ABSTRACT
PIN1 is the only known enzyme capable of recognizing and isomerizing the phosphorylated Serine/ThreonineProline motif. Through this mechanism, PIN1 controls diverse cellular functions, including telomere maintenance. Both PIN1 overexpression and its involvement in oncogenic pathways are involved in several cancer types, including glioblastoma (GBM), a lethal disease with poor therapeutic resources. However, knowledge of the role of PIN1 in GBM is limited. Thus, the present work aimed to study the role of PIN1 as a telomere/telomerase regulator and its contribution to tumor biology. PIN1 knockout (KO) LN229 cell variant using CRISPR/Cas9 was developed and compared with PIN1 LN229 expressing cells. To study the effect of PIN1 absence, status of NFκB pathway was evaluated by luciferase reporter gene assay and quantitative PCR. Results revealed that PIN1 deletion in GBM cells diminished the active levels of NFκB and decrease the transcription of il8 and htert genes. Then, telomere/telomerase related processes were studied by RQTRAP assay and telomere length determination by qPCR, obtaining a reduction both in telomerase activity as in telomere length in PIN1 KO cells. In addition, measurement of SA ßgalactosidase and caspase3 activities revealed that loss of PIN1 triggers senescence and apoptosis. Finally, migration, cell cycle progression and tumorigenicity were studied by flow cytometry/western blot, Transwell assay and in vivo experiments, respectively. PIN1 deletion decreased migration as well as cell cycle progression by increasing doubling time and also resulted in the loss of LN229 cell ability to form tumors in mice. These results highlight the role of PIN1 in telomere homeostasis and GBM progression, which supports PIN1 as a potential molecular target for the development of novel therapeutic agents for GBM treatment.