The Pinx1 Gene Downregulates Telomerase and Inhibits Proliferation of CD133+ Cancer Stem Cells Isolated from a Nasopharyngeal Carcinoma Cell Line by Regulating Trfs and Mad1/C-Myc/p53 Pathways

Background/Aims: Cancer stem cells (CSCs) are important factors for the continuous growth, recurrence, and metastasis of malignant tumors. They are responsible for the ineffectiveness of traditional radiotherapy and chemotherapy toward malignant tumors. Currently, stem cells or side-population cells have been isolated from many cancer cell lines and malignant tumor tissues, including nasopharyngeal carcinoma. Exploring the biological characteristics of CSCs for CSC-targeted therapy has gained importance. CSCs possess higher telomerase activity; thus, the use of the gene encoding telomerase inhibitor PinX1 gene to target telomerase in CSCs and inhibit proliferation, invasion, and metastasis of CSCs has become an important means for the treatment of malignant tumors. PinX1 may regulate complex pathways, including TRF1, Mad1/c-Myc, and p53. Methods: In this study, nasopharyngeal CD133+ CSCs were sorted using CD133 immunomagnetic beads by flow cytometry The successful isolation of CD133+ CSCs was confirmed by examining their surface markers, namely CD44, NaNOG, and SOX2 as well as their ability to undergo in vivo tumorigenesis and in vitro sphere formation, proliferation, migration, and invasion. In addition, CD133+ CSCs were transfected with the constructed PinX1 overexpression plasmid or siRNA and the resulting effects on their proliferation, migration, invasion, and apoptosis were detected using cell counting kit-8 (CCK-8), transwell assay, and scratch test, respectively. Furthermore, their effects on mRNA and protein levels of TRF1, TRF2, Mad1, c-Myc, and p53 were examined using quantitative real-time PCR and western blot, respectively. Results: The overexpression of PinX1 in CD133+ CSCs significantly decreased hTERT (P < 0.001), inhibited proliferation, migration, and invasion, induced apoptosis, and significantly decreased c-Myc mRNA levels (P < 0.001), while it increased TRF1, Mad1, and p53 mRNA levels (all P < 0.001). On the other hand, PinX1 silencing in CD133+ CSCs significantly decreased TRF1, Mad1, and p53 mRNA levels (all P < 0.01), while it increased hTERT and c-Myc mRNA levels (all P < 0.05). Conclusion: These results indicate that PinX1 downregulates telomerase activity in CD133+ CSCs, inhibits its proliferation, migration, and invasion, and induces apoptosis possibly through TRF1, Mad1/c-Myc, and p53–mediated pathways

Joint quantitative measurement of hTERT mRNA in both peripheral blood and circulating tumor cells of patients with nasopharyngeal carcinoma and its clinical significance

Abstract Background The study was aimed to quantitatively detect mRNA levels of the catalytic subunit of telomerase (hTERT) in both peripheral blood and circulating tumor cells (CTCs) of patients with nasopharyngeal carcinoma (NPC) and explore its significance in early diagnosis and treatment of NPC. Methods hTERT mRNA levels in peripheral blood and CTCs of 33 NPC patients before and after treatment with intensity-modulated radiation therapy (IMRT) or/and chemotherapy and 24 healthy controls were measured using real-time quantitative PCR (qPCR) and their correlations to clinic pathological factors of NPC were analyzed. Results Peripheral hTERT mRNA content was 10.75 ± 4.29 in NPC patients and 0.95 ± 0.37 in control subjects (P < 0.05), and had a significant correlation with patients’ clinical stage, T stage, and N stage (P < 0.05). Treatment of NPC patients at stages I and II with simple IMRT significantly reduced hTERT mRNA level from 5.60 ± 2.33 to 3.43 ± 1.42 (P < 0.05) and treatment of patients at advanced stage (III and IV) with induction chemotherapy followed by IMRT significantly reduced hTERT mRNA levels from 12.68 ± 3.08 to 10.68 ± 2.48 to 3.13 ± 1.69 (P < 0.05), respectively. In addition, the study also showed that hTERT mRNA content in CTCs of NPC patients was 10.65 ± 4.28, evidently higher than that of 1.09 ± 0.40 in control subjects (P < 0.05) and hTERT mRNA level in CTCs of NPC patients was obviously correlated to patients’ clinical stage, T stage and N stage (P < 0.05). After treatment, hTERT mRNA level in CTCs of NPC patients lowered from 10.65 ± 4.28 to 5.59 ± 2.32 (P < 0.05). The correlation analysis found that hTERT mRNA level in peripheral blood and CTCs of NPC patients were highly correlated with a correlation coefficient of 0.981. Conclusions hTERT mRNA levels in peripheral blood and CTCs of NPC patients were significantly enhanced compared to that in healthy controls and highly correlated. Changes in hTERT mRNA level was closely correlated to patients’ clinical stage and T stage. Radiochemotherapy could effectively reduce hTERT mRNA level in peripheral blood and CTCs. Thus, it is possible using the joint detection of hTERT mRNA level in peripheral blood and CTCs as a new biomarker for early diagnosis, treatment efficacy and prognosis of NPC

PinX1-Promoted Autophagy Inhibits Cell Proliferation and Induces Cell Apoptosis by Inhibiting the NF-κB/p65 Signaling Pathway in Nasopharyngeal Carcinoma

Background: The role of Pin2 telomeric repeat factor 1-interacting telomerase inhibitor 1 (PinX1) in tumorigenesis and development has been extensively studied. As we previously demonstrated, PinX1 plays an important role in modulating epithelial-mesenchymal transition (EMT), stemness, cell proliferation, and apoptosis in nasopharyngeal carcinoma (NPC). However, the relationship between PinX1, autophagy, and cell function in NPC remains unclear. This study aimed to investigate the mechanisms by which PinX1 regulates autophagy in NPC, and to explore its biological role and clinical significance in disease progression. Methods: The proliferative capacity of NPC cells was assessed by MTT and xenograft tumorigenicity assays. Autophagic flux was monitored using a tandem monomeric DAPI–FITC–LC3 reporter assay. The rates of apoptosis and the cell cycle in NPC cells were analyzed using flow cytometry. The activation of autophagy and the signaling status of the AKT/mTOR and NF-κB/p65 pathways were evaluated by Western blot analysis. Results: In addition to promoting autophagy and apoptosis, PinX1 overexpression suppressed proliferation, migration, invasion, and decelerated cell-cycle progression in NPC cells. These effects were reversed by inhibiting autophagy with 3-methyladenine. Mechanistic investigations clarified that PinX1 overexpression significantly reduced the expression of p-AKT, p-mTOR, p65, and p-p65. Chloroquine treatment in PinX1-overexpressing cells did not significantly alter p-AKT and p-mTOR levels, whereas 3-MA treatment in PinX1-overexpressing cells resulted in increased p65 and p-p65 expression, relative to untreated PinX1-overexpressing cells. Conclusions: It appears that PinX1 promotes autophagy by inhibiting the AKT/mTOR signaling pathway, which then inhibits NF-κB/p65 pathways, and consequently inhibiting cell proliferation and causing cell apoptosis in NPC cells