Abstract 5078: Human breast carcinoma-associated mesenchymal stem cells promote breast cancer cell proliferation, irreversible EMT and invasion through Collagen I
Authors: Gonzalez Maria E. , Martin Emily E. , Kleer Celina G. 
Published: August 2015

Background: Accumulating evidence suggests that mesenchymal stem cells (MSCs) are recruited to the tumor microenvironment and play roles in tumor progression; however their specific mechanisms and functions need further investigation. In this study, we identified the presence of carcinoma-associated MSCs (CA-MSCs) isolated from breast cancer metastasis to a human lymph node (LNM) and liver (LM). We hypothesized that CA-MSCs may increase the invasive abilities of breast cancer cells and that they may enhance collagen expression to promote breast cancer progression.

Methods: We isolated CA-MSCs from fresh samples of breast cancer metastasis to a lymph node and liver obtained from the operating room. A portion of each specimen was subjected to H&E staining to confirm the diagnosis, and another portion was mechanically dissected and digested with collagenase. Red blood cells were lysed with ACK buffer and cell suspensions were cultured in Human Epithelial Medium. Once isolated, adherent CA-MSCs were subcultured in MSC medium for up to 12 passages for each experiment. CA-MSCs were subjected to multilineage differentiation assays (osteogenic, chrodrogenic, and adipogenic differentiation), and labeled with Ds-Red and co-cultured with a panel of breast cancer cells including MDA-MB-231, MCF7, DCIS.COM. We performed RT-PCR, WB, 3D proliferation assays, and invasion assays, and immunoshistochemistry. COAL1 expression was downregulated in the CA-MSCs-DsRED using specific shRNA. Control and CA-MSCs-DsRed-shCOAL1 were co-cultured with MDA-MB-231 and MCF7 breast cancer cells, and subjected to proliferation and invasion assays, and to RT-PCR and WB to investigate EMT proteins.

Results: CA-MSCs had spindle morphology, normal karyotype, were nontumorigenic, and possessed tri-lineage differentiation ability (osteoblast, adipocyte, and chondrocyte). In co-cultures, CA-MSCs promote proliferation, invasion, irreversible EMT through serial passages, compared to single cultures of breast cancer cells. CA-MSCs increased COAL1 expression and collagen 1 deposition in the 3D co-cultures by IHC and RT-PCR. COAL1 shRNA knockdown in CA-MSCs rescued the effect in proliferation and invasion of breast cancer cells in the co-cultures.

Conclusion: We successfully isolated and characterized CA-MSCs, confirming their presence in human breast cancer metastasis. We found that CA-MSCs enhance breast cancer cell proliferation, promote irreversible EMT and invasion and increased COAL1 expression and collagen 1 deposition. We demonstrated that COAL1 expression is required for the effect of CA-MSCs on breast cancer cell proliferation and invasion.

Citation Format: Maria E. Gonzalez, Emily E. Martin, Celina G. Kleer. Human breast carcinoma-associated mesenchymal stem cells promote breast cancer cell proliferation, irreversible EMT and invasion through Collagen I. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5078. doi:10.1158/1538-7445.AM2015-5078