Leading malignant cells initiate collective epithelial cell invasion in a three-dimensional heterotypic tumor spheroid model

Abstract

Solid tumors consist of genetically and phenotypically diverse subpopulations of cancer cells with unique capacities for growth, differentiation, and invasion. While the molecular and microenvironmental bases for heterogeneity are increasingly appreciated, the outcomes of such intratumor heterogeneity, particularly in the context of tumor invasion and metastasis, remain poorly understood. To study heterotypic cell-cell interactions and elucidate the biological consequences of intratumor heterogeneity, we developed a tissue-engineered multicellular spheroid (MCS) co-culture model that recapitulates the cellular diversity and fully three-dimensional cell-cell and cell-matrix interactions that characterize human carcinomas. We found that “invasion-competent” malignant cells induced the collective invasion of otherwise “invasion-incompetent” epithelial cells, and that these two cell types consistently exhibited distinct leader and follower roles during invasion. Analysis of extracellular matrix microarchitecture revealed that malignant cell invasion was accompanied by extensive extracellular matrix remodeling including matrix alignment and proteolytic track-making. Inhibition of cell contractility- and proteolysis-mediated matrix reorganization prevented leader-follower behavior and malignant cell-induced epithelial cell invasion. These results indicate that heterogeneous subpopulations within a tumor may possess specialized roles during tumor progression and suggest that complex interactions among the various subpopulations of cancer cells within a tumor may regulate critical aspects of tumor biology and affect clinical outcome.

Illuminating breast cancer invasion: diverse roles for cell–cell interactions

“…Multiple studies demonstrate that intrinsic differences in invasive motility between tumor cells affect the leader follower arrangement of collectively invading cancer cells [111,112]. For example, MT1-MMP expressing breast cancer cells generate micro-tracks that enable migration of trailing cancer cells, and collective invasion is abolished when MT1-MMP-mediated proteolysis is disrupted [112].…”

Measurement of dynamic cell-induced 3D displacement fields in vitro for traction force optical coherence microscopy

“…It has been shown that mechanical cues, such as substrate stiffness or local stresses, have bearing on cellular behavior in many contexts [1][2][3][4][5][6]. For example, it has been shown that extracellular matrix (ECM) stiffness can promote the onset and progression of cancer [7][8][9][10], and that metastatic cancer cells exert greater traction forces than their healthy counterparts [11].…”

Oriented collagen fibers direct tumor cell intravasation

“…The reason for that is mainly because precise quantification of reorganized collagen tissue in vivo is significantly restricted by existing methods. Therefore, in vitro 3D models have been constructed to build linear oriented matrices in microchannels by mechanical strain and have demonstrated that 3D matrix alignment facilitates persistent migration of tumor cells (9,(19)(20)(21)(22). For example, Jimenez Valencia et al studied cell behaviors in and around spheroids, which could be regarded as a tumor model at an early stage of the intravasation process.…”