Abstract: Objective To investigate the effects of long non-coding RNA LAMTOR5-AS1 (LncRNA LAMTOR5-AS1) on the malignant biological behaviors of colorectal cancer (CRC) cells through targeted regulation of the microRNA-28-5p (miR-28-5p)/agmatinase (AGMAT) signaling axis. Methods The expression levels of LncRNA LAMTOR5-AS1, miR-28-5p, and AGMAT mRNA were detected in CRC tissues, adjacent non-tumor tissues, CRC cell lines (HCT116, SW480, Lo Vo), and human normal colonic epithelial cells (NCM460).HCT116 cells were divided into the si-NC, si-LAMTOR5-AS1, miR-NC, miR-28-5p mimics, si-LAMTOR5-AS1+inhibitor NC, and si-LAMTOR5-AS1+miR-28-5p inhibitor.In each group, the expression levels of LncRNA LAMTOR5-AS1, miR-28-5p and AGMAT mRNA were detected by real-time quantitative reverse transcription PCR (RT-qPCR); cell viability was assessed by CCK-8 assay; cell migration and invasion were evaluated by wound healing assay and Transwell assay, respectively; cell apoptosis was measured by flow cytometry; and the protein expression levels of AGMAT, Ki67, Cleaved caspase-3, E-cadherin and MMP9 were determined by Western blot.The targeted relationships between miR-28-5p and LncRNA LAMTOR5-AS1 or AGMAT were verified.A subcutaneous xenograft tumor model in nude mice was established, and the animals were divided into si-NC and si-LAMTOR5-AS1 groups.Tumor growth and the expression levels of LncRNA LAMTOR5-AS1, miR-28-5p and AGMAT mRNA were examined. Results LncRNA LAMTOR5-AS1 and AGMAT mRNA were upregulated, while miR-28-5p was downregulated in CRC tissues and cell lines.Silencing LncRNA LAMTOR5-AS1 or overexpressing miR-28-5p significantly reduced HCT116 cell viability, proliferation, migration, and the protein expression of AGMAT, Ki67 and MMP9, while increasing the apoptosis rate and the protein expression of Cleaved caspase-3 and E-cadherin (P<0.05).Simultaneous silencing of LncRNA LAMTOR5-AS1 and downregulation of miR-28-5p reversed the effects of si-LAMTOR5-AS1, as evidenced by increased protein expression of AGMAT, Ki67 and MMP9, decreased apoptosis rate and reduced Cleaved caspase-3 and E-cadherin expression, thereby attenuating the inhibitory effects of si-LAMTOR5-AS1 on HCT116 cell viability, proliferation and migration (P<0.05).In vivo experiments demonstrated that silencing LncRNA LAMTOR5-AS1 suppressed the growth of xenograft tumors in nude mice. Conclusion Silencing LncRNA LAMTOR5-AS1 inhibits HCT116 cell proliferation, migration and tumor growth through targeted regulation of the miR-28-5p/AGMAT signaling axis.

Key words: long non-coding RNA LAMTOR5-AS1, colorectal cancer cells, malignant biological behaviors, microRNA285p (miR285p)/agmatinase (AGMAT) signaling axis