Assessing Measurable Residual Disease in Chronic Myeloid Leukemia. BCR-ABL1 IS in the Avant-Garde of Molecular Hematology

Association of pre-treatment bone marrow morphology and achievement of BCR-ABL1 transcript milestones in CML

Chronic myeloid leukemia (CML) is characterized by the fusion gene BCR-ABL1 which encodes aberrantly functioning tyrosine kinase. Treatment with tyrosine kinase inhibitors (TKI) is a landmark of CML management and the main goal is to achieve major molecular response (MMR) which is defined as BCR-ABL1^IS ≤ 0.1 % at 12 months of therapy. The aim of this study is to analyze histologic features of bone marrow (BM) in CML patients at the time of diagnosis and compare it to the level of BCR-ABL1^IS transcript at 3 (BCR-ABL1^IS ≤10 % early molecular response; EMR) and 12 months (MMR) as well as to so called molecularly undetectable leukemia (MUL) to see weather bone marrow morphology can be of value in predicting achievement molecular response milestones. Thirty-two bone marrow biopsies of CML patients, prior TKI therapy, were re-evaluated and CD34 immunohistochemistry was performed to examine microvessel density (MVD) and microvessel area (MVA) and subsequently compared it to the level of BCR-ABL1^IS transcript. This study showed statistically significant association between BM hypercellularity and EMR (p = 0.048) and MUL (p = 0.034), peri-trabecular adipocyte distribution and EMR and MUL (p = 0.027 and p = 0.011, respectively), MMR and bone marrow fibrosis (p = 0.029), loose megakaryocyte clustering and EMR and MUL (p = 0.004 and p = 0.018, respectively), absence of naked nuclei and MUL (p = 0.033) but there was no statistically significant association with vascular parameters. These results suggest that some bone marrow morphologic features prior TKI therapy might be indicators of favorable molecular response.

COVID-19 Impact on Chronic Myeloid Leukemia Patients

(1) Background: Chronic myeloid leukemia (CML) is a blood dyscrasia that accounts for about 20% of all leukemia cases. Tyrosine kinase inhibitors (TKIs) are used as first line treatment of CML. The 2019 SARS-CoV-2 outbreak raised new concerns for CML patients, such as whether CML increases the risk of contracting COVID-19, whether TKIs increase that risk, whether these drugs are safe to use during the infection, and whether any other hematologic parameters influence infection outcomes. (2) Methods: In our study we addressed these intriguing questions by using a retrospective analysis of 51 CML patients treated at the Ion Chiricuta Cancer Center, Cluj-Napoca, Romania. Furthermore, we investigated the effects of currently approved COVID-19 vaccines in our CML patients treated with tyrosine kinase inhibitors. (3) Results: Our results have shown that hemoglobin level upon diagnosis of CML has been the only hematologic parameter correlated to the risk of contracting COVID-19 in our CML patients. (4) Conclusions: TKI treatment did not negatively influence COVID-19 risk or the response to the vaccine in our patients. The safety profile of the currently approved COVID-19 vaccines was similar to that of the general population.

Allostery: Allosteric Cancer Drivers and Innovative Allosteric Drugs

Here, we discuss the principles of allosteric activating mutations, propagation downstream of the signals that they prompt, and allosteric drugs, with examples from the Ras signaling network. We focus on Abl kinase where mutations shift the landscape toward the active, imatinib binding-incompetent conformation, likely resulting in the high affinity ATP outcompeting drug binding. Recent pharmacological innovation extends to allosteric inhibitor (GNF-5)-linked PROTAC, targeting Bcr-Abl1 myristoylation site, and broadly, allosteric heterobifunctional degraders that destroy targets, rather than inhibiting them. Designed chemical linkers in bifunctional degraders can connect the allosteric ligand that binds the target protein and the E3 ubiquitin ligase warhead anchor. The physical properties and favored conformational state of the engineered linker can precisely coordinate the distance and orientation between the target and the recruited E3. Allosteric PROTACs, noncompetitive molecular glues, and bitopic ligands, with covalent links of allosteric ligands and orthosteric warheads, increase the effective local concentration of productively oriented and placed ligands. Through covalent chemical or peptide linkers, allosteric drugs can collaborate with competitive drugs, degrader anchors, or other molecules of choice, driving innovative drug discovery.

Clinical relevance of extracellular vesicles in hematological neoplasms: from liquid biopsy to cell biopsy

In the era of precision medicine, liquid biopsy is becoming increasingly important in oncology. It consists in the isolation and analysis of tumor-derived biomarkers, including extracellular vesicles (EVs), in body fluids. EVs are lipid bilayer-enclosed particles, heterogeneous in size and molecular composition, released from both normal and neoplastic cells. In tumor context, EVs are valuable carriers of cancer information; in fact, their amount, phenotype and molecular cargo, including proteins, lipids, metabolites and nucleic acids, mirror nature and origin of parental cells rendering EVs appealing candidates as novel biomarkers. Translation of these new potential diagnostic tools into clinical practice could deeply revolutionize the cancer field mainly for solid tumors but for hematological neoplasms, too.

Standardization of BCR-ABL1 p210 Monitoring: From Nested to Digital PCR

The introduction of tyrosine kinase inhibitors in 2001 as a targeted anticancer therapy has significantly improved the quality of life and survival of patients with chronic myeloid leukemia. At the same time, with the introduction of tyrosine kinase inhibitors, the need for precise monitoring of the molecular response to therapy has emerged. Starting with a qualitative polymerase chain reaction, followed by the introduction of a quantitative polymerase chain reaction to determine the exact quantity of the transcript of interest-p210 BCR-ABL1, molecular monitoring in patients with chronic myeloid leukemia was internationally standardized. This enabled precise monitoring of the therapeutic response, unification of therapeutic protocols, and comparison of results between different laboratories. This review aims to summarize the steps in the diagnosis and molecular monitoring of p210 BCR-ABL1, as well as to consider the possible future application of a more sophisticated method such as digital polymerase chain reaction.