Tristetraprolin inhibits the growth of human glioma cells through downregulation of urokinase plasminogen activator/urokinase plasminogen activator receptor mRNAs

SUZ12 inhibition attenuates cell proliferation of glioblastoma via post-translational regulation of CDKN1B

BACKGROUND

Human gliomas are aggressive brain tumors characterized by uncontrolled cell proliferation. Differential expression of Polycomb repressive complex 2 (PRC2) has been reported in various subtypes of glioma. However, the role of PRC2 in uncontrolled growth in glioma and its underlying molecular mechanisms remain to be elucidated.

OBJECTIVE

We aimed to investigate the functional role of PRC2 in human glioblastoma cell growth by silencing SUZ12, the non-catalytic core component of PRC2.

METHODS

Knockdown of SUZ12 was achieved by infecting T98G cells with lentivirus carrying sequences specifically targeting SUZ12 (shSUZ12). Gene expression was examined by quantitative PCR and western analysis. The impact of shSUZ12 on cell growth was assessed using a cell proliferation assay. Cell cycle distribution was analyzed by flow cytometry, and protein stability was evaluated in cycloheximide-treated cells. Subcellular localization was examined through immunofluorescence staining and biochemical cytoplasmic-nuclear fractionation. Gene expression analysis was also performed on human specimens from normal brain and glioblastoma patients.

RESULTS

SUZ12 knockdown (SUZ12 KD) led to widespread decrease in the PRC2-specific histone mark, accompanied by a slowdown of cell proliferation through G1 arrest. In SUZ12 KD cells, the degradation of CDKN1B protein was reduced, resulting from alterations in the MYC-SKP2-CDKN1B axis. Furthermore, nuclear localization of CDKN1B was enhanced in SUZ12 KD cells. Analysis of human glioblastoma samples yielded increased expression of EZH2 and MYC along with reduced CDKN1B compared to normal human brain tissue.

CONCLUSION

Our findings suggest a novel role for SUZ12 in cell proliferation through post-translational regulation of CDKN1B in glioblastoma.

Effectiveness of Combined Thrombolysis and Mild Hypothermia Therapy in Acute Cerebral Infarction: A Meta-Analysis

Objective

To evaluate the effectiveness and safety of thrombolytic therapy combined with mild hypothermia in patients with acute cerebral infarction (ACI), based on a meta-analysis of randomized controlled trials (RCTs).

Methods

PubMed, EMBASE, Cochrane Library, and Chinese National Knowledge Infrastructure Database of Controlled Trials were systematically screened for randomized controlled trials (RCTs) of thrombolytic therapy combined with mild hypothermia in treating ACI from inception to January 2021. Participation and outcomes among intervention enrollees are as follows: P, participants (patients in ACI); I, interventions (thrombolysis in combination with mild hypothermia therapy); C, controls (thrombolysis merely); O, outcomes (main outcomes are the change of NIHSS, glutathione peroxidase, superoxide dismutase, malondialdehyde, inflammatory factor interleukin-1β, tumor necrosis factor-α, and adverse reaction). Following data extraction and quality assessment, a meta-analysis was performed using RevMan 5.3 software.

Results

A total of 26 RCTs involving 2071 patients were included. Compared to thrombolysis alone, thrombolytic therapy combined with mild hypothermia leads to better therapeutic efficacy [RR = 1.23, 95% CI (1.16, 1.31)], NIHSS [MD = -2.02, 95% CI (-2.55, -1.49)], glutathione peroxidase [MD = 8.71, 95% CI (5.55, 11.87)], superoxide dismutase [MD = 16.52, 95% CI (12.31, 19.74)], malondialdehyde [MD = -1.86, 95% CI (-1.98, -1.75)], interleukin-1β [MD = -3.48, 95% CI (-4.88, -2.08)], tumor necrosis factor-α [MD = -0.46, 95% CI (-3.39, 2.48)], and adverse reaction [RR = 0.87, 95% CI (0.63, 1.20)].

Conclusions

Thrombolytic therapy combined with mild hypothermia demonstrates a beneficial role in reducing brain nerve function impairment and inflammatory reactions in ACI subjects analysed in this meta-analysis.

Tristetraprolin, a Potential Safeguard Against Carcinoma: Role in the Tumor Microenvironment

Tristetraprolin (TTP), a well-known RNA-binding protein, primarily affects the expression of inflammation-related proteins by binding to the targeted AU-rich element in the 3' untranslated region after transcription and subsequently mediates messenger RNA decay. Recent studies have focused on the role of TTP in tumors and their related microenvironments, most of which have referred to TTP as a potential tumor suppressor involved in regulating cell proliferation, apoptosis, and metastasis of various cancers, as well as tumor immunity, inflammation, and metabolism of the microenvironment. Elevated TTP expression levels could aid the diagnosis and treatment of different cancers, improving the prognosis of patients. The aim of this review is to describe the role of TTP as a potential safeguard against carcinoma.

Roles of Tristetraprolin in Tumorigenesis

Genetic loss or mutations in tumor suppressor genes promote tumorigenesis. The prospective tumor suppressor tristetraprolin (TTP) has been shown to negatively regulate tumorigenesis through destabilizing the messenger RNAs of critical genes implicated in both tumor onset and tumor progression. Regulation of TTP has therefore emerged as an important issue in tumorigenesis. Similar to other tumor suppressors, TTP expression is frequently downregualted in various human cancers, and its low expression is correlated with poor prognosis. Additionally, disruption in the regulation of TTP by various mechanisms results in the inactivation of TTP protein or altered TTP expression. A recent study showing alleviation of Myc-driven lymphomagenesis by the forced expression of TTP has shed light on new therapeutic avenues for cancer prevention and treatment through the restoration of TTP expression. In this review, we summarize key oncogenes subjected to the TTP-mediated mRNA degradation, and discuss how dysregulation of TTP can contribute to tumorigenesis. In addition, the control mechanism underlying TTP expression at the posttranscriptional and posttranslational levels will be discussed.

Tristetraprolin: A novel target of diallyl disulfide that inhibits the progression of breast cancer

Diallyl disulfide (DADS), a volatile component of garlic oil, has various biological properties, including antioxidant, antiangiogenic and anticancer effects. The present study aimed to explore novel targets of DADS that may slow or stop the progression of breast cancer. First, xenograft tumor models were created by subcutaneously injecting MCF-7 and MDA-MB-231 breast cancer cells into nude mice. Subsequently, western blot analysis was performed to investigate the expression of tristetraprolin (TTP), urokinase-type plasminogen activator (uPA) and matrix metalloproteinase-9 (MMP-9) in the xenograft tumors, and cell cultures. Tablet cloning, Transwell and wound healing assays revealed that DADS treatment significantly inhibited the proliferation, invasion and migration of breast cancer cells. In addition, DADS treatment led to significant downregulation of uPA and MMP-9 protein expression, but significantly upregulated TTP expression in vivo and in vitro. Knocking down TTP expression using small interfering RNA reversed the aforementioned effects of DADS, which suggests TTP is a key target of DADS in inhibiting the progression of breast cancer.

Low tristetraprolin expression promotes cell proliferation and predicts poor patients outcome in pancreatic cancer

Tristetraprolin (also known as TTP, TIS11, ZFP36, and Nup475) is a well-characterized tumor suppressor that is down-regulated in several tumor types. In the current study, we found that TTP expression was markedly reduced in pancreatic cancer samples as compared to matched normal tissues. Low TTP level was associated with age (P=0.037), tumor size (P=0.008), tumor differentiation (P=0.004), postoperative T stage (pT stage, P<0.001), postoperative N stage (pN stage, P=0.008) and TNM stage (P<0.001). Moreover, low TTP expression predicted reduced survival rates and poor patient outcome. We also found that TTP impairs pancreatic cancer cell proliferation both in vivo and in vitro. Fluorescence Activated Cell Sorting (FACS) assay showed that TTP over-expression both increases apoptosis and decreases proliferation in pancreatic cancer cells. RNA-sequencing analysis showed that TTP over-expression downregulates several tumor-related factors, including Pim-1 and IL-6. Our findings indicate that TTP could serve as a potential prognostic indicator in pancreatic cancer.

Resveratrol Induces Glioma Cell Apoptosis through Activation of Tristetraprolin

Tristetraprolin (TTP) is an AU-rich elements (AREs)-binding protein, which regulates the decay of AREs-containing mRNAs such as proto-oncogenes, anti-apoptotic genes and immune regulatory genes. Despite the low expression of TTP in various human cancers, the mechanism involving suppressed expression of TTP is not fully understood. Here, we demonstrate that Resveratrol (3,5,4'-trihydroxystilbene, Res), a naturally occurring compound, induces glioma cell apoptosis through activation of tristetraprolin (TTP). Res increased TTP expression in U87MG human glioma cells. Res-induced TTP destabilized the urokinase plasminogen activator and urokinase plasminogen activator receptor mRNAs by binding to the ARE regions containing the 3' untranslated regions of their mRNAs. Furthermore, TTP induced by Res suppressed cell growth and induced apoptosis in the human glioma cells. Because of its regulation of TTP expression, these findings suggest that the bioactive dietary compound Res can be used as a novel anti-cancer agent for the treatment of human malignant gliomas.