Genetic Variants of ABC and SLC Transporter Genes and Chronic Myeloid Leukaemia: Impact on Susceptibility and Prognosis.

Solute carrier (SLC) and ATP-binding cassette (ABC) transporters comprise a variety of proteins expressed on cell membranes responsible for intrusion or extrusion of substrates, respectively, including nutrients, xenobiotics, and chemotherapeutic agents. These transporters mediate the cellular disposition of tyrosine kinase inhibitors (TKIs), and their genetic variants could affect its function, potentially predisposing patients to chronic myeloid leukaemia (CML) and modulating treatment response. We explored the impact of genetic variability (single nucleotide variants-SNVs) of drug transporter genes (ABCB1, ABCG2, SLC22A1, and SLC22A5) on CML susceptibility, drug response, and BCR-ABL1 mutation status. We genotyped 10 SNVs by tetra-primers-AMRS-PCR in 198 CML patients and 404 controls, and assessed their role in CML susceptibility and prognosis. We identified five SNVs associated with CML predisposition, with some variants increasing disease risk, including TT genotype ABCB1 (rs1045642), and others showing a protective effect (GG genotype SLC22A5 rs274558). We also observed different haplotypes and genotypic profiles associated with CML predisposition. Relating to drug response impact, we found that CML patients with the CC genotype (rs2231142 ABCG2) had an increased risk of TKI resistance (six-fold). Additionally, CML patients carrying the CG genotype (rs683369 SLC22A1) presented a 4.54-fold higher risk of BCR-ABL1 mutations. Our results suggest that drug transporters' SNVs might be involved in CML susceptibility and TKI response, and predict the risk of BCR-ABL1 mutations, highlighting the impact that SNVs could have in therapeutic selection.

Standardization of molecular monitoring of CML: results and recommendations from the European treatment and outcome study.

Standardized monitoring of BCR::ABL1 mRNA levels is essential for the management of chronic myeloid leukemia (CML) patients. From 2016 to 2021 the European Treatment and Outcome Study for CML (EUTOS) explored the use of secondary, lyophilized cell-based BCR::ABL1 reference panels traceable to the World Health Organization primary reference material to standardize and validate local laboratory tests. Panels were used to assign and validate conversion factors (CFs) to the International Scale and assess the ability of laboratories to assess deep molecular response (DMR). The study also explored aspects of internal quality control. The percentage of EUTOS reference laboratories (n = 50) with CFs validated as optimal or satisfactory increased from 67.5% to 97.6% and 36.4% to 91.7% for ABL1 and GUSB, respectively, during the study period and 98% of laboratories were able to detect MR4.5 in most samples. Laboratories with unvalidated CFs had a higher coefficient of variation for BCR::ABL1IS and some laboratories had a limit of blank greater than zero which could affect the accurate reporting of DMR. Our study indicates that secondary reference panels can be used effectively to obtain and validate CFs in a manner equivalent to sample exchange and can also be used to monitor additional aspects of quality assurance.

[Mechanisms of resistance to BCR-ABL kinase inhibitors]. / Mecanismos de resistência aos inibidores da tirosina cinase BCR-ABL.

Since the introduction of imatinib mesylate for the treatment of chronic myeloid leukaemia, impressive clinical responses were observed in the majority of patients in chronic phase. However, not all patients experience an optimal response to imatinib mesylate or even to the more potent, second generation tyrosine kinase inhibitors. Furthermore, responses are not sustained in a number of patients, and it is yet unclear whether the inhibitors can be safely discontinued in patients who achieve long-term remission. The emergence of resistance to second generation tyrosine kinase inhibitors has become a significant problem that led to extensive studies on the causal mechanisms. This review will describe our current state of knowledge on why and how chronic myeloid leukaemia cells can develop resistance to second generation tyrosine kinase inhibitors.

Os doentes com leucemia mielóide crónica em fase crónica, tratados com imatinib mesilato obtêm na maioria dos casos uma respostaclínica. Contudo, nem todos atingem uma resposta óptima ao imatinib mesilato, ou sequer aos mais potentes inibidores da tirosina cinase de segunda geração. Além disso, algumas respostas não são duradouras e ainda não é claro se os inibidores podem ser interrompidos em doentes em remissão prolongada. Os mecanismos de resistência aos inibidores da tirosina cinase de segunda geraçãotornaram-se objecto de numerosos estudos. Esta revisão descreve o conhecimento actual sobre como e porquê as células de leucemiamielóide crónica podem desenvolver resistência aos inibidores da tirosina cinase de segunda geração.

Mechanisms of resistance to BCR-ABL kinase inhibitors.

Since the introduction of imatinib mesylate (IM) for the treatment of chronic myeloid leukemia (CML), impressive clinical responses have been observed in the majority of patients in chronic phase. However, not all patients experience an optimal response to IM or even to the more potent, second-generation tyrosine kinase inhibitors (TKIs). Furthermore, responses are not sustained in a number of patients, and it is yet unclear whether the inhibitors can be safely discontinued in patients who achieve long-term remission. The emergence of resistance to TKIs has become a significant problem that has led to extensive studies on the causal mechanisms. This review describes our current state of knowledge on why and how CML cells can develop resistance to TKIs.

Detection of human mammaglobin mRNA in serial peripheral blood samples from patients with non-metastatic breast cancer is not predictive of disease recurrence.

INTRODUCTION: Human mammaglobin (hMAM) mRNA is a sensitive and specific marker of breast cancer cells. We evaluated if hMAM mRNA detection in serial peripheral blood samples from non-metastatic breast cancer patients predicts for disease recurrence. METHODS: Patients scheduled for adjuvant or neoadjuvant chemotherapy were eligible. Serial blood samples were collected up to 5 years, the first before (neo)adjuvant chemotherapy. hMAM gene expression was analysed by RT-PCR. Specificity was evaluated in blood samples from healthy volunteers. A total of 321 patients were included. RESULTS: The incidence of pre-chemotherapy hMAM-positive samples was similar in patients who latter experienced cancer recurrence (22.4%) and those who remained disease-free (17.9%; P = 0.46). Similarly, the mean number of positive follow-up samples was similar in both groups (0.15 +/- 0.22 and 0.13 +/- 013; P = 0.29). Furthermore, there was no difference in disease-free (P = 0.63) or overall survival (P = 0.57) in patients with and without positive baseline samples or between patients whose follow-up samples were always hMAM negative and those with at least one positive sample. Multivariate survival analysis confirmed that hMAM mRNA detection before or after (neo)adjuvant chemotherapy was not predictive of recurrence. DISCUSSION: There is no evidence that hMAM mRNA detection at diagnosis or during follow-up predicts for breast cancer recurrence.