# Effect of CircCCND1 on the Malignant Biological Behaviors of H446 Lung Cancer Cells by Regulating the MiR-340-5p/TGIF1 Axis

## TL;DR

This study shows that CircCCND1 promotes lung cancer cell growth and spread by controlling the miR-340-5p/TGIF1 pathway.

## Contribution

The novel finding is that CircCCND1 regulates lung cancer cell behavior through the miR-340-5p/TGIF1 axis.

## Key findings

- CircCCND1 is overexpressed in H446 lung cancer cells compared to normal cells.
- Knocking down CircCCND1 or increasing miR-340-5p reduces cancer cell proliferation, migration, and invasion.
- miR-340-5p targets TGIF1, and CircCCND1 regulates this interaction.

## Abstract

肺癌是常见的肺部恶性肿瘤，探究肺癌发生发展的分子机制是当前研究的热点。环状RNA细胞周期蛋白D1（circular RNA Cyclin D1, CircCCND1）在肺癌中高表达，可能是治疗肺癌的潜在靶点。本研究旨在探讨CircCCND1调节miR-340-5p/转化生长因子β诱导因子同源框1（transforming growth factor β-induced factor homeobox 1, TGIF1）轴对肺癌细胞恶性生物学行为的影响。

检测人正常肺上皮细胞BEAS-2B及人肺癌H446细胞中CircCCND1、miR-340-5p及TGIF1 mRNA表达。将体外培养的H446细胞分为对照组、CircCCND1 siRNA组、miR-340-5p mimics组、阴性对照组、CircCCND1 siRNA+miR-340-5p inhibitor组，检测细胞增殖、线粒体膜电位、凋亡、迁移和侵袭情况，以及各组细胞CircCCND1、miR-340-5p、TGIF1 mRNA、BCL2相关X蛋白（BCL2-associated X protein, Bax）、剪切的半胱天冬氨酸蛋白酶3（cleaved Caspase-3）、N-钙黏蛋白（N-cadherin）、E-钙黏蛋白（E-cadherin）、TGIF1蛋白表达，并验证miR-340-5p与CircCCND1、TGIF1的靶向关系。

与BEAS-2B细胞相比，H446细胞CircCCND1、TGIF1 mRNA升高，miR-340-5p表达降低（P<0.05）。敲低CircCCND1或上调miR-340-5p表达可抑制H446细胞增殖、迁移、侵袭，降低TGIF1 mRNA和TGIF1蛋白表达，促进细胞凋亡；下调miR-340-5p可拮抗敲低CircCCND1对H446肺癌细胞恶性生物学行为的抑制作用。CircCCND1可能靶向下调miR-340-5p，miR-340-5p可能靶向下调TGIF1。

敲低CircCCND1可抑制肺癌H446细胞恶性行为，其作用可能是通过调控miR-340-5p/TGIF1轴实现的。

Primers sequence

Expression levels of CircCCND1 and miR-340-5p, and relative expression levels of TGIF1 mRNA in each cell (Mean±SD, n=6)

Expressions of CircCCND1, miR-340-5p and TGIF1 mRNA in each group (Mean±SD, n=6)

Proliferation rate, mitochondrial membrane potential and apoptosis rate of H446 cells in each group (Mean±SD, n=6)

Migration ratio and invasion number of H446 cells in each group (Mean±SD, n=6)

Relative expression of EMT-related protein and TGIF1 protein in H446 cell apoptosis in each group (Mean±SD, n=6)

Relative luciferase activity in each group (Mean±SD, n=6)

Relative luciferase activity in each group (Mean±SD, n=6)