Multiple myeloma is an incurable cancer of the bone marrow; most patients develop resistance against first line therapy Velcade (bortezomib) sooner or later, which is a problem because few alternative drugs are available.
Part of the reason for this is that to date there have been no screening systems to allow scientists to study the effects of multiple myeloma drug candidates in a 3-D environment.
This may soon change according to European scientists who have grown miniature human myelomas in chicken eggs in a microenviroment that includes extracellular matrix compounds (ECM) and supportive stromal cells.
3D Multiple Myeloma Model
“We wanted to generate a natural microenviroment by combining 3-D co-culture in ECM matrix with in vivo growth conditions in chicken embryos,” said Gerold Untergasser at Innsbruck Medical University in Austria.
“The previous standard 2 D culture was not very successful for testing drugs on myeloma cells, because some drugs were not very efficient in co-culture conditions, due to the supportive function of stromal cells.”
Trial assays have been successful according to Untergasser, who said novel marine compounds synthesized by Spanish API firm Pharmamar “displayed a strong anti-myeloma and anti-angiogenic activity,” Untergasser said.
Tumours in eggs
The scientists approach is to cultivate tumour cells with human mensenchymal cells from the bone marrow and collagen in the shape of 3-D cell spheres, simulating tumours in bone marrow.
After removing the eggshells, the researchers transfer the cell spheres to the outer chorioallantoic membrane. This membrane provides a perfect base for growing miniature human tumours in a petri dish. It allows putative drugs to be added to see if they can kill myeloma cells.
This is not straightforward because the mensenchymal cells protect the tumor in the test system just as they do in patients. Cancer drugs have to overcome this protective shield.
“We tested already tested four different human myeloma clones and work on refining of the system by including bone-replacement material based on hydroxyapatite (calcium apatite) to provide an optimal substrate for myeloma cell growth of bone marrow aspirates of patients,” Untergasser explained.
The spheroids have a diameter of about 2 mm and their generation takes just 1 to 2 hrs. The preparation of eggs takes about one week before grafting of spheroids.
The group is working to improve the system for patients by constructing spheroids that more resemble the natural microenviroment of the human bone.
Asked what benefits this technique offers, Untergasser said it makes large-scale screening of compounds more feasible, offers easy handling and imaging of tumours and is less costly than immunocompromised mice that require special facilities.
Also the embryonic tissue of the chorioallantoic membrane of chicken is a perfect substrate for growth of myeloma cells, because is strongly vascularized and full of supportive growth factors.
The technique was developed as part of an EU project called OPTATIO and a video publication was released in the Journal of Visualized Experiments. The video is entitled “Establishment of a Human Multiple Myeloma Xenograft Model in the Chicken to Study Tumor Growth, Invasion and Angiogenesis.”
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