Implication of BRCA1/2 germline variants for childhood AML biology and treatment.
Professor Richard D’Andrea
University of South Australia
We have uncovered a novel mechanism associated with development of childhood AML, an aggressive childhood malignancy. Our studies suggest that a significant percentage of childhood AML patients will benefit from tailored therapy with approved clinical agents. To test this we propose a number of experiments using AML patient samples.
Professor Richard D’Andrea, Professor Thomas Gonda, Dr Andrew Moore.
Our collaborative studies have suggested that rare-inherited mutations in well-known breast cancer risk genes may contribute to an increased likelihood of developing AML in childhood, and that these may be particularly important in children with Down’s Syndrome for whom development of AML is a recognised risk. AML in children is rare and thus our results are based on a small group of Australian childhood AML patients. Given the significance of these findings it is critical that we confirm this association and we recently we have been successful in obtaining approval through the National Cancer Institute (USA), to access childhood AML data generated frorr’I a large US genetic study. Confirmation of our findings in this group will mean that genetic counselling could be provided to at-risk families carrying these rare mutations to address potential ways to reduce risk such as reducing exposure to certain toxic chemicals during pregnancy or childhood. This would also justify genetic screening of children with Down’s Syndrome and increased monitoring when these mutations are detected. In parallel to these genetic studies we are performing experiments to test responses of childhood AML samples to a drug which is already approved for use in other cancers where these same rare mutations have been detected.
The most striking observation from our initial study was the frequency of samples carrying damaging mutations in the two well-described breast cancer associated genes BRCAl and BRCA2. These were mostly inherited mutations suggesting ,that such mutations may have an unrecognised role in increasing risk of childhood AML (as well as their known role as pre-disposition genes for breast cancer and some other childhood cancers). The increased frequency of these mutations in the samples with the classical Down’s Syndrome (DS) chromosomal abnormality (trisomy-21) also suggested that presence of these mutations may represent a vitally important risk factor for OS AML patients.
Key outcomes to data are:
- Successful application to obtain and analyse the childhood AML data generated by the Therapeutically Applicable Research to Generate Effective Treatments (TARGET) study.
An application, outlining our preliminary data, was approved through the National Cancer Institute (USA), allowing us access to childhood AML data generated by the TARGET study. This unique data-set includes 50 AML patient samples and was generated as part of a multi-Centre US cancer genetics study. We have now downloaded the TARGET AML data to a secure server at our University and we using our in-house computational approaches to identify the rare mutations in BRACl/2 and related genes. This analysis using a group of independent childhood AML samples will provide important additional data on the risk of childhood AML associated with these rare mutations. These results will be correlated to the clinical characteristics that we have also acquired as part of our agreement with the TARGET/NCI, and will also be compared to our own data. Reproducing our findings in this independent patient group will strongly support our hypothesise that there is a slight reduction in the DNA and chromosomal repair capacity in cells from children who inherit one of these mutations, and that this may be responsible for increased likelihood of developing AML. Together with our initial analysis, this study is critical for developing better genetic counselling of families known to carry mutations in DNA repair genes such as BRCA1/2, and patients with Down’s Syndrome. Counselling will be able to address potential ways to reduce risk, such as reducing exposure to certain toxic chemicals during pregnancy or childhood, and will justify screening and increased monitoring of children with Down’s Syndrome where these mutations are detected.
- Optimisation and testing of effects of rare BRCAl and AML mutations, and development of assays for analysis of patient sample responses
To further characterise the rare BRCAl ard BRCA2 mutations that we detected in our patient group (from Dr Andrew Moore, Qld), we first used an independent DNA test to detect the presence of the mutations in separate patient samples, and confirmed that they are inherited mutations. To investigate the function of a number of these very rare BRCA1/2 mutations, which have known association with cancer, we have used recombinant DNA technology to introduce the specific mutations into the BRCAl and BRCA2 genes. We will now introduce the mutated genes (or their normal counterparts) into cells in culture so that we can measure changes in the effectiveness of how the cells cope with induced damage to DNA (either from toxins, medications, or from stress growth conditions). The assay required to measure these cell responses have been optimised in the laboratory. Work continues to test potential therapies tailored for patients with these rare BRCAl and BRCA2 mutations. We have optimised conditions for culturing samples from AML patients in the laboratory, and have performed preliminary experiments to assay responses to a drug (olaparib) which is approved for clinical use in other cancers where these rare BRCAl and BRCA2 mutations have been detected. The next step will be to test the effectiveness of this drug (alone or in combination with chemotherapy) in killing cells from childhood AML samples.
- “Investigating rare pathogenic mutations of the extended Fanconi Anaemia DNA repair pathway in Acute Myeloid Leukaemia”, PhD thesis University of Adelaide, Kyaw Ze Ya Maung
- “BRCAl/2 mutations in childhood AML”,Maung KZY et al, manuscript in preparation for Leukemia
“Regulation and targeting of DNA repair in AML”,Invited seminar, Hunter Medical Research Institute and University of Newcastle,Newcastle, Sept 21 2018.