Abstract: BACKGROUND: Long non coding RNA (lncRNA) and microRNA (miRNA) are two types of small non-coding RNA that are involved in regulating cell proliferation, apoptosis and migration and other life activities, and lncRNA can also be used as a competitive endogenous RNA and miRNA target binding to regulate the expression of miRNA target genes and play an important role in the occurrence and development of tumors. LINC02532 is an lncRNA that can target miR-129-5p and miR-490-5p to promote the proliferation, migration and invasion of gastric cancer cells, but its effect on the biological behavior of pancreatic cancer stem cells and the action mechanism are still unknown. 
OBJECTIVE: To investigate the effect and action mechanism of LINC02532 on the proliferation, migration, invasion and apoptosis of pancreatic cancer stem cells. 
METHODS:  (1) Fifty-six patients with pancreatic cancer confirmed by pathological examination in North China University of Science and Technology Affiliated Hospital from January 2017 to June 2018 were selected as the research subjects. Real time fluorescent quantitative PCR was used to detect the expression levels of LINC02532 and miR-145 in pancreatic cancer tissues and adjacent tissues. (2) Using CD24+CD44+ESA+ as surface markers, pancreatic cancer stem cells were sorted from human pancreatic cancer cells PANC-1 by flow cytometry. Pancreatic cancer stem cells were divided into normal group, si-LINC02532 group (transfected with LINC02532 small interfering RNA), si-NC group (transfected with disorderly negative sequence), si-LINC02532+anti-miR-145 group (co-transfected with LINC02532 small interfering RNA and miR-145 inhibitor) and si-LINC02532+anti-miR-NC group (co-transfected with LINC02532 small interfering RNA and miR-145 inhibitor negative control sequence). At 12 hours after transfection, real time fluorescent quantitative PCR was used to detect the expression levels of LINC02532 and miR-145 in each group of cells. Cell counting kit-8 (CCK-8) assay was utilized to detect the cell survival rate. The colony formation test was applied to detect the number of cell clones formed. Transwell chamber was used to detect cell migration and invasion. Flow cytometry was utilized to detect cell apoptosis rate. Western blot assay was used to detect the expression levels of P21, Bax, Caspase-3, E-cadherin and MMP-2 protein. The double luciferase reporter gene experiment was utilized to verify the regulatory relationship between miR-145 and LINC02532.   
RESULTS AND CONCLUSION: (1) Compared with adjacent tissues, the expression level of LINC02532 increased in pancreatic cancer tissues (P < 0.05), while the expression level of miR-145 decreased (P < 0.05). (2) Compared with the si-NC group, the survival rate, colony formation, cell migration and invasion number, and MMP-2 protein expression level of pancreatic cancer stem cells reduced in the si-LINC02532 group (P < 0.05), while the apoptotic rate and the expression levels of P21 and Bax, Caspase-3 and E-cadherin protein increased (P < 0.05), but there was no significant difference between the si-NC group and the normal group (P > 0.05). (3) LINC02532 targeted negatively regulated miR-145 expression in pancreatic cancer stem cells. Compared with the si-LINC02532+anti-miR-NC group, the survival rate, colony formation, cell migration and invasion number, and MMP-2 protein expression level of pancreatic cancer stem cells increased in the si-LINC02532+anti-miR-145 group (P < 0.05), while the apoptotic rate and the expression levels of P21 and Bax, Caspase-3 and E-cadherin protein reduced (P < 0.05). (4) The results show that LINC02532 was up-regulated in pancreatic cancer tissues, and down-regulating its expression may inhibit the proliferation, migration and invasion of pancreatic cancer stem cells by targeting up-regulation of miR-145 expression, and induce apoptosis.

Key words: LINC02532, miR-145, pancreatic cancer stem cells, biological behavior, factor, protein, pathway, targeting, apoptosis