Abstract B73: Activin A and activin C have opposing effects on pathways involved in cancer progression in Ovcar3 cells
Authors: Reader Karen L. , Mottershead David G. , Nicholson Helen D. 
Published: August 2018

Activins are members of the transforming growth factor-β (TGFB) family that play important roles in the development, growth, and function of the ovary. These proteins consist of dimers and hetero-dimers of inhibin-βA, -βB, and -βC subunits that form activin A, B, C, AB, or AC. The few studies that have examined the effects of activin A on ovarian cancer cell growth have produced conflicting results, with some showing stimulation and others inhibition of growth in the same cell lines. Little has been published on the function of activin C. Mice lacking inhibin develop ovarian granulosa cell tumors that secrete increased amounts of activin A; they also develop cachexia. Overexpression of activin C in these mice inhibits the growth of these tumors and prevents cachexia development, possibly by inhibiting activin A signaling.

We hypothesized that activin C would inhibit the effects of activin A on proliferation in epithelial ovarian cancer cell lines. The objectives of our study were a) to determine the effect of activin A, activin C, or activin A and C in combination on epithelial ovarian cancer cell proliferation and b) to identify the downstream pathways altered by activin treatment. Ovcar3 cells were treated with and without different concentrations of recombinant activin A, activin C, and activin A and C together for 96h and proliferation was measured using the CellTiter 96 MTS cell proliferation assay in replicate wells in 5 to 6 different cell passages. Following treatment for 18h, RNA was isolated from Ovcar3 cells from three separate passages and gene expression changes were measured with the NanoString PanCancer Pathway Code Set.

Activin A at both 10ng/ml (P &lt; 0.05) and 50ng/ml (P &lt; 0.0001) inhibited proliferation in Ovcar3 cells, as did activin C at 100ng/ml (P &lt; 0.01). The combination of activin A + C inhibited growth of the cells (P &lt; 0.0001), but this was not significantly different to the effect of activin A alone. NanoString analysis revealed the number of genes that were significantly differentially expressed (Benjamini-Yekutieli p-value adjusted) with a log2 fold change greater than 0.5 or less than -0.5 was 34, 10, and 40 for activin A, activin C, and activin A + C treatment, respectively. NanoString directed global significance gene set analysis revealed activin A treatment upregulated the TGFB pathway along with gene pathways commonly misregulated in cancer, while the DNA repair and chromatin modulation pathways were downregulated by activin A. This suggests a potential pro-oncogenic role for activin A. In contrast, activin C downregulated the TGFB and Hedgehog pathways, upregulated chromatin modulation, and had a small positive effect on the DNA repair pathway. When Ovcar3 cells were treated with both activin A and C, pathway regulation was generally similar to that of activin A alone (with slightly higher scores), except for chromatin modulation, which was upregulated, as with activin C treatment. In conclusion, activin A and activin C have opposing effects on several pathways known to be important in the progression of cancer. We believe that activin C has potential as a therapeutic agent for the treatment of ovarian cancer, and further research to better understand the role of activin C in ovarian cancer progression is warranted.

Citation Format: Karen L. Reader, David G. Mottershead, Helen D. Nicholson. Activin A and activin C have opposing effects on pathways involved in cancer progression in Ovcar3 cells. [abstract]. In: Proceedings of the AACR Conference: Addressing Critical Questions in Ovarian Cancer Research and Treatment; Oct 1-4, 2017; Pittsburgh, PA. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(15_Suppl):Abstract nr B73.