The evolution of single cell-derived colorectal cancer cell lines is dominated by the continued selection of tumor-specific genomic imbalances, despite random chromosomal instability

Intratumor heterogeneity is a major challenge in cancer treatment. To decipher patterns of chromosomal heterogeneity, we analyzed six colorectal cancer cell lines by multiplex interphase FISH (miFISH). The mismatch-repair-deficient cell lines DLD-1 and HCT116 had the most stable copy numbers, whereas aneuploid cell lines (HT-29, SW480, SW620 and H508) displayed a higher degree of instability. We subsequently assessed the clonal evolution of single cells in two colorectal carcinoma cell lines, SW480 and HT-29, which both have aneuploid karyotypes but different degrees of chromosomal instability. The clonal compositions of the single cell-derived daughter lines, as assessed by miFISH, differed for HT-29 and SW480. Daughters of HT-29 were stable, clonal, with little heterogeneity. Daughters of SW480 were more heterogeneous, with the single cell-derived daughter lines separating into two distinct populations with different ploidy (hyper-diploid and near-triploid), morphology, gene expression and tumorigenicity. To better understand the evolutionary trajectory for the two SW480 populations, we constructed phylogenetic trees which showed ongoing instability in the daughter lines. When analyzing the evolutionary development over time, most single cell-derived daughter lines maintained their major clonal pattern, with the exception of one daughter line that showed a switch involving a loss of APC. Our meticulous analysis of the clonal evolution and composition of these colorectal cancer models shows that all chromosomes are subject to segregation errors, however, specific net genomic imbalances are maintained. Karyotype evolution is driven by the necessity to arrive at and maintain a specific plateau of chromosomal copy numbers as the drivers of carcinogenesis.

Single Chromosome Aneuploidy Induces Genome-Wide Perturbation of Nuclear Organization and Gene Expression

Chromosomal aneuploidy is a defining feature of carcinomas and results in tumor-entity specific genomic imbalances. For instance, most sporadic colorectal carcinomas carry extra copies of chromosome 7, an aneuploidy that emerges already in premalignant adenomas, and is maintained throughout tumor progression and in derived cell lines. A comprehensive understanding on how chromosomal aneuploidy affects nuclear organization and gene expression, i.e., the nucleome, remains elusive. We now analyzed a cell line established from healthy colon mucosa with a normal karyotype (46,XY) and its isogenic derived cell line that acquired an extra copy of chromosome 7 as its sole anomaly (47,XY,+7). We studied structure/function relationships consequent to aneuploidization using genome-wide chromosome conformation capture (Hi-C), RNA sequencing and protein profiling. The gain of chromosome 7 resulted in an increase of transcript levels of resident genes as well as genome-wide gene and protein expression changes. The Hi-C analysis showed that the extra copy of chromosome 7 is reflected in more interchromosomal contacts between the triploid chromosomes. Chromatin organization changes are observed genome-wide, as determined by changes in A/B compartmentalization and topologically associating domain (TAD) boundaries. Most notably, chromosome 4 shows a profound loss of chromatin organization, and chromosome 14 contains a large A/B compartment switch region, concurrent with resident gene expression changes. No changes to the nuclear position of the additional chromosome 7 territory were observed when measuring distances of chromosome painting probes by interphase FISH. Genome and protein data showed enrichment in signaling pathways crucial for malignant transformation, such as the HGF/MET-axis. We conclude that a specific chromosomal aneuploidy has profound impact on nuclear structure and function, both locally and genome-wide. Our study provides a benchmark for the analysis of cancer nucleomes with complex karyotypes.

Effects of single and repeated treatment with antidepressants on apomorphine-induced yawning in the rat: the implication of alpha-1 adrenergic mechanisms in the D-2 receptor function

Acute (10 or 20 mg/kg IP) and subchronic (2 x 5 or 10 mg/kg IP daily for 7 days) effects of desipramine, imipramine, maprotiline, (+)- and (-)-oxaprotiline enantiomers as well as selective 5-HT-uptake inhibitors citalopram and ifoxetine on yawning, induced by low doses of apomorphine, were investigated in the rat. In addition, the effects of alpha-1 receptor agonist adrafinil and antagonist prazosin were also tested. After acute treatment, desipramine, the stereoselective NA-uptake inhibiting (+)-enantiomer of oxaprotiline, and the alpha-1 agonist adrafinil, markedly and significantly suppressed yawning. Prazosin, in contrast, clearly potentiated it. This potentiating effect was abolished by the pretreatment with (+)-oxaprotiline and adrafinil. Other drugs were inactive. After subchronic administration, yawning was antagonized by NA-uptake-inhibiting antidepressants, including imipramine and maprotiline. By comparison to the acute treatment, the inhibitory effects of desipramine and (+)-oxaprotiline were considerably enhanced. Neither selective 5-HT-uptake inhibitors nor (-)-oxaprotiline (levoprotiline) were active. Antidepressants therefore modulate the functional activity of D-2 receptors, activated by low doses of apomorphine, predominantly by the virtue of their noradrenergic enhancing properties. This modulatory effect appears to be mediated by alpha-1 adrenergic receptors.

Differential effects of anxiolytics and beta-receptor blocking drugs on novelty-oriented ("neophobic") behavior in the rat

The effects of diazepam, I-propranolol and isamoltane (CGP 361 A) (I-isopropylamino-3[2-(I-pyrrolyl)-phenoxy]-2-propranol), a drug with beta-receptor blocking and anxiolytic-like properties, on behavioral responses in rats encountering either a novel object or a drinking bottle in an unfamiliar open-field ("neophobic" behavior) were evaluated. Diazepam (1-5 mg/kg p.o.) and isamoltane (0.5-1.0 mg/kg p.o.) showed a similar pattern of effects in both test paradigms used. They counteracted the fear-induced suppression of behavioral responses in the presence of novelty: they shortened the approach latencies, increased the exploration-oriented activities and reduced grooming. Propranolol, however, in comparison with isamoltane (1.0 and 2.5 mg/kg i.p.) at equivalent doses, failed to significantly change any of the parameters measured in either of the two test situations. The results therefore indicate that neophobic behavioral responses discriminate between central anxiolytic and peripheral beta-blocking actions of drugs and further validate neophobic behavior as an animal model of anxiety.

Suppressant effect of REM sleep deprivation on neophobia in normal rats and in rats with selective DSP-4 induced damage of locus coeruleus neurons

The influence of REM sleep deprivation (REMD) on open field behavior of normal and locus coeruleus (LC)-damaged animals was investigated under the assumption that REMD suppresses neophobia in rats. REMD (for 24 or 72 hr, water tank technique) produced marked changes in behavior of rats encountering a novel object (white cube) in the center of the open field. REMD induced an increase in activity of treated rats; latency to the object approach was shorter, the number of center entries, time spent in object exploration, frequency of ambulation and rearing were significantly higher than in controls, also defecation was nearly abolished. LC-damage (using DSP-4, a selective central noradrenergic neurotoxin) induced neophobic-like reactions manifested by significantly prolonged latency, tendency to decreased object exploration, center entries and reduction of ambulation and rearing. This "neophobic" behavior of DSP-4 rats was counteracted by REMD as well as by subchronic, but not acute treatment, with antidepressant oxaprotiline (2 X daily for 8 days, 10 mg/kg, IP). The results provide strong support for antineophobic activity of REMD. In addition, they indicate possible similarity of REMD and subchronic oxaprotiline action on neophobia-like behavior in rats with damaged LC-neurons.

Neophobia in spontaneous hypertensive (SHR) and normotensive control (WKY) rats

Latency of approaching a novel object (white-colored cube) placed in an unfamiliar open field, duration of object exploration, ambulation, rearing, grooming, and defecation were investigated in spontaneous hypertensive rats (SHR), their genetic normotensive controls (WKY), and standard Laboratory rats of Wistar origin (Tif:RAIf). The parameters measured were taken as indices of fear due to novelty (neophobia). Remarkable differences in behavior of all three strains were observed. By comparison to RAIf and WKY rats, SHR showed decreased neophobia as reflected in the significantly shorter latency of approaching the object and enhanced ambulation and rearing activity in the open field. By comparison to RAIf rats SHR also showed reduced grooming and defecation. WKY rats distinguished themselves from both SHR and RAIf by almost total absence of all responses in this test situation. This behavioral suppression was antagonized by 7.5 mg/kg ip of chlordiazepoxide. The results of this study further support the notion that, by comparison to standard laboratory rats, both SHR and WKY rats show possible genetically determined, altered behaviors which are diametrically opposite to each other.

Novelty-oriented behavior in the rat after selective damage of locus coeruleus projections by DSP-4, a new noradrenergic neurotoxin

Open-field behavior and reactions to a novel object (white-colored cube) or a familiar object (drinking bottle) were investigated in rats treated with DSP-4 N-(2-chloroethyl) -N-ethyl-2-bromobenzylamine, a new noradrenergic neurotoxin which selectively damages locus coeruleus projections. Altered behavior in the open-field and in the presence of the novel object (white cube) was observed in DSP-4 rats. This was reflected in decreased exploration-oriented locomotor responses and in longer latencies to approach the novel cube. Also, there was a trend towards fewer center entries and a shorter duration of object exploration. Although these behavioral responses of DSP-4 rats were indicative of enhanced neophobia, other measures of emotionality, such as grooming and defecation, were either unchanged or slightly decreased. Moreover, when the familiar drinking bottle was present in the open-field, water-deprived DSP-4 rats showed no change in any measure of fear including the latency to the first approach and lick, and the duration of the licking episodes. The results of this study suggest that noradrenergic neurons of the locus coeruleus are involved in the regulation of certain, but not all, novelty-oriented responses in the rat. Explorative behavior in the novel environment seems to be particularly dependent on central noradrenaline.