Targeting mutant p53 by a SIRT1 activator YK-3-237 inhibits the proliferation of triple-negative breast cancer cells

The key vulnerabilities and therapeutic opportunities in the USP7-p53/MDM2 axis in cancer

The MDM2/MDMX-p53 circuitry is essential for controlling the development, apoptosis, immune response, angiogenesis, senescence, cell cycle progression, and proliferation of cancer cells. Research has demonstrated that USP7 exerts strong control over p53, MDM2, and MDMX stability, with multiple mediator proteins influencing the USP7-p53-MDM2/MDMX axis to modify p53 expression level and function. In cases where p53 is of the wild type (Wt-p53) in tumors, inhibiting USP7 promotes the degradation of MDM2/MDMX, leading to the activation of p53 signaling. This, in turn, results in cell cycle arrest and apoptosis. Hence, targeting USP7 presents a promising avenue for cancer therapy. Targeting USP7 in tumors that harbor mutant p53 (Mut-p53) is unlikely and remains largely unexplored due to the existence of numerous USP7 targets that function independently of p53. Considering that Mut-p53 exhibits resistance to degradation by MDM2 and other E3 ligases and also shares the same signaling pathways as Wt-p53, it is reasonable to suggest that USP7 may play a role in stabilizing Mut-p53. However, there is still much to be done in this area. If the hypothesis is correct, USP7 may be a potent target in cancers containing both Wt-p53 and Mut-p53.

Cabozantinib selectively induces proteasomal degradation of p53 somatic mutant Y220C and impedes tumor growth

Inactivation of p53 by mutations commonly occurs in human cancer. The mutated p53 proteins may escape proteolytic degradation and exhibit high expression in tumors and acquire gain-of-function activity that promotes tumor progression and chemo-resistance. Therefore, selectively targeting of the gain-of-function p53 mutants may serve as a promising therapeutic strategy for cancer prevention and treatment. In this study, we identified cabozantinib, a multikinase inhibitor currently used in the clinical treatment of several types of cancer, as a selective inducer of proteasomal degradation of the p53-Y220C mutant. We demonstrate that cabozantinib disrupts the interaction between p53Y220C and USP7, a deubiquitylating enzyme, resulting in the dissociation of p53Y220C protein from its binding with USP7 and subsequent ubiquitination and degradation mediated by CHIP (the carboxyl terminal of Hsp70-interacting protein). We also show that cabozantinib displays preferential cytotoxicity to p53Y220C-harboring cancer cells both in vitro and in vivo. This study demonstrates a novel, p53-Y220C mutant-targeted anticancer action and mechanism for cabozantinib and provides the rationale for use of this drug in the treatment of cancers that carry the p53-Y220C mutation.

Roles of Post-Translational Modifications of Transcription Factors Involved in Breast Cancer Hypoxia

BC is the most commonly diagnosed cancer and the second leading cause of cancer death among women worldwide. Cellular stress is a condition that leads to disrupted homeostasis by extrinsic and intrinsic factors. Among other stressors, hypoxia is a driving force for breast cancer (BC) progression and a general hallmark of solid tumors. Thus, intratumoral hypoxia is an important determinant of invasion, metastasis, treatment failure, prognosis, and patient mortality. Acquisition of the epithelial-mesenchymal transition (EMT) phenotype is also a consequence of tumor hypoxia. The cellular response to hypoxia is mainly regulated by the hypoxia signaling pathway, governed by hypoxia-inducible factors (HIFs), mainly HIF1α. HIFs are a family of transcription factors (TFs), which induce the expression of target genes involved in cell survival and proliferation, metabolic reprogramming, angiogenesis, resisting apoptosis, invasion, and metastasis. HIF1α cooperates with a large number of other TFs. In this review, we focused on the crosstalk and cooperation between HIF1α and other TFs involved in the cellular response to hypoxia in BC. We identified a cluster of TFs, proposed as the HIF1α-TF interactome, that orchestrates the transcription of target genes involved in hypoxia, due to their post-translational modifications (PTMs), including phosphorylation/dephosphorylation, ubiquitination/deubiquitination, SUMOylation, hydroxylation, acetylation, S-nitrosylation, and palmitoylation. PTMs of these HIF1α-related TFs drive their stability and activity, degradation and turnover, and the bidirectional translocation between the cytoplasm or plasma membrane and nucleus of BC cells, as well as the transcription/activation of proteins encoded by oncogenes or inactivation of tumor suppressor target genes. Consequently, PTMs of TFs in the HIF1α interactome are crucial regulatory mechanisms that drive the cellular response to oxygen deprivation in BC cells.

The Immunohistochemical Prognostic Value of Nuclear and Cytoplasmic Silent Information Regulator 1 Protein Expression in Saudi Patients with Breast Cancer

BACKGROUND

The mammalian NAD-dependent deacetylase sirtuin-1 family (named also silent information regulator or SIRT family, where NAD stands for "nicotinamide adenine dinucleotide" (NAD)) appears to have a dual role in several human cancers by modulating cell proliferation and death. This study examines how SIRT1 protein levels correlate with clinicopathological characteristics and survival outcomes in patients with breast cancer.

METHODS

A total of 407 BC formalin-fixed paraffin-embedded (FFPE) samples were collected from King Abdulaziz University Hospital, Saudi Arabia. SIRT1 was stained on tissue microarray slides using automated immunohistochemistry.

RESULTS

All BC subtypes expressed more nuclear SIRT1 proteins than their cytoplasm counterparts. In luminal A, luminal B, and TNBC, nuclear and cytoplasmic SIRT1 were highly associated (p < 0.001). Kaplan-Meier analysis showed reduced disease-specific survival (DSS) in H2BC with high SIRT1 nuclear expression (p = 0.001, log-rank). Moreover, the cytoplasmic expression of SIRT1 in HER2-positive BC was associated with a larger tumor size (p = 0.036) and lymph node metastasis (p = 0.045). Nuclear SIRT1 expression was also positively associated with lymph node metastasis (LNM) (p = 0.048). As low-grade tumors had a higher frequency of SIRT1 protein expression than other groups, SIRT1 expression was associated with a favorable prognosis in patients with luminal A BC (p < 0.001).

CONCLUSIONS

SIRT1 expression seems to be involved in different molecular pathways either suppressing or promoting tumor growth depending on the subtype of BC. These molecular functions require further investigations and validation on larger BC cohorts.

From regulation to deregulation of p53 in hematologic malignancies: implications for diagnosis, prognosis and therapy

The p53 protein, encoded by the TP53 gene, serves as a critical tumor suppressor, playing a vital role in maintaining genomic stability and regulating cellular responses to stress. Dysregulation of p53 is frequently observed in hematological malignancies, significantly impacting disease progression and patient outcomes. This review aims to examine the regulatory mechanisms of p53, the implications of TP53 mutations in various hematological cancers, and emerging therapeutic strategies targeting p53. We conducted a comprehensive literature review to synthesize recent findings related to p53's multifaceted role in hematologic cancers, focusing on its regulatory pathways and therapeutic potential. TP53 mutations in hematological malignancies often lead to treatment resistance and poor prognosis. Current therapeutic strategies, including p53 reactivation and gene therapy, show promise in improving treatment outcomes. Understanding the intricacies of p53 regulation and the consequences of its mutations is essential for developing effective diagnostic and therapeutic strategies in hematological malignancies, ultimately enhancing patient care and survival.

Anti-Obesity Effects of Calcium Fructoborate by Inhibiting Adipogenesis and Increasing SIRT's Expression in 3T3-L1 Cells

Obesity is a global public health problem that can lead to mortality and morbidity. Studies on the pathophysiology of obesity for effective and safe treatments are focused on the mechanisms of adipogenesis. The association between boron treatment and weight loss has been reported, but its anti-adipogenic mechanisms and effects on preadipocytes remain unclear. This study aims to investigate the effects of boron compounds boric acid (BA) and calcium fructoborate (CaFB) on adipogenesis using the most widely used in vitro 3T3-L1 cellular model. In our study, cytotoxicity, Oil Red O (ORO), gene and protein expression analyses and cellular NAD measurements of boron compounds were performed. Peroxisome proliferator-activated receptor γ (PPARγ) and CCAAT/enhancer binding protein α (C/EBPα) transcription factors are the main regulators of adipogenesis, and boron compounds affect them at gene and protein levels by showing anti-obesity effects. This is the first study to show that CaFB has anti-obesity properties in mouse adipocytes. Sirtuins, known as the longevity genes, were also activated from boron treatment. Results of this research provide new basic knowledge and insights into the effect of boron-based compounds on obesity. It also offers potential prospects for the development of effective treatment and/or supportive treatment methods.

Targeting mutant p53: a key player in breast cancer pathogenesis and beyond

The p53 mutation is the most common genetic mutation associated with human neoplasia. TP53 missense mutations, which frequently arise early in breast cancer, are present in over thirty percent of breast tumors. In breast cancer, p53 mutations are linked to a more aggressive course of the disease and worse overall survival rates. TP53 mutations are mostly seen in triple-negative breast cancer, a very diverse kind of the disease. The majority of TP53 mutations originate in the replacement of individual amino acids within the p53 protein's core domain, giving rise to a variety of variations referred to as "mutant p53s." In addition to gaining carcinogenic qualities through gain-of-function pathways, these mutants lose the typical tumor-suppressive features of p53 to variable degrees. The gain-of-function impact of stabilized mutant p53 causes tumor-specific dependency and resistance to therapy. P53 is a prospective target for cancer therapy because of its tumor-suppressive qualities and the numerous alterations that it experiences in tumors. Phenotypic abnormalities in breast cancer, notably poorly differentiated basal-like tumors are frequently linked to high-grade tumors. By comparing data from cell and animal models with clinical outcomes in breast cancer, this study investigates the molecular mechanisms that convert gene alterations into the pathogenic consequences of mutant p53's tumorigenic activity. The study delves into current and novel treatment approaches aimed at targeting p53 mutations, taking into account the similarities and differences in p53 regulatory mechanisms between mutant and wild-type forms, as well.

Oxidative stress and regulation of adipogenic differentiation capacity by sirtuins in adipose stem cells derived from female patients of advancing age

Patient age is critical for mesenchymal stem cell quality and differentiation capacity. We demonstrate that proliferation and adipogenic capacity of subcutaneous adipose stem cells (ASCs) from female patients declined with advanced age, associated with reduction in cell nucleus size, increase in nuclear lamina protein lamin B1/B2, and lamin A, upregulation of senescence marker p16INK4a and senescence-associated β-galactosidase activity. Adipogenic induction resulted in differentiation of adipocytes and upregulation of adipogenic genes CCAAT enhancer binding protein alpha, fatty acid binding protein 4, lipoprotein lipase, and peroxisome proliferator-activated receptor-γ, which was not affected by the Sirt-1 activator YK-3-237 or the Sirt-1 inhibitor EX-527. Protein expression of the stem cell markers Oct4 and Sox2 was not significantly downregulated with advanced patient age. Mitochondrial reactive oxygen species were increased in ASCs from old-aged patients, whereas protein expression of NADPH oxidases NOX1 and NOX4 was downregulated, and dual oxidase isoforms remained unchanged. Generation of nitric oxide and iNOS expression was downregulated. Protein expression of Sirt-1 and Sirt-3 decreased with patient age, whereas Sirt-2 and Sirt-5 remained unchanged. Induction of adipogenesis stimulated protein expression of Sirt-1 and Sirt-3, which was not affected upon pre-incubation with the Sirt-1-activator YK-3-237 or the Sirt-1-inhibitor EX-527. The Sirt-1 inhibitor Sirtinol downregulated adiponectin protein expression and the number of adipocytes, whereas YK-3-237 exerted stimulatory effects. In summary, our data demonstrate increased oxidative stress in ASCs of aging patients, and decline of adipogenic capacity due to Sirt-1- mediated adiponectin downregulation in elderly patients.

Post-Translational Modifications (PTMs) of mutp53 and Epigenetic Changes Induced by mutp53

Wild-type (wt) p53 and mutant forms (mutp53) play a key but opposite role in carcinogenesis. wtP53 acts as an oncosuppressor, preventing oncogenic transformation, while mutp53, which loses this property, may instead favor this process. This suggests that a better understanding of the mechanisms activating wtp53 while inhibiting mutp53 may help to design more effective anti-cancer treatments. In this review, we examine possible PTMs with which both wt- and mutp53 can be decorated and discuss how their manipulation could represent a possible strategy to control the stability and function of these proteins, focusing in particular on mutp53. The impact of ubiquitination, phosphorylation, acetylation, and methylation of p53, in the context of several solid and hematologic cancers, will be discussed. Finally, we will describe some of the recent studies reporting that wt- and mutp53 may influence the expression and activity of enzymes responsible for epigenetic changes such as acetylation, methylation, and microRNA regulation and the possible consequences of such changes.

Recent Advances on Mutant p53: Unveiling Novel Oncogenic Roles, Degradation Pathways, and Therapeutic Interventions

The p53 protein is the master regulator of cellular integrity, primarily due to its tumor-suppressing functions. Approximately half of all human cancers carry mutations in the TP53 gene, which not only abrogate the tumor-suppressive functions but also confer p53 mutant proteins with oncogenic potential. The latter is achieved through so-called gain-of-function (GOF) mutations that promote cancer progression, metastasis, and therapy resistance by deregulating transcriptional networks, signaling pathways, metabolism, immune surveillance, and cellular compositions of the microenvironment. Despite recent progress in understanding the complexity of mutp53 in neoplastic development, the exact mechanisms of how mutp53 contributes to cancer development and how they escape proteasomal and lysosomal degradation remain only partially understood. In this review, we address recent findings in the field of oncogenic functions of mutp53 specifically regarding, but not limited to, its implications in metabolic pathways, the secretome of cancer cells, the cancer microenvironment, and the regulating scenarios of the aberrant proteasomal degradation. By analyzing proteasomal and lysosomal protein degradation, as well as its connection with autophagy, we propose new therapeutical approaches that aim to destabilize mutp53 proteins and deactivate its oncogenic functions, thereby providing a fundamental basis for further investigation and rational treatment approaches for TP53-mutated cancers.

Sirtuins and Cellular Senescence in Patients with Idiopathic Pulmonary Fibrosis and Systemic Autoimmune Disorders

The sirtuin family is a heterogeneous group of proteins that play a critical role in many cellular activities. Several degenerative diseases have recently been linked to aberrant sirtuin expression and activity because of the involvement of sirtuins in maintaining cell longevity and their putative antiaging function. Idiopathic pulmonary fibrosis and progressive pulmonary fibrosis associated with systemic autoimmune disorders are severe diseases characterized by premature and accelerated exhaustion and failure of alveolar type II cells combined with aberrant activation of fibroblast proliferative pathways leading to dramatic destruction of lung architecture. The mechanisms underlying alveolar type II cell exhaustion in these disorders are not fully understood. In this review, we have focused on the role of sirtuins in the pathogenesis of idiopathic and secondary pulmonary fibrosis and their potential as biomarkers in the diagnosis and management of fibrotic interstitial lung diseases.

The compound YK 3-237 promotes pig sperm capacitation-related events

Before fertilization of the oocyte, the spermatozoa must undergo through a series of biochemical changes in the female reproductive tract named sperm capacitation. Spermatozoa regulates its functions by post-translational modifications, being historically the most studied protein phosphorylation. In addition to phosphorylation, recently, protein acetylation has been described as an important molecular mechanism with regulatory roles in several reproductive processes. However, its role on the mammal's sperm capacitation process remains unraveled. Sirtuins are a deacetylase protein family with 7 members that regulate protein acetylation. Here, we investigated the possible role of SIRT1 on pig sperm capacitation-related events by using YK 3-237, a commercial SIRT1 activator drug. SIRT1 is localized in the midpiece of pig spermatozoa. Protein tyrosine phosphorylation (focused at p32) is an event associated to pig sperm capacitation that increases when spermatozoa are in vitro capacitated in presence of YK 3-237. Eventually, YK 3-237 induces acrosome reaction in capacitated spermatozoa: YK 3-237 treatment tripled (3.40 ± 0.40 fold increase) the percentage of acrosome-reacted spermatozoa compared to the control. In addition, YK 3-237 induces sperm intracellular pH alkalinization and raises the intracellular calcium levels through a CatSper independent mechanism. YK 3-237 was not able to bypass sAC inhibition by LRE1. In summary, YK 3-237 promotes pig sperm capacitation by a mechanism upstream of sAC activation and independent of CatSper calcium channel.

SIRT1 and thrombosis

Thrombosis is a major cause of morbidity and mortality worldwide, with a complex and multifactorial pathogenesis. Recent studies have shown that SIRT1, a member of the sirtuin family of NAD + -dependent deacetylases, plays a crucial role in regulating thrombosis, modulating key pathways including endothelial activation, platelet aggregation, and coagulation. Furthermore, SIRT1 displays anti-inflammatory activity both in vitro, in vivo and in clinical studies, particularly via the reduction of oxidative stress. On these bases, several studies have investigated the therapeutic potential of targeting SIRT1 for the prevention of thrombosis. This review provides a comprehensive and critical overview of the main preclinical and clinical studies and of the current understanding of the role of SIRT1 in thrombosis.

Sirtuin1-p53: a potential axis for cancer therapy

Sirtuin1 (SIRT1) is a conserved nicotinamide adenine dinucleotide (NAD⁺)-dependent histone deacetylase that plays key roles in a range of cellular events, including the maintenance of genome stability, gene regulation, cell proliferation, and apoptosis. P53 is one of the most studied tumor suppressors and the first identified non-histone target of SIRT1. SIRT1 deacetylates p53 in a NAD⁺-dependent manner and inhibits its transcriptional activity, thus exerting action on a series of pathways related to tissue homeostasis and various pathological states. The SIRT1-p53 axis is thought to play a central role in tumorigenesis. Although SIRT1 was initially identified as a tumor promoter, evidence now indicates that SIRT1 may also act as a tumor suppressor. This seemingly contradictory evidence indicates that the functionality of SIRT1 may be dictated by different cell types and intracellular localization patterns. In this review, we summarize recent evidence relating to the interactions between SIRT1 and p53 and discuss the relative roles of these two molecules with regards to cancer-associated cellular events. We also provide an overview of current knowledge of SIRT1-p53 signaling in tumorigenesis. Given the vital role of the SIRT1-p53 pathway, targeting this axis may provide promising strategies for the treatment of cancer.

Lysine Acetylome of Breast Cancer-Derived Small Extracellular Vesicles Reveals Specific Acetylation Patterns for Metabolic Enzymes

Cancer-derived small extracellular vesicles have been proposed as promising potential biomarkers for diagnosis and prognosis of breast cancer (BC). We performed a proteomic study of lysine acetylation of breast cancer-derived small extracellular vesicles (sEVs) to understand the potential role of the aberrant acetylated proteins in the biology of invasive ductal carcinoma and triple-negative BC. Three cell lines were used as models for this study: MCF10A (non-metastatic), MCF7 (estrogen and progesterone receptor-positive, metastatic) and MDA-MB-231 (triple-negative, highly metastatic). For a comprehensive protein acetylation analysis of the sEVs derived from each cell line, acetylated peptides were enriched using the anti-acetyl-lysine antibody, followed by LC-MS/MS analysis. In total, there were 118 lysine-acetylated peptides, of which 22, 58 and 82 have been identified in MCF10A, MCF7 and MDA-MB-231 cell lines, respectively. These acetylated peptides were mapped to 60 distinct proteins and mainly identified proteins involved in metabolic pathways. Among the acetylated proteins identified in cancer-derived sEVs from MCF7 and MDA-MB-231 cell lines are proteins associated with the glycolysis pathway, annexins and histones. Five acetylated enzymes from the glycolytic pathway, present only in cancer-derived sEVs, were validated. These include aldolase (ALDOA), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), phosphoglycerate kinase (PGK1), enolase (ENO) and pyruvate kinase M1/2 (PKM). For three of these enzymes (ALDOA, PGK1 and ENO) the specific enzymatic activity was significantly higher in MDA-MB-231 when compared with MCF10A-derived sEVs. This study reveals that sEVs contain acetylated glycolytic metabolic enzymes that could be interesting potential candidates for early BC diagnostics.

The sirtuin 1 activator YK 3-237 stimulates capacitation-related events in human spermatozoa

RESEARCH QUESTION

Does sirtuin-1 (SIRT1) have a role in the human spermatozoa capacitation process?

DESIGN

Human spermatozoa were incubated for 6 h in a capacitating medium in presence or absence of the specific SIRT1 activator, YK 3-237. Several sperm parameters were determined by flow cytometry: viability, acrosome reaction and mitochondria membrane status. Sperm motility was determined objectively by computer-assisted semen analysis. Sperm capacitation status was evaluated by the extent of protein tyrosine phosphorylation and by the percentage of spermatozoa with the acrosome reacted by a calcium ionophore challenge.

RESULTS

SIRT1 was detected in the connecting piece of human spermatozoa where a lysine acetylation pattern was mainly found along the sperm tail. SIRT1 activation accelerates the occurrence of a phenotype associated with human sperm capacitation, with no differences seen in the lysine acetylation pattern. After 1 h of co-incubation of YK 3-237 with human spermatozoa, tyrosine phosphorylation levels were comparable to control levels after 6 h of incubation in capacitating conditions. In addition, the activator improved sperm responsiveness to a Ca²⁺ ionophore (A23187) challenge determined by an increase in acrosome-reacted spermatozoa (P = 0.025). Importantly, sperm viability and mitochondrial activity-related parameters assessed by flow cytometry were not affected by YK 3-237.

CONCLUSION

YK 3-237 induces capacitation-related events in human spermatozoa such an increase of tyrosine phosphorylation levels and acrosome-reacted spermatozoa after the ionophore challenge. Together, these results show that YK 3-237 affects human spermatozoa capacitation-related events by a mechanism independent of protein lysine acetylation but dependent on bicarbonate and calcium.

Role of p53 in breast cancer progression: An insight into p53 targeted therapy

The transcription factor p53 is an important regulator of a multitude of cellular processes. In the presence of genotoxic stress, p53 is activated to facilitate DNA repair, cell cycle arrest, and apoptosis. In breast cancer, the tumor suppressive activities of p53 are frequently inactivated by either the overexpression of its negative regulator MDM2, or mutation which is present in 30-35% of all breast cancer cases. Notably, the frequency of p53 mutation is highly subtype dependent in breast cancers, with majority of hormone receptor-positive or luminal subtypes retaining the wild-type p53 status while hormone receptor-negative patients predominantly carry p53 mutations with gain-of-function oncogenic activities that contribute to poorer prognosis. Thus, a two-pronged strategy of targeting wild-type and mutant p53 in different subtypes of breast cancer can have clinical relevance. The development of p53-based therapies has rapidly progressed in recent years, and include unique small molecule chemical inhibitors, stapled peptides, PROTACs, as well as several genetic-based approaches using vectors and engineered antibodies. In this review, we highlight the therapeutic strategies that are in pre-clinical and clinical development to overcome p53 inactivation in both wild-type and mutant p53-bearing breast tumors, and discuss their efficacies and limitations in pre-clinical and clinical settings.

Bromodomain Protein BRD4-Mediated Mutant p53 Transcription Promotes TNBC Progression

TP53 is the most common mutated gene in human cancer. Mutant p53 protein loses its tumor-suppressor properties and gains oncogenic activity. Mutant p53 is a therapeutic target in a broad range of cancer types. However, how mutant p53 is epigenetically regulated during tumor progression remains elusive. In this study, we found that the upregulation of mutant p53 is mediated by bromodomain protein BRD4 in triple-negative breast cancer (TNBC) cells. Inhibition of BRD4 with its inhibitor JQ1 or knockdown of BRD4 suppressed the transcription of mutant p53, which led to the re-expression of p21, the inhibition of S-phase entry, and colony formation in TNBC cells. BRD4 also positively regulated the transcription of wild-type p53, whereas JQ1 treatment and knockdown of BRD4 decreased the expression of p21 in MCF-7 cells. Knockdown of BRD4 resulted in attenuation of TNBC tumor growth in vivo. Taken together, our results uncover a novel regulatory mechanism of mutant p53 via BRD4, and suggest that the bromodomain inhibitor suppresses tumorigenesis through targeting mutant p53 in TNBC.

Inhibition of IκB Kinase Is a Potential Therapeutic Strategy to Circumvent Resistance to Epidermal Growth Factor Receptor Inhibition in Triple-Negative Breast Cancer Cells

Triple-negative breast cancer (TNBC) remains as an intractable malignancy with limited therapeutic targets. High expression of epidermal growth factor receptor (EGFR) has been associated with a poor prognosis of TNBC; however, EGFR targeting has failed with unfavorable clinical outcomes. Here, we performed a combinatorial screening of fifty-five protein kinase inhibitors with the EGFR inhibitor gefitinib in the TNBC cell line MDA-MB-231 and identified the IκB kinase (IKK) inhibitor IKK16 as a sensitizer of gefitinib. Cell viability and clonogenic survival assays were performed to evaluate the antiproliferative effects of the gefitinib and IKK16 (Gefitinib + IKK16) combination in TNBC cell lines. Western blot analyses were also performed to reveal the potential mode of action of this combination. In addition, next-generation sequencing (NGS) analysis was performed in Gefitinib+IKK16-treated cells. The Gefitinib+IKK16 treatment synergistically reduced cell viability and colony formation of TNBC cell lines such as HS578T, MDA-MB-231, and MDA-MB-468. This combination downregulated p-STAT3, p-AKT, p-mTOR, p-GSK3β, and p-RPS6. In addition, p-NF-κB and the total NF-κB were also regulated by this combination. Furthermore, NGS analysis revealed that NF-κB/RELA targets including CCL2, CXCL8, EDN1, IL-1β, IL-6, and SERPINE1 were further reduced and several potential tumor suppressors, such as FABP3, FADS2, FDFT1, SEMA6A, and PCK2, were synergistically induced by the Gefitinib-+IKK16 treatment. Taken together, we identified the IKK/NF-κB pathway as a potential target in combination of EGFR inhibition for treating TNBC.

GOF Mutant p53 in Cancers: A Therapeutic Challenge

Simple Summary

In normal cells, p53 is a protein which regulates the cell cycle progression to ensure normal cell division, growth, and development. However, in cancer, changes in the p53 DNA sequence, called genetic mutation, results in the protein either losing its normal function or exhibiting advanced pro-tumorigenic functions that lead to cancer. Importantly, cancers with mutations in the p53 protein often represent ones which are more aggressive and more resistant to chemotherapy. As a result, many studies have and continue to investigate multiple ways to target mutant p53-bearing cancer using targeted therapy, gene therapy, immunotherapy, and combination therapies. Knowledge of these strategies is important in improving the overall therapeutic response of cancers with mutant p53. This review highlights new strategies and discusses the progression of such therapies.

Abstract

TP53 is mutated in the majority of human cancers. Mutations can lead to loss of p53 expression or expression of mutant versions of the p53 protein. These mutant p53 proteins have oncogenic potential. They can inhibit any remaining WTp53 in a dominant negative manner, or they can acquire new functions that promote tumour growth, invasion, metastasis and chemoresistance. In this review we explore some of the mechanisms that make mutant p53 cells resistant to chemotherapy. As mutant p53 tumours are resistant to many traditional chemotherapies, many have sought to explore new ways of targeting mutant p53 tumours and reinstate chemosensitivity. These approaches include targeting of mutant p53 stability, mutant p53 binding partners and downstream pathways, p53 vaccines, restoration of WTp53 function, and WTp53 gene delivery. The current advances and challenges of these strategies are discussed.

3,4,3'-Tri-O-methylellagic acid as an anticancer agent: in vitro and in silico studies

We report a natural product compound isolated from Syzygium polycephalum known as 3,4,3'-tri-O-methylellagic acid (T-EA) as a candidate drug for cancer treatment. The characterization of the isolated T-EA compound was carried out using various spectroscopic methods. The in vitro evaluation showcased the inhibition activity of T-EA towards the T47D and HeLa cell lines with EC₅₀ values of 55.35 ± 6.28 μg mL^-1 and 12.57 ± 2.22 μg mL^-1, respectively. Meanwhile, the in silico evaluation aimed to understand the interaction of T-EA with enzymes responsible for cancer regulation at the molecular level by targeting the hindrance of cyclin-dependent kinase 9 (CDK9) and sirtuin 1 (SIRT1) enzymes. T-EA showed a binding free energy towards the SIRT1 protein of ΔG _{bind (MM-GBSA)}: -30.98 ± 0.25 kcal mol^-1 and ΔG _{bind (MM-PBSA)}: -24.07 ± 0.30 kcal mol^-1, while that of CDK9 was ΔG _{bind (MM-GBSA)}: -29.50 ± 0.22 kcal mol^-1 and ΔG _{bind (MM-PBSA)}: -25.87 ± 0.40 kcal mol^-1. The obtained results from this research could be considered as important information on 3,4,3'-tri-O-methylellagic acid as a drug to treat cervical and breast cancers.

Versatile role of sirtuins in metabolic disorders: From modulation of mitochondrial function to therapeutic interventions

Sirtuins (SIRT1-7) are distinct histone deacetylases (HDACs) whose activity is determined by cellular metabolic status andnicotinamide adenine dinucleotide (NAD⁺ ) levels. HDACs of class III are the members of the SIRT's protein family. SIRTs are the enzymes that modulate mitochondrial activity and energy metabolism. SIRTs have been linked to a number of clinical and physiological operations, such as energy responses to low-calorie availability, aging, stress resistance, inflammation, and apoptosis. Mammalian SIRT2 orthologs have been identified as SIRT1-7 that are found in several subcellular sections, including the cytoplasm (SIRT1, 2), mitochondrial matrix (SIRT3, 4, 5), and the core (SIRT1, 2, 6, 7). For their deacetylase or ADP-ribosyl transferase action, all SIRTs require NAD⁺ and are linked to cellular energy levels. Evolutionarily, SIRT1 is related to yeast's SIRT2 as well as received primary attention in the circulatory system. An endogenous protein, SIRT1 is involved in the development of heart failure and plays a key role in cell death and survival. SIRT2 downregulation protects against ischemic-reperfusion damage. Increase in human longevity is caused by an increase in SIRT3 expression. Cardiomyocytes are also protected by SIRT3 from oxidative damage and aging, as well as suppressing cardiac hypertrophy. SIRT4 and SIRT5 perform their roles in the heart. SIRT6 has also been linked to a reduction in heart hypertrophy. SIRT7 is known to be involved in the regulation of stress responses and apoptosis in the heart.

Phosphoproteomic Analysis of Breast Cancer-Derived Small Extracellular Vesicles Reveals Disease-Specific Phosphorylated Enzymes

Small membrane-derived extracellular vesicles have been proposed as participating in several cancer diseases, including breast cancer (BC). We performed a phosphoproteomic analysis of breast cancer-derived small extracellular vesicles (sEVs) to provide insight into the molecular and cellular regulatory mechanisms important for breast cancer tumor progression and metastasis. We examined three cell line models for breast cancer: MCF10A (non-malignant), MCF7 (estrogen and progesterone receptor-positive, metastatic), and MDA-MB-231 (triple-negative, highly metastatic). To obtain a comprehensive overview of the sEV phosphoproteome derived from each cell line, effective phosphopeptide enrichment techniques IMAC and TiO2, followed by LC-MS/MS, were performed. The phosphoproteome was profiled to a depth of 2003 phosphopeptides, of which 207, 854, and 1335 were identified in MCF10A, MCF7, and MDA-MB-231 cell lines, respectively. Furthermore, 2450 phosphorylation sites were mapped to 855 distinct proteins, covering a wide range of functions. The identified proteins are associated with several diseases, mostly related to cancer. Among the phosphoproteins, we validated four enzymes associated with cancer and present only in sEVs isolated from MCF7 and MDA-MB-231 cell lines: ATP citrate lyase (ACLY), phosphofructokinase-M (PFKM), sirtuin-1 (SIRT1), and sirtuin-6 (SIRT6). With the exception of PFKM, the specific activity of these enzymes was significantly higher in MDA-MB-231 when compared with MCF10A-derived sEVs. This study demonstrates that sEVs contain functional metabolic enzymes that could be further explored for their potential use in early BC diagnostic and therapeutic applications.

NMNAT promotes glioma growth through regulating post-translational modifications of P53 to inhibit apoptosis

Gliomas are highly malignant brain tumors with poor prognosis and short survival. NAD⁺ has been shown to impact multiple processes that are dysregulated in cancer; however, anti-cancer therapies targeting NAD⁺ synthesis have had limited success due to insufficient mechanistic understanding. Here, we adapted a Drosophila glial neoplasia model and discovered the genetic requirement for NAD⁺ synthase nicotinamide mononucleotide adenylyltransferase (NMNAT) in glioma progression in vivo and in human glioma cells. Overexpressing enzymatically active NMNAT significantly promotes glial neoplasia growth and reduces animal viability. Mechanistic analysis suggests that NMNAT interferes with DNA damage-p53-caspase-3 apoptosis signaling pathway by enhancing NAD⁺-dependent posttranslational modifications (PTMs) poly(ADP-ribosyl)ation (PARylation) and deacetylation of p53. Since PARylation and deacetylation reduce p53 pro-apoptotic activity, modulating p53 PTMs could be a key mechanism by which NMNAT promotes glioma growth. Our findings reveal a novel tumorigenic mechanism involving protein complex formation of p53 with NAD⁺ synthetic enzyme NMNAT and NAD⁺-dependent PTM enzymes that regulates glioma growth.

Tumor suppressor p53: Biology, signaling pathways, and therapeutic targeting

TP53 is the most commonly mutated gene in human cancer with over 100,000 literature citations in PubMed. This is a heavily studied pathway in cancer biology and oncology with a history that dates back to 1979 when p53 was discovered. The p53 pathway is a complex cellular stress response network with multiple diverse inputs and downstream outputs relevant to its role as a tumor suppressor pathway. While inroads have been made in understanding the biology and signaling in the p53 pathway, the p53 family, transcriptional readouts, and effects of an array of mutants, the pathway remains challenging in the realm of clinical translation. While the role of mutant p53 as a prognostic factor is recognized, the therapeutic modulation of its wild-type or mutant activities remain a work-in-progress. This review covers current knowledge about the biology, signaling mechanisms in the p53 pathway and summarizes advances in therapeutic development.

Structural and Drug Targeting Insights on Mutant p53

p53 is a transcription factor with a pivotal role in cell homeostasis and fate. Its impairment is a major event in tumor onset and development. In fact, about half of human cancers bear TP53 mutations that not only halt the normal function of p53, but also may acquire oncogenic gain of functions that favor tumorigenesis. Although considered undruggable for a long time, evidence has proven the capability of many compounds to restore a wild-type (wt)-like function to mutant p53 (mutp53). However, they have not reached the clinic to date. Structural studies have strongly contributed to the knowledge about p53 structure, stability, dynamics, function, and regulation. Importantly, they have afforded relevant insights into wt and mutp53 pharmacology at molecular levels, fostering the design and development of p53-targeted anticancer therapies. Herein, we provide an integrated view of mutp53 regulation, particularly focusing on mutp53 structural traits and on targeting agents capable of its reactivation, including their biological, biochemical and biophysical features. With this, we expect to pave the way for the development of improved small molecules that may advance precision cancer therapy by targeting p53.

Potentiating Therapeutic Effects of Epidermal Growth Factor Receptor Inhibition in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is a subset of breast cancer with aggressive characteristics and few therapeutic options. The lack of an appropriate therapeutic target is a challenging issue in treating TNBC. Although a high level expression of epidermal growth factor receptor (EGFR) has been associated with a poor prognosis among patients with TNBC, targeted anti-EGFR therapies have demonstrated limited efficacy for TNBC treatment in both clinical and preclinical settings. However, with the advantage of a number of clinically approved EGFR inhibitors (EGFRis), combination strategies have been explored as a promising approach to overcome the intrinsic resistance of TNBC to EGFRis. In this review, we analyzed the literature on the combination of EGFRis with other molecularly targeted therapeutics or conventional chemotherapeutics to understand the current knowledge and to provide potential therapeutic options for TNBC treatment.

Dual Inhibition of AKT and MEK Pathways Potentiates the Anti-Cancer Effect of Gefitinib in Triple-Negative Breast Cancer Cells

There is an unmet medical need for the development of new targeted therapeutic strategies for triple-negative breast cancer (TNBC). With drug combination screenings, we found that the triple combination of the protein kinase inhibitors (PKIs) of the epidermal growth factor receptor (EGFR), v-akt murine thymoma viral oncogene homolog (AKT), and MAPK/ERK kinase (MEK) is effective in inducing apoptosis in TNBC cells. A set of PKIs were first screened in combination with gefitinib in the TNBC cell line, MDA-MB-231. The AKT inhibitor, AT7867, was identified and further analyzed in two mesenchymal stem-like (MSL) subtype TNBC cells, MDA-MB-231 and HS578T. A combination of gefitinib and AT7867 reduced the proliferation and long-term survival of MSL TNBC cells. However, gefitinib and AT7867 induced the activation of the rat sarcoma (RAS)/ v-raf-1 murine leukemia viral oncogene homolog (RAF)/MEK/ extracellular signal-regulated kinase (ERK) pathway. To inhibit this pathway, MEK/ERK inhibitors were further screened in MDA-MB-231 cells in the presence of gefitinib and AT7867. As a result, we identified that the MEK inhibitor, PD-0325901, further enhanced the anti-proliferative and anti-clonogenic effects of gefitinib and AT7867 by inducing apoptosis. Our results suggest that the dual inhibition of the AKT and MEK pathways is a novel potential therapeutic strategy for targeting EGFR in TNBC cells.

Differential Response of Lung Cancer Cells, with Various Driver Mutations, to Plant Polyphenol Resveratrol and Vitamin D Active Metabolite PRI-2191

Plant polyphenols and vitamins D exhibit chemopreventive and therapeutic anticancer effects. We first evaluated the biological effects of the plant polyphenol resveratrol (RESV) and vitamin D active metabolite PRI-2191 on lung cancer cells having different genetic backgrounds. RESV and PRI-2191 showed divergent responses depending on the genetic profile of cells. Antiproliferative activity of PRI-2191 was noticeable in EGFRmut cells, while RESV showed the highest antiproliferative and caspase-3-inducing activity in KRASmut cells. RESV upregulated p53 expression in wtp53 cells, while downregulated it in mutp53 cells with simultaneous upregulation of p21 expression in both cases. The effect of PRI-2191 on the induction of CYP24A1 expression was enhanced by RESV in two KRASmut cell lines. The effect of RESV combined with PRI-2191 on cytokine production was pronounced and modulated. RESV cooperated with PRI-2191 in regulating the expression of IL-8 in EGFRmut cells, while OPN in KRASmut cells and PD-L1 in both cell subtypes. We hypothesize that the differences in response to RESV and PRI-2191 between EGFRmut and KRASmut cell lines result from the differences in epigenetic modifications since both cell subtypes are associated with the divergent smoking history that can induce epigenetic alterations.

Verteporfin disrupts multiple steps of autophagy and regulates p53 to sensitize osteosarcoma cells

Background

Osteosarcoma (OS) is a malignant tumor of the bone mostly observed in children and adolescents. The current treatment approach includes neoadjuvant and adjuvant chemotherapy; however, drug resistance often hinders therapy in OS patients. Also, the post-relapse survival of OS patients is as low as 20%. We therefore planned to understand the molecular cause for its poor prognosis and design an appropriate therapeutic strategy to combat the disease.

Methods

We analyzed OS patient dataset from Gene Expression Omnibus (GEO) and identified the differentially expressed genes and the top deregulated pathways in OS. Subsequently, drugs targeting the major de-regulated pathways were selected and the following assays were conducted- MTT assay to assess cytotoxicity of drugs in OS cells; immunoblotting and immunostaining to analyze key protein expression and localization after drug treatment; LysoTracker staining to monitor lysosomes; Acridine Orange to label acidic vesicles; and DCFDA to measure Reactive Oxygen Species (ROS).

Results

The differential gene expression analysis from OS patient dataset implicated the striking involvement of cellular processes linked to autophagy and protein processing in the development of OS. We therefore selected the FDA approved drugs, chloroquine (CQ) and verteporfin (VP) known for autophagy inhibitory and proteotoxic functions to explore against OS. Importantly, VP, but not CQ, showed an extensive dose-dependent cytotoxicity. It resulted in autophagy disruption at multiple steps extending from perturbation of early autophagic processes, inhibition of autophagic flux to induction of lysosomal instability. Interestingly, VP treated protein lysates showed a ROS-dependent high molecular weight (HMW) band when probed for P62 and P53 protein. Further, VP triggered accumulation of ubiquitinated proteins as well. Since VP had a pronounced disruptive effect on cellular protein homeostasis, we explored the possibility of simultaneous inhibition of the ubiquitin-proteasomal system (UPS) by MG-132 (MG). Addition of a proteasomal inhibitor significantly aggravated VP induced cytotoxicity. MG co-treatment also led to selective targeting of P53 to the lysosomes.

Conclusion

Herein, we propose VP and MG induce regulation of autophagy and protein homeostasis which can be exploited as an effective therapeutic strategy against osteosarcoma.

Cancer Stemness: p53 at the Wheel

The tumor suppressor p53 maintains an equilibrium between self-renewal and differentiation to sustain a limited repertoire of stem cells for proper development and maintenance of tissue homeostasis. Inactivation of p53 disrupts this balance and promotes pluripotency and somatic cell reprogramming. A few reports in recent years have indicated that prevalent TP53 oncogenic gain-of-function (GOF) mutations further boosts the stemness properties of cancer cells. In this review, we discuss the role of wild type p53 in regulating pluripotency of normal stem cells and various mechanisms that control the balance between self-renewal and differentiation in embryonic and adult stem cells. We also highlight how inactivating and GOF mutations in p53 stimulate stemness in cancer cells. Further, we have explored the various mechanisms of mutant p53-driven cancer stemness, particularly emphasizing on the non-coding RNA mediated epigenetic regulation. We have also analyzed the association of cancer stemness with other crucial gain-of-function properties of mutant p53 such as epithelial to mesenchymal transition phenotypes and chemoresistance to understand how activation of one affects the other. Given the critical role of cancer stem-like cells in tumor maintenance, cancer progression, and therapy resistance of mutant p53 tumors, targeting them might improve therapeutic efficacy in human cancers with TP53 mutations.

Circular and linear: a tale of aptamer selection for the activation of SIRT1 to induce death in cancer cells

It is a challenge to select the right target to treat conditions without affecting non-diseased cells. Cancer belongs to the top 10 causes of death in the world and it remains difficult to treat. Amongst cancer emerging targets, silent information regulator 1 (SIRT1) - a histone deacetylase - has shown many roles in cancer, ageing and metabolism. Here we report novel SIRT1 ligands that bind and modulate the activity of SIRT1 within cells and enhance its enzymatic activity. We developed a modified aptamer capable of binding to and forming a complex with SIRT1. Our ligands are aptamers, they can be made of DNA or RNA oligonucleotides, their binding domain can recognise a target with very high affinity and specificity. We used the systematic evolution of ligands by exponential enrichment (SELEX) technique to develop circular and linear aptamers selectively binding to SIRT1. Cellular consequences of the interaction were monitored by fluorescence microscopy, cell viability assay, stability and enzymatic assays. Our results indicate that from our pool of aptamers, circular AC3 penetrates cancerous cells and is recruited to modulate the SIRT1 activity. This modulation of SIRT1 resulted in anticancer activity on different cancer cell lines. Furthermore, this modified aptamer showed no toxicity on one non-cancerous cell line and was stable in human plasma. We have demonstrated that aptamers are efficient tools for localisation of internal cell targets, and in this particular case, anticancer activity through modulation of SIRT1.

Exploring the multiple roles of guardian of the genome: P53

Background

Cells have evolved balanced mechanisms to protect themselves by initiating a specific response to a variety of stress. TheTP53gene, encoding P53 protein, is one of the many widely studied genes in human cells owing to its multifaceted functions and complex dynamics. The tumour-suppressing activity of P53 plays a principal role in the cellular response to stress. The majority of the human cancer cells exhibit the inactivation of the P53 pathway. In this review, we discuss the recent advancements in P53 research with particular focus on the role of P53 in DNA damage responses, apoptosis, autophagy, and cellular metabolism. We also discussed important P53-reactivation strategies that can play a crucial role in cancer therapy and the role of P53 in various diseases.

Main body

We used electronic databases like PubMed and Google Scholar for literature search. In response to a variety of cellular stress such as genotoxic stress, ischemic stress, oncogenic expression, P53 acts as a sensor, and suppresses tumour development by promoting cell death or permanent inhibition of cell proliferation. It controls several genes that play a role in the arrest of the cell cycle, cellular senescence, DNA repair system, and apoptosis. P53 plays a crucial role in supporting DNA repair by arresting the cell cycle to purchase time for the repair system to restore genome stability. Apoptosis is essential for maintaining tissue homeostasis and tumour suppression. P53 can induce apoptosis in a genetically unstable cell by interacting with many pro-apoptotic and anti-apoptotic factors.

Furthermore, P53 can activate autophagy, which also plays a role in tumour suppression. P53 also regulates many metabolic pathways of glucose, lipid, and amino acid metabolism. Thus under mild metabolic stress, P53 contributes to the cell’s ability to adapt to and survive the stress.

Conclusion

These multiple levels of regulation enable P53 to perform diversified roles in many cell responses. Understanding the complete function of P53 is still a work in progress because of the inherent complexity involved in between P53 and its target proteins. Further research is required to unravel the mystery of this Guardian of the genome “TP53”.

Expression of SIRT1, SIRT3 and SIRT6 Genes for Predicting Survival in Triple-Negative and Hormone Receptor-Positive Subtypes of Breast Cancer

Triple-negative breast cancer (TNBC) is characterized by aggressive phenotype and a poorer prognosis compared to the estrogen and progesterone receptor positive, Her2 negative (ER + PR + Her2-) breast cancer. Increasing evidence suggests that sirtuins, a family of histone deacetylases, could have an important role in aggressiveness of TNBC's. The current study evaluated the potential clinical relevance of SIRT1, SIRT3 and SIRT6 gene expressions in two prognostically distinctive subtypes of breast cancer, the most aggressive TNBC and the least aggressive ER + PR + Her2- tumors. Total RNAs were isolated from 48 TNBC and 63 ER + PR + Her2- tumor samples. Relative gene expression was determined by SYBR Green RT-PCR and delta-delta Ct method, normalized to GAPDH. Mean gene expression of both SIRT1 and SIRT3 was significantly lower in the TNBC compared to ER + PR + Her2- tumors (p = 0.0001). Low SIRT1 and SIRT6 expressions associated with worse overall survival in ER + PR + Her2- patients (p = 0.039, p = 0.006, respectively), while TNBC patients with high SIRT1 tend to have a poor prognosis (p = 0.057). In contrast, high expression of SIRT3 in TNBC patients associated with higher histological grade (p = 0.027) and worse overall survival (p = 0.039). The Cox regression analysis revealed that low SIRT1 expression could be an independent prognostic marker of poor survival in ER + PR + Her2- breast cancers (HR = 11.765, 95% CI:1.234-100, p = 0.033). Observed differential expression of SIRT1, SIRT3 and SIRT6 genes in TNBC and ER + PR + Her2- subtypes, with opposite effects on patients' survival, suggests context-dependent mechanisms underlying aggressiveness of breast cancer. Further investigations are necessary to evaluate sirtuins as potential biomarkers and therapeutic targets in breast cancer.

A tetraprenylated benzophenone 7-epiclusianone induces cell cycle arrest at G1/S transition by modulating critical regulators of cell cycle in breast cancer cell lines

Breast cancer is a complex disease and encompassing different types of tumor. Although advances in understanding of the molecular bases of breast cancer biology, the therapeutic proposals available still are not effective. In this scenario, the present study aimed to evaluate the mechanisms associated to antitumor activity of 7-Epiclusianone (7-Epi), a tetraprenylated benzophenone, on luminal A (MCF-7) and claudin-low (Hs 578T) breast cancer cell lines. We found that 7-Epi efficiently inhibited cell proliferation and migration of these cells; however MCF-7 was slightly more responsive than Hs 578T. Cell cycle analysis showed accumulation of cells at G0/G1 phase with drastic reduction of S population in treated cultures. This effect was associated to downregulation of CDKN1A (p21) and cyclin E in both cell lines. In addition, 7-Epi reduced cyclin D1 and p-ERK expression levels in MCF-7 cell line. Cytotoxic effect of 7-Epi on breast cancer cell lines was associated to its ability to increase BAX/BCL-2 ratio. In conclusion, our findings showed that 7-Epi is a promising antitumor agent against breast cancer by modulating critical regulators of the cell cycle and apoptosis.

Targeting codon 158 p53-mutant cancers via the induction of p53 acetylation

Gain of function (GOF) DNA binding domain (DBD) mutations of TP53 upregulate chromatin regulatory genes that promote genome-wide histone methylation and acetylation. Here, we therapeutically exploit the oncogenic GOF mechanisms of p53 codon 158 (Arg¹⁵⁸) mutation, a DBD mutant found to be prevalent in lung carcinomas. Using high throughput compound screening and combination analyses, we uncover that acetylating mutp53^R158G could render cancers susceptible to cisplatin-induced DNA stress. Acetylation of mutp53^R158G alters DNA binding motifs and upregulates TRAIP, a RING domain-containing E3 ubiquitin ligase which dephosphorylates IĸB and impedes nuclear translocation of RelA (p65), thus repressing oncogenic nuclear factor kappa-B (NF-ĸB) signaling and inducing apoptosis. Given that this mechanism of cytotoxic vulnerability appears inapt in p53 wild-type (WT) or other hotspot GOF mutp53 cells, our work provides a therapeutic opportunity specific to Arg¹⁵⁸-mutp53 tumors utilizing a regimen consisting of DNA-damaging agents and mutp53 acetylators, which is currently being pursued clinically.

Codon 158 gain-of-function mutant p53 (158-mutp53) promotes tumourigenesis in lung cancer. Here, the authors show that 158-mutp53 render cancers sensitive to cisplatin and p53 acetylation agents through a mechanism where acetylated mutant p53 upregulates TRAIP and inhibits NF-ĸB signaling.

A Stilbenoid Isorhapontigenin as a Potential Anti-Cancer Agent against Breast Cancer through Inhibiting Sphingosine Kinases/Tubulin Stabilization

Isorhapontigenin (ISO), a tetrahydroxylated stilbenoid, is an analog of resveratrol (Rsv). The various biological activities of Rsv and its derivatives have been previously reported in the context of both cancer and inflammation. However, the anti-cancer effect of ISO against breast cancer has not been well established, despite being an orally bioavailable dietary polyphenol. In this study, we determine the anti-cancer effects of ISO against breast cancer using MCF7, T47D, and MDA-MB-231 cell lines. We observed that ISO induces breast cancer cell death, cell cycle arrest, oxidative stress, and the inhibition of cell proliferation. Additionally, sphingosine kinase inhibition by ISO controlled tubulin polymerization and cancer cell growth by regulating MAPK/PI3K-mediated cell cycle arrest in MCF7 cells. Interestingly, SPHK1/2 gene silencing increased oxidative stress, cell death, and tubulin destabilization in MCF7 cells. This suggests that the anti-cancer effect of ISO can be regulated by SPHK/tubulin destabilization pathways. Overall, ISO successfully induced breast cancer cell death and cell growth arrest, suggesting this phytochemical is a better alternative for breast cancer treatment. Further studies in animal models could confirm the potency and usability of ISO over Rsv for targeting breast cancer, potentially posing an alternative candidate for improved therapy in the near future.

Inhibition of SIRT1 deacetylase and p53 activation uncouples the anti-inflammatory and chemopreventive actions of NSAIDs

Background

Nonsteroidal anti-inflammatory drugs (NSAIDs) have been proposed as chemopreventive agents for many tumours; however, the mechanism responsible for their anti-neoplastic activity remains elusive and the side effects due to cyclooxygenase (COX) inhibition prevent this clinical application.

Methods

Molecular biology, in silico, cellular and in vivo tools, including innovative in vivo imaging and classical biochemical assays, were applied to identify and characterise the COX-independent anti-cancer mechanism of NSAIDs.

Results

Here, we show that tumour-protective functions of NSAIDs and exisulind (a sulindac metabolite lacking anti-inflammatory activity) occur through a COX-independent mechanism. We demonstrate these NSAIDs counteract carcinogen-induced proliferation by inhibiting the sirtuin 1 (SIRT1) deacetylase activity, augmenting acetylation and activity of the tumour suppressor p53 and increasing the expression of the antiproliferative gene p21. These properties are shared by all NSAIDs except for ketoprofen lacking anti-cancer properties. The clinical interest of the mechanism identified is underlined by our finding that p53 is activated in mastectomy patients undergoing intraoperative ketorolac, a treatment associated with decreased relapse risk and increased survival.

Conclusion

Our study, for the first-time, links NSAID chemopreventive activity with direct SIRT1 inhibition and activation of the p53/p21 anti-oncogenic pathway, suggesting a novel strategy for the design of tumour-protective drugs.

Dual Tumor Suppressor and Tumor Promoter Action of Sirtuins in Determining Malignant Phenotype

Sirtuins (SIRTs), class III histone deacetylases, are differentially expressed in several human cancers, where they display both oncogenic and tumor-suppressive properties depending on cellular context and experimental conditions. SIRTs are involved in many important biological processes and play a critical role in cancer initiation, promotion, and progression. A growing body of evidence indicates the involvement of SIRTs in regulating three important tumor processes: epithelial-to-mesenchymal transition (EMT), invasion, and metastasis. Many SIRTs are responsible for cellular metabolic reprogramming and drug resistance by inactivating cell death pathways and promoting uncontrolled proliferation. In this review, we summarize current knowledge on the role of SIRTs in cancer and discuss their puzzling dual function as tumor suppressors and tumor promoters, important for the future development of novel tailored SIRT-based cancer therapies.

Regulators of Oncogenic Mutant TP53 Gain of Function

The tumor suppressor p53 (TP53) is the most frequently mutated human gene. Mutations in TP53 not only disrupt its tumor suppressor function, but also endow oncogenic gain-of-function (GOF) activities in a manner independent of wild-type TP53 (wtp53). Mutant TP53 (mutp53) GOF is mainly mediated by its binding with other tumor suppressive or oncogenic proteins. Increasing evidence indicates that stabilization of mutp53 is crucial for its GOF activity. However, little is known about factors that alter mutp53 stability and its oncogenic GOF activities. In this review article, we primarily summarize key regulators of mutp53 stability/activities, including genotoxic stress, post-translational modifications, ubiquitin ligases, and molecular chaperones, as well as a single nucleotide polymorphism (SNP) and dimer-forming mutations in mutp53.

Breaking down the Contradictory Roles of Histone Deacetylase SIRT1 in Human Breast Cancer

Breast cancer (BC) is the most common type of cancer in women worldwide; it is a multifactorial genetic disease. Acetylation and deacetylation are major post-translational protein modifications that regulate gene expression and the activity of a myriad of oncoproteins. Aberrant deacetylase activity can promote or suppress tumorigenesis and cancer metastasis in different types of human cancers, including breast cancer. Sirtuin-1 (SIRT1) is a class-III histone deacetylase (HDAC) that deacetylates both histone and non-histone targets. The often-described ‘regulator of regulators’ is deeply implicated in apoptosis, gene regulation, genome maintenance, DNA repair, aging, and cancer development. However, despite the accumulated studies over the past decade, the role of SIRT1 in human breast cancer remains a subject of debate and controversy. The ambiguity surrounding the implications of SIRT1 in breast tumorigenesis stems from the discrepancy between studies, which have shown both tumor-suppressive and promoting functions of SIRT1. Furthermore, studies have shown that SIRT1 deficiency promotes or suppresses tumors in breast cancer, making it an attractive therapeutic target in cancer treatment. This review provides a comprehensive examination of the various implications of SIRT1 in breast cancer development and metastasis. We will also discuss the mechanisms underlying the conflicting roles of SIRT1, as well as its selective modulators, in breast carcinogenesis.

An overview of Sirtuins as potential therapeutic target: Structure, function and modulators

Sirtuin (Yeast Silent Information RegulatorsⅡ, Sir2) was first discovered in the 1970s. Because of its function by removing acetylated groups from histones in the presence of nicotinamide adenine dinucleotide (NAD⁺), waves of research have assessed the potential of Sirtuin as a therapeutic target. The Sirtuin family, which is widely distributed throughout the nature, has been divided into seven human isoforms (Sirt1-Sirt7). They are thought to be closely related to some aging diseases such as cardiovascular disorders, neurodegeneration, and tumors. Herein, we present a comprehensive review of the structure, function and modulators of Sirtuins, which is expected to be beneficial to relevant studies.

Sirt1 protects neural stem cells from apoptosis by decreasing acetylation of histone 3K9

Objective

To explore the role and mechanism of Sirt1 in protecting neural stem cells (NSCs) from apoptosis.

Materials and methods

Transfection was used to overexpress Sirt1 in rat NSCs. The effect of Sirt1 overexpression on camptothecin-induced apoptosis of NSCs was evaluated. Western blotting was used to examine the expression of Sirt1, cleaved caspase-3, and acetylated histone 3K9.

Results

Overexpression of Sirt1 in NSCs decreased the cleavage of caspase-3 and acetylation of histone 3K9.

Conclusion

Sirt1 may protect NSCs from apoptosis by decreasing the acetylation of histone 3 on K9.

SIRT1-dependent epigenetic regulation of H3 and H4 histone acetylation in human breast cancer

Breast cancer is the most frequently diagnosed malignancy in women worldwide. It is well established that the complexity of carcinogenesis involves profound epigenetic deregulations that contribute to the tumorigenesis process. Deregulated H3 and H4 acetylated histone marks are amongst those alterations. Sirtuin-1 (SIRT1) is a class-III histone deacetylase deeply involved in apoptosis, genomic stability, gene expression regulation and breast tumorigenesis. However, the underlying molecular mechanism by which SIRT1 regulates H3 and H4 acetylated marks, and consequently cancer-related gene expression in breast cancer, remains uncharacterized. In this study, we elucidated SIRT1 epigenetic role and analyzed the link between the latter and histones H3 and H4 epigenetic marks in all 5 molecular subtypes of breast cancer. Using a cohort of 135 human breast tumors and their matched normal tissues, as well as 5 human-derived cell lines, we identified H3k4ac as a new prime target of SIRT1 in breast cancer. We also uncovered an inverse correlation between SIRT1 and the 3 epigenetic marks H3k4ac, H3k9ac and H4k16ac expression patterns. We showed that SIRT1 modulates the acetylation patterns of histones H3 and H4 in breast cancer. Moreover, SIRT1 regulates its H3 acetylated targets in a subtype-specific manner. Furthermore, SIRT1 siRNA-mediated knockdown increases histone acetylation levels at 6 breast cancer-related gene promoters: AR, BRCA1, ERS1, ERS2, EZH2 and EP300. In summary, this report characterizes for the first time the epigenetic behavior of SIRT1 in human breast carcinoma. These novel findings point to a potential use of SIRT1 as an epigenetic therapeutic target in breast cancer.

A novel small-molecule activator of Sirtuin-1 induces autophagic cell death/mitophagy as a potential therapeutic strategy in glioblastoma

Sirtuin-1 (SIRT1), the mammalian ortholog of yeast Sir2p, is well known to be a highly conserved NAD⁺-dependent protein deacetylase that has been emerging as a key cancer target. Autophagy, an evolutionarily conserved, multi-step lysosomal degradation process, has been implicated in cancer. Accumulating evidence has recently revealed that SIRT1 may act as a tumor suppressor in several types of cancer, and thus activating SIRT1 would represent a possible therapeutic strategy. Thus, in our study, we identified that SIRT1 was a key prognostic factor in brain cancer based upon The Cancer Genome Atlas and tissue microarray analyses. Subsequently, we screened a series of potential small-molecule activators of SIRT1 from Drugbank, and found the best candidate compound F0911-7667 (hereafter, named Comp 5), which showed a good deacetylase activity for SIRT1 rather than other Sirtuins. In addition, we demonstrated that Comp 5-induced autophagic cell death via the AMPK-mTOR-ULK complex in U87MG and T98G cells. Interestingly, Comp 5-induced mitophagy by the SIRT1–PINK1–Parkin pathway. Further iTRAQ-based proteomics analyses revealed that Comp 5 could induce autophagy/mitophagy by downregulating 14-3-3γ, catalase, profilin-1, and HSP90α. Moreover, we showed that Comp 5 had a therapeutic potential on glioblastoma (GBM) and induced autophagy/mitophagy by activating SIRT1 in vivo. Together, these results demonstrate a novel small-molecule activator of SIRT1 that induces autophagic cell death/mitophagy in GBM cells, which would be utilized to exploit this compound as a leading drug for future cancer therapy.

Combination of SIRT1 and Src overexpression suggests poor prognosis in luminal breast cancer

Objectives

1) Analyze the correlation of SIRT1 and Src with human breast cancer (BC) prognosis; 2) explore the roles of SIRT1 and Src in BC cell proliferation, tumor invasion, and metastasis; and 3) analyze the correlation and interaction between SIRT1 and Src.

Materials and methods

1) Tissue microarray was used to analyze the expression of SIRT1 and Src in human BC tissues and the correlation between protein expression and cancer prognosis; 2) CCK8 assay was used to determine the influence of SIRT1 and Src inhibitors on BC cell proliferation; 3) Transwell migration assay and wound healing assay were used to determine the effect of SIRT1 and Src inhibitors on BC cell migration and invasion; and 4) Western blotting was used to analyze the correlation and interaction between SIRT1 and Src.

Results

1) Combination of SIRT1 and/or Src positivity is a prognosis factor in BC, especially in luminal type; 2) MCF-7 cell proliferation is suppressed by SIRT1 inhibitor Ex527, and cell migration and invasion were inhibited by Src inhibitor bosutinib; 3) combined with Ex527, bosutinib has a significantly increased effect on MCF-7 cell migration suppression; and 4) there is a positive association between SIRT1 and Src both in BC tissues and in MCF-7 cells.

Conclusion

1) SIRT1 and Src overexpression are both correlated with poor prognosis in human BC; 2) SIRT1 + Src (SIRT1 and/or Src positivity) is a fine prognosis model for luminal-type BC; 3) SIRT1 is a copromotor of Src in BC migration and invasion, but not in cell proliferation; and 4) our results suggest a potential interaction or a common regulation pathway between SIRT1 and Src expression and activity.

An in silico approach in predicting the possible mechanism involving restoration of wild-type p53 functions by small molecular weight compounds in tumor cells expressing R273H mutant p53

R273H mutant p53 is a DNA-contact mutant that renders p53 dysfunctional due to a single substitution of Arg273 for His273. Rescuing R273 mutant p53 implies that a competent molecule would have to bind to the site of DNA-contact hot spots to complement the loss of contact with the DNA-binding domain. Here, curcumin, flavokawain B, and alpinetin were docked against the crystal structure of R273H mutant p53 in silico. Consequently, all the compounds bind to the cavity of R273H mutant p53 with a dissociation constant estimated to have 36.57, 70.77, and 75.11 µM for curcumin, flavokawain B, and alpinetin, respectively. Subsequently, each molecule was able to bind to the R273H mutant p53 by interacting with the DNA-contact hot spot Arg248 and mutant R273H, thereby compensating for the loss of direct contact with the DNA-binding domain. Furthermore, all the molecules were able to induce a direct contact with the consensus site of the DNA binding domain, thus maintaining DNA-contact residues with the DNA. The present findings offer preliminary indirect supporting evidence that small molecular weight compounds may certainly rescue DNA-contact mutant p53, which may lay a foundation for designing a competent and effective molecule capable of rescuing mutant p53 in tumor cells expressing R273H mutant p53.

Dual SIRT1 expression patterns strongly suggests its bivalent role in human breast cancer

Breast cancer is the most common cancer in women, and the leading cause of cancer death in women worldwide. SIRT1 (silent mating type information regulation 2 homolog) 1 is a class-III histone deacetylase involved in apoptosis regulation, DNA repair and tumorigenesis. However, its role in breast carcinoma remains controversial, as both tumor-suppressive and tumor-promoting functions have been reported. Also, there are very few reports available where expression of SIRT1 is comprehensively analyzed in breast tumors classified by molecular subtype. Here, using a cohort of 50 human breast tumors and their matched normal tissues, we investigated SIRT1 expression levels in the 5 molecular subtypes of breast cancer according to the St Gallen classification (2013). Tumors and their corresponding normal tissue samples were collected from all patients, and SIRT1 mRNA and protein expression levels were then examined by real-time quantitative polymerase chain reaction and immunoblotting, respectively. After statistical analysis, the results showed a dual expression profile of SIRT1 in human breast carcinoma, with significant overexpression in luminal and HER2-enriched subtypes and significantly reduced expression in the triple-negative subtype. We also found an inverse correlation between SIRT1 expression and breast cancer aggressivity. These novel findings suggest that SIRT1 plays a dual role in breast tumors depending on its expression rate and the molecular subtype of the cancer. Our data also point to a potential role for SIRT1 as a prognostic biomarker in breast cancer.