4 research outputs found
Adenovirus DNA in Guthrie cards from children who develop acute lymphoblastic leukaemia (ALL)
Aims: The aim of this thesis was to increase understanding of how molecular processes influence
the development and risk assessment of childhood leukemia. Studies I and II investigates whether a
specific virus infection in utero could be involved in a “first hit” in leukemogenesis. Studies III and
IV examine whether alterations in protein expression from cell cycle regulating genes may predict
a relapse in children with myeloid malignancies undergoing hematopoietic stem cell
transplantation (HSCT).
Background: Genetic alterations, analyzed at time of diagnosis in children who develop leukemia,
have been traced back to neonatal dried blood spots (DBS). This suggests that the majority of
chromosome translocations occur in utero during fetal hematopoiesis, generating a “first hit”. A
“second hit” is then required to generate a leukemic clone. Today, experiments in vitro, animal
models, and clinical observations have revealed that several viruses are oncogenic and capable of
initiating a genetic alteration. Smith M postulated the theory that an in utero infection might be the
“first hit”, causing genetic aberrations that could later lead to the development of the leukemic
clone, which is supported by the early age of onset and space-time clustering data, based on time,
place of birth, and diagnosis.
Leukemia develops as a result of hematopoietic or lymphoid tissue with uncontrolled cell division.
Normally cell division is controlled by the cell cycle, the network of which is complex with
numerous regulating proteins both up and down stream, but also containing several feedback
loops. The important regulators of this process are tumor suppressor genes, essential for normal
cell proliferation and differentiation as well as for controlling DNA integrity. Errors in these genes
or their protein expression affect the ability of the cell to check for DNA damage, thus tumors may
occur. Proteins from these genes could serve as prognostic markers and predict relapse.
Methods: In studies I and II we investigated neonatal DBS by PCR for the presence of adenovirus
DNA (243 samples) and the three newly discovered polyomaviruses (50 samples) from children
who later developed leukemia but also from controls (486 and 100 samples respectively). In
studies III and IV we explored the expression of one (p53) respectively four (p53, p21, p16 and
PTEN) cell cycle regulating proteins in bone marrow at diagnosis as well as pre and post HSCT in
myeloid malignancies in children. We retrospectively collected clinical data and bone marrow
samples from 33 children diagnosed with chronic myeloid malignancies (MDS, JMML and CML),
34 children diagnosed with AML as well as 55 controls. The samples were prepared by tissue
micro array (TMA) as well as immunohistochemistry and examined for protein expression in a
light microscope.
Results: In study I we detected adenovirus DNA in only two patients who later developed
leukemia, but in none of the controls. In study II all the samples were negative for KIPyV, WUPyV
and MCPyV DNA in both patients and controls. In study III we found an overexpression of p53
protein at diagnosis that significantly predicted relapse after HSCT in children with rare chronic
myeloid malignancies. In study IV a significantly higher p53 expression was found in the relapse
compared to the non-relapse group at six months post HSCT in children with AML, suggesting
that p53 may be used as prognostic markers for predicting a relapse. In addition, the calculated cut
off level for p53 at diagnosis (study III) and at six months (study IV) post HSCT was
approximately 20%, which indicates that a p53 expression over 20% may predict relapse in
children with myeloid malignancies.
Conclusion: Although we did not find an association between adenoviruses or the three newly
discovered polyomaviruses and the development of childhood leukemia, a virus could still be
involved in this process; the virus may have escaped detection, other new viruses could be
involved or a virus could precipitate the “second hit”.
We suggest that evaluation of p53 protein expression may be used as a supplement to regular
prognostic markers both pre and post HSCT. To further evaluate this, a prospective multicenter
study has been started