High telomerase activity correlates with the stabilities of genome and DNA ploidy in renal cell carcinoma

A non-diploid DNA status is linked to poor prognosis in renal cell cancer

Purpose

DNA ploidy measurement has earlier been suggested as a potentially powerful prognostic tool in many cancer types, but the role in renal tumors is still unclear.

Methods

To clarify its prognostic impact, we analyzed the DNA content of 1320 kidney tumors, including clear cell, papillary and chromophobe renal cell carcinoma (RCC) as well as renal oncocytoma and compared these data with clinico-pathological parameters and patient prognosis.

Results

A non-diploid DNA content was seen in 37% of 1276 analyzable renal tumors with a striking predominance in chromophobe carcinoma (74.3% of 70 cases). In clear cell carcinoma, a non-diploid DNA content was significantly linked to high-grade (ISUP, Fuhrman, Thoenes; p < 0.0001 each), advanced tumor stage (p = 0.0011), distant metastasis (p < 0.0001), shortened overall survival (p = 0.0010), and earlier recurrence (p < 0.0001). In papillary carcinoma, an aberrant DNA content was significantly linked to high Fuhrman grade (p = 0.0063), distant metastasis (p = 0.0138), shortened overall survival (p = 0.0010), and earlier recurrence (p = 0.0003).

Conclusion

In summary, the results of our study identify a non-diploid DNA content as a predictor of an unfavorable prognosis in clear cell and papillary carcinoma.

Electronic supplementary material

The online version of this article (10.1007/s00345-020-03226-8) contains supplementary material, which is available to authorized users.

Chromosomal disruption and rearrangements during murine sarcoma development converge to stable karyotypic formation kept by telomerase overexpression

BACKGROUND

Tumor initiation presents a complex and unstable genomic landscape; one of the earliest hallmark events of cancer, and its progression is probably based on selection mechanisms under specific environments that lead to functional tumor cell speciation. We hypothesized that viable tumor phenotypes possess common and highly stable karyotypes and their proliferation is facilitated by an attuned high telomerase activity. Very few investigations have focused on the evolution of common chromosomal rearrangements associated to molecular events that result in functional phenotypes during tumor development.

RESULTS

We have used cytogenetic, flow cytometry and cell culture tools to investigate chromosomal rearrangements and clonality during cancer development using the murine sarcoma TG180 model, and also molecular biology techniques to establish a correlation between chromosome instability and telomerase activity, since telomeres are highly affected during cancer evolution. Cytogenetic analysis showed a near-tetraploid karyotype originated by endoreduplication. Chromosomal rearrangements were random events in response to in vitro conditions, but a stable karyotypic equilibrium was achieved during tumor progression in different in vivo conditions, suggesting that a specific microenvironment may stabilize the chromosomal number and architecture. Specific chromosome aberrations (marker chromosomes) and activated regions (rDNAs) were ubiquitous in the karyotype, suggesting that the conservation of these patterns may be advantageous for tumor progression. High telomerase expression was also correlated with the chromosomal rearrangements stabilization.

CONCLUSIONS

Our data reinforce the notion that the sarcoma cell evolution converges from a highly unstable karyotype to relatively stable and functional chromosome rearrangements, which are further enabled by telomerase overexpression.

Chordoma: the entity

Chordomas are malignant tumors of the axial skeleton, characterized by their locally invasive and slow but aggressive growth. These neoplasms are presumed to be derived from notochordal remnants with a molecular alteration preceding their malignant transformation. As these tumors are most frequently observed on the skull base and sacrum, patients suffering from a chordoma present with debilitating neurological disease, and have an overall 5-year survival rate of 65%. Surgical resection with adjuvant radiotherapy is the first-choice treatment modality in these patients, since chordomas are resistant to conventional chemotherapy. Even so, management of chordomas can be challenging, as chordoma patients often present with recurrent disease. Recent advances in the understanding of the molecular events that contribute to the development of chordomas are promising; the most novel finding being the identification of brachyury in the disease process. Here we present an overview of the current paradigms and summarize relevant research findings.

Laser scanning cytometry: principles and applications-an update

Laser scanning cytometer (LSC) is the microscope-based cytofluorometer that offers a plethora of unique analytical capabilities, not provided by flow cytometry (FCM). This review describes attributes of LSC and covers its numerous applications derived from plentitude of the parameters that can be measured. Among many LSC applications the following are emphasized: (a) assessment of chromatin condensation to identify mitotic, apoptotic cells, or senescent cells; (b) detection of nuclear or mitochondrial translocation of critical factors such as NF-κB, p53, or Bax; (c) semi-automatic scoring of micronuclei in mutagenicity assays; (d) analysis of fluorescence in situ hybridization (FISH) and use of the FISH analysis attribute to measure other punctuate fluorescence patterns such as γH2AX foci or receptor clustering; (e) enumeration and morphometry of nucleoli and other cell organelles; (f) analysis of progeny of individual cells in clonogenicity assay; (g) cell immunophenotyping; (h) imaging, visual examination, or sequential analysis using different probes of the same cells upon their relocation; (i) in situ enzyme kinetics, drug uptake, and other time-resolved processes; (j) analysis of tissue section architecture using fluorescent and chromogenic probes; (k) application for hypocellular samples (needle aspirate, spinal fluid, etc.); and (l) other clinical applications. Advantages and limitations of LSC are discussed and compared with FCM.

Genome-wide profiling of chromosomal alterations in renal cell carcinoma using high-density single nucleotide polymorphism arrays

The identification of genetic aberrations may help understand the mechanisms of tumorigenesis and has important implications in diagnosis, prognosis and treatment. We applied Illumina's 317K high-density single nucleotide polymorphism (SNP) arrays to profile chromosomal aberrations in clear cell renal cell carcinoma (ccRCC) from 80 patients and analyzed the association of LOH/amplification events with clinicopathological characteristics and telomere length. The most common loss of heterozygosity (LOH) were 3p (69 cases) including 38 whole 3p arm losses, 30 large fragment LOH (spanning 3p21-36), and 1 interstitial LOH (spanning 3p12-14, 3p21-22, 3p24.1-24.2 and 3p24.3), followed by chromosome losses at 8p12-pter, 6q23.3-27, 14q24.1-qter, 9q32-qter, 10q22.3-qter, 9p13.3-pter, 4q28.3-qter and 13q12.1-21.1. We also found several smallest overlapping regions of LOH that contained tumor suppressor genes. One smallest LOH in 8p12 had a size of 0.29 Mb and only contained one gene (NRG1). The most frequent chromosome gains were at 5q (32 cases), including 10 whole 5q amplification, 21 large amplifications encompassing 5q32-ter and 1 focal amplification in 5q35.3 (0.42 Mb). The other common chromosome gains were 1q25.1-qter, 7q21.13-qter, 8q24.12-qter and whole 7p arm. Significant associations of LOH at 9p, 9q, 14q and 18q were observed with higher nuclear grade. Significant associations with tumor stage were observed for LOH at 14q, 18p and 21q. Finally, we found that tumors with LOH at 2q, 6p, 6q, 9p, 9q and 17p had significantly shorter telomere length than those without LOH. This is the first study to use Illumina's SNP-CGH array that provides a close estimate of the size and frequency of chromosome LOH and amplifications of ccRCC. The identified regions and genes may become diagnostic and prognostic biomarkers as well as potential targets of therapy.

FISH glossary: an overview of the fluorescence in situ hybridization technique

The introduction of FISH (fluorescence in situ hybridization) marked the beginning of a new era for the study of chromosome structure and function. As a combined molecular and cytological approach, the major advantage of this visually appealing technique resides in its unique ability to provide an intermediate degree of resolution between DNA analysis and chromosomal investigations while retaining information at the single-cell level. Used to support large-scale mapping and sequencing efforts related to the human genome project, FISH accuracy and versatility were subsequently capitalized on in biological and medical research, providing a wealth of diverse applications and FISH-based diagnostic assays. The diversification of the original FISH protocol into the impressive number of procedures available these days has been promoted throughout the years by a number of interconnected factors: the improvement in sensitivity, specificity and resolution, together with the advances in the fields of fluorescence microscopy and digital imaging, and the growing availability of genomic and bioinformatic resources. By assembling in a glossary format many of the "acronymed" FISH applications published so far, this review intends to celebrate the ability of FISH to re-invent itself and thus remain at the forefront of biomedical research.

Laser scanning cytometry: principles and applications

The laser scanning cytometer (LSC) is the microscope-based cytofluorometer that offers a plethora of analytical capabilities. Multilaser-excited fluorescence emitted from individual cells is measured at several wavelength ranges, rapidly (up to 5000 cells/min), with high sensitivity and accuracy. The following applications of LSC are reviewed: (1) identification of cells that differ in degree of chromatin condensation (e.g., mitotic or apoptotic cells or lymphocytes vs granulocytes vs monocytes); (2) detection of translocation between cytoplasm vs nucleus or nucleoplasm vs nucleolus of regulatory molecules such as NF-kappaB, p53, or Bax; (3) semiautomatic scoring of micronuclei in mutagenicity assays; (4) analysis of fluorescence in situ hybridization; (5) enumeration and morphometry of nucleoli; (6) analysis of phenotype of progeny of individual cells in clonogenicity assay; (7) cell immunophenotyping; (8) visual examination, imaging, or sequential analysis of the cells measured earlier upon their relocation, using different probes; (9) in situ enzyme kinetics and other time-resolved processes; (10) analysis of tissue section architecture; (11) application for hypocellular samples (needle aspirate, spinal fluid, etc.); (12) other clinical applications. Advantages and limitations of LSC are discussed and compared with flow cytometry.

Chromosome instability in neoplasia: chaotic roots to continuous growth

Multiple rearrangements of chromosome number and structure are common manifestations of genomic instability encountered in mammalian tumors. In neoplasia, in continuous immortalized growth in vitro, and in animal models, the accumulation of various defects on DNA repair and telomere maintenance machineries, mitotic spindle abnormalities, and breakage-fusion-bridge cycles, deteriorate the precise mitotic distribution of the genomic content, thus producing various types of chromosomal anomalies. These lesions generate tremendous genomic imbalances, which are evolutionary selected, since they force the function of the whole genome towards continuous growth. For more than a century chromosomal rearrangements and aneuploidy in neoplasia have been discussed and a vast number of genes and pathways, directly or indirectly implicated, have been described. In this review, we focus on the biological mechanisms that generate numerical or structural deviations of the normal diploid chromosomal constitution in epithelial neoplasia. There is growing evidence that chromosomal instability is both an epiphenomenon and a leading cause of cancer. We will discuss the roles of genes, chromosome structure, and telomere dysfunction in the initiation of chromosomal instability. We will explore research strategies that can be applied to identify rates of chromosomal instability in a specimen, and the putative biological consequences of karyotypic heterogeneity. Finally, we will re-examine the longstanding hypothesis of the generation of aneuploidy in the context of telomere dysfunction and restoration.

Induction of centrosome amplification and chromosome instability in p53-null cells by transient exposure to subtoxic levels of S-phase-targeting anticancer drugs

Chromosome instability (CIN) is one of the most important phenotypes in tumor progression, introducing multiple mutations required for acquisition of further malignant characteristics. Abnormal amplification of centrosomes, which is frequently observed in human cancer, has been shown to contribute to CIN by increasing the frequency of mitotic defects. Here, we show that transient exposure to subtoxic concentrations of commonly used anticancer drugs that target DNA synthesis induces centrosome amplification in cells lacking p53 tumor suppressor protein, by allowing continuous centrosome duplication in the absence of DNA synthesis. When these cells are released from cell cycle arrest by removal of drugs, cells suffer extensive destabilization of chromosomes. Considering that p53 is the most frequently mutated gene in human cancer and that CIN is known to be associated with acquisition of malignant phenotypes, our observations may explain why recurrent tumors, after chemotherapy, often exhibit more malignant characteristics than the original tumors. The tumor cells that are exposed to subtoxic levels of DNA synthesis-targeting drugs will be arrested and undergo centrosome amplification. Upon cessation of chemotherapy, these cells will re-enter cell cycling, and experience extensive CIN due to the presence of amplified centrosomes. This in turn promotes generation of tumor cells equipped with further malignant characteristics.

In vitro aging of rat lung cells. Downregulation of telomerase activity and continuous decrease of telomere length are not incompatible with malignant transformation

Most normal mammalian somatic cells cultivated in vitro enter replicative senescence after a finite number of divisions, as a consequence of the progressive shortening of telomeres during proliferation that reflects one aspect of organism/cellular aging. The situation appears more complex in rodent cells due to physiological telomerase expression in most somatic normal tissues, great telomere length, and the difficulties of finding suitable in vitro culture conditions. To study in vitro aging of rat lung epithelial cells, we have developed primary culture conditions adapted to rat fresh lung explants and have studied for 1 year (50 passages) the changes in cellular proliferation and mortality, genetic instability, telomerase activity, telomere length, and tumorigenic potential. We have observed an absence of senescence and/or crisis, a transient genetic instability, the persistence of a differentiated Clara cell phenotype, a steady decrease in telomerase activity followed by a low residual activity together with a continuous decrease in telomere length, a constant rate of proliferation, and the acquisition of tumorigenic potential. The bypass of the growth arrest and the acquisition of long-term growth properties could be explained by the loss of p16(INK4a) expression, the ARF/p53 pathway not being altered. In conclusion, these results clearly indicate that, in rat lung epithelial cells, in vitro transformation and acquisition of tumorigenic properties can occur even if the telomere length is still decreasing and telomerase activity remains downregulated.

Telomerase activity and genetic alterations in primary breast carcinomas

It has been proposed that the structural and numerical chromosome abnormalities recorded in breast cancer could be the result of telomere dysfunction and that telomerase is activated de novo to provide a survival mechanism curtailing further chromosomal aberrations. However, recent in vivo and in vitro data show that the ectopic expression of telomerase promotes tumorigenesis via a telomere length-independent mechanism. In this study, the relation between telomerase expression and the extent of chromosomal aberrations was investigated in 62 primary breast carcinomas. Telomerase activity was measured using a polymerase chain reaction-based telomeric repeat amplification protocol assay and 92% of the tumors were found to express telomerase with a relative activity ranging from 0 to 3839.6. Genetic alterations were determined by G-banding and comparative genomic hybridization analysis and 97% of the tumors exhibited chromosomal aberrations ranging from 0 to 44 (average: 10.98). In the overall series, the relationship between telomerase activity levels and genetic changes could be best described by a quadratic model, whereas in tumors with below-average genetic alteration numbers, a significant positive association was recorded between the two variables (coefficient=0.374, P=.017). The relationship between telomerase activity levels and the extent of genetic alteration may reflect the complex effect of telomerase activation upon tumor progression in breast carcinomas.