Mesenchymal Stem Cells (MSC) Promote Aggressive Behavior of Human Breast Cancer Cells (MCF-7) in Vitro- the Role Cytokines (TNF-alpha) and Chemokines

The tumor microenvironment contributes to local tumor growth and may set up a metastatic niche for breast cancer cells. We tested the effects of spontaneously transformed murine mesenchymal stem cells (stMSC; Li et al. Cancer Res 2008) on the migration, proliferation and cell cycle of the MCF-7 human breast cancer cell line.

MCF-7 cells were collected from plates held at confluence to establish cell cycle arrest and then grown either in control media (50/50 mix of fresh and conditioned MCF-7 media) or modification of stMSC conditioned media (50/50 mix of fresh and stMSC conditioned media with TNF-alpha, anti-TNF-alpha or isotype control). MCF-7 cells were plated at equal concentrations into 24-well dishes to establish near confluent plates. The MCF-7 monolayer was wounded using a pipette tip, and the area evaluated/photographed at 0, 24 and 48 hours (in triplicate). Media was changed daily. Synchronized cultures were grown in control or MSC media for 0, 24 or 48 hours in triplicates and analyzed by FACS for cell cycle status and standard cell counts. MCF-7 cells grown in MSC cultured media healed 49% (based on wound size) while control wound size was 26% healed at 24 hrs (p=0.00591). At 48 hrs, MCF-7 cells exposed to stMSC media showed 95% healing while MCF-7 cells in control media still retained 50% of the original wound size (50% healing; p=0.00002). The exposure MCF-7 grown in control media and MSC media did not differ in cell cycle progression. MSC media increased proliferation of MCF-7 cells at 24, 48 and 72 hours compared to control media. (p<0.002). In a separate experiments media from stMSC exposed to TNF-alpha led to increased healing of MCF-7 monolayer compared to stMSC conditioned media at 24 hrs (59.5% vs 44.5%; p=0.027). Healing was lower in media from stMSC cultured with anti-TNF blocking antibody compared to stMSC conditioned media at 24 hrs (66.6% vs 95.7%; p=0.002). We have also detected that stMSC conditioned media contains very high levels of TNF-alpha, MCP-1, CCL-5 and also high levels of NF-kB activity in stMSC conditioned media.

StMSCs produce factors (such as TNF-alpha) that provide breast cancer cells (MCF-7) with migration and growth advantage. Animal experiments assessing the ability stMSCs to contribute to invasion and migration of breast cancer cells are currently underway.