Interleukin-6 Expression under Gravitational Stress Due to Vibration and Hypergravity in Follicular Thyroid Cancer Cells

It is known that exposing cell lines in vitro to parabolic flights changes their gene expression and protein production patterns. Parabolic flights and spaceflight in general are accompanied by transient hypergravity and vibration, which may impact the cells and therefore, have to be considered too. To estimate the possible impact of transient hypergravity and vibration, we investigated the effects of these forces separately using dedicated ground-based facilities. We placed follicular thyroid ML-1 and CGTH W-1 cancer cells in a specific centrifuge (MuSIC Multi Sample Incubator Centrifuge; SAHC Short Arm Human Centrifuge) simulating the hypergravity phases that occur during one (P1) and 31 parabolas (P31) of parabolic flights, respectively. On the Vibraplex device, the same cell lines were treated with vibration waves corresponding to those that occur during a whole parabolic flight lasting for two hours. After the various treatments, cells were harvested and analyzed by quantitative real-time PCR, focusing on the genes involved in forming (ACTB, MYO9, TUBB, VIM, TLN1, and ITGB1) and modulating (EZR, RDX, and MSN) the cytoskeleton, as well as those encoding growth factors (EGF, CTGF, IL6, and IL8) or protein kinases (PRKAA1 and PRKCA). The analysis revealed alterations in several genes in both cell lines; however, fewer genes were affected in ML-1 than CGTH W-1 cells. Interestingly, IL6 was the only gene whose expression was changed in both cell lines by each treatment, while PKCA transcription remained unaffected in all experiments. We conclude that a PKCa-independent mechanism of IL6 gene activation is very sensitive to physical forces in thyroid cells cultured in vitro as monolayers.