Ask the experts - organoids for oncology studies

In the first post from our "Ask the experts" series we have answered the most commonly asked questions around the applications of HUB Organoids to viral infection studies. Here we discuss how they are contributing to our understanding of cancer biology and revolutionizing oncology drug development

Drs. Robert Vries, Sylvia Boj from HUB and Dr. Ryan Conder from our partner STEMCELL Technologies answer questions about organoids in oncology studies.

ORGANOIDS IN CANCER

How are organoids being applied to study cancer? What types of cancer can be modeled with organoids?

Patient-derived tumor organoids can be generated from most carcinomas and are commonly generated from colon, breast, lung, pancreas, ovarian, head, neck, and bladder tumors. These organoids can be expanded in culture, banked, or used in molecular applications, including genomics, transcriptomics and proteomics. Recent studies have shown differences in efficacy of drugs tested in 2D- versus 3D-cell cultures. Patient-derived tumor organoids can serve as a powerful in vitro system for drug screening and development as they represent the in vivo tumor more faithfully than immortalized cell lines.

How are tumor-derived organoids established? What considerations should I make when trying to establish tumor-derived organoids?

Tumor-derived organoids can be established using the same or a similar approach to organoids derived from normal/healthy tissue: organoids are established by isolating cells from tumor biopsies or from resected tissue and resuspending these cells in extracellular matrix (ECM) such as Matrigel^® or Cultrex^®. Organoids spontaneously self-organize from the resuspended tumor cells, with medium changes performed every 2-3 days and the culture passages performed every 7-10 days. It is important to use a ROCK inhibitor during the initial culture to avoid single cells entering anoikis.

Can organoids be established from circulating tumor cells? How can I use organoids to expand rare cancer cell types?

Organoid cultures have been established from resected tissue, core needle biopsies, and fine needle biopsies, therefore, researchers should be able to establish organoid cultures from liquid biopsies as well. Important factors that can impact the success of establishing these cultures are tumor cell content and the proliferative capacity of the tumor cells themselves. Organoid culture media designed for expanding healthy adult stem cells is generally amenable to culturing tumor-derived organoids and is non-selective, allowing for growth of rare cancer cell types.

How are organoids being used to develop new cancer therapies? How do treatments like radiation or other commonly used treatment strategies affect organoid integrity?

Organoids have been shown to accurately predict the response to treatment in a variety of cancer- and tumor-types (Vlachogiannis et al. 2018, Sachs et al. 2018, Berkers et al., 2019, Driehuis et al. 2019, Yao   2020). This makes patient-derived organoids (PDOs) a very powerful preclinical platform for drug screening and drug development in a human- or even patient-specific context. Multiple groups have used PDOs in large screens and have shown high predictivity of patient response to treatment with typical study endpoint being inhibition of proliferation or organoid death. However, it should be noted that the response may vary with treatment type, dosage, organoid type and depending on tumor donor.

How have organoids been used in immuno-oncology studies? What implications does this have for the potential of applications in precision medicine (eg. endocytosis assays to study immunoconjugate-mediated receptor internalization)?

Organoids have increasingly been adopted by the immuno-oncology field as a way to study the interaction of the immune system with epithelial tumors. However robust systems to enable tumor organoid-immune cell co-culture are still in development. Recent advances using leukocytes and T cells to examine retention, activation, and organoid cytolysis have shown that organoids are able to model the interactions observed in vivo. This has enabled researchers to effectively evaluate the cytotoxicity of a variety of antibody-drug-conjugates (e.g. trastuzumab, emtansine, neratinib) in vitro.

How can organoids be co-cultured with other cell types to better recapitulate the tumor microenvironment (eg. co-culture with hematopoietic cell types)?

Co-culturing organoids with other cell types is a technical challenge currently being addressed by the field. To recapitulate the tumor microenvironment in vitro, organoid culture conditions need to be optimized to allow growth of cancer cells as well as endogenous immune and other non-epithelial cells from patient tumor resections. However, current patient-derived organoid cultures only allow for the expansion of the epithelial compartment of the tumor. One strategy to recapitulate additional cellular diversity is expanding each desired cell-type independently until sufficient material is available for performing your assay then co-culturing these different cell fractions with organoids. Protocols that preserve the cellular diversity found in original patient biopsies for prolonged culture periods are currently under development. For example, Neal et al. (Cell, 2018) integrated epithelial and stromal compartments that allowed preservation of hematopoietic cell types.