Daily application of low magnitude mechanical stimulus inhibits the growth of MDA-MB-231 breast cancer cells in vitro

Abstract

IntroductionMechanical loads can regulate cell proliferation and differentiation at various stages of development and homeostasis. However, the extension of this regulatory effect of mechanical loads on cancer cells is largely unknown. Increased physical compliance is one of the key features of cancer cells, which may hamper the transmission of mechanical loads to these cells within tumor microenvironment. Here we tested whether brief daily application of an external low magnitude mechanical stimulus (LMMS), would impede the growth of MDA-MB-231 aggressive type breast cancer cells in vitro for 3 wks of growth.MethodsThe signal was applied in oscillatory form at 90 Hz and 0.15 g, a regimen that would induce mechanical loads on MDA-MB-231 cells via inertial properties of cells rather than matrix deformations. Experimental cells were exposed to LMMS 15 min/day, 5 days/week in ambient conditions while control cells were sham loaded. Cell proliferation, viability, cycle, apoptosis, morphology and migration were tested via Trypan Blue dye exclusion, MTT, PI, Annexin V, Calcein-AM and phalloidin stains and scratch wound assays.ResultsCompared to sham controls, daily application of LMMS reduced the number and viability of cancerous MDA-MB-231 cells significantly after first week in the culture, while non-cancerous MCF10A cells were found to be unaffected. Flow cytomety analyses suggested that the observed decrease for the cancer cells in the LMMS group was due to a cell cycle arrest rather than apoptosis. LMMS further reduced cancer cell circularity and increased cytoskeletal actin in MDA-MB-231 cells.ConclusionCombined, results suggest that direct application of mechanical loads negatively regulate the proliferation of aggressive type cancer cells. If confirmed, this non-invasive approach may be integrated to the efforts for the prevention and/or treatment of cancer.

Mechanical Suppression of Breast Cancer Cell Invasion and Paracrine Signaling Requires Nucleo-Cytoskeletal Connectivity

“…In one study, fluid shear increased apoptosis 631 in several tumor cell types, while no negative effects of shear were found in non-tumor 632 cells (Lien et al, 2013). In another study, daily application of LIV increased apoptosis of MDA-633 MB-231 cells (Olcum and Ozcivici, 2014). We did not observe increased cell death directly 634 following LIV; however, LIV increased expression of the membrane death receptor FAS, 635 resulting in increased Fas ligand-mediated apoptosis following LIV.…”

Biomechanical Regulation of Breast Cancer Metastasis and Progression

“…However, in another study in hepatocellular liver carcinoma cells in which the cells were exposed to shear stress from orbital shaking, there was increased cell death with cisplatin treatment in combination with shear stress (35). In MDA-MB-231 cells, 15 minutes of vibrational stresses per day also reduced proliferation (12). While compressive stress was found to enhance invasion in several cancer cell lines including the MDA-MB-231 cell line (8).…”

“…Thus, there are a rich variety of mechanical conditions within the breast tissue normally and these forces act on tumors that form within the tissue, potentially altering the course of the disease. Studies of the role of applied forces in regulating breast cancer support that compressive forces may enhance invasiveness (8) but may also suppress proliferation (12,13). However, the understanding of how applied mechanical forces alter breast cancer progression and metastasis remain poorly understood and therapies that can target these potentially powerful effects are lacking.…”

Mechanical signals inhibit growth of a grafted tumorin vivo: Proof of Concept

“…Three-dimensional (3D) culture systems have allowed the study of growth and apoptosis. It has been shown, for instance, that pressure applied to a tumor in vitro in different experimental setups delays tumor growth by changing cell death (apoptosis) and cell division in space and time (19)(20)(21)(22)(23). The first demonstration of the action of stress (surface tension) on the phenotype of a breast acinus was reported in 2005 (19).…”

“…The first demonstration of the action of stress (surface tension) on the phenotype of a breast acinus was reported in 2005 (19). Others have shown the effect of osmotic pressure or compressive stress on a spheroid (20)(21)(22) or the effect of gravity on cells in a 2D cell culture (23). In those experiments, pressure was applied on tissue externally by modifying the environment that was then considered as being equivalent to the ECM.…”