p21WAF1/CIP1 promotes p53 protein degradation by facilitating p53-Wip1 and p53-Mdm2 interaction

The role of the PPM1D gene in tumor pathogenesis

The PPM1D gene and its protein product (serine-threonine protein phosphatase, PPM1D or Wip1) are involved in regulation of cell's DNA damage response, cell cycle control, and repair. Amplification, overexpression, or mutations of the PPM1D gene have a significant impact on cell responses to stress factors and genetic instability as well as impairments of processes of double-strand break repair, nucleotide excision repair, base excision repair, cell cycle, and apoptosis. PPM1D dephosphorylates and thus inactivates p53, proteins that respond to DNA strand integrity damage, cell cycle checkpoint proteins, and apoptotic proteins. This contributes to tumor development, growth, and maintenance of the tumor phenotype. In this review we consider data on the role of the PPM1D gene in the formation and maintenance of various oncological processes, including tumors of the mammary glands, ovaries, prostate gland, esophagus, stomach, intestines, liver and pancreas, hemoblastoses, and others.

TP53 mutations and MDM2 polymorphisms in breast and ovarian cancers: amelioration by drugs and natural compounds

Globally, breast and ovarian cancers are major health concerns in women and account for significantly high cancer-related mortality rates. Dysregulations and mutations in genes like TP53, BRCA1/2, KRAS and PTEN increase susceptibility towards cancer. Here, we discuss the impact of mutations in the key regulatory gene, TP53 and polymorphisms in its negative regulator MDM2 which are reported to accelerate cancer progression. Missense mutations, null mutations, transversions, transitions, and point mutations occurring in the TP53 gene can cause an increase in metastatic activity. This review discusses mutations occurring in exon regions of TP53, polymorphisms in MDM2 and their interaction with large ribosomal subunit protein (RPL) leading to cancer development. We also highlight the potential of small molecules e.g. p53 activators like XI-011, Tenovin-1, and Nutlin-3a for the treatment of breast and ovarian cancers. The therapeutic efficacy of natural compounds in amelioration of these two types of cancers is also discussed.

RNF144B-mediated p21 degradation regulated by HDAC3 contribute to enhancing ovarian cancer growth and metastasis

We have shown before that HDAC3 was involved in the pathogenesis of ovarian cancer; however, the specific mechanism of HDAC3 on the pathogenesis of ovarian cancer has not been thoroughly studied. To explore the related proteins in the mechanism of HDAC3 on ovarian cancer. The transcriptome profiles were identified in ovarian carcinoma cells with HDAC3 knockdown or overexpression. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blot analysis were used to verify transfection efficiency. Immunofluorescence staining were performed to detect the expression levels of HDAC3 and RNF144B in tissues. Cell proliferation, apoptosis, migration and invasion were confirmed by cell counting Kit-8 (CCK-8), terminal deoxynucleotidyl transferase (TUNEL) and transwell assay, respectively. The protein expression of p53, p21, Bax and Bcl-2 was confirmed by western blot, and CoIP assay was used to validate RNF144B/P21/P53 interaction. Meanwhile, the protein synthesis inhibitor cycloheximide (CHX) was performed to treat cells to probe p21 stability. Finally, we established an in vivo tumor model to explore the effects of HDAC3 and RNF144B on tumor growth. Microarray results showed that among the overlapping genes in the two profiles (HDAC3 knockdown and overexpression), RNF144B was decreased or increased in ovarian carcinoma cells with HDAC3 knockdown or overexpression, HDAC3 overexpression promoted RNF144B expression, and HDAC3 knockdown hindered RNF144B levels. The levels of HDAC3 and RNF144B in malignant ovarian cancer were significantly higher than those in normal ovarian tissue and benign ovarian cancer tissue. RNF144B promoted cell proliferation, migration and invasion, and inhibited cell apoptosis. In addition, overexpression of HDAC3 or RNF144B inhibited p53/p21/Bax expression and promoted Bcl-2 expression. Knockout of HDAC3 or RNF144B has the opposite effect, and RNF144B interacted with p21 and regulated the p21/p53 complex degradation, and finally in vivo experiments proved that HDAC3 and RNF144B promoted tumor growth. RNF144B-mediated p21 degradation regulated by HDAC3 contributed to enhancing ovarian cancer growth and metastasis.

Allyl-isothiocyanate against colorectal cancer via the mutual dependent regulation of p21 and Nrf2

Allyl-isothiocyanate (AITC) is a common Isothiocyanates (ITC) and its chemo-preventive and anti-tumor effects are believed to be related to the activation of NF-E2 p45-related Factor 2 (Nrf2). However, its anti-tumor effects on colorectal cancer (CRC) are not well elucidated. Here, we investigated the therapeutic in vitro and/or in vivo effects and mechanisms of action (MOA) for AITC on CRC cell line HCT116 (human) and MC38 (mouse). AITC treatment in a low concentration range (1 mg/kg in vivo) significantly inhibited the tumor cell growth and increased the expression of p21 and Nrf2. The AITC-mediated induction of p21 was dependent on Nrf2 but independent on p53 in vitro and in vivo at low dose. In contrast, the high dose of AITC (5 mg/kg in vivo) failed to increase substantial levels of p21/MdmX, and impaired the total antioxidant capacity of tumors and subsequent anti-tumor effect in vivo. These results suggest that an optimal dose of AITC is important and required for the proper Nrf2 activation and its anti-CRC effects and thus, providing insights into the potential applications of AITC for the prevention and treatment of CRC.

Targeting cyclin-dependent kinases in rheumatoid arthritis and psoriasis - a review of current evidence

INTRODUCTION

Rheumatoid arthritis (RA) is a chronic inflammatory disease associated with synovial proliferation and bone erosion, which leads to the structural and functional impairment of the joints. Immune cells, together with synoviocytes, induce a pro-inflammatory environment and novel treatment agents target inflammatory cytokines. Psoriasis is a chronic immune-mediated skin disease, and several cytokines are considered as typical mediators in the progression of the disease, including IL-23, IL-22, and IL-17, among others.

AREA COVERED

In this review, we try to evaluate whether cyclin-dependent kinases (CDK), enzymes that regulate cell cycle and transcription of various genes, could become novel therapeutic targets in RA and psoriasis. We present the main results of in vitro and in vivo studies, as well as scarce clinical reports.

EXPERT OPINION

CDK inhibitors seem promising for treating RA and psoriasis because of their multidirectional effects. CDK inhibitors may affect not only the process of osteoclastogenesis, thereby reducing joint destruction in RA, but also the process of apoptosis of neutrophils and macrophages responsible for the development of inflammation in both RA and psoriasis. However, assessing the efficacy of these drugs in clinical practice requires multi-center, long-term clinical trials evaluating the effectiveness and safety of CDK-blocking therapy in RA and psoriasis.

Targeting the p53 signaling pathway in cancers: Molecular mechanisms and clinical studies

Tumor suppressor p53 can transcriptionally activate downstream genes in response to stress, and then regulate the cell cycle, DNA repair, metabolism, angiogenesis, apoptosis, and other biological responses. p53 has seven functional domains and 12 splice isoforms, and different domains and subtypes play different roles. The activation and inactivation of p53 are finely regulated and are associated with phosphorylation/acetylation modification and ubiquitination modification, respectively. Abnormal activation of p53 is closely related to the occurrence and development of cancer. While targeted therapy of the p53 signaling pathway is still in its early stages and only a few drugs or treatments have entered clinical trials, the development of new drugs and ongoing clinical trials are expected to lead to the widespread use of p53 signaling-targeted therapy in cancer treatment in the future. TRIAP1 is a novel p53 downstream inhibitor of apoptosis. TRIAP1 is the homolog of yeast mitochondrial intermembrane protein MDM35, which can play a tumor-promoting role by blocking the mitochondria-dependent apoptosis pathway. This work provides a systematic overview of recent basic research and clinical progress in the p53 signaling pathway and proposes that TRIAP1 is an important therapeutic target downstream of p53 signaling.

Fullerene C60 reduces acute lung injury by suppressing oxidative stress-mediated DMBA-induced apoptosis and autophagy by regulation of cytochrome-C/caspase-3/beclin-1/IL-1α/HO-1/p53 signaling pathways in rats

The objective of this study was to evaluate the effect of fullerene C60 nanoparticles against 7,12-dimethylbenz[a]anthracene (DMBA)-induced lung tissue damage in rats. 60 Wistar albino (8 weeks old) female rats were assigned into four groups: Control Group (C), Fullerene C60, DMBA, and Fullerene C60+DMBA. The rats in the DMBA and Fullerene C60+DMBA groups were administered DMBA (45 mg/kg bw, oral gavage). The rats in Fullerene C60, and Fullerene C60+DMBA groups were administered with Fullerene C60 (1.7 mg/kg bw, oral gavage). Expression levels of cytochrome-C, caspase-3, beclin-1, IL-1α, HO-1 and p53 proteins in lung tissue were determined by western blotting, lipid peroxidation malondialdehyde (MDA) analyzes, glutathione (GSH), glutathione peroxidase (GSH-Px), catalase activity (CAT) and total protein levels were determined by spectrophotometer. In addition, lung tissues were evaluated by histopathologically. Fullerene C60 reduced the increasing of MDA and IL-1α protein expression levels and attenuated histopathological changes in lung. Moreover, fullerene C60 enhanced the protein expression of cytochrome-C, caspase-3, beclin-1, HO-1, and p53, which were decreased in the DMBA group. Fullerene C60 has strong biological activity that it might be an effective approach for lung damage.

Phosphorylation and specific DNA improved the incorporation ability of p53 into functional condensates

The transcription factor p53 acted as a critical tumor suppressor by activating the expression of various target genes to regulate diverse cellular responses. The phosphorylation of p53 influenced the binding of p53 to promotor-specific DNA and the choice of cell fate. In this study, we found that full-length wild-type p53 and pol II CTD could form heterotypic phase separation condensates in vitro. The heterotypic condensates of p53 and pol II CTD were mediated by electrostatic and hydrophobic interactions between pol II CTD and multiple domains of p53. The mobility of heterotypic p53 and pol II CTD droplets was significantly higher than that of p53 droplet. The phosphorylation promoted p53 to be recruited into pol II CTD droplets and transcription condensates. The specific DNA could further enhance the incorporation ability of p53 into functional condensates. Therefore, we proposed that the p53 droplet might be in a mediate state, the mutations resulting in p53 mutants with gain-of-function impelled the aggregate of p53, while the phosphorylation promoted p53 to be recruited into functional condensates as a client molecule to exert its function. This study might provide insights into the regulation mechanism that the phosphorylation and nuclei acid affected the phase behavior of p53.

Slug promotes p53 and p21 protein degradation by inducing Mdm2 expression in HCT116 colon cancer cells

Our previous study revealed that the tumor suppressor/transcription factor p53 directly binds to its transcriptional target, p21, and that the p53/p21 complex binds to zinc finger protein SNAI2 (Slug), a tumor promoter/transcription factor; thereby promoting the degradation of Slug by Mdm2, an E3 ligase. The present study demonstrated that Slug reduced the cellular expression levels of p53 and p21 in HCT116 colon cancer by decreasing their protein stability. In parallel, Slug increased the mRNA and protein expression levels of Mdm2 in these cells. Moreover, knockdown of Mdm2 using specific small interfering RNAs abolished the ability of Slug to induce the degradation of p53 and p21. Considering the well-known function of Mdm2 in facilitating p53 and p21 degradation, these data suggested that Slug promoted p53 and p21 degradation by inducing Mdm2 expression. Moreover, Slug increased ubiquitination levels of p53 in HCT116 cells. This is consistent with the fact that Mdm2 induces p53 degradation by ubiquitinating p53, and further confirmed that Mdm2 acted downstream of Slug. Comparative studies using HCT116 cells and their p53- or p21-knockout variants have revealed that Slug requires p21 to induce p53 degradation. This result is consistent with our previous study, which revealed that Mdm2 acts more efficiently on p53 in the p53/p21 complex compared with on p53 alone. By contrast, Slug did not require p53 to induce p21 degradation, suggesting that p53 was dispensable in Mdm2-mediated p21 degradation. Notably, the ability of Slug to increase/decrease Mdm2/p53 and p21 levels, respectively, was not confined to HCT116 cells alone, but was also confirmed in A549 and H460 lung cancer cells. Collectively, the results of the present study suggested that Slug could counter p53 and p21. The balance between these two opposing groups (Slug vs. p53/p21) may depend on environmental stresses and the internal physiology of cells.

Corilagin induces human glioblastoma U251 cell apoptosis by impeding activity of (immuno)proteasome

Glioma is a type of common primary intracranial tumor, which is difficult to treat. It has been confirmed by research that corilagin (the primary active constituent of the matsumura leafflower herb) has significant antitumor effect. In particular, our previous research demonstrated that corilagin effectively promotes apoptosis of glioma U251 cells and has a synergistic effect when used with temozolomide. However, the mechanism by which corilagin causes apoptosis in U251 cells has yet to be investigated. Proteasomes are catalytic centers of the ubiquitin-proteasome system, which is the major protein degradation pathway in eukaryotic cells; they are primarily responsible for the degradation of signal molecules, tumor suppressors, cyclins and apoptosis inhibitors and serve an important role in tumor cell proliferation and apoptosis. The present study investigated the pro-apoptotic effect of corilagin on glioma U251 cells and confirmed that decreased proteasome activity and expression levels serve an important role in corilagin-induced U251 cell apoptosis.