Mutant p53 as an Antigen in Cancer Immunotherapy

DNA-delivered monoclonal antibodies targeting the p53 R175H mutant epitope inhibit tumor development in mice

The tumor suppressor p53 is the most common mutated gene in cancer, with the R175H as the most frequent p53 missense mutant. However, there are currently no approved targeted therapies or immunotherapies against mutant p53. Here, we characterized and investigated a monoclonal antibody (mAb) that recognizes the mutant p53-R175H for its affinity, specificity, and activity against tumor cells in vitro. We then delivered DNA plasmids expressing the anti-R175H mAb or a bispecific antibody (BsAb) into mice to evaluate their therapeutic effects. Our results showed that the anti-R175H mAb specifically bound to the p53-R175H antigen with a high affinity and recognized the human mutant p53-R175H antigen expressed on HEK293T or MC38 cells, with no cross-reactivity with wild-type p53. In cultured cells, the anti-R175H mAb showed higher cytotoxicity than the control but did not induce antibody-dependent cellular cytotoxicity. We made a recombinant MC38 mouse cell line (MC38-p53-R175H) that overexpressed the human p53-R175H after knocking out the endogenous mutant p53 alleles. In vivo, administration of the anti-R175H mAb plasmid elicited a robust anti-tumor effect against MC38-p53-R175H in mice. The administration of the anti-R175H BsAb plasmid showed no therapeutic effects, yet potent anti-tumor activity was observed in combination with the anti-PD-1 antibody. These results indicate that targeting specific mutant epitopes using DNA-delivered mAbs or BsAbs presents a form of improved natural immunity derived from tumor-infiltrating B cells and plasma cells against intracellular tumor antigens.

A case of sequential medical therapy for advanced ureteral cancer in Li-Fraumeni syndrome

Introduction

Li-Fraumeni syndrome, an autosomal dominant cancer predisposition syndrome caused by a pathogenic variant of TP53, a tumor suppressor gene, leads to a high risk from early childhood of developing various types of cancers. Here, we report a case of advanced ureteral cancer in Li-Fraumeni syndrome.

Case presentation

A 73 years-old female patient, who had been diagnosed genetically as Li-Fraumeni syndrome; suffered from chondrosarcoma in the left pelvic joint, bilateral breast cancer, endometrial cancer, gastric cancer, and colon cancer in her history. She was diagnosed as unresectable advanced urothelial cancer during continuous magnetic resonance imaging surveillance, underwent avelumab maintenance therapy after the combination of gemcitabine and cisplatin chemotherapy. The efficacies of gemcitabine and cisplatin chemotherapy and avelumab maintenance therapy were good.

Conclusion

We report an advanced urothelial cancer in a patient with Li-Fraumeni syndrome who demonstrated good efficacies to sequential medical therapy.

p53 Modulates Radiosensitivity in Head and Neck Cancers-From Classic to Future Horizons

p53, initially considered a tumor suppressor, has been the subject of research related to cancer treatment resistance in the last 30 years. The unfavorable response to multimodal therapy and the higher recurrence rate, despite an aggressive approach, make HNSCC a research topic of interest for improving therapeutic outcomes, even if it is only the sixth most common malignancy worldwide. New advances in molecular biology and genetics include the involvement of miRNA in the control of the p53 pathway, the understanding of mechanisms such as gain/loss of function, and the development of different methods to restore p53 function, especially for HPV-negative cases. The different ratio between mutant p53 status in the primary tumor and distant metastasis originating HNSCC may serve to select the best therapeutic target for activating an abscopal effect by radiotherapy as a "booster" of the immune system. P53 may also be a key player in choosing radiotherapy fractionation regimens. Targeting any pathway involving p53, including tumor metabolism, in particular the Warburg effect, could modulate the radiosensitivity and chemo-sensitivity of head and neck cancers.

High-throughput and multi-phases identification of autoantibodies in diagnosing early-stage breast cancer and subtypes

Autoantibodies (AAbs) targeted tumor‐associated antigens (TAAs) have the potential for early detection of breast cancer. Here, 574 early‐stage breast cancer (ES‐BC) patients containing 4 subtypes (Luminal A, Luminal B, HER2+, TN), 126 benign breast disease (BBD) patients, and 199 normal healthy controls (NHC) were separated into three‐phases to discover, verify, and validate AAbs. In discovery phase using high‐throughput protein microarray, 37 AAbs with sensitivity of 31.25%‐86.25% and specificity over 73% in ES‐BC, and 40 AAbs with different positive rates between subtypes were identified as candidates. In verification phase, 18 AAbs were significantly increased compared with the Control (BBD and NHC) in focused array. Ten out of 18 AAbs exhibited a significant difference between subtypes (P < .05). In ELISA validation phase, 5 novel AAbs (anti‐KJ901215, ‐FAM49B, ‐HYI, ‐GARS, ‐CRLF3) exhibited significantly higher levels in ES‐BC compared with BBD/NHC (P < .05). The sensitivities of individual AAb and a 5‐AAbs panel were 20.41%‐28.57% and 38.78%, whereas the specificities were over 90% and 85.94%. Simultaneously, 4 AAbs except anti‐GARS differed significantly between TN and non‐TN subtype (P < .05). We constructed 3 random forest classifier models based on AAbs to discriminant ES‐BC from Control or BBD, and to discern TN subtype, which yielded an area under the curve of 0.870, 0.860, and 0.875, respectively. Biological interaction analysis revealed 4 TAAs, except for KJ901215, that were associated with well known proteins of BC. This study discovered and stepwise validated 5 novel AAbs with the potential to diagnose ES‐BC and discern TN subtype, indicating easy‐to‐detect and minimally invasive diagnostic value of serum AAbs ahead of biopsy for future application.

Clinical and Immunological Effects of p53-Targeting Vaccines

Immunotherapy, including immune checkpoint blockade and chimeric antigen receptor T cells, is one of the most promising approaches to treat cancer. Vaccines have been effective in preventing cancers like liver cancer and cervical cancer with a viral etiology. Instead of preventing disease, therapeutic cancer vaccines mobilize the immune system to attack existing cancer. p53 is dysregulated in the majority of human cancers and is a highly promising target for cancer vaccines. Over twenty clinical trials have targeted p53 in malignant diseases using vaccines. In this work, we review the progress of vaccinations with p53 or its peptides as the antigens and summarize the clinical and immunological effects of p53-targeting vaccines from clinical trials. The delivery platforms include p53 peptides, viral vectors, and dendritic cells pulsed with short peptides or transduced by p53-encoding viruses. These studies shed light on the feasibility, safety, and clinical benefit of p53 vaccination in select groups of patients, implicating that p53-targeting vaccines warrant further investigations in experimental animals and human studies.

A Balancing Act: p53 Activity from Tumor Suppression to Pathology and Therapeutic Implications

TP53, encoding the p53 transcription factor, is the most frequently mutated tumor suppressor gene across all human cancer types. While p53 has long been appreciated to induce antiproliferative cell cycle arrest, apoptosis, and senescence programs in response to diverse stress signals, various studies in recent years have revealed additional important functions for p53 that likely also contribute to tumor suppression, including roles in regulating tumor metabolism, ferroptosis, signaling in the tumor microenvironment, and stem cell self-renewal/differentiation. Not only does p53 loss or mutation cause cancer, but hyperactive p53 also drives various pathologies, including developmental phenotypes, premature aging, neurodegeneration, and side effects of cancer therapies. These findings underscore the importance of balanced p53 activity and influence our thinking of how to best develop cancer therapies based on modulating the p53 pathway. Expected final online publication date for the Annual Review of Pathology: Mechanisms of Disease, Volume 17 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

p53 Antibodies as a Diagnostic Marker for Cancer: A Meta-Analysis

Importance: The protein p53 is an unequivocal tumor suppressor that is altered in half of all cancers. The immune system produces systemic p53 autoantibodies (p53 Abs) in many cancer patients. Objective: This systemic review and meta-analysis focuses on the prognostic value of p53 Abs expressed in the serum of patients with solid tumors. Data Sources: All the clinical investigations were searched on PubMed from the first study dated 1993 until May 2021 (date of submission of the manuscript). Study Selection: Studies were included that met the following criteria: (1) participants with cancer; (2) outcome results expressed in relation to the presence of a p53 antibody; (3) a primary outcome (disease-free survival, overall survival or progression-free survival) expressed as hazard ratio (HR). The following exclusion criteria were used: (1) insufficient data available to evaluate outcomes; (2) animal studies; (3) studies with less than 10 participants. As a result, 12 studies were included in the analysis. Data Extraction and Synthesis: PRISMA guidelines were used for abstracting and assessing data quality and validity by three independent observers. The summary estimates were generated using a fixed-effect model (Mantel-Haenszel method) or a random-effect model (DerSimonian-Laird method), depending on the absence or presence of heterogeneity (I²). Main Outcome(s) and Measure(s): The primary study outcome was to determine the prognostic value of p53 Abs from a large population of patients with solid tumors, as determined before data collection. Results: In total, 12 clinical studies involving 2094 patients were included in the meta-analysis, and it was determined that p53 Abs expression in the serum significantly correlated with poorer survival outcomes of cancer patients (95% CI 1.48 [1.24, 1.77]; p < 0.00001). Conclusions and Relevance: This is the first meta-analysis proving the diagnostic utility of p53-Abs for cancer patients in predicting poorer outcomes. The serum-p53 value (s-p53-value) may be useful for future theranostics.

PBRM1 Mutations as a Predictive Biomarker for Immunotherapy in Metastatic Renal Cell Carcinoma: A Systematic Review

INTRODUCTION: Genomic features linked to prediction of response to immunotherapy in metastatic renal cell carcinoma (mRCC) are still lacking. Protein polybromo-1 (PBRM1) mutations have been studied as a potential biomarker of clinical benefit, with conflicting published data so far. MATERIAL AND METHODS: This systematic review was guided by the standards of the PRISMA statement to identify studies involving mRCC, immunotherapy and mutations in PBRM1. The main objective was to assess the relationship between PBRM1 mutations and response to immune checkpoint inhibitors (ICI) in patients with mRCC. RESULTS: After an initial search that identified 422 studies, 8 studies met the eligibility criteria and were selected for the final analysis. Data are included from 2 trials in the first-line treatment setting, and 6 trials in second- or later treatment lines evaluating the relationship between the presence of PBRM1 mutations and clinical benefit (CB) with ICI treatment. Regarding the first-line treatment setting, the analysis of both studies failed to show any CB in patients with PBRM1 mutations treated with ICI. However, for the second- and later treatment lines, the results were mixed. CONCLUSIONS: PBRM1 mutations may be a potential genomic biomarker to predict response to ICI treatment in patients with mRCC, mainly in second- and later treatment lines, but the existence of conflicting data in the literature highlights an important bias in the studies and the need for additional clinical validation in large, prospective trials.

Mutant p53 in Cancer Progression and Targeted Therapies

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