Long noncoding RNA GAPLINC promotes invasion in colorectal cancer

This study aimed to investigate the role of long noncoding RNAs (lncRNAs) in the metastasis of colorectal cancer (CRC). Metastasis is an important prognostic factor of CRC, and lncRNAs have been implicated in tumor proliferation and metastasis.

Genome-wide lncRNA expression patterns in metastatic lymph nodes compared with paired normal lymph nodes of CRC were assessed by microarray analysis. Gastric adenocarcinoma predictive long intergenic noncoding (GAPLINC) RNA was detected via functional prediction. The increased expression of GAPLINC was found to be positively correlated with larger tumor size, advanced tumor stage (T stage), advanced node stage (N stage), increased death, and shorter survival of patients with CRC by in situ hybridization analysis. Besides, the decreased expression of GAPLINC could significantly repress CRC cell invasion in vitro and also inhibit proliferation in vitro and in vivo. RNA pull-down with mass spectrum experiments revealed that PTB-associated splicing factor (PSF) and non-POU-domain-containing octamer-binding (NONO) protein bound to GAPLINC and reversed the effect of GAPLINC on cell invasion. Gene array and bioinformatics analyses identified that snail family zinc finger 2 (SNAI2) was involved in the biological processes of GAPLINC/PSF/NONO.

GAPLINC accelerated the growth of CRC cells in vivo

A, B. Photographs of the xenograft-transplanted nude mouse tumor models and the harvested tumors were captured 4 weeks after the injection of GAPLINC-shRNA or empty vector of HCT116 cells (n = 5). C. Tumor volume was calculated as the length × width² × 0.5 every week after injection. D. Weights of xenografts were measured when the mice were sacrificed. E. qPCR analysis of GAPLINC expression in xenograft tumor tissues. F. Hematoxylin and eosin and immunohistochemical (IHC) staining of the xenograft tumors. IHC staining showed that Ki67 expression was weakened in the GAPLINC-shRNA group compared with the empty vector group.

This study indicated the importance of GAPLINC in promoting CRC invasion via binding to PSF/NONO and partly by stimulating the expression of SNAI2. Hence, GAPLINC may serve as a promising target for CRC diagnosis and therapy. The findings may help in developing a novel therapeutic strategy for patients with CRC.