Tumor organoids are ex vivo three-dimensional (3D) organized cultures that are derived from fresh tumor tissue and provide cancer models. Tumor organoids recapitulate the biological key features of the original primary tumor1,2,3,4 and can be expanded for up to several months and cryopreserved, similar to conventional immortalized cell lines. Tumor organoids provide a biobank of patient-derived tumor models for translational/personalized medicine5 and represent an important advance in cancer cell biology systems/models. Patient-derived tumor organoids can be used as ex vivo models to predict the efficacy of (neo)adjuvant oncological/pharmacological therapies, for which cultures are established from fresh tumor tissue and drug sensitivity assays or pharmacotyping are performed on a patient-specific basis to identify effective agents for subsequent lines of therapy1,4. Furthermore, tumor organoids overcome the limitation of the availability of primary tumor tissue and, more importantly, provide an excellent alternative or complementary system to in vivo mouse models, such as patient-derived xenografts (PDX)2. The complexity of tumor organoids is increased if the primary tumor cells are combined with stromal cells that are found in the tumor microenvironment (TME), such as cancer-associated fibroblasts (CAFs), endothelial cells, and immune cells, which mimic the functioning and complex cellularity of the primary tumor. Tumor organoids have been established for many tumor types using standardized protocols6,7,8,9,10. Organoid propagation from different solid tumors, including colorectal and breast cancer tissue, is well-established and technically affordable11,12,13,14,15.
Surgical tumor resections or tumor biopsies provide primary tumor tissue specimens. Ideally, tumor tissue specimens should come from the center of the tumor mass or the invading edge of the tumor, as well as normal-looking tissue adjacent to the tumor. Compared to conventional 2D cultures, tumor organoids require several "add-ons", including a biological basement membrane (such as Matrigel, hydrogel, or a collagen-based scaffold), which mimics the extracellular TME, and a liquid growth medium that supplies specific nutrients and growth factors and supports cell proliferation and viability in culture16.
The most basic steps in primary cell culture are washing the tissue in saline solution to prevent contamination, mechanically cutting/digesting the tumor into small pieces of 1-3 mm3, and treatment with collagenase for the enzymatic digestion of the tissue. The digested mix is then filtered to remove large tissue fragments, resuspended in a biological basement membrane such as Matrigel, and plated as domes in low-attachment culture plates to enhance non-attachment growth. The basement membrane matrix domes are covered with liquid culture medium and supplemented with glutamine and antibiotics to avoid contamination, as well as with specific growth factors depending on the tissue type7,8,9,16,17. Other relevant cells present within the bulk tumor and the TME may also be isolated, such as cancer-associated fibroblasts (CAFs) and immune cells. This technique, which has recently been reviewed18, allows the establishment of co-cultures with different cell types to study the response to therapy in a more "realistic" tumor environment. Furthermore, cell-cell interactions and the interaction between tumor cells and components of the surrounding biological matrix can be studied.
The reported success rate of tumor organoid establishment using fresh tissue from biopsies or resected gastrointestinal tumor tissue is around 50%11, and the success rate from the latter is largely dependent on the tissue type and origin4, particularly the tumor grade and overall tumor cellularity. Three-dimensional tumor models have varying complexity, from simple unicellular aggregates to highly complex engineered models consisting of various cell types. The terminology used to describe 3D cultures in the literature is highly inconsistent19,20,21, as different terms such as spheroids, tumorspheres, and organoids are used, although the difference between them is unclear. As a clear consensus on the definition has not yet been reached, in this article, a tumor organoid is described as an organized tumor cell culture embedded into a biological basement membrane.
Herein, a validated protocol is reported for the establishment of tumor organoids from fresh tissue samples originating from fresh primary resected or PDX-derived pancreatic ductal adenocarcinoma (PDAC), and this protocol can be performed in most laboratories with basic tissue culture facilities. This protocol has been adapted from several state-of-the-art reported protocols that are currently used to establish tumor organoids or tumoroids from digestive tumor tissue from the groups of David Tuveson9, Hans Clevers8, and Aurel Perren7.
This protocol does not discuss how the fresh tissue is harvested. To obtain high-quality fresh human tumor tissue, it is important to have efficient coordination between the surgeons that harvest the tissue and the pathology department that extracts the tissue sample for organoid culture. Likewise, when using PDX as a fresh tissue source, efficient coordination with the person that harvests the tissue sample is also important. It is critical to obtain the tissue sample as quickly as possible (within 30-60 min from harvesting time) in order to maintain a high quality.