When mutants gain new powers: news from the mutant p53 field

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.

Differentiated pre-adipocytes promote proliferation, migration and epithelial-mesenchymal transition in breast cancer cells of different p53 status

Breast cancer progression and metastasis are associated with stromal cells in the tumor microenvironment. Adipocytes are the most abundant cells surrounding breast stromal tissue, promote tumor progression through the induction of Epithelial-to-Mesenchymal Transition (EMT) which is negatively regulated by tumor suppressor protein p53. In this study aimed to investigate the role of p53 in the progression of breast cancer after mature adipocyte-conditioned medium (CM) application. The proliferative effect of CM obtained from differentiated pre-adipocytes were assessed by MTS assay. 20% CM increased cell proliferation in breast cancer cells, T-47D (mutant p53) and MCF-7 (wild-type p53). The migration and invasion capacity were evaluated by scratch and transwell assays, respectively. CM significantly enhanced migration and invasion capacity in T-47D compared to MCF-7. Gene and protein expressions were detected by qRT-PCR and Western Blot analysis, respectively. CM markedly increased expression levels of Cyclin D1, PI3K, MMP9, Snail and Twist in T-47D compared to MCF-7. However, CM did not change E-Cadherin level in T-47D while downregulated in MCF-7 cells. Also, the protein levels of NFκB p65, p-Akt, Snail, and Vimentin were upregulated in both cells. Overall, the findings highlight how the p53 status affects mature adipocyte-mediated proliferation, migration, and aggressive behavior of breast cancer cell lines. Targeting the tumor microenvironment may represent a promising approach for preventing breast cancer progression and metastasis.

Suppression of HSF1 activity by wildtype p53 creates a driving force for p53 loss-of-heterozygosity

The vast majority of human tumors with p53 mutations undergo loss of the remaining wildtype p53 allele (loss-of-heterozygosity, p53LOH). p53LOH has watershed significance in promoting tumor progression. However, driving forces for p53LOH are poorly understood. Here we identify the repressive WTp53-HSF1 axis as one driver of p53LOH. We find that the WTp53 allele in AOM/DSS chemically-induced colorectal tumors (CRC) of p53R248Q/+ mice retains partial activity and represses heat-shock factor 1 (HSF1), the master regulator of the proteotoxic stress response (HSR) that is ubiquitously activated in cancer. HSR is critical for stabilizing oncogenic proteins including mutp53. WTp53-retaining CRC tumors, tumor-derived organoids and human CRC cells all suppress the tumor-promoting HSF1 program. Mechanistically, retained WTp53 activates CDKN1A/p21, causing cell cycle inhibition and suppression of E2F target MLK3. MLK3 links cell cycle with the MAPK stress pathway to activate the HSR response. In p53R248Q/+ tumors WTp53 activation by constitutive stress represses MLK3, thereby weakening the MAPK-HSF1 response necessary for tumor survival. This creates selection pressure for p53LOH which eliminates the repressive WTp53-MAPK-HSF1 axis and unleashes tumor-promoting HSF1 functions, inducing mutp53 stabilization enabling invasion.

Apoptotic effect of chromanone derivative, hyrtiosone A from marine demosponge Hyrtios erectus in hepatocellular carcinoma HepG2 cells

The tumor suppressor proteins p53 and p27 exhibited a significant role in the survival of cells and regulation of cellular division and growth. In majority of the human tumors, particularly in hepatocellular carcinoma, these proteins are inactivated by mutation or deletion, and are considered to predict the pathophysiology related to liver cancer. The present study evaluated the activation of the p53 and p27 pathways as a useful therapeutic tool to attenuate hepatocellular carcinoma. Three undescribed homologous chromanone derivatives, hyrtiosones A-C were isolated from the organic extract of marine demosponge Hyrtios erectus (family Thorectidae). Preliminary bioactivity assessments found that hyrtiosone A exhibited prospective anti-inflammatory (IC₅₀ 1.02-1.86 mM) and antioxidant (IC₅₀ 0.74-0.83 mM) properties. Molecular docking analysis of the hyrtiosones using p53-murine double minute complex revealed lesser docking parameters for hyrtiosone A (binding energy -11.12 kcal mol^-1, docking score -12.18 kcal mol^-1) thereby attributing its greater bioactivity. Hyrtiosone A was furthermore analyzed for in vitro anticancer activity in hepatocellular carcinoma HepG2 cells. Morphological assessment of hyrtiosone A treated HepG2 cell line by acridine orange/ethidium bromide fluorescence staining revealed greater number of apoptotic cells, and was found to be comparable with the cells treated with the standard doxorubicin. Further the Annexin V-fluorescein isothiocyanate assay of hyrtiosone A treated HepG2 cell line by flow cytometry displayed greater number of early apoptotic cells (51.24%) than that exhibited by the standard (21.45%). Cell cycle distribution analysis showed that hyrtiosone A arrested the S and G2/M phase of cell cycle and upregulate the gene expression of p53 and p27 in hepatocellular carcinoma HepG2 cells.

Targeting Stress-Response Pathways and Therapeutic Resistance in Head and Neck Cancer

Head and neck cancer is the sixth leading cancer worldwide; head and neck squamous cell carcinoma (HNSCC) accounts for more than 90% of incident cases. In the US, cases of HNSCC associated with human papillomavirus (HPV) have been growing in proportion amongst a younger demographic with superior outcomes to the same treatments, relative to cases associated with tobacco. Yet failures to improve the long-term prognosis of advanced HNSCC over the last three decades persist in part due to intrinsic and acquired mechanisms of resistance. Deregulation of the pathways to respond to stress, such as apoptosis and autophagy, often contributes to drug resistance and tumor progression. Here we review the stress-response pathways in drug response and resistance in HNSCC to explore strategies to overcome these resistance mechanisms. We focus on the mechanisms of resistance to current standard cares, such as chemotherapy (i.e., cisplatin), radiation, and cetuximab. Then, we discuss the strategies to overcome these resistances, including novel combinations and immunotherapy.

Solution structure of the anticancer p28 peptide in biomimetic medium

The p28 peptide derived from Pseudomonas aeruginosa azurin shows an anticancer activity after binding to p53 protein and is currently in Phase I of clinical trials. We have studied its structure in water and in a biomimetic media and show that the peptide is unstructured in water but when studied in a biomimetic medium assumes a structure very similar to the one observed in azurin, suggesting a high propensity of this peptide to maintain this secondary structure. Analysis of p28 sequences from different bacterial species indicates conservation of the secondary structure despite amino acid replacement in different positions, suggesting that others, similar peptides could be tested for binding to p53.

Towards a Better Understanding of the Relationships between Galectin-7, p53 and MMP-9 during Cancer Progression

It has been almost 25 years since the discovery of galectin-7. This member of the galectin family has attracted interest from many working in the cancer field given its highly restricted expression profile in epithelial cells and the fact that cancers of epithelial origin (carcinoma) are among the most frequent and deadly cancer subtypes. Initially described as a p53-induced gene and associated with apoptosis, galectin-7 is now recognized as having a protumorigenic role in many cancer types. Several studies have indeed shown that galectin-7 is associated with aggressive behavior of cancer cells and induces expression of MMP-9, a member of the matrix metalloproteinases (MMP) family known to confer invasive behavior to cancer cells. It is therefore not surprising that many studies have examined its relationships with p53 and MMP-9. However, the relationships between galectin-7 and p53 and MMP-9 are not always clear. This is largely because p53 is often mutated in cancer cells and such mutations drastically change its functions and, consequently, its association with galectin-7. In this review, we discuss the functional relationships between galectin-7, p53 and MMP-9 and reconcile some apparently contradictory observations. A better understanding of these relationships will help to develop a working hypothesis and model that will provide the basis for further research in the hope of establishing a new paradigm for tackling the role of galectin-7 in cancer.

The Gain-of-Function p53 R248W Mutant Promotes Migration by STAT3 Deregulation in Human Pancreatic Cancer Cells

Missense p53 mutations (mutp53) occur in approx. 70% of pancreatic ductal adenocarcinomas (PDAC). Typically, mutp53 proteins are aberrantly stabilized by Hsp90/Hsp70/Hsp40 chaperone complexes. Notably, stabilization is a precondition for specific mutp53 alleles to acquire powerful neomorphic oncogenic gain-of-functions (GOFs) that promote tumor progression in solid cancers mainly by increasing invasion and metastasis. In colorectal cancer (CRC), we recently established that the common hotspot mutants mutp53^R248Q and mutp53^R248W exert GOF activities by constitutively binding to and hyperactivating STAT3. This results in increased proliferation and invasion in an autochthonous CRC mouse model and correlates with poor survival in patients. Comparing a panel of p53 missense mutations in a series of homozygous human PDAC cell lines, we show here that, similar to CRC, the mutp53^R248W protein again undergoes a strong Hsp90-mediated stabilization and selectively promotes migration. Highly stabilized mutp53 is degradable by the Hsp90 inhibitors Onalespib and Ganetespib, and correlates with growth suppression, possibly suggesting therapeutic vulnerabilities to target GOF mutp53 proteins in PDAC. In response to mutp53 depletion, only mutp53^R248W harboring PDAC cells show STAT3 de-phosphorylation and reduced migration, again suggesting an allele-specific GOF in this cancer entity, similar to CRC. Moreover, mutp53^R248W also exhibits the strongest constitutive complex formation with phosphorylated STAT3. The selective mutp53^R248W GOF signals through enhancing the STAT3 axis, which was confirmed since targeting STAT3 by knockdown or pharmacological inhibition phenocopied mutp53 depletion and reduced cell viability and migration preferentially in mutp53^R248W-containing PDAC cells. Our results confirm that mutp53 GOF activities are allele specific and can span across tumor entities.

Direct evidence of cellular transformation by prion-like p53 amyloid infection

Tumor suppressor p53 mutations are associated with more than 50% of cancers. Aggregation and amyloid formation of p53 is also implicated in cancer pathogenesis, but direct evidence for aggregated p53 amyloids acting as an oncogene is lacking. Here, we conclusively demonstrate that wild-type p53 amyloid formation imparts oncogenic properties to non-cancerous cells. p53 amyloid aggregates were transferred through cell generations, contributing to enhanced survival, apoptotic resistance with increased proliferation and migration. The tumorigenic potential of p53 amyloid-transformed cells was further confirmed in mouse xenografts, wherein the tumors showed p53 amyloids. p53 disaggregation rescued the cellular transformation and inhibited tumor development in mice. We propose that wild-type p53 amyloid formation contributes to tumorigenesis and can be a potential target for therapeutic intervention. This article has an associated First Person interview with the first author of the paper.

SLC45A4 promotes glycolysis and prevents AMPK/ULK1-induced autophagy in TP53 mutant pancreatic ductal adenocarcinoma

Background

Somatic mutations of the TP53 gene occur frequently in pancreatic ductal adenocarcinoma (PDA). Solute carrier family 45 member A4 (SLC45A4) is a H⁺‐dependent sugar cotransporter. The role of SLC45A4 in PDA, especially in TP53 mutant PDA, remains poorly understood.

Methods

We explored the TCGA datasets to identify oncogenes in TP53 mutant PDA. MTS [3‐(4,5‐dimethylthiazol‐2‐yl)‐5‐(3‐carboxymethoxyphenyl)‐2‐(4‐sulfophenyl)‐2H‐tetrazolium], colony formation and 5‐ethynyl‐2′‐deoxyuridine (Edu) assays were performed to investigate the function of SLC45A4 in vitro. Glucose consumption, lactate production and ATP production were detected to evaluate glucose utilization. Extracellular acidification rate and oxygen consumption rate assays were used to evaluate glycolysis and oxidative phosphorylation. The subcutaneous xenotransplantation models were conducted to explore the function of SLC45A4 in vivo. RNA‐sequencing and gene set enrichment analysis were employed to explore the biological alteration caused by SLC45A4 knockdown. Western blotting was performed to evaluate the activation of glycolysis, as well as the AMPK pathway and autophagy.

Results

SLC45A4 was overexpressed in PDA for which the expression was significantly higher in TP53 mutant PDA than that in wild‐type PDA tissues. Moreover, high level of SLC45A4 expression was tightly associated with poor clinical outcomes in PDA patients. Silencing SLC45A4 inhibited proliferation in TP53 mutant PDA cells. Knockdown of SLC45A4 reduced glucose uptake and ATP production, which led to activation of autophagy via AMPK/ULK1 pathway. Deleting SLC45A4 in TP53 mutant HPAF‐II cells inhibited the growth of xenografts in nude mice.

Conclusions

The present study found that SLC45A4 prevents autophagy via AMPK/ULK1 axis in TP53 mutant PDA, which may be a promising biomarker and therapeutic target in TP53 mutant PDA.

Mutant p53 oncogenicity: dominant-negative or gain-of-function?

The p53 protein is mutated in about 50% of human cancers. Aside from losing its tumor-suppressive activities, mutant p53 may acquire pro-oncogenic activity, which is facilitated by two underlying mechanisms. The first mechanism is the inhibition of co-expressed wild-type p53 (WTp53) activity, dubbed the dominant-negative effect (DNE). The second mechanism is a neomorphic pro-oncogenic activity that does not involve the inhibition of WTp53, termed gain-of-function (GOF). Throughout the years, both mechanisms were demonstrated in a plethora of in vitro and in vivo models. However, whether both account for protumorigenic activities of mutant p53 and in which contexts is still a matter of ongoing debate. Here, we discuss evidence for both DNE and GOF in a variety of models. These models suggest that both GOF and DNE can be relevant, but are highly dependent on the specific mutation type, genetic and cellular context and even the phenotype that is being assessed. In addition, we discuss how mutant and WTp53 might not exist as two separate entities, but rather as a continuum that may involve a balance between the two forms in the same cells, which could be tilted by various factors and drugs. Further elucidation of the factors that dictate the balance between the WT and mutant p53 states, as well as the factors that govern the impact of DNE and GOF in different cancer types, may lead to the development of more effective treatment regimens for cancer patients.

Rely on Each Other: DNA Binding Cooperativity Shapes p53 Functions in Tumor Suppression and Cancer Therapy

p53 is a tumor suppressor that is mutated in half of all cancers. The high clinical relevance has made p53 a model transcription factor for delineating general mechanisms of transcriptional regulation. p53 forms tetramers that bind DNA in a highly cooperative manner. The DNA binding cooperativity of p53 has been studied by structural and molecular biologists as well as clinical oncologists. These experiments have revealed the structural basis for cooperative DNA binding and its impact on sequence specificity and target gene spectrum. Cooperativity was found to be critical for the control of p53-mediated cell fate decisions and tumor suppression. Importantly, an estimated number of 34,000 cancer patients per year world-wide have mutations of the amino acids mediating cooperativity, and knock-in mouse models have confirmed such mutations to be tumorigenic. While p53 cancer mutations are classically subdivided into "contact" and "structural" mutations, "cooperativity" mutations form a mechanistically distinct third class that affect the quaternary structure but leave DNA contacting residues and the three-dimensional folding of the DNA-binding domain intact. In this review we discuss the concept of DNA binding cooperativity and highlight the unique nature of cooperativity mutations and their clinical implications for cancer therapy.

TP53 abnormalities correlate with immune infiltration and associate with response to flotetuzumab immunotherapy in AML

Somatic TP53 mutations and 17p deletions with genomic loss of TP53 occur in 37% to 46% of acute myeloid leukemia (AML) with adverse-risk cytogenetics and correlate with primary induction failure, high risk of relapse, and dismal prognosis. Herein, we aimed to characterize the immune landscape of TP53-mutated AML and determine whether TP53 abnormalities identify a patient subgroup that may benefit from immunotherapy with flotetuzumab, an investigational CD123 × CD3 bispecific dual-affinity retargeting antibody (DART) molecule. The NanoString PanCancer IO360 assay was used to profile 64 diagnostic bone marrow (BM) samples from patients with TP53-mutated (n = 42) and TP53-wild-type (TP53-WT) AML (n = 22) and 45 BM samples from patients who received flotetuzumab for relapsed/refractory (R/R) AML (15 cases with TP53 mutations and/or 17p deletion). The comparison between TP53-mutated and TP53-WT primary BM samples showed higher expression of IFNG, FOXP3, immune checkpoints, markers of immune senescence, and phosphatidylinositol 3-kinase-Akt and NF-κB signaling intermediates in the former cohort and allowed the discovery of a 34-gene immune classifier prognostic for survival in independent validation series. Finally, 7 out of 15 patients (47%) with R/R AML and TP53 abnormalities showed complete responses to flotetuzumab (<5% BM blasts) on the CP-MGD006-01 clinical trial (NCT #02152956) and had significantly higher tumor inflammation signature, FOXP3, CD8, inflammatory chemokine, and PD1 gene expression scores at baseline compared with nonresponders. Patients with TP53 abnormalities who achieved a complete response experienced prolonged survival (median, 10.3 months; range, 3.3-21.3 months). These results encourage further study of flotetuzumab immunotherapy in patients with TP53-mutated AML.

Human GATA2 mutations and hematologic disease: how many paths to pathogenesis?

The surge of human genetic information, enabled by increasingly facile and economically feasible genomic technologies, has accelerated discoveries on the relationship of germline genetic variation to hematologic diseases. For example, germline variation in GATA2, encoding a vital transcriptional regulator of multilineage hematopoiesis, creates a predisposition to bone marrow failure and acute myeloid leukemia termed GATA2 deficiency syndrome. More than 300 GATA2 variants representing missense, truncating, and noncoding enhancer mutations have been documented. Although these variants can diminish GATA2 expression and/or function, the functional ramifications of many variants are unknown. Studies using genetic rescue and knockin mouse systems have established that GATA2 mutations differentially affect molecular processes in distinct target genes and within a single target cell. Considering that target genes for a transcription factor can differ in sensitivity to altered levels of the factor, and transcriptional mechanisms are often cell type specific, the context-dependent consequences of GATA2 mutations in experimental systems portend the complex phenotypes and interindividual variation of GATA2 deficiency syndrome. This review documents GATA2 human genetics and the state of efforts to traverse from physiological insights to pathogenic mechanisms.

Small molecule Y-320 stimulates ribosome biogenesis, protein synthesis, and aminoglycoside-induced premature termination codon readthrough

Premature termination codons (PTC) cause over 10% of genetic disease cases. Some aminoglycosides that bind to the ribosome decoding center can induce PTC readthrough and restore low levels of full-length functional proteins. However, concomitant inhibition of protein synthesis limits the extent of PTC readthrough that can be achieved by aminoglycosides like G418. Using a cell-based screen, we identified a small molecule, the phenylpyrazoleanilide Y-320, that potently enhances TP53, DMD, and COL17A1 PTC readthrough by G418. Unexpectedly, Y-320 increased cellular protein levels and protein synthesis, measured by SYPRO Ruby protein staining and puromycin labeling, as well as ribosome biogenesis measured using antibodies to rRNA and ribosomal protein S6. Y-320 did not increase the rate of translation elongation and it exerted its effects independently of mTOR signaling. At the single cell level, exposure to Y-320 and G418 increased ribosome content and protein synthesis which correlated strongly with PTC readthrough. As a single agent, Y-320 did not affect translation fidelity measured using a luciferase reporter gene but it enhanced misincorporation by G418. RNA-seq data showed that Y-320 up-regulated the expression of CXC chemokines CXCL10, CXCL8, CXCL2, CXCL11, CXCL3, CXCL1, and CXCL16. Several of these chemokines exert their cellular effects through the receptor CXCR2 and the CXCR2 antagonist SB225002 reduced cellular protein levels and PTC readthrough in cells exposed to Y-320 and G418. These data show that the self-limiting nature of PTC readthrough by G418 can be compensated by Y-320, a potent enhancer of PTC readthrough that increases ribosome biogenesis and protein synthesis. They also support a model whereby increased PTC readthrough is enabled by increased protein synthesis mediated by an autocrine chemokine signaling pathway. The findings also raise the possibility that inflammatory processes affect cellular propensity to readthrough agents and that immunomodulatory drugs like Y-320 might find application in PTC readthrough therapy.

Mutant p53 Drives Cancer Metastasis via RCP-Mediated Hsp90α Secretion

Mutant p53 (mutp53) loses its tumor suppressor properties but gains oncogenic functions of driving malignancy. However, it remains largely unknown how mutp53 drives cancer metastasis. Here, we show that wild-type p53 (WTp53) suppresses the secretion of heat shock protein 90-alpha (Hsp90α), whereas mutp53 enhances Hsp90α vesicular trafficking and exosome-mediated secretion. Long-term delivery of an antibody that blocks extracellular Hsp90α (eHsp90α) function extends the survival of p53^-/- mice and attenuates the invasiveness of p53 mutant tumors. Furthermore, mass spectrometry and functional analysis identified a critical role for Rab coupling protein (RCP) in mutp53-induced Hsp90α secretion. RCP knockdown decreases eHsp90α levels and inhibits malignant progression. Notably, recombinant Hsp90α re-introduction markedly rescues the impaired migration and invasion abilities caused by RCP depletion. Taken together, these findings elucidate the molecular mechanisms by which mutp53 executes oncogenic activities via its downstream RCP-mediated Hsp90α secretion and a strategy to treat human cancers expressing mutp53 proteins.

The roles and regulation of MDM2 and MDMX: it is not just about p53

In this review, Klein et al. discuss the p53-independent roles of MDM2 and MDMX. First, they review the structural and functional features of MDM2 and MDMX proteins separately and together that could be relevant to their p53-independent activities. Following this, they summarize how these two proteins are regulated and how they can function in cells that lack p53.

Most well studied as proteins that restrain the p53 tumor suppressor protein, MDM2 and MDMX have rich lives outside of their relationship to p53. There is much to learn about how these two proteins are regulated and how they can function in cells that lack p53. Regulation of MDM2 and MDMX, which takes place at the level of transcription, post-transcription, and protein modification, can be very intricate and is context-dependent. Equally complex are the myriad roles that these two proteins play in cells that lack wild-type p53; while many of these independent outcomes are consistent with oncogenic transformation, in some settings their functions could also be tumor suppressive. Since numerous small molecules that affect MDM2 and MDMX have been developed for therapeutic outcomes, most if not all designed to prevent their restraint of p53, it will be essential to understand how these diverse molecules might affect the p53-independent activities of MDM2 and MDMX.

Myelodysplasia Syndrome, Clonal Hematopoiesis and Cardiovascular Disease

Simple Summary

The development of blood cancers is a complex process that involves the acquisition of specific blood disorders that precede cancer. These blood disorders are often driven by the accumulation of genetic abnormalities, which are discussed in this review. Likewise, predicting the rate of progression of these diseases is difficult, but it appears to be linked to which specific gene mutations are present in blood cells. In this review, we discuss a variety of genetic abnormalities that drive blood cancer, conditions that precede clinical symptoms of blood cancer, and how alterations in these genes change blood cell function. Additionally, we discuss the novel links between blood cancer development and heart disease.

Abstract

The development of myelodysplasia syndromes (MDS) is multiphasic and can be driven by a plethora of genetic mutations and/or abnormalities. MDS is characterized by a hematopoietic differentiation block, evidenced by increased immature hematopoietic cells, termed blast cells and decreased mature circulating leukocytes in at least one lineage (i.e., cytopenia). Clonal hematopoiesis of indeterminate potential (CHIP) is a recently described phenomenon preceding MDS development that is driven by somatic mutations in hemopoietic stem cells (HSCs). These mutant HSCs have a competitive advantage over healthy cells, resulting in an expansion of these clonal mutated leukocytes. In this review, we discuss the multiphasic development of MDS, the common mutations found in both MDS and CHIP, how a loss-of-function in these CHIP-related genes can alter HSC function and leukocyte development and the potential disease outcomes that can occur with dysfunctional HSCs. In particular, we discuss the novel connections between MDS development and cardiovascular disease.

High-fidelity detection of DNA combining the CRISPR/Cas9 system and hairpin probe

Methods that enable specific and sensitive detection of DNA are greatly required for high-fidelity sequence measurement and single-nucleotide variations (SNVs) genotyping. The CRISPR (clustered regularly interspaced short palindromic repeats)/Cas systems have provided revolutionary tools for detecting nucleic acids. However, most of the current CRISPR/Cas-based DNA biosensing platforms suffer from inherent off-target effects of Cas proteins and require pre-amplification processes, which compromise the analytical fidelity. In this work, a CRISPR/Cas9-triggered hairpin probe-mediated biosensing method (namely CHP) was used to directly read the original DNA sequences, while effectively neutralizing the off-target effect and achieving high sensitivity. This technique can quantify DNA targets with a limit of detection (LOD) at the attomole level and identify SNVs with allelic fractions as low as 0.01%~0.1%. Moreover, we show that the CHP system is applicable in detecting mutations in serum samples without DNA isolation steps. Collectively, the CHP system is a sensitive and high-fidelity platform, which promises a great potential for providing robust tool for DNA sequence analysis and SNVs genotyping.

The G199X and V157fs mutations in the TP53 gene promote malignancy in serous ovarian cancer: an analysis using whole-exome sequencing

Background

The carcinogenic mechanisms underlying serous ovarian cancer are not fully understood.

Methods

Whole-exome sequencing and targeted sequencing were performed in ovarian cancer samples to identify novel molecular markers involved in the process of cell malignancy in ovarian cancer. In vitro experiments, the oncogenic roles such as cell proliferation, migration and invasion of TP53 G199X and V157fs mutations were investigated deeply.

Results

The present study identified the G199X and V157fs point mutations in the tumor protein P53 gene (TP53). The rate of TP53 mutation was 59.2% in a cohort of 76 ovarian cancer patients, compared with 9.0% in a cohort of 156 healthy women. Kaplan-Meier analysis showed that patients with a TP53 mutation had a lower 5-year overall survival (OS) rate compared with patients harboring wild type TP53. In vitro experiments in an ovarian cancer cell line demonstrated that the G199X and V157fs mutants inhibited P53 protein expression, enhanced proliferation, promoted migration and increased invasion.

Conclusions

This study identified two novel markers, TP53 G199X and V157fs mutations in TP53. Functional assays indicated that these mutations enhanced the malignant phenotype in ovarian cancer cells. These novel markers will assist in the diagnosis of ovarian tumors and represent potential targets for the treatment of TP53 mutant ovarian cancers.

Detection of Post-translationally Modified p53 by Western Blotting

The p53 tumor suppressor has a central role in many key cellular processes including the DNA damage response, aging, stem cell differentiation, and fertility. p53 undergoes extensive regulatory post-translational modification through events such as phosphorylation, acetylation, methylation, and ubiquitylation. Here, we describe western blotting-based methodology for the detection and relative quantification of individual phosphorylation events in p53. While we focus on well-established N-terminal modifications for the purpose of illustration, this approach can be used to investigate other post-translational modifications of the protein, drawing upon a broad range of commercially available modification-specific antibodies.

Cooperation between oncogenic Ras and wild-type p53 stimulates STAT non-cell autonomously to promote tumor radioresistance

Oncogenic RAS mutations are associated with tumor resistance to radiation therapy. Cell-cell interactions in the tumor microenvironment (TME) profoundly influence therapy outcomes. However, the nature of these interactions and their role in Ras tumor radioresistance remain unclear. Here we use Drosophila oncogenic Ras tissues and human Ras cancer cell radiation models to address these questions. We discover that cellular response to genotoxic stress cooperates with oncogenic Ras to activate JAK/STAT non-cell autonomously in the TME. Specifically, p53 is heterogeneously activated in Ras tumor tissues in response to irradiation. This mosaicism allows high p53-expressing Ras clones to stimulate JAK/STAT cytokines, which activate JAK/STAT in the nearby low p53-expressing surviving Ras clones, leading to robust tumor re-establishment. Blocking any part of this cell-cell communication loop re-sensitizes Ras tumor cells to irradiation. These findings suggest that coupling STAT inhibitors to radiotherapy might improve clinical outcomes for Ras cancer patients.

Identification and characterization of R2TP in the development of oral squamous cell carcinoma

R2TP is a well-conserved molecular chaperone complex, composed of Pontin, Reptin, RPAP3, and PIH1D, in eukaryotes. Recent studies have suggested an involvement of R2TP in cancer development. However, it remains unclear if it is related to the development of oral squamous cell carcinoma (OSCC), which is the most common type of oral cancer. Here, we identify and investigate the function of R2TP in OSCC development. Immunohistochemical analysis reveals that all of the R2TP components are strongly expressed in normal oral epithelia and OSCC tissues, where actively proliferating cells are abundant. Co-immunoprecipitation assay identifies that R2TP components form a protein complex in OSCC-derived HSC4-cells. Knockdown experiments show that all R2TP components, except for RPAP3, are required for the cell proliferation and migration of HSC-4 cells. Furthermore, we reveal that Pontin contributes to a gain-of-function (GOF) activity of mutp53-R248Q in HSC-4 cells by regulating phosphorylation levels of mutp53 at Ser15 and Ser46. To our knowledge, this study is the first to report the functional involvement of R2TP and its components in the malignant characteristics of OSCC cells.

Aberrant phase separation and cancer

Eukaryotic cells are intracellularly divided into numerous compartments or organelles, which coordinate specific molecules and biological reactions. Membrane-bound organelles are physically separated by lipid bilayers from the surrounding environment. Biomolecular condensates, also referred to membraneless organelles, are micron-scale cellular compartments that lack membranous enclosures but function to concentrate proteins and RNA molecules, and these are involved in diverse processes. Liquid-liquid phase separation (LLPS) driven by multivalent weak macromolecular interactions is a critical principle for the formation of biomolecular condensates, and a multitude of combinations among multivalent interactions may drive liquid-liquid phase transition (LLPT). Dysregulation of LLPS and LLPT leads to aberrant condensate and amyloid formation, which causes many human diseases, including neurodegeneration and cancer. Here, we describe recent findings regarding abnormal forms of biomolecular condensates and aggregation via aberrant LLPS and LLPT of cancer-related proteins in cancer development driven by mutation and fusion of genes. Moreover, we discuss the regulatory mechanisms by which aberrant LLPS and LLPT occur in cancer and the drug candidates targeting these mechanisms. Further understanding of the molecular events regulating how biomolecular condensates and aggregation form in cancer tissue is critical for the development of therapeutic strategies against tumorigenesis.

TP53 Mutations in Acute Myeloid Leukemia: Still a Daunting Challenge?

TP53 is a key tumor suppressor gene with protean functions associated with preservation of genomic balance, including regulation of cellular senescence, apoptotic pathways, metabolism functions, and DNA repair. The vast majority of de novo acute myeloid leukemia (AML) present unaltered TP53 alleles. However, TP53 mutations are frequently detected in AML related to an increased genomic instability, such as therapy‐related (t-AML) or AML with myelodysplasia-related changes. Of note, TP53 mutations are associated with complex cytogenetic abnormalities, advanced age, chemoresistance, and poor outcomes. Recent breakthroughs in AML research and the development of targeted drugs directed at specific mutations have led to an explosion of novel treatments with different mechanisms. However, optimal treatment strategy for patients harboring TP53 mutations remains a critical area of unmet need. In this review, we focus on the incidence and clinical significance of TP53 mutations in de novo and t-AML. The influence of these alterations on response and clinical outcomes as well as the current and future therapeutic perspectives for this hardly treatable setting are discussed.

Mutant p53 as a Regulator and Target of Autophagy

One of the most notoriously altered genes in human cancer is the tumor-suppressor TP53, which is mutated with high frequency in more cancers than any other tumor suppressor gene. Beyond the loss of wild-type p53 functions, mutations in the TP53 gene often lead to the expression of full-length proteins with new malignant properties. Among the defined oncogenic functions of mutant p53 is its effect on cell metabolism and autophagy. Due to the importance of autophagy as a stress adaptive response, it is frequently dysfunctional in human cancers. However, the role of p53 is enigmatic in autophagy regulation. While the complex action of the wild-type p53 on autophagy has extensively been described in literature, in this review, we focus on the conceivable role of distinct mutant p53 proteins in regulating different autophagic pathways and further discuss the available evidence suggesting a possible autophagy stimulatory role of mutant p53. Moreover, we describe the involvement of different autophagic pathways in targeting and degrading mutant p53 proteins, exploring the potential strategies of targeting mutant p53 in cancer by autophagy.

Interplay between HMGA and TP53 in cell cycle control along tumor progression

The high mobility group A (HMGA) proteins are found to be aberrantly expressed in several tumors. Studies (in vitro and in vivo) have shown that HMGA protein overexpression has a causative role in carcinogenesis process. HMGA proteins regulate cell cycle progression through distinct mechanisms which strongly influence its normal dynamics along malignant transformation. Tumor protein p53 (TP53) is the most frequently altered gene in cancer. The loss of its activity is recognized as the fall of a barrier that enables neoplastic transformation. Among the different functions, TP53 signaling pathway is tightly involved in control of cell cycle, with cell cycle arrest being the main biological outcome observed upon p53 activation, which prevents accumulation of damaged DNA, as well as genomic instability. Therefore, the interaction and opposing effects of HMGA and p53 proteins on regulation of cell cycle in normal and tumor cells are discussed in this review. HMGA proteins and p53 may reciprocally regulate the expression and/or activity of each other, leading to the counteraction of their regulation mechanisms at different stages of the cell cycle. The existence of a functional crosstalk between these proteins in the control of cell cycle could open the possibility of targeting HMGA and p53 in combination with other therapeutic strategies, particularly those that target cell cycle regulation, to improve the management and prognosis of cancer patients.

Histone Methyltransferase SETDB1: A Common Denominator of Tumorigenesis with Therapeutic Potential

Epigenetic regulation of gene expression has been ultimately linked to cancer development, with posttranslational histone modifications representing attractive targets for disease monitoring and therapy. Emerging data have demonstrated histone lysine (K) methylation by methyltransferase SETDB1 as a common denominator of gene regulation in several cancer types. SETDB1 reversibly catalyzes the di- and trimethylation of histone 3 (H3) K9 in euchromatic regions of chromosomes, inhibiting gene transcription within these regions and promoting a switch from euchromatic to heterochromatic states. Recent studies have implicated aberrant SETDB1 activity in the development of various types of cancers, including brain, head and neck, lung, breast, gastrointestinal, ovarian, endometrial and prostate cancer, mesothelioma, melanoma, leukemias, and osteosarcoma. Although its role has not been fully elucidated in every case, most data point toward a pro-oncogenic potential of SETDB1 via the downregulation of critical tumor-suppressive genes. Less commonly, however, SETDB1 can also acquire a tumor-suppressive role, depending on cancer type and stage. Here we provide an updated overview of the cellular and molecular effects underlying SETDB1 activity in cancer development and progression along with current targeting strategies in different cancer types, with promising effects either as a standalone therapy or in conjunction with other therapeutic agents.

A Phenomic Perspective on Factors Influencing Breast Cancer Treatment: Integrating Aging and Lifestyle in Blood and Tissue Biomarker Profiling

Breast cancer is the most common malignancy among women worldwide. Over the last four decades, diagnostic and therapeutic procedures have improved substantially, giving patients with localized disease a better chance of cure, and those with more advanced cancer, longer periods of disease control and survival. However, understanding and managing heterogeneity in the clinical response exhibited by patients remains a challenge. For some treatments, biomarkers are available to inform therapeutic options, assess pathological response and predict clinical outcomes. Nevertheless, some measurements are not employed universally and lack sensitivity and specificity, which might be influenced by tissue-specific alterations associated with aging and lifestyle. The first part of this article summarizes available and emerging biomarkers for clinical use, such as measurements that can be made in tumor biopsies or blood samples, including so-called liquid biopsies. The second part of this article outlines underappreciated factors that could influence the interpretation of these clinical measurements and affect treatment outcomes. For example, it has been shown that both adiposity and physical activity can modify the characteristics of tumors and surrounding tissues. In addition, evidence shows that inflammaging and immunosenescence interact with treatment and clinical outcomes and could be considered prognostic and predictive factors independently. In summary, changes to blood and tissues that reflect aging and patient characteristics, including lifestyle, are not commonly considered clinically or in research, either for practical reasons or because the supporting evidence base is developing. Thus, an aim of this article is to encourage an integrative phenomic approach in oncology research and clinical management.

Telomeres: history, health, and hallmarks of aging

The escalating social and economic burden of an aging world population has placed aging research at center stage. The hallmarks of aging comprise diverse molecular mechanisms and cellular systems that are interrelated and act in concert to drive the aging process. Here, through the lens of telomere biology, we examine how telomere dysfunction may amplify or drive molecular biological processes underlying each hallmark of aging and contribute to development of age-related diseases such as neurodegeneration and cancer. The intimate link of telomeres to aging hallmarks informs preventive and therapeutic interventions designed to attenuate aging itself and reduce the incidence of age-associated diseases.

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.

p53 immunohistochemistry discriminates between pure erythroid leukemia and reactive erythroid hyperplasia

Pure erythroid leukemia (PEL) is a rare, aggressive subtype of acute myeloid leukemia with a poor prognosis. The diagnosis of PEL is often medically urgent, quite challenging, and is typically a diagnosis of exclusion requiring meticulous distinction from non-neoplastic erythroid proliferations, particularly florid erythroid hyperplasia/regeneration. Given the frequency of TP53 mutations in the molecular signature of PEL, we hypothesize that differential p53 expression by immunohistochemistry (IHC) may be useful in distinguishing PEL versus non-neoplastic erythroid conditions. We performed p53 IHC on 5 normal bone marrow, 46 reactive erythroid proliferations, and 27 PEL cases. We assessed the positivity and intensity of nuclear staining in pronormoblasts and basophilic normoblasts using a 0–3+ scale with 0 being absent (with internal positive controls) and 3 being strong nuclear positivity. A total of 26/27 PEL cases showed strong, uniform, diffuse intense staining by the neoplastic pronormoblasts versus 0/5 and 0/46 normal and reactive controls, respectively. The control cases show various staining patterns ranging from 0 to 3+ in scattered erythroid precursor cells. Uniform, strong p53 positivity is unique to PEL and discriminates this entity from a benign erythroid mimic. Thus, p53 IHC may be a useful marker in urgent medical cases to assist in the confirmation of a malignant PEL diagnosis while awaiting the results of additional ancillary studies such as cytogenetics.

Identification of a druggable protein-protein interaction site between mutant p53 and its stabilizing chaperone DNAJA1

The TP53 gene is the most frequently mutated gene in human cancers, and the majority of TP53 mutations are missense mutations. As a result, these mutant p53 (mutp53) either directly lose wildtype p53 (wtp53) tumor suppressor function or exhibit a dominant negative effect over wtp53. In addition, some mutp53 have acquired new oncogenic function (gain of function). Therefore, targeting mutp53 for its degradation may serve as a promising strategy for cancer prevention and therapy. Based on our previous finding that farnesylated DNAJA1 is a crucial chaperone in maintaining mutp53 stabilization, and by using an in silico approach, we built 3D homology models of human DNAJA1 and mutp53R175H proteins, identified the interacting pocket in the DNAJA1-mutp53R175H complex, and found one critical druggable small molecule binding site in the DNAJA1 glycine/phenylalanine-rich region. We confirmed that the interacting pocket in the DNAJA1-mutp53R175H complex was crucial for stabilizing mutp53R175H using a site-directed mutagenesis approach. We further screened a drug-like library to identify a promising small molecule hit (GY1-22) against the interacting pocket in the DNAJA1-mutp53R175H complex. The GY1-22 compound displayed an effective activity against the DNAJA1-mutp53R175H complex. Treatment with GY1-22 significantly reduced mutp53 protein levels, enhanced Waf1p21 expression, suppressed cyclin D1 expression, and inhibited mutp53-driven pancreatic cancer growth both in vitro and in vivo. Together, our results indicate that the interacting pocket in the DNAJA1-mutp53R175H complex is critical for mutp53's stability and oncogenic function, and DNAJA1 is a robust therapeutic target for developing the efficient small molecule inhibitors against oncogenic mutp53.

Investigating Conformational Dynamics and Allostery in the p53 DNA-Binding Domain Using Molecular Simulations

The p53 tumor suppressor is a multifaceted context-dependent protein, which is involved in multiple cellular pathways, with the ability to either keep the cells alive or to kill them through mechanisms such as apoptosis. To complicate this picture, cancer cells that express mutant p53 becomes addicted to the mutant activity, so that the mutant variant features a myriad of gain-of-function activities, opening different venues for therapy. This makes essential to think outside the box and apply new approaches to the study of p53 structure-(mis)function relationship to find new critical components of its pathway or to understand how known parts are interconnected, compete, or cooperate. In this context, I will here illustrate how to integrate different computational methods to the identification of possible allosteric effects transmitted from the DNA binding interface of p53 to regions for cofactor recruitment. The protocol can be extended to any other cases of study. Indeed, it does not necessarily apply only to the study of DNA-induced effects, but more broadly to the investigation of long-range effects induced by a biological partner that binds to a biomolecule of interest.

Tumor Suppressors Having Oncogenic Functions: The Double Agents

Cancer progression involves multiple genetic and epigenetic events, which involve gain-of-functions of oncogenes and loss-of-functions of tumor suppressor genes. Classical tumor suppressor genes are recessive in nature, anti-proliferative, and frequently found inactivated or mutated in cancers. However, extensive research over the last few years have elucidated that certain tumor suppressor genes do not conform to these standard definitions and might act as “double agents”, playing contrasting roles in vivo in cells, where either due to haploinsufficiency, epigenetic hypermethylation, or due to involvement with multiple genetic and oncogenic events, they play an enhanced proliferative role and facilitate the pathogenesis of cancer. This review discusses and highlights some of these exceptions; the genetic events, cellular contexts, and mechanisms by which four important tumor suppressors—pRb, PTEN, FOXO, and PML display their oncogenic potentials and pro-survival traits in cancer.

A TP53-Associated Immune Prognostic Signature for the Prediction of Overall Survival and Therapeutic Responses in Muscle-Invasive Bladder Cancer

Background

TP53 gene mutation is one of the most common mutations in human bladder cancer (BC) and has been implicated in the progression and prognosis of BC.

Methods

RNA sequencing data and TP53 mutation data in different populations and platforms were downloaded from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) database to determine and validate a TP53-associated immune prognostic signature (TIPS) based on differentially expressed immune-related genes (DEIGs) between muscle-invasive bladder cancer (MIBC) patients with and without TP53 mutations.

Results

A total of 99 DEIGs were identified based on TP53 mutation status. TIPS including ORM1, PTHLH, and CTSE were developed and validated to identify high-risk prognostic group who had a poorer prognosis than low-risk prognostic group in TCGA and GEO database. The high-risk prognostic group were characterized by a higher abundance of regulatory T cells, myeloid-derived suppressor cells, and tumor-associated macrophages than the low-risk prognostic group. Moreover, they exhibited a lower abundance of CD56bright NK cells, higher expression of CTLA4, LAG3, PDCD1, TIGIT, and HAVCR2, as well as being more likely to respond to anti–PD-1, and neoadjuvant chemotherapy than the low-risk prognostic group. Based on TIPS and other clinical characteristics, a nomogram was constructed for clinical use.

Conclusion

TIPS derived from TP53 mutation status is a potential prognostic signature or therapeutic target but additional prospective studies are necessary to confirm this potential.

Berberine Inhibits Cell Proliferation by Interfering with Wild-Type and Mutant P53 in Human Glioma Cells

Introduction

Glioma is the most common malignant brain tumor. TP53 is the most common mutant gene in human cancer. Wild-type p53 (wtp53) is a tumor suppressor protein whereas mutant p53 (mutp53) is an oncoprotein that promotes tumor cell proliferation. Our aim was to examine the inhibitory effects of berberine on the proliferation of human glioma cells via regulation of wtp53, mutp53, and their downstream molecules.

Methods

We selected wtp53 cells (U87 cells) and mutp53 cells (U251 cells termed p53 R273H) to examine the inhibitory effects of berberine on human glioma cells. We used the CCK-8 kit to detect the toxic effect of berberine. Flow cytometry was used to detect the effect of berberine. Clone formation test was used to test the inhibitory effect of berberine on the proliferation of glioma cells. Western blot was used to detect the changes of related proteins such as p53, p-p53, p21 and cyclin D1. Lentivirus transduction was used to transduce wild-type p53 into U251 cells to further examine the effect of berberine. The nude mouse subcutaneous tumor model was used to detect the effect of berberine on inhibiting the proliferation of glioma cells in vivo.

Results

Berberine promoted the phosphorylation of wtp53, increased the expression of p21 protein, reduced cyclin D1 content, and caused G1 phase arrest in U87 cells. Berberine also reduced mutp53 content and caused G2 phase arrest in U251 cells with a concurrent decrease in p21, cyclin D1, and cyclin B1 content. Transduction with wtp53 enhanced the effects on cell cycle arrest. Further, berberine significantly inhibited glioma growth in vivo mouse tumor model.

Discussion

Glioma is a group of heterogeneous brain tumors with unique biological and clinical characteristics. Berberine can inhibit glioma cells through a variety of ways. Our research indicated that berberine inhibited the proliferation of glioma cells by interfering with wtp53 and mutp53. This indicates that berberine could be used as a potential drug to treat wild-type and mutant p53 glioma.

Integrative p53, micro-RNA and Cathepsin Protease Co-Regulatory Expression Networks in Cancer

Simple Summary

This article describes an emerging area of significant interest in cancer and cell death and the relationships shared by these through the transcriptional regulation of cathepsin protease genes by micro-RNAs that are connected to p53 activation. While it has been demonstrated that the p53 protein can directly regulate some cathepsin genes and the expression of their upstream regulatory micro-RNAs, very little is known about what input the p53 isoform proteins may have in regulating this relationship. Herein, we draw attention to this important regulatory aspect in the context of describing mechanisms that are being established for the micro-RNA regulation of cathepsin protease genes and their collective use in diagnostic or prognostic assays.

Abstract

As the direct regulatory role of p53 and some of its isoform proteins are becoming established in modulating gene expression in cancer research, another aspect of this mode of gene regulation that has captured significant interest over the years is the mechanistic interplay between p53 and micro-RNA transcriptional regulation. The input of this into modulating gene expression for some of the cathepsin family members has been viewed as carrying noticeable importance based on their biological effects during normal cellular homeostasis and cancer progression. While this area is still in its infancy in relation to general cathepsin gene regulation, we review the current p53-regulated micro-RNAs that are generating significant interest through their regulation of cathepsin proteases, thereby strengthening the link between activated p53 forms and cathepsin gene regulation. Additionally, we extend our understanding of this developing relationship to how such micro-RNAs are being utilized as diagnostic or prognostic tools and highlight their future uses in conjunction with cathepsin gene expression as potential biomarkers within a clinical setting.

Predictive and Prognostic Potential of TP53 in Patients With Advanced Non-Small-Cell Lung Cancer Treated With EGFR-TKI: Analysis of a Phase III Randomized Clinical Trial (CTONG 0901)

BACKGROUND

Mutations in TP53 are commonly found in patients with epidermal growth factor receptor (EGFR) mutant advanced non-small-cell lung cancer (NSCLC). In this study, we determined the predictive and prognostic potential of different subtypes of TP53 using data from a phase III randomized trial (CTONG 0901).

PATIENTS AND METHODS

The trial enrolled 195 patients who had undergone next-generation sequencing of 168 genes before treatment with EGFR tyrosine kinase inhibitors. Mutations in TP53 (exon 4 or 7, other mutations, and wild-type) were analyzed based on the therapeutic response and survival. A Cox proportional hazards model was used to determine the potential of the predictive and prognostic factors.

RESULTS

All 195 patients harbored activating EGFR mutations: the most common concomitant mutations were TP53 (134/195, 68.7%), CTNNB1 (20/195, 10.3%), and RB1 (16/195, 8.2%). The genetic profiles between patient subgroups administered first-line (132, 67.7%) or later-line (63, 32.3%) treatments did not significantly differ. The median progression-free survival in patients with mutations in exon 4 or 7 of TP53, other TP53 mutations, and wild-type TP53 were 9.4, 11.0, and 14.5 months (P = .009), respectively. Overall survival times were 15.8, 20.0, and 26.1 months (P = .004), respectively. Mutations in exon 4 or 7 of TP53 served as independent prognostic factors for progression-free (P = .001) and overall survival (P = .004) in patients.

CONCLUSION

Mutations in exon 4 and/or 7 in TP53 are promising predictive and prognostic indicators in EGFR-mutated NSCLC.

The head and neck cancer genome in the era of immunotherapy

The recent success of immunotherapy in head and neck squamous cell carcinoma (HNSCC) has necessitated a new perspective on the cancer genome. Here we review recent advances in the carcinogenesis and molecular genetics of HNSCC with an eye on their implications for cancer immunity. Newer sequencing technologies have recently facilitated dissection of the complex interaction between the HPV virus, tumor, host factors, and the tumor microenvironment (TME) that help shed light on how the immune system interacts with head and neck malignancies.

Mutant p53 in Cancer Progression and Targeted Therapies

TP53 is the most frequently mutated tumor suppressor gene in human cancer. The majority of mutations of p53 are missense mutations, leading to the expression of the full length p53 mutant proteins. Mutant p53 (Mutp53) proteins not only lose wild-type p53-dependent tumor suppressive functions, but also frequently acquire oncogenic gain-of-functions (GOF) that promote tumorigenesis. In this review, we summarize the recent advances in our understanding of the oncogenic GOF of mutp53 and the potential therapies targeting mutp53 in human cancers. In particular, we discuss the promising drugs that are currently under clinical trials as well as the emerging therapeutic strategies, including CRISPR/Cas9 based genome edition of mutant TP53 allele, small peptide mediated restoration of wild-type p53 function, and immunotherapies that directly eliminate mutp53 expressing tumor cells.

LINC00460-miR-149-5p/miR-150-5p-Mutant p53 Feedback Loop Promotes Oxaliplatin Resistance in Colorectal Cancer

Oxaliplatin resistance is a major challenge in the clinical treatment for advanced colorectal cancer (CRC). Long non-coding RNAs (lncRNAs) are involved in tumorigenesis and progression as critical regulators, while their potential roles in chemoresistance are poorly understood. In this study, we report that the LINC00460-miR-149-5p/miR-150-5p-mutant p53 feedback loop is responsible for oxaliplatin resistance in CRC. First, LINC00460 was found to exhibit higher expression in oxaliplatin-resistant CRC (CRC/OxR) cells compared with parental oxaliplatin-sensitive ones, and this expression pattern depends on mutant p53 (SW480/OxR), not wild-type p53 (HCT116/OxR). Oxaliplatin-induced LINC00460 in SW480/OxR cells was mainly located in the cytoplasm and was associated with AGO2 protein. LINC00460 functions as a competing endogenous RNA (ceRNA) to promote oxaliplatin resistance through sequestering miR-149-5p/miR-150-5p and upregulating the expression of the microRNA (miRNA) target p53. Knockdown of LINC00460 sensitized SW480/OxR cells to oxaliplatin by modulating p53 in vitro and in vivo. In turn, mutant p53 positively regulated the expression of LINC00460, thus forming a feedback loop. Clinical data showed that LINC00460 was upregulated in CRC tissues compared with paired normal tissues and was significantly correlated with clinical stage and node (N) status. Our findings uncover a mechanism for the LINC00460-miR-149-5p/miR-150-5p-mutant p53 feedback loop in oxaliplatin resistance of CRC, and they provide potential therapeutic targets for tumor chemoresistance.

Immune Infiltration Landscape in Lung Squamous Cell Carcinoma Implications

Intrinsic cancer cells and the tumor-infiltrating immune cells (TIICs) recruited to the immune microenvironment define the malignant phenotype of lung squamous cell carcinoma (LUSC). Understanding more about the immune microenvironment of LUSC enables the selection of high-risk patients who would derive benefit from immunotherapy. Based on large public LUSC cohorts obtained from TCGA and GEO datasets, 22 types of infiltrating immune cell subgroups were evaluated by CIBERSORT. Meta-analysis, principal component analysis (PCA), single-sample gene set enrichment analysis (ssGSEA), and hierarchical clustering analysis were used to evaluate specific immune responses of LUSC. The distribution of TIICs of LUSC was entirely different from normal. TIIC subpopulations were also found to be closely associated with clinical features and molecular subtypes. Unsupervised clustering analysis revealed that three distinct TIIC subgroups existed with different survival patterns. TIICs are extensively implicated in the pathogenesis and development of LUSC. Characterizing the composition of TIICs influences the metabolism, pathological stage, and survival of tumor patients. It is hoped that this immune landscape could provide a more accurate understanding of the development and immunotherapy of LUSC.

Context is key: Understanding the regulation, functional control, and activities of the p53 tumour suppressor

The p53 tumour suppressor is considered one of the most critical genes in cancer biology. By upregulating apoptosis, cell cycle arrest, and DNA damage repair in normal cells, p53 prevents the propagation of cells with tumorigenic potential; therefore, mutations in p53 are associated with carcinogenic transformation and can be accompanied by the accumulation of a novel gain-of-function oncogenic protein, mutant p53. Although p53 is most often understood to utilize context-dependent post-translational modifications to achieve regulation of its many target genes, recent research has also sought to define other mechanisms of regulating p53 gene expression prior to translation and to understand how this alternative regulation of p53 may influence target gene expression and cellular outcome. This review attempts to summarize what is known about p53 regulation at the transcriptional, post-transcriptional, and post-translational levels while paying special attention to the ways in which context may influence p53 regulation and subsequent regulation of its target genes.

Auto-antibodies to p53 and the Subsequent Development of Colorectal Cancer in a U.S. Prospective Cohort Consortium

BACKGROUND

Auto-antibodies to tumor suppressor p53 are found in a subset of patients with colorectal cancer. A recent prospective study in the United States has reported a significant 1.8-fold increased odds for colorectal cancer development with prediagnostic seropositivity to p53. In this study, we sought to examine this association in a U.S. colorectal cancer cohort consortium to evaluate the potential utility of p53 auto-antibodies as an early biomarker for colorectal cancer.

METHODS

Auto-antibodies to p53 were measured in prediagnostic blood samples of 3,702 incident colorectal cancer cases and 3,702 controls, matched by age, race, and sex, from 9 U.S. prospective cohorts. The association of seropositivity to p53 with colorectal cancer risk, overall and by time between blood draw and diagnosis, was determined by conditional logistic regression.

RESULTS

Overall, 5% of controls and 7% of cases were seropositive to p53, resulting in a statistically significant 33% increased colorectal cancer risk [odds ratio (OR), 1.33; 95% confidence interval (CI), 1.09-1.61]. By follow-up time, the association was only significant with colorectal cancer diagnoses within 4 years after blood draw (OR, 2.27; 95% CI, 1.62-3.19), but not thereafter (OR, 0.97; 95% CI, 0.76-1.24).

CONCLUSIONS

In this large consortium of prospective cohorts, we found that prediagnostic seropositivity to tumor suppressor p53 was significantly associated with an over 2-fold increased odds of developing colorectal cancer within 4 years after blood draw.

IMPACT

Our finding suggests that p53 seropositivity may not be a useful predictor of long-term colorectal cancer risk; however, it might be considered as a marker to aid in the early diagnosis of colorectal cancer.

Protein phosphatase 1 in tumorigenesis: is it worth a closer look?

Cancer cells take advantage of signaling cascades to meet their requirements for sustained growth and survival. Cell signaling is tightly controlled by reversible protein phosphorylation mechanisms, which require the counterbalanced action of protein kinases and protein phosphatases. Imbalances on this system are associated with cancer development and progression. Protein phosphatase 1 (PP1) is one of the most relevant protein phosphatases in eukaryotic cells. Despite the widely recognized involvement of PP1 in key biological processes, both in health and disease, its relevance in cancer has been largely neglected. Here, we provide compelling evidence that support major roles for PP1 in tumorigenesis.

p53 involvement in clonal hematopoiesis of indeterminate potential

PURPOSE OF REVIEW

Clonal hematopoiesis of indeterminate potential (CHIP) increases with age and occurs when a single mutant hematopoietic stem cell (HSC) contributes to a significant clonal proportion of mature blood lineages. Somatic mutations in the TP53 gene, which encodes the tumor suppressor protein p53, rank in the top five among genes that were mutated in CHIP. This review focuses on mechanisms by which mutant p53 promotes CHIP progression and drives the pathogenesis of hematological malignancies, including myelodysplastic syndromes, and acute myeloid leukemia.

RECENT FINDINGS

TP53 was frequently mutated in individuals with CHIP. Although clinical studies suggest that expansion of HSCs with TP53 mutations predisposes the elderly to hematological neoplasms, there is a significant gap in knowledge regarding the mechanisms by which TP53 mutations promote HSC expansion. Recent findings suggest that several cellular stressors, including hematopoietic transplantation, genotoxic stress, and inflammation, promote the expansion of HSCs with TP53 mutations. Further, TP53 mutations identified in CHIP cooperate with genetic and/or epigenetic changes in leukemogenesis.

SUMMARY

TP53 mutations identified in CHIP are associated with increased risks of de novo and therapy-related hematological neoplasms. Thus, targeting mutant p53 and related pathways holds great potential in preventing CHIP progression and treating hematological malignancies.

Targeting cyclooxygenase by indomethacin decelerates progression of acute lymphoblastic leukemia in a xenograft model

Acute lymphoblastic leukemia (ALL) develops in the bone marrow in the vicinity of stromal cells known to promote tumor development and treatment resistance. We previously showed that the cyclooxygenase (COX) inhibitor indomethacin prevents the ability of stromal cells to diminish p53-mediated killing of cocultured ALL cells in vitro, possibly by blocking the production of prostaglandin E2 (PGE2). Here, we propose that PGE2 released by bone marrow stromal cells might be a target for improved treatment of pediatric ALL. We used a xenograft model of human primary ALL cells in nonobese diabetic-scid IL2rγnull mice to show that indomethacin delivered in the drinking water delayed the progression of ALL in vivo. The progression was monitored by noninvasive in vivo imaging of the engrafted leukemic cells, as well as by analyses of CD19+CD10+ leukemic blasts present in spleen or bone marrow at the termination of the experiments. The indomethacin treatment increased the level of p53 in the leukemic cells, implying that COX inhibition might reduce progression of ALL by attenuating protective paracrine PGE2 signaling from bone marrow stroma to leukemic cells.

Kevetrin induces apoptosis in TP53 wild‑type and mutant acute myeloid leukemia cells

Tumor protein p53 is a key regulator of several cellular pathways, including DNA repair, cell cycle and angiogenesis. Kevetrin exhibits p53-dependent as well as-independent activity in solid tumors, while its effects on leukemic cells remain unknown. The aim of the present study was to analyze the response of acute myeloid leukemia (AML) cell lines (TP53 wild-type: OCI-AML3 and MOLM-13; and TP53-mutant: KASUMI-1 and NOMO-1) to kevetrin at a concentration range of 85–340 µM. The cellular and molecular effects of the treatment were analyzed in terms of cell growth, viability [Annexin V-propidium iodide (PI) staining] and cell cycle alterations (PI staining). Gene expression profiling, western blotting and immunofluorescence were performed to elucidate the pathways underlying kevetrin activity. Pulsed exposure exerted no effect on the wild-type cells, but was effective on mutant cells. After continuous treatment, significant cell growth arrest and apoptosis were observed in all cell lines, with TP53-mutant models displaying a higher sensitivity and p53 induction. Kevetrin also displayed efficacy against TP53 wild-type and mutant primary AML, with a preferential cytotoxic activity against blast cells. Gene expression profiling revealed a common core transcriptional program altered by drug exposure and the downregulation of glycolysis, DNA repair and unfolded protein response signatures. These findings suggest that kevetrin may be a promising therapeutic option for patients with both wild-type and TP53-mutant AML.