T-cell acute lymphoblastic leukemia (T-ALL) accounts for 10%-15% of pediatric and 25% of adult ALL cases. The disease is critically associated to Notch signaling deregulation, since about 60% of T-ALL harbor activating NOTCH1 mutations and the vast majority of T-ALL patients displays increased expression and function of Notch3. Current treatments fail in 20-30% of T-ALL patients and Notch signaling may contribute to chemotherapy resistance, thus suggesting Notch inhibition as a targeted therapy strategy.
We and others previously reported that the development of T-ALL in mouse models is preceded by the appearence in periphery of CD4+CD8+ "preleukemic cells", which may mirror the disruption of normal intrathymic T cell differentiation, that in turn may represent the primum movens of T-ALL development, at least of the childhood disease. This proposal is designed to gain mechanistic and functional insights into the effects of Notch signaling deregulation in intrathymic T cell differentiation, which may lead to T-ALL development through the disruption of normal relationships between T cell precursors and the microenvironment. Our main goals are: i) to identify the mechanisms underlying the thymus egression of "pre-leukemic cells" and to follow their fate in the periphery in order to define a possible hierarchical colonization program; ii) to dissect their relationships with the different microenvironments, encountered during initiation, development and/or relapse of the disease. The dissection of cellular and molecular mechanisms, involved in the crosstalk between leukemia cells at different stages and microenvironment of different districts, may
help future research aimed to identify malignant niches where pre-leukemic cells may receive instructive cues for their maintenance, as leukemia initiating cells (i.e. cancer stem cells), or evolve from preleukemic to leukemic stages in the course of the disease, finally supporting the design of novel target therapy protocols.
The present proposal originates from the ETN proposal THYTOTALL, submitted to the H2020-MSCA-ITN-2018 Call. In that project Prof. Screpanti was the Coordinator and the network included high profile research and clinical groups from several academic and non academic institutions. As stated in Horizon 2020, objective of fundamental research is to acquire new knowledge and unveil complex processes, that in the future may have a practical application. In keeping with this, the main objective of THYTOTALL, was to dissect the mechanisms involved in the normal development of T lymphocytes and to correlate their possible deregulation to pathogenic aspects of T-cell leukemia development and progression. In this wide project, prof Screpanti, was the coordinator but also one of the partner involved in the complex experimental plan. Prof Screpanti's group, including prof. MP Felli, from the Department of Experimental Medicine and who participates to the present project, would have carried out specific tasks related to the intercellular relationships between lymphoma cells, at different stages of development of the disease, and stromal cells of different districts and to the study of the effect of Notch deregulation on these processes.
The understanding of such relationships represents a critical issue in the management of leukemias. Indeed, increasing evidence suggests that, similarly to what happens for cancer stem cells in solid tumors, extrinsic components (i.e. stromal or endothelial cells, chemokines, etc.) related to the microenvironment may play a pivotal role in allowing survival and drug resistance of leukemia cells. Thus, a better knowledge of the molecular and cellular mechanisms favoring T-ALL initiation, development and/or relapse through the relationships of leukemia cells with a specific microenvironment represents a challenging issue, with implications for the discovery of new therapy targets and the design of new personalized therapies.
Notably, although efficient chemotherapy protocols rendered T-ALL a curable cancer, 25-30% of children and up to 60% of adults bearing TALL still relapse, undergoing a poor prognosis.
To this regard the dissection of cellular and molecular mechanisms involved in the crosstalk between leukemia cells and microenvironments of different districts, possibly involved in the protection of tumor cells from immune surveillance (i.e. through the induction of T regulatory cells (Tregs) that would inhibit an effective anti-tumor immune response) or in sustaining therapy resistance, may help to identify new druggable targets.
In addition, the possibility to detect preleukemic cells circulating in peripheral blood in very early phases of the disease would offer the opportunity to undertake precocius bloking treatments, that would help in stopping or at least delaying the development of full-blown disease and preventing its dissemination in peripheral organs.
The in vivo experiments we propose here may be very helpful to follow the onset of T-ALL, which may be represented by the appearance of circulating preleukemic cells, and then its development and dissemination in peripheral organs, until the possible settlement of leukemia initiating cells in the Bone Marrow, where they can induce and exploit a protective microenvironment.
In addition, bioprinting-derived 3D tissue constructs can offer the possibility to recreate in vitro a tumor microenvironment, facilitating direct cell-cell interaction and triggering intercellular signaling and, by mimicking tumor structures found in vivo, would allow a great opportunity to understand crucial cancer mechanisms and to develop novel therapy approaches.
The respect of 3Rs (Reduction, Replacement and Refinement) in animal experimentation represents to date a challenging issue in research proposals.
The validation of the 3D co-culture system as a predictive model of in vivo responses to traditional and/or targeted T-ALL therapy, taking into account the bidirectional crosstalk between thymic or BM stroma and leukemia cells, would represent an additional improvement of science since it would help in reducing the xenotransplant experiments, thus the number of animals utilized to study cancer/microenvironment relationships. 3D co-culture would thus represent a promising alternative method to replace animal use.
Finally, the possibility to utilize both leukemia and stromal human cells in 3D co-culture systems may also increase the reliability of the bidirectional effects observed in both cell populations, resulting from the leukemia/stromal cells direct interaction, with respect to what may happen in human into mouse xenotransplants.