Whole chromosome instability resulting from the synergistic effects of pRB and p53 inactivation

Methylation sites of human papillomavirus 16 as potential biomarkers for cervical cancer progression

Objective

To investigate the methylation levels at 13 specific sites of the human papillomavirus 16 (HPV16) L1 gene as potential biomarkers for the diagnosis of cervical cancer.

Methods

Samples were collected from the gynecological outpatient and inpatient departments of the Xinjiang Uygur Autonomous Region People's Hospital. A total of 107 women participated in this study, including 54 with cervical cancer (32 Uygur, 22 Han) and 53 with cervical inflammation (32 Uygur, 21 Han). Methylation analysis was performed using pyrosequencing to quantitatively assess methylation levels at specified CpG sites within the HPV16 L1 gene.

Results

High methylation levels were predominantly observed at sites 5927, 5963 and 6367 in cervical cancer cells compared with inflammatory cells. Methylation patterns exhibited no significant differences between the Han and Uygur ethnic groups but correlated with viral load and age within each group. Receiver operating characteristic curve analyses of these methylation sites indicated high diagnostic accuracy in distinguishing between high-grade lesions and less severe conditions.

Conclusions

Methylation of specific CpG sites in the HPV16 L1 gene holds promise as a biomarker for cervical cancer progression. The gene locus at position 6367 has important features in the methylation pattern of cervical cancer, and high accuracy shown in diagnosis make it a potential biomarker for early diagnosis of cervical cancer.

Comprehensive Analysis of the Mechanism of Anoikis in Hepatocellular Carcinoma

Background

Hepatocellular carcinoma (HCC), ranking as the second-leading cause of global mortality among malignancies, poses a substantial burden on public health worldwide. Anoikis, a type of programmed cell death, serves as a barrier against the dissemination of cancer cells to distant organs, thereby constraining the progression of cancer. Nevertheless, the mechanism of genes related to anoikis in HCC is yet to be elucidated.

Methods

This paper's data (TCGA-HCC) were retrieved from the database of the Cancer Genome Atlas (TCGA). Differential gene expression with prognostic implications for anoikis was identified by performing both the univariate Cox and differential expression analyses. Through unsupervised cluster analysis, we clustered the samples according to these DEGs. By employing the least absolute shrinkage and selection operator Cox regression analysis (CRA), a clinical predictive gene signature was generated from the DEGs. The Cell-Type Identification by Estimating Relative Subsets of RNA Transcripts (CIBERSORT) algorithm was used to determine the proportions of immune cell types. The external validation data (GSE76427) were procured from Gene Expression Omnibus (GEO) to verify the performance of the clinical prognosis gene signature. Western blotting and immunohistochemistry (IHC) analysis confirmed the expression of risk genes.

Results

In total, 23 prognostic DEGs were identified. Based on these 23 DEGs, the samples were categorized into four distinct subgroups (clusters 1, 2, 3, and 4). In addition, a clinical predictive gene signature was constructed utilizing ETV4, PBK, and SLC2A1. The gene signature efficiently distinguished individuals into two risk groups, specifically low and high, demonstrating markedly higher survival rates in the former group. Significant correlations were observed between the expression of these risk genes and a variety of immune cells. Moreover, the outcomes from the validation cohort analysis aligned consistently with those obtained from the training cohort analysis. The results of Western blotting and IHC showed that ETV4, PBK, and SLC2A1 were upregulated in HCC samples.

Conclusion

The outcomes of this paper underscore the effectiveness of the clinical prognostic gene signature, established utilizing anoikis-related genes, in accurately stratifying patients. This signature holds promise in advancing the development of personalized therapy for HCC.

Genomic and transcriptomic profiling of combined small-cell lung cancer through microdissection: unveiling the transformational pathway of mixed subtype

BACKGROUND

Combined small-cell lung carcinoma (cSCLC) represents a rare subtype of SCLC, the mechanisms governing the evolution of cancer genomes and their impact on the tumor immune microenvironment (TIME) within distinct components of cSCLC remain elusive.

METHODS

Here, we conducted whole-exome and RNA sequencing on 32 samples from 16 cSCLC cases.

RESULTS

We found striking similarities between two components of cSCLC-LCC/LCNEC (SCLC combined with large-cell carcinoma/neuroendocrine) in terms of tumor mutation burden (TMB), tumor neoantigen burden (TNB), clonality structure, chromosomal instability (CIN), and low levels of immune cell infiltration. In contrast, the two components of cSCLC-ADC/SCC (SCLC combined with adenocarcinoma/squamous-cell carcinoma) exhibited a high level of tumor heterogeneity. Our investigation revealed that cSCLC originated from a monoclonal source, with two potential transformation modes: from SCLC to SCC (mode 1) and from ADC to SCLC (mode 2). Therefore, cSCLC might represent an intermediate state, potentially evolving into another histological tumor morphology through interactions between tumor and TIME surrounding it. Intriguingly, RB1 inactivation emerged as a factor influencing TIME heterogeneity in cSCLC, possibly through neoantigen depletion.

CONCLUSIONS

Together, these findings delved into the clonal origin and TIME heterogeneity of different components in cSCLC, shedding new light on the evolutionary processes underlying this enigmatic subtype.

Exosomes from Adipose-Tissue-Derived Stem Cells Induce Proapoptotic Gene Expression in Breast Tumor Cell Line

Lipofilling is an option for breast reconstruction after tumor resection to avoid the complications of an implant-based reconstruction. Although some concerns exist regarding the oncological safety of tissue rich in mesenchymal stem cells with their proangiogenic and proliferation-supportive properties, there are also reports that adipose-tissue-derived stem cells can exhibit antitumoral properties. We isolated primary adipose-tissue-derived stem cells. Both conditioned medium and exosomes were harvested from the cell culture and used to treat the breast cancer cell line MCF-7. Cell viability, cytotoxicity, and gene expression of MCF-7 cells in response to the indirect co-culture were evaluated. MCF-7 cells incubated with exosomes from adipose-tissue-derived stem cells show reduced cell viability in comparison to MCF-7 cells incubated with adipose-tissue-derived stem-cell-conditioned medium. Expression of proapoptotic genes was upregulated, and expression of antiapoptotic genes was downregulated. The debate about the oncological safety of autologous fat grafting after tumor resection continues. Here, we show that exosomes from adipose-tissue-derived stem cells exhibit some antitumoral properties on breast cancer cell line MCF-7.

Permission to pass: on the role of p53 as a gatekeeper for aneuploidy

Aneuploidy-the karyotype state in which the number of chromosomes deviates from a multiple of the haploid chromosome set-is common in cancer, where it is thought to facilitate tumor initiation and progression. However, it is poorly tolerated in healthy cells: during development and tissue homeostasis, aneuploid cells are efficiently cleared from the population. It is still largely unknown how cancer cells become, and adapt to being, aneuploid. P53, the gatekeeper of the genome, has been proposed to guard against aneuploidy. Aneuploidy in cancer genomes strongly correlates with mutations in TP53, and p53 is thought to prevent the propagation of aneuploid cells. Whether p53 also participates in preventing the mistakes in cell division that lead to aneuploidy is still under debate. In this review, we summarize the current understanding of the role of p53 in protecting cells from aneuploidy, and we explore the consequences of functional p53 loss for the propagation of aneuploidy in cancer.

Establishment and validation of an immune infiltration predictive model for ovarian cancer

BACKGROUND

The most prevalent mutation in ovarian cancer is the TP53 mutation, which impacts the development and prognosis of the disease. We looked at how the TP53 mutation associates the immunophenotype of ovarian cancer and the prognosis of the disease.

METHODS

We investigated the state of TP53 mutations and expression profiles in culturally diverse groups and datasets and developed an immune infiltration predictive model relying on immune-associated genes differently expressed between TP53 WT and TP53 MUT ovarian cancer cases. We aimed to construct an immune infiltration predictive model (IPM) to enhance the prognosis of ovarian cancer and investigate the impact of the IPM on the immunological microenvironment.

RESULTS

TP53 mutagenesis affected the expression of seventy-seven immune response-associated genes. An IPM was implemented and evaluated on ovarian cancer patients to distinguish individuals with low- and high-IPM subgroups of poor survival. For diagnostic and therapeutic use, a nomogram is thus created. According to pathway enrichment analysis, the pathways of the human immune response and immune function abnormalities were the most associated functions and pathways with the IPM genes. Furthermore, patients in the high-risk group showed low proportions of macrophages M1, activated NK cells, CD8+ T cells, and higher CTLA-4, PD-1, PD-L1, and TIM-3 than patients in the low-risk group.

CONCLUSIONS

The IPM model may identify high-risk patients and integrate other clinical parameters to predict their overall survival, suggesting it is a potential methodology for optimizing ovarian cancer prognosis.

Seeing is believing: the impact of RB on nuclear organization

The retinoblastoma tumor suppressor (RB) prevents G1 to S cell cycle transition by inhibiting E2F activity. This function requires that RB remains un- or underphosphorylated (the so-called active forms of RB). Recently, we showed that active forms of RB cause widespread changes in nuclear architecture that are visible under a microscope. These phenotypes did not correlate with cell cycle arrest or repression of the E2F transcriptional program, but appeared later, and were associated with the appearance of autophagy or in IMR-90 cells with senescence markers. In this perspective, we describe the relative timing of these RB-induced events and discuss the mechanisms that may underlie RB-induced chromatin dispersion. We consider the relationship between RB-induced dispersion, autophagy, and senescence and the potential connection between dispersion and cell cycle exit.

Inactivation of RB1, CDKN2A, and TP53 have distinct effects on genomic stability at side-by-side comparison in karyotypically normal cells

Chromosomal instability is a common feature in malignant tumors. Previous studies have indicated that inactivation of the classical tumor suppressor genes RB1, CDKN2A, and TP53 may contribute to chromosomal aberrations in cancer by disrupting different aspects of the cell cycle and DNA damage checkpoint machinery. We performed a side-by-side comparison of how inactivation of each of these genes affected chromosomal stability in vitro. Using CRISPR-Cas9 technology, RB1, CDKN2A, and TP53 were independently knocked out in karyotypically normal immortalized cells, after which these cells were followed over time. Bulk RNA sequencing revealed a distinct phenotype with upregulation of pathways related to cell cycle control and proliferation in all three knockouts. Surprisingly, the RB1 and CDKN2A knocked out cell lines did not harbor more copy number aberrations than wild-type cells, despite culturing for months. The TP53-knocked out cells, in contrast, showed a massive amount of copy number alterations and saltatory evolution through whole genome duplication. This side-by-side comparison indicated that the effects on chromosomal stability from inactivation of RB1 and CDKN2A are negligible compared to inactivation of TP53, under the same conditions in a nonstressful environment, even though partly overlapping regulatory pathways are affected. Our data suggest that loss of RB1 and CDKN2A alone is not enough to trigger surviving detectable aneuploid clones while inactivation of TP53 on its own caused massive CIN leading to saltatory clonal evolution in vitro and clonal selection.

Hepatocellular Carcinoma: Current Therapeutic Algorithm for Localized and Advanced Disease

Hepatocellular carcinoma (HCC) is the most common primary liver cancer in patients with liver cirrhosis of various etiologies. In recent years, there has been an advance in the knowledge of molecular mechanisms and a better staging definition of patients which has allowed the development of new therapies that have entered the therapeutic workup of these patients. Deep information on molecular drivers of HCC contributed to the development of targeted therapies with remarkable benefits. The novel strategies of targeting immune evasion using immune checkpoint inhibitors and CAR-T and TCR-T therapeutics have also shown promising results. For advanced diseases, the therapeutic algorithm has been recently updated, thanks to the efficacy of combining immunotherapy and antiangiogenic therapy in the first-line setting, and new drugs, both as single-agents or combinations, are currently under investigation.

Novel insights into RB1 mutation

Since the discovery of the retinoblastoma susceptibility gene (RB1) decades ago, RB1 has been regarded as a prototype tumor suppressor gene providing a paradigm for tumor genetic research. Constant research has updated the understanding of RB1-related pathways and their impact on tumor and nontumor diseases. Mutation of RB1 gene has been observed in multiple types of malignant tumors including prostate cancer, lung cancer, breast cancer, and almost every familial and sporadic case of retinoblastoma. Even if well-known and long-investigated, the application potential of RB1 mutation has not been fully tapped. In this review, we focus on the mechanism underlying RB1 mutation during oncogenesis. Therapeutically, we have further discussed potential clinical strategies by targeting RB1-mutated cancers. The unsolved problems and prospects of RB1 mutation are also discussed.

Cold and heterogeneous T cell repertoire is associated with copy number aberrations and loss of immune genes in small-cell lung cancer

Small-cell lung cancer (SCLC) is speculated to harbor complex genomic intratumor heterogeneity (ITH) associated with high recurrence rate and suboptimal response to immunotherapy. Here, using multi-region whole exome/T cell receptor (TCR) sequencing as well as immunohistochemistry, we reveal a rather homogeneous mutational landscape but extremely cold and heterogeneous TCR repertoire in limited-stage SCLC tumors (LS-SCLCs). Compared to localized non-small cell lung cancers, LS-SCLCs have similar predicted neoantigen burden and genomic ITH, but significantly colder and more heterogeneous TCR repertoire associated with higher chromosomal copy number aberration (CNA) burden. Furthermore, copy number loss of IFN-γ pathway genes is frequently observed and positively correlates with CNA burden. Higher mutational burden, higher T cell infiltration and positive PD-L1 expression are associated with longer overall survival (OS), while higher CNA burden is associated with shorter OS in patients with LS-SCLC.

Construction and Validation of a Reliable Six-Gene Prognostic Signature Based on the TP53 Alteration for Hepatocellular Carcinoma

BACKGROUND

The high mutation rate of TP53 in hepatocellular carcinoma (HCC) makes it an attractive potential therapeutic target. However, the mechanism by which TP53 mutation affects the prognosis of HCC is not fully understood.

MATERIAL AND APPROACH

This study downloaded a gene expression profile and clinical-related information from The Cancer Genome Atlas (TCGA) database and the international genome consortium (ICGC) database. We used Gene Set Enrichment Analysis (GSEA) to determine the difference in gene expression patterns between HCC samples with wild-type TP53 (n=258) and mutant TP53 (n=116) in the TCGA cohort. We screened prognosis-related genes by univariate Cox regression analysis and Kaplan-Meier (KM) survival analysis. We constructed a six-gene prognostic signature in the TCGA training group (n=184) by Lasso and multivariate Cox regression analysis. To assess the predictive capability and applicability of the signature in HCC, we conducted internal validation, external validation, integrated analysis and subgroup analysis.

RESULTS

A prognostic signature consisting of six genes (EIF2S1, SEC61A1, CDC42EP2, SRM, GRM8, and TBCD) showed good performance in predicting the prognosis of HCC. The area under the curve (AUC) values of the ROC curve of 1-, 2-, and 3-year survival of the model were all greater than 0.7 in each independent cohort (internal testing cohort, n = 181; TCGA cohort, n = 365; ICGC cohort, n = 229; whole cohort, n = 594; subgroup, n = 9). Importantly, by gene set variation analysis (GSVA) and the single sample gene set enrichment analysis (ssGSEA) method, we found three possible causes that may lead to poor prognosis of HCC: high proliferative activity, low metabolic activity and immunosuppression.

CONCLUSION

Our study provides a reliable method for the prognostic risk assessment of HCC and has great potential for clinical transformation.

Are Molecular Alterations Linked to Genetic Instability Worth to Be Included as Biomarkers for Directing or Excluding Melanoma Patients to Immunotherapy?

The improvement of the immunotherapeutic potential in most human cancers, including melanoma, requires the identification of increasingly detailed molecular features underlying the tumor immune responsiveness and acting as disease-associated biomarkers. In recent past years, the complexity of the immune landscape in cancer tissues is being steadily unveiled with a progressive better understanding of the plethora of actors playing in such a scenario, resulting in histopathology diversification, distinct molecular subtypes, and biological heterogeneity. Actually, it is widely recognized that the intracellular patterns of alterations in driver genes and loci may also concur to interfere with the homeostasis of the tumor microenvironment components, deeply affecting the immune response against the tumor. Among others, the different events linked to genetic instability—aneuploidy/somatic copy number alteration (SCNA) or microsatellite instability (MSI)—may exhibit opposite behaviors in terms of immune exclusion or responsiveness. In this review, we focused on both prevalence and impact of such different types of genetic instability in melanoma in order to evaluate whether their use as biomarkers in an integrated analysis of the molecular profile of such a malignancy may allow defining any potential predictive value for response/resistance to immunotherapy.

Cep55 overexpression promotes genomic instability and tumorigenesis in mice

High expression of centrosomal protein CEP55 has been correlated with clinico-pathological parameters across multiple human cancers. Despite significant in vitro studies and association of aberrantly overexpressed CEP55 with worse prognosis, its causal role in vivo tumorigenesis remains elusive. Here, using a ubiquitously overexpressing transgenic mouse model, we show that Cep55 overexpression causes spontaneous tumorigenesis and accelerates Trp53^+/− induced tumours in vivo. At the cellular level, using mouse embryonic fibroblasts (MEFs), we demonstrate that Cep55 overexpression induces proliferation advantage by modulating multiple cellular signalling networks including the hyperactivation of the Pi3k/Akt pathway. Notably, Cep55 overexpressing MEFs have a compromised Chk1-dependent S-phase checkpoint, causing increased replication speed and DNA damage, resulting in a prolonged aberrant mitotic division. Importantly, this phenotype was rescued by pharmacological inhibition of Pi3k/Akt or expression of mutant Chk1 (S280A) protein, which is insensitive to regulation by active Akt, in Cep55 overexpressing MEFs. Moreover, we report that Cep55 overexpression causes stabilized microtubules. Collectively, our data demonstrates causative effects of deregulated Cep55 on genome stability and tumorigenesis which have potential implications for tumour initiation and therapy development.

Sinha et al. demonstrate that overexpression of centrosomal protein Cep55 in mice is sufficient to cause a wide-spectrum of cancer via multiple mechanisms including hyperactivation of the Pi3k/Akt pathway, stabilized microtubules and a defective replication checkpoint response. These findings are relevant to human cancers as high CEP55 expression is associated with worse prognosis across multiple cancer types.

Short-term in vitro glutamine restriction differentially impacts the chromosomal stability of transformed and non-transformed cells

Glutamine (Gln) is a non-essential amino acid central for generating building blocks and cellular energy in tumours and rapidly proliferating non-transformed cells. However, the influence of Gln on regulating chromosomal stability of transformed and non-transformed cells remain poorly understand. We hypothesised that Gln is required for maintaining a homeostatic level of chromosomal stability. To this end, transformed cells HeLa and A375 and non-transformed cells NCM460 and HUVEC cells were intervened with varying concentrations of Gln (10, 1, 0.1 and 0.01 mM), with or without cisplatin (0.1 µg/ml), for 24 h. The cytokinesis-block micronucleus (MN) assay was used to determine chromosomal instability (CIN), the extent of which is reflected by the frequency of MN, nucleoplasmic bridge (NPB) and nuclear bud (NB). We demonstrated an unexpected decrease in the spontaneous rate of MN, but not NPB and NB, after Gln restriction in HeLa and A375 cells. Gln restriction reduced cisplatin-induced MN, but not NPB and NB, in HeLa and A375 cells. We further revealed that Gln restriction suppressed the proliferation of HeLa cells with high CIN induced by nocodazole, partially explaining why Gln restriction decreased the frequency of spontaneous and cisplatin-induced MN in transformed cells. In contrast, Gln restriction increased MN and NB, but not NPB, in NCM460 cells. In HUVEC cells, Gln restriction increased MN, NPB and NB. Meanwhile, Gln restriction sensitised NCM460 cells to cisplatin-induced genotoxicity. A similar but more pronounced pattern was observed in HUVEC cells. Collectively, these results suggest that the in vitro influences of Gln metabolism on CIN depend on cellular contexts: Transformed cells require high Gln to fine tune their CIN in an optimal rate to maximise genomic heterogeneity and fitness, whereas non-transformed cells need high Gln to prevent CIN.

Retinoblastoma: Etiology, Modeling, and Treatment

Retinoblastoma is a retinal cancer that is initiated in response to biallelic loss of RB1 in almost all cases, together with other genetic/epigenetic changes culminating in the development of cancer. RB1 deficiency makes the retinoblastoma cell-of-origin extremely susceptible to cancerous transformation, and the tumor cell-of-origin appears to depend on the developmental stage and species. These are important to establish reliable preclinical models to study the disease and develop therapies. Although retinoblastoma is the most curable pediatric cancer with a high survival rate, advanced tumors limit globe salvage and are often associated with high-risk histopathological features predictive of dissemination. The advent of chemotherapy has improved treatment outcomes, which is effective for globe preservation with new routes of targeted drug delivery. However, molecularly targeted therapeutics with more effectiveness and less toxicity are needed. Here, we review the current knowledge concerning retinoblastoma genesis with particular attention to the genomic and transcriptomic landscapes with correlations to clinicopathological characteristics, as well as the retinoblastoma cell-of-origin and current disease models. We further discuss current treatments, clinicopathological correlations, which assist in guiding treatment and may facilitate globe preservation, and finally we discuss targeted therapeutics for future treatments.

Protein expression profiling identifies differential modulation of homologous recombination by platinum-based antitumor agents

PURPOSE

Oxaliplatin and satraplatin demonstrate activity against cisplatin-resistant tumor cells. Although the two platinum analogs are structurally-related, oxaliplatin is more active. Therefore, studies focusing on protein expression profiling were undertaken to identify the molecular mechanism for the difference in antitumor activity.

METHODS

We included cisplatin as reference and DAP as a Pt(IV)-prodrug of oxaliplatin to offset Pt(IV) status of satraplatin, and utilized A2780, cisplatin-resistant 2780CP/Cl-16, U2OS, and HCT-116 tumor cells in the investigation. Protein expressions following drug exposures were examined by reverse-phase protein array and ingenuity pathway analysis. Cell cycle was assessed by flow cytometry, cytotoxicity by growth inhibition assay, and homologous recombination (HR) by a GFP reporter assay.

RESULTS

Clustering analysis paired oxaliplatin with DAP and, surprisingly, satraplatin with cisplatin. This correlated with differential upregulation of p53/p21 pathway, with S and G2/M arrests by cisplatin and satraplatin in contrast to G1 arrest by oxaliplatin and DAP. Moreover, Rad51 and BRCA1 were severely downregulated by oxaliplatin and DAP, but not cisplatin and satraplatin. As a result, HR was inhibited only by oxaliplatin and DAP and this also contributed to their greater drug activity over cisplatin and satraplatin.

CONCLUSIONS

Oxaliplatin and DAP robustly activate p53 and p21, which downregulate HR proteins to enhance drug activity. More significantly, since oxaliplatin induces a BRCAness state, it may have potential against BRCA-proficient cancers. Satraplatin, on the other hand, resembled cisplatin in its protein expression profile, which indicates that small changes in chemical structure can substantially alter signal transduction pathways to modulate drug activity.

RBL1 (p107) functions as tumor suppressor in glioblastoma and small-cell pancreatic neuroendocrine carcinoma in Xenopus tropicalis

Alterations of the retinoblastoma and/or the p53 signaling network are associated with specific cancers such as high-grade astrocytoma/glioblastoma, small-cell lung cancer (SCLC), choroid plexus tumors, and small-cell pancreatic neuroendocrine carcinoma (SC-PaNEC). However, the intricate functional redundancy between RB1 and the related pocket proteins RBL1/p107 and RBL2/p130 in suppressing tumorigenesis remains poorly understood. Here we performed lineage-restricted parallel inactivation of rb1 and rbl1 by multiplex CRISPR/Cas9 genome editing in the true diploid Xenopus tropicalis to gain insight into this in vivo redundancy. We show that while rb1 inactivation is sufficient to induce choroid plexus papilloma, combined rb1 and rbl1 inactivation is required and sufficient to drive SC-PaNEC, retinoblastoma and astrocytoma. Further, using a novel Li-Fraumeni syndrome-mimicking tp53 mutant X. tropicalis line, we demonstrate increased malignancy of rb1/rbl1-mutant glioma towards glioblastoma upon concomitant inactivation of tp53. Interestingly, although clinical SC-PaNEC samples are characterized by abnormal p53 expression or localization, in the current experimental models, the tp53 status had little effect on the establishment and growth of SC-PaNEC, but may rather be essential for maintaining chromosomal stability. SCLC was only rarely observed in our experimental setup, indicating requirement of additional or alternative oncogenic insults. In conclusion, we used CRISPR/Cas9 to delineate the tumor suppressor properties of Rbl1, generating new insights in the functional redundancy within the retinoblastoma protein family in suppressing neuroendocrine pancreatic cancer and glioma/glioblastoma.

Centromere mechanical maturation during mammalian cell mitosis

During mitosis, tension develops across the centromere as a result of spindle-based forces. Metaphase tension may be critical in preventing mitotic chromosome segregation errors, however, the nature of force transmission at the centromere and the role of centromere mechanics in controlling metaphase tension remains unknown. We combined quantitative, biophysical microscopy with computational analysis to elucidate the mechanics of the centromere in unperturbed, mitotic human cells. We discovered that the mechanical stiffness of the human centromere matures during mitotic progression, which leads to amplified centromere tension specifically at metaphase. Centromere mechanical maturation is disrupted across multiple aneuploid cell lines, leading to a weak metaphase tension signal. Further, increasing deficiencies in centromere mechanical maturation are correlated with rising frequencies of lagging, merotelic chromosomes in anaphase, leading to segregation defects at telophase. Thus, we reveal a centromere maturation process that may be critical to the fidelity of chromosome segregation during mitosis.

During mitosis, tension at the centromere occurs from the spindle but the role of centromere mechanics in controlling metaphase tension is poorly understood. Here, the authors report that mechanical stiffnness of the centromere matures during mitotic progression and is amplified specifically at metaphase.

Development and validation of a TP53-associated immune prognostic model for hepatocellular carcinoma

BACKGROUND

TP53 mutation is the most common mutation in hepatocellular carcinoma (HCC), and it affects the progression and prognosis of HCC. We investigated how TP53 mutation regulates the HCC immunophenotype and thus affects the prognosis of HCC.

METHODS

We investigated TP53 mutation status and RNA expression in different populations and platforms and developed an immune prognostic model (IPM) based on immune-related genes that were differentially expressed between TP53^WT and TP53^MUT HCC samples. Then, the influence of the IPM on the immune microenvironment in HCC was comprehensively analysed.

FINDINGS

TP53 mutation resulted in the downregulation of the immune response in HCC. Thirty-seven of the 312 immune response-related genes were differentially expressed based on TP53 mutation status. An IPM was established and validated based on 865 patients with HCC to differentiate patients with a low or high risk of poor survival. A nomogram was also established for clinical application. Functional enrichment analysis showed that the humoral immune response and immune system diseases pathway represented the major function and pathway, respectively, related to the IPM genes. Moreover, we found that the patients in the high-risk group had higher fractions of T cells follicular helper, T cells regulatory (Tregs) and macrophages M0 and presented higher expression of CTLA-4, PD-1 and TIM-3 than the low-risk group.

INTERPRETATION

TP53 mutation is strongly related to the immune microenvironment in HCC. Our IPM, which is sensitive to TP53 mutation status, may have important implications for identifying subgroups of HCC patients with low or high risk of unfavourable survival. FUND: This work was supported by the International Science and Technology Cooperation Projects (2016YFE0107100), the Capital Special Research Project for Health Development (2014-2-4012), the Beijing Natural Science Foundation (L172055 and 7192158), the National Ten Thousand Talent Program, the Fundamental Research Funds for the Central Universities (3332018032), and the CAMS Innovation Fund for Medical Science (CIFMS) (2017-I2M-4-003 and 2018-I2M-3-001).

Context dependent roles for RB-E2F transcriptional regulation in tumor suppression

RB-E2F transcriptional control plays a key role in regulating the timing of cell cycle progression from G1 to S-phase in response to growth factor stimulation. Despite this role, it is genetically dispensable for cell cycle exit in primary fibroblasts in response to growth arrest signals. Mice engineered to be defective for RB-E2F transcriptional control at cell cycle genes were also found to live a full lifespan with no susceptibility to cancer. Based on this background we sought to probe the vulnerabilities of RB-E2F transcriptional control defects found in Rb1^R461E,K542E mutant mice (Rb1^G) through genetic crosses with other mouse strains. We generated Rb1^G/G mice in combination with Trp53 and Cdkn1a deficiencies, as well as in combination with Kras^G12D. The Rb1^G mutation enhanced Trp53 cancer susceptibility, but had no effect in combination with Cdkn1a deficiency or Kras^G12D. Collectively, this study indicates that compromised RB-E2F transcriptional control is not uniformly cancer enabling, but rather has potent oncogenic effects when combined with specific vulnerabilities.

Checkpoint Kinase 1 Expression Predicts Poor Prognosis in Nigerian Breast Cancer Patients

BACKGROUND

Checkpoint kinase 1 (CHEK1), a DNA damage sensor and cell death pathway stimulator, is regarded as an oncogene in tumours, where its activities are considered essential for tumourigenesis and the survival of cancer cells treated with chemotherapy and radiotherapy. In breast cancer, CHEK1 expression has been associated with an aggressive tumour phenotype, the triple-negative breast cancer subtype, an aberrant response to tamoxifen, and poor prognosis. However, the relevance of CHEK1 expression has, hitherto, not been investigated in an indigenous African population. We therefore aimed to investigate the clinicopathological, biological, and prognostic significance of CHEK1 expression in a cohort of Nigerian breast cancer cases.

MATERIAL AND METHODS

Tissue microarrays of 207 Nigerian breast cancer cases were tested for CHEK1 expression using immunohistochemistry. The clinicopathological, molecular, and prognostic characteristics of CHEK1-positive tumours were determined using the Chi-squared test and Kaplan-Meier and Cox regression analyses in SPSS Version 16.

RESULTS

Nuclear expression of CHEK1 was present in 61% of breast tumours and was associated with tumour size, triple-negative cancer, basal-like phenotype, the epithelial-mesenchymal transition, p53 over-expression, DNA homologous repair pathway dysfunction, and poor prognosis.

CONCLUSIONS

The rate expression of CHEK1 is high in Nigerian breast cancer cases and is associated with an aggressive phenotype and poor prognosis.

Integrating the DNA damage and protein stress responses during cancer development and treatment

During evolution, cells have developed a wide spectrum of stress response modules to ensure homeostasis. The genome and proteome damage response pathways constitute the pillars of this interwoven 'defensive' network. Consequently, the deregulation of these pathways correlates with ageing and various pathophysiological states, including cancer. In the present review, we highlight: (1) the structure of the genome and proteome damage response pathways; (2) their functional crosstalk; and (3) the conditions under which they predispose to cancer. Within this context, we emphasize the role of oncogene-induced DNA damage as a driving force that shapes the cellular landscape for the emergence of the various hallmarks of cancer. We also discuss potential means to exploit key cancer-related alterations of the genome and proteome damage response pathways in order to develop novel efficient therapeutic modalities. © 2018 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Expression of MAGE-A and NY-ESO-1 cancer/testis antigens is enriched in triple-negative invasive breast cancers

Aims

A better understanding of the expression of cancer/testis antigens (CTAs) in breast cancer might enable the identification of new immunotherapy options, especially for triple‐negative (TN) tumours, which lack expression of the conventional therapeutic targets oestrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2. The aim of this study was to quantify the expression of MAGE‐A and NY‐ESO‐1 CTAs in breast cancer, and relate this to known clinicopathological parameters.

Methods and results

We surveyed MAGE‐A and NY‐ESO‐1 expression in an unselected cohort of 367 breast tumours (of which 65 were TN), with accompanying clinical follow‐up data, by using immunohistochemical analysis of tissue microarrays. Relevant to their potential as vaccine targets in breast cancer, MAGE‐A was expressed in 13% of cases, and NY‐ESO‐1 in 3.8%, with the majority of tumours showing fairly homogeneous staining within individual tissue cores (~85% of cases with staining in >75% of tumour cells). Most NY‐ESO‐1‐positive cases also expressed MAGE‐A (P = 2.06 × 10⁻⁹), and both were strongly associated with the TN phenotype (P < 0.0001), with the most proliferative and poorly differentiated cases, in paticular, showing genomic instability. This was characterised by coexpression of c‐Kit and TTK, and overexpression of p53.

Conclusions

MAGE‐A and NY‐ESO‐1 are frequently expressed in TN breast cancer (~47% and 17% of TN cases, respectively), suggesting that targeting them could be feasible in this patient group. Expression is reasonably homogeneous in positive cases, suggesting that immunohistochemical analysis of tissue biopsies would be a reliable companion biomarker.

Retinoblastoma 1 protects T cell maturation from premature apoptosis by inhibiting E2F1

T lymphocytes are key cellular components of an acquired immune system and play essential roles in cell-mediated immunity. T cell development occurs in the thymus where 95% of immature thymocytes are eliminated via apoptosis. It is known that mutation of Zeb1, one of the retinoblastoma 1 (Rb1) target genes, results in a decrease in the number of immature T cells in mice. E2F1, an RB1-interacting protein, has been shown to regulate mature T cell development by interfering with thymocyte apoptosis. However, whether Rb1 regulates thymocyte development in vivo still needs to be further investigated. Here, we use a zebrafish model to investigate the role of Rb1 in T cell development. We show that Rb1-deficient fish exhibit a significant reduction in T cell number during early development that it is attributed to the accelerated apoptosis of immature T cells in a caspase-dependent manner. We further show that E2F1 overexpression could mimic the reduced T lymphocytes phenotype of Rb1 mutants, and E2F1 knockdown could rescue the phenotype in Rb1-deficient mutants. Collectively, our data indicate that the Rb1-E2F1-caspase axis is crucial for protecting immature T cells from apoptosis during early T lymphocyte maturation.

RB1: a prototype tumor suppressor and an enigma

In this review, Dyson summarizes some recent developments in pRB research and focuses on progress toward answers for the three fundamental questions that sit at the heart of the pRB literature: What does pRB do? How does the inactivation of RB change the cell? How can our knowledge of RB function be exploited to provide better treatment for cancer patients?

The retinoblastoma susceptibility gene (RB1) was the first tumor suppressor gene to be molecularly defined. RB1 mutations occur in almost all familial and sporadic forms of retinoblastoma, and this gene is mutated at variable frequencies in a variety of other human cancers. Because of its early discovery, the recessive nature of RB1 mutations, and its frequency of inactivation, RB1 is often described as a prototype for the class of tumor suppressor genes. Its gene product (pRB) regulates transcription and is a negative regulator of cell proliferation. Although these general features are well established, a precise description of pRB's mechanism of action has remained elusive. Indeed, in many regards, pRB remains an enigma. This review summarizes some recent developments in pRB research and focuses on progress toward answers for the three fundamental questions that sit at the heart of the pRB literature: What does pRB do? How does the inactivation of RB change the cell? How can our knowledge of RB function be exploited to provide better treatment for cancer patients?

The Consequences of Chromosome Segregation Errors in Mitosis and Meiosis

Mistakes during cell division frequently generate changes in chromosome content, producing aneuploid or polyploid progeny cells. Polyploid cells may then undergo abnormal division to generate aneuploid cells. Chromosome segregation errors may also involve fragments of whole chromosomes. A major consequence of segregation defects is change in the relative dosage of products from genes located on the missegregated chromosomes. Abnormal expression of transcriptional regulators can also impact genes on the properly segregated chromosomes. The consequences of these perturbations in gene expression depend on the specific chromosomes affected and on the interplay of the aneuploid phenotype with the environment. Most often, these novel chromosome distributions are detrimental to the health and survival of the organism. However, in a changed environment, alterations in gene copy number may generate a more highly adapted phenotype. Chromosome segregation errors also have important implications in human health. They may promote drug resistance in pathogenic microorganisms. In cancer cells, they are a source for genetic and phenotypic variability that may select for populations with increased malignance and resistance to therapy. Lastly, chromosome segregation errors during gamete formation in meiosis are a primary cause of human birth defects and infertility. This review describes the consequences of mitotic and meiotic errors focusing on novel concepts and human health.

TP53 mutation-mediated genomic instability induces the evolution of chemoresistance and recurrence in epithelial ovarian cancer

BACKGROUND

Genomic instability caused by mutation of the checkpoint molecule TP53 may endow cancer cells with the ability to undergo genomic evolution to survive stress and treatment. We attempted to gain insight into the potential contribution of ovarian cancer genomic instability resulted from TP53 mutation to the aberrant expression of multidrug resistance gene MDR1.

METHODS

TP53 mutation status was assessed by performing nucleotide sequencing and immunohistochemistry. Ovarian cancer cell DNA ploidy was determined using Feulgen-stained smears or flow cytometry. DNA copy number was analyzed by performing fluorescence in situ hybridization (FISH).

RESULTS

In addition to performing nucleotide sequencing for 5 cases of ovarian cancer, TP53 mutations were analyzed via immunohistochemical staining for P53. Both intensive P53 immunohistochemical staining and complete absence of signal were associated with the occurrence of TP53 mutations. HE staining and the quantification of DNA content indicated a significantly higher proportion of polyploidy and aneuploidy cells in the TP53 mutant group than in the wild-type group (p < 0.05). Moreover, in 161 epithelial ovarian cancer patients, multivariate logistic analysis identified late FIGO (International Federation of Gynecology and Obstetrics) stage, serous histotype, G3 grade and TP53 mutation as independent risk factors for ovarian cancer recurrence. In relapse patients, the proportion of chemoresistant cases in the TP53 wild-type group was significantly lower than in the mutant group (63.6% vs. 91.8%, p < 0.05). FISH results revealed a higher percentage of cells with >6 MDR1 copies and chromosome 7 amplication in the TP53 mutant group than in the wild-type group [11.7 ± 2.3% vs. 3.0 ± 0.7% and 2.1 ± 0.7% vs. 0.3 ± 0.05%, (p < 0.05), respectively]. And we observed a specific increase of MDR1 and chromosome 7 copy numbers in the TP53 mutant group upon disease regression (p < 0.01).

CONCLUSIONS

TP53 mutation-associated genomic instability may promote chromosome 7 accumulation and MDR1 amplification during ovarian cancer chemoresistance and recurrence. Our findings lay the foundation for the development of promising chemotherapeutic approaches to treat aggressive and recurrent ovarian cancer.

Frequently mutated genes/pathways and genomic instability as prevention targets in liver cancer

The incidence of liver cancer has increased in recent years. Worldwide, liver cancer is common: more than 600000 related deaths are estimated each year. In the USA, about 27170 deaths due to liver cancer are estimated for 2016. Liver cancer is highly resistant to conventional chemotherapy and radiotherapy. For all stages combined, the 5-year survival rate is 15-17%, leaving much to be desired for liver cancer prevention and therapy. Heterogeneity, which can originate from genomic instability, is one reason for poor outcome. About 80-90% of liver cancers are hepatocellular carcinoma (HCC), and recent cancer genome sequencing studies have revealed frequently mutated genes in HCC. In this review, we discuss the cause of the tumor heterogeneity based on the functions of genes that are frequently mutated in HCC. We overview the functions of the genes that are most frequently mutated (e.g. TP53, CTNNB1, AXIN1, ARID1A and WWP1) that portray major pathways leading to HCC and identify the roles of these genes in preventing genomic instability. Notably, the pathway analysis suggested that oxidative stress management may be critical to prevent accumulation of DNA damage and further mutations. We propose that both chromosome instability (CIN) and microsatellite instability (MIN) are integral to the hepatic carcinogenesis process leading to heterogeneity in HCC and that the pathways leading to heterogeneity may be targeted for prognosis, prevention and treatment.

Retinoblastoma tumor suppressor functions shared by stem cell and cancer cell strategies

Carcinogenic transformation of somatic cells resembles nuclear reprogramming toward the generation of pluripotent stem cells. These events share eternal escape from cellular senescence, continuous self-renewal in limited but certain population of cells, and refractoriness to terminal differentiation while maintaining the potential to differentiate into cells of one or multiple lineages. As represented by several oncogenes those appeared to be first keys to pluripotency, carcinogenesis and nuclear reprogramming seem to share a number of core mechanisms. The retinoblastoma tumor suppressor product retinoblastoma (RB) seems to be critically involved in both events in highly complicated manners. However, disentangling such complicated interactions has enabled us to better understand how stem cell strategies are shared by cancer cells. This review covers recent findings on RB functions related to stem cells and stem cell-like behaviors of cancer cells.

Overexpression of the microRNA miR-433 promotes resistance to paclitaxel through the induction of cellular senescence in ovarian cancer cells

Annually, ovarian cancer (OC) affects 240,000 women worldwide and is the most lethal gynecological malignancy. High-grade serous OC (HGSOC) is the most common and aggressive OC subtype, characterized by widespread genome changes and chromosomal instability and is consequently poorly responsive to chemotherapy treatment. The objective of this study was to investigate the role of the microRNA miR-433 in the cellular response of OC cells to paclitaxel treatment. We show that stable miR-433 expression in A2780 OC cells results in the induction of cellular senescence demonstrated by morphological changes, downregulation of phosphorylated retinoblastoma (p-Rb), and an increase in β-galactosidase activity. Furthermore, in silico analysis identified four possible miR-433 target genes associated with cellular senescence: cyclin-dependent kinase 6 (CDK6), MAPK14, E2F3, and CDKN2A. Mechanistically, we demonstrate that downregulation of p-Rb is attributable to a miR-433-dependent downregulation of CDK6, establishing it as a novel miR-433 associated gene. Interestingly, we show that high miR-433 expressing cells release miR-433 into the growth media via exosomes which in turn can induce a senescence bystander effect. Furthermore, in relation to a chemotherapeutic response, quantitative real-time polymerase chain reaction (qRT-PCR) analysis revealed that only PEO1 and PEO4 OC cells with the highest miR-433 expression survive paclitaxel treatment. Our data highlight how the aberrant expression of miR-433 can adversely affect intracellular signaling to mediate chemoresistance in OC cells by driving cellular senescence.

Conditional haploinsufficiency of the retinoblastoma tumor suppressor gene

Recent work demonstrates that retention of a single functional retinoblastoma susceptibility (RB1) allele is insufficient to maintain genome stability. Haploinsufficiency of RB1 accelerates cancer pathogenesis in concert with inactivation of tumor protein p53. Collectively, multiple lines of evidence suggest revision of the ‘2-hit’ model to include conditional haploinsufficiency of RB1.

Suppression of genome instability in pRB-deficient cells by enhancement of chromosome cohesion

Chromosome instability (CIN), a common feature of solid tumors, promotes tumor evolution and increases drug resistance during therapy. We previously demonstrated that loss of the retinoblastoma protein (pRB) tumor suppressor causes changes in centromere structure and generates CIN. However, the mechanism and significance of this change was unclear. Here, we show that defects in cohesion are key to the pRB loss phenotype. pRB loss alters H4K20 methylation, a prerequisite for efficient establishment of cohesion at centromeres. Changes in cohesin regulation are evident during S phase, where they compromise replication and increase DNA damage. Ultimately, such changes compromise mitotic fidelity following pRB loss. Remarkably, increasing cohesion suppressed all of these phenotypes and dramatically reduced CIN in cancer cells lacking functional pRB. These data explain how loss of pRB undermines genomic integrity. Given the frequent functional inactivation of pRB in cancer, conditions that increase cohesion may provide a general strategy to suppress CIN.