Myoferlin Depletion in Breast Cancer Cells Promotes Mesenchymal to Epithelial Shape Change and Stalls Invasion

Abstract

Myoferlin (MYOF) is a mammalian ferlin protein with homology to ancestral Fer-1, a nematode protein that regulates spermatic membrane fusion, which underlies the amoeboid-like movements of its sperm. Studies in muscle and endothelial cells have reported on the role of myoferlin in membrane repair, endocytosis, myoblast fusion, and the proper expression of various plasma membrane receptors. In this study, using an in vitro human breast cancer cell model, we demonstrate that myoferlin is abundantly expressed in invasive breast tumor cells. Depletion of MYOF using lentiviral-driven shRNA expression revealed that MDA-MB-231 cells reverted to an epithelial morphology, suggesting at least some features of mesenchymal to epithelial transition (MET). These observations were confirmed by the down-regulation of some mesenchymal cell markers (e.g., fibronectin and vimentin) and coordinate up-regulation of the E-cadherin epithelial marker. Cell invasion assays using Boyden chambers showed that loss of MYOF led to a significant diminution in invasion through Matrigel or type I collagen, while cell migration was unaffected. PCR array and screening of serum-free culture supernatants from shRNAMYOF transduced MDA-MB-231 cells indicated a significant reduction in the steady-state levels of several matrix metalloproteinases. These data when considered in toto suggest a novel role of MYOF in breast tumor cell invasion and a potential reversion to an epithelial phenotype upon loss of MYOF.

Myoferlin Is a Key Regulator of EGFR Activity in Breast Cancer

“…One of the most striking biologic effects observed here was the inability of breast cancer cells to respond to EGF-stimulus to migrate (MDA-MB231 and MDA-MB468) or undergo EMT (MDA-MB468). Li and colleagues (14) reported recently that MDA-MB231 underwent a spontaneous reverse EMT in the absence of myoferlin. However, similar data published by the same authors elsewhere (38) MB231 cells as shown in ref.…”

“…S5). Interestingly, Li and colleagues (14) and Eisenberg and colleagues (13) both showed that short hairpin RNA (shRNA)-mediated myoferlin depletion impairs MDA-MB231 cells' invasion; however, it has no effect on cell migration or proliferation. Our invasion and proliferation data are in agreement with the literature (13,14).…”

“…Interestingly, Li and colleagues (14) and Eisenberg and colleagues (13) both showed that short hairpin RNA (shRNA)-mediated myoferlin depletion impairs MDA-MB231 cells' invasion; however, it has no effect on cell migration or proliferation. Our invasion and proliferation data are in agreement with the literature (13,14). However, opposite to the previous findings (13,14), we show that myoferlin silencing exhibits a strong inhibitory effect on the ability of MDA-MB231 cells to migrate.…”

“…In normal myoblasts, Demonbreun and colleagues showed that myoferlin deficiency leads to a defect in insulin growth factor-like receptor (IGFR1) trafficking as well as to decreased IGFR1 signaling (12). Although increasing number of studies continue to further our understanding of myoferlin function in normal cells, to date, only little (13)(14)(15) is known concerning its role in tumor cells. Three previous studies have reported the overexpression of myoferlin at the mRNA level in lung (16) and breast cancer (17) as well as at the protein level in pancreas cancer (18).…”

Myoferlin plays a key role in VEGFA secretion and impacts tumor‐associated angiogenesis in human pancreas cancer

“…Recently, myoferlin was found to be important for breast cancer invasion. [13][14][15] Our laboratory showed that myoferlin, is a key regulator of EGFR activity in human breast cancer cells. 16 Interestingly, it was reported, in a Kaplan-Meier survival curve, that patients with myoferlin-positive PDAC had a significant lower overall survival than those with a myoferlinnegative tumor.…”