CircASAP1 promotes the development of cervical cancer through sponging miR-338-3p to upregulate RPP25.

Circular RNAs have been identified as vital regulators to regulate the development of human cancers, including cervical cancer. Therefore, this study was designed to clarify the underlying mechanism of circASAP1 in cervical cancer. The real-time quantitative PCR assay was applied to quantify the expression levels of circASAP1, microRNA (miR)-338-3p, and ribonuclease P and MRP subunit p25 (RPP25) in cervical cancer tissues and cells. The cell proliferation ability was measured by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl-2H-tetrazol-3-ium bromide and colony-forming assays. The protein expression levels of cyclin D1, proliferating cell nuclear antigen, and RPP25 were assessed by western blot assay. Flow cytometry assays were used to determine the apoptosis and cell cycle distribution of cervical cancer cells. The transwell assay was employed to test the migration and invasion abilities of cervical cancer cells. The interaction relationship between miR-338-3p and circASAP1 or RPP25 was confirmed by dual-luciferase reporter assay and RNA pull-down assay. The xenograft experiment was established to clarify the functional role of circASAP1 inhibition in vivo. CircASAP1 was overexpressed in cervical cancer tissues and cells compared with negative groups. Additionally, the loss-of-functional experiments implied that knockdown of circASAP1 impeded proliferation, migration, and invasion while induced apoptosis and cell cycle arrest in cervical cancer cells along with repressed tumor growth in vivo through regulation of miR-338-3p. In addition, RPP25 was a target mRNA of miR-338-3p, and overexpression of miR-338-3p suppressed proliferation, migration, and invasion while induced apoptosis and cell cycle arrest in cervical cancer cells by suppressing RPP25 expression. Mechanistically, circASAP1 could function as a sponge for miR-338-3p to increase the expression of RPP25, and further regulated proliferation, migration, invasion, apoptosis, and cell cycle program of cervical cancer cells, which might be potential markers for cervical cancer diagnosis.

A novel genetic- and cell-based tool for assessing the efficacy and toxicity of anticancer drugs in vitro.

AIMS: To develop an in vitro tool for assessing the efficacy and toxicity of anticancer drugs using mixed culture containing both tumor and non-tumor cells. Such in vitro tool should have high application potential in drug-screening and personalized cancer care. METHODS: Fibroblasts were spiked as non-tumor cells into tumor cells of an established line. The mixed culture was treated with a test drug at various concentrations. After the treatment, DNA was prepared directly from the survived adhesive cells in the wells of the 96-well plates using a simple and inexpensive method, and subjected to digital PCR for measuring relative copy numbers of a target gene NF1 to that of a reference gene RPP30. The NF1 gene is known to be heterozygously deleted in these tumor cells while the RPP30 gene has two copies in both tumor and non-tumor cells. Using the NF1/ RPP30 ratios resulting from the dual digital PCR assay, the proportions of tumor cells were calculated for each drug concentration. RESULTS: Digital PCR confirmed that the tumor cells have only one copy of the NF1 gene while the non-tumor fibroblasts have two copies. By contrast, both types of cells have two copies of the reference gene RPP30. Using the ratio of the two genes, we successfully calculated the proportion of tumor cells which decreased as the dose of the test drug increased up to a certain concentration, indicating that the drug is more effective for the tumor cells than for the non-tumor cells in this dose-range. At the highest dose, we observed a slight increase in the proportion of tumor cells, likely reflecting the toxic effect of the drug on both tumor and non-tumor cells. CONCLUSION: This pilot study demonstrated the feasibility of a genetic- and cell-based tool for testing efficacy and toxicity of anticancer drugs in vitro. The promising results suggest that additional efforts are merited, for further development since such a tool will likely have high application potential (1) in drug discovery where it enables simultaneously assessing therapeutic effect on target cells and toxic effect on non-target cells, and (2) in personalized adjuvant chemotherapy where multiple drugs can be tested in primary cultures derived from surgically removed tumor.