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[Characteristics of clonal evolution in patients with myelocytic leukemia].

The authors report the results of the clinical, cytochemical, cytogenetic and kinetic studies (3H-thymidine autoradiography and scanning integrating cytospectrophotometry of DNA) in a male patient with chronic myeloleukemia with blast infiltration of the lymph nodes. Analysis of the karyotype and kinetic aspects of leukemic cells obtained from the blood, bone marrow, spleen and hyperplastic lymph nodes was performed over time at different disease periods. Based on the data obtained the authors suggest that aneuploid blasts may maturate before segmented granulocytes. The probability of the medullary origin of aneuploid clones is discussed.

Bone Marrow

Clonal evolution of karyotype in blastic phase of CML.

A patient with chronic myelocytic leukemia (CML) had a Philadelphia chromosome--Ph1(t(9q +; 22q--)) in all evaluated bone marrow cells at the time of diagnosis. After 29 months of intermittent therapy (chemotherapy and immunotherapy) and 2 months before clinical signs of blastic phase developed, three additional cell lines in bone marrow and peripheral blood appeared: one line with extra chromosome Ph1, another one in which chromosome Y disappeared, and the third line with extra chromosome No. 13, evidently derived from the X-monosomie cell line. Five weeks before death a variable hypodiploidy was found in more than 50% mitoses. The patient died 47 months after the establishment of CML and seven months after the onset of the blastic phase.

Chromosome Aberrations

Simultaneous presence, in one serum, of four monoclonal antibodies that might correspond to different steps in a clonal evolution from polyreactive to monoreactive antibodies.

Three monoclonal IgG of different subclasses (IgG1, IgG2, and IgG4) and one IgA1 were isolated from the serum of patient Per suffering from an immunocytic sarcoma. All four monoclonal Ig shared the same N-terminal sequence of their H chains (VH3). Furthermore, their kappa-chains exhibited identical isoelectric charges and N-terminal sequences (VK2) and expressed the same private idiotope. A strong antitubulin activity was found in IgA1Per and in two of the three monoclonal IgGPer. The specificity was restricted to tubulin for IgA1Per and IgG4Per, whereas IgG1Per also displayed significant polyreactive bindings and IgG2Per failed to react with any of the Ag tested. The monoreactive IgG4Per, as well as the polyreactive IgG1Per, bound a large peptide in the central part of both alpha and beta subunits of tubulin (amino acid position 100 to 300). In contrast, the monoreactive IgA1Per bound to a rarely detected epitope close to residue 310 of these subunits. The tubulin epitope recognized by polyreactive IgG1Per was similar to that of germ-line-encoded polyreactive antibodies. It is hypothesized that IgG4Per- and IgA1Per-producing cells derive from the IgG1Per polyreactive clone after somatic events leading to the production of monoreactive antibodies.

Amino Acid Sequence

Change in karyotype between diagnosis and first relapse in acute myelogenous leukemia.

We compared karyotype at first relapse with presenting karyotype in 212 patients with AML seen at MD Anderson Cancer Center (Houston, TX, USA) between 1975 and 1994. In 38% the karyotypes at diagnosis and relapse were identical. A stable karyotype was most frequent (70%) among patients who presented without cytogenetic abnormalities, suggesting that the finding of a normal karyotype is usually not due to sampling error. In contrast, a finding of insufficient metaphases at diagnosis was repeated at relapse in only 6% of cases. A change in karyotype occurred in 67% of 101 patients who presented with an abnormal karyotype and had sufficient metaphases for evaluation at relapse. The great majority of changes involved clonal evolution, clonal devolution (regression), or both; a purely normal karyotype and unrelated clones were seen in 11 and three of the 101, respectively. Change in karyotype between diagnosis and relapse and type of change were unrelated to remission duration. The only group in which karyotype at relapse vs that at diagnosis had a possible bearing on achievement of second CR were patients who presented with abnormalities other than inv(16), t(8;21) or t(15;17) and who at relapse had only normal metaphases; such patients had higher CR rates than comparable patients who retained their presenting abnormalities.

Chromosome Aberrations

A single-cell lens into the co-evolution of genotypes and phenotypes in cancer.

Genetic heterogeneity and clonal outgrowths are observed even in otherwise healthy human tissues, shaping the genetic composition of cell populations in non-malignant disease and during physiological ageing. This clonal mosaicism likely provides the pre-cancerous seeds for malignant transformation. Once a tumour arises, clonal evolution poses a major challenge to achieving cure, as clonal diversification provides an expanded number of substrates upon which therapy can act as a selective pressure, leading to the selection of resistant clones that ultimately fuel disease recurrence. Understanding somatic clonal evolution requires not only mapping genetic diversity but also defining the resulting phenotypes that provide a fitness advantage to mutated clones. This Review discusses multimodal single-cell technologies that enable the measurement of genotypes and additional molecular features from the same cell. These technologies unveil mutant-specific phenotypic traits, often show cell-state specificity in genotype-phenotype effects and can define therapeutic vulnerabilities for precision elimination of disease-propagating mutant cells. Furthermore, the combination of phylogenetic reconstruction with phenotypic measurements allows for the temporal mapping of clonal evolution and phenotypic plasticity. These breakthroughs have created a unique opportunity to define, directly in primary human samples, the mechanisms underlying clonal expansion in both healthy and malignant tissues.

Journal Article

Clonal cytogenetic evolution in a squamous cell carcinoma of the skin from a xeroderma pigmentosum patient.

Cytogenetic changes in epithelial neoplasms are often complex, making it difficult to determine which are the primary abnormalities and which are secondary. In this report, we describe clonal evolution in a cytogenetically simple, but clinically aggressive squamous cell cancer of the skin from a patient with xeroderma pigmentosum. Chromosome preparations were analyzed from a direct harvest, three independent primary harvests, and passaged cell lines. Three closely related tumor subclones were identified in the primary cultures, and all three proliferated in vitro. Monosomy 4 and a chromosome 9 rearrangement were present in all three subclones and monosomy 21 was present in two subclones. An i(9p) and an i(9q) were derived from the same chromosome 9, and there was concurrent loss of the homologous chromosome 9. In addition, each subclone was characterized by a further specific evolutionary change: t(5;7) (q11.2;p22) in subclone 1, der (11)t(10;11) (q21;p14) in subclone 2, and der (14)t(13;14) (q14;q32) in subclone 3. All three subclones were represented by hypodiploid and hypotetraploid metaphases. Loss of chromosomes from hypotetraploid cells and an 11q+ were the only other changes found in this tumor. The early genetic events in the evolution of this squamous cell cancer, monosomy 4, i(9p), i(9q), and monosomy 21, represent loss of chromosome regions that are commonly lost in other squamous cell carcinomas of the head and neck region. Taken together, these observations indicate that genes on these chromosomal regions are probably important and possibly sufficient for the development of squamous cell carcinoma.

Adult

Clonal karyotypic evolution in a pediatric neurofibrosarcoma.

A retroperitoneal neurofibrosarcoma infiltrating the spine of a 2-year-old boy was investigated cytogenetically three times over a 5-month period. The first sample, from a diagnostic fine-needle aspiration biopsy, had a supernumerary i(1)(q10) as the sole clonal aberration; two cells showed monosomy 18 in addition to the isochromosome. The second sample, obtained at tumor resection 3 weeks later, had the karyotype 47,XY, +i(1)(q10), -18, +21/45,XY, -18. After 5 months, a large local recurrence was resected. The chromosome analysis showed further clonal evolution: 45,XY, +1,der (1;11)dic(1;11)(q44;q13)i(1)(q10), inv(6)(p21q12), -17. The findings indicate that formation of i(1)(q10) and loss of chromosome 18 may be early genetic events in neurofibrosarcoma development.

Child, Preschool

Parallel karyotypic evolution and tumor progression in uterine leiomyoma.

Cytogenetic evidence of clonal evolution was detected in five uterine leiomyomas. In two tumors, two clones were found, the third tumor had four, the fourth had nine, and the fifth had 12 clones. The first tumor had trisomy 12 as the primary anomaly and a sideline that also contained a del(7)(q21q31). Both clones of the second tumor had three structural changes in common but differed by the presence in the more advanced clone of an inv(7)(q31q34). Two cytogenetically unrelated pairs of clones were seen in the third tumor. One clone had a stemline of 46 and an r(1); a sideline had developed through duplication of this clone. The other pair had a del(7)(q21q31) in common. The last two tumors both had t(12;14)(q14-15;q23-24) as the primary abnormality. They also had a high frequency of telomeric associations that involved certain chromosome arms only. One of the secondary changes in the fourth tumor was a del(7)(q21q31); the principal secondary change in the fifth case was a ring chromosome 1 of variable size in the different clones. The analysis of these five uterine leiomyomas and the collation of the results with previously obtained data lead us to conclude that del(7)(q21q31) is secondary to t(12;14) and + 12 in this tumor type, and that ring formation involving chromosome 1 material, often with duplication of segments, is a common phenomenon during clonal evolution. The fact that the tumors were classified as cellular and had an increased mitotic rate indicates a parallel development between histologically detectable tumor progression and cytogenetically recognizable clonal evolution in uterine leiomyomas.

Chromosome Aberrations

Mutational Landscape and Clonal Dynamics in AML Undergoing PTCy Hematopoietic Cell Transplantation.

To improve risk stratification, we performed targeted NGS at diagnosis in 191 patients with AML undergoing myeloablative allogeneic HCT with PTCy-based prophylaxis. We also investigated clonal evolution using paired diagnostic and relapse samples from 39 individuals. A total of 610 mutations were detected in 184 patients (96%), most commonly in FLT3 (26%), DNMT3A (25%), RUNX1 (24%), and NPM1 (19%). Sixteen unique fusion genes were identified in 35 patients, with KMT2A (43%) and core binding factor rearrangements (23%) being the most frequent. TP53 and WT1 mutations were strongly associated with adverse outcomes, whereas NPM1 retained favorable significance. RUNX1 co-mutations with SF3B1 or NRAS were associated with inferior survival. In an exploratory allelic analysis, multi-hit TP53 alterations, but not single-hit mutations, were associated with distinctly poorer OS, EFS, and relapse risk. Relapse involved mutational shifts in ∼70% of cases, with significant enrichment of WT1 and more modest increases in TP53, KRAS, ASXL1, NF1, and MECOM, while DNMT3A, TET2, and ASXL1 persisted stably. Neither acute nor chronic graft-versus-host disease was associated with molecular remodeling at relapse. Incorporating TP53 and WT1 into risk models, recognizing context-dependent effects of DNMT3A and RUNX1, and applying longitudinal genomic monitoring may help guide personalized strategies to prevent relapse. Extended abstract BACKGROUND Relapse remains the leading cause of treatment failure after allogeneic hematopoietic cell transplantation (HCT) for acute myeloid leukemia (AML), yet the genetic mechanisms underlying post-transplant relapse remain poorly understood, particularly in the era of post-transplant cyclophosphamide (PTCy). Characterizing the mutational landscape at diagnosis and the clonal evolution leading to relapse may improve post-transplant risk stratification and identify opportunities for personalized surveillance and intervention. OBJECTIVES To characterize the diagnostic mutational landscape, evaluate its prognostic significance, and investigate clonal evolution from diagnosis to relapse in AML patients undergoing myeloablative HCT with PTCy-based graft-versus-host disease prophylaxis. STUDY DESIGN We performed targeted next-generation sequencing (NGS) at diagnosis in 191 consecutive AML patients undergoing myeloablative allogeneic HCT with PTCy-based prophylaxis. Paired diagnostic and relapse samples were available for 39 patients to evaluate clonal evolution. RESULTS A total of 610 mutations were detected in 184 patients (96%), most commonly in FLT3 (26%), DNMT3A (25%), RUNX1 (24%), and NPM1 (19%). Sixteen unique fusion genes were identified in 35 patients, with KMT2A (43%) and core binding factor rearrangements (23%) being the most frequent. TP53 and WT1 mutations were strongly associated with adverse outcomes, whereas NPM1 retained favorable significance. RUNX1 co-mutations with SF3B1 or NRAS were associated with inferior survival. In an exploratory allelic analysis, multi-hit TP53 alterations, but not single-hit mutations, were associated with distinctly poorer OS, EFS, and relapse risk. Relapse involved mutational shifts in ∼70% of cases, with significant enrichment of WT1 and more modest increases in TP53, KRAS, ASXL1, NF1, and MECOM, while DNMT3A, TET2, and ASXL1 persisted stably. Neither acute nor chronic graft-versus-host disease was associated with molecular remodeling at relapse. CONCLUSIONS This study provides a comprehensive characterization of the mutational landscape and clonal evolution of AML undergoing contemporary PTCy-based allogeneic HCT. TP53 and WT1 identify patients at particularly high risk of post-transplant relapse, whereas NPM1 retains favorable prognostic significance. The frequent acquisition of new genetic lesions at relapse underscores the dynamic nature of post-transplant clonal evolution and supports longitudinal molecular monitoring together with genomically informed post-transplant surveillance and relapse-prevention strategies.

Clonal Dynamics

Rapid production of diversity during the progression of a mixed lineage leukaemia.

A leukaemia presenting with two morphologically different blast populations failed to respond to either antimyeloid or antilymphoid treatment and showed a rapid clinical progression. Immunophenotyping provided good evidence for two blast populations, one lymphoid and the other lymphoid with granulocyte monocytic markers. Two different gene rearrangements within JH were also observed with band densities corresponding to the sizes of the two blast cell populations. A t(19; 22) translocation was observed in almost all cells at presentation one of which evolved into a subclone, becoming dominant in the terminal phase of the disease. We show here both the clonal evolution and clonal competition that occurred in this leukaemia and suggest that the potential of the tumour stem line for rapidly producing diversity was the reason for the resistance to treatment.

Bone Marrow

Chronic myelogenous leukemia in blast crisis. Analysis of 242 patients.

Two hundred forty-two patients with Philadelphia chromosome-positive chronic myelogenous leukemia in blast crisis were reviewed to identify significant biologic and prognostic associations. Twenty percent of patients had lymphoid blast crisis. Clonal evolution was present in 60 percent of patients at blast crisis and involved most frequently the development of a double Philadelphia chromosome, trisomy 8, or isochromosome 17. The overall median survival from blast crisis was 18 weeks. Patient characteristics demonstrated to have significant association with short survival were: anemia; thrombocytopenia; myeloid or undifferentiated blast cell morphology; clonal evolution involving the presence of a double Philadelphia chromosome, trisomy 8, or isochromosome 17; and low marrow blast percentage. Of 195 patients who received therapy for blast crisis, complete remission was achieved in 44 (23 percent) patients, and 24 (13 percent) patients had a partial remission or hematologic improvement. Lower complete remission rates were associated with old age, thrombocytopenia, myeloid or undifferentiated blast cell morphology, clonal evolution--especially isochromosome 17 and trisomy 8--and long interval from diagnosis to onset of blast crisis. A multivariate analysis identified two characteristics to have independent prognostic importance for both survival and remission: platelet counts and blast cell morphology. In addition, clonal evolution had additive prognostic value for survival (double Philadelphia chromosome) and for response (isochromosome 17). The beneficial association of therapy with survival was demonstrated by the significantly longer median survival of patients treated since 1981 compared with those treated earlier, even after accounting for the pretreatment prognostic factors, and by the significant improvement in survival of patients achieving remission using the "landmark" analysis technique.

Blast Crisis

Clues from natural history and results of treatment supporting the monoclonal origin of germ cell tumours.

Recent observations have suggested that a major factor in the development of germ cell tumours may be excessive mitogenic stimulus developed because of failure of feedback suppression of the normal pituitary drive due to atrophic damage to germinal epithelium. With this observation and the increasing recognition that there is a common in situ stage which precedes both seminoma and malignant teratoma/non-seminoma there has been a polarisation of views regarding the relationship between seminoma and malignant teratoma/non-seminoma, with some authors viewing these two entities as separate unrelated transformational events while others hypothesise that seminoma is an interim stage of clonal evolution associated with increased malignant potential towards malignant teratoma/non-seminoma. This chapter reviews the clinical evidence supporting the concept of clonal evolution which arises from the observation that the modal DNA content of seminoma (3.6N) is intermediate between that of in situ carcinoma (4.2N) and malignant teratoma/non-seminoma (2.8N). These observations, taken with the observation that the median age of patients with mixed tumours containing both seminoma and non-seminoma elements (30 years) is intermediate between the slower growing seminoma (35 years) and faster growing malignant teratoma/non-seminoma (25 years), as well as studies of spontaneous regression, tumours in AIDS patients chemo/radio sensitivity and post mortem histology, provide the most convincing evidence supporting clonal evolution. However, these observations cannot explain the fact that some patients have more than one focus of tumour (which can be of different histological type) in a single testis with normal tubules in between, even if they have in situ carcinoma. An extreme manifestation is seen in patients who are treated and cured from metastases arising from one testicle who then die from metastases from a completely different histological type arising from a second transformation event of a germ cell in the contralateral testis. The conclusion from these observations is that it is indeed possible for polyclonal development of tumours to occur, as is seen for bladder and bowel tumours, but they do not detract from the concept that seminoma is an intermediate event in the evolution from in situ carcinoma to malignant teratoma/non-seminoma.

Adult

Characterization of clonal immunoglobulin heavy chain and I cell receptor gamma gene rearrangements during progression of childhood acute lymphoblastic leukemia.

Instability of antigen receptor gene rearrangements during progression of acute lymphoblastic leukemia (ALL) has important implications for polymerase chain reaction (PCR)-based techniques using these genes for the detection of minimal residual disease (MRD). Antigen receptor gene instability may lead to false negative results in bone marrow samples taken during remission. Utilizing the PCR and consensus primers for rearranged immunoglobulin heavy chain (IgH) and T cell receptor gamma (TCR gamma) gene sequences, we analyzed the bone marrow samples at diagnosis and first relapse for 37 children with ALL. The incidence of clonal evolution at the IgH locus was 9/33 (27%) and at the TCR gamma locus 1/15 (7%). In four of the nine patients with clonal evolution at the IgH locus, the sequence at relapse retained the diversity and joining region (D-N-J) sequences from diagnosis. Patients with clonal evolution were characterized by a higher incidence of more than one IgH PCR band at diagnosis and by late relapse (> 18 months from diagnosis). These results suggest that, where possible, patients with more than one IgH PCR rearrangement at diagnosis should be monitored using another antigen receptor gene, such as TCR gamma, since evolution for this gene was found to be a rare event. By combining this approach with a strategy directed at the more stable D-N-J region of the IgH gene, MRD false negativity would have occurred in less than 10% of patients in the present study.

Adolescent