iASPP preferentially binds p53 proline-rich region and modulates apoptotic function of codon 72-polymorphic p53

Ferroptosis-associated genes and compounds in renal cell carcinoma

As the main type of renal cell carcinoma (RCC), clear cell RCC (ccRCC) is often associated with the deletion or mutation of the von Hippel Lindau (VHL) gene, enhancement of glucose and lipid metabolism, and heterogeneity of the tumor microenvironment. VHL alterations in RCC cells lead to the activation of hypoxia-inducible factors and their downstream target vascular endothelial growth factor, and to the reprogramming of multiple cell death pathways and metabolic weakness, including ferroptosis, which are associated with targeted therapy or immunotherapy. The changes in biological metabolites (e.g., iron and lipids) support ferroptosis as a potential therapeutic strategy for RCC, while iron metabolism and ferroptosis regulation have been examined as anti-RCC agents in numerous studies, and various ferroptosis-related molecules have been shown to be related to the metastasis and prognosis of ccRCC. For example, glutathione peroxidase 4 and glutaminase inhibitors can inhibit pyrimidine synthesis and increase reactive oxygen species levels in VHL-deficient RCC cells. In addition, the release of damage-associated molecular patterns by tumor cells undergoing ferroptosis also mediates antitumor immunity, and immune therapy can synergize with targeted therapy or radiotherapy through ferroptosis. However, Inducing ferroptosis not only suppresses cancer, but also promotes cancer development due to its potential negative effects on anti-cancer immunity. Therefore, ferroptosis and various tumor microenviroment-related molecules may co-occur during the development and treatment of RCC, and further understanding of the interactions, core targets, and related drugs of ferroptosis may provide new combination drug strategies for RCC treatment. Here we summarize the key genes and compounds on ferroptosis and RCC in order to envision future treatment strategies and to provide sufficient information for overcoming RCC resistance through ferroptosis.

Inhibitor of apoptosis stimulating protein of p53 protects against MPP+-induced neurotoxicity of dopaminergic neurons

Inhibitor of apoptosis stimulating protein of p53 (iASPP) is related to the pathogenesis of several neurological disorders by affecting the oxidative stress and survival of neurons. However, whether iASPP has a role in Parkinson disease (PD) remains to be determined. This work explored the potential regulatory effect of iASPP in an in vitro model of PD based on 1-methyl-4-phenylpyridinium (MPP+)-evoked neurotoxicity of dopaminergic neurons in culture. MN9D neurons were treated with MPP+ at 200 µM in the culture media for 24 h to induce neurotoxicity. Overexpression and silencing of iASPP in neurons were achieved by infecting recombinant adenovirus expressing iASPP and sh-iASPP, respectively. Protein expression was examined by immunoblotting. MPP+-evoked neurotoxicity of dopaminergic neurons was determined by cell viability, TUNEL, and flow cytometric assays. The transcriptional activity of nuclear erythroid factor 2-like 2 (Nrf2) was assessed by luciferase reporter assay. Kelch-like ECH-associated protein 1 (Keap1)-knockout neurons were generated by lentiCRISPR/Cas9-Keap1 constructs. Expression levels of iASPP declined in MPP+-stimulated neurons. Overexpression of iASPP in neurons exhibited inhibitory effects on MPP+-evoked apoptosis, α-synuclein accumulation, and oxidative stress, while iASPP-deficient neurons were more sensitive to MPP+-induced neurotoxicity. Overexpression of iASPP led to an enhancing effect on Nrf2 activation in MPP+-stimulated neurons. Mechanism research revealed that iASPP may contribute to the activation of Nrf2 by competing with Nrf2 in binding with Keap1. Notably, the regulatory effect of iASPP on Nrf2 was diminished in Keap1-knockout neurons. The chemical inhibition of Nrf2 or knockdown of Nrf2 abrogated the protective effects of iASPP on MPP+-induced neurotoxicity. To conclude, iASPP protects dopaminergic neurons against MPP+-induced neurotoxicity through modulation of the Keap1/Nrf2 axis. Therefore, iASPP may play a crucial role in mediating the loss of dopaminergic neurons in PD, and targeting the iASPP-Nrf2 axis could be a promising strategy for treating PD.

Multiple TP53 p.R337H haplotypes and implications for tumor susceptibility

The germline TP53 p.R337H mutation is reported as the most common germline TP53 variant. It exists at a remarkably high frequency in the population of southeast Brazil as founder mutation in two distinct haplotypes with the most frequent co-segregating with the p.E134∗ variant of the XAF1 tumor suppressor and an increased cancer risk. Founder mutations demonstrate linkage disequilibrium with neighboring genetic polymorphic markers that can be used to identify the founder variant in different geographic regions and diverse populations. We report here a shared haplotype among Brazilian, Portuguese, and Spanish families and the existence of three additional distinct TP53 p.R337H alleles. Mitochondrial DNA sequencing and Y-STR profiling of Brazilian carriers of the founder TP53 p.R337H allele reveal an excess of Native American haplogroups in maternal lineages and exclusively European haplogroups in paternal lineages, consistent with communities established through male European settlers with extensive intermarriage with Indigenous women. The identification of founder and independent TP53 p.R337H alleles underlines the importance for considering the haplotype as a functional unit and the additive effects of constitutive polymorphisms and associated variants in modifier genes that can influence the cancer phenotype.

Evaluation of apoptosis stimulating protein of TP53-1 (ASPP1/PPP1R13B) to predict therapy resistance and overall survival in acute myeloid leukemia (AML)

ASPP1 (PPP1R13B) belongs to a family of p53-binding proteins and enhances apoptosis by stimulation of p53-transactivation of selected proapoptotic target genes. It is preferentially expressed in hematopoietic stem cells (HSC) and together with p53 preserves the genomic integrity of the HSC pool. Consequently, dysfunction of ASPP1 has been associated with malignant transformation and development of acute lymphoblastic leukemias and lymphomas - whereas methylation of the promoter region is linked to reduced transcription and ultimately attenuated expression of ASPP1. The role of ASPP1 in AML is not known. We now show that impaired regulation of PPP1R13B contributes to the biology of leukemogenesis and primary therapy resistance in AML. PPP1R13B mRNA expression patterns thereby define a distinct prognostic profile - which is not reflected by the European leukemia net (ELN) risk score. These findings have direct therapeutic implications and we provide a strategy to restore ASPP1 protein levels using hypomethylating agents to sensitize cells towards proapoptotic drugs. Prospective clinical trials are warranted to investigate the role of ASPP1 (PPP1R13B) as a biomarker for risk stratification and as a potential therapeutic target to restore susceptibility to chemotherapy.

Significant association of BRCA1 (rs1799950), BRCA2 (rs144848) and TP53 (rs1042522) polymorphism with breast cancer risk in Pashtun population of Khyber Pakhtunkhwa, Pakistan

BACKGROUND

Single nucleotide polymorphism (SNPs) in BRCA1, BRCA2 and TP53 has been widely associated with breast cancer risk in different ethnicities with inconsistent results. There is no such study conducted so far in the Pashtun population of Khyber Pakhtunkhwa, Pakistan. Therefore, this study was conducted to check BRCA1 (rs1799950), BRCA2 (rs144848) and TP53 (rs1042522) polymorphism with breast cancer risk in Pashtun population of Khyber Pakhtunkhwa, Pakistan.

METHODS

This study, consisting 140 breast cancer patients and 80 gender and age matched healthy controls were subjected to confirm BRCA1, BRCA2 and TP53 polymorphism. Clinicopathological data and blood samples were taken from all the participants. DNA was extracted and SNPs were confirmed using T-ARMS-PCR protocol.

RESULTS

Our data indicated that BRCA1, BRCA2, and TP53 selected SNPs risk allele and risk allele containing genotypes displayed significant association (p < 0.05) with breast cancer risk in the Pashtun population of Khyber Pakhtunkhwa, Pakistan.

CONCLUSION

All the three selected SNPs of BRCA1, BRCA2 and TP53 showed significant association with breast cancer risk in the Pashtun population of Khyber Pakhtunkhwa, Pakistan. However, more investigation will be required on large data sets to confirm the selected SNPs and other SNPs in the selected and other related genes with the risk of breast cancer.

Targeting p53 pathways: mechanisms, structures, and advances in therapy

The TP53 tumor suppressor is the most frequently altered gene in human cancers, and has been a major focus of oncology research. The p53 protein is a transcription factor that can activate the expression of multiple target genes and plays critical roles in regulating cell cycle, apoptosis, and genomic stability, and is widely regarded as the "guardian of the genome". Accumulating evidence has shown that p53 also regulates cell metabolism, ferroptosis, tumor microenvironment, autophagy and so on, all of which contribute to tumor suppression. Mutations in TP53 not only impair its tumor suppressor function, but also confer oncogenic properties to p53 mutants. Since p53 is mutated and inactivated in most malignant tumors, it has been a very attractive target for developing new anti-cancer drugs. However, until recently, p53 was considered an "undruggable" target and little progress has been made with p53-targeted therapies. Here, we provide a systematic review of the diverse molecular mechanisms of the p53 signaling pathway and how TP53 mutations impact tumor progression. We also discuss key structural features of the p53 protein and its inactivation by oncogenic mutations. In addition, we review the efforts that have been made in p53-targeted therapies, and discuss the challenges that have been encountered in clinical development.

Hyaluronan-Induced CD44-iASPP Interaction Affects Fibroblast Migration and Survival

In the present study, we show that the inhibitor of the apoptosis-stimulating protein of p53 (iASPP) physically interacts with the hyaluronan receptor CD44 in normal and transformed cells. We noticed that the CD44 standard isoform (CD44s), but not the variant isoform (CD44v), bound to iASPP via the ankyrin-binding domain in CD44s. The formation of iASPP-CD44s complexes was promoted by hyaluronan stimulation in fibroblasts but not in epithelial cells. The cellular level of p53 affected the amount of the iASPP-CD44 complex. iASPP was required for hyaluronan-induced CD44-dependent migration and adhesion of fibroblasts. Of note, CD44 altered the sub-cellular localization of the iASPP-p53 complex; thus, ablation of CD44 promoted translocation of iASPP from the nucleus to the cytoplasm, resulting in increased formation of a cytoplasmic iASPP-p53 complex in fibroblasts. Overexpression of iASPP decreased, but CD44 increased the level of intracellular reactive oxygen species (ROS). Knock-down of CD44s, in the presence of p53, led to increased cell growth and cell density of fibroblasts by suppression of p27 and p53. Our observations suggest that the balance of iASPP-CD44 and iASPP-p53 complexes affect the survival and migration of fibroblasts.

Mutant Ras and inflammation-driven skin tumorigenesis is suppressed via a JNK-iASPP-AP1 axis

Concurrent mutation of a RAS oncogene and the tumor suppressor p53 is common in tumorigenesis, and inflammation can promote RAS-driven tumorigenesis without the need to mutate p53. Here, we show, using a well-established mutant RAS and an inflammation-driven mouse skin tumor model, that loss of the p53 inhibitor iASPP facilitates tumorigenesis. Specifically, iASPP regulates expression of a subset of p63 and AP1 targets, including genes involved in skin differentiation and inflammation, suggesting that loss of iASPP in keratinocytes supports a tumor-promoting inflammatory microenvironment. Mechanistically, JNK-mediated phosphorylation regulates iASPP function and inhibits iASPP binding with AP1 components, such as JUND, via PXXP/SH3 domain-mediated interaction. Our results uncover a JNK-iASPP-AP1 regulatory axis that is crucial for tissue homeostasis. We show that iASPP is a tumor suppressor and an AP1 coregulator.

Targeting Protein Interaction Hotspots Using Structured and Disordered Chimeric Peptide Inhibitors

The main challenge in inhibiting protein-protein interactions (PPI) for therapeutic purposes is designing molecules that bind specifically to the interaction hotspots. Adding to the complexity, such hotspots can be within both structured and disordered interaction interfaces. To address this, we present a strategy for inhibiting the structured and disordered hotspots of interactions using chimeric peptides that contain both structured and disordered parts. The chimeric peptides we developed are comprised of a cyclic structured part and a disordered part, which target both disordered and structured hotspots. We demonstrate our approach by developing peptide inhibitors for the interactions of the antiapoptotic iASPP protein. First, we developed a structured, α-helical stapled peptide inhibitor, derived from the N-terminal domain of MDM2. The peptide bound two hotspots on iASPP at the low micromolar range and had a cytotoxic effect on A2780 cancer cells with a half-maximal inhibitory concentration (IC₅₀) value of 10 ± 1 μM. We then developed chimeric peptides comprising the structured stapled helical peptide and the disordered p53-derived LinkTer peptide that we previously showed to inhibit iASPP by targeting its disordered RT loop. The chimeric peptide targeted both structured and disordered domains in iASPP with higher affinity compared to the individual structured and disordered peptides and caused cancer cell death. Our strategy overcomes the inherent difficulty in inhibiting the interactions of proteins that possess structured and disordered regions. It does so by using chimeric peptides derived from different interaction partners that together target a much wider interface covering both the structured and disordered domains. This paves the way for developing such inhibitors for therapeutic purposes.

A Critical Function for the Transcription Factors GLI1 and GLI2 in the Proliferation and Survival of Human Mast Cells

Mast cell hyperactivity and accumulation in tissues are associated with allergy and other mast cell-related disorders. However, the molecular pathways regulating mast cell survival in homeostasis and disease are not completely understood. As glioma-associated oncogene (GLI) proteins are involved in both tissue homeostasis and in the hematopoietic system by regulating cell fate decisions, we sought to investigate the role for GLI proteins in the control of proliferation and survival of human mast cells. GLI1 transcripts were present in primary human mast cells and mast cell lines harboring or not activating mutations in the tyrosine kinase receptor KIT (HMC-1.1 and HMC-1.2, and LAD2 cells, respectively), while GLI2 transcripts were only present in HMC-1.1 and HMC-1.2 cells, suggesting a role for oncogenic KIT signaling in the regulation of GLI2. Reduction in GLI activity by small molecule inhibitors, or by shRNA-mediated knockdown of GLI1 or GLI2, led to increases in apoptotic cell death in both cultured human and murine mast cells, and reduced the number of peritoneal mast cells in mice. Although GLI proteins are typically activated via the hedgehog pathway, steady-state activation of GLI in mast cells occurred primarily via non-canonical pathways. Apoptosis induced by GLI silencing was associated with a downregulation in the expression of KIT and of genes that influence p53 stability and function including USP48, which promotes p53 degradation; and iASPP, which inhibits p53-induced transcription, thus leading to the induction of p53-regulated apoptotic genes. Furthermore, we found that GLI silencing inhibited the proliferation of neoplastic mast cell lines, an effect that was more pronounced in rapidly growing cells. Our findings support the conclusion that GLI1/2 transcription factors are critical regulators of mast cell survival and that their inhibition leads to a significant reduction in the number of mast cells in vitro and in vivo, even in cells with constitutively active KIT variants. This knowledge can potentially be applicable to reducing mast cell burden in mast cell-related diseases.

ASPP2κ Is Expressed In Human Colorectal Carcinoma And Promotes Chemotherapy Resistance And Tumorigenesis

Alternative splicing is a common physiologic mechanism to generate numerous distinct gene products from one gene locus, which can result in unique gene products with differing important functional outcomes depending on cell context. Aberrant alternative splicing is a hallmark of cancer that can contribute to oncogenesis and aggressiveness of the disease as well as resistance to therapy. However, aberrant splicing might also result in novel targets for cancer therapy. ASPP2 is a haplo-insufficient tumor suppressor, that functions through both p53-dependent as well as p53-independent mechanisms to enhance cell death after stress. Interestingly, the common human tumor TP53 mutations result in a loss of the binding sites to ASPP2, leading to impaired induction of apoptosis. Vice versa, attenuation of ASPP2 has been described to be associated with high-risk disease, therapy failure and poor clinical outcome especially in tumors harboring the TP53 wildtype (WT) isoform. We have recently identified a novel, dominant-negative splicing variant of ASPP2, named ASPP2κ, with oncogenic potential. Exon-skipping results in a reading-frame shift with a premature translation stop, omitting most of the ASPP2 C-terminus - which harbors the p53-binding domain. Consequently, the ASPP2-p53 interaction is abrogated, which in part impacts on oncogenesis, aggressiveness of disease and response to therapy. Since ASPP2κ has been shown in hematologic malignancies to promote tumorigenesis, we further wished to determine if aberrant ASPP2κ expression plays a role in human solid tumors. In this report, we find that ASPP2κ is frequently expressed in human colorectal tumors (CRC). Using ASPP2κ overexpressing and interference CRC models, we demonstrate a functional role of ASPP2κ in contributing to oncogenesis and resistance to therapy in CRC by 1) enhancing proliferation, 2) promoting cell migration and, 3) conferring resistance to chemotherapy induced apoptosis. Our findings have far-reaching consequences for future diagnostic and therapeutic strategies for ASPP2κ expressing colorectal cancer patients and provide proof-of-principle to further explore ASPP2κ as potential predictive marker and target for therapy in clinical trials.

Effect of the p53 P72R Polymorphism on Mutant TP53 Allele Selection in Human Cancer

BACKGROUND

TP53 mutations occur in more than 50% of cancers. We sought to determine the effect of the intragenic P72R single nucleotide polymorphism (SNP; rs1042522) on the oncogenic properties of mutant p53.

METHODS

P72R allelic selection in tumors was determined from genotype calls and a Gaussian distributed mixture model. The SNP effect on mutant p53 was determined in p53-negative cancer cell lines. RNA-sequencing, chromatin immunoprecipitation, and survival analysis were performed to describe the SNP effect. All statistical tests were 2-sided.

RESULTS

Among 409 patients with germline heterozygous P72R SNP who harbored somatic mutations in TP53, we observed a selection bias against missense TP53 mutants encoding the P72 SNP (P = 1.64 x 10-13). Exogenously expressed hotspot p53 mutants with the P72 SNP were negatively selected in cancer cells. Gene expression analyses showed the enrichment of p53 pathway genes and inflammatory genes in cancer cells transduced with mutants encoding P72 SNP. Immune gene signature is enriched in patients harboring missense TP53 mutations with homozygous P72 SNP. These patients have improved overall survival as compared with those with the R72 SNP (P = .04).

CONCLUSION

This is the largest study demonstrating a selection against the P72 SNP. Missense p53 mutants with the P72 SNP retain partial wild-type tumor-suppressive functions, which may explain the selection bias against P72 SNP across cancer types. Ovarian cancer patients with the P72 SNP have a better prognosis than with the R72 SNP. Our study describes a previously unknown role through which the rs1042522 SNP modifies tumor suppressor activities of mutant p53 in patients.

Nuclear iASPP determines cell fate by selectively inhibiting either p53 or NF-κB

p53 and NF-κBp65 are essential transcription factors (TFs) in the cellular response to stress. Two signaling systems can often be entwined together and generally produce opposing biological outcomes in a cell context-dependent manner. Inhibitor of apoptosis-stimulating protein of p53 (iASPP) has the potential to inhibit both p53 and NF-κBp65, yet how such activities of iASPP are integrated with cancer remains unknown. Here, we utilized different cell models with diverse p53/NF-κBp65 activities. An iASPP(295–828) mutant, which is exclusively located in the nucleus and has been shown to be essential for its inhibitory effects on p53/NF-κBp65, was used to investigate the functional interaction between iASPP and the two TFs. The results showed that iASPP inhibits apoptosis under conditions when p53 is activated, while it can also elicit a proapoptotic effect when NF-κBp65 alone is activated. Furthermore, we demonstrated that iASPP inhibited the transcriptional activity of p53/NF-κBp65, but with a preference toward p53, thereby producing an antiapoptotic outcome when both TFs were simultaneously activated. This may be due to stronger binding between p53 and iASPP than NF-κBp65 and iASPP. Overall, these findings provide important insights into how the activities of p53 and NF-κBp65 are modulated by iASPP. Despite being a well-known oncogene, iASPP may have a proapoptotic role, which will guide the development of iASPP-targeted therapies to reach optimal outcomes in the future.

Sufentanil Protects the Liver from Ischemia/Reperfusion-Induced Inflammation and Apoptosis by Inhibiting ATF4-Induced TP53BP2 Expression

Liver ischemia-reperfusion (I/R) injury is a pathological process that often occurs during liver and trauma surgery. This study aimed to investigate the protective effect and potential mechanisms of sufentanil on hepatic I/R injury. I/R rat model and hypoxic/reoxygenation (H/R)-induced buffalo rat liver (BRL)-3A cell model were established. Following pretreatment with sufentanil, the enzymatic activities of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in rat serum and the changes of hepatic histopathology were evaluated to track the extent of liver injury. The levels of inflammatory factors were determined with ELISA kits and RT-qPCR. The infiltration of macrophages was assessed after detecting monocyte chemoattractant protein 1 (MCP-1) and F4/80 expression. Additionally, apoptosis was measured by means of TUNEL staining, and gene expression related to apoptosis was examined using RT-qPCR and western blotting. Then, TP53BP2 was overexpressed in BRL-3A cells exposed to H/R condition to evaluate whether sufentanil defended the liver against injury by regulating TP53BP2 expression. Moreover, the potential binding site of ATF4 on the TP53BP2 promoter was analyzed using JASPAR databases and verified by chromosomal immunoprecipitation (ChIP) assay. Furthermore, TP53BP2 expression and endoplasmic reticulum stress (ERS)-related protein levels were determined after ATF4 was overexpressed in sufentanil-treated BRL-3A cells. Results revealed that sufentanil significantly improved hepatic I/R injury, decreased the levels of inflammatory factors, and alleviated hepatocyte apoptosis. Notably, upregulated TP53BP2 expression was observed in hepatic tissues, and TP53BP2 overexpression markedly reversed the protective effects of sufentanil on the inflammation and apoptosis in H/R-stimulated BRL-3A cells. Additionally, ATF4 was confirmed to combine with the TP53BP2 promoter. ATF4 upregulation attenuated the inhibitory effects of sufentanil on the expression of TP53BP2 and ERS-associated proteins. These findings demonstrated that sufentanil protects the liver from inflammation and apoptosis injury induced by I/R by inhibiting ATF4 expression and further suppressing TP53BP2 expression, suggesting a promising therapeutic candidate for the treatment of liver I/R injury.

Association Between Arg72Pro Polymorphism in TP53 and Malignant Abdominal Solid Tumor Risk in Hunan Children

Pediatric solid tumors are heterogeneous and comprise various histological subtypes. TP53, a tumor suppressor, orchestrates the transcriptional activation of anti-cancer genes. The gene coding for this protein is highly polymorphic, and its mutations are associated with cancer development. The Arg72Pro polymorphism in TP53 has been associated with susceptibility to various types of cancer. Here, in this hospital-based study, we evaluated the association of this polymorphism with susceptibility toward malignant abdominal solid tumors in children in the Hunan province of China. We enrolled 162 patients with neuroblastoma, 60 patients with Wilms' tumor, and 28 patients with hepatoblastoma as well as 270 controls. Genotypes were determined using a TaqMan assay, and the strength of the association was assessed using an odds ratio, within a 95% confidence interval identified using logistic regression models. Our results showed that the Arg72Pro polymorphism did not exhibit significant association with susceptibility toward pediatric malignant abdominal solid tumors. Stratification analysis revealed that this polymorphism exerts weak sex- and age-specific effects on Wilms' tumor and hepatoblastoma susceptibility, respectively. Overall, our results indicate that the Arg72Pro polymorphism may have a marginal effect on susceptibility toward pediatric malignant abdominal solid tumors in Hunan, and this finding warrants further confirmation.

The P72R Polymorphism in R248Q/W p53 Mutants Modifies the Mutant Effect on Epithelial to Mesenchymal Transition Phenotype and Cell Invasion via CXCL1 Expression

High-grade serous carcinoma (HGSC), the most lethal subtype of epithelial ovarian cancer (EOC), is characterized by widespread TP53 mutations (>90%), most of which are missense mutations (>70%). The objective of this study was to investigate differential transcriptional targets affected by a common germline P72R SNP (rs1042522) in two p53 hotspot mutants, R248Q and R248W, and identify the mechanism through which the P72R SNP affects the neomorphic properties of these mutants. Using isogenic cell line models, transcriptomic analysis, xenografts, and patient data, we found that the P72R SNP modifies the effect of p53 hotspot mutants on cellular morphology and invasion properties. Most importantly, RNA sequencing studies identified CXCL1 a critical factor that is differentially affected by P72R SNP in R248Q and R248W mutants and is responsible for differences in cellular morphology and functional properties observed in these p53 mutants. We show that the mutants with the P72 SNP promote a reversion of the EMT phenotype to epithelial characteristics, whereas its R72 counterpart promotes a mesenchymal transition via the chemokine CXCL1. These studies reveal a new role of the P72R SNP in modulating the neomorphic properties of p53 mutants via CXCL1, which has significant implications for tumor invasion and metastasis.

YB-1 Knockdown Inhibits the Proliferation of Mesothelioma Cells through Multiple Mechanisms

Y-box binding protein-1 (YB-1) is a multifunctional oncoprotein that has been shown to regulate proliferation, invasion and metastasis in a variety of cancer types. We previously demonstrated that YB-1 is overexpressed in mesothelioma cells and its knockdown significantly reduces tumour cell proliferation, migration, and invasion. However, the mechanisms driving these effects are unclear. Here, we utilised an unbiased RNA-seq approach to characterise the changes to gene expression caused by loss of YB-1 knockdown in three mesothelioma cell lines (MSTO-211H, VMC23 and REN cells). Bioinformatic analysis showed that YB-1 knockdown regulated 150 common genes that were enriched for regulators of mitosis, integrins and extracellular matrix organisation. However, each cell line also displayed unique gene expression signatures, that were differentially enriched for cell death or cell cycle control. Interestingly, deregulation of STAT3 and p53-pathways were a key differential between each cell line. Using flow cytometry, apoptosis assays and single-cell time-lapse imaging, we confirmed that MSTO-211H, VMC23 and REN cells underwent either increased cell death, G1 arrest or aberrant mitotic division, respectively. In conclusion, this data indicates that YB-1 knockdown affects a core set of genes in mesothelioma cells. Loss of YB-1 causes a cascade of events that leads to reduced mesothelioma proliferation, dependent on the underlying functionality of the STAT3/p53-pathways and the genetic landscape of the cell.

Targeting an Interaction Between Two Disordered Domains by Using a Designed Peptide

Intrinsically disordered regions in proteins (IDRs) mediate many disease-related protein-protein interactions. However, the unfolded character and continuous conformational changes of IDRs make them difficult to target for therapeutic purposes. Here, we show that a designed peptide based on the disordered p53 linker domain can be used to target a partner IDR from the anti-apoptotic iASPP protein, promoting apoptosis of cancer cells. The p53 linker forms a hairpin-like structure with its two termini in close proximity. We designed a peptide derived from the disordered termini without the hairpin, designated as p53 LinkTer. The LinkTer peptide binds the disordered RT loop of iASPP with the same affinity as the parent p53 linker peptide, and inhibits the p53-iASPP interaction in vitro. The LinkTer peptide shows increased stability to proteolysis, penetrates cancer cells, causes nuclei shrinkage, and compromises the viability of cells. We conclude that a designed peptide comprising only the IDR from a peptide sequence can serve as an improved inhibitor since it binds its target protein without the need for pre-folding, paving the way for therapeutic targeting of IDRs.

Increases of iASPP-Keap1 interaction mediated by syringin enhance synaptic plasticity and rescue cognitive impairments via stabilizing Nrf2 in Alzheimer's models

Oxidative stress is an important pathogenic manifestation of Alzheimer's disease (AD) that contributes to synaptic dysfunction, which precedes Aβ accumulation and neurofibrillary tangle formation. However, the molecular machineries that govern the decline of antioxidative defence in AD remains to be elucidated, and effective candidate for AD treatment is limited. Here, we showed that the decreases in the inhibitor of apoptosis-stimulating protein of p53 (iASPP) was associated with the vulnerability to oxidative stress in the amyloid precursor protein (APP)/presenilin 1 (PS1) mouse brain. Treatment with an antioxidant, syringin, could ameliorate AD-related pathologic and behavioural impairments. Interestingly, syringin treatment resulted in an upregulation of iASPP and the increase in the interaction of iASPP with Kelchlike ECH-associating protein 1 (Keap1). Syringin reduced neuronal apoptosis independently of p53. We confirmed that syringin-induced enhancement of antioxidant defenses involved the stabilization of Nrf2 in overexpressing human Swedish mutant APP (APPswe) cells in vitro. Syringin-mediated Nrf2 nuclear translocation facilitated the activation of the Nrf2 downstream genes via iASPP/Nrf2 axis. Our results demonstrate that syringin-mediated increases of iASPP-Keap1 interaction restore cellular redox balance. Further study on the syringin-iASPP interactions may help in understanding the regulatory mechanism and designing novel potent modulators for AD treatment.

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Poor expression of iASPP is associated with the serious accumulation of β-amyloid.

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Syringin reduces Aβ production and mitigates cognitive deficits by amending redox.

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Syringin-caused increases of iASPP facilitate the activation of NADPH and γGCL-C.

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Syringin protects neuronal cells against oxidative stress via iASPP/Nrf2 axis.

Endometrial receptivity and pregnancy outcome

Human implantation is a highly complex and multifactorial process. Successful implantation requires the presence of a healthy embryo, a receptive endometrium, and a synchronized molecular dialogue between the two, as well as immune tolerance/protection from the host. The endometrial receptivity refers to a hormonally limited period in which the endometrial tissue acquires a transient functional status allowing blastocyst implantation and pregnancy initiation. Global knowledge of endometrial receptivity grew up in recent years. Improvements in genetics, new biomarkers, noninvasive methods, new advanced techniques (Endometrial receptivity assay - the ERA system, proteomic analysis) offer the possibility to evaluate the endometrial status and to manage patients with infertility problems, especially women undergoing assisted reproductive treatment. This overview reports the most relevant knowledge and recent advances in the study of implantation processes from the perspective of the endometrium, often considered as being the main barrier for a successful pregnancy initiation. Endometrial receptivity is a topic of great interest and further studies are needed for the early identification of endometrial abnormalities and the discovery of new strategies for increasing the chance for the establishment of pregnancy.

Susceptibility of Multiple Primary Cancers in Patients With Head and Neck Cancer: Nature or Nurture?

Multiple primary cancers (MPCs) are major obstacles to long-term survival in head and neck cancer (HNSCC), however, the molecular mechanism underlying multiple carcinogenesis remains unclear. “Field cancerization” is a classical theory to elaborate the malignant progression of MPCs. Apart from environmental and immune factors, genetic factors may have great potential as molecular markers for MPCs risk prediction. This review focuses on inherited and acquired gene mutations in MPCs, including germ-line mutation, single-nucleotide polymorphism, chromosomal instability, microsatellite instability and DNA methylation. And definition and prognosis of MPCs have also been discussed. These may pave the way for the early detection, prevention and effective treatment of MPCs in HNSCC.

iASPP mediates p53 selectivity through a modular mechanism fine-tuning DNA recognition

The most frequently mutated protein in human cancer is p53, a transcription factor (TF) that regulates myriad genes instrumental in diverse cellular outcomes including growth arrest and cell death. Cell context-dependent p53 modulation is critical for this life-or-death balance, yet remains incompletely understood. Here we identify sequence signatures enriched in genomic p53-binding sites modulated by the transcription cofactor iASPP. Moreover, our p53-iASPP crystal structure reveals that iASPP displaces the p53 L1 loop-which mediates sequence-specific interactions with the signature-corresponding base-without perturbing other DNA-recognizing modules of the p53 DNA-binding domain. A TF commonly uses multiple structural modules to recognize its cognate DNA, and thus this mechanism of a cofactor fine-tuning TF-DNA interactions through targeting a particular module is likely widespread. Previously, all tumor suppressors and oncoproteins that associate with the p53 DNA-binding domain-except the oncogenic E6 from human papillomaviruses (HPVs)-structurally cluster at the DNA-binding site of p53, complicating drug design. By contrast, iASPP inhibits p53 through a distinct surface overlapping the E6 footprint, opening prospects for p53-targeting precision medicine to improve cancer therapy.

Flexible Tethering of ASPP Proteins Facilitates PP-1c Catalysis

ASPP (apoptosis-stimulating proteins of p53) proteins bind PP-1c (protein phosphatase 1) and regulate p53 impacting cancer cell growth and apoptosis. Here we determine the crystal structure of the oncogenic ASPP protein, iASPP, bound to PP-1c. The structure reveals a 1:1 complex that relies on interactions of the iASPP SILK and RVxF motifs with PP-1c, plus interactions of the PP-1c PxxPxR motif with the iASPP SH3 domain. Small-angle X-ray scattering analyses suggest that the crystal structure undergoes slow interconversion with more extended conformations in solution. We show that iASPP, and the tumor suppressor ASPP2, enhance the catalytic activity of PP-1c against the small-molecule substrate, pNPP as well as p53. The combined results suggest that PxxPxR binding to iASPP SH3 domain is critical for complex formation, and that the modular ASPP-PP-1c interface provides dynamic flexibility that enables functional binding and dephosphorylation of p53 and other diverse protein substrates.

miR-219a-5p Ameliorates Hepatic Ischemia/Reperfusion Injury via Impairing TP53BP2

BACKGROUND

Hepatic ischemia/reperfusion (I/R) injury is a serious complication that occurs upon hypovolemic shock, liver resection, and transplantation. A significant age-dependent difference in the injury response to hepatic I/R in both human and animal models has been reported. Nevertheless, the molecular mechanism is currently unclear.

AIMS

To clarify the reason why aged animals or people were more vulnerable to hepatic I/R injury.

METHODS

In the present study, we found decreased miR-219a-5p expression in the old mice more vulnerable to hepatic I/R injury. Administrated with agomir-miR-219a-5p diminished the severity of hepatic I/R injury in old mice, as indicated by lower serum ALT and AST, oxidative parameters including MDA, TOA, and OSI, and decreased apoptotic cell number. The effect of miR-219a-5p was also confirmed in the H₂O₂-induced apoptosis model in AML-12 and NCTC1469 cells. After miR-219a-5p overexpression, two key apoptosis-related proteins Bax and P21, target genes of TP53, were decreased. Furthermore, TP53BP2 interacts with p53 family members and promotes their transcriptional activities toward pro-apoptosis genes.

RESULTS

RNA sequencing, western blot, and luciferase reporter assay proved that TP53BP2, a crucial TP53 transcriptional activity enhancer in vivo, was directly regulated by miR-219a-5p.

CONCLUSIONS

In summary, our study demonstrated that age-related miR-219a-5p can attenuate hepatic I/R injury through inhibiting TP53BP2 and downstream TP53-dependent apoptosis of hepatic cells in mice.

The Spatiotemporal Pattern and Intensity of p53 Activation Dictates Phenotypic Diversity in p53-Driven Developmental Syndromes

Inappropriate activation of the p53 transcription factor contributes to numerous developmental syndromes characterized by distinct constellations of phenotypes. How p53 drives exquisitely specific sets of symptoms in diverse syndromes, however, remains enigmatic. Here, we deconvolute the basis of p53-driven developmental syndromes by leveraging an array of mouse strains to modulate the spatial expression pattern, temporal profile, and magnitude of p53 activation during embryogenesis. We demonstrate that inappropriate p53 activation in the neural crest, facial ectoderm, anterior heart field, and endothelium induces distinct spectra of phenotypes. Moreover, altering the timing and degree of p53 hyperactivation substantially affects the phenotypic outcomes. Phenotypes are associated with p53-driven cell-cycle arrest or apoptosis, depending on the cell type, with gene expression programs, rather than extent of mitochondrial priming, largely governing the specific response. Together, our findings provide a critical framework for decoding the role of p53 as a mediator of diverse developmental syndromes.

A helical lock and key model of polyproline II conformation with SH3

Motivation

More than half of the human proteome contains the proline-rich motif, PxxP. This motif has a high propensity for adopting a left-handed polyproline II (PPII) helix and can potentially bind SH3 domains. SH3 domains are generally grouped into two classes, based on whether the PPII binds in a positive (N-to-C terminal) or negative (C-to-N terminal) orientation. Since the discovery of this structural motif, over six decades ago, a systematic understanding of its binding remains poor and the consensus amino acid sequence that binds SH3 domains is still ill defined.

Results

Here, we show that the PPII interaction with SH3 domains is governed by the helix backbone and its prolines, and their rotation angle around the PPII helical axis. Based on a geometric analysis of 131 experimentally solved SH3 domains in complex with PPIIs, we observed a rotary translation along the helical screw axis, and separated them by 120° into three categories we name α (0–120°), β (120–240°) and γ (240–360°). Furthermore, we found that PPII helices are distinguished by a shifting PxxP motif preceded by positively charged residues which act as a structural reading frame and dictates the organization of SH3 domains; however, there is no one single consensus motif for all classified PPIIs. Our results demonstrate a remarkable apparatus of a lock with a rotating and translating key with no known equivalent machinery in molecular biology. We anticipate our model to be a starting point for deciphering the PPII code, which can unlock an exponential growth in our understanding of the relationship between protein structure and function.

Availability and implementation

We have implemented the proposed methods in the R software environment and in an R package freely available at https://github.com/Grantlab/bio3d.

Supplementary information

Supplementary data are available at Bioinformatics online.

Alternative splicing of the tumor suppressor ASPP2 results in a stress-inducible, oncogenic isoform prevalent in acute leukemia

Background

Apoptosis-stimulating Protein of TP53-2 (ASPP2) is a tumor suppressor enhancing TP53-mediated apoptosis via binding to the TP53 core domain. TP53 mutations found in cancers disrupt ASPP2 binding, arguing for an important role of ASPP2 in TP53-mediated tumor suppression. We now identify an oncogenic splicing variant, ASPP2κ, with high prevalence in acute leukemia.

Methods

An mRNA screen to detect ASPP2 splicing variants was performed and ASPP2κ was validated using isoform-specific PCR approaches. Translation into a genuine protein isoform was evaluated after establishing epitope-specific antibodies. For functional studies cell models with forced expression of ASPP2κ or isoform-specific ASPP2κ-interference were created to evaluate proliferative, apoptotic and oncogenic characteristics of ASPP2κ.

Findings

Exon skipping generates a premature stop codon, leading to a truncated C-terminus, omitting the TP53-binding sites. ASPP2κ translates into a dominant-negative protein variant impairing TP53-dependent induction of apoptosis. ASPP2κ is expressed in CD34+ leukemic progenitor cells and functional studies argue for a role in early oncogenesis, resulting in perturbed proliferation and impaired induction of apoptosis, mitotic failure and chromosomal instability (CIN) – similar to TP53 mutations.

Importantly, as expression of ASPP2κ is stress-inducible it defines a novel class of dynamic oncogenes not represented by genomic mutations.

Interpretation

Our data demonstrates that ASPP2κ plays a distinctive role as an antiapoptotic regulator of the TP53 checkpoint, rendering cells to a more aggressive phenotype as evidenced by proliferation and apoptosis rates – and ASPP2κ expression results in acquisition of genomic mutations, a first initiating step in leukemogenesis. We provide proof-of-concept to establish ASPP2κ as a clinically relevant biomarker and a target for molecule-defined therapy.

Fund

Unrestricted grant support from the Wilhelm Sander Foundation for Cancer Research, the IZKF Program of the Medical Faculty Tübingen, the Brigitte Schlieben-Lange Program and the Margarete von Wrangell Program of the State Ministry Baden-Wuerttemberg for Science, Research and Arts and the Athene Program of the excellence initiative of the Eberhard-Karls University, Tübingen.

Polymorphisms in MDM2 and TP53 Genes and Risk of Developing Therapy-Related Myeloid Neoplasms

One of the most severe complications after successful cancer therapy is the development of therapy-related myeloid neoplasms (t-MN). Constitutional genetic variation is likely to impact on t-MN risk. We aimed to evaluate if polymorphisms in the p53 pathway can be useful for predicting t-MN susceptibility. First, an association study revealed that the Pro variant of the TP53 Arg72Pro polymorphism and the G allele of the MDM2 SNP309 were associated with t-MN risk. The Arg variant of TP53 is more efficient at inducing apoptosis, whereas the Pro variant is a more potent inductor of cell cycle arrest and DNA repair. As regards MDM2 SNP309, the G allele is associated with attenuation of the p53 apoptotic response. Second, to evaluate the biological effect of the TP53 polymorphism, we established Jurkat isogenic cell lines expressing p53Arg or p53Pro. Jurkat p53Arg cells presented higher DNA damage and higher apoptotic potential than p53Pro cells, after treatment with chemotherapy agents. Only p53Pro cells presented t(15;17) translocation and del(5q). We suggest that failure to repair DNA lesions in p53Arg cells would lead them to apoptosis, whereas some p53Pro cells, prone to cell cycle arrest and DNA repair, could undergo misrepair, generating chromosomal abnormalities typical of t-MN.

TP53 gene rs1042522 allele G decreases neuroblastoma risk: a two-centre case-control study

The TP53 gene plays a crucial role in the prevention of cancer formation, which is closely related to TP53 mutation. TP53 gene polymorphism rs1042522 C>G was largely investigated in various cancers, but its contribution to neuroblastoma is as yet undefined. Here, we evaluated the effect of the TP53 gene rs1042522 C>G polymorphism on the development of neuroblastoma in two different regions, with patients from hospitals in both North and South China. The clinical data involved 374 patients and 812 controls. The resulting odds ratios (ORs) and 95% confidence intervals (CIs) were used with a logistic regression model to determine the intensity of associations between the factors of interest. We found that the TP53 gene rs1042522 allele G was associated with a reduced risk of developing neuroblastoma. In our stratified analysis of age, sex, primary sites and clinical stages, we observed that male children, older than 18 months, with tumours derived from the mediastinum who had the rs1042522 CG/GG genotypes were at a decreased risk of developing neuroblastoma. These results indicate that the TP53 gene rs1042522 allele G may be a potential protective factor against neuroblastoma in Chinese children.

Associations Between TP53 and MDM2 Polymorphisms and the Follicle-Stimulating Hormone/Luteinizing Hormone Ratio in Infertile Women

AIMS

This is a follow-up study based on the results of our previous article, to further explore the effect of the TP53 codon 72 (rs1042522) and MDM2 SNP309 (rs2279744) polymorphisms on basal follicle-stimulating hormone (FSH)/luteinizing hormone (LH) ratios in infertility women.

MATERIALS AND METHODS

The distribution of two genetic polymorphisms (rs1042522 and rs2279744) and basal FSH/LH ratios were tested and analyzed in 1051 in vitro fertilization (IVF) patients at a university-affiliated hospital.

RESULTS

The TP53 codon 72 polymorphism had a significant association with the FSH/LH ratio (group I: FSH/LH <2.3 and group II: FSH/LH ≥2.3) (C/C vs. G/G: odds ratio [OR] = 1.69, 95% confidence interval [CI]: 1.07-2.65, p = 0.02; G/C vs. G/G: OR = 1.86, 95% CI: 1.25-2.77, p = 0.002). In a stratification analysis, C allele carriers and the C/C genotype showed a strong association with positive clinical pregnancy outcomes after IVF compared with G allele carriers and the G/G genotype in the recessive, dominant, and allelic genetic models in group I (C/C vs. G/G: OR = 1.84, 95% CI: 1.25-2.69, p = 0.01; C/C vs. G carrier: OR = 1.52, 95% CI: 1.12-2.07, p = 0.01; C carrier vs. G/G: OR = 1.46, 95% CI: 1.07-2.01, p = 0.02; C allele vs. G allele: OR = 1.34, 95% CI: 1.11-1.62, p = 0.003), no significant associations by stratification were observed for group II. No associations were found between MDM2 SNP309 and either of two groups.

CONCLUSION

The TP53 codon 72 polymorphism is associated with FSH/LH ratios, suggesting that it is a potential predictive genetic marker of IVF outcome in patients younger than 35 years of age with baseline FSH levels below 10 IU/L and who have an FSH/LH ratio <2.3.

Impact of p53 arg72pro SNP on Breast Cancer Risk in North Indian Population

Background:

Genetic changes in p53 gene contribute to breast cancer susceptibility.

Objective and Methods:

A case-control study and a meta-analysis were performed to investigate the role of p53 codon72 SNP with breast cancer susceptibility in Indian women.

Results:

p53 heterozygous arginine variant was associated with decreased risk of breast cancer in total cohort. In meta-analysis, Allelic and GG vs. CC genetic comparison model were found to be associated with breast cancer risk. Moreover, recessive comparison model indicated a protective correlation with breast cancer occurrence.

Conclusion:

The findings of our case-control study and meta-analysis suggest a significant association between p53 Arg72Pro polymorphism and an increased risk of breast cancer in Indian population.

Immunogenetics of prostate cancer: a still unexplored field of study

The immune system is a double-edged sword with regard to the prostate cancer (PCa) battle. Immunogenetics, the study of the potential role of immune-related polymorphisms, is taking its first steps in the treatment of this malignancy. This review summarizes the most recent papers addressing the potential of immunogenetics in PCa, reporting immune-related polymorphisms associated with tumor aggressiveness, treatment toxicity and patients' prognosis. With some peculiarities, RNASEL, IL-6, IL-10, IL-1β and MMP7 have arisen as the most significant biomarkers in PCa treatment and management, having a potential clinical role. Validation prospective clinical studies are required to translate immunogenetics into precision treatment of PCa.

Sequence variation in PPP1R13L results in a novel form of cardio-cutaneous syndrome

Dilated cardiomyopathy (DCM) is a life-threatening disorder whose genetic basis is heterogeneous and mostly unknown. Five Arab Christian infants, aged 4-30 months from four families, were diagnosed with DCM associated with mild skin, teeth, and hair abnormalities. All passed away before age 3. A homozygous sequence variation creating a premature stop codon at PPP1R13L encoding the iASPP protein was identified in three infants and in the mother of the other two. Patients' fibroblasts and PPP1R13L-knocked down human fibroblasts presented higher expression levels of pro-inflammatory cytokine genes in response to lipopolysaccharide, as well as Ppp1r13l-knocked down murine cardiomyocytes and hearts of Ppp1r13l-deficient mice. The hypersensitivity to lipopolysaccharide was NF-κB-dependent, and its inducible binding activity to promoters of pro-inflammatory cytokine genes was elevated in patients' fibroblasts. RNA sequencing of Ppp1r13l-knocked down murine cardiomyocytes and of hearts derived from different stages of DCM development in Ppp1r13l-deficient mice revealed the crucial role of iASPP in dampening cardiac inflammatory response. Our results determined PPP1R13L as the gene underlying a novel autosomal-recessive cardio-cutaneous syndrome in humans and strongly suggest that the fatal DCM during infancy is a consequence of failure to regulate transcriptional pathways necessary for tuning cardiac threshold response to common inflammatory stressors.

Association between MDM2 SNP309, p53 Arg72Pro, and hepatocellular carcinoma risk: A MOOSE-compliant meta-analysis

Epidemiological studies have determined the associations between polymorphisms on the promoter of MDM2 (SNP309) and the codon 72 on exon 4 of p53 (p53 Arg72Pro) and the risk of hepatocellular carcinoma (HCC); however, the results were not always consistent. The aim of the present meta-analysis was to evaluate the overall associations between these 2 variants and HCC risk.The MEDLINE, Web of science, EMBASE, Cochrane Library, and CNKI databases were searched for eligibility studies and the data were synthesized under the fixed- or random-effects model. Heterogeneity among the studies was evaluated with the Cochrane test Q and I statistic.For MDM2 SNP309, the pooled odds ratio (OR) from 15 independent studies with a total of 4038 cases and 5491 controls suggested a significant association for the variant with HCC risk [allele model, G vs T: pooled OR = 1.48, 95% confidence interval (95% CI) = 1.26-1.73; pooled OR = 1.53, 95% CI = 1.26-1.81, for G/T vs T/T; pooled OR = 2.04, 95% CI = 1.54-2.71 for G/G vs T/T]. For p53 Arg72Pro, a total of 21 studies with 7285 cases and 9710 controls suggested that the variant was also associated with HCC risk under common genetic model (allele Pro vs Arg, pooled OR = 1.13, 95% CI = 1.02-1.25; Pro/Pro vs Arg/Arg, pooled OR = 1.32, 95% CI =1.06-1.64). No publication bias was found for all the meta-analysis as suggested by the Begg funnel plot and Egger tests.These results suggested that variants MDM2 SNP309 and p53 Arg72Pro are susceptibility factors for HCC; however, more studies are warranted to validate the results.

Dysfunction of the MDM2/p53 axis is linked to premature aging

The tumor suppressor p53, a master regulator of the cellular response to stress, is tightly regulated by the E3 ubiquitin ligase MDM2 via an autoregulatory feedback loop. In addition to its well-established role in tumorigenesis, p53 has also been associated with aging in mice. Several mouse models with aberrantly increased p53 activity display signs of premature aging. However, the relationship between dysfunction of the MDM2/p53 axis and human aging remains elusive. Here, we have identified an antiterminating homozygous germline mutation in MDM2 in a patient affected by a segmental progeroid syndrome. We show that this mutation abrogates MDM2 activity, thereby resulting in enhanced levels and stability of p53. Analysis of the patient's primary cells, genome-edited cells, and in vitro and in vivo analyses confirmed the MDM2 mutation's aberrant regulation of p53 activity. Functional data from a zebrafish model further demonstrated that mutant Mdm2 was unable to rescue a p53-induced apoptotic phenotype. Altogether, our findings indicate that mutant MDM2 is a likely driver of the observed segmental form of progeria.

Lack of evidence of HPV etiology of prostate cancer following radical surgery and higher frequency of the Arg/Pro genotype in Turkish men with prostate cancer

Objectives

The aim of this study was to assess the possible role of HPV in the development of prostate cancer (PCa) and investigate the distribution of the p53 codon 72 polymorphism in PCa in a Turkish population.

Materials and methods

A total of 96 tissues, which had been obtained using a radical surgery method, formalin-fixed and parafin-embedded, were used in this study. The study group consisted of 60 PCa tissues (open radical prostatectomy) and the control group contained 36 benign prostatic hyperplasia tissues (BPH) (transvesical open prostatectomy). The presence of HPV and the p53 codon 72 polymorphism was investigated in both groups using real-time PCR and pyrosequencing.

Results

The results of the real-time PCR showed no HPV DNA in any of the 36 BPH tissue samples. HPV-DNA was positive in only 1 of the 60 PCa samples (1.7%). The HPV type of this sample was identified as HPV-57. The distribution of the three genotypes, Arg/Arg, Arg/Pro and Pro/Pro was found to be 45.6, 45.6, and 8.8% in the PCa group and 57.1%, 34.3% and 8.6% in the control group, respectively. Compared with the control group, patients with PCa had a higher frequency of the Arg/Pro genotype and Proline allele (odds ratio (OR)=1.67, 95% confidence interval (CI)=0.68-4.09, p=0.044; OR=1.13, 95% CI=0.76-1.68, p=0.021, respectively).

Conclusions

The results of the study do not support the hyphothesis that prostate cancer is associated with HPV infection but indicated that Proline allele can be a risk factor in the development of PCa in the Turkish population.

The p53 R72P polymorphism does not affect the physiological response to ionizing radiation in a mouse model

Tissue culture and mouse model studies show that the presence of the arginine (R) or proline (P) coding single nucleotide polymorphism (SNP) of the tumor suppressor gene p53 at codon 72 (p53 R72P) differentially affects the responses to genotoxic insult. Compared to the P variant, the R variant shows increased apoptosis in most cell cultures and mouse model tissues in response to genotoxins, and epidemiological studies suggest that the R variant may enhance cancer survival and reduce the risks of adverse reactions to genotoxic cancer treatment. As ionizing radiation (IR) treatment is often used in cancer therapy, we sought to test the physiological effects of IR in mouse models of the p53 R72P polymorphism. By performing blood counts, immunohistochemical (IHC) staining and survival studies in mouse populations rigorously controlled for strain background, sex and age, we discovered that p53 R72P polymorphism did not differentially affect the physiological response to IR. Our findings suggest that genotyping for this polymorphism to personalize IR therapy may have little clinical utility.

Role of a p53 polymorphism in the development of nonfunctional pituitary adenomas

Non-functional pituitary adenomas (NFPAs) are among the commonest intracranial neoplasms. While histologically benign, NFPAs sometimes become large enough to limit therapeutic options and reduce quality of life. Investigations of the molecular etiology of NFPAs have failed to identify prevalent genetic changes and, while a role for p53 has been suggested, TP53 gene alterations have yet to be described in NFPAs. We found that the polymorphism rs1042522:C > G in codon 72 of exon 4 of the TP53 gene, whose C variant produces a proline and is more common in most ethnicities, has a G variant producing an arginine in 79.8% of NFPAs (n = 42; p < 1.411 × 10^-18 vs. 1000 Genomes database), causing patients to present a decade earlier with symptomatic NFPAs. In cultured NFPA cells, transfection with the rs1042522 G variant versus the C variant reduced expression of cell arrest gene p21 and increased proliferation. These findings suggest that this TP53 polymorphism influences NFPA growth.

Selective targeting p53WT lung cancer cells harboring homozygous p53 Arg72 by an inhibitor of CypA

TP53 plays essential roles in tumor initiation and progression, and is frequently mutated in cancer. However, pharmacological stabilization and reactivation of p53 have not been actively explored for targeted cancer therapies. Herein, we identify a novel Cyclophilin A (CypA) small molecule inhibitor (HL001) that induces non-small cell lung cancer (NSCLC) cell cycle arrest and apoptosis via restoring p53 expression. We find that HL001 stabilizes p53 through inhibiting the MDM2-mediated p53 ubiquitination. Further mechanistic studies reveal that the downregulation of G3BP1 and the induction of reactive oxygen species and DNA damage by HL001 contribute to p53 stabilization. Surprisingly, HL001 selectively suppresses tumor growth in p53 wild-type NSCLC harboring Arg72 homozygous alleles (p53-72R) through disrupting interaction between MDM2 and p53-72R in a CypA-dependent manner. Moreover, combining HL001 with cisplatin synergistically enhance tumor regression in orthotopic NSCLC mouse model. Collectively, this study demonstrates that pharmacologic inhibition of CypA offers a potential therapeutic strategy via specific activation of p53-72R in NSCLC.

ΔN-ASPP2, a novel isoform of the ASPP2 tumor suppressor, promotes cellular survival

ASPP2 is a tumor suppressor that works, at least in part, through enhancing p53-dependent apoptosis. We now describe a new ASPP2 isoform, ΔN-ASPP2, generated from an internal transcription start site that encodes an N-terminally truncated protein missing a predicted 254 amino acids. ΔN-ASPP2 suppresses p53 target gene transactivation, promoter occupancy, and endogenous p53 target gene expression in response to DNA damage. Moreover, ΔN-ASPP2 promotes progression through the cell cycle, as well as resistance to genotoxic stress-induced growth inhibition and apoptosis. Additionally, we found that ΔN-ASPP2 expression is increased in human breast tumors as compared to adjacent normal breast tissue; in contrast, ASPP2 is suppressed in the majority of these breast tumors. Together, our results provide insight into how this new ASPP2 isoform may play a role in regulating the ASPP2-p53 axis.

The IGF-1R/AKT pathway determines cell fate in response to p53

p53 that is activated in response to DNA-damaging stress can induce apoptosis or either transient or permanent cell cycle arrests. Apoptosis and permanent cell cycle arrest (senescence) are bona-fide tumor suppressor mechanisms through which p53 inhibits cancer cell survival. In contrast, transient cell cycle arrests induced by p53 can increase survival by allowing cells time to repair their DNA before proceeding with cell division. Mechanisms that control the choice of response to p53 (apoptosis vs arrest) are not fully understood. There is abundant crosstalk between p53 and the IGF-1R/AKT/mTORC1 signaling pathway. Recent studies indicate this crosstalk can determine the choice of response to p53. These findings have clear implications for the potential use of IGF-1R pathway inhibitors against p53 wild-type or p53-null or mutant cancers.

Intra molecular interactions in the regulation of p53 pathway

The p53 tumor suppressor is highly regulated at the level of protein degradation and transcriptional activity. The key players of the pathway, p53, MDM2, and MDMX are present at multiple conformational states that are responsive to regulation by post-translational modifications and protein-protein interactions. The structures of major functional domains of these proteins have been determined, but the mechanisms of several intrinsically disordered regions remain unclear despite their critical roles in signaling and regulation. Recent studies suggest that these disordered regions function in part by dynamic intra molecular interactions with the structured domains to regulate p53 DNA binding, MDM2 ubiquitin E3 ligase activity, and MDMX-p53 binding. These findings provide new insight on how p53 is controlled by various stress signals, and suggest potential targets for the search of allosteric regulators of the p53 pathway.

TP53 codon 72 polymorphism and breast cancer risk in Bangladeshi population

BACKGROUND

Breast cancer, a hereditary or heterogeneous sporadic disease, is the most common cancer in women worldwide. The tumor suppressor TP53 gene has been found to be the most commonly mutated genes in many types of human cancers, including breast cancer. This study aimed to investigate the association of codon 72 polymorphism of TP53 gene with breast cancer risk in Bangladeshi females.

METHODS

The study included 125 cases and 125 healthy controls. Genotyping and polymorphism were determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis.

RESULTS

The frequencies of the three genotypes Arg/Arg, Arg/Pro, and Pro/Pro were 43.2, 33.6, and 23.2% in cases, whereas 48.8, 40.8, and 10.4% in controls, respectively. The frequency of mutant homozygous (Pro/Pro) genotype was significantly increased in breast cancer patients as compared with controls (23.2 vs 10.4%), and showed 2.52-fold significantly increased risk for breast cancer (OR 2.5199, 95% CI 1.19-5.33, p = 0.0157). The frequencies of Pro/Pro genotype were significantly higher in breast cancer cases with non-breast feeding status. Pro allele frequency was found to be significantly increased in breast cancer cases (OR 1.4978, 95% CI 1.0357-2.1662, p = 0.0318).

CONCLUSIONS

Our data suggest that mutant (Pro/Pro) homozygosity at codon 72 of TP53 gene is significantly associated with breast cancer susceptibility in Bangladeshi women. In addition, this association was significantly related to lactating status.

A novel TP53 variant (rs78378222 A > C) in the polyadenylation signal is associated with increased cancer susceptibility: evidence from a meta-analysis

Polymorphisms in TP53 are involved in the progression of different types of cancer. A rare novel TP53 variant (rs78378222 A > C allele) was found via whole-genome sequencing in 2011. This variant was shown to significantly increase the risk of glioma, colorectal adenoma and prostate cancer. Functional analysis further revealed that this variant hindered TP53 expression and its downstream effect on apoptosis. Several studies have investigated the relationship between rs78378222 and cancer susceptibility. However, the results were not consistent. We conducted the first meta-analysis to give a more credible assessment on the association about this variant and cancer risk. Our meta-analysis included 34 studies consisting of 36599 cases and 91272 controls. These studies were mostly on the basis of high-grade data from Genome-wide association studies (GWASs). The results indicated that TP53 rs78378222 was significantly associated with an increased risk of overall cancer (AC vs. AA: OR = 1.511, 95% CI = 1.285-1.777). Furthermore, stratified analyses indicated that rs78378222 increased the risk of nervous system cancer, skin cancer and other cancer. To summarize, this meta-analysis suggested that rs78378222 C allele is a potent risk factor for overall cancer.

Lysines in the tetramerization domain of p53 selectively modulate G1 arrest

Functional in a tetrameric state, the protein product of the p53 tumor suppressor gene confers its tumor-suppressive activity by transactivating genes which promote cell-cycle arrest, senescence, or programmed cell death. How p53 distinguishes between these divergent outcomes is still a matter of considerable interest. Here we discuss the impact of 2 mutations in the tetramerization domain that confer unique properties onto p53. By changing lysines 351 and 357 to arginine, thereby blocking all post-translational modifications of these residues, DNA binding and transcriptional regulation by p53 remain virtually unchanged. On the other hand, by changing these lysines to glutamine (2KQ-p53), thereby neutralizing their positive charge and potentially mimicking acetylation, p53 is impaired in the induction of cell cycle arrest and yet can still effectively induce cell death. Surprisingly, when 2KQ-p53 is expressed at high levels in H1299 cells, it can bind to and transactivate numerous p53 target genes including p21, but not others such as miR-34a and cyclin G1 to the same extent as wild-type p53. Our findings show that strong induction of p21 is not sufficient to block H1299 cells in G1, and imply that modification of one or both of the lysines within the tetramerization domain may serve as a mechanism to shunt p53 from inducing cell cycle arrest.

A novel all-trans retinoic acid derivative 4-amino‑2‑trifluoromethyl-phenyl retinate inhibits the proliferation of human hepatocellular carcinoma HepG2 cells by inducing G0/G1 cell cycle arrest and apoptosis via upregulation of p53 and ASPP1 and downregulation of iASPP

4-Amino-2-trifluoromethyl-phenyl retinate (ATPR), a novel all-trans retinoic acid (ATRA) derivative, was reported to function as a tumor inhibitor in various types of cancer cells in vitro. However, little is known concerning its antitumor effect on human hepatocellular carcinoma (HCC) HepG2 cells. The aims of the present study were to investigate the effects of ATPR on the proliferation of HepG2 cells and to explore the probable mechanisms. A series of experiments were performed following the treatment of HepG2 cells with ATRA and ATPR. MTT and plate colony formation assays were used to measure the cell viability. To confirm the influence on proliferation, flow cytometry was used to detect the distribution of the cell cycle. Apoptosis was observed by Hoechst staining and flow cytometry. In addition, to characterize the underlying molecular mechanisms, immunofluorescence was applied to observe the distribution of p53. The transcription and translation levels of p53 were analyzed by real-time quantitative RT-PCR (qRT-PCR) and western blotting. The expression levels of murine double minute 2 (MDM2), apoptosis stimulating proteins of p53 (ASPP), cell cycle- and apoptosis-associated proteins were detected by western blotting. After HepG2 cells were incubated with ATRA and ATPR, the viability of the HepG2 cells was inhibited in a dose- and time-dependent manner. As well, ATPR significantly suppressed HepG2 cell colony formation and arrested cells at the G0/G1 phase, while ATRA had no obvious effects. Both Hoechst staining and flow cytometry unveiled the apoptosis of HepG2 cells. Moreover, the fluorescent density of p53 was higher in the nuclei after exposure to ATPR than that in the ATRA group. HepG2 cells treated with ATPR showed elevated mRNA and protein levels of p53 when compared with these levels in the ATRA-treated cells. Western blotting showed that ATPR increased ASPP1, p21 and Bax expression and decreased MDM2, iASPP, cyclin D and E, cyclin-dependent kinase 6 (CDK6) and Bcl-2 expression, while CDK4 and ASPP2 expression were scarcely altered. Consequently, ATPR exerted a better inhibitory effect on the proliferation of HepG2 cells than ATRA through increased expression of p53 and ASPP1 and downregulation of iASPP, thereby resulting in G0/G1 cell cycle arrest and apoptosis.