Prognostic value of cytogenetics in multiple myeloma

Karyotypic studies of bone marrow were conducted in 79 previously untreated patients with multiple myeloma who received a standard programme of chemotherapy. An abnormal karyotype was observed in 46% of patients, virtually all showing multiple abnormalities consistent with a long period of preclinical clonal evolution. Patients with an abnormal pattern showed various aberrations with hyperdiploidy in 64%, pseudodiploidy in 5% and hypodiploidy in 31%. The number of chromosomes affected ranged from two to 19 (median 10), with at least one trisomy in 83%, one monosomy in 75%, and one translocation in 42% of patients. Lymphoma-like karyotypes were present in 17% of patients with an abnormality but were not associated with atypical clinical features, such as an extramedullary mass, leukaemia, or increased serum lactate dehydrogenase. Monosomy or deletion of chromosome 13 was present in 47% of patients with an abnormal pattern, who lived for a shorter duration (median 10 months) than patients with other abnormalities (median 34 months) or with diploidy (median 35 months). The cause of the short survival of patients with monosomy or deletion of chromosome 13 was not clear, but further studies on the relationship with specific oncogenes are indicated.     

Clinical and cytogenetic observations during a six-year period in an adult with Fanconi's anaemia

Summary A male adult patient suffering from Fanconi's anemia is described who was diagnosed 5 years before the onset of clinical symptoms by cytogenetic findings of chromosomeinstability in a lymphocyte culture. Repeated clinical, haematological and biochemical investigations of the untreated patient have been made during the observation period of six years. In the same period of time cytogenetic studies have been carried out which show no correlation in results compared with the clinical or physical findings. Four well defined lymphocyte clones have been discovered. The patient is still under observation of the clinic and the cytogenetic department.This work was supported by the Deutsche Forschungsgemeinschaft.     

Variant Philadelphia translocations in chronic myeloid leukaemia can mimic typical blast crisis chromosome abnormalities or classic t(9;22): a report of two cases

A range of fluorescent in situ hybridization techniques have been used to reveal hidden variant Philadelphia translocations in two cases of Ph-positive chronic-phase chronic myeloid leukaemia. In one patient, a highly complex variant Ph translocation affecting four chromosomes had resulted in the formation of structures with the appearance of i(17q) and +8. Misinterpretation of these karyotypes has direct clinical relevance. Our findings illustrate that even established cytogenetic abnormalities may contain cryptic abnormalities beyond the resolution of conventional cytogenetic methods.     

Exopolysaccharide defects cause hyper-thymineless death in Escherichia coli via massive loss of chromosomal DNA and cell lysis

Thymineless death in Escherichia coli thyA mutants growing in the absence of thymidine (dT) is preceded by a substantial resistance phase, during which the culture titer remains static, as if the chromosome has to accumulate damage before ultimately failing. Significant chromosomal replication and fragmentation during the resistance phase could provide appropriate sources of this damage. Alternatively, the initial chromosomal replication in thymine (T)-starved cells could reflect a considerable endogenous dT source, making the resistance phase a delay of acute starvation, rather than an integral part of thymineless death. Here we identify such a low-molecular-weight (LMW)-dT source as mostly dTDP-glucose and its derivatives, used to synthesize enterobacterial common antigen (ECA). The thyA mutant, in which dTDP-glucose production is blocked by the rfbA rffH mutations, lacks a LMW-dT pool, the initial DNA synthesis during T-starvation and the resistance phase. Remarkably, the thyA mutant that makes dTDP-glucose and initiates ECA synthesis normally yet cannot complete it due to the rffC defect, maintains a regular LMW-dT pool, but cannot recover dTTP from it, and thus suffers T-hyperstarvation, dying precipitously, completely losing chromosomal DNA and eventually lysing, even without chromosomal replication. At the same time, its ECA⁺ thyA parent does not lyse during T-starvation, while both the dramatic killing and chromosomal DNA loss in the ECA-deficient thyA mutants precede cell lysis. We conclude that: 1) the significant pool of dTDP-hexoses delays acute T-starvation; 2) T-starvation destabilizes even nonreplicating chromosomes, while T-hyperstarvation destroys them; and 3) beyond the chromosome, T-hyperstarvation also destabilizes the cell envelope.

Acute starvation for thymidine triphosphate (dTTP), one of the four precursors for DNA synthesis, is lethal in both bacterial and eukaryotic cells (1). Following a short resistance phase, the rapid death of thyA auxotrophs in media lacking thymine or thymidine (“T-starvation”) known as thymineless death (TLD) was first described in Escherichia coli (2, 3) and since then was extensively studied to identify the cause of lethality (1, 4, 5). Because the bulk of thymidine (dT) in any cell is used for chromosomal DNA synthesis, lack of dT was always assumed to cause some form of chromosomal damage, and hence the role of DNA repair pathways during T-starvation was the focus of intense investigation (6–9). These studies revealed that certain pathways, like double-strand break repair initiated by the RecBCD helicase/nuclease, Holliday junction resolution by RuvABC, and antirecombination activity of the UvrD helicase, keep cells alive during the resistance phase of T-starvation. Other events, like attempted single-strand gap repair initiated by the RecFOR complex, the function of the RecQ helicase and RecJ exonuclease, and SOS induction of the cell division inhibitor SulA, are detrimental for T-starved E. coli cells (8, 10–12). However, the thyA mutants of E. coli inactivated for all of the latter “toxic DNA repair pathways” still die by two orders of magnitude during T-starvation (8), indicating some other yet-to-be-identified major lethality factors.Since actively growing cells continuously require a lot of dT to replicate chromosomal DNA, existing replication forks were inferred to be the points of TLD pathology (7, 8, 13–15). Indeed, T-starvation severely inhibits chromosomal DNA replication (15) and is associated with accumulation of single-stranded DNA, suggesting generation of single-strand (ss) gaps by attempted replication in the absence of dT (7, 16). These ss-gaps induce the SOS response (7, 8, 17), which contributes to the pathology of TLD by induction of the SulA cell division inhibitor (8). Also, replication initiation spike in the T-starved cells triggers the destruction of the origin-centered chromosomal subdomain during TLD, suggesting that it is the demise of the nascent replication bubbles, rather than the existing replication forks, that eventually kills the chromosome (15, 17).Although the thyA mutants cannot synthesize dT, they grow normally if supplemented with exogenous dT/T. Upon removal of dT from the growth medium, the E. coli thyA strain has a two-generation-long resistance phase (also called the lag phase) (1), when the colony-forming unit (CFU) titer of the culture stays constant (Fig. 1 A, Top). This is followed by the rapid exponential death (RED) phase, when the CFU titer falls by approximately three orders of magnitude within several hours (Fig. 1 A, Top).Open in a separate windowFig. 1.A significant endogenous pool of LMW dT decreases during T-starvation. (A) The phenomenon of TLD in E. coli suggests accumulation of chromosomal damage during the resistance phase (green) that would later kill cells during the RED phase (red). The data are adapted from ref. 16. Henceforth, the data are means (n ≥ 3) ± SEM. Cultures were grown at 37 °C in the presence of dT, which was removed at time = 0, while incubation in the growth medium continued. Top, cell death begins after 1-h-long resistance phase, during which the culture titer is stable. Bottom, during the same first hour without dT, cells manage to synthesize the amount of DNA equal to half of what they already had before dT removal. However, during the RED phase genomic DNA is gradually lost. (B) Scheme of 50% methanol fractionation of the intracellular thymidine into HMW dT (the dT content of the chromosomal DNA) and LMW dT. (C) A 0.7% agarose gel analysis of the HMW and LMW fractions of the 50% methanol-treated cells, as well as pure LB treated the same way, for DNA and RNA content (staining with ethidium bromide). Inverse images of stained gels are shown, in which the indicated samples were either incubated in the buffer or with the indicated enzyme (DNase I for the top gel, RNase A for the bottom gel). (D) The size of the LMW-dT pool, normalized to the HMW-dT content of the chromosome, either during normal growth in dT-supplemented medium or during T-starvation. Thymidine was removed at time = 0. The strain is KKW58.An obvious explanation for the resistance phase is existence of an intracellular source of dT to support slow replication; however, chromosomal DNA amount was consistently reported to remain flat during TLD (15, 18–20). Besides, the recent systematic test of potential candidates for a source of dT or its analogs supporting the resistance phase returned empty-handed (16). Thus, the mechanisms behind the initial resistance to T-starvation, followed by the sudden shift to the RED phase remain unclear, leading to a reasonable assumption that the resistance phase is an integral part of the TLD phenomenon, during which chromosomal damage accumulates until it becomes irreparable, ushering the RED phase (1, 5). Specific early events during the resistance phase of TLD that would later turn poisonous during the RED phase were proposed to be futile incorporation–excision cycles (1, 21), ss-gap accumulation causing the SOS induction (1, 8, 16), futile fork breakage-repair cycles (16, 22), and overinitiation from the origin (5, 15).Two recent observations, in combination with an old popular TLD explanation, further support the idea of the resistance phase as the TLD period during which chromosomal damage accumulates without affecting viability for the time being. First, the resistance phase coincides with accumulation of double-strand breaks in the chromosome, which then paradoxically disappear during the RED phase (7, 16). Second (and in contrast to the reports mentioned above of constant chromosomal DNA amount during T-starvation) (15, 18–20), we have found that during the resistance phase the amount of the chromosomal DNA actually increases ∼1.5 times over the prestarvation level, but then the chromosomal DNA is apparently destabilized during the RED phase, since it is slowly reduced to the original level (16) (Fig. 1 A, Bottom). Therefore, both the apparent chromosomal replication and the significant chromosome fragmentation during the resistance phase could lead to accumulation of chromosomal damage (SOS induction is an indicator of this accumulation) (7).On the other hand, the early DNA synthesis and the resistance phase in T-starved cells could reflect the existence of a source of dT, available early on during T-starvation, that fuels the initial DNA accumulation and delays viability loss until this pool is exhausted. In other words, the resistance phase could simply postpone TLD, rather than being an integral part of it. Previously, we have tested the two obvious high-molecular-weight (HMW) dT sources, namely, the stable RNAs and the chromosomal DNA, but found that incapacitation of neither one reduced the resistance phase or precluded the early DNA synthesis during T-starvation (16). Thus, the question of whether the resistance phase is a part of the TLD phenomenon remains unresolved.In the current study, we investigated a seemingly remote possibility of a substantial low-molecular-weight (LMW)-dT pool supporting the resistance phase of T-starvation in E. coli. While the bulk of dTTP in E. coli immediately incorporates into the chromosomal DNA, a fraction of dTTP is recruited into the dTDP-hexose pool (23), to participate in the synthesis of the exopolysaccharide (EPS) capsule, made of core lipopolysaccharide (LPS) (24), O-antigen (OA) (25), and enterobacterial common antigen (ECA) in E. coli (26). The first step of this recruitment is to conjugate dTTP with glucose; the hexose moiety of the resulting dTDP-glucose then undergoes several modifications, before eventually incorporating into oligosaccharide precursors of the outer antigens, while the activating dTDP handle is released back into the DNA precursor pools (26). We ignored LMW dT before because, if the total dT content of the chromosomal DNA is taken for 100%, the pool of dTTP constitutes ∼0.7% of it, while dTDP-glucose (unresolved from other dTDP-hexoses?) adds only another 2.4% (27). No more LMW-dT species are known in the cell, so the total expected LMW-dT pool comes to ∼3% of the total dT content of the chromosomal DNA, not nearly enough to support the resistance phase with its ∼50% increase in the chromosomal DNA mass (Fig. 1A).To investigate the role of the LMW-dT pool in TLD, we started by developing a simple protocol to extract the LMW-dT pool from growing cells and to compare it to the (HMW) chromosomal dT content. Here we show that early on during T-starvation the pool of dTDP-sugars becomes the major source of dTTP for the chromosomal DNA replication. This unexpected rebalancing of the dTTP pool with the help of cell envelope metabolism delays TLD and prevents T-hyperstarvation, a significantly more lethal phenomenon accompanied by complete chromosome destruction and cell lysis.     

异基因造血干细胞移植后伊马替尼维持治疗对Ph＋ALL疗效的Meta分析

目的：系统评价异基因造血干细胞移植（Allo-HSCT）后伊马替尼（IM）维持治疗对费城染色体急性淋巴细胞白血病（Ph＋ALL）的疗效。方法计算机检索 Cochrane Library及临床试验注册中心、PubMed、Embase、中国知网、中国生物医学文献数据库、中国万方和中国维普数据库等,并辅以手工检索和文献追溯,获取 Allo-HSCT后 IM维持治疗对 Ph＋ALL疗效的随机对照研究及观察性研究。检索时限均从建库至2014年4月3日。筛选文献并提取资料和评价质量后,采用 Cochrane协作网RevMan5．2软件进行 Meta分析。共纳入7篇研究文献,共计366例 Allo-HSCT后Ph＋ALL患者。分别比较移植后 Ph＋ALL不同 IM治疗起点的疗效差异,及移植后Ph＋ALL是否使用 IM的疗效差异。结果 Allo-HSCT后 IM维持治疗对患者总体生存率、无病生存率、非复发死亡率方面的影响差异有统计学意义（P＜0．05）,其效应统计量风险比（HR）及其95％CI 分别为0．22（0．17～0．27）、0．84（0．80～0．89）、0．41（0．20～0．82）;IM维持治疗对移植后白细胞植入时间及血小板植入时间影响差异无统计学意义（P＞0．05）,其效应统计量均数差（MD）及其95％CI分别为－0．92（－4．35～2．50）、0．78（－1．59～3．16）;对复发率的影响尚存在争议。预防性应用 IM与检测到微小残留病变后应用相比,可降低移植后的分子学复发率,并延长 BCR／ABL持续阴性的时间。但对于缓解持续时间、无病生存期、总生存率及无事件生存率等方面均无明显影响。结论 Allo-HSCT后应用 IM维持治疗可提高Ph＋ALL患者总体生存率,改善无病生存率并降低非复发死亡率,对白细胞、血小板植入时间无明显影响,对复发率的影响尚存在争议。移植后早期检测到BCR／ABL阳性与不良预后相关,而移植后 IM最佳治疗起点尚无定论。     

男性Y染色体AZF微缺患者在不育症中的相关性研究

目的对不育男性患者的Y染色体长臂上的AZF区进行微缺失检测,研究Y染色体AZF区的微缺失与男性患者不育的相关性。方法运用多重聚合酶链反应(PCR)扩增-凝胶电泳方法对332例不育男性患者及100名有生育能力的男性健康对照者进行外周血Y染色体长臂AZF区域微缺失基因检测。结果 332例不育男性患者中检出28例AZF区不同程度微缺失,缺失率比例达8.4%。其中152例无精症男性不育患者中检出12例AZF区微缺失;180例少精症不育男性患者中检出16例AZF区微缺失。100名有生育能力的男性健康对照者均未发现AZF微缺失。结论 Y染色体长臂AZF区微缺失是男性原发性不育的重要致病因素。对不育男性患者进行Y染色体AZF区域进行微缺失检测有助于临床诊断不育症病因及降低男性不育患者通过辅助生殖技术进行受孕时将此缺陷遗传给其男性后代的风险。     

厦门地区69例原发闭经患者的染色体核型分析

目的探讨厦门地区原发性闭经患者各种异常染色体核型的分布情况及其有关临床体征和意义。方法采用外周血淋巴细胞染色体培养技术进行染色体核型分析。结果 69例原发闭经患者共检出染色体异常28例,异常检出率为40.6%,其中X染色体数目异常8例,占28.6%;X染色体数目异常及嵌合体6例,占21.4%;X染色体结构异常5例,占17.9%;X染色体结构异常及嵌合体3例,占10.7%;染色体倒位3例,占10.7%;性反转2例,占7.1%;与常染色体易位1例,占3.6%。结论染色体异常是导致原发性闭经的主要病因之一,对原发闭经患者进行细胞遗传学检查,对确定其病因及治疗方案具有重要意义。     

急性淋巴细胞白血病病人Ikaros6基因表达及意义

目的探讨Ikaros6基因在急性淋巴细胞白血病（ALL）病人中的表达及临床意义。方法对95例ALL病人进行R-显带染色体核型分析,再采用逆转录PCR方法检测Ikaros6基因的表达,基因测序确定Ikaros6基因突变的位置及类型;应用荧光定量PCR测定初诊及缓解病人Ikaros6mRNA的表达,并通过临床随访观察不同病人采用不同治疗方案的疗效。结果 95例ALL病人中有45例Ph染色体阳性,50例Ph染色体阴性;在Ph染色体阳性和阴性病人中分别有13例和2例表达Ikaros6,差异有显著性（χ2=11.03,P〈0.05）。健康对照组均未检测到Ikaros6基因的表达。表达Ikaros6的病人基因测序均显示IKZF1中外显子4~7的缺失。初诊病人Ikaros6mRNA平均表达量明显高于缓解病人（t=4.054,P〈0.05）。Ph染色体阳性ALL病人接受络氨酸酶抑制剂（TKIs）治疗后,有Ikaros6基因表达的病人其缓解率明显低于未表达该基因病人（χ2=6.20,P〈0.05）;未表达Ikaros6基因Ph染色体阳性ALL病人,接受TKIs治疗的缓解率明显高于VDCP治疗方案（χ2=5.43,P〈0.05）。表达Ikaros6的Ph染色体阳性ALL病人20个月平均累积复发时间明显短于未表达Ikaros6病人（Waldχ2=13.72,P〈0.05）。结论 IKZF1外显子4~7缺失导致Ikaros6基因在Ph染色体阳性ALL病人中高表达,表达该基因的病人对TKIs具有明显的抵抗作用,TKIs和VDCP方案对于此类病人的治疗效果均不理想,复发率高。