Transcriptional regulation of thymine DNA glycosylase (TDG) by the tumor suppressor protein p53

TAMing immunity through an unexpected source

Arginine availability and metabolism critically shape tumor-immune interactions. In this issue of Cancer Cell, Zhu et al. demonstrate that breast cancer-cell-derived arginine synthesized via ASS1 fuels macrophage polyamine synthesis, reinforcing immunosuppressive tumor-associated macrophages (TAMs). Mechanistically, this occurs through TDG/p53-dependent DNA demethylation and activation of PPARG.

Cancer cell-derived arginine fuels polyamine biosynthesis in tumor-associated macrophages to promote immune evasion

Arginine metabolism reshapes the tumor microenvironment (TME) into a pro-tumor niche through complex metabolic cross-feeding among various cell types. However, the key intercellular metabolic communication that mediates the collective effects of arginine metabolism within the TME remains unclear. Here, we reveal that the metabolic interplay between cancer cells and macrophages plays a dominant role in arginine-driven breast cancer progression. Within the TME, breast cancer cells serve as the primary source of arginine, which induces a pro-tumor polarization of tumor-associated macrophages (TAMs), thereby suppressing the anti-tumor activity of CD8+ T cells. Notably, this cancer cell-macrophage interaction overrides the arginine-mediated enhancement of CD8+ T cell anti-tumor activity. Mechanistically, polyamines derived from arginine metabolism enhance pro-tumor TAM polarization via thymine DNA glycosylase (TDG)-mediated DNA demethylation, regulated by p53 signaling. Importantly, targeting the arginine-polyamine-TDG axis between cancer cells and macrophages significantly suppresses breast cancer growth, highlighting its therapeutic potential.

The level of active DNA demethylation compounds in leukocytes and urine samples as potential epigenetic biomarkers in breast cancer patients

The active DNA demethylation process, which involves TET proteins, can affect DNA methylation pattern. TET dependent demethylation results in DNA hypomethylation by oxidation 5-methylcytosine (5-mC) to 5-hydroxymethylcytosine (5-hmC) and its derivatives. Moreover, TETs' activity may be upregulated by ascorbate. Given that aberrant DNA methylation of genes implicated in breast carcinogenesis may be involved in tumor progression, we wanted to determine whether breast cancer patients exert changes in the active DNA demethylation process. The study included blood samples from breast cancer patients (n = 74) and healthy subjects (n = 71). We analyzed the expression of genes involved in the active demethylation process (qRT-PCR), and 5-mC and its derivatives level (2D-UPLC MS/MS). The ascorbate level was determined using UPLC-MS. Breast cancer patients had significantly higher TET3 expression level, lower 5-mC and 5-hmC DNA levels. TET3 was significantly increased in luminal B breast cancer patients with expression of hormone receptors. Moreover, the ascorbate level in the plasma of breast cancer patients was decreased with the accompanying increase of sodium-dependent vitamin C transporters (SLC23A1 and SLC23A2). The presented study indicates the role of TET3 in DNA demethylation in breast carcinogenesis.

Comprehensive analysis of the prognostic value and biological function of TDG in hepatocellular carcinoma

Epigenetics plays an important role in the malignant progression of tumors, in which DNA methylation can alter genetic performance without altering the DNA sequence. As a key regulator demethylation, thymine-DNA glycosylase (TDG) has been reported to participate in malignant progression of multiple tumors. In this study, we demonstrate that TDG is highly expressed in hepatocellular carcinoma (HCC) and its high expression is closely related to the poor prognosis of patients. Decreasing TDG expression can significantly inhibit the malignant biological behavior of HCC cells. ABL proto-oncogene 1(ABL1) was identified as a downstream gene regulated by TDG demethylation. In addition, TDG can affect the Hippo signaling pathway through ABL1 to regulate HCC cell proliferation, apoptosis, invasion and migration. Overall, our study demonstrated that TDG reduces DNA methylation of ABL1, increases ABL1 protein expression, and affects the Hippo signaling pathway to regulate the malignant progression of HCC.

Study on the Effects of Melatonin on Cisplatin-Induced Apoptosis of Renal Tubular Epithelial Cells and Autophagy Protein L Light Chain 3 (LC3)

Purpose: The aim of this work was to discuss Melatonin’s effects on Cisplatin-induced Apoptosis of Renal Tubular Epithelial Cells. Materials and Methods: Blood and renal tissue were collected, The level of serum creatinine (Scr) was detected, the content of p53 protein in renal tissue was detected by immunohistochemistry, the expression of p53 protein and autophagy marker protein microtubule associated protein L light chain 3II (LC3II)/LC 3I ratio in renal tissue was detected by WB method, the apoptosis of renal tubular epithelial cells was detected by TUNEL method, and the morphological changes of renal tissue were observed by light microscope. Results: Scr level and apoptosis cell rate were significantly increased in Model group (P < 0.001), P53 and LC 3II/LC 3I ratio were significantly depressed (P < 0.001). With MT supplement, Scr level and apoptosis cell rate were significantly depressed (P < 0.05); MT could significantly up-regulate P53 and LC 3II/LC 3I ratio (P < 0.05), MT could improve the pathological changes such as renal tubular epithelial cell fusion and vacuolar degeneration, and reduce renal tubular injury. Conclusion: MT has a protective effect on cisplatin induced AKI in mice. Its mechanism may be related to up regulating the expression levels of p53 protein and LC 3II/LC 3I ratio.

Retracted Article: Divergent synthesis of 5-substituted pyrimidine 2'-deoxynucleosides and their incorporation into oligodeoxynucleotides for the survey of uracil DNA glycosylases

Recent studies have indicated that 5-methylcytosine (5mC) residues in DNA can be oxidized and potentially deaminated to the corresponding thymine analogs. Some of these oxidative DNA damages have been implicated as new epigenetic markers that could have profound influences on chromatin function as well as disease pathology. In response to oxidative damage, the cells have a complex network of repair systems that recognize, remove and rebuild the lesions. However, how the modified nucleobases are detected and repaired remains elusive, largely due to the limited availability of synthetic oligodeoxynucleotides (ODNs) containing these novel DNA modifications. A concise and divergent synthetic strategy to 5mC derivatives has been developed. These derivatives were further elaborated to the corresponding phosphoramidites to enable the site-specific incorporation of modified nucleobases into ODNs using standard solid-phase DNA synthesis. The synthetic methodology, along with the panel of ODNs, is of great value to investigate the biological functions of epigenetically important nucleobases, and to elucidate the diversity in chemical lesion repair.

Thymine DNA glycosylase-regulated TAZ promotes radioresistance by targeting nonhomologous end joining and tumor progression in esophageal cancer

Radiation resistance is a major cause of esophageal cancer relapse or metastasis. Transcriptional coactivator with PDZ binding domain (TAZ) is a final effector of the Hippo signaling pathway and plays critical roles in several types of cancer, but how it participates in the progression and radiation resistance of esophageal cancer remains unclear. Here, we revealed that TAZ was the strongest prognostic factor among Hippo pathway members. Overexpression of TAZ predicted poor outcome and adverse pathological features. In cell and animal models, TAZ facilitated cell proliferation, motility, and radiation resistance. Additionally, TAZ promoted expression of nonhomologous end joining (NHEJ)‐related genes, which are the main contributors to repair irradiation‐induced DNA breaks and result in radiation resistance. Amplification of the TAZ gene occurred in 2.5%‐3.2% of esophageal cancers. In addition, the CpG islands of the TAZ gene were demethylated in esophageal cancer under thymine DNA glycosylase (TDG) regulation. Knockdown of TDG inhibited cell growth, motility, and radiation resistance, which were overridden by TAZ overexpression. Collectively, these findings suggest that the TDG/TAZ/NHEJ axis is a critical player in esophageal cancer progression and radiation resistance, as well as a potential target for radiotherapy.

From cancer to rejuvenation: incomplete regeneration as the missing link (Part I: the same origin, different outcomes)

Here, we interpret malignant tissue transformation from the aging point of view, that is, as a result of insufficient cell adaptation to the needs of regeneration/repair and proliferation. A consequence of the aging (senescence) process is gradual loss of self-renewal potential. It limits lifespan and leads to death due to the decline of tissue/organ functions, failure of regulatory mechanisms, disruption of endogenous processes and increased susceptibility to exogenous factors. Recapitulation of the embryonic pathway of self-renewal/rejuvenation in adulthood is epigenetically determined. At the postembryonic stage, in the absence of immune privilege, this recapitulation is transformed into cancer (potency expansion of single structures composing the organism to the detriment of the whole organism or disintegrating growth). We suggest that the process of rebirth occurs in the same way as embryonic tissue growth. Thus, the idea to use the potential of the transformed cells to stop the aging process has been proposed.

Additional functions of selected proteins involved in DNA repair

Protein moonlighting is a phenomenon in which a single polypeptide chain can perform a number of different unrelated functions. Here we present our analysis of moonlighting in the case of selected DNA repair proteins which include G:T mismatch-specific thymine DNA glycosylase (TDG), methyl-CpG-binding domain protein 4 (MBD4), apurinic/apyrimidinic endonuclease 1 (APE1), AlkB homologs, poly (ADP-ribose) polymerase 1 (PARP-1) and single-strand selective monofunctional uracil DNA glycosylase 1 (SMUG1). Most of their additional functions are not accidental and clear patterns are emerging. Participation in RNA metabolism is not surprising as bases occurring in RNA are the same or very similar to those in DNA. Other common additional function involves regulation of transcription. This is not unexpected as these proteins bind to specific DNA regions for DNA repair, hence they can also be recruited to regulate transcription. Participation in demethylation and replication of DNA appears logical as well. Some of the multifunctional DNA repair proteins play major roles in many diseases, including cancer. However, their moonlighting might prove a major difficulty in the development of new therapies because it will not be trivial to target a single protein function without affecting its other functions that are not related to the disease.

TDG Gene Polymorphisms and Their Possible Association with Colorectal Cancer: A Case Control Study

Genetic alterations that might lead to colorectal cancer involve essential genes including those involved in DNA repair, inclusive of base excision repair (BER). Thymine DNA glycosylase (TDG) is one of the most well characterized BER genes that catalyzes the removal of thymine moieties from G/T mismatches and is also involved in many cellular functions, such as the regulation of gene expression, transcriptional coactivation, and the control of epigenetic DNA modification. Mutation of the TDG gene is implicated in carcinogenesis. In the present study, we aimed to investigate the association between TDG gene polymorphisms and their involvement in colon cancer susceptibility. One hundred blood samples were obtained from colorectal cancer patients and healthy controls for the genotyping of seven SNPs in the TDG gene. DNA was extracted from the blood, and the polymorphic sites (SNPs) rs4135113, rs4135050, rs4135066, rs3751209, rs1866074, and rs1882018 were investigated using TaqMan genotyping. One of the six TDG SNPs was associated with an increased risk of colon cancer. The AA genotype of the TDG SNP rs4135113 increased the risk of colon cancer development by more than 3.6-fold, whereas the minor allele A increased the risk by 1.6-fold. It also showed a 5-fold higher risk in patients over the age of 57. SNP rs1866074 showed a significant protective association in CRC patients. The GA genotype of TDG rs3751209 was associated with a decreased risk in males. There is a significant relationship between TDG gene function and colorectal cancer progression.

Cytotoxic and toxicogenomic effects of silibinin in bladder cancer cells with different TP53 status

Silibinin is a natural phenol found in the seeds of the milk thistle plant. Recent data have shown its effectiveness for preventing/treating bladder tumours. Therefore, in this study we investigated the cytotoxic and toxicogenetic activity of silibinin in bladder cancer cells with different TP53 statuses. Two bladder urothelial carcinoma cell lines were used: RT4 (wild-type TP53 gene) and T24 (mutated TP53 gene). Cell proliferation, clonogenic survival, apoptosis rates, genotoxicity and relative expression profile of FRAP/mTOR, FGFR3, AKT2 and DNMT1 genes and of miR100 and miR203 were evaluated. Silibinin promoted decreased proliferation and increased late apoptosis in TP53 mutated cells. Increased early apoptosis rates, primary DNA damage, and decrease of cell colonies in the clonogenic survival assay were detected in both RT4 and T24 cell lines. Down-regulation of FRAP/mTOR, AKT2, FGFR3, DNMT1 and miR100 expression occurred in RT4 cells. Modulation of miR203 was observed in both cell lines. In conclusion, despite the reduction of clone formation in both cell lines, the toxicogenomic effect of silibinin on FRAP/mTOR, AKT2, FGFR3, DNMT1 and miR100 was dependent on the TP53 status. Taken together, the data confirmed the role of silibinin as an antiproliferative compound, whose mechanism of action was related to the TP53 status.

Oncogenic Ras suppresses ING4-TDG-Fas axis to promote apoptosis resistance

Ras is aberrantly activated in many cancers and active DNA demethylation plays a fundamental role to establish DNA methylation pattern which is of importance to cancer development. However, it was unknown whether and how Ras regulate DNA demethylation during carcinogenesis. Here we found that Ras downregulated thymine-DNA glycosylase (TDG), a DNA demethylation enzyme, by inhibiting the interaction of transcription activator ING4 with TDG promoter. TDG recruited histone lysine demethylase JMJD3 to the Fas promoter and activated its expression, thus restoring sensitivity to apoptosis. TDG suppressed in vivo tumorigenicity of xenograft pancreatic cancer. Thus, we speculate that reversing Ras-mediated ING4 inhibition to activate Fas expression is a potential therapeutic approach for Ras-driven cancers.

Multifaceted roles for thymine DNA glycosylase in embryonic development and human carcinogenesis

Thymine DNA glycosylase (TDG) is a multifunctional protein that plays important roles in DNA repair, DNA demethylation, and transcriptional regulation. These diverse functions make TDG a unique enzyme in embryonic development and carcinogenesis. This review discusses the molecular function of TDG in human cancers and the previously unrecognized value of TDG as a potential target for drug therapy.

Robust quantitative assessments of cytosine modifications and changes in the expressions of related enzymes in gastric cancer

BACKGROUND

The rediscovery of 5-hydroxymethylcytosine, the ten-eleven translocation (TET) family, thymine-DNA glycosylase (TDG) and isocitrate dehydrogenase (IDH) have opened new avenues in the study of DNA demethylation pathways in gastric cancer (GC). We performed a comprehensive and robust analysis of these genes and modified cytosines in gastric cancer.

METHODS

Liquid chromatography mass spectrometry/mass spectrometry (LC-MS/MS) was used to assess 5-methyldeoxycytidine (5-mC), 5-hydroxymethyldeoxycytidine (5-hmC), 5-formyldeoxycytidine (5-fC) and 5-carboxyldeoxycytidine (5-caC) quantitatively in tumorous and non-tumorous regions of GCs; [D2]-5-hmC was used as an internal standard. Expression levels of the genes TET1, TET2, TET3, TDG, IDH1 and IDH2 were measured using a real-time reverse transcription polymerase chain reaction (RT-PCR) and were compared to the clinical attributes of each case. Using HEK293T cells the effects of introducing plasmids containing full-length TET1, TET2, and TET3 and 7 variants of the TET2 catalytic domain were evaluated in terms of their effect on cytosine demethylation.

RESULTS

LC-MS/MS showed that 5-hmC was significantly decreased in tumorous portions. 5-mC was also moderately decreased in tumors, while 5-fC and 5-caC were barely detectable. The expressions of TET1, TET2, TET3, TDG and IDH2, but not IDH1, were notably decreased in GCs, compared with the adjacent non-tumor portion. TET1 expression and the 5-hmC levels determined using LC-MS/MS had a significantly positive correlation and TET1 protein had a greater effect on the increase in 5-hmC than TET2 and TET3 in HEK293T cells.

CONCLUSIONS

The loss of 5-hmC and the down-regulation of TET1-3, TDG and IDH2 were found in GCs. The loss of 5-hmC in GCs was mainly correlated with the down-regulation of TET1.

miR-29b is an indicator of prognosis in breast cancer patients

MicroRNA-29b (miR-29b) targets numerous important genes that mediate carcinogenesis and tumor development in breast cancer in vitro and in vivo. The aim of the present study was to determine the clinical significance of miR-29b expression in primary breast cancer patients. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) of miR-29b and certain target genes of miR-29b, such as DNA methyltransferase 3A (DNMT3A), ten-eleven translocation 1 (TET1) and thymine DNA glycosylase (TDG), was performed in 94 primary breast cancer samples. Low expression of miR-29b in primary tumors was significantly associated with poorer disease-free survival (DFS) (P=0.0075) and overall survival (OS) (p=0.0012). Multivariate analysis indicated that miR-29b expression was an independent prognostic factor for OS [relative risk=15.6 (2.33-348), P=0.0026]. In addition, a significant inverse correlation was identified between the expression levels of DNMT3A and miR-29b in estrogen receptor-positive breast cancer patients (P=0.027). To the best of our knowledge, this is the first study to investigate the clinicopathological significance of miR-29b in breast cancer cases and miR-29b is shown to act as a tumor suppressive microRNA in breast cancer and as a potential marker for recurrence and metastasis in breast cancer patients.

DNA methylation patterns of candidate genes regulated by thymine DNA glycosylase in patients with TP53 germline mutations

Li-Fraumeni syndrome (LFS) is a rare, autosomal dominant, hereditary cancer predisposition disorder. In Brazil, the p.R337H TP53 founder mutation causes the variant form of LFS, Li-Fraumeni-like syndrome. The occurrence of cancer and age of disease onset are known to vary, even in patients carrying the same mutation, and several mechanisms such as genetic and epigenetic alterations may be involved in this variability. However, the extent of involvement of such events has not been clarified. It is well established that p53 regulates several pathways, including the thymine DNA glycosylase (TDG) pathway, which regulates the DNA methylation of several genes. This study aimed to identify the DNA methylation pattern of genes potentially related to the TDG pathway (CDKN2A, FOXA1, HOXD8, OCT4, SOX2, and SOX17) in 30 patients with germline TP53 mutations, 10 patients with wild-type TP53, and 10 healthy individuals. We also evaluated TDG expression in patients with adrenocortical tumors (ADR) with and without the p.R337H TP53 mutation. Gene methylation patterns of peripheral blood DNA samples assessed by pyrosequencing revealed no significant differences between the three groups. However, increased TDG expression was observed by quantitative reverse transcription PCR in p.R337H carriers with ADR. Considering the rarity of this phenotype and the relevance of these findings, further studies using a larger sample set are necessary to confirm our results.

The role of DNA damage responses in p53 biology

The tumour suppressor p53 is a central player in cellular DNA damage responses. P53 is upregulated and activated by genotoxic stress and induces a transcriptional programme with effectors promoting apoptosis, cell cycle arrest, senescence and DNA repair. For the best part of the last three decades, these DNA damage-related programmes triggered by p53 were unequivocally regarded as the major if not sole mechanism by which p53 exerts its tumour suppressor function. However, this interpretation has been challenged by a number of recent in vivo studies, demonstrating that mice which are defective in inducing p53-dependent apoptosis, cell cycle arrest and senescence suppress thymic lymphoma as well as wild-type p53 expressing animals. Consequently, the importance of DNA damage responses for p53-mediated tumour suppression has been questioned. In this review, I summarize current knowledge on p53-controlled DNA damage responses and argue that these activities, while their role has certainly changed, remain an important feature of p53 biology with relevance for cancer therapy and tumour suppression.

Thymine DNA glycosylase is a positive regulator of Wnt signaling in colorectal cancer

Wnt signaling plays an important role in colorectal cancer (CRC). Although the mechanisms of β-catenin degradation have been well studied, the mechanism by which β-catenin activates transcription is still not fully understood. While screening a panel of DNA demethylases, we found that thymine DNA glycosylase (TDG) up-regulated Wnt signaling. TDG interacts with the transcription factor TCF4 and coactivator CREB-binding protein/p300 in the Wnt pathway. Knocking down TDG by shRNAs inhibited the proliferation of CRC cells in vitro and in vivo. In CRC patients, TDG levels were significantly higher in tumor tissues than in the adjacent normal tissues. These results suggest that TDG warrants consideration as a potential biomarker for CRC and as a target for CRC treatment.

Molecular changes during neurodevelopment following second-trimester binge ethanol exposure in a mouse model of fetal alcohol spectrum disorder: from immediate effects to long-term adaptation

Fetal alcohol spectrum disorder (FASD) is an umbrella term that refers to a wide range of behavioral and cognitive deficits resulting from prenatal alcohol exposure. It involves changes in brain gene expression that underlie lifelong FASD symptoms. How these changes are achieved from immediate to long-term effects, and how they are maintained, is unknown. We have used the C57BL/6J mouse to assess the dynamics of genomic alterations following binge alcohol exposure. Ethanol-exposed fetal (short-term effect) and adult (long-term effect) brains were assessed for gene expression and microRNA (miRNA) changes using Affymetrix mouse arrays. We identified 48 and 68 differentially expressed genes in short- and long-term groups, respectively. No gene was common between the 2 groups. Short-term (immediate) genes were involved in cellular compromise and apoptosis, which represent ethanol's toxic effects. Long-term genes were involved in various cellular functions, including epigenetics. Using quantitative RT-PCR, we confirmed the downregulation of long-term genes: Camk1g, Ccdc6, Egr3, Hspa5, and Xbp1. miRNA arrays identified 20 differentially expressed miRNAs, one of which (miR-302c) was confirmed. miR-302c was involved in an inverse relationship with Ccdc6. A network-based model involving altered genes illustrates the importance of cellular redox, stress and inflammation in FASD. Our results also support a critical role of apoptosis in FASD, and the potential involvement of miRNAs in the adaptation of gene expression following prenatal ethanol exposure. The ultimate molecular footprint involves inflammatory disease, neurological disease and skeletal and muscular disorders as major alterations in FASD. At the cellular level, these processes represent abnormalities in redox, stress and inflammation, with potential underpinnings to anxiety.

The role of inflammation in brain cancer

Malignant brain tumors are among the most lethal of human tumors, with limited treatment options currently available. A complex array of recurrent genetic and epigenetic changes has been observed in gliomas that collectively result in derangements of common cell signaling pathways controlling cell survival, proliferation, and invasion. One important determinant of gene expression is DNA methylation status, and emerging studies have revealed the importance of a recently identified demethylation pathway involving 5-hydroxymethylcytosine (5hmC). Diminished levels of the modified base 5hmC is a uniform finding in glioma cell lines and patient samples, suggesting a common defect in epigenetic reprogramming. Within the tumor microenvironment, infiltrating immune cells increase oxidative DNA damage, likely promoting both genetic and epigenetic changes that occur during glioma evolution. In this environment, glioma cells are selected that utilize multiple metabolic changes, including changes in the metabolism of the amino acids glutamate, tryptophan, and arginine. Whereas altered metabolism can promote the destruction of normal tissues, glioma cells exploit these changes to promote tumor cell survival and to suppress adaptive immune responses. Further understanding of these metabolic changes could reveal new strategies that would selectively disadvantage tumor cells and redirect host antitumor responses toward eradication of these lethal tumors.

The transcription factor p53: not a repressor, solely an activator

The predominant function of the tumor suppressor p53 is transcriptional regulation. It is generally accepted that p53-dependent transcriptional activation occurs by binding to a specific recognition site in promoters of target genes. Additionally, several models for p53-dependent transcriptional repression have been postulated. Here, we evaluate these models based on a computational meta-analysis of genome-wide data. Surprisingly, several major models of p53-dependent gene regulation are implausible. Meta-analysis of large-scale data is unable to confirm reports on directly repressed p53 target genes and falsifies models of direct repression. This notion is supported by experimental re-analysis of representative genes reported as directly repressed by p53. Therefore, p53 is not a direct repressor of transcription, but solely activates its target genes. Moreover, models based on interference of p53 with activating transcription factors as well as models based on the function of ncRNAs are also not supported by the meta-analysis. As an alternative to models of direct repression, the meta-analysis leads to the conclusion that p53 represses transcription indirectly by activation of the p53-p21-DREAM/RB pathway.

Single-strand selective monofunctional uracil-DNA glycosylase (SMUG1) deficiency is linked to aggressive breast cancer and predicts response to adjuvant therapy

Uracil in DNA is an important cause of mutagenesis. SMUG1 is a uracil-DNA glycosylase that removes uracil through base excision repair. SMUG1 also processes radiation-induced oxidative base damage as well as 5-fluorouracil incorporated into DNA during chemotherapy. We investigated SMUG1 mRNA expression in 249 primary breast cancers. SMUG1 protein expression was investigated in 1,165 breast tumours randomised into two cohorts [training set (n = 583) and test set (n = 582)]. SMUG1 and chemotherapy response was also investigated in a series of 315 ER-negative tumours (n = 315). For mechanistic insights, SMUG1 was correlated to biomarkers of aggressive phenotype, DNA repair, cell cycle and apoptosis. Low SMUG1 mRNA expression was associated with adverse disease specific survival (p = 0.008) and disease-free survival (p = 0.008). Low SMUG1 protein expression (25 %) was associated with high histological grade (p < 0.0001), high mitotic index (p < 0.0001), pleomorphism (p < 0.0001), glandular de-differentiation (p = 0.0001), absence of hormonal receptors (ER-/PgR-/AR) (p < 0.0001), presence of basal-like (p < 0.0001) and triple-negative phenotypes (p < 0.0001). Low SMUG1 protein expression was associated with loss of BRCA1 (p < 0.0001), ATM (p < 0.0001) and XRCC1 (p < 0.0001). Low p27 (p < 0.0001), low p21 (p = 0.023), mutant p53 (p = 0.037), low MDM2 (p < 0.0001), low MDM4 (p = 0.004), low Bcl-2 (p = 0.001), low Bax (p = 0.003) and high MIB1 (p < 0.0001) were likely in low SMUG1 tumours. Low SMUG1 protein expression was associated with poor prognosis in univariate (p < 0.001) and multivariate analysis (p < 0.01). In ER+ cohort that received adjuvant endocrine therapy, low SMUG1 protein expression remains associated with poor survival (p < 0.01). In ER- cohort that received adjuvant chemotherapy, low SMUG1 protein expression is associated with improved survival (p = 0.043). Our study suggests that low SMUG1 expression may correlate to adverse clinicopathological features and predict response to adjuvant therapy in breast cancer.

Molecular dynamics of the full-length p53 monomer

The p53 protein is frequently mutated in a very large proportion of human tumors, where it seems to acquire gain-of-function activity that facilitates tumor onset and progression. A possible mechanism is the ability of mutant p53 proteins to physically interact with other proteins, including members of the same family, namely p63 and p73, inactivating their function. Assuming that this interaction might occurs at the level of the monomer, to investigate the molecular basis for this interaction, here, we sample the structural flexibility of the wild-type p53 monomeric protein. The results show a strong stability up to 850 ns in the DNA binding domain, with major flexibility in the N-terminal transactivations domains (TAD1 and TAD2) as well as in the C-terminal region (tetramerization domain). Several stable hydrogen bonds have been detected between N-terminal or C-terminal and DNA binding domain, and also between N-terminal and C-terminal. Essential dynamics analysis highlights strongly correlated movements involving TAD1 and the proline-rich region in the N-terminal domain, the tetramerization region in the C-terminal domain; Lys120 in the DNA binding region. The herein presented model is a starting point for further investigation of the whole protein tetramer as well as of its mutants.