Department of Biomedical Engineering, Cornell University, Weill Hall, NY 14853, USA.
Biomaterials. 2012 Dec;33(35):9037-48. doi: 10.1016/j.biomaterials.2012.08.052. Epub 2012 Sep 17.
Hematogenous metastasis involves a glycoprotein mediated adhesion cascade of tumor cells with E-selectin on the endothelial layer of the blood vessels. Cell-cell interactions play a major role in cancer metastasis and invasiveness. Intercellular communication between two cancer cells or between a cancer cell with a stromal cell in the microenvironment such as fibroblasts or inflammatory cells play an important role in metastatic invasion. Culturing tumor cells as 3D spheroids can recapitulate these physiologically relevant cell-cell interactions. The heterogeneity in primary tumors is attributed to cell subpopulations with varying degree of invasiveness. Co-culturing cancer cells with different phenotypes as 3D spheroids can mimic this heterogeneity. Here we report the effect of homotypic and heterotypic interactions in breast cancer cells cultured as 3D spheroids on polydimethylsiloxane (PDMS) on the adhesion phenotype to E-selectin. We show that breast cancer cell lines (BT20 and MCF7) propagating as 3D spheroids on PDMS exhibit a stronger interaction with human recombinant E-selectin when compared to their respective monolayer grown counterparts on tissue culture plate (TCP). Matrigel invasion assay also indicated that BT20 and MCF7 spheroids were more invasive than BT20 and MCF7 cells grown as monolayers. To mimic tumor heterogeneity in vitro, a co-culture model included tumorigenic cell lines BT20, MCF7 and a non-tumorigenic mammary epithelial cell line MCF10A. These cell lines were cultured together in equal seeding ratio on PDMS to generate co-culture spheroids. The heterotypic interactions in the co-culture model resulted in enhancement of the adhesion of the most invasive BT20 cell line to E-selectin. BT20 cells in co-culture bound to the greatest degree to soluble E-selectin compared to MCF7 and MCF10A cells in co-culture. Co-invasion assay with co-culture spheroids indicated that BT20 cells in co-culture were more invasive than MCF7 and MCF10A cells. The results presented here indicate that homotypic and heterotypic interaction of cancer cells favor adhesion to E-selectin thus representing a complexity beyond planar cell culture. Also, when cells of different phenotypes are mixed, the heterogeneity enhances the adhesive phenotype and invasiveness of the most invasive cell population. The results challenge the classic use of planar cell culture for evaluating the adhesion of cancer cells to E-selectin and establish our co-culture technique as a model that can help investigative studies in metastasis and invasiveness of breast and other types of cancers.
血行转移涉及肿瘤细胞与血管内皮层上的 E-选择素的糖蛋白介导的黏附级联。细胞-细胞相互作用在癌症转移和侵袭中起着重要作用。两种癌细胞之间或癌细胞与微环境中的成纤维细胞或炎症细胞等基质细胞之间的细胞间通讯在转移性侵袭中起着重要作用。将肿瘤细胞培养为 3D 球体可以再现这些生理相关的细胞-细胞相互作用。原发性肿瘤的异质性归因于具有不同侵袭程度的细胞亚群。将不同表型的癌细胞共培养为 3D 球体可以模拟这种异质性。在这里，我们报告了乳腺癌细胞作为 3D 球体在聚二甲基硅氧烷 (PDMS) 上培养时的同质和异质相互作用对 E-选择素黏附表型的影响。我们表明，与各自在组织培养板 (TCP) 上生长的单层相比，在 PDMS 上增殖的乳腺癌细胞系 (BT20 和 MCF7) 作为 3D 球体培养时与重组人 E-选择素的相互作用更强。Matrigel 侵袭试验也表明，BT20 和 MCF7 球体比作为单层生长的 BT20 和 MCF7 细胞更具侵袭性。为了在体外模拟肿瘤异质性，共培养模型包括致瘤细胞系 BT20、MCF7 和非致瘤乳腺上皮细胞系 MCF10A。这些细胞系以相等的接种比例一起在 PDMS 上培养以生成共培养球体。共培养模型中的异质相互作用导致最具侵袭性的 BT20 细胞系与 E-选择素的黏附增强。与共培养中的 MCF7 和 MCF10A 细胞相比，BT20 细胞在共培养中与可溶性 E-选择素的结合程度最大。共培养球体的共侵袭试验表明，BT20 细胞在共培养中的侵袭性强于 MCF7 和 MCF10A 细胞。这里呈现的结果表明，癌细胞的同质和异质相互作用有利于与 E-选择素的黏附，从而代表了超越平面细胞培养的复杂性。此外，当不同表型的细胞混合时，异质性增强了最具侵袭性细胞群体的黏附表型和侵袭性。这些结果挑战了使用平面细胞培养来评估癌细胞与 E-选择素的黏附的经典方法，并确立了我们的共培养技术作为一种模型，可以帮助研究乳腺癌和其他类型癌症的转移和侵袭。
