Human TP53 Research Articles

Association between hepatitis C virus genotype 4 and renal cell carcinoma: Molecular and virological studies.

Hepatitis C virus (HCV) is the most common infection worldwide. The correlation between HCV and renal cell carcinoma (RCC) is still mysterious. Therefore, the relationship between HCV and RCC was investigated. The study included 100 patients with RCC; 32 with HCV infection, and 68 without HCV infection. Expressions of viral proteins (NS3 and NS5A) were tested using an immune electron-microscope (IEM) and immunohistochemistry (IHC). IHC and quantitative real time-PCR investigated the presentation of human proteins TP53 and p21 genes. Transmission electron (TEM) detected viral-like particles in infected RCC tissues. The gene and protein expression of P53 was higher in HCV positive versus HCV negative patients and p21 was lower in HCV positive versus HCV negative in both tumor and normal tissue samples. Viral like particles were observed by TEM in the infected tumor and normal portion of the RCC tissues and the plasma samples. The IEM showed the depositions of NS3 and NS5A in infected renal tissues, while in noninfected samples, were not observed. The study hypothesizes that a correlation between HCV and RCC could exist through successfully detecting HCV-like particles, HCV proteins, and (p53 and p21) in RCC-infected patients.

Induction of the human CDC45 gene promoter activity by natural compound trans‑resveratrol.

GGAA motifs in the human TP53 and HELB gene promoters play a part in responding to trans‑resveratrol (Rsv) in HeLa S3 cells. This sequence is also present in the 5'‑upstream region of the human CDC45 gene, which encodes a component of CMG DNA helicase protein complex. The cells were treated with Rsv (20 µM), then transcripts and the translated protein were analyzed by quantitative RT‑PCR and western blotting, respectively. The results showed that the CDC45 gene and protein expression levels were induced after the treatment. To examine whether they were due to the activation of transcription, a 5'‑upstream 556‑bp of the CDC45 gene was cloned and inserted into a multi‑cloning site of the Luciferase (Luc) expression vector. In the present study, various deletion/point mutation‑introduced Luc expression plasmids were constructed and they were used for the transient transfection assay. The results showed that the GGAA motif, which is included in a putative RELB protein recognizing sequence, plays a part in the promoter activity with response to Rsv in HeLa S3 cells.

Abstract 3166: Lipid nanoparticles as an efficient transfection method for the delivery of elephant TP53 and retrogene9 into osteosarcoma cells

Abstract Lipid nanoparticles (LNPs) continue to be at the forefront of nanotechnology research due to their versatile and effective ability to deliver DNA, RNA, and small molecules through the cell membrane. Since LNPs are formulated with lipids found naturally in cells, they generate a lower risk for immunogenic response and cause significantly less cell death than traditional transfection methods, such as electroporation. Our microfluidics assembled LNPs have shown transfection efficiencies over 80%, substantially higher than observed with other transfection techniques, and continues to increase over the first 72 hours. We previously reported that elephant TP53 (EP53) induces apoptosis in cancer cells at higher rates than human TP53 (huTP53), and elephant TP53 RETROGENE9 (EP53-R9) contributes to apoptosis through transcription independent mechanisms. To further characterize the effectiveness of these genes, osteosarcoma cell lines were transfected with huTP53, EP53, and EP53-R9 nanoplasmid and mRNA loaded LNPs. Cells treated with EP53 and huTP53 nanoplasmid-loaded LNPs had significantly increased caspase activity and cell death compared to those treated with the empty vector control (P<.0001), with over 90% of all cells treated with either type of p53 dead after 72 hours. Immunocytochemistry was performed to image cells using confocal microscopy, which showed a 36-fold increase in TP53 signal in the nucleus of nanoplasmid LNP treated cells after 72 hours as compared to untreated osteosarcoma cells. In contrast, cells treated with the mRNA LNPs had a 7-fold increase in TP53 signal over 72 hours, though the transfection efficiency was equivalent to the nanoplasmid treated cells. Future studies will assess the efficacy of EP53 and EP53-R9 LNPs in vivo in osteosarcoma mouse models. These results demonstrate the potential of LNP mediated delivery of EP53 and EP53-R9 to be developed as a new treatment approach for cancer patients. Citation Format: Madison Sanborn, Aaron Rogers, Gareth Mitchell, Ryan Kennington, Miranda Sharp, Joshua D. Schiffman, Lisa M. Abegglen. Lipid nanoparticles as an efficient transfection method for the delivery of elephant TP53 and retrogene9 into osteosarcoma cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3166.

Abstract 2828: Combining neratinib with trastuzumab deruxtecan to treat HER2;TP53 co-mutated breast cancers

Abstract In metastatic breast cancer, HER2 activating mutations frequently co-occur with mutations in the TP53 gene and patients with these two co-occuring mutations have a lower response rate to neratinib. In order to address this clinical problem, we bred HER2 activating mutant transgenic mice with two different alleles of TP53. We used mice with the TP53 R172H mutation, which is the murine homolog of the human hotspot TP53 R175H mutation, and mice with TP53flox/flox allele, which mimics TP53 truncating mutations seen in human breast cancers. All three H53 genotypes (H53null, H53172/WT, and H53172/null) developed breast cancers faster than H mice, with H53172/null mice developing breast tumors the fastest, at just 6 weeks after adenoviral-Cre injection into the mammary fat pad. We developed organoids from these murine breast cancers and found that all H53 genotype organoids were less sensitive to neratinib compared to H, however, neratinib was able to synergize with trastuzumab deruxtecan (T-DXd), likely through neratinib mediated increased internalization of T-DXd. Prior literature studies suggest TP53 mutant cancer cells may have therapeutic vulnerabilities to the topoisomerase 1 (Top1) inhibitors. Organoids from all three H53 genotypes were sensitive to the Top1 inhibitor, exatecan. H53172/WT behaved like H organoids with G1 phase cell cycle arrest and induction of p21 expression after exatecan treatment. In contrast, H53null and H53172/null failed to induce p21 and arrested at late-S/G2 phase. Additional animal experiments with these H53 genotypes are in progress and results will be presented at the AACR Annual Meeting. Abbreviation Genotype Median tumor formation (weeks) Neratinib IC50 (nM) Neratinib +T-DXd H HER2V777L 28 10 Not determined H53null HER2V777L;TP53flox/flox 10 240 Synergy H53172/WT HER2V777L;TP53R172H/WT 11 100 Synergy H53172/null HER2V777L;TP53R172H/flox 6 150 Synergy Citation Format: Xiaoqing (Cathy) Cheng, Maureen Highkin, Jacob Hsia, Julie L. Prior, Ian S. Hagemann, Ron Bose. Combining neratinib with trastuzumab deruxtecan to treat HER2;TP53 co-mutated breast cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2828.

Abstract 1262: Comparative analysis of TP53 alleles in pancreatic ductal adenocarcinoma

Abstract The transcription factor p53 is a tumor suppressor capable of inducing cell cycle arrest, senescence, and apoptosis. Both truncating loss-of-function mutations and point mutations of the TP53 gene (mouse gene Trp53), which encodes for the p53 protein, are frequently observed across human cancers. While point mutations in p53 result in loss of canonical tumor suppressor function, recent studies suggest that these mutated proteins acquire pro-tumorigenic gain-of-function properties. For example, Trp53R172H mutations (the murine homolog of TP53R175H, the most common human TP53 variant) enhance metastatic spread relative to deletion mutations in mouse models of advanced pancreatic ductal adenocarcinoma (PDAC). To further explore the differential functions of p53 point and deletion mutants in cancer progression, we performed a rigorous comparative analysis of Trp53 alleles in vivo using Mosaic Analysis with Double Markers (MADM) in mice. MADM uses stochastic mitotic recombination to induce two genotypically distinct daughter cells - created at 1-to-1 ratios - expressing different Trp53 variants dependent on the genotype of the mouse (+/+ vs. -/-, R172H/R172H vs. +/+, R172H/R172H vs. -/-) and simultaneously label them with unique genetically encoded fluorescent markers (TdTomato vs. GFP). We integrated MADM into a faithful Kras-driven model of pancreatic tumorigenesis and used fluorescence microscopy to trace subclonal populations with various p53 alleles within the same mouse. By analyzing the ratio of TdTomato+ to GFP+ cells, we studied the functional differences between alleles in driving pancreatic cancer at various stages of progression. We found that Trp53−/− cells exhibited greater tumor initiation of preinvasive pancreatic intraepithelial neoplasia (PanINs) and early PanIN cell expansion compared to Trp53+/+ cells. Surprisingly, Trp53R172H/R172H cells were comparable in number to Trp53+/+ cells in early PanINs but were outcompeted by Trp53−/− cells.In contrast, both Trp53R172H/R172H and Trp53−/− cells were capable of facilitating the transition to advanced PDAC with comparable survival times. These phenotypic differences imply that p53R172H retains tumor suppressive properties in early pancreatic tumorigenesis, but similar to the loss of p53, it is incapable of constraining progression to advanced disease, arguing that p53R172H is a separation of function mutation in vivo. Ongoing studies examining the molecular differences between Trp53 alleles by fluorescence-activated cell sorting and RNA-sequencing will shed further light onto the underlying mechanisms that explain these phenotypic differences. Citation Format: Andy Tang, Sherry Agabiti, Hannah Chung, Mandar Deepak Muzumdar. Comparative analysis of TP53 alleles in pancreatic ductal adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1262.

Human TP53 gene polymorphisms among patients with Hepatocellular carcinoma and chronic hepatitis B infection in Kenya

Background Human TP53 is the gatekeeper for generation of human cells and is highly conserved. Some alteration/mutation in TP53 adversely affects the regulatory function of the protein, potentially resulting in cancer. This study investigated mutations in codons 72 and 249 of TP53, among patients with hepatocellular carcinoma (HCC) and chronic hepatitis B virus (HBV) infection at the Moi Teaching and Referral Hospital (MTRH), Eldoret, Kenya. Methods In total, 33 HBV-positive patients attending MTRH hospital between September 2013 and July 2017 were purposely selected from medical records for the study; those with HCC were confirmed from the cancer registry. The patients were aged between 25-67 years, with a male-to-female ratio of 1.1:1. Blood samples were collected from the patients. DNA was extracted, amplified and sequenced using TP53 forward and reverse primers. Gene mutation detection and analysis was done on exons 4 codon 72 and exon 7 codon 249. Results Of the 33 patients, 75.8% were chronically infected with HBV and had HCC; the rest were HBsAg positive without HCC. Homozygous proline was prevalent (54.5%) at exon 4 codon 72, followed by heterozygous Arg/Pro (33.3%) and lastly homozygous Arg/Arg (12.1%). Pro/Pro allele was frequent in HCC group while Arg/Arg allele was common in patients without HCC. There was no significant association between the HCC and codon polymorphisms (P=0.12). In exon 7, codon 249, 24.2% of patients had an Arg/Ser mutation of which, 75.0% had HCC and 25.0% did not. There was no significant association between HCC patients and codon 249 mutation (P=0.15). Conclusion TP53 is a gene gate keeper, the mutations under study may dependently play a role in HCC development. This study did not find any association between TP53 mutations and presence of HCC. Therefore, TP53 Arg-72 and Ser-249 mutation is not a clear prognosis indicator for hepatocellular carcinoma among HBV infected patients in Kenya.

Enhancing chimeric antigen receptor T cell therapy by modulating the p53 signaling network with Δ133p53α

Chimeric antigen receptor (CAR) T cell dysfunction is a major barrier to achieving lasting remission in hematologic cancers, especially in chronic lymphocytic leukemia (CLL). We have shown previously that Δ133p53α, an endogenous isoform of the human TP53 gene, decreases in expression with age in human T cells, and that reconstitution of Δ133p53α in poorly functional T cells can rescue proliferation [A. M. Mondal et al., J. Clin. Invest. 123, 5247-5257 (2013)]. Although Δ133p53α lacks a transactivation domain, it can form heterooligomers with full-length p53 and modulate the p53-mediated stress response [I. Horikawa et al., Cell Death Differ. 24, 1017-1028 (2017)]. Here, we show that constitutive expression of Δ133p53α potentiates the anti-tumor activity of CD19-directed CAR T cells and limits dysfunction under conditions of high tumor burden and metabolic stress. We demonstrate that Δ133p53α-expressing CAR T cells exhibit a robust metabolic phenotype, maintaining the ability to execute effector functions and continue proliferating under nutrient-limiting conditions, in part due to upregulation of critical biosynthetic processes and improved mitochondrial function. Importantly, we show that our strategy to constitutively express Δ133p53α improves the anti-tumor efficacy of CAR T cells generated from CLL patients that previously failed CAR T cell therapy. More broadly, our results point to the potential role of the p53-mediated stress response in limiting the prolonged antitumor functions required for complete tumor clearance in patients with high disease burden, suggesting that modulation of the p53 signaling network with Δ133p53α may represent a translationally viable strategy for improving CAR T cell therapy.

Inflammation status after retinal detachment could be modulate by TP53 gene

Aims/Purpose: The TP53 Arg72Pro polymorphism has been linked to the risk of proliferative vitreoretinopathy (PVR) and may alter the functional prognosis of individuals with retinal detachment (RD). The current study aims to determine the effect of the TP53 Arg72Pro variant on inflammation and apoptosis following RD.Methods: Sixty patients undergoing RD surgery were included in the study. Using the PCR‐RFLP method, the TP53 Arg72Pro polymorphism was identified in peripheral blood. A RD model was also performed in humanized TP53 Arg72Pro KI mice. In human and animal retinal tissues, mRNA expression for genes involved in inflammation and apoptosis were examined using comparative quantitative PCR (qPCR). Immunohistochemistry was performed to study the presence of glial fibrillary acidic protein (GFAP) in the mouse retina. For statistical analysis, the SPSS v15 program was employed.Results: After RD, mice with the proline mutation exhibited increased expression of the inflammatory genes TGFB1, IL1 and IL6. Additionally, after RD, the immunoexpression of retinal GFAP was also raised in the Pro variant. Carriers of the Arg/Arg mutation displayed an increase in the relative mRNA expression of the BAX and CASP3 intrinsic apoptotic genes in retinal tissue after RD in patients and mice model.Conclusions: The human TP53 Arg72Pro genetic variant has been linked to inflammation and retinal cellular death after RD, suggesting that it could be a genetic biomarker for RD prognosis.Funded: Ministerio de Ciencia e Innovación (Spain Government) (PID2020‐114585RA‐I00).

CTIM-34. JACOB: JOINT ADMINISTRATION OF CDNA FOR TP53, CHECKPOINT INHIBITION, AND BOOST/HYPO FRACTIONATED RADIATION. A PHASE 0/1 STUDY IN CHILDREN WITH RECURRENT, PROGRESSIVE, OR REFRACTORY CNS MALIGNANCIES

Abstract BACKGROUND Pediatric patients with recurrent, progressive, or refractory brain tumors have dismal prognoses and few therapeutic options. Due to the complex biological mechanisms of resistance in these tumors, targeted agents and immunotherapeutic approaches in isolation have yielded disappointing results. The combination of SGT-53, anti-PD-1, and hypofractionated radiation has shown encouraging results in preclinical studies. SGT-53 is a novel nanoparticle carrying cDNA encoding human wild-type human TP53; the nanoparticle uses a single-chain antibody fragment recognizing the human transferrin receptor, leading to excellent blood-brain barrier penetrance and anti-tumor targeting. TP53 therapy work synergistically with immune checkpoint inhibitors like anti-PD-1. Hypofractionated radiation provides additional synergy, increasing vascular access, cytokine production and activating tumor-specific T-cells. METHODS JACOB is a prospective, phase 0/1 clinical trial to evaluate the safety and efficacy of SGT-53 in combination with hypofractionated radiation and anti-PD-1 in children with recurrent, progressive, or refractory CNS malignancies. Inclusion criteria: patients age ≥ 3 and ≤ 21 years, measurable disease, performance status >50 and adequate organ function. The 3 + 3 de-escalation design will be used to determine the maximum tolerated dose (MTD) of SGT-53 in combination with ICI and radiation. Dose limiting toxicities will be evaluated. SGT-53 will be administered two times per week. Hypofractionated radiation will be given in week 2, and anti-PD-1 (once in 2 weeks) will begin on the second week of treatment. A maintenance phase of SGT-53 and anti-PD-1 will be continued for up to 12 months. Primary endpoints evaluate toxicities related to SGT-53 and plasma pharmacokinetics. Secondary and exploratory endpoints include best radiological response, and immunobiological markers. Twelve patients will be treated in the phase I/dose de-escalation cohort. After the MTD has been identified, a target validation/ phase 0 cohort will include up to 4 patients receiving 2 doses of SGT-53 prior to undergoing surgical resection to determine tissue-specific response.

TP53 germline pathogenic variants in modern humans were likely originated during recent human history.

TP53 is crucial for maintaining genome stability and preventing oncogenesis. Germline pathogenic variation in TP53 damages its function, causing genome instability and increased cancer risk. Despite extensive study in TP53, the evolutionary origin of the human TP53 germline pathogenic variants remains largely unclear. In this study, we applied phylogenetic and archaeological approaches to identify the evolutionary origin of TP53 germline pathogenic variants in modern humans. In the phylogenic analysis, we searched 406 human TP53 germline pathogenic variants in 99 vertebrates distributed in eight clades of Primate, Euarchontoglires, Laurasiatheria, Afrotheria, Mammal, Aves, Sarcopterygii and Fish, but we observed no direct evidence for the cross-species conservation as the origin; in the archaeological analysis, we searched the variants in 5031 ancient human genomes dated between 45045 and 100 years before present, and identified 45 pathogenic variants in 62 ancient humans dated mostly within the last 8000 years; we also identified 6 pathogenic variants in 3 Neanderthals dated 44000 to 38515 years before present and 1 Denisovan dated 158550 years before present. Our study reveals that TP53 germline pathogenic variants in modern humans were likely originated in recent human history and partially inherited from the extinct Neanderthals and Denisovans.

Haberlea rhodopensis alcohol extract normalizes stress-responsive transcription of the human TP53 gene

The Orpheus flower Haberlea rhodopensis (Friv.) of the family Gesneriaceae can go into anabiosis for long periods in an almost entirely desiccated state. It is an endemic relict from the Balkan Peninsula. Alcohol extracts from H. rhodopensis contain many biologically active substances with potent antioxidant, antigenotoxic, radioprotective, revitalizing and antiaging capabilities. However, regulating the gene networks responsible for these activities is vastly unknown. This study explores the cellular mechanisms underlying the protective effect of H. rhodopensis extracts (HRE). HeLa cells (human cervix epithelial carcinoma, HeLa ATCC® CCL-2™) were used as a model. We examined the changes in catalase activity and TP53 mRNA level shortly after oxidative (H2O2) and ionizing radiation (IR) induced stress with and without pre-incubation with HRE extracts. The dynamics in the activity of catalase, a main cellular antioxidant enzyme, and the expression of the stress-responsive gene TP53 were investigated by UV spectrophotometric assay and RT-qPCR, respectively. Under the applied stress conditions, H2O2 treatment and gamma radiation, catalase activity increased. This was a sign of induced ROS generation. In the first hours after treatment, the two stressors led to opposite changes in the levels of TP53 gene expression, which were alleviated by pre-incubation with HRE in a concentration-dependent manner. The broad biological activities of the studied extract, taking into account our results, show that ability of HRE to reduce the effect of stress is achieved through complex molecular mechanisms aimed at preserving cellular homeostasis. Mechanisms include the normalization of antioxidant enzyme activity such as catalase and the activity of TP53, one of the genes responsive to stress, by up or down-regulation.

Synonymous alterations of cancer-associated Trp53 CpG mutational hotspots cause fatal developmental jaw malocclusions but no tumors in knock-in mice.

Intragenic CpG dinucleotides are tightly conserved in evolution yet are also vulnerable to methylation-dependent mutation, raising the question as to why these functionally critical sites have not been deselected by more stable coding sequences. We previously showed in cell lines that altered exonic CpG methylation can modify promoter start sites, and hence protein isoform expression, for the human TP53 tumor suppressor gene. Here we extend this work to the in vivo setting by testing whether synonymous germline modifications of exonic CpG sites affect murine development, fertility, longevity, or cancer incidence. We substituted the DNA-binding exons 5-8 of Trp53, the mouse ortholog of human TP53, with variant-CpG (either CpG-depleted or -enriched) sequences predicted to encode the normal p53 amino acid sequence; a control construct was also created in which all non-CpG sites were synonymously substituted. Homozygous Trp53-null mice were the only genotype to develop tumors. Mice with variant-CpG Trp53 sequences remained tumor-free, but were uniquely prone to dental anomalies causing jaw malocclusion (p < .0001). Since the latter phenotype also characterises murine Rett syndrome due to dysfunction of the trans-repressive MeCP2 methyl-CpG-binding protein, we hypothesise that CpG sites may exert non-coding phenotypic effects via pre-translational cis-interactions of 5-methylcytosine with methyl-binding proteins which regulate mRNA transcript initiation, expression or splicing, although direct effects on mRNA structure or translation are also possible.

Abstract 45: Elephant p53 protects mice from carcinogen induced death

Abstract Elephants naturally have low rates of cancer, potentially due to evolved genetic changes in tumor suppressor elephant TP53 (EP53) and amplification of 19 TP53 retrogenes. A better understanding of the mechanisms of cancer suppression in elephants by EP53 and its retrogenes could lead to more effective human cancer therapeutics. EP53 induces a strong apoptotic response compared to human TP53, especially when combined with EP53-RETROGENE 9 (EP53-R9). EP53-R9 encodes a truncated p53 protein that induces apoptosis of human cancer cells independent of EP53 through a transcription-independent mechanism. To characterize EP53 and EP53-R9’s role in cancer suppression, transgenic mice were generated to replace mouse TRP53 with EP53. Additionally, a tetracycline inducible EP53-R9 gene was inserted into a safe harbor locus in mice. Carcinogenesis studies with 3-Methylcholanthene injection revealed that EP53 mice survived significantly longer compared to heterozygous or homozygousTRP53 mice (p &amp;lt;0.0001, 0.0102). Experiments to assess the protective role of EP53-R9 alone and combined with EP53 are ongoing. Several mouse embryonic fibroblast (MEF) cell lines were generated from these transgenic mice with 14 distinct genotypes with different combinations of TRP53, EP53, and EP53-R9. p53 target gene expression studies showed that MEFs with EP53 induce higher expression of MDM2 and p21 compared to TRP53-containing MEFs, suggesting that the cancer-protective effect observed in EP53 mice is due, in part, to greater activation of p53 signaling. These results support the need for future work to assess the potential of EP53-based therapeutics for human cancer. Citation Format: Lisa M. Abegglen, Jared S. Fowles, Aidan J. Preston, Aaron Rogers, Niraja Bhachech, Brayden B. Barney, Ryan Kennington, David H. Lum, Gareth Mitchell, Joshua D. Schiffman. Elephant p53 protects mice from carcinogen induced death [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 45.

Synthesis and Chemopreventive Potential of 5-FU/Genistein Hybrids on Colorectal Cancer Cells.

A series of 5-FU-Genistein hybrids were synthesized and their structures were elucidated by spectroscopic analysis. The chemopreventive potential of these compounds was evaluated in human colon adenocarcinoma cells (SW480 and SW620) and non-malignant cell lines (HaCaT and CHO-K1). Hybrid 4a displayed cytotoxicity against SW480 and SW620 cells with IC50 values of 62.73 ± 7.26 µM and 50.58 ± 1.33 µM, respectively; compound 4g induced cytotoxicity in SW620 cells with an IC50 value of 36.84 ± 0.71 µM. These compounds were even more selective than genistein alone, the reference drug (5-FU) and the equimolar mixture of genistein plus 5-FU. In addition, hybrids 4a and 4g induced time- and concentration-dependent antiproliferative activity and cell cycle arrest at the S-phase and G2/M. It was also observed that hybrid 4a induced apoptosis in SW620 cells probably triggered by the extrinsic pathway in response to the activation of p53, as evidenced by the increase in the levels of caspases 3/8 and the tumor suppressor protein (Tp53). Molecular docking studies suggest that the most active compound 4a would bind efficiently to proapoptotic human caspases 3/8 and human Tp53, which in turn could provide valuable information on the biochemical mechanism for the in vitro cytotoxic response of this compound in SW620 colon carcinoma cell lines. On the other hand, molecular dynamics (MD) studies provided strong evidence of the conformational stability of the complex between caspase-3 and hybrid 4a obtained throughout 100 ns all-atom MD simulation. Molecular mechanics Poisson–Boltzmann surface area (MM-PBSA) analyses of the complex with caspase-3 showed that the interaction between the ligand and the target protein is stable. Altogether, the results suggest that the active hybrids, mainly compound 4a, might act by modulating caspase-3 activity in a colorectal cancer model, making it a privileged scaffold that could be used in future investigations.

Significance of p53 and presence of differentiated vulvar intra-epithelial neoplasia (dVIN) at resection margin in early stage human papillomavirus-independent vulvar squamous cell carcinoma

ObjectiveVulvar squamous cell carcinoma and in situ lesions can be stratified by human papillomavirus (HPV) and TP53 status into prognostic risk groups using p16 and p53 immunohistochemistry. We assessed the...

Convergent evolution of a genotoxic stress response in a parasite-specific p53 homolog

P53 is a widely studied tumor suppressor that plays important roles in cell-cycle regulation, cell death, and DNA damage repair. P53 is found throughout metazoans, even in invertebrates that do not develop malignancies. The prevailing theory for why these invertebrates possess a tumor suppressor is that P53 originally evolved to protect the germline of early metazoans from genotoxic stress such as ultraviolet radiation. This theory is largely based upon functional data from only three invertebrates, omitting important groups of animals including flatworms. Previous studies in the freshwater planarian flatworm Schmidtea mediterranea suggested that flatworm P53 plays an important role in stem cell maintenance and skin production, but these studies did not directly test for any tumor suppressor functions. To better understand the function of P53 homologs across diverse flatworms, we examined the function of two different P53 homologs in the parasitic flatworm Schistosoma mansoni. The first P53 homolog (p53-1) is orthologous to S. mediterranea P53(Smed-p53) and human TP53 and regulates flatworm stem cell maintenance and skin production. The second P53 homolog (p53-2) is a parasite-specific paralog that is conserved across parasitic flatworms and is required for the normal response to genotoxic stress in S. mansoni. We then found that Smed-p53 does not seem to play any role in the planarian response to genotoxic stress. The existence of this parasite-specific paralog that bears a tumor suppressor-like function in parasitic flatworms implies that the ability to respond to genotoxic stress in parasitic flatworms may have arisen from convergent evolution.

Abstract 6184: Kras Co-mutations lead to resistance to mutant TP53 targeted therapy in mouse models of spontaneous non-small cell lung cancer

Abstract Background: Lung cancer results in more than 131,000 deaths per year with estimated 236,000 new cases in 2021 in the United States. About 85% of lung cancers are non-small cell lung cancer (NSCLC). TP53 is an important tumor-suppressor and about 50% of human lung NSCLCs contain a mutant TP53. Targeting of mutant p53 is very limited due to the lack of drugs. PRIMA-1 is a first in class anti-mutant TP53 molecule with the ability to induce apoptosis by restoring the wild-type function of TP53 through covalently binding and modifying thiol groups in the central domain of the mutated protein. Recently, the FDA granted breakthrough therapy designation to the PRIMA-1 methylated analog, APR-246 in combination with azacytidine for the treatment of patients with myelodysplastic syndromes and a TP53 mutation. The major setback of targeted therapy today continues to be resistance. Herein, we report our findings related to resistance to PRIMA-1 targeted therapy in spontaneous P53 mutant driven NSCLC. Methods: We have previously reported the generation of a line of transgenic mice with a human mutant p53(273H) expressed in a lung-specific manner. Human mutant TP53 expression was regulated under the transcriptional control of the human surfactant protein C (SP-C) promoter. After the age of 12 months, the mice developed spontaneous lung adenocarcinomas. We treated SPC-p53-273H lung tumor mice via intraperitoneal injection (i.p) with PRIMA-1 at a dose of 100 mg/kg in 0.2 mL PBS every other day for two weeks. The tumors were identified using micro-computed tomography (micro-CT) system and pre-and post-treatment diameters were estimated based on the CT image. K-ras status was analyzed by PCR-based Sanger sequencing. Results: Of the 10 lung tumor-bearing mice treated with PRIMA-1, micro-CT derived sum of the largest diameters indicated that six mice (60%) experienced tumor volume reductions whereas four mice experienced tumor volume increase. Sequencing analysis showed five tumors contained K-ras mutations (two p.G12D, one p.G12F, one p.G12V and one p.Q61L). On average, lung tumor diameter had a 31% reduction post-treatment of PRIMA-1 for the lung tumors containing wild-type K-ras gene. Whereas it increased 18% on the average post-treatment of PRIMA-1 for the lung tumors containing a mutant K-ras gene. There is a significant difference statistically (p = 0.016) in the response to the treatment of PRIMA-1 between the mutant K-ras cohort and the wild-type K-ras cohort. Conclusion: PRIMA 1 therapy results in antitumor activity against P53 mutant lung tumors. However, the presence of K-ras co-mutation is a significant resistance factor. Combination of APR-246 and K-ras inhibitor therapy would be needed to overcome this resistance. Citation Format: David T. Costa, Shaylyn Grier, Melanie Perez, Li Gao, Miguel A. Villalona-Calero, Wenrui Duan. Kras Co-mutations lead to resistance to mutant TP53 targeted therapy in mouse models of spontaneous non-small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6184.

TP53 Gene Therapy as a Potential Treatment for Patients with COVID-19

SGT-53 is a novel investigational agent that comprises an immunoliposome carrying a plasmid vector driving expression of the human TP53 gene that encodes wild-type human p53. SGT-53 is currently in phase II human trials for advanced pancreatic cancer. Although p53 is best known as a tumor suppressor, its participation in both innate and adaptive immune responses is well documented. It is now clear that p53 is an important component of the host response to various viral infections. To facilitate their viral life cycles, viruses have developed a diverse repertoire of strategies for counteracting the antiviral activities of host immune system by manipulating p53-dependent pathways in host cells. Coronaviruses reduce endogenous p53 levels in the cells they infect by enhancing the degradation of p53 in proteasomes. Thus, interference with p53 function is an important component in viral pathogenesis. Transfection of cells by SGT-53 has been shown to transiently produce exogenous p53 that is active as a pleiotropic transcription factor. We herein summarize the rationale for repurposing SGT-53 as a therapy for infection by SARS-CoV-2, the pathogen responsible for the COVID-19 pandemic. Because p53 regulation was found to play a crucial role in different infection stages of a wide variety of viruses, it is rational to believe that restoring p53 function based on SGT-53 treatment may lead to beneficial therapeutic outcomes for infectious disease at large including heretofore unknown viral pathogens that may emerge in the future.

A Systematic Review of Risk Factors for Development, Recurrence, and Progression of Vulvar Intraepithelial Neoplasia.

Vulvar intraepithelial neoplasia (VIN) is a premalignant condition with high recurrence rates despite treatment. Vulvar intraepithelial neoplasia develops through separate etiologic pathways relative to the presence or absence of human papillomavirus (HPV) and TP53 mutations. This systematic review was conducted (1) to identify historical risk factors for the development, recurrence, and progression of VIN and (2) to critique these risk factors in the context of advances made in the stratification of VIN based on HPV or TP53 status. A systematic search was performed on MEDLINE, Embase, Cochrane Database, PsychInfo, and CINAHL from inception to July 5, 2021. Three gynecologic oncologists independently evaluated the eligibility of studies based on predetermined inclusion and exclusion criteria, abstracted data, and then analyzed the relevant data. A total of 1,969 studies (involving 6,983 patients) were identified. Twenty-nine studies met inclusion criteria. The quality of evidence was low; primarily level 2b (Oxford Centre for Evidence-Based Medicine). Risk factors associated with the development of VIN include: smoking and coexisting vulvar dermatoses. Risk factors associated with recurrence include: smoking, multifocal disease, and positive surgical margins. Recent studies identified the presence of differentiated VIN/TP53 mutation as the most significant risk factor for both VIN recurrence and malignant progression. The current body of evidence consists primarily of small retrospective observational studies. Well-designed retrospective case-control series and/or prospective observational studies are urgently needed. Ideally, future studies will collect standardized data regarding associated risk factors and stratify women with VIN based on HPV and TP53 status.

Exome sequencing of hepatocellular carcinoma in lemurs identifies potential cancer drivers: A pilot study.

Background and objectivesHepatocellular carcinoma occurs frequently in prosimians, but the cause of these liver cancers in this group is unknown. Characterizing the genetic changes associated with hepatocellular carcinoma in prosimians may point to possible causes, treatments and methods of prevention, aiding conservation efforts that are particularly crucial to the survival of endangered lemurs. Although genomic studies of cancer in non-human primates have been hampered by a lack of tools, recent studies have demonstrated the efficacy of using human exome capture reagents across primates.MethodologyIn this proof-of-principle study, we applied human exome capture reagents to tumor–normal pairs from five lemurs with hepatocellular carcinoma to characterize the mutational landscape of this disease in lemurs.ResultsSeveral genes implicated in human hepatocellular carcinoma, including ARID1A, TP53 and CTNNB1, were mutated in multiple lemurs, and analysis of cancer driver genes mutated in these samples identified enrichment of genes involved with TP53 degradation and regulation. In addition to these similarities with human hepatocellular carcinoma, we also noted unique features, including six genes that contain mutations in all five lemurs. Interestingly, these genes are infrequently mutated in human hepatocellular carcinoma, suggesting potential differences in the etiology and/or progression of this cancer in lemurs and humans.Conclusions and implicationsCollectively, this pilot study suggests that human exome capture reagents are a promising tool for genomic studies of cancer in lemurs and other non-human primates.Lay SummaryHepatocellular carcinoma occurs frequently in prosimians, but the cause of these liver cancers is unknown. In this proof-of-principle study, we applied human DNA sequencing tools to tumor–normal pairs from five lemurs with hepatocellular carcinoma and compared the lemur mutation profiles to those of human hepatocellular carcinomas.