Cells detect signals from their microenvironment and respond accordingly, impacting signal transduction and gene expression. This further leads to modulating cellular activities such as proliferation, migration and differentiation. Such cellular dynamics are particularly prominent in embryonic development and cancer. Using these two contexts, we study the cellular and molecular mechanisms whereby the cellular microenvironment regulates cell growth and fate.

Embryo development

Embryogenesis is precisely controlled by various processes including gene expression, cell-cell interaction, cell differentiation and migration. Our current study focuses on genetic diseases, especially spliceosome syndromes which cause congenital skeletal abnormalities. Despite the requirement for the precise function of the spliceosome in all cells, mutations in the splicing machinery cause abnormal development only in specific tissues. One of the spliceosomal proteins, encoded by  SNRPB, is a core component of the major spliceosomal particles. Mutations in SNRPB are responsible for the Cerebro-cost-mandibular syndrome (Tooley et al., 2016 Am J Med Gen). We demonstrated that the expression of SNRPB is not ubiquitous during embryonic development, the loss-of-function affects chondrogenesis and osteogenesis in virto, and it modulates the Wnt and BMP pathways (Knill et al., 2024 FEBS J; Turner et al. 2023 Dev Dyn; Turner et al. 2020 J Anat). We also discussed the clinical phenotype of the syndrome in the anatomical aspect (Keeling et al. 2024 Clin Anat).

Figure 1. In vivo embryo studies. (A) A 2-day-old chick embryo. Beads soaked with proteins or chemical compounds were applied in the region indicated by the red arrow for further analysis. (B) An 8-day-old chick embryo was stained for cartilage with alcian blue, following the application of Dkk1 (a Wnt signal inhibitor) beads as shown in A. Arrows indicate proximal rib defects caused by the Wnt inhibitor. (Turner & Itasaki, DOI: 10.1111/joa.13144))

Impact of cancer microenvironment on stemness

The cellular microenvironment and the subsequent cell architecture have a profound impact on the way how cells receive signals and interpret them. One example is that Wnt/β-catenin signal transduction differs significantly depending on the epithelial or mesenchymal morphology  (Howard et al. 2011 PLoS One). Another example is whether the cells are on a stiff or soft scaffold. These are the key to understanding how complex tissues such as developing embryos as well as adult tissues in normal and pathological conditions, regulate cellular activities. To investigate the scaffold-dependent and independent growth differences, we employ a newly developed liquid-culture system (Abe-Fukasawa et al. 2018 Sci Rep). We demonstrated that cancer spheroids exhibit suppressed PI3K/Akt pathway activities when grown in the liquid without a scaffold of extracellular matrices (Abe-Fukasawa et al. 2021 FEBS J). Our current study is on the impact of such physical microenvironment in cancer spheroids on the acquisition of stemness features, that are clinically important in drug resistance and tumour relapse. 

Figure 2. Cancer spheroids in vitro. Breast cancer cells MCF7 were grown in 3D to form spheroids in vitro, in the gel matrix (A) or medium (B), and stained for p-Ezrin (green, marking apical cell membrane), β1-Integrin (red, marking basal cell membrane) and nuclei (blue). In the spheroid grown in the gel matrix (A), the basal membrane is outward-facing, whereas the liquid-cultured spheroid (B) shows the apical membrane on the surface. (Abe-Fukasawa et al., DOI: 10.1111/febs.15867)

Interaction of cancer cells with non-cancerous cells

Some years ago we developed a time-lapse monitoring of cell-cell interaction in 3D (Ivers et al. 2014 Cancer Cell Int; Scholz and Itasaki, 2016 Methods Mol Biol). We revealed that spheroids move dynamically in the matrix by spinning and rotating, like the earth rotates on its axis while orbiting. Furthermore, when cancer cells encounter non-cancer (normal) cells, cancer cells show aggressive behaviour leading to the engulfing and killing of non-cancer cells. The effective attacking depends on the ratio of cancerous and non-cancer cell populations: when cancer cells are dominant, they effectively cooperate to attack non-cancer cells, whereas a minority of cancer cells do not effectively kill non-cancer cells. We are now applying this method to the interaction between cancer cells and immune cells, aiming to elucidate the mechanism that impacts the efficacy of cancer immunotherapy. 

Figure 3. Interaction of cancer cells with non-cancerous cells. Co-culture of MDCK (red, epithelial, non-cancerous) and MDA-MB-231 (green, breast cancer) cell spheroids were grown in the 3D gel matrix. The two red spheroids are engulfed by highly motile green cancer cells. For time-lapse movies, see Ivers et al., DOI: 10.1186/s12935-014-0108-6.