Cancer: a CINful evolution

BUB1/KIF14 complex promotes anaplastic thyroid carcinoma progression by inducing chromosome instability

Chromosome instability (CIN) is a common contributor driving the formation and progression of anaplastic thyroid cancer (ATC), but its mechanism remains unclear. The BUB1 mitotic checkpoint serine/threonine kinase (BUB1) is responsible for the alignment of mitotic chromosomes, which has not been thoroughly studied in ATC. Our research demonstrated that BUB1 was remarkably upregulated and closely related to worse progression-free survival. Knockdown of BUB1 attenuated cell viability, invasion, migration and induced cell cycle arrests, whereas overexpression of BUB1 promoted the cell cycle progression of papillary thyroid cancer cells. BUB1 knockdown remarkably repressed tumour growth and tumour formation of nude mice with ATC xenografts and suppressed tumour metastasis in a zebrafish xenograft model. Inhibition of BUB1 by its inhibitor BAY-1816032 also exhibited considerable anti-tumour activity. Further studies showed that enforced expression of BUB1 evoked CIN in ATC cells. BUB1 induced CIN through phosphorylation of KIF14 at serine1292 (Ser1292 ). Overexpression of the KIF14ΔSer1292 mutant was unable to facilitate the aggressiveness of ATC cells when compared with that of the wild type. Collectively, these findings demonstrate that the BUB1/KIF14 complex drives the aggressiveness of ATC by inducing CIN.

Identification of aneuploidy-related gene signature to predict survival in head and neck squamous cell carcinomas

BACKGROUND

To parse the characteristics of aneuploidy related riskscore (ARS) model in head and neck squamous cell carcinomas (HNSC) and their predictive ability on patient prognosis.

METHODS

Molecular subtyping of HNSC specimens was clustered by Copy Number Variation (CNV) data from The Cancer Genome Atlas (TCGA) dataset applying consistent clustering, followed by immune condition evaluation, differentially expressed genes (DEGs) analysis and DEGs function annotation. Weighted gene co-expression network analysis (WGCNA), protein-protein interaction, Univariate Cox regression analysis, least absolute shrinkage and selection operator (LASSO) and stepwise multivariate Cox regression analysis were implemented to construct an ARS model. A nomogram for clinic practice was designed by rms package. Immunotherapy evaluation and drug sensitivity prediction were also carried out.

RESULTS

We stratified HNSC patients into three different molecular subgroups, with the best prognosis in C1 cluster among 3 clusters. C1 cluster displayed greatest immune infiltration status. The most DEGs between C1 and C2 groups, mainly enriched in cell cycle and immune function. We constructed a nine-gene ARS model (ICOS, IL21R, CCR7, SELL, CYTIP, ZAP70, CCR4, S1PR4 and CD79A) that effectively differentiates between high- and low-risk patients. Patients in low ARS group showed a higher sensitivity to immunotherapy. A nomogram built by integrating ARS and clinic-pathological characteristics helped predict clinic survival benefit. Drug sensitivity evaluation found that 4/9 inhibitor drugs (MK-8776, AZD5438, PD-0332991, PHA-665752) acted on the cell cycle.

CONCLUSIONS

We classified 3 molecular subtypes for HNSC patients and established an ARS prognostic model, which offered a prospective direction for prognosis in HNSC.

Insight into the physiological and pathological roles of USP44, a potential tumor target (Review)

Ubiquitin-specific peptidase 44 (USP44) is a member of the ubiquitin-specific proteases (USPs) family and its functions in various biological processes have been gradually elucidated in recent years. USP44 targets multiple downstream factors and regulates multiple mechanisms through its deubiquitination activity. Ubiquitination is, in essence, a process in which a single ubiquitin molecule or a multiubiquitin chain binds to a substrate protein to form an isopeptide bond. Deubiquitination is the catalyzing of the isopeptide bonds between ubiquitin and substrate proteins through deubiquitylating enzymes. These two processes serve an important role in the regulation of the expression, conformation, localization and function of substrate proteins by regulating their binding to ubiquitin. Based on existing research, this paper summarized the current state of knowledge about USP44. The physiological roles of USP44 in various cellular events and its pathophysiological roles in different cancer types are evaluated and the therapeutic potential of USP44 for cancer treatment is evaluated.

Implications of Polyploidy and Ploidy Alterations in Hepatocytes in Liver Injuries and Cancers

Polyploidy, a condition in which more than two sets of chromosomes are present in a cell, is a characteristic feature of hepatocytes. A significant number of hepatocytes physiologically undergo polyploidization at a young age. Polyploidization of hepatocytes is enhanced with age and in a diseased liver. It is worth noting that polyploid hepatocytes can proliferate, in marked contrast to other types of polyploid cells, such as megakaryocytes and cardiac myocytes. Polyploid hepatocytes divide to maintain normal liver homeostasis and play a role in the regeneration of the damaged liver. Furthermore, polyploid hepatocytes have been shown to dynamically reduce ploidy during liver regeneration. Although it is still unclear why hepatocytes undergo polyploidization, accumulating evidence has revealed that alterations in the ploidy in hepatocytes are involved in the pathophysiology of liver cirrhosis and carcinogenesis. This review discusses the significance of hepatocyte ploidy in physiological liver function, liver injury, and liver cancer.

The Controversial Role of Polyploidy in Hepatocellular Carcinoma

Polyploidy, a physiological phenomenon in which cells contain more than two sets of homologous chromosomes, commonly exists in plants, fish, and amphibians but is rare in mammals. In humans, polyploid cells are detected commonly in specific organs or tissues including the heart, marrow, and liver. As the largest solid organ in the body, the liver is responsible for a myriad of functions, most of which are closely related to polyploid hepatocytes. It has been confirmed that polyploid hepatocytes are related to liver regeneration, homeostasis, terminal differentiation, and aging. Polyploid hepatocytes accumulate during the aging process as well as in chronically injured livers. The relationship between polyploid hepatocytes and hepatocellular carcinoma, the endpoint of most chronic liver diseases, is not yet fully understood. Recently, accumulated evidence has revealed that polyploid involves in the process of tumorigenesis and development. The study of the correlation and relationship between polyploidy hepatocytes and the development of hepatocellular carcinoma can potentially promote the prevention, early diagnosis, and treatment of hepatocellular carcinoma. In this review, we conclude the potential mechanisms of polyploid hepatocytes formation, focusing on the specific biological significance of polyploid hepatocytes. In addition, we examine recent discoveries that have begun to clarify the relevance between polyploid hepatocytes and hepatocellular carcinoma and discuss recent excellent findings that reveal the role of polyploid hepatocytes as resisters of hepatocellular carcinoma or as promoters of hepatocarcinogenesis.

Microtubule Targeting Agents in Disease: Classic Drugs, Novel Roles

Microtubule-targeting agents (MTAs) represent one of the most successful first-line therapies prescribed for cancer treatment. They interfere with microtubule (MT) dynamics by either stabilizing or destabilizing MTs, and in culture, they are believed to kill cells via apoptosis after eliciting mitotic arrest, among other mechanisms. This classical view of MTA therapies persisted for many years. However, the limited success of drugs specifically targeting mitotic proteins, and the slow growing rate of most human tumors forces a reevaluation of the mechanism of action of MTAs. Studies from the last decade suggest that the killing efficiency of MTAs arises from a combination of interphase and mitotic effects. Moreover, MTs have also been implicated in other therapeutically relevant activities, such as decreasing angiogenesis, blocking cell migration, reducing metastasis, and activating innate immunity to promote proinflammatory responses. Two key problems associated with MTA therapy are acquired drug resistance and systemic toxicity. Accordingly, novel and effective MTAs are being designed with an eye toward reducing toxicity without compromising efficacy or promoting resistance. Here, we will review the mechanism of action of MTAs, the signaling pathways they affect, their impact on cancer and other illnesses, and the promising new therapeutic applications of these classic drugs.

Bridging Tumorigenesis and Therapy Resistance With a Non-Darwinian and Non-Lamarckian Mechanism of Adaptive Evolution

Although neo-Darwinian (and less often Lamarckian) dynamics are regularly invoked to interpret cancer's multifarious molecular profiles, they shine little light on how tumorigenesis unfolds and often fail to fully capture the frequency and breadth of resistance mechanisms. This uncertainty frames one of the most problematic gaps between science and practice in modern times. Here, we offer a theory of adaptive cancer evolution, which builds on a molecular mechanism that lies outside neo-Darwinian and Lamarckian schemes. This mechanism coherently integrates non-genetic and genetic changes, ecological and evolutionary time scales, and shifts the spotlight away from positive selection towards purifying selection, genetic drift, and the creative-disruptive power of environmental change. The surprisingly simple use-it or lose-it rationale of the proposed theory can help predict molecular dynamics during tumorigenesis. It also provides simple rules of thumb that should help improve therapeutic approaches in cancer.

Molecular Genetics in Neuroblastoma Prognosis

In recent years, much research has been carried out to identify the biological and genetic characteristics of the neuroblastoma (NB) tumor in order to precisely define the prognostic subgroups for improving treatment stratification. This review will describe the major genetic features and the recent scientific advances, focusing on their impact on diagnosis, prognosis, and therapeutic solutions in NB clinical management.

Chromosomal Instability in Acute Myeloid Leukemia

Chromosomal instability (CIN), the increasing rate in which cells acquire new chromosomal alterations, is one of the hallmarks of cancer. Many studies highlighted CIN as an important mechanism in the origin, progression, and relapse of acute myeloid leukemia (AML). The ambivalent feature of CIN as a cancer-promoting or cancer-suppressing mechanism might explain the prognostic variability. The latter, however, is described in very few studies. This review highlights the important CIN mechanisms in AML, showing that CIN signatures can occur largely in all the three major AML types (de novo AML, secondary-AML, and therapy-related-AML). CIN features in AML could also be age-related and reflect the heterogeneity of the disease. Although most of these abnormalities show an adverse prognostic value, they also offer a strong new perspective on personalized therapy approaches, which goes beyond assessing CIN in vitro in patient tumor samples to predict prognosis. Current and emerging AML therapies are exploring CIN to improve AML treatment, which includes blocking CIN or increasing CIN beyond the limit threshold to induce cell death. We argue that the characterization of CIN features, not included yet in the routine diagnostic of AML patients, might provide a better stratification of patients and be extended to a more personalized therapeutic approach.

Genetic variation in aneuploidy prevalence and tolerance across Saccharomyces cerevisiae lineages

Individuals carrying an aberrant number of chromosomes can vary widely in their expression of aneuploidy phenotypes. A major unanswered question is the degree to which an individual's genetic makeup influences its tolerance of karyotypic imbalance. Here we investigated within-species variation in aneuploidy prevalence and tolerance, using Saccharomyces cerevisiae as a model for eukaryotic biology. We analyzed genotypic and phenotypic variation recently published for over 1,000 S. cerevisiae strains spanning dozens of genetically defined clades and ecological associations. Our results show that the prevalence of chromosome gain and loss varies by clade and can be better explained by differences in genetic background than ecology. The relationships between lineages with high aneuploidy frequencies suggest that increased aneuploidy prevalence emerged multiple times in S. cerevisiae evolution. Separate from aneuploidy prevalence, analyzing growth phenotypes revealed that some genetic backgrounds-such as the European Wine lineage-show fitness costs in aneuploids compared to euploids, whereas other clades with high aneuploidy frequencies show little evidence of major deleterious effects. Our analysis confirms that chromosome gain can produce phenotypic benefits, which could influence evolutionary trajectories. These results have important implications for understanding genetic variation in aneuploidy prevalence in health, disease, and evolution.

High Chromosomal Stability and Immortalized Totipotency Characterize Long-Term Tissue Cultures of Chinese Ginseng (Panax Ginseng)

Chinese ginseng (Panax ginseng C. A. Meyer) is a highly cherished traditional Chinese medicine, with several confirmed medical effects and many more asserted health-boosting functions. Somatic chromosomal instability (CIN) is a hallmark of many types of human cancers and also related to other pathogenic conditions such as miscarriages and intellectual disabilities, hence, the study of this phenomenon is of wide scientific and translational medical significance. CIN also ubiquitously occurs in cultured plant cells, and is implicated as a major cause of the rapid decline/loss of totipotency with culture duration, which represents a major hindrance to the application of transgenic technologies in crop improvement. Here, we report two salient features of long-term cultured callus cells of ginseng, i.e., high chromosomal stability and virtually immortalized totipotency. Specifically, we document that our callus of ginseng, which has been subcultured for 12 consecutive years, remained highly stable at the chromosomal level and showed little decline in totipotency. We show that these remarkable features of cultured ginseng cells are likely relevant to the robust homeostasis of the transcriptional expression of specific genes (i.e., genes related to tissue totipotency and chromosomal stability) implicated in the manifestation of these two complex phenotypes. To our knowledge, these two properties of ginseng have not been observed in any animals (with respect to somatic chromosomal stability) and other plants. We posit that further exploration of the molecular mechanisms underlying these unique properties of ginseng, especially somatic chromosomal stability in protracted culture duration, may provide novel clues to the mechanistic understanding of the occurrence of CIN in human disease.

Proliferative polyploid cells give rise to tumors via ploidy reduction

Polyploidy is a hallmark of cancer, and closely related to chromosomal instability involved in cancer progression. Importantly, polyploid cells also exist in some normal tissues. Polyploid hepatocytes proliferate and dynamically reduce their ploidy during liver regeneration. This raises the question whether proliferating polyploids are prone to cancer via chromosome missegregation during mitosis and/or ploidy reduction. Conversely polyploids could be resistant to tumor development due to their redundant genomes. Therefore, the tumor-initiation risk of physiologic polyploidy and ploidy reduction is still unclear. Using in vivo lineage tracing we here show that polyploid hepatocytes readily form liver tumors via frequent ploidy reduction. Polyploid hepatocytes give rise to regenerative nodules with chromosome aberrations, which are enhanced by ploidy reduction. Although polyploidy should theoretically prevent tumor suppressor loss, the high frequency of ploidy reduction negates this protection. Importantly, polyploid hepatocytes that undergo multiple rounds of cell division become predominantly mononucleated and are resistant to ploidy reduction. Our results suggest that ploidy reduction is an early step in the initiation of carcinogenesis from polyploid hepatocytes.

P53 induces senescence in the unstable progeny of aneuploid cells

Aneuploidy is the condition of having an imbalanced karyotype, which is associated with tumor initiation, evolution, and acquisition of drug-resistant features, possibly by generating heterogeneous populations of cells with distinct genotypes and phenotypes. Multicellular eukaryotes have therefore evolved a range of extrinsic and cell-autonomous mechanisms for restraining proliferation of aneuploid cells, including activation of the tumor suppressor protein p53. However, accumulating evidence indicates that a subset of aneuploid cells can escape p53-mediated growth restriction and continue proliferating in vitro. Here we show that such aneuploid cell lines display a robust modal karyotype and low frequency of chromosomal aberrations despite ongoing chromosome instability. Indeed, while these aneuploid cells are able to survive for extended periods in vitro, their chromosomally unstable progeny remain subject to p53-induced senescence and growth restriction, leading to subsequent elimination from the aneuploid pool. This mechanism helps maintain low levels of heterogeneity in aneuploid populations and may prevent detrimental evolutionary processes such as cancer progression and development of drug resistance.

Mus81-Eme1-dependent aberrant processing of DNA replication intermediates in mitosis impairs genome integrity

Chromosome instability (CIN) underpins cancer evolution and is associated with drug resistance and poor prognosis. Understanding the mechanistic basis of CIN is thus a priority. The structure-specific endonuclease Mus81-Eme1 is known to prevent CIN. Intriguingly, however, here we show that the aberrant processing of late replication intermediates by Mus81-Eme1 is a source of CIN. Upon depletion of checkpoint kinase 1 (Chk1), Mus81-Eme1 cleaves under-replicated DNA engaged in mitotic DNA synthesis, leading to chromosome segregation defects. Supplementing cells with nucleosides allows the completion of mitotic DNA synthesis, restraining Mus81-Eme1-dependent DNA damage in mitosis and the ensuing CIN. We found no correlation between CIN arising from nucleotide shortage in mitosis and cell death, which were selectively linked to DNA damage load in mitosis and S phase, respectively. Our findings imply the possibility of optimizing Chk1-directed therapies by inducing cell death while curtailing CIN, a common side effect of chemotherapy.

Morphology-Predicted Large-Scale Transition Number in Circulating Tumor Cells Identifies a Chromosomal Instability Biomarker Associated with Poor Outcome in Castration-Resistant Prostate Cancer

Chromosomal instability (CIN) increases a tumor cell's ability to acquire chromosomal alterations, a mechanism by which tumor cells evolve, adapt, and resist therapeutics. We sought to develop a biomarker of CIN in circulating tumor cells (CTC) that are more likely to reflect the genetic diversity of patient's disease than a single-site biopsy and be assessed rapidly so as to inform treatment management decisions in real time. Large-scale transitions (LST) are genomic alterations defined as chromosomal breakages that generate chromosomal gains or losses of greater than or equal to10 Mb. Here we studied the relationship between the number of LST in an individual CTC determined by direct sequencing and morphologic features of the cells. This relationship was then used to develop a computer vision algorithm that utilizes CTC image features to predict the presence of a high (9 or more) versus low (8 or fewer) LST number in a single cell. As LSTs are a primary functional component of homologous recombination deficient cellular phenotypes, the image-based algorithm was studied prospectively on 10,240 CTCs in 367 blood samples obtained from 294 patients with progressing metastatic castration-resistant prostate cancer taken prior to starting a standard-of-care approved therapy. The resultant computer vision-based biomarker of CIN in CTCs in a pretreatment sample strongly associated with poor overall survival times in patients treated with androgen receptor signaling inhibitors and taxanes. SIGNIFICANCE: A rapidly assessable biomarker of chromosomal instability in CTC is associated with poor outcomes when detected in men with progressing mCRPC.

Asymmetric clustering of centrosomes defines the early evolution of tetraploid cells

Tetraploidy has long been of interest to both cell and cancer biologists, partly because of its documented role in tumorigenesis. A common model proposes that the extra centrosomes that are typically acquired during tetraploidization are responsible for driving tumorigenesis. However, tetraploid cells evolved in culture have been shown to lack extra centrosomes. This observation raises questions about how tetraploid cells evolve and more specifically about the mechanisms(s) underlying centrosome loss. Here, using a combination of fixed cell analysis, live cell imaging, and mathematical modeling, we show that populations of newly formed tetraploid cells rapidly evolve in vitro to retain a near-tetraploid chromosome number while losing the extra centrosomes gained at the time of tetraploidization. This appears to happen through a process of natural selection in which tetraploid cells that inherit a single centrosome during a bipolar division with asymmetric centrosome clustering are favored for long-term survival.

Comparative Molecular Life History of Spontaneous Canine and Human Gliomas

Sporadic gliomas in companion dogs provide a window on the interaction between tumorigenic mechanisms and host environment. We compared the molecular profiles of canine gliomas with those of human pediatric and adult gliomas to characterize evolutionarily conserved mammalian mutational processes in gliomagenesis. Employing whole-genome, exome, transcriptome, and methylation sequencing of 83 canine gliomas, we found alterations shared between canine and human gliomas such as the receptor tyrosine kinases, TP53 and cell-cycle pathways, and IDH1 R132. Canine gliomas showed high similarity with human pediatric gliomas per robust aneuploidy, mutational rates, relative timing of mutations, and DNA-methylation patterns. Our cross-species comparative genomic analysis provides unique insights into glioma etiology and the chronology of glioma-causing somatic alterations.

The genetic basis of aneuploidy tolerance in wild yeast

Aneuploidy is highly detrimental during development yet common in cancers and pathogenic fungi – what gives rise to differences in aneuploidy tolerance remains unclear. We previously showed that wild isolates of Saccharomyces cerevisiae tolerate chromosome amplification while laboratory strains used as a model for aneuploid syndromes do not. Here, we mapped the genetic basis to Ssd1, an RNA-binding translational regulator that is functional in wild aneuploids but defective in laboratory strain W303. Loss of SSD1 recapitulates myriad aneuploidy signatures previously taken as eukaryotic responses. We show that aneuploidy tolerance is enabled via a role for Ssd1 in mitochondrial physiology, including binding and regulating nuclear-encoded mitochondrial mRNAs, coupled with a role in mitigating proteostasis stress. Recapitulating ssd1Δ defects with combinatorial drug treatment selectively blocked proliferation of wild-type aneuploids compared to euploids. Our work adds to elegant studies in the sensitized laboratory strain to present a mechanistic understanding of eukaryotic aneuploidy tolerance.

Kinetochore-associated Stu2 promotes chromosome biorientation in vivo

Accurate segregation of chromosomes to daughter cells is a critical aspect of cell division. It requires the kinetochores on duplicated chromosomes to biorient, attaching to microtubules from opposite poles of the cell. Bioriented attachments come under tension, while incorrect attachments lack tension and must be released to allow proper attachments to form. A well-studied error correction pathway is mediated by the Aurora B kinase, which destabilizes low tension-bearing attachments. We recently discovered that in vitro, kinetochores display an additional intrinsic tension-sensing pathway that utilizes Stu2. The contribution of kinetochore-associated Stu2 to error correction in cells, however, was unknown. Here, we identify a Stu2 mutant that abolishes its kinetochore function and show that it causes biorientation defects in vivo. We also show that this Stu2-mediated pathway functions together with the Aurora B-mediated pathway. Altogether, our work indicates that cells employ multiple pathways to ensure biorientation and the accuracy of chromosome segregation.

The precise regulation of cell division is critical to processes such as self-renewal, proliferation and development. A key event in the cell cycle is the partitioning of every pair of duplicated chromosomes to daughter cells. Defects in chromosome partitioning lead to aneuploidy, a condition that is a common hallmark of cancer cells and the cause of some birth defects. Chromosomes segregate using their kinetochores, the specialized protein structures that are assembled on centromeric DNA sequences and attach to spindle microtubules. Here, we report that a protein that associates with kinetochores called Stu2 ensures that each kinetochore attaches to the proper microtubules. We identified a Stu2 mutant that does not associate with kinetochores and found that it generates aneuploidy. Together, our work identifies a previously unknown mechanism where cells ensure that chromosomes are accurately inherited during cell division.

Analysis of basal chromosome instability in patients with chronic lymphocytic leukaemia

Genomic instability is a hallmark of cancer, contributing to tumour development and transformation, being chromosome instability (CIN) the most common form in human cancer. Chronic lymphocytic leukaemia (CLL) is the most frequent adult leukaemia in the Western world. In this study, we have evaluated basal CIN in untreated patients with CLL by measuring chromosome aberrations (CAs) and micronucleus (MN) frequency and their association with different prognostic factors. Seventy-two patients and 21 normal controls were analysed. Cytogenetic and fluorescence in situ hybridisation (FISH) studies were performed. IGHV (immunoglobulin heavy chain variable region) mutational status was evaluated by reverse transcription polymerase chain reaction and sequencing. An increased number of CA in patients compared with controls (P = 0.0001) was observed. Cases with abnormal karyotypes showed increased CA rate than those with normal karyotypes (P = 0.0026), with a particularly highest frequency in cases with complex karyotypes. Among FISH risk groups, a significant low frequency of CA was found in patients with no FISH alterations compared to those with del13q14 and ≥2 FISH alterations (P = 0.0074). When mean CA value (6.7%) was considered, significant differences in the distribution of low and high CA frequency between cases with normal and abnormal karyotypes (P = 0.002) were observed. By MN analysis, higher frequency in patients compared to controls (P = 0.0001) was also found, as well as between cases with ≥2 FISH abnormalities and those with no FISH alterations (P = 0.026). Similarly, significant differences were observed when patients were divided according to mean MN frequency (2.2%; P ≤ 0.04). Interestingly, patients with high MN frequency had shorter time to first treatment than those with low frequency (P = 0.024). Cases with mutated and unmutated IGHV status showed increased CA and MN frequencies compared to controls (P ≤ 0.0007), but no differences between both groups were found. Our results support the strong interaction between CIN and genomic complexity as well as their influence on poor outcome in this pathology.

Chromosomal Instability in Tumor Initiation and Development

Chromosomal instability (CIN) is one of the major forms of genomic instability in various human cancers and is recognized as a common hallmark of tumorigenesis and heterogeneity. However, some malignant tumors show a paucity of chromosomal alterations, suggesting that tumor progression and evolution can occur in the absence of CIN. It is unclear whether CIN is stable between precursor lesions, primary tumor, and metastases or if it evolves during these steps. In this review, we describe the influence of CIN on the various steps in tumor initiation and development. Given the recognized significant effects of CIN in cancer, CIN-targeted therapeutics could have a major impact on improving clinical outcomes.

Fusion-mediated chromosomal instability promotes aneuploidy patterns that resemble human tumors

Oncogenesis is considered to result from chromosomal instability, in addition to oncogene and tumor-suppressor alterations. Intermediate to aneuploidy and chromosomal instability, genome doubling is a frequent event in tumor development but the mechanisms driving tetraploidization and its impact remain unexplored. Cell fusion, one of the pathways to tetraploidy, is a physiological process involved in mesenchymal cell differentiation. Besides simple genome doubling, cell fusion results in the merging of two different genomes that can be destabilized upon proliferation. By testing whether cell fusion is involved in mesenchymal oncogenesis, we provide evidence that it induces genomic instability and mediates tumor initiation. After a latency period, the tumor emerges with the cells most suited for its development. Furthermore, hybrid tumor genomes were stabilized after this selection process and were very close to those of human pleomorphic mesenchymal tumors. Thus genome restructuring triggered by cell fusion may account for the chromosomal instability involved in oncogenesis.

Resolving genetic heterogeneity in cancer

To a large extent, cancer conforms to evolutionary rules defined by the rates at which clones mutate, adapt and grow. Next-generation sequencing has provided a snapshot of the genetic landscape of most cancer types, and cancer genomics approaches are driving new insights into cancer evolutionary patterns in time and space. In contrast to species evolution, cancer is a particular case owing to the vast size of tumour cell populations, chromosomal instability and its potential for phenotypic plasticity. Nevertheless, an evolutionary framework is a powerful aid to understand cancer progression and therapy failure. Indeed, such a framework could be applied to predict individual tumour behaviour and support treatment strategies.

Chromosome instability in neuroblastoma

Neuroblastoma is a neural crest-derived tumor that accounts for 7-10% of all malignancies in children and ~15% of all childhood cancer-associated mortalities. Approximately 50% of patients are characterized as high-risk (HR) and have an overall survival of <40% at 5 years from diagnosis. HR patients with unfavorable prognosis exhibit several structural copy number variations (CNVs), whereas localized tumors belonging to patients in the low- and intermediate-risk classes, have favorable outcomes and display several numerical CNVs. Taken together these results are indicative of chromosome instability (CIN) in neuroblastoma tumor cells. The present review discusses multiple aspects of CIN including methods of measuring CIN, CIN targeting as a therapeutic strategy in cancer and the effects of CIN in neuroblastoma development and aggressiveness with particular emphasis on the CIN gene signature associated with HR neuroblastoma patients.

Environmental stresses induce karyotypic instability in colorectal cancer cells

Understanding how cells acquire genetic mutations is a fundamental biological question with implications for many different areas of biomedical research, ranging from tumor evolution to drug resistance. While karyotypic heterogeneity is a hallmark of cancer cells, few mutations causing chromosome instability have been identified in cancer genomes, suggesting a nongenetic origin of this phenomenon. We found that in vitro exposure of karyotypically stable human colorectal cancer cell lines to environmental stress conditions triggered a wide variety of chromosomal changes and karyotypic heterogeneity. At the molecular level, hyperthermia induced polyploidization by perturbing centrosome function, preventing chromosome segregation, and attenuating the spindle assembly checkpoint. The combination of these effects resulted in mitotic exit without chromosome segregation. Finally, heat-induced tetraploid cells were on the average more resistant to chemotherapeutic agents. Our studies suggest that environmental perturbations promote karyotypic heterogeneity and could contribute to the emergence of drug resistance.

Genomic chaos in peripheral blood lymphocytes of Hodgkin's lymphoma patients one year after ABVD chemotherapy/radiotherapy

Hodgkin's lymphoma (HL) is a lymphoid malignancy representing 5% of all cancers in children, 16% in adolescents, and 30-40% of all malignant lymphomas and has a survival rate of ~95% at 10 years. One of the most common treatment schemes uses a cocktail of genotoxic agents including adriamycin, bleomycin, vinblastine, and dacarbazine (ABVD) with or without radiotherapy. We investigated the occurrence of chromosomal damage in peripheral blood lymphocytes from five patients diagnosed with HL who provided samples before (BT), during chemotherapy (DT) and ~1 year after ABVD chemotherapy/radiotherapy (AT). Five healthy subjects served as controls. Chromosomal abnormalities were evaluated by multicolor fluorescence in situ hybridization. The average frequencies of structural chromosomal aberrations in HL samples were 0.11, 0.22, and 0.96 per cell in BT, DT, and AT samples, respectively. These frequencies were significantly different (P < 0.0001) with respect to control subjects (0.02 per cell). Interestingly, the highest frequency of structural damage, including genomic chaos and nonclonal abnormalities, was observed in the AT samples indicating that new aberrations were continuously produced. Rejoined structural chromosomal aberrations were the most common type of aberrations, although aneuploidies were also significantly increased. Finally, we found several chromosomal abnormalities linked to cancer secondary to treatment in all five HL patients. Our results show that ABVD chemotherapy plus radiotherapy is inducing genomic chaos in vivo; moreover, the persistence of genomic instability in the hematopoietic stem cells from HL patients may play a role in the occurrence of secondary cancer that is observed in 5-20% of HL patients. Environ. Mol. Mutagen. 59:755-768, 2018. © 2018 Wiley Periodicals, Inc.

Contradictory mRNA and protein misexpression of EEF1A1 in ductal breast carcinoma due to cell cycle regulation and cellular stress

Encoded by EEF1A1, the eukaryotic translation elongation factor eEF1α1 strongly promotes the heat shock response, which protects cancer cells from proteotoxic stress, following for instance oxidative stress, hypoxia or aneuploidy. Unexpectedly, therefore, we find that EEF1A1 mRNA levels are reduced in virtually all breast cancers, in particular in ductal carcinomas. Univariate and multivariate analyses indicate that EEF1A1 mRNA underexpression independently predicts poor patient prognosis for estrogen receptor-positive (ER+) cancers. EEF1A1 mRNA levels are lowest in the most invasive, lymph node-positive, advanced stage and postmenopausal tumors. In sharp contrast, immunohistochemistry on 100 ductal breast carcinomas revealed that at the protein level eEF1α1 is ubiquitously overexpressed, especially in ER+ , progesterone receptor-positive and lymph node-negative tumors. Explaining this paradox, we find that EEF1A1 mRNA levels in breast carcinomas are low due to EEF1A1 allelic copy number loss, found in 27% of tumors, and cell cycle-specific expression, because mRNA levels are high in G1 and low in proliferating cells. This also links estrogen-induced cell proliferation to clinical observations. In contrast, high eEF1α1 protein levels protect tumor cells from stress-induced cell death. These observations suggest that, by obviating EEF1A1 transcription, cancer cells can rapidly induce the heat shock response following proteotoxic stress, and survive.