Adaptation of Non-Invasive Cancer Cells to 3D Collagen I Microenvironment Induces Transcriptional Reprogramming Accompanied by a More Complex RNA Landscape

Nowadays, most cancer research still depends on traditional cell culture in Petri dishes or cell culture flasks which do not have the ability to mimic physiological-like conditions in vitro. However, the behavior of cancer cells strongly relies on the interaction with their extracellular microenvironment. Consequently, current advanced approaches focus on three-dimensional (3D) cell culture to overcome such limitations and to enable a better understanding of fundamental processes including cancer development, progression, apoptosis and invasion. However, transcriptional adaptation to and temporal stability within an in vitro 3D microenvironment still appear to be remarkably understudied. In our study, we compared the cellular behavior and whole transcriptome gene expression of three frequently used non-invasive cancer cell lines (HCT-116, A549 and T47D), embedded within a collagen I (Coll I)-based 3D microenvironment to its counterparts grown as simple monolayers in a time-dependent manner. Thereby, changes in morphology and doubling time became apparent between both cultivation systems, and RNA sequencing-based transcriptome-wide analysis revealed a remarkable increase in transcriptional complexity under 3D conditions. In line with the 3D-dependent phenotype, unidirectional shifts for genes involved in cell cycle regulation (e.g., CCNB1, CCNB2), cell–matrix interaction (e.g., ADAM8, ITGA2) and metabolic signaling (e.g., HK2, ENO2) were identified over time, being either activated or repressed. Interestingly, all three cell lines cultured in Coll I matrices displayed a highly distinct RNA content and composition, along with a significantly increased number of expressed protein-coding genes (increase of 3–6%) as well as long non-coding RNAs (increase of 26–48%), suggesting a more multifaceted transcription profile under 3D conditions. Our work clearly highlights that an in vitro 3D Coll I-based cell culture system has an incisive cell-specific impact on the whole transcriptome on a qualitative and quantitative level. This tremendous transcriptional reprogramming implies essential changes in gene regulatory networks and affects phenotypic cancer cell behavior, which should be considered when focusing on downstream applications.