The Importance of Caveolin-1 as Key-Regulator of Three-Dimensional Growth in Thyroid Cancer Cells Cultured under Real and Simulated Microgravity Conditions

Abstract

We recently demonstrated that the CAV1 gene was down-regulated, when poorly differentiated thyroid FTC-133 cancer cells formed spheroids under simulated microgravity conditions. Here, we present evidence that the caveolin-1 protein is involved in the inhibition of spheroid formation, when confluent monolayers are exposed to microgravity. The evidence is based on proteins detected in cells and their supernatants of the recent spaceflight experiment: “NanoRacks-CellBox-Thyroid Cancer”. The culture supernatant had been collected in a special container adjacent to the flight hardware incubation chamber and stored at low temperature until it was analyzed by Multi-Analyte Profiling (MAP) technology, while the cells remaining in the incubation chamber were fixed by RNAlater and examined by mass spectrometry. The soluble proteins identified by MAP were investigated in regard to their mutual interactions and their influence on proteins, which were associated with the cells secreting the soluble proteins and had been identified in a preceding study. A Pathway Studio v.11 analysis of the soluble and cell-associated proteins together with protein kinase C alpha (PRKCA) suggests that caveolin-1 is involved, when plasminogen enriched in the extracellular space is not activated and the vascular cellular adhesion molecule (VCAM-1) mediated cell–cell adhesion is simultaneously strengthened and activated PRKCA is recruited in caveolae, while the thyroid cancer cells do not form spheroids.

Key Proteins Involved in Spheroid Formation and Angiogenesis in Endothelial Cells After Long-Term Exposure to Simulated Microgravity

“…PAI-1 is mainly produced by ECs, but is also secreted by other cells, e.g. thyroid cancer cells [59]. PAI-1 is involved in cancer angiogenesis, metastasis and promotes angiogenesis by stimulating EC migration toward fibronectin [60].…”

Cytokine Release and Focal Adhesion Proteins in Normal Thyroid Cells Cultured on the Random Positioning Machine

“…For the analysis, SwissProt numbers of the investigated proteins were entered and networks built by the software based on relationships and processes from the literature, PubMed, databases and experimental data [9, 10, 33]. …”

“…Earlier experiments have shown that human thyroid cancer cells exhibit changes in the secretion of growth factors and cytokines, as well as alterations in the factors involved in 3D growth, in the cytoskeleton, and in the extracellular matrix composition when cultured in a an RPM [10, 20, 21]. Furthermore, human thyroid cells may exhibit two phenotypes in s-µ g either in the form of multicellular spheroids (MCS) or as adherent monolayer (AD) cells [20, 21].…”

Expression and significance of caveolin‑1 in hepatitis B virus‑associated hepatocellular carcinoma

“…Previous results have demonstrated that Cav-1 is a growth-inhibitory protein that may act as a tumor suppressor (8,9). Cav-1 expression is downregulated in some forms of cancer, including mesenchymal tumors and sarcomas (8,10); however, in other cancer types; for example, oral squamous cell carcinoma, Cav-1 expression is high (11,12). These findings suggest that Cav-1 has multiple actions in human cancer cells.…”