Standard management of patients with chronic myeloid leukemia

On the representation of cells in bone marrow pathology by a scalar field: propagation through serial sections, co-localization and spatial interaction analysis

BACKGROUND

Immunohistochemical analysis of cellular interactions in the bone marrow in situ is demanding, due to its heterogeneous cellular composition, the poor delineation and overlap of functional compartments and highly complex immunophenotypes of several cell populations (e.g. regulatory T-cells) that require immunohistochemical marker sets for unambiguous characterization. To overcome these difficulties, we herein present an approach to describe objects (e.g. cells, bone trabeculae) by a scalar field that can be propagated through registered images of serial histological sections.

METHODS

The transformation of objects within images (e.g. cells) to a scalar field was performed by convolution of the object's centroids with differently formed radial basis function (e.g. for direct or indirect spatial interaction). On the basis of such a scalar field, a summation field described distributed objects within an image.

RESULTS

After image registration i) colocalization analysis could be performed on basis scalar field, which is propagated through registered images, and - due to the shape of the field - were barely prone to matching errors and morphological changes by different cutting levels; ii) furthermore, depending on the field shape the colocalization measurements could also quantify spatial interaction (e.g. direct or paracrine cellular contact); ii) the field-overlap, which represents the spatial distance, of different objects (e.g. two cells) could be calculated by the histogram intersection.

CONCLUSIONS

The description of objects (e.g. cells, cell clusters, bone trabeculae etc.) as a field offers several possibilities: First, co-localization of different markers (e.g. by immunohistochemical staining) in serial sections can be performed in an automatic, objective and quantifiable way. In contrast to multicolour staining (e.g. 10-colour immunofluorescence) the financial and technical requirements are fairly minor. Second, the approach allows searching for different types of spatial interactions (e.g. direct and indirect cellular interaction) between objects by taking field shape into account (e.g. thin vs. broad). Third, by describing spatially distributed groups of objects as summation field, it gives cluster definition that relies rather on the bare object distance than on the modelled spatial cellular interaction.

Characterization and targeting of neoplastic stem cells in Ph+ chronic myeloid leukemia

Chronic myeloid leukemia (CML) is a myeloproliferative neoplasm characterized by the presence of an oncogenic fusion gene, BCR–ABL1. This fusion gene produces a cytoplasmic protein with tyrosine kinase activity that acts as a main driver of oncogenesis and abnormal proliferation of myeloid cells in CML. Targeted therapy with BCR–ABL1 tyrosine kinase inhibitors (TKIs) such as imatinib is followed by long-term responses in most patients. However, despite continuous treatment, relapses occur, suggesting the presence of TKI-resistant neoplastic stem cells in these patients. Here, we discuss potential mechanisms and signaling molecules involved in the prosurvival and self-renewal capacity of CML neoplastic stem cells as well as antigens expressed by these cells. Several of these signaling molecules and cell surface antigens may serve as potential targets of therapy and their use may overcome TKI resistance in CML in the future.

Genotypic and phenotypic classification of cancer: How should the impact of the two diagnostic approaches best be balanced?

Neoplastic tumors are traditionally named based on their differentiation (i.e., which normal cells and tissues they resemble) and bodily site. In recent years, knowledge about the genetic basis of tumorigenesis has grown rapidly, and the new information has in several instances been incorporated into the very definition of cancerous entities. The proper contribution of the diseases' phenotype and genotype to what they are called and how they are delineated from one another has rarely been subjected to explicit reasoning, however, nor is it often made clear whether existing naming practices are founded on ontological or utilitarian grounds. We look at several examples of how the new cytogenetic and molecular genetic understanding of tumorigenesis has impacted oncological nomenclature in a significant manner, but also at counterexamples where no similar change has taken place. In all likelihood, more and more neoplastic diseases will in the future be defined and named based on their pathogenesis rather than their phenotype, not least because effective and specific drug therapies directed against the molecular change at the very heart of oncogenesis will increasingly become available. The fact that this shift in emphasis is primarily guided by utilitarian considerations rather than any perception of acquired genetic changes as somehow being more ontologically "profound" or "important" in tumorigenesis, is as it should be; both the phenotype and the genotype of tumors are key parameters across most of oncology and are likely to be retained as the basis of coexisting disease classifications for as long as we can foresee.