How does p53 induce apoptosis and how does this relate to p53-mediated tumour suppression?

The tumour suppressor gene TP53 is mutated in ~50% of human cancers. In addition to its function in tumour suppression, p53 also plays a major role in the response of malignant as well as nontransformed cells to many anticancer therapeutics, particularly those that cause DNA damage. P53 forms a homotetrameric transcription factor that is reported to directly regulate ~500 target genes, thereby controlling a broad range of cellular processes, including cell cycle arrest, cell senescence, DNA repair, metabolic adaptation and cell death. For a long time, induction of apoptotic death in nascent neoplastic cells was regarded as the principal mechanism by which p53 prevents tumour development. This concept has, however, recently been challenged by the findings that in striking contrast to Trp53-deficient mice, gene-targeted mice that lack the critical effectors of p53-induced apoptosis do not develop tumours spontaneously. Remarkably, even mice lacking all mediators critical for p53-induced apoptosis, G1/S boundary cell cycle arrest and cell senescence do not develop any tumours spontaneously. In this review we discuss current understanding of the mechanisms by which p53 induces cell death and how this affects p53-mediated tumour suppression and the response of malignant cells to anticancer therapy.

Ectopic expression of germline genes drives malignant brain tumor growth in Drosophila

Model organisms such as the fruit fly Drosophila melanogaster can help to elucidate the molecular basis of complex diseases such as cancer. Mutations in the Drosophila gene lethal (3) malignant brain tumor cause malignant growth in the larval brain. Here we show that l(3)mbt tumors exhibited a soma-to-germline transformation through the ectopic expression of genes normally required for germline stemness, fitness, or longevity. Orthologs of some of these genes were also expressed in human somatic tumors. In addition, inactivation of any of the germline genes nanos, vasa, piwi, or aubergine suppressed l(3)mbt malignant growth. Our results demonstrate that germline traits are necessary for tumor growth in this Drosophila model and suggest that inactivation of germline genes might have tumor-suppressing effects in other species.

Apoptotic cell death in disease-Current understanding of the NCCD 2023

Apoptosis is a form of regulated cell death (RCD) that involves proteases of the caspase family. Pharmacological and genetic strategies that experimentally inhibit or delay apoptosis in mammalian systems have elucidated the key contribution of this process not only to (post-)embryonic development and adult tissue homeostasis, but also to the etiology of multiple human disorders. Consistent with this notion, while defects in the molecular machinery for apoptotic cell death impair organismal development and promote oncogenesis, the unwarranted activation of apoptosis promotes cell loss and tissue damage in the context of various neurological, cardiovascular, renal, hepatic, infectious, neoplastic and inflammatory conditions. Here, the Nomenclature Committee on Cell Death (NCCD) gathered to critically summarize an abundant pre-clinical literature mechanistically linking the core apoptotic apparatus to organismal homeostasis in the context of disease.

Mutant TRP53 exerts a target gene-selective dominant-negative effect to drive tumor development

Here, Aubrey et al. researched how mutant TRP53 drives tumor development. Their findings demonstrate a strong functional synergy between deregulated expression of c-MYC and the hot spot mutant TRP53 proteins that distinguishes them from the less frequently occurring TRP53 mutants and that mutant TRP53 drives tumorigenesis primarily through dominant-negative effects.

Mutations in Trp53, prevalent in human cancer, are reported to drive tumorigenesis through dominant-negative effects (DNEs) over wild-type TRP53 function as well as neomorphic gain-of-function (GOF) activity. We show that five TRP53 mutants do not accelerate lymphomagenesis on a TRP53-deficient background but strongly synergize with c-MYC overexpression in a manner that distinguishes the hot spot Trp53 mutations. RNA sequencing revealed that the mutant TRP53 DNE does not globally repress wild-type TRP53 function but disproportionately impacts a subset of wild-type TRP53 target genes. Accordingly, TRP53 mutant proteins impair pathways for DNA repair, proliferation, and metabolism in premalignant cells. This reveals that, in our studies of lymphomagenesis, mutant TRP53 drives tumorigenesis primarily through the DNE, which modulates wild-type TRP53 function in a manner advantageous for neoplastic transformation.

A metabolic map of the DNA damage response identifies PRDX1 in the control of nuclear ROS scavenging and aspartate availability

While cellular metabolism impacts the DNA damage response, a systematic understanding of the metabolic requirements that are crucial for DNA damage repair has yet to be achieved. Here, we investigate the metabolic enzymes and processes that are essential for the resolution of DNA damage. By integrating functional genomics with chromatin proteomics and metabolomics, we provide a detailed description of the interplay between cellular metabolism and the DNA damage response. Further analysis identified that Peroxiredoxin 1, PRDX1, contributes to the DNA damage repair. During the DNA damage response, PRDX1 translocates to the nucleus where it reduces DNA damage-induced nuclear reactive oxygen species. Moreover, PRDX1 loss lowers aspartate availability, which is required for the DNA damage-induced upregulation of de novo nucleotide synthesis. In the absence of PRDX1, cells accumulate replication stress and DNA damage, leading to proliferation defects that are exacerbated in the presence of etoposide, thus revealing a role for PRDX1 as a DNA damage surveillance factor.

Lessons for Patient Engagement in Research in Low- and Middle-Income Countries

Patient engagement in research is marked by partnership between clinicians, scientists, and people with lived experience of a disease, who jointly develop and implement research and disseminate results. Patient engagement in research has been shown to lead to more impactful and relevant findings. There is a global need for quality research contextualized for low- and middle-income countries (LMICs). Patient involvement in research could address this need, yet it remains a practice more commonly employed in high income countries. In this paper, the authors explore LMIC-specific challenges and opportunities for patient engagement in research. Limitations to patient engagement in research include gaps in health infrastructure, socioeconomic status, cultural stigma, and uncertain roles. Potential solutions to address these challenges include strategic national and international research partnerships, initiatives to combat stigma, and sensitization and training of stakeholders in patient engagement in research. Reflecting on their patient engagement experience with eye cancer research in Canada and Kenya, and supported by evidence of patient engagement in other low-resource settings, the authors provide a roadmap for patient engagement in research in LMICs.

Consequences of Zmat3 loss in c-MYC- and mutant KRAS-driven tumorigenesis

TP53 is a critical tumor suppressor that is mutated in approximately 50% of human cancers. Unveiling the downstream target genes of TP53 that fulfill its tumor suppressor function is an area of intense investigation. Zmat3 (also known as Wig-1 or PAG608) is one such downstream target of p53, whose loss in hemopoietic stem cells lacking the apoptosis and cell cycle regulators, Puma and p21, respectively, promotes the development of leukemia. The function of Zmat3 in tumorigenesis however remains unclear. Here, to investigate which oncogenic drivers co-operate with Zmat3 loss to promote neoplastic transformation, we utilized Zmat3 knockout mice in models of c-MYC-driven lymphomagenesis and Kras^G12D-driven lung adenocarcinoma development. Interestingly, unlike loss of p53, Zmat3 germline loss had little impact on the rate of tumor development or severity of malignant disease upon either the c-MYC or Kras^G12D oncogenic activation. Furthermore, loss of Zmat3 failed to rescue Kras^G12D primary lung tumor cells from oncogene-induced senescence. Taken together, we conclude that in the context of c-MYC-driven lymphomagenesis or mutant Kras^G12D-driven lung adenocarcinoma development, additional co-occurring mutations are required to resolve Zmat3 tumor suppressive activity.

Surgical crown lengthening in a population with human immunodeficiency virus: a retrospective analysis)

BACKGROUND

Individuals with human immunodeficiency virus (HIV) have an increased risk of developing health problems, including some that are life threatening. Today, dental treatment for the population with a positive HIV diagnosis (HIV+) is comprehensive. There are limited reports on the outcomes of intraoral surgical therapy in patients with HIV, such as crown lengthening surgery (CLS) with osseous recontouring. This report investigates the outcome of CLS procedures performed at an urban dental school in a population of individuals with HIV. Specifically, this retrospective clinical analysis evaluates the healing response after CLS.

METHODS

Paper and electronic records were examined from the year 2000 to the present. Twenty-one individuals with HIV and immunosuppression, ranging from insignificant to severe, underwent CLS. Pertinent details, including laboratory values, medications, smoking history/status, and postoperative outcomes, were recorded. One such surgery is described in detail with radiographs, photographs, and a videoclip.

RESULTS

Of the 21 patients with HIV examined after CLS, none had postoperative complications, such as delayed healing, infection, or prolonged bleeding. Variations in viral load (<48 to 40,000 copies/mL), CD4 cell count (126 to 1,260 cells/mm(3)), smoking (6 of 21 patients), platelets (130,000 to 369,000 cells/mm(3)), and neutrophils (1.1 to 4.5 × 103 /mm(3)) did not impact surgical healing. In addition, variations in medication regimens (highly active anti-retroviral therapy [18]; on protease inhibitors [1]; no medications [2]) did not have an impact.

CONCLUSIONS

The results of this retrospective analysis show the absence of postoperative complications after CLS in this population with HIV. Additional investigation into this area will help health care practitioners increase the range of surgical services provided to this group of patients.

Evaluating ChatGPT on Orbital and Oculofacial Disorders: Accuracy and Readability Insights

PURPOSE

To assess the accuracy and readability of responses generated by the artificial intelligence model, ChatGPT (version 4.0), to questions related to 10 essential domains of orbital and oculofacial disease.

METHODS

A set of 100 questions related to the diagnosis, treatment, and interpretation of orbital and oculofacial diseases was posed to ChatGPT 4.0. Responses were evaluated by a panel of 7 experts based on appropriateness and accuracy, with performance scores measured on a 7-item Likert scale. Inter-rater reliability was determined via the intraclass correlation coefficient.

RESULTS

The artificial intelligence model demonstrated accurate and consistent performance across all 10 domains of orbital and oculofacial disease, with an average appropriateness score of 5.3/6.0 ("mostly appropriate" to "completely appropriate"). Domains of cavernous sinus fistula, retrobulbar hemorrhage, and blepharospasm had the highest domain scores (average scores of 5.5 to 5.6), while the proptosis domain had the lowest (average score of 5.0/6.0). The intraclass correlation coefficient was 0.64 (95% CI: 0.52 to 0.74), reflecting moderate inter-rater reliability. The responses exhibited a high reading-level complexity, representing the comprehension levels of a college or graduate education.

CONCLUSIONS

This study demonstrates the potential of ChatGPT 4.0 to provide accurate information in the field of ophthalmology, specifically orbital and oculofacial disease. However, challenges remain in ensuring accurate and comprehensive responses across all disease domains. Future improvements should focus on refining the model's correctness and eventually expanding the scope to visual data interpretation. Our results highlight the vast potential for artificial intelligence in educational and clinical ophthalmology contexts.

Patient-reported outcome measures for retinoblastoma: a scoping review

BACKGROUND

Retinoblastoma is a childhood retinal cancer with lifelong consequences such as vision loss and increased risk of second cancer. Patient-reported outcome measures (PROMs) are instruments that measure outcomes related to health directly reported by patients. The purpose of this study was to determine the scope, characteristics and quality of PROMs used in retinoblastoma and related fields of pediatric ophthalmology and pediatric oncology.

METHODS

Databases MEDLINE and Embase were searched for studies in the English language that reported on PROMs used in retinoblastoma, pediatric oncology, or pediatric ophthalmology; grey literature and studies reporting on developmental PROM phases were excluded. PROMs were grouped by the construct measured and domains assessed, and classified as condition-specific or generic. A subsequent search was then conducted in MEDLINE and Embase for studies assessing measurement properties of the identified PROMs. PROMs with associated studies were assessed for their methodologic quality using the COnsensus-based standard for the Selection of health Measurement INstruments (COSMIN) strategy.

RESULTS

Among 110 eligible studies uncovered by the database searches, 143 PROMs were identified: one retinoblastoma-specific, 56 ophthalmology- and 86 oncology-related. The most common construct measured was 'health-related quality of life' and the most common domain assessed was emotional well-being. Of the 143 PROMs, 100 had associated validation studies; the one retinoblastoma-specific PROM was not validated. Quality assessment revealed 34/100 PROMs received a score of sufficient quality in both subcategories of 'overall content validity'; 3/100 received a score of sufficient quality in both subcategories of 'internal structure'; 0/100 received a score of sufficient quality in all three subcategories of 'remaining measurement properties'. The Patient-Reported Outcome Measure Information System (PROMIS) Pediatric Profile-25 was the highest-scoring PROM identified, meeting COSMIN standards for 2/3 measurement property categories (and 5/7 subcategories). Eleven additional PROMs were identified which had sufficient scores in 1/3 measurement property categories (and 5/7 subcategories).

CONCLUSION

The study identified several PROMs from the pediatric ophthalmology and pediatric oncology literature that could be relevant to the retinoblastoma population, but many have limits to their validation. Future development of a retinoblastoma-specific PROM, performed in partnership with retinoblastoma patients to support optimal content validity, could first focus on the selection and definition of the optimal construct to measure, followed potentially by adaptation and further validation of the relevant PROMs with strong methodologic quality identified in this study.

Effect of bilingualism on visual tracking attention and resistance to distraction

Speaking more than one language has been associated with enhanced cognitive capacities. Here we evaluated whether bilingual individuals have advantages in visual tracking attention. Adult bilingual (n = 35) and monolingual (n = 35) participants were tested in the Multiple Object Tracking task (MOT). In one condition, the MOT was performed by itself establishing the baseline performance of each group, and in the other condition, it was performed while participants counted backward out loud in their mother tongue. At baseline, the average speed tracking threshold of bilinguals was not better than that of the monolinguals. Importantly, for bilinguals, counting backward decreased their threshold by only 15%, but, for monolinguals, it decreased it three times as much. This result suggests that bilingualism confers advantages to visual tracking attention when dual tasking is required, extending the evidence that bilingualism affords cognitive benefits beyond verbal communication.

Abstract 3427: Finding critical cancer driving and cancer suppressing genes using functional genomics screening in vivo

P53 is one of the most potent tumour suppressors and its activity is also required for cancer cells to respond to diverse chemotherapeutic drugs. Focused functional genetic screens in haematopoietic cells in vivo revealed DNA repair to be one of the most critical downstream pathways for p53's tumour suppressive function. Recently, we extended our search for novel tumour suppressor genes acting potentially outside the p53 tumour suppressor pathway. To this end, we performed whole genome CRISPR/Cas9 knockout screening in vivo, using the Eµ-Myc transgenic mouse model. This identified previously unknown genes and hence pathways, which upon deletion/mutation lead to the acceleration of tumour onset. Amongst these novel tumour suppressor genes, we identified the GATOR1 members DEPDC5 and NPRL3, which are known inhibitors of the mTOR pathway. Interestingly, drug mediated inhibition of mTOR activity with rapamycin or Torin1 in GATOR1 deficient Eµ-Myc cells led to efficient killing of these malignant cells, which was in striking contrast to control Eµ-Myc lymphoma cells that were resistant to this treatment. In parallel we conducted CRISPR/Cas9 screens for identifying p53 bound promoter and enhancer elements in haematopoietic cells in vivo. Excitingly, we observed that targeting the NPRL3 promoter led to accelerated tumour onset in the Eµ-Myc transgenic model, suggesting that NPRL3 is under direct transcriptional control of p53. These results indicate that p53 mediated shutdown of the mTOR pathway through upregulation of the GATOR1 member NPRL3 is a critical tumour suppressive function of p53.

Citation Format: Marco Josef Herold, Shinsuke Mizutani, Yexuan Deng, Ana Janic, Andrew Kueh, Martin Pal, Stephen Wilcox, Lin Tai, Gemma L. Kelly, Andreas Strasser. Finding critical cancer driving and cancer suppressing genes using functional genomics screening in vivo [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3427.

Values of Retinoblastoma Survivors and Parents Regarding Treatment Outcomes: A Qualitative Study

PURPOSE

Retinoblastoma is an aggressive pediatric eye cancer. Patient-reported outcome measures reveal important insights into how patients perceive their own health. Currently, there is no widely used or validated measure for assessment of retinoblastoma outcomes. The purpose of this research was to uncover which treatment outcomes that retinoblastoma survivors and their parents value, to inform the development of a future measure.

METHODS

This qualitative, cross-sectional study included retinoblastoma survivors age 6 years and older and parents of retinoblastoma survivors. Participants who did not demonstrate fluency in English were excluded. Study participants participated in semistructured interviews or focus groups, either in person at The Hospital for Sick Children, Toronto, Canada, or through secure videoconference, between March 3, 2019, and January 25, 2020. Iterative rounds of opening coding, codebook development, and coresearcher analysis were used to identify key emergent themes and subthemes.

RESULTS

Seventeen adults participated in six focus groups. Nine pediatric survivors participated in individual interviews. Four common themes emerged from all participant groups: (1) definition of treatment success, (2) enucleation-acceptance and challenges, (3) treatment outcomes to measure, and (4) need for outcome reporting. An additional, unique theme was identified in all pediatric discussions: worries and coping mechanisms. Treatment outcomes deemed valuable were related to the following domains: psychosocial outcomes, daily functioning, functional vision, retinoblastoma education, cosmetic outcomes, and secondary eye conditions.

CONCLUSION

This study represents the first stage in the development of a retinoblastoma-specific patient-reported outcome measure. The findings reveal insight into what outcomes are valued by survivors after treatment and offer promise to improve outcomes assessment for retinoblastoma.

Combined absence of TRP53 target genes ZMAT3, PUMA and p21 cause a high incidence of cancer in mice

Transcriptional activation of target genes is essential for TP53-mediated tumour suppression, though the roles of the diverse TP53-activated target genes in tumour suppression remains poorly understood. Knockdown of ZMAT3, an RNA-binding zinc-finger protein involved in regulating alternative splicing, in haematopoietic cells by shRNA caused leukaemia only with the concomitant absence of the PUMA and p21, the critical effectors of TRP53-mediated apoptosis and cell cycle arrest respectively. We were interested to further investigate the role of ZMAT3 in tumour suppression beyond the haematopoietic system. Therefore, we generated Zmat3 knockout and compound gene knockout mice, lacking Zmat3 and p21, Zmat3 and Puma or all three genes. Puma-/-p21-/-Zmat3-/- triple knockout mice developed tumours at a significantly higher frequency compared to wild-type, Puma-/-Zmat3-/- or p21-/-Zmat3-/-deficient mice. Interestingly, we observed that the triple knockout and Puma-/-Zmat3-/- double deficient animals succumbed to lymphoma, while p21-/-Zmat3-/- animals developed mainly solid cancers. This analysis suggests that in addition to ZMAT3 loss, additional TRP53-regulated processes must be disabled simultaneously for TRP53-mediated tumour suppression to fail. Our findings reveal that the absence of different TRP53 regulated tumour suppressive processes changes the tumour spectrum, indicating that different TRP53 tumour suppressive pathways are more critical in different tissues.

Decoding p53 tumor suppression: a crosstalk between genomic stability and epigenetic control?

Genomic instability, a hallmark of cancer, is a direct consequence of the inactivation of the tumor suppressor protein p53. Genetically modified mouse models and human tumor samples have revealed that p53 loss results in extensive chromosomal abnormalities, from copy number alterations to structural rearrangements. In this perspective article we explore the multifaceted relationship between p53, genomic stability, and epigenetic control, highlighting its significance in cancer biology. p53 emerges as a critical regulator of DNA repair mechanisms, influencing key components of repair pathways and directly participating in DNA repair processes. p53 role in genomic integrity however extends beyond its canonical functions. p53 influences also epigenetic landscape, where it modulates DNA methylation and histone modifications. This epigenetic control impacts the expression of genes involved in tumor suppression and oncogenesis. Notably, p53 ability to ensure cellular response to DNA demethylation contributes to the maintenance of genomic stability by preventing unscheduled transcription of repetitive non-coding genomic regions. This latter indicates a causative relationship between the control of epigenetic stability and the maintenance of genomic integrity in p53-mediated tumor suppression. Understanding these mechanisms offers promising avenues for innovative therapeutic strategies targeting epigenetic dysregulation in cancer and emphasizes the need for further research to unravel the complexities of this relationship. Ultimately, these insights hold the potential to transform cancer treatment and prevention strategies.

The TP53-activated E3 ligase RNF144B is a tumour suppressor that prevents genomic instability

BACKGROUND

TP53, the most frequently mutated gene in human cancers, orchestrates a complex transcriptional program crucial for cancer prevention. While certain TP53-dependent genes have been extensively studied, others, like the recently identified RNF144B, remained poorly understood. This E3 ubiquitin ligase has shown potent tumor suppressor activity in murine Eμ Myc-driven lymphoma, emphasizing its significance in the TP53 network. However, little is known about its targets and its role in cancer development, requiring further exploration. In this work, we investigate RNF144B's impact on tumor suppression beyond the hematopoietic compartment in human cancers.

METHODS

Employing TP53 wild-type cells, we generated models lacking RNF144B in both non-transformed and cancerous cells of human and mouse origin. By using proteomics, transcriptomics, and functional analysis, we assessed RNF144B's impact in cellular proliferation and transformation. Through in vitro and in vivo experiments, we explored proliferation, DNA repair, cell cycle control, mitotic progression, and treatment resistance. Findings were contrasted with clinical datasets and bioinformatics analysis.

RESULTS

Our research underscores RNF144B's pivotal role as a tumor suppressor, particularly in lung adenocarcinoma. In both human and mouse oncogene-expressing cells, RNF144B deficiency heightened cellular proliferation and transformation. Proteomic and transcriptomic analysis revealed RNF144B's novel function in mediating protein degradation associated with cell cycle progression, DNA damage response and genomic stability. RNF144B deficiency induced chromosomal instability, mitotic defects, and correlated with elevated aneuploidy and worse prognosis in human tumors. Furthermore, RNF144B-deficient lung adenocarcinoma cells exhibited resistance to cell cycle inhibitors that induce chromosomal instability.

CONCLUSIONS

Supported by clinical data, our study suggests that RNF144B plays a pivotal role in maintaining genomic stability during tumor suppression.