Somatic genetic testing in haematological malignancies: chronic myeloid leukaemia

• Autor(a) principal: Gonçalves, Cátia Monteiro
• Data de Publicação: 2023
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/39250
• topic: Chronic myeloide leukaemia; Haemato-oncology; Molecular biology; Cytogenetic; Karyotype; Fish; Sanger sequencing; PCR

Haematology-oncology is the medical specialty that combines haematology with oncology. As the name implies, it is responsible for cancers that interfere with the production and functioning of blood cells. Cancer is a disease caused by genetic changes and/or dysregulation. Gradually, increased understanding and research into the genetics of neoplasms has changed the oncology landscape to adapt to the new genetic data. Chronic Myeloid Leukaemia (CML) is a myeloproliferative neoplasm, being the most common (corresponding to about 15-20% of all leukaemias). CML was the first leukaemia to be described and it was the first neoplasm in which an associated chromosomal abnormality, the Philadelphia chromosome (Ph), was identified. This is the product of a reciprocal translocation between chromosomes 9 and 22, t(9;22)(q34.1;q11.2), which leads in a 22 chromosome the fusion gene BCR (located on 22q11.2), with the ABL1 gene (located on 9q34.1). The resulting BCR::ABL1 chimeric gene encodes a fusion protein, BCR::ABL1, with constitutively active tyrosine kinase activity. Currently, the diagnosis of this disease is carried out, mostly, in an asymptomatic phase, due to the routine analysis. The typical finding on hemogram that leads to suspicion of CML is a leucocytosis, namely neutrophilia. According to the classifications of neoplasms currently in vigour, CML is a myeloproliferative neoplasm with BCR::ABL1 fusion gene. Thus, after the diagnosis of myeloproliferative neoplasia, it is genetics that will confirm the diagnosis of CML. The objectives for this internship are to gain experience in the cytogenetics and molecular genetics laboratory, as well as to understand the carcinogenesis and pathophysiology of CML. In order to fulfil the objectives, I carried out the various analyses in the cytogenetics laboratory and in the molecular genetics’ laboratory, always focusing on haematological neoplasms, in particular CML. Confirmation of the diagnosis of CML is carried out, as a rule, using two techniques, namely, qualitative PCR and karyotype. The two techniques together will confirm or reject the CML diagnosis. However, some patients have less frequent transcripts, or cryptic changes by karyotype. In such cases, it is necessary to use another technique, namely fluorescent in situ hybridization (FISH). Due to advances in genetics and the understanding of the pathophysiology of CML, it was possible to develop target drugs for this disease, the tyrosine kinase inhibitors (TKIs). These drugs caused that the natural history of this disease was entirely revolutionized.It caused an increase in the quality of life of patients and in their average life expectancy. Genetics, in addition to being important for the development of targeted therapy, is crucial for the diagnosis and for the follow-up of these patients. From the moment the diagnosis of CML is confirmed, patients are monitored by quantitative PCR, or in cases of less frequent transcripts, by FISH. It is through genetic evaluation that it is possible to assess, more accurately, the response to TKIs and adherence to therapy. This internship allowed me, not only, to acquire laboratory skills in cytogenetics and molecular biology, but also give the notion that there are no perfect techniques and all are complementary to each other, and the most important thing is to know how to take advantage of each of them. It also allowed me to understand the enormous importance that genetics have in oncology.