Background Gastric carcinogenesis is a multifactorial and complex process, in which long non-coding RNAs (lncRNAs) play important roles as oncogenes or antioncogenes. Research has found that the expression of lncRNA LINC02859 is down-regulated in gastric cancer tissues and correlated with the degree of tumor differentiation and TNM stage, and also plays an important role in the development of malignant transformation of cells induced by environmental carcinogen N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), but its mechanism of action is still unclear.

Objective To explore the role and potential regulatory mechanism of gastric cancer-associated lncRNA LINC02859 in MNNG-induced malignant transformation of human normal gastric mucosal cells (GES-1).

Methods A total of 110 gastric cancer patients from a high incidence area of gastric cancer in Gansu Province were selected, and their cancer tissues and normal gastric mucosa tissues adjacent to the cancer were collected to detect the expression level of LINC02859 by real-time quantitative PCR (RT-qPCR). High-throughput sequencing and bioinformatics analysis of the tissues were used to identify the potential signaling pathways regulated by the genes co-expressed with LINC02859. GES-1 cells at 70%-80% cell fusion with low cell passage number and normal morphology were incubated with 0, 0.25 and 0.5 μmol·L⁻¹ MNNG solution for 48 h and the LINC02859 expression level was detected. Cell proliferation activity was detected by Cell Counting Kit-8 (CCK-8), clone formation was detected by plate clone formation assay, and cell migration ability was detected by scratch assay to evaluate the effects of MNNG on cell morphology and function. The expression levels of key proteins of Wnt signaling pathway were detected by RT-qPCR and Western blotting.

Results  The RT-qPCR results showed that LINC02859 was lowly expressed in the gastric cancer tissues compared with the paracancerous tissues, and the difference was statistically significant (P < 0.05). The pathway enrichment analysis showed that LINC02859 potentially regulated the Wnt pathway. The in vitro malignant transformation assay suggested that after the MNNG exposure, the malignant cells of passage 5 (MC-5) had altered morphology, increased number of colony formation, and higher proliferation and migration ability than the control cells; compared with the normal GES-1 cells, LINC02859 gene expression levels were reduced in the 0.25 μmol·L⁻¹ and the 0.5 μmol·L⁻¹ MNNG-exposed GES-1 cells; the expression levels of key proteins of the Wnt pathway, transcription factor 7 (TCF7), Axis inhibitor (Axin1), phosphorylation of glycogen synthase kinase-3 beta (p-GSK-3β), casein kinase 1 (CK1), and β-catenin, were elevated in the cells after 0.5 μmol·L⁻¹ MNNG exposure (P < 0.05); whereas, overexpression of LINC02859 suppressed the activating effect of MNNG on the Wnt pathway.

Conclusion LINC02859 is lowly expressed in the cancer tissues of gastric cancer patients. MNNG exposure induces morphological and functional changes in GES-1 cells, down-regulated expression of LINC02859, and activation of the Wnt signaling pathway; overexpression of LINC02859 inhibits the activation of the Wnt signaling pathway in the gastric carcinogenesis induced by MNNG exposure.