The long non-coding RNA cytoskeleton regulator (CYTOR) sponges microRNA-206 (miR-206) to promote proliferation and invasion of HP75 cells

Background: The role and mechanism of long non-coding RNA cytoskeleton regulator (CYTOR) in invasive pituitary adenomas (IPA) has not been elucidated previously. Objective: This study aimed to investigate the interaction between CYTOR and miR-206 and their roles in IPA using HP75 cells as the model. Methods: The expression levels of CYTOR and miR-206 were detected by quantitative real-time polymerase chain reaction (qRT-PCR) in IPA tissues and cell lines. The Chi-square test was used to analyze the correlation between CYTOR expression and clinical-pathological parameters. HP75 cell proliferation was detected by Cell Counting Kit-8 assay and colony formation assay. Scratch healing experiments and Transwell assay were used to detect migration and invasion of HP75 cells. The relationship between CYTOR and miR-206 was predicted by bioinformatics and verified by qRT-PCR and dual-luciferase reporter gene method. Result: CYTOR is up-regulated in IPA tissues and cell lines. The high expression of CYTOR is associated with adenoma invasiveness and adenoma size of the patients. Down-regulation of CYTOR decreases the proliferation, migration and invasion of HP75 cells, while up-regulation of miR-206 can inhibit proliferation, migration and invasion of HP75 cells. MiR-206 is identified as a target of CYTOR and could be negatively regulated by it in IPA. Discussion: CYTOR, as a tumor-promoting factor, facilitates the proliferation, migration and invasion of HP75 cells through sponging miR-206. Conclusion: The CYTOR-miR-206 axis provides new insights into the diagnosis and treatment of IPA.

Overexpression of Wild-Type Activin Receptor Alk4-1 Restores Activin Antiproliferative Effects in Human Pituitary Tumor Cells

Activin is a member of the TGFβ family of cytokines involved in the control of cell proliferation. We have previously shown that the majority of clinically nonfunctioning pituitary tumors do not respond to activin-induced growth suppression. Human pituitary tumors specifically express alternatively spliced activin type I receptor Alk4 mRNAs, producing C-terminus truncated isoforms designated Alk4-2, 4-3, and 4-4. However, it is not known whether these truncated activin receptors suppress activin effects on cell proliferation in human pituitary cells. Therefore, we investigated activin signaling in a human pituitary tumor cell line, HP75, derived from a clinically nonfunctioning pituitary tumor. HP75 cells express activin A mRNA and secrete activin A, as measured by ELISA and a functional bioassay. TGFβ administration decreases the proliferation of HP75 cells, suggesting that the signaling pathway shared by TGFβ and activin is functional in this cell line. However, activin neither inhibits cell proliferation nor stimulates reporter gene expression in HP75 cells, indicating that activin signaling is specifically blocked at the receptor level. HP75 cells express all truncated activin type I receptor Alk4 isoforms, as determined by RT-PCR. Because truncated Alk4 receptor isoforms inhibit activin signaling by competing with the wild-type receptor for binding to activin type II receptors, we hypothesized that overexpression of wild-type activin type I receptor will restore activin signaling. In HP75 cells, cotransfection of the wild-type activin type I receptor Alk4-1 expression vector increases activin-responsive reporter activity. Furthermore, transfection with wild-type activin receptor type I results in activin-mediated suppression of cell proliferation. These data indicate that truncated Alk4 isoforms interfere with activin signaling pathways and thereby may contribute to uncontrolled cell growth. Overexpression of the wild-type Alk4-1 receptor restores responsiveness to activin in human pituitary tumor-derived cells.