br MKI proliferation marker protein
MKI67, proliferation marker protein Ki-67, is a nuclear protein ex-pressed in all proliferation vertebrate cells, and it is a widely biomarker to estimate the proportion of dividing cells to grade tumors [28,29]. Ki-67 expression is a late marker of U73122 entry and also is a central player with many associated genes in CRC . Therefore, down-regulation of MKI67 will restrain the cell proliferation in CRCs. Ac-cording to our study, it is speculated that SNRPA1 knocking down to inhibit the expression of MKI67 seems to be the upstream event in the pathway.
CDK1(cyclin-dependent kinase 1) is a critical regulator of G2-M checkpoint and it is considered a possible target for cancer treatment. Biomedicine & Pharmacotherapy 117 (2019) 109076
One study found that CDk1 interacts with iASPP to aﬀect CRC cell proliferation and apoptosis through the p53 apoptosis pathway . CDK1 has also been reported upregulated in CRC circulating tumor cells . In addition, a high ratio of CDK1 expression in nuclear/cytoplasm was a poor prognosis in CRC patients . Similar to MKI67, we found that knocking down of SNRPA1 can also inhibit the expression of CDK1, which contributed to the dampened cell proliferation in RKO or HCT116 cells.
NRP1(neuropilin 1) and VEGFR2 were thought to play a regulatory role in development angiogenesis as well as in tumor angiogenesis . They might also play a role in colon carcinogenesis and development of metastases. A earlier study reported that in ex vivo transfer experiments animals with tumor from SiRNA-NRP1 transferred cells showed no significant inhibition of tumor growth compared to siRNA control . Another study suggested that the preserved expression of NRP1 in-dicated a better prognosis in colon cancer . Our results indicated that NRP1 is upregulated after knocking down of SNRPA1. Upregula-tion of NRP1 upregulation along the changes of other genes contributed to the inhibition of cell proliferation, apoptosis in vitro and ex vivo tumor development. There is another study that reported that over-expression of NRP1 has been shown to promote tumor progression in certain cancers, glioma, prostate cancer, and colon cancer . Con-sidering the current research on NRP1, additional studies are required before the exact role of NRP1 in CRC could be delineated.
PIK3R1 (phosphoinositide-3-kinase, regulatory subunit 1), is a component of PI3K signaling which is one the most frequently down-regulated pathways in several human cancers, including CRC. Somatic mutation of PIK3R1 was found to promote gliomagenesis . The importance of PI3K signaling in various cancers has made it an at-tractive therapeutic target . In this study, we found that PIK3R1 was upregulated after SNRPA1 knocking down, this upregulation of PIK3R1 contributed to the inhibition of RKO or HCT 116 cell pro-liferation in vitro and ex vivo, which is also reminiscent of previous reports in regard to its role in CRC.
In summary, the present study suggested that SNRPA1 is an im-portant player in the development or progression of CRCs. The in vitro experiments demonstrated that Knocking down of SNRPA1 by shRNA lentivirus inhibited the cell proliferation, colony formation and pro-moted cell apoptosis in two representative CRC cell line, RKO and HCT116. The ex vivo tumor implantation from shSNRP1 lentivirus transduced RKO cells in nude mice further corroborated these findings. Further microarray gene profiling and the western blotting analysis identified a few important oncogenic or tumor suppressor genes regu-lated by SNRPA1 in CRCs. All together, these results showed that SNRPA1 plays an important role in the CRCs by upregulation of NRP1, PIK3R1 and downregulation of E2FZ, VEGFC, MKI67, CDK1 and etc. Our findings identified novel roles of SNRPA1 in CRCs, except its in-volvement in the RNA processing. Those new findings will shed light on future development of new therapeutic targets in the treatment of CRCs.
This study was funded by Shougang Science and Technology Innovation Fund.
Conflict of interest
All authors declare that there is no conflict of interest existing re-garding the research, authorship and publication of this manuscript.
All applicable international, national, and/or institutional guide-lines for the care and use of animals were followed. This article does not contain any studies with human participants performed by any of the authors.
We thank all the colleagues who participated in this project, Q.M. Zeng, F.M. Lei, Y.G. Chang, Z.C. Gao, Y.Z. Wang, Q.K. Gao, and P.F. Niu all performed in the involved research and helped with manuscript preparation, Q. Li supervised the whole experiment and wrote the final manuscript with approval of all authors.