Loss of mutant p53 in HaCaT keratinocytes promotes cadmium-induced keratin 17 expression and cell death

BACKGROUND

Cadmium exposure induces dermatotoxicity and epidermal barrier disruption and leads to the development of various pathologies. HaCaT cells are immortalized human keratinocytes that are widely used as alternatives to primary human keratinocytes, particularly for evaluating cadmium toxicity. HaCaT cells bear two gain-of-function (GOF) mutations in the TP53 gene, which strongly affect p53 function. Mutant forms of p53 are known to correlate with increased resistance to various stimuli, including exposure to cytotoxic substances. In addition, keratin 17 (KRT17) was recently shown to be highly expressed in HaCaT cells in response to genotoxic stress. Moreover, p53 is a direct transcriptional repressor of KRT17. However, the impact of TP53 mutations in HaCaT cells on the regulation of cell death and keratin 17 expression is unclear. In this study, we aimed to evaluate the impact of p53 on the response to Cd-induced cytotoxicity.

METHODS AND RESULTS

Employing the MTT assay and Annexin V/propidium iodide staining, we demonstrated that knockout of TP53 leads to a decrease in the sensitivity of HaCaT cells to the cytotoxic effects of cadmium. Specifically, HaCaT cells with TP53 knockout (TP53 KO HaCaT) exhibited cell death at a cadmium concentration of 10 μM or higher, whereas wild-type cells displayed cell death at a concentration of 30 μM. Furthermore, apoptotic cells were consistently detected in TP53 KO HaCaT cells upon exposure to low concentrations of cadmium (10 and 20 μM) but not in wild-type cells. Our findings also indicate that cadmium cytotoxicity is mediated by reactive oxygen species (ROS), which were significantly increased only in TP53 knockout cells treated with 30 μM cadmium. An examination of proteomic data revealed that TP53 knockout in HaCaT cells resulted in the upregulation of proteins involved in the regulation of apoptosis, redox systems, and DNA repair. Moreover, RT‒qPCR and immunoblotting showed that cadmium toxicity leads to dose-dependent induction of keratin 17 in p53-deficient cells but not in wild-type cells.

CONCLUSIONS

The connection between mutant p53 in HaCaT keratinocytes and increased resistance to cadmium toxicity was demonstrated for the first time. Proteomic profiling revealed that TP53 knockout in HaCaT cells led to the activation of apoptosis regulatory circuits, redox systems, and DNA repair. In addition, our data support the involvement of keratin 17 in the regulation of DNA repair and cell death. Apparently, the induction of keratin 17 is p53-independent but may be inhibited by mutant p53.

Pediatric-type high-grade gliomas with PDGFRA amplification in adult patients with Li-Fraumeni syndrome: clinical and molecular characterization of three cases

Li-Fraumeni syndrome (LFS) is an autosomal dominant tumor predisposition syndrome caused by heterozygous germline mutations or deletions in the TP53 tumor suppressor gene. Central nervous system tumors, such as choroid plexus tumors, medulloblastomas, and diffuse gliomas, are frequently found in patients with LFS. Although molecular profiles of diffuse gliomas that develop in pediatric patients with LFS have been elucidated, those in adults are limited. Recently, diffuse gliomas have been divided into pediatric- and adult-type gliomas, based on their distinct molecular profiles. In the present study, we investigated the molecular profiles of high-grade gliomas in three adults with LFS. These tumors revealed characteristic histopathological findings of high-grade glioma or glioblastoma and harbored wild-type IDH1/2 according to whole exome sequencing (WES). However, these tumors did not exhibit the key molecular alterations of glioblastoma, IDH-wildtype such as TERT promoter mutation, EGFR amplification, or chromosome 7 gain and 10 loss. Although WES revealed no other characteristic gene mutations or copy number alterations in high-grade gliomas, such as those in histone H3 genes, PDGFRA amplification was found in all three cases together with uniparental disomy of chromosome 17p, where the TP53 gene is located. DNA methylation analyses revealed that all tumors exhibited DNA methylation profiles similar to those of pediatric-type high-grade glioma H3-wildtype and IDH-wildtype (pHGG H3-/IDH-wt), RTK1 subtype. These data suggest that high-grade gliomas developed in adult patients with LFS may be involved in pHGG H3-/IDH-wt. PDGFRA and homozygous alterations in TP53 may play pivotal roles in the development of this type of glioma in adult patients with LFS.

Pioneering the future of cancer therapy: Deciphering the p53-ferroptosis nexus for precision medicine

The TP53 gene, encoding the p53 protein, has been a focal point of research since its 1979 discovery, playing a crucial role in tumor suppression. Ferroptosis, a distinct form of cell death characterized by lipid peroxide accumulation, has gained prominence since its recognition in 2012. Recent studies have unveiled an intriguing connection between p53 and ferroptosis, with implications for cancer therapy. Recent research underscores p53 as a novel target for cancer therapy, influencing key metabolic processes in ferroptosis. Notably, p53 represses the expression of the cystine-glutamate antiporter SLC7A11, supporting p53-mediated tumor growth suppression. Furthermore, under metabolic stress, p53 mitigates ferroptosis sensitivity, aiding cancer cells in coping and delaying cell death. This dynamic interplay between p53 and ferroptosis has far-reaching implications for various diseases, particularly cancer. This review provides a comprehensive overview of ferroptosis in cancer cells, elucidating p53's role in regulating ferroptosis, and explores the potential of targeting p53 to induce ferroptosis for cancer therapy. Understanding this complex relationship between p53 and ferroptosis offers a promising avenue for developing innovative cancer treatments.

Patient-derived tumor organoids with p53 mutations, and not wild-type p53, are sensitive to synergistic combination PARP inhibitor treatment

Poly (ADP-ribose) polymerase inhibitors (PARPi) are used for patients with BRCA1/2 mutations, but patients with other mutations may benefit from PARPi treatment. Another mutation that is present in more cancers than BRCA1/2 is mutation to the TP53 gene. In 2D breast cancer cell lines, mutant p53 (mtp53) proteins tightly associate with replicating DNA and Poly (ADP-ribose) polymerase (PARP) protein. Combination drug treatment with the alkylating agent temozolomide and the PARPi talazoparib kills mtp53 expressing 2D grown breast cancer cell lines. We evaluated the sensitivity to the combination of temozolomide plus PARPi talazoparib treatment to breast and lung cancer patient-derived tumor organoids (PDTOs). The combination of the two drugs was synergistic for a cytotoxic response in PDTOs with mtp53 but not for PDTOs with wtp53. The combination of talazoparib and temozolomide induced more DNA double-strand breaks in mtp53 expressing organoids than in wild-type p53 expressing organoids as shown by increased γ-H2AX protein expression. Moreover, breast cancer tissue microarrays (TMAs) showed a positive correlation between stable p53 and high PARP1 expression in sub-groups of breast cancers, which may indicate sub-classes of breast cancers sensitive to PARPi therapy. These results suggest that mtp53 could be a biomarker to predict response to the combination of PARPi talazoparib-temozolomide treatment.

Cell fate regulation governed by p53: Friends or reversible foes in cancer therapy

Cancer is a leading cause of death worldwide. Targeted therapies aimed at key oncogenic driver mutations in combination with chemotherapy and radiotherapy as well as immunotherapy have benefited cancer patients considerably. Tumor protein p53 (TP53), a crucial tumor suppressor gene encoding p53, regulates numerous downstream genes and cellular phenotypes in response to various stressors. The affected genes are involved in diverse processes, including cell cycle arrest, DNA repair, cellular senescence, metabolic homeostasis, apoptosis, and autophagy. However, accumulating recent studies have continued to reveal novel and unexpected functions of p53 in governing the fate of tumors, for example, functions in ferroptosis, immunity, the tumor microenvironment and microbiome metabolism. Among the possibilities, the evolutionary plasticity of p53 is the most controversial, partially due to the dizzying array of biological functions that have been attributed to different regulatory mechanisms of p53 signaling. Nearly 40 years after its discovery, this key tumor suppressor remains somewhat enigmatic. The intricate and diverse functions of p53 in regulating cell fate during cancer treatment are only the tip of the iceberg with respect to its equally complicated structural biology, which has been painstakingly revealed. Additionally, TP53 mutation is one of the most significant genetic alterations in cancer, contributing to rapid cancer cell growth and tumor progression. Here, we summarized recent advances that implicate altered p53 in modulating the response to various cancer therapies, including chemotherapy, radiotherapy, and immunotherapy. Furthermore, we also discussed potential strategies for targeting p53 as a therapeutic option for cancer.

Mutant p53 Gain-of-Function in the Spotlight: Are We Suffering a GOF Delusion?

Mutant p53 proteins are often highly expressed in human cancers and have been thought to have oncogenic driver gain-of-function (GOF) properties. Wang and colleagues show, surprisingly, that this is not the case because removing the TP53-mutant gene from human and mouse cancer cells using CRISPR technology has no effect on cancer cell growth in vitro or in vivo. See related article by Wang et al., p. 362 (10) .

Disruption of the TP53 locus in osteosarcoma leads to TP53 promoter gene fusions and restoration of parts of the TP53 signalling pathway

TP53 is the most frequently mutated gene in human cancer. This gene shows not only loss-of-function mutations but also recurrent missense mutations with gain-of-function activity. We have studied the primary bone malignancy osteosarcoma, which harbours one of the most rearranged genomes of all cancers. This is odd since it primarily affects children and adolescents who have not lived the long life thought necessary to accumulate massive numbers of mutations. In osteosarcoma, TP53 is often disrupted by structural variants. Here, we show through combined whole-genome and transcriptome analyses of 148 osteosarcomas that TP53 structural variants commonly result in loss of coding parts of the gene while simultaneously preserving and relocating the promoter region. The transferred TP53 promoter region is fused to genes previously implicated in cancer development. Paradoxically, these erroneously upregulated genes are significantly associated with the TP53 signalling pathway itself. This suggests that while the classical tumour suppressor activities of TP53 are lost, certain parts of the TP53 signalling pathway that are necessary for cancer cell survival and proliferation are retained. In line with this, our data suggest that transposition of the TP53 promoter is an early event that allows for a new normal state of genome-wide rearrangements in osteosarcoma. © 2023 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

TP53 to mediate immune escape in tumor microenvironment: an overview of the research progress

Increasing evidence suggests that key cancer-causing driver genes continue to exert a sustained influence on the tumor microenvironment (TME), highlighting the importance of immunotherapeutic targeting of gene mutations in governing tumor progression. TP53 is a prominent tumor suppressor that encodes the p53 protein, which controls the initiation and progression of different tumor types. Wild-type p53 maintains cell homeostasis and genomic instability through complex pathways, and mutant p53 (Mut p53) promotes tumor occurrence and development by regulating the TME. To date, it has been wildly considered that TP53 is able to mediate tumor immune escape. Herein, we summarized the relationship between TP53 gene and tumors, discussed the mechanism of Mut p53 mediated tumor immune escape, and summarized the progress of applying p53 protein in immunotherapy. This study will provide a basic basis for further exploration of therapeutic strategies targeting p53 protein.

Early Cancer Detection in Li-Fraumeni Syndrome with Cell-Free DNA

People with Li-Fraumeni syndrome (LFS) harbor a germline pathogenic variant in the TP53 tumor suppressor gene, face a near 100% lifetime risk of cancer, and routinely undergo intensive surveillance protocols. Liquid biopsy has become an attractive tool for a range of clinical applications, including early cancer detection. Here, we provide a proof-of-principle for a multimodal liquid biopsy assay that integrates a targeted gene panel, shallow whole-genome, and cell-free methylated DNA immunoprecipitation sequencing for the early detection of cancer in a longitudinal cohort of 89 LFS patients. Multimodal analysis increased our detection rate in patients with an active cancer diagnosis over uni-modal analysis and was able to detect cancer-associated signal(s) in carriers prior to diagnosis with conventional screening (positive predictive value = 67.6%, negative predictive value = 96.5%). Although adoption of liquid biopsy into current surveillance will require further clinical validation, this study provides a framework for individuals with LFS.

SIGNIFICANCE

By utilizing an integrated cell-free DNA approach, liquid biopsy shows earlier detection of cancer in patients with LFS compared with current clinical surveillance methods such as imaging. Liquid biopsy provides improved accessibility and sensitivity, complementing current clinical surveillance methods to provide better care for these patients. See related commentary by Latham et al., p. 23. This article is featured in Selected Articles from This Issue, p. 5.

Targeting Mutant-p53 for Cancer Treatment: Are We There Yet?

BACKGROUND

Mutations in the TP53 gene are the most common among genetic alterations in human cancers, resulting in the formation of mutant p53 protein (mutp53). Mutp53 promotes proliferation, migration, invasion, and metastasis in cancer cells. Not only does the initiation of oncogenesis ensue due to mutp53, but resistance towards chemotherapy and radiotherapy in cancer cells also occurs. This review aims to summarise and discuss the oncogenesis of mutant p53 in cancer cells and introduce the various mutant p53 inhibitors currently being evaluated at the pre-clinical and clinical stages. Compounds that induce the wild-type conformation on the targeted p53 missense mutation, restore or enhance the DNA binding of mutant p53, and inhibit cancer cells' growth are highlighted. In addition, the progression and development of the mutant p53 inhibitors in clinical trials are updated.

CONCLUSION

The progress of developing a cancer treatment that may successfully and efficiently target mutant p53 is on the verge of development. Mutant p53 proteins not only initiate oncogenesis but also cause resistance in cancer cells to certain chemo or radiotherapies, further endorse cancer cell survival and promote migration as well as metastasis of cancerous cells. With this regard, many mutant p53 inhibitors have been developed, some of which are currently being evaluated at the pre-clinical level and have been identified and discussed. To date, APR-246 is the most prominent one that has progressed to the Phase III clinical trial.

Enhancing the invasive traits of breast cancers by CYP1B1 via regulation of p53 to promote uPAR expression

Human cytochrome P450 1B1 (CYP1B1) catalyzes estrogen metabolism to produce metabolites that promote the progression of breast cancer. Since the invasive properties of cancer cells cause cancer relapse, which dramatically reduces patient survival, we investigated the new pro-invasive mechanism involving CYP1B1 in breast cancer. Exploring clinical data from invasive breast cancer patients revealed that CYP1B1 exhibits a potential correlation with urokinase-type plasminogen activator receptor (uPAR). Interestingly, uPAR mRNA expression was elevated in invasive breast cancer patients carrying TP53 genes with driver mutations, and our results showed that CYP1B1 activates the uPAR pathway following regulation of p53 according to its mutant status. CYP1B1 suppressed wild-type (WT) p53 whereas it induced the oncogenic gain-of-function mutant p53R280K, not only via transcriptional regulation but also the protein stabilization and activation following phosphorylation on Ser15 residue of p53R280K. Intriguingly, results from CYP1B1 polymorphic gene study and 4-hydroxyestradiol (4-OHE2) treatment showed that CYP1B1 regulates p53s and uPAR through its enzymatic activity. Furthermore, effects of DMBA and TMS on uPAR expression disappeared in HCT116p53-/- cells, indicating that p53 is critical for uPAR induction by CYP1B1. Collectively, our results demonstrate that CYP1B1 may reduce the relapse-free survival rate of breast cancer patients by inducing invasive traits in cancer cells via p53 regulation based on the mutation status of TP53 genes and further activation of the uPAR pathway. The elucidation of the previously unknown molecular mechanism of CYP1B1 may provide evidence for the development of effective anti-cancer therapeutic strategies that target the progression of cancer invasion.

PRIMA-1 synergizes olaparib-induced cell death in p53 mutant triple negative human breast cancer cell line via restoring p53 function, arresting cell cycle, and inducing apoptosis

This study concerned with assessing the effect of restoring p53 using PRIMA-1 on the anti-cancer activity of olaparib against TP53-mutant triple negative breast cancer (TNBC) cells and exploring the optimum synergistic concentrations and the underlying mechanism. Human BC cell lines, MDA-MB-231 with mutated TP53 gene, and MCF-7 with wild-type TP53 gene were treated with olaparib and/or PRIMA-1. The IC50 value for olaparib was significantly decreased by PRIMA-1 in MDA-MB-231 cells compared to MCF-7 cells. Contrary to MCF-7 cells, co-treatment with olaparib and PRIMA-1 had a synergistic anti-proliferative effect in MDA-MB-231 at all tested concentrations with the best synergistic combination at 45 and 8.5 µM, respectively, and furthermore PRIMA-1 enhanced olaparib-induced apoptosis. This synergistic apoptotic effect was associated with a significant boost in mRNA expression of TP53 gene, cell cycle arrest at G2/M phase, modulation of BRCA-1, BAX and Bcl2 proteins expressions, and induction of active caspase-3. These results present a clue for the utility of combined olaparib and PRIMA-1 in treatment of TP53-mutant TNBC invitro. PRIMA-1 triggers olaparib-induced MDA-MB-231 cell death in a synergistic manner via restoring TP53, decreasing BRCA-1 expression, cell cycle arrest, and enhancement of apoptosis via p53/BAX/Bcl2/caspase 3 pathway.

Exploring the genetic and molecular basis of differences in multiple myeloma of individuals of African and European descent

Multiple Myeloma is a typical example of a neoplasm that shows significant differences in incidence, age of onset, type, and frequency of genetic alterations between patients of African and European ancestry. This perspective explores the hypothesis that both genetic polymorphisms and spontaneous somatic mutations in the TP53 tumor suppressor gene are determinants of these differences. In the US, the rates of occurrence of MM are at least twice as high in African Americans (AA) as in Caucasian Americans (CA). Strikingly, somatic TP53 mutations occur in large excess (at least 4-6-fold) in CA versus AA. On the other hand, TP53 contains polymorphisms specifying amino-acid differences that are under natural selection by the latitude of a population and have evolved during the migrations of humans over several hundred thousand years. The p53 protein plays important roles in DNA strand break repair and, therefore, in the surveillance of aberrant DNA recombination, leading to the B-cell translocations that are causal in the pathogenesis of MM. We posit that polymorphisms in one region of the TP53 gene (introns 2 and 3, and the proline-rich domain) specify a concentration of the p53 protein with a higher capacity to repress translocations in CA than AA patients. This, in turn, results in a higher risk of acquiring inactivating, somatic mutations in a different region of the TP53 gene (DNA binding domain) in CA than in AA patients. Such a mechanism, by which the polymorphic status of a gene influencing its own "spontaneous" mutation frequency, may provide a genetic basis to address ethnicity-related differences in the incidence and phenotypes of many different forms of cancer.

p53 deficient breast cancer cells reprogram preadipocytes toward tumor-protective immunomodulatory cells

The TP53 gene is mutated in approximately 30% of all breast cancer cases. Adipocytes and preadipocytes, which constitute a substantial fraction of the stroma of normal mammary tissue and breast tumors, undergo transcriptional, metabolic, and phenotypic reprogramming during breast cancer development and play an important role in tumor progression. We report here that p53 loss in breast cancer cells facilitates the reprogramming of preadipocytes, inducing them to acquire a unique transcriptional and metabolic program that combines impaired adipocytic differentiation with augmented cytokine expression. This, in turn, promotes the establishment of an inflammatory tumor microenvironment, including increased abundance of Ly6C+ and Ly6G+ myeloid cells and elevated expression of the immune checkpoint ligand PD-L1. We also describe a potential gain-of-function effect of common p53 missense mutations on the inflammatory reprogramming of preadipocytes. Altogether, our study implicates p53 deregulation in breast cancer cells as a driver of tumor-supportive adipose tissue reprogramming, expanding the network of non-cell autonomous mechanisms whereby p53 dysfunction may promote cancer. Further elucidation of the interplay between p53 and adipocytes within the tumor microenvironment may suggest effective therapeutic targets for the treatment of breast cancer patients.

Rictor mediates p53 deactivation to facilitate the malignant transformation of hepatocytes and promote hepatocarcinogenesis

BACKGROUND

Mutations in TP53 gene is considered a main driver of hepatocellular carcinoma (HCC). While TP53 mutations are the leading cause of p53 dysfunction, their occurrence rates may drop to approximately 10% in cohorts without hepatitis B virus and aflatoxin exposure. This observation suggests that the deactivation of wild-type p53 (p53wt) may be a critical factor in the majority of HCC cases. However, the mechanism undermining p53wt activity in the liver remains unclear.

METHODS

Microarray analysis and luciferase assay were utilized to confirm target associations. Gain- and/or loss-of-function methods were employed to assess alterations in signaling pathways. Protein interactions were analyzed by molecular immunological methods and further visualized by confocal microscopy. Bioinformatic analysis was performed to analyze clinical significance. Tumor xenograft nude mice were used to validate the findings in vivo.

RESULTS

Our study highlights the oncogenic role of Rictor, a key component of the mammalian target of rapamycin complex 2 (mTORC2), in hepatocytes. Rictor exerts its oncogenic function by binding to p53wt and subsequently blocking p53wt activity based on p53 status, requiring the involvement of mTOR. Moreover, we observed a dynamic nucleocytoplasmic distribution pattern of Rictor, characterized by its translocation from the nucleus (in precancerous lesions) to the cytoplasm (in HCCs) during malignant transformation. Notably, Rictor is directly targeted by the liver-enriched microRNA miR-192, and the disruption of the miR-192-Rictor-p53-miR-192 signaling axis was consistently observed in both human and rat HCC models. Clinical analysis associated lower miR-192/higher Rictor with shorter overall survival and more advanced clinical stages (P < 0.05). In mice, xenograft tumors overexpressing miR-192 exhibited lower Rictor expression levels, leading to higher p53 activity, and these tumors displayed slower growth compared to untreated HCC cells.

CONCLUSIONS

Rictor dynamically shuttles between the nucleus and cytoplasm during HCC development. Its pivotal oncogenic role involves binding and inhibiting p53wt activity within the nucleus in early hepatocarcinogenesis. Targeting Rictor presents a promising strategy for HCC based on p53 status.

Arsenic trioxide extends survival of Li-Fraumeni syndrome mimicking mouse

Li-Fraumeni syndrome (LFS) is characterized by germline mutations occurring on one allele of genome guardian TP53. It is a severe cancer predisposition syndrome with a poor prognosis, partly due to the frequent development of subsequent primary tumors following DNA-damaging therapies. Here we explored, for the first time, the effectiveness of mutant p53 rescue compound in treating LFS-mimicking mice harboring a deleterious p53 mutation. Among the ten p53 hotspot mutations in IARC LFS cohorts, R282W is one of the mutations predicting the poorest survival prognosis and the earliest tumor onset. Among the six clinical-stage mutant p53 rescue compounds, arsenic trioxide (ATO) effectively restored transactivation activity to p53-R282W. We thus constructed a heterozygous Trp53 R279W (corresponding to human R282W) mouse model for the ATO treatment study. The p53R279W/+ (W/+) mice exhibited tumor onset and overall survival well mimicking the ones of human LFS. Further, 35 mg/L ATO addition in drink water significantly extended the median survival of W/+ mice (from 460 to 596 days, hazard ratio = 0.4003, P = 0.0008). In the isolated tumors from ATO-treated W/+ mice, the representative p53 targets including Cdkn1a, Mdm2, and Tigar were significantly upregulated, accompanying with a decreased level of the proliferation marker Ki67 and increased level of apoptosis marker TUNEL. Together, the non-genotoxic treatment of p53 rescue compound ATO holds promise as an alternative for LFS therapeutic.

Detection of TP53 gene mutation in blood of breast cancer patients based on circulating tumor DNA and its application in prognosis

This experiment was carried out to explore the application value of high throughput gene sequencing technology in detecting TP53 gene mutations in the blood of patients with breast cancer by detecting ctDNA gene mutations, and exploring the relationship between TP53 mutations and clinicopathological characteristics and prognosis of patients. The gene mutation of peripheral blood ctDNA and tissue paraffin DNA (tDNA) of 50 patients was detected by high-throughput sequencing technology. The basic data of 50 cases of Medium to high-risk breast cancer diagnosed and were retrospectively collected, and the clinicopathological characteristics and survival results of TP53 mutant and wild-type patients were compared and analyzed according to the ctDNA detection results and relevant follow-up data. Analyze the impact of TP53 mutations on overall survival and progression-free survival using univariate and multivariate Cox regression models. Among 50 patients, there were 29 cases of 7 kinds of gene mutations detected by ctDNA, and 37 cases of 9 kinds of gene mutations detected by tDNA. Using the gene mutation results detected by tDNA as the gold standard, the sensitivity and specificity of peripheral blood ctDNA in diagnosing TP53 gene mutations are 75% to 100%, 92.31% to 100%, and the overall coincidence rate with tDNA results was 83.33% to 100%. Exon 5 was the most prone to mutation, with a frequency of 24.14% (7/29). The most common type of mutation was the missense mutation of 37.93% (11/29). There was no significant correlation between TP53 mutation and PFS (HR=0.67, 95% CI: 0.41-1.08, P=0.102), while TP53 mutation was a protective factor for OS (HR=0.49, 95% CI: 0.27-0.90, P=0.022). The detection of ctDNA in peripheral blood of breast cancer patients by high-throughput gene sequencing technology can replace tumor tissue sections to understand gene mutation. The TP53 mutation in breast cancer patients is related to tumor size, lymph node metastasis and vascular tumor thrombus, but the prognosis of TP53 mutant patients is similar to that of wild-type patients.

HER2-positive breast cancer progresses rapidly after pyrotinib resistance: acquired RET gene fusion and TP53 gene mutation are potential reasons

Approximately 15-20% of the patients with breast cancer overexpress human epidermal growth factor receptor 2 ( HER2 ). HER2 -positive breast cancer is highly aggressive and has a high relapse rate, suggesting that it is prone to and progresses rapidly after drug resistance. Pyrotinib resistance and changes in patients' conditions after drug resistance are challenging clinical issues and require medical attention. Recently, there are few clinical reports on changes in patients' conditions after pyrotinib resistance. We report a case of a 46-year-old patient with HER2 -positive breast cancer who developed resistance to pyrotinib and rapidly progressed to uncontrolled liver failure in less than a week. To elucidate the cause of the rapid progression, we collected samples of the patient's ascites and performed next-generation sequencing (NGS). On the basis of the NGS results, we speculated that the rapid progression after pyrotinib resistance might be due to RET gene fusion and TP53 gene mutations. Therefore, this case report aims to alert oncologists that patients with HER2 -positive breast cancer, who are resistant to pyrotinib or other targeted drugs, could experience rapid or even flare-up progression and that RET gene fusion and TP53 gene mutations might be potential causes.

Polymorphisms in Cyclooxygenase, Lipoxygenase, and TP53 Genes Predict Colorectal Polyp Risk Reduction by Aspirin in the seAFOod Polyp Prevention Trial

Aspirin and eicosapentaenoic acid (EPA) reduce colorectal adenomatous polyp risk and affect synthesis of oxylipins including prostaglandin E2. We investigated whether 35 SNPs in oxylipin metabolism genes such as cyclooxygenase (PTGS) and lipoxygenase (ALOX), as well as 7 SNPs already associated with colorectal cancer risk reduction by aspirin (e.g., TP53; rs104522), modified the effects of aspirin and EPA on colorectal polyp recurrence in the randomized 2 × 2 factorial seAFOod trial. Treatment effects were reported as the incidence rate ratio (IRR) and 95% confidence interval (CI) by stratifying negative binomial and Poisson regression analyses of colorectal polyp risk on SNP genotype. Statistical significance was reported with adjustment for the false discovery rate as the P and q value. 542 (of 707) trial participants had both genotype and colonoscopy outcome data. Reduction in colorectal polyp risk in aspirin users compared with nonaspirin users was restricted to rs4837960 (PTGS1) common homozygotes [IRR, 0.69; 95% confidence interval (CI), 0.53-0.90); q = 0.06], rs2745557 (PTGS2) compound heterozygote-rare homozygotes [IRR, 0.60 (0.41-0.88); q = 0.06], rs7090328 (ALOX5) rare homozygotes [IRR 0.27 (0.11-0.64); q = 0.05], rs2073438 (ALOX12) common homozygotes [IRR, 0.57 (0.41-0.80); q = 0.05], and rs104522 (TP53) rare homozygotes [IRR, 0.37 (0.17-0.79); q = 0.06]. No modification of colorectal polyp risk in EPA users was observed. In conclusion, genetic variants relevant to the proposed mechanism of action on oxylipins are associated with differential colorectal polyp risk reduction by aspirin in individuals who develop multiple colorectal polyps. SNP genotypes should be considered during development of personalized, predictive models of colorectal cancer chemoprevention by aspirin.

PREVENTION RELEVANCE

Single-nucleotide polymorphisms in genes controlling lipid mediator signaling may modify the colorectal polyp prevention activity of aspirin. Further investigation is required to determine whether testing for genetic variants can be used to target cancer chemoprevention by aspirin to those who will benefit most.

Mutant p53 Gain-of-Function Induces Migration and Invasion through Overexpression of miR-182-5p in Cancer Cells

The master-key TP53 gene is a tumor suppressor that is mutated in more than 50% of human cancers. Some p53 mutants lose their tumor suppressor activity and acquire new oncogenic functions, known as a gain of function (GOF). Recent studies have shown that p53 mutants can exert oncogenic effects through specific miRNAs. We identified the differentially expressed miRNA profiles of the three most frequent p53 mutants (p53R273C, p53R248Q, and p53R175H) after their transfection into the Saos-2 cell line (null p53) as compared with p53WT transfected cells. The associations between these miRNAs and the signaling pathways in which they might participate were identified with miRPath Software V3.0. QRT-PCR was employed to validate the miRNA profiles. We observed that p53 mutants have an overall negative effect on miRNA expression. In the global expression profile of the human miRNome regulated by the p53R273C mutant, 72 miRNAs were underexpressed and 35 overexpressed; in the p53R175H miRNAs profile, our results showed the downregulation of 93 and upregulation of 10 miRNAs; and in the miRNAs expression profile regulated by the p53R248Q mutant, we found 167 decreased and 6 increased miRNAs compared with p53WT. However, we found overexpression of some miRNAs, like miR-182-5p, in association with processes such as cell migration and invasion. In addition, we explored whether the induction of cell migration and invasion by the p53R48Q mutant was dependent on miR-182-5p because we found overexpression of miR-182-5p, which is associated with processes such as cell migration and invasion. Inhibition of mutant p53R248Q and miR-182-5p increased FOXF2-MTSS1 levels and decreased cell migration and invasion. In summary, our results suggest that p53 mutants increase the expression of miR-182-5p, and this miRNA is necessary for the p53R248Q mutant to induce cell migration and invasion in a cancer cell model.

Accurate interpretation of p53 immunohistochemical patterns is a surrogate biomarker for TP53 alterations in large B-cell lymphoma

BACKGROUND

To clarify the relationship between p53 immunohistochemistry (IHC) staining and TP53 alterations (including mutations and deletions) in large B-cell lymphomas (LBCLs) and to explore the possibility of p53 IHC expression patterns as surrogate markers for TP53 alterations.

METHODS

A total of 95 patients diagnosed with LBCLs were selected, and paraffin samples were taken for TP53 gene sequencing, fluorescence in situ hybridization and p53 IHC staining. The results were interpreted by experienced pathologists and molecular pathologists.

RESULTS

Forty-three nonsynonymous TP53 mutations and p53 deletions were detected in 40 cases, whereas the remaining 55 cases had wild-type TP53 genes. The majority of TP53 mutations (34/43, 79.1%) occurred in exons 4-8, and R248Q was the most common mutation codon (4/43, 9.3%). The highest frequency single nucleotide variant was C > T (43.6%). p53 expression was interpreted as follows: Pattern A: p53 staining was positive in 0%-3% of tumor cells, Pattern B: p53 staining was positive in 4-65% of tumor cells, Pattern C: more than 65% of tumor cells were stained positive for p53. The p53 IHC expression patterns were associated with TP53 alterations. Gain of function variants and wild-type TP53 tended to exhibit type C and B p53 expression patterns, but loss of function variants were exclusively seen in type A cases. Additionally, interpretation of the staining by various observers produced significant reproducibility.

CONCLUSIONS

The p53 IHC expression patterns can be used to predict TP53 alterations and are reliable for diverse alteration types, making them possible surrogate biomarkers for TP53 alterations in LBCLs.

DNA2 Nuclease Inhibition Confers Synthetic Lethality in Cancers with Mutant p53 and Synergizes with PARP Inhibitors

The tumor suppressor p53 promotes tumor-suppressive activities including cell-cycle inhibition, apoptosis, senescence, autophagy, and DNA repair. However, somatic mutations in the TP53 gene are one of the most common alterations in human cancers. We previously showed that mutant p53 (mutp53) can bind TopBP1, an ATR activator, to attenuate its ATR-activating function. A partially defective ATR function caused by mutp53 makes cancer cells more vulnerable to inhibitors of other TopBP1-independent ATR activators, such as DNA2. DNA2 plays a role in homologous recombination (HR) repair by resecting DNA ends in double-strand breaks and preparing them for invasion of homologous duplex. Here we identify a new DNA2 inhibitor, namely d16, and show that d16 exhibits anticancer activities and overcomes chemotherapy resistance in mutp53-bearing cancers. Similar to DNA2 depletion, d16 treatment results in cell-cycle arrest mainly at S-phase. Moreover, reexpression of mutp53 in a p53-null cancer cell line makes cells more vulnerable to d16-mediated inhibition of ATR activity. As d16 also inhibits HR, a combination of d16 and PARP inhibitors displays synergistic induction of cell death. DNA2 is often overexpressed in cancer, particularly in cancer cells harboring mutp53. Overexpression of DNA2 is associated with poor outcome in ovarian cancer. Overall, our results provide a rationale to target DNA2 as a new synthetic lethality approach in mutp53-bearing cancers, and further extend the benefit of PARP inhibitors beyond BRCA-mutated cancers.

SIGNIFICANCE

This study identifies a new DNA2 inhibitor as a synthetic lethal targeted therapy for mutp53-harboring cancers, and provides a new therapeutic strategy by combining DNA2 inhibitors with PARP inhibitors for these cancers.

The evaluation of the possibility of Li-Fraumeni syndrome in cancer patients in East Azarbaijan Province of Iran

INTRODUCTION

In 1969, Li-Fraumeni syndrome (LFS), which is a rare cancer predisposition syndrome, was reported for the first time. The main problem in LFS is the mutation in the TP53 gene, which is a crucial tumor suppressor gene in the cell cycle. A hereditary syndrome is inherited in an autosomal dominant pattern. There is a significant correlation between this syndrome and various cancers such as sarcoma, breast cancer, brain tumors, and different other types of malignancies. This study aimed to identify the possibility of LFS in cancer patients in the East Azarbaijan, Iran.

METHODS

In this experimental study, 45 children with cancer in the Northwest of Iran were investigated for LFS. DNA was extracted from the whole blood cells using the salting-out method. The region within the exons 5-8 of the TP53 gene has been replicated via Polymerase Chain Reaction (PCR) method. The PCR products were sent for Sanger sequencing, and finally, the data were analyzed by Chromas software.

RESULTS

In the studied probands, in 12 (26.67%) cases, polymorphisms in Exon 6 and Introns 6 and Intron 7 were identified, and no mutation was observed in exons 5-8 of the TP53 gene.

CONCLUSION

Our results show that there were no mutations in exons 5-8 of the TP53 gene as an indication of LFS possibility in these families. Further studies are needed to be done in a bigger population, and Next-Generation Sequencing (NGS) needs to be done to evaluate the whole genome of these patients to complete our data.

Mutational spectrum of TP53 gene correlates with nivolumab treatment efficacy in advanced gastric cancer (TP53MUT study)

BACKGROUND

Although nivolumab has a high efficacy, reliable biomarkers are needed to predict the efficacy. We evaluated the nivolumab efficacy according to the TP53 mutation in advanced gastric cancer patients enrolled in the GI-SCREEN project.

METHODS

Sequence data of tumour specimens and clinicopathological information of 913 patients with advanced gastric cancer who were enrolled between April 2015 and March 2017 were obtained from the GI-SCREEN database. The follow-up information of 266 patients treated with nivolumab was also provided.

RESULTS

Among 266 patients treated with nivolumab, the objective response rate (ORR) of TP53 wild type (wt) patients (24.6%) was higher than that of TP53 mutant patients (14.8%). Among TP53 mutant patients, the ORR of the frameshift type tended to be higher than the transition and transversion type (23.1%, 13.6%, and 13.0%, respectively). The median progression-free survival (PFS) was statistically longer in TP53 wt patients than in mutant patients (3.3 vs 2.1 months, HR 1.4, 95% CI 1.1-1.9). Among TP53 mutant patients, PFS was statistically longer in the frameshift type than in the transversion type.

CONCLUSION

Nivolumab showed better efficacy in TP53 wt patients than in mutant patients. Among TP53 mutant patients, the frameshift type may have efficacy from nivolumab treatment.

Competition between p53 and YY1 determines PHGDH expression and malignancy in bladder cancer

PURPOSE

Serine metabolism is frequently dysregulated in many types of cancers and the tumor suppressor p53 is recently emerging as a key regulator of serine metabolism. However, the detailed mechanism remains unknown. Here, we investigate the role and underlying mechanisms of how p53 regulates the serine synthesis pathway (SSP) in bladder cancer (BLCA).

METHODS

Two BLCA cell lines RT-4 (WT p53) and RT-112 (p53 R248Q) were manipulated by applying CRISPR/Cas9 to examine metabolic differences under WT and mutant p53 status. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) and non-targeted metabolomics analysis were adopted to identify metabolomes changes between WT and p53 mutant BLCA cells. Bioinformatics analysis using the cancer genome atlas and Gene Expression Omnibus datasets and immunohistochemistry (IHC) staining was used to investigate PHGDH expression. Loss-of-function of PHGDH and subcutaneous xenograft model was adopted to investigate the function of PHGDH in mice BLCA. Chromatin immunoprecipitation (Ch-IP) assay was performed to analyze the relationships between YY1, p53, SIRT1 and PHGDH expression.

RESULTS

SSP is one of the most prominent dysregulated metabolic pathways by comparing the metabolomes changes between wild-type (WT) p53 and mutant p53 of BLCA cells. TP53 gene mutation shows a positive correlation with PHGDH expression in TCGA-BLCA database. PHGDH depletion disturbs the reactive oxygen species homeostasis and attenuates the xenograft growth in the mouse model. Further, we demonstrate WT p53 inhibits PHGDH expression by recruiting SIRT1 to the PHGDH promoter. Interestingly, the DNA binding motifs of YY1 and p53 in the PHGDH promoter are partially overlapped which causes competition between the two transcription factors. This competitive regulation of PHGDH is functionally linked to the xenograft growth in mice.

CONCLUSION

YY1 drives PHGDH expression in the context of mutant p53 and promotes bladder tumorigenesis, which preliminarily explains the relationship between high-frequency mutations of p53 and dysfunctional serine metabolism in bladder cancer.

p53 Immunohistochemical Staining and TP53 Gene Mutations in Endometrial Cancer: Does Null Pattern Correlate With Prognosis?

Whether immunohistochemistry (IHC) of p53 accurately reflects the TP53 mutational status of endometrial carcinoma (EC) has not yet been established. This study aimed to clarify the relationship between p53 IHC and TP53 mutations in EC and to examine whether p53 IHC can be a more convenient prognostic marker than TP53 mutation in EC. We performed p53 IHC staining of EC samples obtained via surgery and genetic analyses using next-generation sequencing. p53 IHC results showed that of the 101 cases, 71 (70%) were wild-type (WT), 12 (12%) were overexpression (OE), and 18 (18%) were in the null group. Missense mutations were found in 9 cases (47.4%) in OE, 2 (10.5%) in null, and 8 (42.1%) in the WT group. Truncating mutations were found in 1 case (8.3%) in OE, 6 (50%) in null, and 5 (41.7%) in the WT group. The 5-year progression-free survival was 0% in OE, 74.8% in null, and 79.0% in the WT group. In the prognosis for each type of TP53 mutation, the 5-year progression-free survival was missense (32.2%), truncating (65.6%), and WT (79.7%). These survival comparisons showed that the p53 IHC OE had the poorest prognosis. These results suggest that the p53 IHC OE is an independent poor prognostic factor for EC and can be used as a simple and rapid surrogate marker for TP53 mutations. Contrastingly, the complete absence of p53 IHC-the null staining pattern-may not accurately predict a TP53 mutation in EC, and it is necessary to be more careful in making the diagnosis of "abnormal."

Antifouling Electrochemiluminescence Biosensor Based on Bovine Serum Albumin Hydrogel for the Accurate Detection of p53 Gene in Human Serum

To detect biomarkers in complex samples, it is fundamental to avoid the nonspecific adsorption of impurities to improve the selectivity of biosensors. In this study, a sensitive antifouling electrochemiluminescence biosensor was proposed based on bovine serum albumin (BSA)- and exonuclease III (Exo III)-mediated nucleic acid cycle signal amplification strategy. Ti3C2Tx-NH4, which has a large surface area and high metal conductivity, was crosslinked with BSA to improve the conductivity of the sensing interface, which shows antifouling performance excellently due to the electrical neutrality and good hydrophilicity of BSA hydrogel. The cyclic amplification strategy based on Exo III and DNA hybridization chain reaction significantly amplified the electrochemiluminescence signal and improved the sensitivity of p53 gene detection. The linear range of the biosensor is 1 fM-1 nM with a detection limit of 0.26 fM. More importantly, the sensor showed excellent selectivity when it was used to detect the p53 gene in real samples, such as serum. Thus, this unique antifouling sensing interface is expected to construct various electrochemical biosensors in clinical diagnosis and biopathological analysis.

[Malignant peripheral nerve sheath tumor: a clinicopathological analysis]

Objective: To investigate the clinicopathological, immunophenotypic, and genetic features of malignant peripheral nerve sheath tumor (MPNST). Methods: Twenty-three cases of MPNST were diagnosed at the Jiangsu Province Hospital (the First Affiliated Hospital of Nanjing Medical University), China, between January 2012 and December 2022 and thus included in the study. EnVision immunostaining and next-generation sequencing (NGS) were used to examine their immunophenotypical characteristics and genomic aberrations, respectively. Results: There were 10 males and 13 females, with an age range of 11 to 79 years (median 36 years), including 14 cases of neurofibromatosis type I-associated MPNST and 9 cases of sporadic MPNST. The tumors were located in extremities (7 cases), trunk (4 cases), neck and shoulder (3 cases), chest cavity (3 cases), paraspinal area (2 cases), abdominal cavity (2 cases), retroperitoneum (1 case), and pelvic cavity (1 case). Morphologically, the tumors were composed of dense spindle cells arranged in fascicles. Periphery neurofibroma-like pattern was found in 73.9% (17/23) of the cases. Under low magnification, alternating hypercellular and hypocellular areas resembled marbled appearance. Under high power, the tumor cell nuclei were irregular, presenting with oval, conical, comma-like, bullet-like or wavy contour. In 7 cases, the tumor cells demonstrated marked cytological pleomorphism and rare giant tumor cells. The mitotic figures were commonly not less than 3/10 HPF, and geographic necrosis was often noted. Immunohistochemically, tumor cells were positive for S-100 (14/23, 60.9%) and SOX10 (11/23, 47.8%). The loss of the CD34-positive fibroblastic network encountered in neurofibromas was observed in 14/17 of the MPNST cases. The loss of H3K27me3 expression was observed in 82.6% (19/23) of the cases. Moreover, SDHA and SDHB losses were presented in one case. NGS revealed that NF1 gene loss of function (germline or somatic) were found in all 5 cases tested. Furthermore, four cases accompanied with somatic mutations of SUZ12 gene and half of them had somatic mutations of TP53 gene, while one case with germline mutation in SDHA gene and somatic mutations in FAT1, BRAF, and KRAS genes. Available clinical follow-up was obtained in 19 cases and ranged from 1 to 67 months. Four patients died of the disease, all of whom had the clinical history of neurofibromatosis type Ⅰ. Conclusions: MPNST is difficult to be differentiated from a variety of spindle cell tumors due to its wide spectrum of histological morphology and complex genetic changes. H3K27me3 is a useful diagnostic marker, while the loss of CD34 positive fibroblastic network can also be a diagnostic feature of MPNST. NF1 gene inactivation mutations and complete loss of PRC2 activity are the common molecular diagnostic features, but other less commonly recurred genomic aberrations might also contribute to the MPNST pathogenesis.

Anticancer effect of polyphenolic acid enriched fractions from Grewia bracteata Roth on tumor cells and their p53 gene independent ROS mediated apoptosis in colon cancer cells

It is the first report on leaves of Grewia bracteata Roth for its anticancer effect. In this study, three polarity-guided solvent extracts of Grewia bracteata leaves from n-hexane (GLH), ethyl acetate (GLE), and methanol (GLM) were screened for anticancer effects on HeLa, HCT-116, MCF-7, HCT-116 p53-/- and PC-3 cells via methyl thiazoldiphenyltetrazolium bromide (MTT) assay. Based on the results, GLM was fractionated, and the obtained fractions were tested on HCT-116 cells. Further, FT-IR, HPLC analysis, clonogenic assay, wound healing assay, DCFDA, and cell cycle experiments were conducted on HCT-116 cells. The extracts from methanol (GLM) and ethyl-acetate (GLE) demonstrated a more selective and promising inhibition on HCT-116 cells than others. Notably, GLM recorded superior inhibition on HCT-116 p53-/- than GLE. Amongst, the methanol column fraction (GMCF) showed prominent inhibition on HCT-116 (IC50:63.55 ± 0.61 μg/ml) and HCT-116 p53-/- (IC50: 84.51 ± 0.58 μg/ml) cells. Further, the test on normal cells (NKE) revealed minimal toxicity of GMCF. The phytochemical test, FT-IR, HPLC, and LC-HRMS analyses confirmed the high abundance of polyphenolic acid/polyphenols in GMCF. Further, the clonogenic and wound healing assays on HCT-116 cells were also performed. Later, the probable cell death mechanism was identified using DCFDA and cell cycle experiments. These experiments disclosed that GMCF induced HCT-116 cell death was probably due to reactive oxygen species (ROS) upregulation and cells cycle arrest at SubG0 phase. It inferred that the activity is most probably p53 independent, a tumor suppressor gene responsible for drug resistance in colon cancer.

Low Frequency of Aflatoxin Induced TP53 Gene Codon 249 Mutation in Hepatocellular Carcinoma from Egyptian Patients Living in the Nile Delta Region

OBJECTIVE

Study the frequency of codon 7 (c.747 G>T, p. R249S) mutation associated with Aflatoxin B1 (AFB1) exposure in Egyptian patients with hepatocellular carcinoma (HCC).

METHODS

We utilized restriction fragment polymorphism and direct sequencing to assess codon 7 mutations in 104 hepatocellular carcinomas. The expression of TP53 protein in the tumors were assessed in 44 tumors by a monoclonal rabbit antibody.

RESULTS

We identified a single 1/104 (1%) with c.747 G>T, p. R249S variant. 28/44 (63.6%) tumors showed no or occasional (less than < 5%) nuclear staining; 9/44 (20.4%) showed mild to moderate (5-49%) and 7/44 (15.9%) showed strong ≥ 50% staining.

CONCLUSION

We observed much lower frequency of TP53 gene than previously published results suggesting geographical alterations in AFB1 exposure in Egypt.

Impact of Interaction between Single Nucleotide Polymorphism of XRCC1, XRCC2, XRCC3 with Tumor Suppressor Tp53 Gene Increases Risk of Breast Cancer: A Hospital Based Case-Control Study

BACKGROUND

At present very little information is available on combined effects of DNA repair genes with tumor suppressor gene polymorphisms and their association with cancer susceptibility. No such association studies have been carried out with breast cancer or any other cancer from India. Present study was conducted to study the combined effects of SNPs of XRCC1, XRCC2, XRCC3 with Arg72Pro and Arg249Ser SNPs of TP53 gene in risk of BC in rural parts of India.

METHODS

The polymorphisms of Arg194Trp, Arg280His, Arg399Gln of XRCC1, Arg188His of XRCC2 and Thr241Met of  XRCC3 with Arg72Pro and Arg249Ser of TP53 gene polymorphisms was studied by polymerase chain reaction-based restriction fragment length polymorphism (PCR-RFLP) method. The association among the polymorphisms with breast cancer risk was studied by Odds ratio within 95% confidence interval and SNP-SNP interaction were confirmed by logistic regression analysis.

RESULTS

The results of genotype frequency distribution of XRCC1, XRCC2, XRCC3 genotypes showed positive association between XRCC1 Arg280His polymorphism and BC risk (OR=4.54; 95% CI: 3.36- 6.15; p<0.0001).  Also the heterozygous genotypes Arg188His of XRCC2 (OR=1.58; 95% CI: 1.13- 2.21; p=0.007) and Thr241Met genotype of XRCC3 (OR=2.13; 95% CI: 1.44- 3.13; p=0.0001) were associated with BC risk. The combination of heterozygous Arg280His genotype of XRCC1 along with Arg72Pro genotype of TP53 increased the risk of BC (OR=4.53; 95% CI: 2.85-7.20); p<0.0001). Similarly,  the combined effect of heterozygous Arg/His genotype of XRCC1 with heterozygous Arg/Ser genotype of TP53 at codon 249 showed significant association with increased BC risk (OR=5.08; 95% CI: 2.86-9.04); p<0.0001).

CONCLUSION

The findings derived from our study concluded that the heterozygous variant Arg280His genotype of XRCC1 and Thr241Met polymorphism of XRCC3 in combination with heterozygous arginine72proline genotype and heterozygous Arg249Ser polymorphism of TP53 showed significant association with breast cancer risk in Maharashtrian women.

Triple-negative breast tumors are dependent on mutant p53 for growth and survival

The TP53 tumor suppressor gene is mutated early in the majority of patients with triple-negative breast cancer (TNBC). The most frequent TP53 alterations are missense mutations that contribute to tumor aggressiveness. We developed an autochthonous somatic K14-Cre driven TNBC mouse model with p53R172H and p53R245W mutations in which mutant p53 can be toggled on and off genetically while leaving the tumor microenvironment intact and wild-type for p53. These mice develop TNBCs with a median latency of 1 y. Deletion of mutant p53R172H or p53R245W in vivo in these tumors blunts their tumor growth and significantly extends survival of mice. Downstream analyses revealed that deletion of mutant Trp53 activated the cyclic GMP-AMP Synthase-Stimulator of Interferon Genes pathway but did not cause apoptosis implicating other mechanisms of tumor regression. Furthermore, we determined that only tumors with stable mutant p53 are dependent on mutant p53 for growth.

Activation of p53-regulated pro-survival signals and hypoxia-independent mitochondrial targeting of TIGAR by human papillomavirus E6 oncoproteins

The high-risk subtype human papillomaviruses (hrHPVs) infect and oncogenically transform basal epidermal stem cells associated with the development of squamous-cell epithelial cancers. The viral E6 oncoprotein destabilizes the p53 tumor suppressor, inhibits p53 K120-acetylation by the Tat-interacting protein of 60 kDa (TIP60, or Kat5), and prevents p53-dependent apoptosis. Intriguingly, the p53 gene is infrequently mutated in HPV + cervical cancer clinical isolates which suggests a possible paradoxical role for this gatekeeper in viral carcinogenesis. Here, we demonstrate that E6 activates the TP53-induced glycolysis and apoptosis regulator (TIGAR) and protects cells against oncogene-induced oxidative genotoxicity. The E6 oncoprotein induces a Warburg-like stress response and activates PI3K/PI5P4K/AKT-signaling that phosphorylates the TIGAR on serine residues and induces its hypoxia-independent mitochondrial targeting in hrHPV-transformed cells. Primary HPV + cervical cancer tissues contain high levels of TIGAR, p53, and c-Myc and our xenograft studies have further shown that lentiviral-siRNA-knockdown of TIGAR expression inhibits hrHPV-induced tumorigenesis in vivo. These findings suggest the modulation of p53 pro-survival signals and the antioxidant functions of TIGAR could have key ancillary roles during HPV carcinogenesis.

Interferon-ε is a tumour suppressor and restricts ovarian cancer

High-grade serous ovarian cancers have low survival rates because of their late presentation with extensive peritoneal metastases and frequent chemoresistance1, and require new treatments guided by novel insights into pathogenesis. Here we describe the intrinsic tumour-suppressive activities of interferon-ε (IFNε). IFNε is constitutively expressed in epithelial cells of the fallopian tube, the cell of origin of high-grade serous ovarian cancers, and is then lost during development of these tumours. We characterize its anti-tumour activity in several preclinical models: ovarian cancer patient-derived xenografts, orthotopic and disseminated syngeneic models, and tumour cell lines with or without mutations in Trp53 and Brca genes. We use manipulation of the IFNε receptor IFNAR1 in different cell compartments, differential exposure status to IFNε and global measures of IFN signalling to show that the mechanism of the anti-tumour activity of IFNε involves direct action on tumour cells and, crucially, activation of anti-tumour immunity. IFNε activated anti-tumour T and natural killer cells and prevented the accumulation and activation of myeloid-derived suppressor cells and regulatory T cells. Thus, we demonstrate that IFNε is an intrinsic tumour suppressor in the female reproductive tract whose activities in models of established and advanced ovarian cancer, distinct from other type I IFNs, are compelling indications of potential new therapeutic approaches for ovarian cancer.

Loss of p53 enhances the tumor-initiating potential and drug resistance of clonogenic multiple myeloma cells

Tumor relapse and drug resistance are major factors that limit the curability of multiple myeloma (MM). New regimens have improved overall MM survival rates, but patients with high-risk features continue to have inferior outcomes. Chromosome 17p13 deletion (del17p) that includes the loss of the TP53 gene is a high-risk cytogenetic abnormality and is associated with poor clinical outcomes owing to relatively short remissions and the development of pan-drug resistant disease. Increased relapse rates suggest that del17p enhances clonogenic growth, and we found that the loss of p53 increased both the frequency and drug resistance of tumor-initiating MM cells (TICs). Subsequent RNA sequencing (RNA-seq) studies demonstrated significant activation of the Notch signaling pathway and upregulation of inhibitor of DNA binding (ID1/ID2) genes in p53-knock out (p53-KO) cells. We found that the loss of ID1 or HES-1 expression or treatment with a gamma-secretase inhibitor (GSI) significantly decreased the clonogenic growth of p53-KO but not p53 wild-type cells. GSI treatment in a small set of MM specimens also reduced the clonogenic growth in del17p samples but not in non-del17p samples. This effect was specific as overexpression of the Notch intracellular domain (NICD) rescued the effects of GSI treatment. Our study demonstrates that the Notch signaling and ID1 expression are required for TIC expansion in p53-KO MM cells. These findings also suggest that GSI may be specifically active in patients with p53 mutant MM.

An African-Specific Variant of TP53 Reveals PADI4 as a Regulator of p53-Mediated Tumor Suppression

TP53 is the most frequently mutated gene in cancer, yet key target genes for p53-mediated tumor suppression remain unidentified. Here, we characterize a rare, African-specific germline variant of TP53 in the DNA-binding domain Tyr107His (Y107H). Nuclear magnetic resonance and crystal structures reveal that Y107H is structurally similar to wild-type p53. Consistent with this, we find that Y107H can suppress tumor colony formation and is impaired for the transactivation of only a small subset of p53 target genes; this includes the epigenetic modifier PADI4, which deiminates arginine to the nonnatural amino acid citrulline. Surprisingly, we show that Y107H mice develop spontaneous cancers and metastases and that Y107H shows impaired tumor suppression in two other models. We show that PADI4 is itself tumor suppressive and that it requires an intact immune system for tumor suppression. We identify a p53-PADI4 gene signature that is predictive of survival and the efficacy of immune-checkpoint inhibitors.

SIGNIFICANCE

We analyze the African-centric Y107H hypomorphic variant and show that it confers increased cancer risk; we use Y107H in order to identify PADI4 as a key tumor-suppressive p53 target gene that contributes to an immune modulation signature and that is predictive of cancer survival and the success of immunotherapy. See related commentary by Bhatta and Cooks, p. 1518. This article is highlighted in the In This Issue feature, p. 1501.

Identifying p53 Target Genes Using Hypomorphic Variants

SUMMARY

The reduced tumor suppression activity of hypomorphic variants of the TP53 gene was used by Indeglia and colleagues to corroborate PADI4 as a p53 target. The study makes a noteworthy advancement in comprehending the downstream implications of TP53-PDI4, including potential predictions of survival and the efficacy of immunotherapy. See related article by Indeglia et al., p. 1696 (4).

The African-centric P47S Variant of TP53 Confers Immune Dysregulation and Impaired Response to Immune Checkpoint Inhibition

The tumor suppressor TP53 is the most frequently mutated gene in cancer and is mutationally inactivated in 50% of sporadic tumors. Inactivating mutations in TP53 also occur in Li Fraumeni syndrome (LFS). In addition to germline mutations in TP53 in LFS that completely inactivate this protein, there are many more germline mutant forms of TP53 in human populations that partially inactivate this protein: we call these partially inactivating mutations "hypomorphs." One of these hypomorphs is a SNP that exists in 6%-10% of Africans and 1%-2% of African Americans, which changes proline at amino acid 47 to serine (Pro47Ser; P47S). We previously showed that the P47S variant of p53 is intrinsically impaired for tumor suppressor function, and that this SNP is associated with increased cancer risk in mice and humans. Here we show that this SNP also influences the tumor microenvironment, and the immune microenvironment profile in P47S mice is more protumorigenic. At basal levels, P47S mice show impaired memory T-cell formation and function, along with increased anti-inflammatory (so-called "M2") macrophages. We show that in tumor-bearing P47S mice, there is an increase in immunosuppressive myeloid-derived suppressor cells and decreased numbers of activated dendritic cells, macrophages, and B cells, along with evidence for increased T-cell exhaustion in the tumor microenvironment. Finally, we show that P47S mice demonstrate an incomplete response to anti-PD-L1 therapy. Our combined data suggest that the African-centric P47S variant leads to both intrinsic and extrinsic defects in tumor suppression.

Significance

Findings presented here show that the P47S variant of TP53 influences the immune microenvironment, and the immune response to cancer. This is the first time that a naturally occurring genetic variant of TP53 has been shown to negatively impact the immune microenvironment and the response to immunotherapy.

p53 expression in cytology samples may represent a marker of early-stage cancer

BACKGROUND

TP53 gene plays a major role in the negative control of cell proliferation and in the regulation of signaling cascades. TP53 mutation may have a relevant role in the malignant transformation of thyroid cells as well as thyroid tumor progression. TP53 mutation has been detected only in few well differentiated thyroid carcinomas and is absent in benign conditions.

METHODS

A total of 162 prospective thyroid cytology and corresponding histological samples diagnosed from atypia of indeterminate significance (AUS) to malignant, were studied via immunocytochemistry for p53. Hence, 50 benign lesions (B) were used as negative control. Molecular analysis for p53 only was performed.

RESULTS

The cytology resulted in 50 B, 48 AUS, 40 follicular neoplasms (FNs), 23 suspicious for malignancy (SFM), and 1 malignant (M) case. The authors reported 102 negative and 60 positive p53 cases. The 60 positive cases included 27 cases with weak and/or focal cytoplasmic positivity (+1) and 33 with cases moderate (2+) to strong (3+) cytoplasmic and/or nuclear expression. Overall, 71 cases had histology (2 B, 11 AUS, 37 FN, 20 SFM, and 1 M) including 61.7% benign and 38.2% malignant diagnoses. Only 16 of 71 (5 FN, 10 SFM, and 1 M) were p53-positive. Furthermore, 100% AUS and 86.5% FN cases were p53-negative, none of which had malignant histology. All p53-positive cases were associated with a larger nodule size, tall-cell variant subtype, multifocality, extra thyroidal infiltration, and nodal metastases. Noninvasive follicular thyroid neoplasm with papillary like nuclear features were negative for p53. Few discrepancies in p53 intensity were observed on histology; there were no differences with the molecular testing.

CONCLUSIONS

p53 might be useful in discriminating thyroid follicular lesions. p53 is likely to be a useful diagnostic marker in recognizing indeterminate lesions that are well-differentiated thyroid cancers.

Surveillance imaging and early surgical intervention for improved CNS tumor outcomes in children with Li-Fraumeni syndrome: Children's National Hospital experience and literature review

OBJECTIVE

Li-Fraumeni syndrome (LFS) is a cancer predisposition syndrome caused by germline mutations in the TP53 gene. CNS tumors are the fourth most common tumor type in LFS, and recent screening guidelines demonstrate that early tumor detection is associated with improved long-term survival. However, there is a paucity of data regarding surgical intervention when lesions are identified in asymptomatic patients on surveillance imaging. The authors investigated this through their cohort and literature review.

METHODS

The cohort consisted of children seen in the Pediatric Cancer Genetics Program at Children's National Hospital between August 2012 and August 2021. The authors also include a PubMed (MEDLINE) literature search of articles from 2006 to 2021 related to surveillance and CNS tumors in patients with LFS. Studies in which CNS tumors were not identified or detailed patient information was not provided were excluded. Patients from the selected articles and the authors' cohort were added for further analysis.

RESULTS

Between August 2012 and August 2021, 10 children with LFS and CNS tumors were assessed at Children's National Hospital: 4 who were known carriers of the TP53 mutation had CNS lesions found on surveillance imaging, whereas 6 presented with symptomatic CNS lesions and were either known or subsequently found to have germline TP53 mutations. The literature search identified 148 articles, 7 of which were included in this review. Patients from the literature and the present cohort were added for a total of 56 CNS lesions. A majority of the low-grade CNS lesions (22/24, 92%) were found on surveillance protocols in asymptomatic patients, whereas the majority of the high-grade lesions (22/26, 85%) presented in symptomatic patients who were not undergoing routine surveillance or as the initial diagnosis of LFS. The authors noted a significant survival advantage in pediatric patients with low-grade lesions, with an overall survival of 100% at 30 months. Minor limitations of the study include patient sample size and limitations in the patient cohort due to this being a retrospective rather than a prospective study.

CONCLUSIONS

Data presented in this study support surveillance protocols in LFS and demonstrate the importance of dedicated CNS imaging and early surgical intervention when lesions are identified. Systematic review registration no.: CRD42022372610 (www.crd.york.ac.uk/prospero).

Relative biological effectiveness of low-energy X-rays (25 kV) in mutant p53 cancer cells

Low-energy X-rays as used in radiation therapy and diagnostics such as mammography are associated with a certain risk of promoting tumour development, especially in patients with mutations in cancer-related genes like TP53. The present study therefore addressed the relative biological effectiveness (RBE) of low-energy X-rays for two human adenocarcinoma cell lines of the breast (MDA-MB-468) and pancreas (BxPC-3) with a mutation in the TP53 gene. Clonogenic survival and cytogenetic changes in terms of micronuclei (MN) formation were determined following irradiation with 25 kV X-rays and 200 kV reference irradiation in the dose range of 1-8 Gy. Except the frequency of MN-containing binucleated cells (BNC) (BNC + MN/BNC) in breast cancer cells yielding an RBE between 0.6 and 0.8, both cell lines displayed dose-dependent variations of RBE values between 1 and 2 for all biological end points (cell survival, (BNC + MN/BNC), MN/BNC, MN/(BNC + MN)) with increased effectiveness of 25 kV irradiation in pancreatic compared to breast cancer cells. The results confirm previous findings indicating increased effectiveness of low-energy X-rays and underline the necessity of careful risk estimation for cancer screening programmes.

Common activities and predictive gene signature identified for genetic hypomorphs of TP53

Missense mutations that inactivate p53 occur commonly in cancer, and germline mutations in TP53 cause Li Fraumeni syndrome, which is associated with early-onset cancer. In addition, there are over two hundred germline missense variants of p53 that remain uncharacterized. In some cases, these germline variants have been shown to encode lesser-functioning, or hypomorphic, p53 protein, and these alleles are associated with increased cancer risk in humans and mouse models. However, most hypomorphic p53 variants remain un- or mis-classified in clinical genetics databases. There thus exists a significant need to better understand the behavior of p53 hypomorphs and to develop a functional assay that can distinguish hypomorphs from wild-type p53 or benign variants. We report the surprising finding that two different African-centric genetic hypomorphs of p53 that occur in distinct functional domains of the protein share common activities. Specifically, the Pro47Ser variant, located in the transactivation domain, and the Tyr107His variant, located in the DNA binding domain, both share increased propensity to misfold into a conformation specific for mutant, misfolded p53. Additionally, cells and tissues containing these hypomorphic variants show increased NF-κB activity. We identify a common gene expression signature from unstressed lymphocyte cell lines that is shared between multiple germline hypomorphic variants of TP53, and which successfully distinguishes wild-type p53 and a benign variant from lesser-functioning hypomorphic p53 variants. Our findings will allow us to better understand the contribution of p53 hypomorphs to disease risk and should help better inform cancer risk in the carriers of p53 variants.

The Role of TP53 in Adaptation and Evolution

The TP53 gene is a major player in cancer formation, and it is considered the most important tumor suppressor gene. The p53 protein acts as a transcription factor, and it is involved in DNA repair, senescence, cell-cycle control, autophagy, and apoptosis. Beyond cancer, there is evidence that TP53 is associated with fertility, aging, and longevity. Additionally, more evidence exists that genetic variants in TP53 are associated with environmental adaptation. Special TP53 amino-acid residues or pathogenic TP53 mutations seem to be adaptive for animals living in hypoxic and cold environments or having been exposed to starvation, respectively. At the somatic level, it has recently been proven that multiple cancer genes, including TP53, are under positive selection in healthy human tissues. It is not clear why these driver mutations do not transform these tissues into cancerous ones. Other studies have shown that elephants have multiple TP53 copies, probably this being the reason for the very low cancer incidence in these large animals. This may explain the famous Peto's paradox. This review discusses in detail the multilevel role of TP53 in adaptation, according to the published evidence. This role is complicated, and it extends from cells to individuals and to populations.