive breast cancers was tested by qRT-PCR. The statistical analysis was performed to unveil the potential relationships between the expression of MALAT1 and prognostic factors of breast cancer such as OS (overall survival), RFS (relapse-free survival), number of metastatic lymph nodes and pTNM staging in patients with TNBC or Her-2 positive breast cancer. MALAT1 and XBP1 were knockdown respectively in Her-2 positive cell line MDA-MB-231, and MALAT1 and Her-2 were knockdown respectively in TNBC cell line MDA-MD-435 using siRNA. The alterations of expressions of MALAT1 and related genes were detected by qRT-PCR in two breast cancer cell lines. The changes of proliferation abilities in two cell lines were observed using CCK8 assays. Furthermore, transwell assays were performed to detect changes to invasion abilities of the cells.

The expression of MALAT1 in triple negative and Her-2 positive breast cancers was positively correlated to the number of metastatic lymph nodes in patients with breast cancer. MALAT1 promotes proliferation and invasion abilities of breast cancer cells through XBP1 (X-box binding protein 1)-HIF (hypoxia-inducible factor)-1α pathway in MDA-MB-231 and through Her-2 pathway in MDA-MD-435. Moreover, MALAT1 could possibly be involved in regulation of MYC gene and CD47 (an immune checkpoint gene) in both cell lines.

Our study suggested that MALAT1 is a core signaling molecule for promoting development and migration of triple negative and Her-2 positive breast cancers. It would be employed as common markers for prognosis of the two types of breast cancer mentioned above and potential targets for treating them.