P53 Gene Mutations Research Articles

Discovery and Characterization of Brigimadlin, a Novel and Highly Potent MDM2-p53 Antagonist Suitable for Intermittent Dose Schedules.

p53 is known as the guardian of the genome and is one of the most important tumor-suppressors. It is inactivated in most tumors, either via tumor protein p53 (TP53) gene mutation or copy number amplification of key negative regulators, e.g., mouse double minute 2 (MDM2). Compounds that bind to the MDM2 protein and disrupt its interaction with p53 restore p53 tumor suppressor activity, thereby promoting cell cycle arrest and apoptosis. Previous clinical experience with MDM2-p53 protein-protein interaction antagonists (MDM2-p53 antagonists) have demonstrated that thrombocytopenia and neutropenia represent on-target dose-limiting toxicities that might restrict their therapeutic utility. Dosing less frequently, while maintaining efficacious exposure, represents an approach to mitigate toxicity and improve the therapeutic window of MDM2-p53 antagonists. However, to achieve this, a molecule possessing excellent potency and ideal pharmacokinetic properties is required. Here, we present the discovery and characterization of brigimadlin (BI 907828), a novel, investigational spiro-oxindole MDM2-p53 antagonist. Brigimadlin exhibited high bioavailability and exposure, as well as dose-linear pharmacokinetics in preclinical models. Brigimadlin treatment restored p53 activity and led to apoptosis induction in preclinical models of TP53 wild-type, MDM2-amplified cancer. Oral administration of brigimadlin in an intermittent dosing schedule induced potent tumor growth inhibition in several TP53 wild-type, MDM2-amplified xenograft models. Exploratory clinical pharmacokinetic studies (NCT03449381) showed high systemic exposure and a long plasma elimination half-life in cancer patients who received oral brigimadlin. These findings support the continued clinical evaluation of brigimadlin in patients with MDM2-amplified cancers, such as dedifferentiated liposarcoma.

Dehydroepiandrosterone suppresses human colorectal cancer progression through ER stress-mediated autophagy and apoptosis in a p53-independent manner.

Colorectal cancer (CRC) is one of the primary contributors to cancer-related fatalities, with up to 80% of advanced CRC cases exhibiting mutations in the p53 gene. Unfortunately, the development of new compounds targeting mutant p53 is quite limited. The anticancer effects of Dehydroepiandrosterone (DHEA) on various cancers have been reported. However, the suppressive effect of DHEA on CRC cells harboring wild-type or mutant p53 gene remains controversial. This study emphasized revealing the suppressive mechanism and the effect of DHEA on CRC cell tumorigenesis in the presence of wild-type or mutant p53 gene. We demonstrate that DHEA causes CRC cell death and cell cycle arrest in a dose and time-dependent manner. Notably, DHEA exhibits similar inhibitory effects on CRC cells regardless of the p53 gene status. Further study reveals that DHEA induces endoplasmic reticulum (ER) stress and triggers PERK/eIF2/ATF4/CHOP UPR signaling pathway to activate autophagy followed by apoptosis, which was confirmed by suppression of 4-phenylbutyric acid (an ER stress inhibitor) or knockdown either ATF4 or CHOP. DHEA-induced apoptosis was attenuated by silencing ATG5 gene in either p53+/+ or p53-/- CRC cells, indicating autophagy regulation of apoptosis. Furthermore, DHEA treatment accompanied by bafilomycin A1 (a blocker of autophagosome degradation) leads to the accumulation of ATF4, CHOP, DR5, and p21 levels in CRC cells, implying that the degradative autophagy machinery regulates these four molecules. Consistently, DHEA demonstrates its inhibitory effect by suppressing CRC tumor formation in vivo. Altogether, we provide compelling evidence that DHEA is a potential therapeutic candidate for CRC patient treatment regardless of the p53 status through ER stress-PERK-autophagy-apoptosis axis.

Elacestrant in ER+, HER2- Metastatic Breast Cancer with ESR1-Mutated Tumors: Subgroup Analyses from the Phase III EMERALD Trial by Prior Duration of Endocrine Therapy plus CDK4/6 Inhibitor and in Clinical Subgroups.

Elacestrant significantly prolonged progression-free survival (PFS) with manageable safety versus standard-of-care (SOC) endocrine therapy (ET) in patients with estrogen receptor-positive (ER+), HER2- metastatic breast cancer and tumors harboring estrogen receptor 1 (ESR1) mutation following ET plus a cyclin-dependent kinase 4/6 inhibitor (ET+CDK4/6i). In patients with ESR1-mutated tumors, we evaluated the efficacy and safety of elacestrant versus SOC based on prior ET+CDK4/6i duration and in clinical subgroups with prior ET+CDK4/6i ≥12 months. EMERALD, an open-label phase III trial, randomly assigned patients with ER+, HER2- metastatic breast cancer who had received 1-2 prior lines of ET, mandatory CDK4/6i, and ≤1 chemotherapy to elacestrant (345 mg daily) or SOC (aromatase inhibitor or fulvestrant). PFS was assessed across subgroups in post hoc exploratory analyses without adjustment for multiple testing. In patients with ESR1-mutated tumors and prior ET+CDK4/6i ≥12 months, the median PFS for elacestrant versus SOC was 8.6 versus 1.9 months (HR, 0.41; 95% confidence interval, 0.26-0.63). In this population, the median PFS (in months) for elacestrant versus SOC was 9.1 versus 1.9 (bone metastases), 7.3 versus 1.9 (liver and/or lung metastases), 9.0 versus 1.9 (<3 metastatic sites), 10.8 versus 1.8 (≥3 metastatic sites), 5.5 versus 1.9 (PIK3 catalytic subunit α mutation), 8.6 versus 1.9 (tumor protein p53 gene mutation), 9.0 versus 1.9 (HER2-low), 9.0 versus 1.9 (ESR1D538G-mutated tumors), and 9.0 versus 1.9 (ESR1Y537S/N-mutated tumors). Subgroup safety was consistent with the overall population. The duration of prior ET+CDK4/6i ≥12 months in metastatic breast cancer was associated with a clinically meaningful improvement in PFS for elacestrant compared with SOC and was consistent across all subgroups evaluated in patients with ER+, HER2-, ESR1-mutated tumors.

Association of P53 Gene and Colorectal Cancer in Iran

Background: Colorectal cancer (CRC) is one of the leading causes of malignancies globally with a high mortality rate. Therefore, investigating the underlying mechanism and different risk factors contributing to this neoplasm is imperative, since P53 protein is a tumor suppressor protein, that has inhibiting effect on tumorigenesis, this study aims to assess the association of P53 gene and CRC within specific population, as geography is believed to be a risk factor for CRC. Materials and Methods: In this retrospective case-control study, 90 patients aged 18 years old and above, with CRC were enrolled. They were all scrutinized before and after their surgery. Data were extracted from their medical record, laboratory test results, standard questionnaire, imaging reports, physical exam, related symptoms and colonoscopy and biopsy reports. Data analysis was performed using SPSS software and the chi-square method. Results: 90 patients participated in this study, with the mean age of 71.57 years. There was no statistically significant association between age of patients and P53 mutation. Similarly, no correlation between any of the symptoms and P53 gene mutation was found. However, the risk of P53 mutation increased with larger tumor size (p&lt;0.021), deeper tissue invasion (p&lt;0.041) and higher levels of lymph node involvement (p&lt;0.031). Conclusion: this study investigates the relationship between P53 mutation and various clinical and pathological parameters. A significant association was observed between P53 mutation and tumor characteristics, including larger tumor size, deeper tissue invasion, and increased lymph node involvement. These findings suggest that P53 mutation may serve as a potential biomarker for assessing tumor aggressiveness and prognosis in colorectal cancer

The role of P53 gene and p53 protein in non-Hodgkin malignant lymphoma.

TPS177 Background: Background and study aim P53 gene mutations are the most common genetic abnormalities of cancer. They have been extensively studied in various mature B-cell malignancies, including chronic lymphocytic leukemia (CLL). In recent years, more attention has been paid to the importance of the p53-expressed protein in CLL, and a combination with low survival and non-response to classical conventional chemotherapy, due to mutations in the p53 gene, with progression to Richter Syndrome. Identifying different p53 gene mutations is very important because these mutations have an impact on the patient's clinical course in CLL. Methods: The frequency of p-53 protein expression in 85 patients diagnosed with CLL was analyzed by the Enzyme-Linked Immune-Absorbent Assay (ELISA) technique to investigate the relationship of this protein to the stage of the disease, as well as the impact on response to treatment and survival. Cell extracts 10³×10³/L in 100 μl lysis buffer were applied to ELISA plates coated with PAb 240 capture antibody. Clinical trial information: ISRCTN12539707 .

Li-Fraumeni Syndrome: Imaging Features and Guidelines.

Li-Fraumeni syndrome (LFS) is a rare autosomal dominant familial cancer syndrome caused by germline mutations of the tumor protein p53 gene (TP53), which encodes the p53 transcription factor, also known as the "guardian of the genome." The most common types of cancer found in families with LFS include sarcomas, leukemia, breast malignancies, brain tumors, and adrenocortical cancers. Osteosarcoma and rhabdomyosarcoma are the most common sarcomas. Patients with LFS are at increased risk of developing early-onset gastric and colon cancers. They are also at increased risk for several other cancers involving the thyroid, lungs, ovaries, and skin. The lifetime risk of cancer in individuals with LFS is greater than 70% in males and greater than 90% in females. Some patients with LFS develop multiple primary cancers during their lifetime, and guidelines have been established for screening these patients. Whole-body MRI is the preferred modality for annual screening of these patients. The management guidelines for patients with LFS vary, as these individuals are more susceptible to developing radiation-induced cancers-for example, women with LFS and breast cancer are treated with total mastectomy instead of lumpectomy with radiation to the breast. The authors review the role of imaging, imaging guidelines, and imaging features of tumors in the setting of LFS. ©RSNA, 2024 Supplemental material is available for this article.

Advances in Targeted Therapy of Non-small Cell Lung Cancer with EGFR Combined With P53 Gene Mutation

Non-small cell lung cancer (NSCLC) is currently the leading cause of cancer death worldwide. NSCLC patients with epidermal growth factor receptor (EGFR) mutations were treated with EGFR-tyrosine kinase inhibitor (TKI), but EGFR mutations combined with other genes had a shorter survival. However, the P53 gene mutation is a common combined mutation in patients with NSCLC with EGFR gene mutation. This review summarizes the development of targeted NSCLC for EGFR with P53 mutations.

Monocyte infiltration is an independent positive prognostic biomarker in vulvar squamous cell carcinoma

BackgroundVulvar squamous cell carcinoma (VSCC) arises after an HPV infection or the mutation of p53 or other driver genes and is treated by mutilating surgery and/or (chemo) radiation, with limited success and high morbidity. In-depth information on the immunological make up of VSCC is pivotal to assess whether immunotherapy may form an alternative treatment.MethodsA total of 104 patient samples, comprising healthy vulva (n = 27) and VSCC (n = 77), were analyzed. Multispectral immunofluorescence (15 markers) was used to study both the myeloid and lymphoid immune cell composition, and this was linked to differences in transcriptomics (NanoString nCounter, 1258 genes) and in survival (Kaplan–Meier analyses).ResultsHealthy vulva and VSCC are both well infiltrated but with different subpopulations of lymphoid and myeloid cells. In contrast to the lymphoid cell infiltrate, the density and composition of the myeloid cell infiltrate strongly differed per VSCC molecular subtype. A relative strong infiltration with epithelial monocytes (HLADR−CD11c−CD14+CD68−CD163−CD33−) was prognostic for improved survival, independent of T cell infiltration, disease stage or molecular subtype. A strong infiltration with T cells and/or monocytes was associated with drastic superior survival: 5-year survival > 90% when either one is high, versus 40% when both are low (p < 0.001).ConclusionA hot myeloid and/or lymphoid infiltrate predicts excellent survival in VSCC. Based on the response of similarly high-infiltrated other tumor types, we have started to explore the potential of neoadjuvant checkpoint blockade in VSCC.

Disrupting the interaction between a p53 gain-of-function mutant and the transcriptional co-activator PC4 reverses drug resistance in cancer cells.

PC4 is a chromatin-associated protein and transcriptional coactivator whose role in gene regulation by wild-type p53 is now well known. Little is known about the roles of PC4 in tumor cells bearing mutant p53 genes. We show that PC4 associates with one of the tumor-associated gain-of-function p53 mutants, R273H. This association drives its recruitment to two promoters, UBE2C and MDR1, known to be responsible for imparting aggressive growth and resistance to many drugs. Here, we introduced a peptide that disrupts the PC4-R273Hp53 interaction to tumor cells bearing the R273HTP53 gene, which led to a lowering of MDR1 expression and abrogation of drug resistance in a mutant-specific manner. The results suggest that the PC4-R273Hp53 interaction may be a promising target for reducing proliferation and drug resistance in tumors.

Abstract 1985: Ablation of adenylosuccinate lyase retarded the cell proliferation and induces mitochondrial dysfunction in endocrine therapy resistant breast cancer cells

Abstract Approximately 75% of breast tumors express estrogen receptors (ER+); recurrent ER+ breast cancer is generally incurable. Endocrine therapy (ET) is the mainstay of treatment for ER+ breast cancer and works by targeting either ER activity (Tamoxifen or Fulvestrant) or availability of its ligand estrogen (Letrozole, Exemestane). Unfortunately, endocrine therapies are limited by the emergence of resistance; resistance to endocrine therapies (ET) remains a significant clinical challenge. We have explored the role of adenylosuccinate lyase (ADSL), an enzyme of the de-novo purine biosynthesis pathway, in ET-resistant breast cancer cells. Protein expression of ADSL was significantly higher in two different ET-resistant cells (LCC9 and T47D-4HT) when compared with their respective parental ET-sensitive cells (MCF-7 and T47D). siRNA mediated ablation of ADSL in LCC9 and T47D-4HT cells blocked cell proliferation and both colony and spheroid formation. Depletion of ADSL in LCC9 cells obstructed cell cycle progression from G1 to S phase and elevated the protein expression of cyclin D1/D3, CDK2/4, and cyclin E. In T47D-4HT cells, ADSL depletion led to an accumulation of cells in S-phase with reduced protein expression of cyclin D1. Notably, ADSL ablation in LCC9 cells lead to DNA replication stress, resulting in activation (phosphorylation) of ataxia-telangiectasia-mutated-and-Rad3-related kinase (ATR) and its key downstream effector checkpoint kinase 1 (Chk1), which further limited the phosphatase activity of cdc25A leading to deactivation (phosphorylation) of Cyclin-Dependent Kinase 2 (CDK2). ADSL knockdown reduced the mitochondrial membrane potential and impaired the oxygen consumption (OCR) and extracellular acidification (ECAR) rates in both LCC9 and T47D-4HT cells. Of note, addition of AICAR to ADSL-depleted LCC9 cells significantly increased cell proliferation, colony formation, and restored mitochondrial membrane potential. RNA sequencing data revealed the effect of ADSL depletion on enrichment of different pathways in LCC9 and TH47D-4HT cells. Importantly, p53 signaling was significantly enriched in LCC9 cells but not in T47D-4HT cells after ADSL knockdown (T47D cells have a mutated p53 gene). ER+ breast cancer patients treated with ET showed high ADSL expression that is associated with poor recurrence-free survival. In summary, our findings indicate that ADSL-mediated de novo purine synthesis is crucial for cell proliferation. Therefore, targeting ADSL may be a novel therapeutic approach for ER, ET-resistant breast cancer. Citation Format: ANIL KUMAR Yadav, Lu Jin, Robert Clarke, Surojeet Sengupta. Ablation of adenylosuccinate lyase retarded the cell proliferation and induces mitochondrial dysfunction in endocrine therapy resistant breast cancer 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 1985.

Abstract 3911: A FGFR-p53 developmental signaling axis drives progression of salivary cancer

Abstract Mucoepidermoid carcinoma (MEC) is the most frequently occurring salivary gland (SG) malignancy. Treatments for high grade (HG) MEC are lacking due to a limited understanding of its diverse histological and clinical features. Consequently, patients with non-resectable HG MEC are often treated with adjuvant radiotherapy and suffer from increased rates of recurrence and metastasis with poor 5-year survival rates (30-50%) as compared to low grade (LG) MEC (76-95%). We previously demonstrated a role for IGF-1 signaling, an important mediator for SG development and branching morphogenesis, in MEC pathogenesis (Musicant et al, 2021). Here, we analyzed transcriptome profiles shared between fetal and adult normal parotid (PAR) tissues with MEC tumors to investigate programs involved in MEC progression. Using this information, we developed the first genetically engineered mouse model (GEMM) of advanced HG MEC via targeted oncogene expression in SG ductal cells. MEC samples from 21 PAR tumors (8 LG/13 HG), 8 age-matched normal, and 3 fetal PAR glands aged between 22-24 weeks of gestation (Saitou et al, 2020) were retrospectively collected from UCSF or UNC Surgical Pathology. RNAseq was performed on FFPE samples using Illumina HiSeq. Differential gene expression, gene set enrichment analyses (GSEA), and alternative splicing analyses were compared between fetal/normal/MEC according to tumor grade and CRTC1 (CREB-regulated transcription coactivator 1)/MAML2 (Mastermind-like 2) (C1/M2) status. Based on these analyses, we developed a GEMM combining C1/M2 expression with TP53 loss. GEMM tumors were subjected to RNAseq and reviewed by two independent pathologists for diagnostic confirmation of HG MEC.GSEA revealed significant overlap between MEC tumors and fetal SG for genes governing proliferation and developmental pathways associated with branching morphogenesis. Interestingly, upregulation of the negatively regulated p53 target FOXM1 along with a mutant-p53 gene signature (Troester et al, 2006) revealed that p53 dysregulation in HG tumors phenocopies that seen in fetal SG. Cre-inducible expression of C1/M2 alone was insufficient to induce MEC-like lesions when targeted to distinct salivary cell types (ductal Krt14-CreER, acinar Mist1-CreER, serous demilune Dcpp1-CreER). However, p53 alteration (Tp53KO) with ductal C1/M2 expression drove MEC formation with histological and molecular features of human HG-MEC. Notably, transcriptome profiles implicate an FGFR-p53 developmental signaling axis in MEC progression. Our autochthonous GEMM recapitulates advanced HG-MEC in vivo providing the field with a powerful platform for identifying pathways for developing targeted therapies. Taken together, the integrated bioinformatics and mouse modeling of this study provide a critical step toward elucidating salivary MEC progression and suggest a role for FGFR targeted therapies in the treatment of non-resectable HG MEC. Citation Format: Julia M. Billington, Adele M. Musicant, Jessica L. Cote, Jennifer Modliszewski, Yi-Hsuan Tsai, Luane J. Landuau, John Powers, Renee Betancourt, Radhika Sekhri, Ricardo J. Padilla, Juan C. Hernandez-Prera, David N. Hayes, Trevor G. Hackman, Omer Gokcumen, Sarah M. Knox, Jimena Guidice, Antonio L. Amelio. A FGFR-p53 developmental signaling axis drives progression of salivary cancer [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 3911.

Prognostic significance of tumor suppressor protein p53 in prostate cancer.

The p53 gene mutation is one of the most common genetic alterations in many cancers. In prostate cancer (PCa), it has been associated with a poor prognosis, tumor progression and aggressiveness. P53 mutation induces an abnormal protein expression in related tissues. This study aimed to assess p53 expression using immunohistochemistry in PCa and to discuss its prognostic value. We have retrospectively collected all cases of PCa diagnosed in our pathology department between 2012 and 2022. An automatized immunohistochemical analysis was performed using monoclonal p53 antibody. For each case, we assessed the proportion of positive cells and the intensity of staining. P53 expression was considered abnormal when it was totally negative or overexpressed (>=50% of positive cells). Twenty-four cases have been selected. Abnormal p53 expression was found in 42% of cases (P53 was overexpressed in 6cases and totally negative in 4 cases). Mean age of patients with p53 abnormal expression was 70years old. Patients with p53 abnormal expression had Gleason score >7 in 5 cases, ISUP grade >2 in 3 cases, peri-neural invasion in 8cases, capsule invasion in 9cases. All patients with p53 overexpression developed androgen resistance (p<0.01). An aberrant expression profile of the p53 protein was observed in 42% of cases, and a statistically significant association was found with androgen resistance. Our results suggest a potential prognostic role of p53 in PCa.

KRAS and P53 Gene Mutation Patterns Linked to Colorectal Cancer in Sudan

Background: Molecular pathogenesis of CRC represents a major target for understanding and controlling of the disease in the Sudan. Therefore, the present study aimed to explore the clinicopathological pattern of CRC in the Sudan with specific emphases in the role KRAS and P53 genes mutations. Methodology: This study was carried out in El-Obeid, North Kordofan state, Sudan, using CRC samples from patients who presented to the Al-Obeid teaching hospital between 2017 and 2022 and had a biopsy for histopathological diagnosis. This series featured everyone who has CRC. Results: The most prevalent CRC subtype is adenocarcinoma, which is followed by mucinous adenocarcinoma and metastatic adenocarcinoma, which constitute 74%, 20%, and 6%, respectively. KRAS mutation was found in 40% patients 48% males and 33.3% females). P53 mutation was found in 46% individuals 43.5% men and 48% females. Positive correlations between KRAS and P53 were found in 26% cases, while negative correlations were found in 40% cases. Conclusion: Many CRC patients in Sudan present at advanced stages of the illness and at a younger age, necessitating early screening measures. CRC patients have been discovered to have KRAS, P53, or both mutations. As a result, precise preventative and therapeutic methods are considered essential.

Abstract C116: Oncogenic Kras signaling shapes the tumor microenvironment in lung adenocarcinoma

Abstract Despite advancements in targeted therapy and immunotherapy, lung cancer remains the leading cause of cancer-related deaths in both men and women worldwide, with an estimated 2.2 million deaths each year. At 85%, non-small cell lung cancer (NSCLC) is by far the most common subtype, comprising adenocarcinomas and lung squamous cell carcinoma. Mutations in Kirsten rat sarcoma viral oncogene homolog (KRAS), epidermal growth factor receptor (EGFR) and anaplastic lymphoma receptor tyrosine kinase (ALK) genes are common, with the worst overall survival in KRAS mutant adenocarcinoma patients. About 40% of lung tumors with KRAS mutations also harbor mutations in tumor protein p53 gene (TP53), a tumor suppressor gene. KrasG12C and KrasG12D are both prevalent mutations in lung cancer. Sotorasib, a KrasG12C inhibitor, was recently approved for treatment of NSCLC. However, only 37% of patients have an objective response to Sotorasib, with a median duration of just 11 months. The KrasG12D inhibitor MRTX1133 is entering clinical trials; elucidating the mechanism of action and potential resistance is imperative to design combination treatment approaches. While cell-intrinsic mechanisms of resistance in epithelial oncogenic KRASG12D (Kras*) are well studied, our group and others have shown that KRASG12D also extrinsically regulates the tumor microenvironment (TME) in pancreatic cancer. Whether and how this oncogene regulates the TME of lung cancer is less understood. To study the crosstalk between epithelial lung cells expressing oncogenic KRAS and the surrounding TME, we have established a triple transgenic murine model of Kras*-driven NSCLC, wherein both lung epithelial-specific expression of Kras* and expression of mutant TP53R172H (Tp53*) can be controlled in an inducible and reversible manner. Our preliminary data show that expression of Kras* drives tumor growth, while Kras* depletion results in regression, even in the presence of Tp53*. Here we interrogate how Kras* modulates the TME in lung adenocarcinomas. Harnessing scRNA sequencing, immunohistochemistry, and multiple biochemical approaches, we will provide insight into changes in stromal and immune contexture upon Kras* depletion in mice. Citation Format: Rachael Baliira, Emily Lasse Opsahl, Ivana Barravecchia, Marina Pasca di Magliano, Stefanie Galban. Oncogenic Kras signaling shapes the tumor microenvironment in lung adenocarcinoma [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr C116.

Cell proliferation and apoptosis in canine oral papillomatosis.

This study was aimed at the evaluation of cell proliferation, p53 level and apoptotic index by immunohistochemical methods in canine oral papillomatosis. The study material comprised of tumor tissue samples taken from six dogs being admitted to the Pathology Department of Faculty of Veterinary Medicine, Kafkas University, Kars, Türkiye. Choice of immunohistochemical staining was avidin-biotin peroxidase method.Cases of canine oral papillomatosis, determined to have been caused by canine papillomavirus-1, were found to have a rather high cell proliferation index. Furthermore, all cases were immunohisto-chemically demonstrated to carry a mutant p53 gene. Despite the mutation of p53 gene, the shift in the Bax/Bcl-2 ratio of dogs diagnosed with tumor was in favor of the pro-apoptotic Bax gene. The apoptotic mechanism was determined to occur through both the caspase-dependent and caspase-independent pathways. While the lesions occupied the entire oral cavity in some cases, histopathologically, malignant transformation was not detected in any of the six cases.

Clinicohistopathological Features and Immunohistochemical Expression Patterns of p53 in Epithelial Ovarian Tumours: A Cross-sectional Study

Introduction: Ovarian tumours represent 3% of female malignancies, with epithelial tumours constituting more than 90% of all ovarian cancers. Tumour suppressor gene 53 (TP53) mutations play an important role in the prognosis and treatment of ovarian cancer. The tumour suppressor gene Tumour Protein 53 (p53), located on the short arm of chromosome 17, acts by suppressing abnormal cell growth at the beginning of the Synthesis phase (S-phase) of the cell cycle. Previous studies have shown a correlation between p53 mutation or overexpression and patient prognosis in various types of tumours, including breast cancer, rectal cancer, intestinal cancer, lung cancer, and ovarian cancer. Aim: To investigate the clinicohistopathological features and immunohistochemical expression of p53 in Epithelial Ovarian Tumours (EOT). Materials and Methods: A cross-sectional study was conducted in the Department of Pathology at Hind Institute of Medical Sciences, Barabanki, Uttar Pradesh, India. The duration of the study was one year and two months, from September 2021 to November 2022. A total of 80 cases of EOT were included and histopathological diagnosis was performed, and immunohistochemical expression of p53 was evaluated in all cases. The Chi-square test was used to compare categorical data (the number of benign, borderline, and malignant EOT) and determine whether the difference in p53 expression (positive or negative) was statistically significant, using Statistical Package for the Social Sciences (SPSS) version 26.0. Results: The total of 80 cases of EOT in the present study comprised 56 (70%) benign, 5 (6.25%) borderline, and 19 (23.75%) malignant tumours. The p53 expression was statistically significant. Immunohistochemistry (IHC) for p53 showed diffuse strong positive nuclear staining (&gt;60%) of the tumour cells in 14 cases, all of which were malignant epithelial tumours. Focally weak and patchy positive nuclear staining patterns (5%-60%) were observed in 64 cases, including 56 benign cases, four borderline cases, and four cases of malignant epithelial tumours, respectively. p53 positivity (&lt;5% staining of tumour cells) was seen in two cases, one each of borderline and malignant epithelial tumour, respectively. Conclusion: The IHC marker p53 serves as a surrogate marker for p53 gene mutation, and its positivity is observed in serous EOT. Understanding p53 staining patterns can be used in conjunction with a panel of other antibodies to correctly classify morphologically confusing EOT. This can aid in assessing prognosis and understanding the biological behaviour of the tumour, which can be helpful in modifying the treatment plan.

MRI-based model for accurate prediction of P53 gene status in gliomas

&lt;abstract&gt; &lt;p&gt;The accurate diagnosis and treatment of gliomas depends largely on the understanding of the P53 gene status. In our study, we presented a robust deep learning model, CTD-RegNet (improved RegNet integrating CNN, vision transformer, and truth discovery), tailored for predicting P53 gene status in gliomas. Our model addressed common challenges of existing deep learning models, such as incomplete feature extraction and uncertainty. First, the model used the RegNet network as a basis for predicting P53 gene mutations by skillfully extracting heterogeneous features. Next, the RegNet network was enhanced by integrating the CNN and ViT modules to optimise feature extraction and computational efficiency. Finally, using the truth discovery algorithm, we iteratively refined model uncertainties, thereby improving prediction accuracy. Our experiments demonstrated the effectiveness of the CTD-RegNet model, achieving an impressive accuracy of 95.57% and an AUC score of 0.9789, outperforming existing P53 gene status prediction models. The non-invasive nature of our model minimised the economic burden and physical and psychological stress on patients, while providing critical insights for accurate clinical diagnosis and treatment of gliomas.&lt;/p&gt; &lt;/abstract&gt;

Clinical and molecular profiling of EGFR-mutant lung adenocarcinomas transformation to small cell lung cancer during TKI treatment.

Small cell lung cancer (SCLC) transformation serves as a significant mechanism of resistance to tyrosine kinase inhibitors (TKIs) in advanced non-small cell lung cancer (NSCLC) with epidermal growth factor receptor (EGFR) mutations. To address this clinical challenge, we conducted a retrospective analysis at Zhejiang University School of Medicine, the First Affiliated Hospital, focusing on patients with EGFR sensitizing mutations. A total of 1012 cases were included in this retrospective analysis. The cohort primarily consisted of patients with EGFR sensitizing mutations. Biopsy-confirmed small cell transformation was observed in seven patients, accounting for 0.7% of the cases. All patients in this subset were initially diagnosed with stage IV adenocarcinoma (ADC), with four cases classified as poorly differentiated and three as moderately to poorly differentiated ADC. EGFR exon 19 deletions were identified in five of these cases. Next-generation sequencing (NGS) was performed on seven cases, revealing mutations in the tumor protein p53 (TP53) gene in four cases and loss of the retinoblastoma1 (RB1) gene in three cases. The median duration from the initial diagnosis to small cell transformation was 35.9 months (interquartile range: 12.1-84 months). Following small cell transformation during EGFR inhibition, all patients received etoposide/platinum-based treatment, leading to a median progression-free survival (PFS) of 4.7 months (interquartile range: 2.7-10.1 months). Notably, most patients in this series had poorly differentiated adenocarcinomas at the outset. TP53 mutations and RB1 loss were common genetic alterations observed in patients with small cell transformation in this cohort. The findings underscore the clinical significance of SCLC transformation as a resistance mechanism to EGFR TKIs in NSCLC with EGFR mutations. The observed genetic alterations, including TP53 mutations and RB1 loss, suggest potential associations with the transformation process and warrant further investigation. Understanding the genetic landscape and clinical outcomes in patients experiencing small cell transformation can contribute to improved strategies for managing resistance in EGFR-mutant NSCLC.

Abstract B039: T cell recruitment dynamics at different stages of primary and metastatic colorectal cancer

Abstract Colorectal cancer (CRC) is the fourth deadliest cancer worldwide, primarily due to metastasis. The current standard therapy for patients with CRC includes neoadjuvant therapies combined with surgery, often resulting in severe complications that affect patients’ lifestyles. Hence, there is a critical need to improve our understanding of the tumor microenvironment to improve the current therapeutics for metastatic CRC. We characterized T cell dynamics in response to tumors at early (1-2 weeks) versus late stages (6-7 weeks) of CRC development in different colon compartments (tumor, epithelium, lamina propria), as well as in colon-draining lymph nodes and the liver as potential metastasis sites. To achieve this, we injected by colonoscopy tumor AKP mouse organoids (mutations in APC, Kras, and P53 genes) or metastatic AKP mouse organoids in the colon walls of a novel fate-mapping strain (iSell-tomato). This model allows for the labelling of peripheral T cells that are recruited to the tissue or tumor sites. Our initial data showed an enhanced recruitment of CD4 and CD8ab T cells to the colon epithelium in early stage AKP (non-metastatic) tumor models compared to late-stage AKP and metastatic-AKP models at both stages. These recruited cells exhibited an enhanced anti-tumorigenic profile characterized by the production of IFNg and reduced frequency of FoxP3+ CD4 regulatory T cells (Tregs). In contrast, T cells recruited to early stage metastatic-AKP tumors and late-stage tumors of the colon and liver exhibited enhanced exhaustion characterized by an increased frequency of PD1+ CD4 and CD8ab T cells. These data suggest a time- and aggressiveness-dependent effect of tumors on immune cell infiltrates that, in turn, affect tumor progression and metastasis. Citation Format: Marwa A Saad, Angelina Bilate, Daniel Mucida. T cell recruitment dynamics at different stages of primary and metastatic colorectal cancer [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor Immunology and Immunotherapy; 2023 Oct 1-4; Toronto, Ontario, Canada. Philadelphia (PA): AACR; Cancer Immunol Res 2023;11(12 Suppl):Abstract nr B039.

ROCK inhibition reduces the sensitivity of mutant p53 glioblastoma to genotoxic stress through a Rac1-driven ROS production.

Resistance to radio and chemotherapy in Glioblastoma (GBM) is correlated with its malignancy, invasiveness, and aggressiveness. The Rho GTPase pathway plays important roles in these processes, but its involvement in the GBM response to genotoxic treatments remains unsolved. Inhibition of this signaling pathway has emerged as a promising approach for the treatment of CNS injuries and diseases, proving to be a strong candidate for therapeutic approaches. To this end, Rho-associated kinases (ROCK), classic downstream effectors of small Rho GTPases, were targeted for pharmacological inhibition using Y-27632 in GBM cells, expressing the wild-type or mutated p53 gene, and exposed to genotoxic stress by gamma ionizing radiation (IR) or cisplatin (PT). The use of the ROCK inhibitor (ROCKi) had opposite effects in these cells: in cells expressing wild-type p53, ROCKi reduced survival and DNA repair capacity (reduction of γH2AX foci and accumulation of strand breaks) after stress promoted by IR or PT; in cells expressing the mutant p53 protein, both treatments promoted longer survival and more efficient DNA repair, responses further enhanced by ROCKi. The target DNA repair mechanisms of ROCK inhibition were, respectively, an attenuation of NHEJ and NER pathways in wild-type p53 cells, and a stimulation of HR and NER pathways in mutant p53 cells. These effects were accompanied by the formation of reactive oxygen species (ROS) induced by genotoxic stress only in mutant p53 cells but potentiated by ROCKi and reversed by p53 knockdown. The p53-dependent actions of ROCKi were completely abolished by N-acetyl-L-cysteine (NAC) treatment or Rac1 knockdown, as Rac-GTP levels were specifically elevated by ROCK inhibition only in mutant p53 cells. Combining IR or PT and ROCKi treatments broadens our understanding of the sensitivity and resistance of, respectively, GBM expressing wild-type or mutant p53 to genotoxic agents. Our proposal may be a determining factor to improve the efficiency and assertiveness of CNS antitumor therapies based on ROCK inhibitors. SIGNIFICANCE: The use of ROCK inhibitors in association with radio or chemotherapy modulates GBM resistance and sensitivity depending on the p53 activity, suggesting the potential value of this protein as therapeutic target for tumor pre-sensitization strategies.