The Impact of Cytogenetic Aberrations in the Clonal Evolution of Chronic Myeloid Leukemia: A Single-Center Experience Among 450 Turkish Patients (Cohort Study)

Objective: Chronic myeloid leukemia (CML) is a clonal hematologic disorder characterized by t(9;22) translocation, in which cytogenetic aberrations can occur in Ph(+) and (-) clones. These aberrations develop due to clonal evolution as well as treatment and they have prognostic significance. They are grouped as major and minor route anomalies in terms of their effects on prognostic parameters, such as treatment response, overall survival (OS), disease stage, complete cytogenetic response (CCyR), and major molecular response (MMR). It is stated that major route anomalies have unfavorable prognostic effects compared to minor route anomalies. We aimed to investigate the frequency and prognostic effects of cytogenetic anomalies detected in Ph(+) and (-) clones. Materials and Methods: In this study, we retrospectively analyzed the cytogenetic results of 450 patients diagnosed with CML between 2005 and 2020. Results: We detected cytogenetic aberrations in Ph-positive and negative clones in 41 of 450 patients. The most common anomalies were trisomy 8 (+8), additional Ph chromosome (+Ph), and loss of chromosome Y. Rarely, aneuploidy of the Y chromosome, dup (22), +11, and +6 were seen in CML patients. We observed that these identified aberrations negatively affected MMR and CCyR, and generally resulted in changing imatinib treatment for second-generation tyrosine kinase activity inhibitors. Our results are compatible with the literature. Conclusion: We suggest that cytogenetic aberrations detected in Ph(+) and (-) clones should be a warning sign in terms of treatment and require close observation. The use of cytogenetic methods for the identification of these anomalies is also important.

An Anomaly with Potential as a New Prognostic Marker in CLL with del(13q): Gain of 16p13.3.

Deletion 13q [del(13q)] is a favorable prognostic marker if it is detected as a sole abnormality in chronic lymphocytic leukemia (CLL). However the clinical courses of cases with isolated del(13q) are quite heterogeneous. In our study, we investigated copy number variations (CNVs), loss of heterozygosity (LOH), and the size of del(13q) in 30 CLL patients with isolated del(13q). We used CGH+SNP microarrays in order to understand the cause of this clinical heterogeneity. We detected del(13q) in 28/30 CLL cases. The size of the deletion varied from 0.34 to 28.81 Mb, and there was no clinical effect of the deletion size. We found new prognostic markers, especially the gain of 16p13.3. These markers have statistically significant associations with short time to first treatment and advanced disease stage. Detecting both CNVs and LOH at the same time is an advantageous feature of aCGH+SNP. However, it is very challenging for the array analysis to detect mosaic anomalies. Therefore, it is very important to confirm the results by FISH. In our study, we detected approximately 9% mosaic del(13q) by microarray. In addition, the gain of 16p13.3 may affect the disease prognosis in CLL. However, additional studies with more patients are needed to confirm these results.

A pediatric BAL case with double Ph chromosomes and trisomy 5.

Biphenotypic acute leukemias (BAL) are known as a type of leukemia involving cells with myeloid and along with lymphoid origin, in which genomic changes are detected. It has been stated that the most common genomic changes in BAL are t(9;22) and the translocations of the 11q23 region, these anomalies cause poor prognostic effects. We detected trisomy 5 (+5) in addition to the double Ph chromosome in a case where we investigated the genomic changes using molecular and conventional cytogenetic methods. Bone marrow transplantation was planned due to the poor response to prednisone. According to the information we have obtained, our report will be the first article to discuss the aberrations found in addition to the Ph chromosome in BAL and the effect of these aberrations on prognosis. However, the double observation of the Ph chromosome, which has a poor prognostic effect, is expected to affect the prognosis more negatively, this case will contribute to the literature in terms of trisomy 5. We think that more case reports are needed to reveal the anomalies and their prognostic significance in BAL.

A new four-way complex translocation variant involving the t(8;5;21;4)(q21;q13,q22,q31) and the relocalization of AML1/ETO fusion gene.

In acute myeloid leukemia, t(8;21) detected with a frequency of 10% is associated with good prognosis. However, variant t(8;21) is observed in 4% of these cases, and although the prognostic effects of these variant translocations have not been clearly revealed, there are findings that they affect the prognosis poorly. Here, we report on a 39 years old man, detected 4-way varyant t(8;21) which include relocalization of RUNX1/RUNX1T1 fusion gene, and loss of Y chromosome. RT-PCR also confirmed RUNX1/RUNX1T1 fusion transcript. Additionally, D820G and N822K mutations on KIT gene and mut B on NMP1 gene were detected. A complete remission could not achieved after first chemotherapy treatment. Due to primary resistance and variant of t(8;21), stem cell transplantation was performed. The variant translocation we have reported is unique and also the case is the second case that was reported in the literature in terms of the relocation of the AML1/ETO fusion gene. Since c-KIT mutations and LOY were also observed, it is not possible to predict the prognosis. To highlight the importance of variant translocations and relocalization of fusion gene, more cytogenetic and molecular data are needed.

Which prognostic marker is responsible for the clinical heterogeneity in CLL with 13q deletion?

BACKGROUND: Deletion of 13q14 [del(13q)] is the most common cytogenetic change (50%) in chronic lymphoblastic leukemia (CLL), and it is a good prognostic factor if it is detected as a sole aberration by FISH. However, it is observed the clinical course of CLL cases with del(13q) are quite heterogeneous and the responsible for this clinical heterogeneity has not been established yet. Some investigators suggest type II deletion (include RB1 gene) is associated with more aggressive clinical course. Also, it is suggested that the deletion burden and the deletion type have a prognostic effect. In this study, we aimed to investigate the effect of RB1 gene deletion, deletion burden and deletion type on overall survival (OS), disease stage and time to first treatment (TTFT) in patients with isolated del(3q). Sixty eight cases, detected isolated del(13q) were included in the study. Also, RB1 deletion was analyzed from peripheral blood of them using FISH. RESULTS: RB1 deletion was detected in 41% of patients, but there was no statistically significant difference between RB1 deletion and TTFT, stage and OS (p > 0.05). At same time, statistically significant difference was detected between high del(13q) (> 80%) and TTFT (p < 0.05). CONCLUSION: The statistical analysis of our data regarding to the association between RB1 deletion and deletion type, TTFT, disease stage, and OS has not confirmed type II deletion or biallelic deletion cause poor prognosis. However, our data supports the deletion burden has a prognostic effect. More studies are needed to elucidate the cause of the clinical heterogeneity of CLL cases with del(13q).