Chromothripsis in Chronic Lymphocytic Leukemia: A Driving Force of Genome Instability

Management strategies for patients with chronic lymphocytic leukaemia harbouring complex karyotype

Chronic lymphocytic leukaemia (CLL) is a heterogeneous disease characterised by the uncontrolled proliferation of mature lymphocytes. A subset of CLL patients harbouring complex karyotype (CK) presents with poor prognosis and limited treatment options. This review aims to discuss the current understanding of such patient subset, including its molecular landscape, diagnostic approaches, treatment modalities and emerging therapies. Furthermore, it outlines strategies for personalised management to improve clinical outcomes in this challenging patient population.

Genetic hallmarks and clinical implications of chromothripsis in childhood T-cell acute lymphoblastic leukemia

Chromothripsis (cth) is a form of genomic instability leading to massive de novo structural chromosome rearrangements in a one-time catastrophic event. It can cause cancer-promoting alterations, such as loss of sequences for tumor-suppressor genes, formation of oncogenic fusions, and oncogene amplifications. We investigated the genetic background and clinical significance of cth in childhood T-cell acute lymphoblastic leukemia (T-ALL) patients. For this purpose, whole-genome copy number alterations were analyzed in 173 children with newly diagnosed T-ALL using high-density microarrays. Cth was identified in 10 T-ALL samples (5.78%). In six of them, cth occurred in a constitutional background of Nijmegen breakage syndrome (n = 5) or Li-Fraumeni syndrome (n = 1). Cth generated alterations, including deletions of CDKN2A/B (n = 4) and EZH2 (n = 4), amplifications of CDK6 (n = 2), and NUP214::ABL1 and TFG::GPR128 fusions. Cth-positive leukemias exhibited deletions involving the tumor-suppressor genes RB1 (n = 3), TP53 (n = 1) and MED12 (n = 2). Cth-positive T-ALL patients had a lower probability of 5-year overall survival (OS) [0.56 vs. 0.81; hazard ratio (HR) = 4.14 (1.42-12.02) p = 0.017] as did 5-year event-free survival [0.45 vs. 0.74; HR = 3.91 (1.52-10.08); p = 0.012]. Chromothripsis is an infrequent genomic phenomenon in pediatric T-ALL but is significantly associated with cancer-predisposing syndromes and may associate with inferior prognosis.

Plausible mechanisms in malignisation of non-habit related chronic nonhealing traumatic ulcers of oral cavity

ABSTRACT

Chronic nonhealing ulcers of the oral mucosa and lateral tongue, in particular, can transform into invasive oral squamous cell carcinoma (OSCC). Sometimes these ulcers do not heal even after the removal of the etiological agent that actually initiated these lesions, something similar to what happens in "neoplasia." Numerous factors have been postulated in the literature; however, the exact mechanism remains unclear. We hereby would suggest few plausible factors that could be considered for future studies to shed light on some untapped territories in the pathogenesis of OSCC arising from chronic nonhealing traumatic ulcers in purview of chromoanagenesis and the concepts of "quantum entanglement and coherence."

Chromothripsis in hematologic malignancies

Chromotrypsis, a phenomenon resulting from catastrophic mitotic errors and genomic instability, is defined by the occurrence of multiple DNA double-strand breaks in one or more chromosomes, subsequently subject to error-prone repair mechanisms. This unique process results in extensive rearrangements in the affected chromosomes, leading to loss of tumor suppressor function, the creation of fusion genes, and/or activation of oncogenes. The importance of chromothripsis in cancer, especially in the field of hematologic disorders, underscores the intricate interplay between genomic instability and the genesis of alterations that contribute to cancer. This accentuates the critical need to unravel these complex processes for the targeted development of specific therapeutic interventions. This review delves into the analysis of chromothripsis cases in various hematologic diseases, such as leukemia, lymphoma, and myeloma, with the aim of unveiling its profound impact on patient prognosis. Furthermore, the study explores the intricate molecular mechanisms underlying chromothripsis and investigates its consequences.

A Peculiar CLL Case with Complex Chromosome 6 Rearrangements and Refinement of All Breakpoints at the Gene Level by Genomic Array: A Case Report

INTRODUCTION

Chronic lymphocytic leukemia (CLL), the most common leukemia in Western countries, is a mature B-cell chronic lymphoproliferative disorder characterized by the accumulation of neoplastic CD5+ B lymphocytes, functionally incompetent and usually monoclonal in origin, in bone marrow, lymph nodes and blood. Diagnosis occurs predominantly in elderly patients, with a median age reported between 67 and 72 years. CLL has a heterogeneous clinical course, which can vary from indolent to, less frequently, aggressive forms. Early-stage asymptomatic CLL patients do not require immediate therapeutic intervention, but only observation; treatment is necessary for patients with advanced disease or when "active disease" is observed. The most frequent autoimmune cytopenia (AIC) is autoimmune haemolytic anaemia (AHIA). The main mechanisms underlying the appearance of AIC in CLL are not fully elucidated, the predisposition of patients with CLL to suffering autoimmune complications is variable and autoimmune cytopenia can precede, be concurrent, or follow the diagnosis of CLL.

CASE PRESENTATION

A 74-year-old man was admitted to the emergency room following the finding of severe macrocytic anaemia during blood tests performed that same day, in particular the patient showed a profound asthenia dating back several months. The anamnesis was silent and the patient was not taking any medications. The blood examination showed an extremely high White Blood Cell count and findings of AIHA in CLL-type mature B-cell lymphoproliferative neoplasia. Genetic investigations: Conventional karyotyping was performed and it obtained a trisomy 8 and an unbalanced translocation between the short arm of chromosome 6 and the long arm of chromosome 11, concurrent with interstitial deletions in chromosomes 6q and 11q that could not be defined in detail. Molecular cytogenetics (FISH) analyses revealed Ataxia Telangiectasia Mutated (ATM) monoallelic deletion (with loss of ATM on derivative chromosome 11) and retained signals for TP53, 13q14 and centromere 12 FISH probes. TP53 and IGHV were not mutated. Array-CGH confirmed trisomy of the entire chromosome 8 and allowed us to resolve in detail the nature of the unbalanced translocation, revealing multiple regions of genomic losses on chromosomes 6 and 11.

DISCUSSION

The present case report is an unusual CLL case with complex karyotype and refinement of all breakpoints at the gene level by the genomic array. From a genetic point of view, the case under study presented several peculiarities.

CONCLUSIONS

We report the genetic findings of a CLL patient with abrupt disease onset, so far responding properly to treatments despite the presence of distinct genetic adverse traits including ATM deletion, complex karyotype and chromosome 6q chromoanagenesis event. Our report confirms that interphase FISH alone is not able to provide an overview of the whole genomic landscape in selected CLL cases and that additional techniques are required to reach an appropriate cytogenetic stratification of patients.

Chromosomal Rearrangements and Chromothripsis: The Alternative End Generation Model

Chromothripsis defines a genetic phenomenon where up to hundreds of clustered chromosomal rearrangements can arise in a single catastrophic event. The phenomenon is associated with cancer and congenital diseases. Most current models on the origin of chromothripsis suggest that prior to chromatin reshuffling numerous DNA double-strand breaks (DSBs) have to exist, i.e., chromosomal shattering precedes rearrangements. However, the preference of a DNA end to rearrange in a proximal accessible region led us to propose chromothripsis as the reaction product of successive chromatin rearrangements. We previously coined this process Alternative End Generation (AEG), where a single DSB with a repair-blocking end initiates a domino effect of rearrangements. Accordingly, chromothripsis is the end product of this domino reaction taking place in a single catastrophic event.