Key role of PIN1 in telomere maintenance and oncogenic behavior in a human glioblastoma model

PIN1 is the only known enzyme capable of recognizing and isomerizing the phosphorylated Serine/Threonine‑Proline 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) LN‑229 cell variant using CRISPR/Cas9 was developed and compared with PIN1 LN‑229 expressing cells. To study the effect of PIN1 absence, status of NF‑κB pathway was evaluated by luciferase reporter gene assay and quantitative PCR. Results revealed that PIN1 deletion in GBM cells diminished the active levels of NF‑κB and decrease the transcription of il‑8 and htert genes. Then, telomere/telomerase related processes were studied by RQ‑TRAP 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 β‑galactosidase and caspase‑3 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 LN‑229 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.

Rational design of PIN1 inhibitors for cancer treatment based on conformational diversity analysis and docking based virtual screening

The parvulin PIN1 (peptidyl-prolyl cis-trans isomerase NIMA-interacting 1), is the only enzyme capable of isomerizing prolines of phospho-Serine/Threonine-Proline motifs. PIN1 binds to a subset of proteins and plays an essential role in regulating protein function post-phosphorylation control. Furthermore, the activity of PIN1 regulates the outcome of the signalling of proline-directed kinases (e.g. MAPK, CDK, or GSK3) and thus regulates cell proliferation and cell survival. For these reasons, PIN1 inhibitors are interesting since they may have therapeutic implications for cancer. Several authors have already reported that the non-structural point mutation Trp34Ala prevents PIN1 from interacting with its downstream effector proteins. In this work, we characterized PIN1 structurally, intending to explore new inhibition targets for the rational design of pharmacological activity compounds. Through a conformational diversity analysis of PIN1, we identified and characterized a highly specific druggable pocket around the residue Trp34. This pocket was used in a high-throughput docking screening of 450,000 drug-like compounds, and the top 10 were selected for re-docking studies on the previously used conformers. Finally, we evaluated the binding of each compound by thermal shift assay and found four molecules with a high affinity for PIN1 and potential inhibitory activity. Through this strategy, we achieved novel drug candidates with the ability to interfere with the phosphorylation-dependent actions of PIN1 and with potential applications in the treatment of cancer.Communicated by Ramaswamy H. Sarma.

Telomeropathies: Etiology, diagnosis, treatment and follow-up. Ethical and legal considerations

Telomeropathies involve a wide variety of infrequent genetic diseases caused by mutations in the telomerase maintenance mechanism or the DNA damage response (DDR) system. They are considered a family of rare diseases that often share causes, molecular mechanisms and symptoms. Generally, these diseases are not diagnosed until the symptoms are advanced, diminishing the survival time of patients. Although several related syndromes may still be unrecognized this work describes those that are known, highlighting that because they are rare diseases, physicians should be trained in their early diagnosis. The etiology and diagnosis are discussed for each telomeropathy and the treatments when available, along with a new classification of this group of diseases. Ethical and legal issues related to this group of diseases are also considered.

Relevance of small GTPase Rac1 pathway in drug and radio-resistance mechanisms: Opportunities in cancer therapeutics

Rac1 GTPase signaling pathway has a critical role in the regulation of a plethora of cellular functions governing cancer cell behavior. Recently, it has been shown a critical role of Rac1 in the emergence of resistance mechanisms to cancer therapy. This review describes the current knowledge regarding Rac1 pathway deregulation and its association with chemoresistance, radioresistance, resistance to targeted therapies and immune evasion. This supports the idea that interfering Rac1 signaling pathway could be an interesting approach to tackle cancer resistance.

Rho GTPases as therapeutic targets in cancer (Review)

Rho GTPases are key molecular switches controlling the transduction of external signals to cytoplasmic and nuclear effectors. In the last few years, the development of genetic and pharmacological tools has allowed a more precise definition of the specific roles of Rho GTPases in cancer. The aim of the present review is to describe the cellular functions regulated by these proteins with focus in deregulated signals present in malignant tumors. Finally, we describe the state of the art in search of different experimental therapeutic strategies with Rho GTPases as molecular targets.

[Rho GTPases as molecular targets in cancer. Strategies and therapeutic opportunities]

Rho GTPases are molecular switches that control the different cellular processes. Deregulation of these proteins is associated to transformation and malignant progression in several cancer types. Given the evidence available of the role of Rho GTPases in cancer it is suggested that these proteins can serve as potential therapeutic targets. This review focuses on the strategies used to develop Rho GTPases modulators and their potential use in therapeutic settings.

Lack of beta-amyloidosis in transgenic mice expressing low levels of familial Alzheimer's disease missense mutations

Point mutations within the beta-amyloid precusor protein (beta-APP) gene known to segregate with Alzheimer's disease in certain families were introduced into human beta-APP cDNAs and expressed under the control of a neuron-specific enolase (NSE) promoter in mice. The transgenic animals exhibited transgene expression predominantly in neocortex and hippocampus where the levels were maximally 1.3-fold of those of wild-type mouse beta-APP. Quantitative immunoblot analysis in homozygous mice carrying different missense mutations showed slightly increased alpha-secretory processing. In V7171 mice compared to nontransgenic mice there was more alpha-secretory beta-APP (beta-APPsec) in cortex/hippocampus, less in cerebellum, and no difference in midbrain/brain stem. In none of the transgenic animals tested was a 4 kDa amyloid fragment detected by Western blotting of brain extracts, immunohistochemistry, or by 125I-A beta-binding onto brain sections. No glial reaction was observed. Behavioral analysis of mice carrying the V7171 mutation showed no appreciable deficit in comparison to wild-type mice. Together, these data suggest that low levels of expression of mutated beta-APP in 10-12-month-old transgenic mouse brains result in slightly more beta-APPsec, and are insufficient to induce amyloidogenic processing and AD-like pathology.