Chronic Lymphocytic Leukemia (CLL) is one of the most widespread blood cancers in the Western countries and affects about 5 people per 100,000 inhabitants every year. Although a significant progress in research has been made in recent years, at the moment there is still no therapy to treat the disease, probably due to the still unclear molecular mechanisms behind it.

This is why Dr. Cristina Scielzo, group leader of Malignant B cell biology and 3D modelling Unit Biology of malignant b-cells and 3D modeling at IRCCS Ospedale San Raffaele, together with her multidisciplinary research group, is working on a new experimental model of CLL, able to reproduce more faithfully in the laboratory what happens in our body.

"A major challenge in recent years has been to finalize effective experimental protocols to study how CLL cells behave in vitro, how they interact with the surrounding microenvironment and how they respond to drugs. The ultimate goal is to identify mechanisms that may soon become therapeutic targets for a disease that is still not treatable," explains Cristina Scielzo.

Underlining the importance of her research, Cristina Scielzo has recently received prestigious funding from the European Hematology Association (EHA) to create a multi-organ system in vitro of CLL that is more complex and closely related to reality.

 

Why a new experimental model is important

In CLL, cancer cells are not only circulating in the bloodstream but they also proliferate in lymphoid organs such as bone marrow, lymph nodes and spleen. Here they establish fundamental interactions with the surrounding microenvironment, which determine the development, progression and drug resistance of the disease.

"To study the mechanisms that occur in tissues, many experimental models have been used however so far they resulted to be partial or unreliable. In our three-dimensional model of the disease, tumor cells are not forced to a flat surface (in two dimensions) - as typical of laboratory plates - but extend in all dimensions in space, exactly as they do in reality," specifies Dr. Scielzo.

This innovative approach makes it possible to study in depth the interactions occurring between leukemic cells and the microenvironment, and to test new drugs in a much more physiological context than traditional 2D models.

 

The first results obtained

With this new three-dimensional model of the disease, researchers at San Raffaele were able to mimic the bone marrow by recreating the interactions between leukemic cells and stromal cells, both in the presence and absence of pharmacological agents. It was possible to keep the 3D microenvironment in culture thanks to a special device - a bioreactor working in microgravity - able to provide a suitable environment for cell growth.

"Some of the drugs used in the clinic to treat CLL act not by killing the diseased cells directly, but simply by moving them from the lymphoid tissues, from which they derive support, and forcing them to enter the peripheral bloodstream. Here they lose the direct contact with the tumor microenvironment and die.  Thanks to our experimental model we were able to study the mobilization effect of diseased cells from the tissues, which would have been impossible to evaluate in a traditional 2D culture model," continues Dr.Scielzo.

The results, recently published in the scientific journal Haematologica and obtained thanks to the support of AIRC (the Italian Association for Cancer Research), show that the drug does not act in the same way in all patient cells.

In particular, cells with active HS1 protein - previously identified by the same laboratory with prognostic value and involved in the migratory activity of the cells - are mobilized by the tissues with greater efficiency than those with HS1 in its inactive form. In this second case, in fact, the leukemic cells remain "hidden" in the lymphoid organs, proliferating and making the disease potentially more difficult to treat.

 

A starting point for future developments

Why aren't some cells mobilized? What is the reason for their resistance? There are still many questions that need to be answered, but thanks to the optimization of the 3D model of CLL, researchers at San Raffaele expect to be able to study soon some of the mechanisms that have not yet been investigated for technological limits.

"We know how drugs act in the bloodstream, but we don't really know what happens in the tissues: there we could find fundamental information to develop future therapeutic targets, not only for CLL but also for other types of leukemia or solid tumors. Moreover, the use of 3D models could represent a resource for personalized medicine advancement: by harvesting cells from patients and culturing them in three-dimensions, we could evaluate the evolving effectiveness of a given drug in the laboratory before using it", concludes Dr. Scielzo.

The new funding obtained by the EHA aims to recreate a multi-organ system in vitro much more complex than the current one, consisting of lymph nodes, bone marrow, peripheral blood and various microenvironment cells - from endothelium to immune system cells. The dynamic growth of the three-dimensional model will be made possible by a new type of bioreactor that will allow cells to move in space and drugs to interact with them.