Reactivation Of P53 Research Articles

Rescue of p53 functions by in vitro-transcribed mRNA impedes the growth of high-grade serous ovarian cancer.

The cellular tumor protein p53 (TP53) is a tumor suppressor gene that is frequently mutated in human cancers. Among various cancer types, the very aggressive high-grade serous ovarian carcinoma (HGSOC) exhibits the highest prevalence of TP53 mutations, present in >96% of cases. Despite intensive efforts to reactivate p53, no clinical drug has been approved to rescue p53 function. In this study, our primary objective was to administer in vitro-transcribed (IVT) wild-type (WT) p53-mRNA to HGSOC cell lines, primary cells, and orthotopic mouse models, with the aim of exploring its impact on inhibiting tumor growth and dissemination, both in vitro and in vivo. To restore the activity of p53, WT p53 was exogenously expressed in HGSOC cell lines using a mammalian vector system. Moreover, IVT WT p53 mRNA was delivered into different HGSOC model systems (primary cells and patient-derived organoids) using liposomes and studied for proliferation, cell cycle progression, apoptosis, colony formation, and chromosomal instability. Transcriptomic alterations induced by p53 mRNA were analyzed using RNA sequencing in OVCAR-8 and primary HGSOC cells, followed by ingenuity pathway analysis. In vivo effects on tumor growth and metastasis were studied using orthotopic xenografts and metastatic intraperitoneal mouse models. Reactivation of the TP53 tumor suppressor gene was explored in different HGSOC model systems using newly designed IVT mRNA-based methods. The introduction of WT p53 mRNA triggered dose-dependent apoptosis, cell cycle arrest, and potent long-lasting inhibition of HGSOC cell proliferation. Transcriptome analysis of OVCAR-8 cells upon mRNA-based p53 reactivation revealed significant alterations in gene expression related to p53 signaling, such as apoptosis, cell cycle regulation, and DNA damage. Restoring p53 function concurrently reduces chromosomal instability within the HGSOC cells, underscoring its crucial contribution in safeguarding genomic integrity by moderating the baseline occurrence of double-strand breaks arising from replication stress. Furthermore, in various mouse models, treatment with p53 mRNA reduced tumor growth and inhibited tumor cell dissemination in the peritoneal cavity in a dose-dependent manner. The IVT mRNA-based reactivation of p53 holds promise as a potential therapeutic strategy for HGSOC, providing valuable insights into the molecular mechanisms underlying p53 function and its relevance in ovarian cancer treatment.

Pharmacological reactivation of p53 in the era of precision anticancer medicine.

p53, which is encoded by the most frequently mutated gene in cancer, TP53, is an attractive target for novel cancer therapies. Despite major challenges associated with this approach, several compounds that either augment the activity of wild-type p53 or restore all, or some, of the wild-type functions to p53 mutants are currently being explored. In wild-type TP53 cancer cells, p53 function is often abrogated by overexpression of the negative regulator MDM2, and agents that disrupt p53-MDM2 binding can trigger a robust p53 response, albeit potentially with induction of p53 activity in non-malignant cells. In TP53-mutant cancer cells, compounds that promote the refolding of missense mutant p53 or the translational readthrough of nonsense mutant TP53 might elicit potent cell death. Some of these compounds have been, or are being, tested in clinical trials involving patients with various types of cancer. Nonetheless, no p53-targeting drug has so far been approved for clinical use. Advances in our understanding of p53 biology provide some clues as to the underlying reasons for the variable clinical activity of p53-restoring therapies seen thus far. In this Review, we discuss the intricate interactions between p53 and its cellular and microenvironmental contexts and factors that can influence p53's activity. We also propose several strategies for improving the clinical efficacy of these agents through the complex perspective of p53 functionality.

Abstract LB_A25: Updated Phase 1 results from the PYNNACLE Phase 1/2 study of PC14586, a selective p53 reactivator, in patients with advanced solid tumors harboring a TP53 Y220C mutation

Abstract Background: Mutations in the TP53 gene leading to p53 inactivation are the most common mutational event across human cancers. PC14586 is a first-in-class p53 reactivator that selectively binds to the mutated p53 Y220C protein and restores p53 wild-type activity. Preclinical data support potential for activity of PC14586 across TP53 Y220C-bearing tumors, with enhanced activity in KRAS wild-type (WT) models, consistent with the important parallel roles for p53 inactivation and oncogenic KRAS in tumorigenesis. Preliminary analysis of Phase 1 data from the Phase 1/2 PYNNACLE trial (NCT04585750) evaluating PC14586 in patients with advanced TP53 Y220C solid tumors showed that PC14586 was well tolerated with preliminary clinical activity across multiple tumor types in the efficacious dose range (1150 mg QD to 1500 mg BID). This updated Phase 1 analysis assesses PC14586 in patients treated across the efficacious dose range. Methods: Eligible patients (≥12 years) with locally advanced or metastatic solid tumors with a TP53 Y220C mutation received increasing oral doses of PC14586 to evaluate safety, PK, and preliminary efficacy via RECIST v1.1, and to determine the Recommended Phase 2 Dose (RP2D). Tumor molecular profiling was assessed for the impact of KRAS status on response. Results: As of 1 May 2023, 61 patients were treated in the efficacious dose range (safety population): median age 63 (range 32-84) years, 62% female, and median of 3 (range 1–9) prior lines of systemic therapy. The most frequent treatment-related adverse events (TRAEs) (≥10%) were nausea (42.3%), vomiting (35.2%), diarrhea (19.7%), increased creatinine (18.3%), fatigue (14.1%), and increased AST and ALT (12.7% each); 3% of patients discontinued PC14586 due to TRAEs. Most TRAEs were grade 1 or 2; the most common grade 3 TRAEs were anemia (4.2%) and increased ALT (2.8%). PC14586 administered with food led to improvement in nausea and vomiting. Dose proportional and linear PK was observed with a median half-life of 19 hours. Among patients with measurable disease, 36 patients had KRAS WT and 15 patients had KRAS mutated tumors. A total of 12 PRs (ORR 33.3%) were observed (9 confirmed and 3 unconfirmed - pending confirmation) in patients with KRAS WT disease across multiple tumor types including ovarian, breast, prostate, small-cell lung, and endometrial cancer. The median duration of confirmed response was 7 months. In patients with a KRAS mutation, there were no confirmed responses, although clinical activity was observed. At 2000 mg QD, the ORR was 46.2% in patients with TP53 Y220C and KRAS WT tumors (n=13). A RP2D of 2000 mg QD was selected based on overall safety, PK and preliminary efficacy. Conclusions: PC14586 was well-tolerated with a favorable safety profile. Efficacy was achieved in heavily pre-treated patients across multiple tumor types. The PYNNACLE registrational Phase 2 trial will assess PC14586 as monotherapy at the RP2D of 2000 mg QD in patients with TP53 Y220C and KRAS WT advanced solid tumors. Additional/updated data will be presented at the conference. Citation Format: Alison M Schram, Geoffrey I Shapiro, Melissa L Johnson, Anthony W. Tolcher, John A Thompson, Anthony B El-Khoueiry, Andrae L Vandross, Shivaani Kummar, Aparna R Parikh, Dale R Shepard, Ursula Garczarek, Kim LeDuke, Lisa Sheehan, Marc Fellous, Leila Alland, Ecaterina E Dumbrava. Updated Phase 1 results from the PYNNACLE Phase 1/2 study of PC14586, a selective p53 reactivator, in patients with advanced solid tumors harboring a TP53 Y220C mutation [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr LB_A25.

Abstract A103: Targeting mutant p53-R248W reactivates WT p53 function and alters the onco-metabolic profile

Abstract The tumor suppressor p53 is mutated (mt-p53) in over 50% of human cancers causing gain-of-function oncogenic effects, including metabolic changes that reduce tumor responsiveness to radio/chemotherapy. Common hot-spot mutations within the DNA-binding domain can be categorized as conformational (R175H) or DNA binding (R248W). NSC59984 has been characterized as a small molecule that targets mt-p53 for degradation and restores wt-p53 signaling. Using esophageal adenocarcinoma cells and CRISPR generated isogenic cell lines bearing matching hot-spot p53 mutations, we aim to understand how the molecular features of mt-p53 affect drug efficiency and enable the development of targeted therapies to limit cancer cell growth. We found that NSC59984 covalently modifies p53 by Michael addition at cysteine residues 124 and 229, which promote interactions that would stabilize the protein/DNA complex leading to increased p53 transcriptional activity. In cells, the effects of NSC59984 were substantially greater in cells harboring the R248W mutation compared with the R175H mutation. Treatment with NSC59984 reduced proliferation and increased apoptosis via the intrinsic mitochondrial pathway. It also induced changes in OXPHOS, ATP level, mitochondrial membrane potential, glycolysis, and lactate production. Furthermore, treatment of cells with NSC59984 increased reactive oxygen species production and decreased glutathione levels; effects were enhanced by the addition of buthionine sulfoximine and inhibited by N-acetyl cysteine. NSC59984 treatment increased G6PD activity, total NADPH levels, and expression of TIGAR. Knockout of TIGAR partially removed the antiproliferative effects of the drug and reduced G6PD levels in the p53-R248W cells. Incorporation of [13C6] into cellular metabolites suggests that p53-regulated transcription of TIGAR increased utilization of the pentose phosphate pathway and inhibited glycolysis at the fructose-6-P fructose-1,6-bisphosphate junction, supported by an increase in Hexokinase 2 and a decrease of phosphofructokinase-1. Thermal proteome profiling identified TIGAR as an additional reaction target of NSC59984, suggesting increased involvement in modulating these metabolic effects. Combining currently available therapeutic metabolic inhibitors with NSC59984 enhanced the antiproliferative effects in cells harboring p53-R248W creating a therapeutic window when compared to the wt-p53 expressing cells. This suggests these combinations could be used in a clinically relevant setting. Overall, this work has identified a distinctive mode of action for p53 reactivation resulting in not only transcriptional activity, but also a unique effect on cellular energetics. This study shows evidence of variation in responsiveness of different mt-p53 forms and allows the development of specific therapeutics directed to individuals for patient-centered precision medicine. Importantly, we have shown that targeting p53 signaling has significant effects on the metabolic profiles of cancer cells rendering them more vulnerable to neoadjuvant therapy. Citation Format: Kate Brown, Lisa Jenkins, Dan Crooks, Deborah Surman, Sharlyn Mazur, Yuan Xu, Bhargav Arimilli, Ye Yang, Andrew Lane, Stewart Durell, Teresa Fan, David Schrump, Marston Marston, Taylor Ripley, Ettore Appella, Gaelyn Lyons, Andrew Perciaccante, Jerry Dinan, Marco Robello, Herman Nikolayevskiy, Robert O’Connor, Daniel Appella. Targeting mutant p53-R248W reactivates WT p53 function and alters the onco-metabolic profile [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr A103.

Enhanced TP53 reactivation disrupts MYC transcriptional program and overcomes venetoclax resistance in acute myeloid leukemias.

The tumor suppressor TP53 is frequently inactivated in a mutation-independent manner in cancers and is reactivated by inhibiting its negative regulators. We here cotarget MDM2 and the nuclear exporter XPO1 to maximize transcriptional activity of p53. MDM2/XPO1 inhibition accumulated nuclear p53 and elicited a 25- to 60-fold increase of its transcriptional targets. TP53 regulates MYC, and MDM2/XPO1 inhibition disrupted the c-MYC-regulated transcriptome, resulting in the synergistic induction of apoptosis in acute myeloid leukemia (AML). Unexpectedly, venetoclax-resistant AMLs express high levels of c-MYC and are vulnerable to MDM2/XPO1 inhibition in vivo. However, AML cells persisting after MDM2/XPO1 inhibition exhibit a quiescence- and stress response-associated phenotype. Venetoclax overcomes that resistance, as shown by single-cell mass cytometry. The triple inhibition of MDM2, XPO1, and BCL2 was highly effective against venetoclax-resistant AML in vivo. Our results propose a novel, highly translatable therapeutic approach leveraging p53 reactivation to overcome nongenetic, stress-adapted venetoclax resistance.

RARE PRIMARY CLEAR CELL CARCINOMA OF BLADDER OF MULLERIAN ORIGIN: MORPHO- IMMUNOHISTOCHEMICAL PROFILING

Abstract Introduction/Objective Primary clear cell carcinoma of urinary bladder (PCCCUB) is a rare and aggressive cancer variant with uncertain and debatable histogenesis. The hypotheses include origins from the urothelium, pre-existing Müllerian precursors, or mesonephric remnants. Definitive diagnosis is achieved through histology and immunohistochemistry (IHC). We present an unusual case of PCCCUB in a sexagenarian woman. Methods/Case Report Patient with history of diabetes, hypertension, and smoking presented with gross hematuria. Computed tomography urogram revealed a 2.3 x 1.2 cm enhancing mass at the base of the urinary bladder. Patient underwent transurethral resection of the bladder tumor (TURBT). Histopathology revealed features of tubulo-papillary, solid, glandular structures with hyalinized stroma. Cytologic features varied from flat, hobnail, to polygonal with abundant clear to eosinophilic cytoplasm and prominent nucleoli. Immunohistochemistry revealed strong reactivity for PAX8, CK7, ER, and racemase; focal reactivity for vimentin, napsin A, p53, CA125; and non-reactivity for PAX2, WT1, PR, GATA3, pCEA, CK20, p63, p40, CD10, RCC, BRST-2, and mammaglobin. P53 showed a wild type staining pattern and Ki-67 was 10%. Combined morphologic and IHC features confirmed PCCCUB, and in the absence of muscularis mucosal invasion, tumor was staged pT1N0. PAX8 positivity and urothelial marker negativity excluded clear cell pattern of urothelial carcinoma. IHC also excluded nephrogenic adenoma, and metastasis. The female gender, and CK 7 (+)/CK 20 (−) profile supported Müllerian origin. Restaging TURBT showed consistent results. Subsequently, anterior pelvic exenteration and bilateral pelvic lymph nodes dissection was performed revealing muscularis propria invasion upstaging to mpT2 N0. Results (if a Case Study enter NA) NA Conclusion Poor prognosis, aggressive behavior, and advanced stage at the time of diagnosis warrants accurate diagnose of PCCCUB. Ambiguous origin, limited literature, and lack of clear management guidelines merit reporting in order to enhance knowledge of this rare and intriguing entity.

RTID-05. SURGICAL WINDOW OF OPPORTUNITY TRIAL REVEALS MECHANISMS OF RESPONSE AND RESISTANCE TO NAVTEMADLIN (KRT-232) IN PATIENTS WITH RECURRENT GLIOBLASTOMA

Abstract Over half of glioblastoma multiforme (GBM) patients retain wild-type p53, resulting in potential susceptibility to MDM2 inhibitors. These molecules disrupt the interaction between p53 and its negative regulator MDM2, resulting in downstream pathway signaling and cell fate decisions such as growth inhibition and death from cellular stress. We have analyzed clinical samples from 21 patients with recurrent GBM treated with the MDM2 inhibitor KRT-232, all of which relapsed despite the biological promise of this small molecule. By analyzing on-treatment biopsy samples, we detected upregulation of p53 transcriptional targets, suggesting blood-brain barrier penetrance and drug pharmacodynamics. However, in patient-derived cell lines, treatment with KRT-232 at the clinically achieved concentration was only sufficient to stall but not reduce tumor growth. Cell death via apoptosis was achieved in these cell line models when MDM2 inhibition was combined with the chemotherapeutic agent temozolomide. These drugs have non-overlapping mechanisms of action and exhibit synergy in our cell line models. Normal human bone marrow cells underwent a reversible growth inhibition phenotype when treated with KRT-232 and TMZ, supporting the idea that a therapeutic window exists with this combination. We additionally observed that tumor progression occurred in the absence of p53 inactivating mutations, suggesting that other mechanisms of resistance to KRT-232 may modulate drug response and resistance in GBM. Indeed, drug treatment induced an adaptive response in human tumors, characterized by the upregulation of genes involved in glial cell differentiation processes. Ongoing work is focused on understanding how tumor heterogeneity and cell state modulate response and resistance of GBMs to MDM2 inhibition and other therapeutic strategies that reactivate p53 signaling. Our study highlights the utility of tissue sampling during clinical trials and represents the first clinical effort to detect adaptive changes in human tumor tissue associated with p53 reactivation.

EXTH-06. GLIOBLASTOMA PATIENT SPECIFIC TRANSCRIPTOME REMODELING IN RESPONSE TO MDM2 ANTAGONIST TREATMENT OF WILD-TYPE P53 CANCER STEM CELLS IS ASSOCIATED WITH SENSITIVITY AND STRATEGIES FOR COMBINATION THERAPY

Abstract Over 70% of glioblastomas are p53 wild-type and these patients could benefit from p53 reactivation treatment. Here we determined the sensitivity of a glioblastoma patient-derived cancer stem cells (CSCs) panel to three MDM2 antagonists (MDM2a) to test to what extent transcriptional reprogramming is affected by genomic background and correlates to response to acute treatment with MDM2 antagonists. IC50 concentrations and area above the curve (AAC) were measured from dose response curves obtained from 4 and 7-day treatment. The inhibitors were specific to wt-p53 CSCs, but these presented a wide range of sensitivity. Seven wt-p53 CSCs were treated RG7112 IC50 concentrations or DMSO control for 24h (n=4). RNA was isolated for Illumina Truseq stranded mRNA libraries sequenced at 30M depth. Quantified raw counts were processed using NOISeq R package to determine differentially expressed genes (DEG) between control and treated samples. In addition to the expected high representation of upregulated p53 targets in all cell lines, we observed significan cell specific transcriptome alterations, including enrichment of survival pathways, such as mTOR, ERK and NFkB in the less sensitive CSC lines, which did not readily correlate with the individual genomic landscapes. E2F targets, G2-M cell cycle check point and DNA-repair pathways were highly enriched in the downregulated genes. Combination of MDM2a with radiation treatment (RT) was synergistic to a subset of CSCs. As validation we found that MDM2a treatment was effective in sensitizing a resistant orthotopic mouse glioblastoma PDX to fractionated RT, with maximum efficacy when treatment started 24h prior to RT vs simultaneously (Log-rank Mantel-Cox test: p=0.0006 vs 0.0277). The integration of the treatment-mediated transcriptional patterns with differential sensibility to MDM2 antagonists and genomic landscape of the CSC panel provides a platform to identify targets for combination therapies, which is the most promising clinical application of the reactivation of wt-p53 in GBMs.

Deep learning untangles the resistance mechanism of p53 reactivator in lung cancer cells

Tumor suppressor p53 plays a pivotal role in suppressing cancer, so various drugs has been suggested to upregulate its function. However, drug resistance is still the biggest hurdle to be overcome. To address this, we developed a deep learning model called AnoDAN (anomalous gene detection using generative adversarial networks and graph neural networks for overcoming drug resistance) that unravels the hidden resistance mechanisms and identifies a combinatorial target to overcome the resistance. Our findings reveal that the TGF-β signaling pathway, alongside the p53 signaling pathway, mediates the resistance, with THBS1 serving as a core regulatory target in both pathways. Experimental validation in lung cancer cells confirms the effects of THBS1 on responsiveness to a p53 reactivator. We further discovered the positive feedback loop between THBS1 and the TGF-β pathway as the main source of resistance. This study enhances our understanding of p53 regulation and offers insights into overcoming drug resistance.

Biological Effects of HDAC Inhibitors Vary with Zinc Binding Group: Differential Effects on Zinc Bioavailability, ROS Production, and R175H p53 Mutant Protein Reactivation.

The coordination of zinc by histone deacetylase inhibitors (HDACi), altering the bioavailability of zinc to histone deacetylases (HDACs), is key to HDAC enzyme inhibition. However, the ability of zinc binding groups (ZBGs) to alter intracellular free Zn+2 levels, which may have far-reaching effects, has not been explored. Using two HDACis with different ZBGs, we documented shifts in intracellular free Zn+2 concentrations that correlate with subsequent ROS production. Next, we assayed refolding and reactivation of the R175H mutant p53 protein in vitro to provide greater biological context as the activity of this mutant depends on cellular zinc concentration. The data presented demonstrates the differential activity of HDACi in promoting R175H response element (RE) binding. After cells are treated with HDACi, there are differences in R175H mutant p53 refolding and reactivation, which may be related to treatments. Collectively, we show that HDACis with distinct ZBGs differentially impact the intracellular free Zn+2 concentration, ROS levels, and activity of R175H; therefore, HDACis may have significant activity independent of their ability to alter acetylation levels. Our results suggest a framework for reevaluating the role of zinc in the variable or off-target effects of HDACi, suggesting that the ZBGs of HDAC inhibitors may provide bioavailable zinc without the toxicity associated with zinc metallochaperones such as ZMC1.

Radiation Toxicity Profile Difference in p16+ vs. p16- Oropharyngeal Cancer Patients

p16+ oropharyngeal squamous cell carcinoma is radiosensitive and has better prognosis than p16-ve. However, the correlation between p16 reactivity and radiation toxicity profile in these patients has not been studied. Edmonton Symptom Assessment System (ESAS) is a generic patient reported symptom scale validated for patient reported outcome (PRO) assessments in head and neck cancer patients. We sought to review the ESAS and its psychometric properties in oropharyngeal cancer patients treated with concurrent chemoradiation (CCRT) stratified by their HPV status. To evaluate differences in magnitude and temporal trends in PRO before, during and after radiation treatments in both p16+ and p16-ve oropharyngeal cancer patients using ESAS scores. Prospectively collected ESAS scores for oropharyngeal cancer patients treated at a safety net hospital with CCRT were analyzed. Longitudinal variation in pain, depression, appetite and family distress scores before, during and up to 36 weeks after CCRT were evaluated at seven time points: prior to treatment, 1-3, 4-6, 7-10, 11-15, 16-20 and 20-36 weeks. Statistical analysis focused on data collected through repeated measurements for patients using ANOVA mixed regression analysis using p16 status as between subjects factor for each symptom. Three hundred fifty-five ESAS assessments were analyzed for each symptom for 64 oropharyngeal cancer patients treated with CCRT. Subsites identified were 21 (32.8%) tonsil, 15 (23.4%) base of tongue, 22 (34.4%) soft palate, and 6 (9.4%) oropharynx not specified. We identified 35 (54.7%) p16+ and 29 (45.3%) p16-ve patients. The median age of the cohort was 60 (range: min 39 - max 88); the median age was 59 for p16+ and 61 for p16-ve. Median total radiation dose was 6996 Gy. Pain scores peaked at 7-10 weeks for both groups but p16-ve had delayed peak 11-15 weeks as well. Depression scores stayed <4 for both populations but family distress, pain and appetite scores peaked for p16-ve between 11-15 weeks. Mean pain scores were similar for both populations and peak during CCRT for both however p16-ve patients have another peak after completion of CCRT. Family distress and decreased appetite also heighten during this post CCRT time for p16-ve patients which warrants a planned early intervention at 11-15 weeks for these patients to improve their quality of life.

Abstract PO-023: The AP-1 transcription factor component, JunB, regulates the expression of HPV genes in head and neck cancer

Abstract Within head and neck squamous cell carcinoma (HNSCC), those induced by the human papillomavirus (HPV+) have a more hypermethylated genome compared to those that are negative (HPV-). Therefore, our lab explored the usage of the demethylating agent 5-azacytidine (5-aza), an FDA-approved drug for the treatment of myelodysplasia and acute myeloid leukemia. Repurposing FDA-approved drugs is a strategic way to quickly provide patients with secondary therapeutic options, especially since the incidence of HPV+ HNSCC is now considered an epidemic in the US and Western Europe. Additionally, initial therapy for patients is aggressive leading to adverse, lifelong side effects. Despite having a higher cure rate than HPV-HNSCC, the recurrence rate is still approximately 30% for HPV+ HNSCC. Our lab has found that HPV+ HNSCC cells are more sensitive than HPV- cells to 5-aza as low doses of 5-aza delayed HPV+ xenograft tumor growth and 5-aza-treated HPV+ tumor samples from patients treated in a window trial had increased cell death. Despite demethylation inducing an active, open chromatin conformation, we also observed a marked downregulation of HPV genes expression after 5-aza. Decreased HPV E6 expression, followed by reactivation of tumor suppressor p53, induced p53-dependent apoptosis in HPV+ HNSCC. This decreased expression of HPV genes is an essential component of 5-aza-associated toxicity toward HPV+ HNSCC. Our lab has recently explored the molecular mechanisms of 5-aza on HPV+ HNSCC. We found that 5-aza transcriptionally downregulated the expression of HPV genes, including oncogenes E6 and E7. Microarray studies show marked downregulation of the proto-oncogene JunB, a component of the transcription factor AP-1 (Activator Protein 1) after 5-aza treatment. Experimental deletion of JunB inhibited oncogenes E6 and E7 and restored p53 but also indicated that untreated HPV+ HNSCCs depend on JunB for clonogenic growth. Through this study, we have identified a novel dependency on JunB in HPV+ HNSCC and revealed a new rational target that is desperately needed to treat recurrent/metastatic patients and decrease the toxicity associated with current treatment. Citation Format: Hina Rehmani, Natalia Isaeva, Travis P. Schrank, Wendell G. Yarbrough. The AP-1 transcription factor component, JunB, regulates the expression of HPV genes in head and neck cancer [abstract]. In: Proceedings of the AACR-AHNS Head and Neck Cancer Conference: Innovating through Basic, Clinical, and Translational Research; 2023 Jul 7-8; Montreal, QC, Canada. Philadelphia (PA): AACR; Clin Cancer Res 2023;29(18_Suppl):Abstract nr PO-023.

Targeted Polymersome Delivery of a Stapled Peptide for Drugging the Tumor Protein p53:BCL-2-Family Axis in Diffuse Large B-Cell Lymphoma.

Diffuse large B-cell lymphoma (DLBCL) remains a formidable diagnosis in need of new treatment paradigms. In this work, we elucidated an opportunity for therapeutic synergy in DLBCL by reactivating tumor protein p53 with a stapled peptide, ATSP-7041, thereby priming cells for apoptosis and enhancing their sensitivity to BCL-2 family modulation with a BH3-mimetic, ABT-263 (navitoclax). While this combination was highly effective at activating apoptosis in DLBCL in vitro, it was highly toxic in vivo, resulting in a prohibitively narrow therapeutic window. We, therefore, developed a targeted nanomedicine delivery platform to maintain the therapeutic potency of this combination while minimizing its toxicity via packaging and targeted delivery of a stapled peptide. We developed a CD19-targeted polymersome using block copolymers of poly(ethylene glycol) disulfide linked to poly(propylene sulfide) (PEG-SS-PPS) for ATSP-7041 delivery into DLBCL cells. Intracellular delivery was optimized in vitro and validated in vivo by using an aggressive human DLBCL xenograft model. Targeted delivery of ATSP-7041 unlocked the ability to systemically cotreat with ABT-263, resulting in delayed tumor growth, prolonged survival, and no overt toxicity. This work demonstrates a proof-of-concept for antigen-specific targeting of polymersome nanomedicines, targeted delivery of a stapled peptide in vivo, and synergistic dual intrinsic apoptotic therapy against DLBCL via direct p53 reactivation and BCL-2 family modulation.

GingerenoneA overcomes dexamethasone resistance by activating apoptosis and inhibiting cell proliferation in pediatric T-ALL cells.

Plant-based combination strategies have been widely considered in cancer therapy to attenuate chemotherapeutics side effects. The anti-leukemic effect of the whole ginger extract was previously portrayed by our team, and the current study is centered around the cytotoxicity and mechanism of action of a phenolic subsidiary of ginger, GingerenoneA, on pediatric acute lymphoblastic leukemia. GingernoneA imposed, dose-dependently, inhibitory effects on the viability of T and B leukemia cell lines confirmed by MTT assays. Resistance to Dexamethasone, a mostly used chemotherapeutic in acute lymphoblastic leukemia treatments, was overcome by GingernoneA. A synergistic effect of Dexamethasone and GingrenoneA on T leukemia cell lines and patient primary cells was confirmed. Annexin-V/PI and acridine orange/ethidium bromide staining illustrated dose-dependent apoptosis in CCRF-CEM cells developed by GingerenoneA. The intrinsic and extrinsic apoptosis induction and antiproliferative attribution of GingerenoneA were validated by western blot and qPCR. Despite the supposed loss of function in CCRF-CEM cells, TP53 showed increased expression levels and functional activity upon treatment with GingernoneA. Bioinformatic studies revealed the conceivable impact of GingerenoneA on the reactivity of mutant P53 through its binding to Cys124. Our findings may provide novel strategies for therapeutic intervention to ameliorate pALL outcomes.

PRIMA-1MET Does Not Restore Vitamin D Sensitivity to MDA-MB-231 and MDA-MB-468 Triple-Negative Breast Cancer Cells.

Vitamin D is a steroid hormone that causes growth suppression in cultured cells. We had previously discovered that the triple-negative breast cancer cell lines MDA-MB-231 and MDA-MB-468 did not have growth suppression with vitamin D, while MCF-7 did. MCF-7 cells are not triple-negative and have wild-type p53. Both MDA-MB-231 and MDA-MB-468 have mutations in p53 and these mutations were a possible explanation for the lack of growth suppression with vitamin D. Our hypothesis was that reactivation of p53 in the triple-negative cell lines would cause them to become sensitive to vitamin D. We chose to use the small molecule PRIMA-1MET to reactivate p53 as it has been previously shown to restore function to the p53 mutants present in MB-231 and MB-468. We then measured the ability of vitamin D and its analogues calcipotriol and EB1089 to suppress growth in the presence of PRIMA-1MET. Here, we show that while PRIMA-1MET can kill the breast cancer cells investigated in this study, it does not restore their sensitivity to vitamin D or its analogues.

WR1065 conjugated to thiol-PEG polymers as novel anticancer prodrugs: broad spectrum efficacy, synergism, and drug resistance reversal.

The lack of anticancer agents that overcome innate/acquired drug resistance is the single biggest barrier to achieving a durable complete response to cancer therapy. To address this issue, a new drug family was developed for intracellular delivery of the bioactive aminothiol WR1065 by conjugating it to discrete thiol-PEG polymers: 4-star-PEG-S-S-WR1065 (4SP65) delivers four WR1065s/molecule and m-PEG6-S-S-WR1065 (1LP65) delivers one. Infrequently, WR1065 has exhibited anticancer effects when delivered via the FDA-approved cytoprotectant amifostine, which provides one WR1065/molecule extracellularly. The relative anticancer effectiveness of 4SP65, 1LP65, and amifostine was evaluated in a panel of 15 human cancer cell lines derived from seven tissues. Additional experiments assessed the capacity of 4SP65 co-treatments to potentiate the anticancer effectiveness and overcome drug resistance to cisplatin, a chemotherapeutic, or gefitinib, a tyrosine kinase inhibitor (TKI) targeting oncogenic EGFR mutations. The CyQUANT®-NF proliferation assay was used to assess cell viability after 48-h drug treatments, with the National Cancer Institute COMPARE methodology employed to characterize dose-response metrics. In normal human epithelial cells, 4SP65 or 1LP65 enhanced or inhibited cell growth but was not cytotoxic. In cancer cell lines, 4SP65 and 1LP65 induced dose-dependent cytostasis and cytolysis achieving 99% cell death at drug concentrations of 11.2 ± 1.2 µM and 126 ± 15.8 µM, respectively. Amifostine had limited cytostatic effects in 11/14 cancer cell lines and no cytolytic effects. Binary pairs of 4SP65 plus cisplatin or gefitinib increased the efficacy of each partner drug and surmounted resistance to cytolysis by cisplatin and gefitinib in relevant cancer cell lines. 4SP65 and 1LP65 were significantly more effective against TP53-mutant than TP53-wild-type cell lines, consistent with WR1065-mediated reactivation of mutant p53. Thus, 4SP65 and 1LP65 represent a unique prodrug family for innovative applications as broad-spectrum anticancer agents that target p53 and synergize with a chemotherapeutic and an EGFR-TKI to prevent or overcome drug resistance.

P53 restoration in small cell lung cancer identifies a latent cyclophilin-dependent necrosis mechanism

The p53 tumor suppressor regulates multiple context-dependent tumor suppressive programs. Although p53 is mutated in ~90% of small cell lung cancer (SCLC) tumors, how p53 mediates tumor suppression in this context is unknown. Here, using a mouse model of SCLC in which endogenous p53 expression can be conditionally and temporally regulated, we show that SCLC tumors maintain a requirement for p53 inactivation. However, we identify tumor subtype heterogeneity between SCLC tumors such that p53 reactivation induces senescence in a subset of tumors, while in others, p53 induces necrosis. We pinpoint cyclophilins as critical determinants of a p53-induced transcriptional program that is specific to SCLC tumors and cell lines poised to undergo p53-mediated necrosis. Importantly, inhibition of cyclophilin isomerase activity, or genetic ablation of specific cyclophilin genes, suppresses p53-mediated necrosis by limiting p53 transcriptional output without impacting p53 chromatin binding. Our study demonstrates that intertumoral heterogeneity in SCLC influences the biological response to p53 restoration, describes a cyclophilin-dependent mechanism of p53-regulated cell death, and uncovers putative mechanisms for the treatment of this most-recalcitrant tumor type.

SF3B1 Mutations Are Associated with Resistance to Non-Genotoxic MDM2 Inhibition in Chronic Lymphocytic Leukemia.

Chronic lymphocytic leukemia (CLL) is a genetically and clinically heterogeneous malignancy affecting older individuals. There are a number of current treatment options for CLL, including monoclonal antibodies, targeted drugs, chemotherapy, and different combinations of these. However, for those patients who are intrinsically treatment resistant, or relapse following initial responses, novel targeted therapies are still needed. Targeting the mouse double-minute-2 human homolog (MDM2), a primary negative regulator of p53, is an appealing therapeutic strategy for non-genotoxic reactivation of p53, since the TP53 gene is in its wild-type state at diagnosis in approximately 90% of patients. Mutated SF3B1 and TP53 are both associated with more aggressive disease, resistance to therapies and poorer overall survival for CLL. In this study, we performed a screen for SF3B1 and TP53 mutations and tested RG7388 (idasanutlin), a second-generation MDM2 inhibitor, in a cohort of CLL primary patient samples. SF3B1 mutations were detected in 24 of 195 cases (12.3%) and found associated with poor overall survival (hazard ratio [HR] 2.12, p = 0.032) and high CD38 expression (median CD38 (%) 32 vs. 5; p = 0.0087). The novel striking finding of this study was an independent link between SF3B1 mutational status and poor response to RG7388. Overall, SF3B1 mutations in CLL patient samples were associated with resistance to treatment with RG7388 ex vivo, and patients with the wild type for both SF3B1 and TP53 are more likely to benefit from treatment with MDM2 inhibitors.

Mutant p53 in head and neck squamous cell carcinoma: Molecular mechanism of gain‑of‑function and targeting therapy (Review).

Head and neck squamous cell carcinoma (HNSCC) is one of the most widespread malignancies worldwide. p53, as a transcription factor, can play its role in tumor suppression by activating the expression of numerous target genes. However, p53 is one of the most commonly mutated genes, which frequently harbors missense mutations. These missense mutations are nucleotide substitutions that result in the substitution of an amino acid in the DNA binding domain. Most p53 mutations in HNSCC are missense mutations and the mutation rate of p53 reaches 65‑85%. p53 mutation not only inhibits the tumor suppressive function of p53 but also provides novel functions to facilitate tumor recurrence, called gain‑of‑function (GOF). The present study focused on the prevalence and clinical relevance of p53 mutations in HNSCC, and further described how mutant p53 accumulates. Moreover, mutant p53 in HNSCC can interact with proteins, RNA, and exosomes to exert effects on proliferation, migration, invasion, immunosuppression, and metabolism. Finally, several treatment strategies have been proposed to abolish the tumor‑promoting function of mutant p53; these strategies include reactivation of mutant p53 into wild‑type p53, induction of mutant p53 degradation, enhancement of the synthetic lethality of mutant p53, and treatment with immunotherapy. Due to the high frequency of p53 mutations in HNSCC, a further understanding of the mechanism of mutant p53 may provide potential applications for targeted therapy in patients with HNSCC.

The p53 reactivator PRIMA-1MET synergises with 5-fluorouracil to induce apoptosis in pancreatic cancer cells.

Pancreatic cancer (PC) is one of the deadliest malignancies; p53 is mutated in approximately 75% of PC patients. Hence, the protein derived from mutant/wild-type TP53 may represent a therapeutic target. Interestingly, a p53 reactivator (PRIMA-1MET) showed promise in clinical trials of haematological malignancies; therefore, it warrants an in vitro evaluation in PC cell lines. To evaluate the antiproliferative effects of PRIMA-1MET, either alone or combined with the common chemotherapy 5-fluorouracil (5-FU), against mutated and wild-type p53 PC cell lines. This study involved p53-mutant (AsPC-1) and p53-wild type (Capan-2) PC cell lines. The cytotoxicity of PRIMA-1MET alone or in combination with 5-FU was evaluated by MTT assay. Synergism was assessed by calculating the combination index (CI) via CalcuSyn software. Fluorescence microscopy was used to analyse apoptosis following acridine orange/ethidium bromide (AO/EB) staining. Morphological changes were investigated with an inverted microscope. Quantitative reverse transcription PCR (RT‒qPCR) was used to measure gene expression. Both PC cell lines were sensitive to PRIMA-1MET monotherapy. Furthermore, PRIMA-1MET and 5-FU had a synergistic effect (CI < 1), reflected by significant enhancement of apoptosis and morphological changes in the combination vs. monotherapy treatments. Moreover, the RT‒qPCR results indicated increased expression of the NOXA and TP73 genes in combination-treated cells. Our data suggested that PRIMA-1MET, whether alone or combined with 5-FU, has an antiproliferative effect on PC cell lines regardless of p53 mutational status. The synergism of the combination was associated with significant apoptosis induction through p53-dependent and p53-independent pathways. Preclinical confirmation of these data in in vivo models is highly recommended.