Next-generation cancer organoids

Abstract

Organotypic models of patient-specific tumours are revolutionizing our understanding of cancer heterogeneity and its implications for personalized medicine. These advancements are, in part, attributed to the ability of organoid models to stably preserve genetic, proteomic, morphological and pharmacotypic features of the parent tumour in vitro, while also offering unprecedented genomic and environmental manipulation. Despite recent innovations in organoid protocols, current techniques for cancer organoid culture are inherently uncontrolled and irreproducible, owing to several non-standardized facets including cancer tissue sources and subsequent processing, medium formulations, and animal-derived three-dimensional matrices. Given the potential for cancer organoids to accurately recapitulate the intra- and intertumoral biological heterogeneity associated with patient-specific cancers, eliminating the undesirable technical variability accompanying cancer organoid culture is necessary to establish reproducible platforms that accelerate translatable insights into patient care. Here we describe the current challenges and recent multidisciplinary advancements and opportunities for standardizing next-generation cancer organoid systems.

Fig. 1 |. Cancer organoids recapitulate defining characteristics of patient-specific tumour heterogeneity.

Each patient’s cancer presents a host of unique cellular and environmental characterist ics that contribute to the vast biological heterogeneity within and across tumours. Organoid models derived directly from human tumour tissue have been shown to accurately recapitulate this inherent intra- and intertumoral biological heterogeneity. Specifically, cancer organoids can recapitulate the extreme (epi)genetic and phenotypic diversity of distinct neoplastic cell subclones, as well as their collective tumour-specific morphological features. Cancer organoids also enable modelling of TME heterogeneity, including the presence and functions of non-neoplastic, TME cells, the signalling of niche-specific soluble factors and the altered composition of the ECM. As a result, cancer organoids are a promising tool to model patient-specific responses to anticancer therapies in the clinic.

Fig. 2 |. Current techniques for cancer organoid culture introduce technical variability into biologically heterogeneous cultures.

Protocols used throughout cancer organoid derivation and culture are non-standardized, which is detrimental to reproducibility and limits the ability to reliably represent the tumour’s inherent biological heterogeneity. a, Variable sources and methods of collecting human tumour tissue, as well as the protocols used for its downstream processing into 3D organoid cultures, lead to the formation of non-standardized organoid models that may only represent a subset of the patient’s cancer. b, The use of ill-defined and heterogeneous medium components for organoid cultures, including conditioned medium and animal-derived serum, directly inhibits the controlled presence of soluble cues and unpredictably alters organoid phenotype. c, 3D culture of cancer organoid samples within animal-derived ECMs is limited by substantial batch-to-batch variability and xenogenic contamination. These matrices also have a complex and ill-defined composition as well as overall poor tunability, which limits mechanistic studies of matrix influence on cancer biology.

Fig. 3 |. Patient-specific cancer organoid derivation is limited by non-standardized methods of tissue procurement and processing

a, Current methods of cancer organoid derivation. Several sources of tumour tissue from distinct stages of cancer progression, including primary tumours, circulating tumour cells and secondary metastatic lesions, have been collected to generate patient-specific cancer organoid models. Similarly, several subsequent tissue processing techniques, including tissue mincing, complete tissue dissociation and/or cell sorting, have also facilitated cancer organoid generation upon encapsulation in a 3D matrix. However, the variable implementation of these methods—each introducing its own sources of technical variability—has led to the formation of non-standardized cancer organoid cultures. b, Recent advancements in cancer organoid derivation. The comparison of cancer organoids derived from multiple tissue samples per patient and the introduction of cancer-associated TME cell types (left) has enabled an enhanced understanding of tumour cellular heterogeneity and the impact of heterotypic cell interactions on cancer cell biology. Additionally, advancements in cancer organoid culture platforms (right) have enabled environmental control of nutrient mass transport and overall standardization of organoid size and spatial organization.

Fig. 4 |. The ECM influences cancer organoid phenotype through several biochemical and mechanical interactions.

The ECM plays critical roles in driving cancer phenotype, disease progression and therapeutic response in vivo. 3D engineered matrices with tunable biochemical (for example, ligand presentation, soluble-factor sequestration) and mechanical (for example, matrix viscoelasticity, degradation, architecture, pore size) properties are poised to answer previously untestable hypotheses surrounding mechanisms of these important cancer–matrix interactions. Additionally, reciprocal interactions between the ECM and TME cells, such as fibroblasts and immune cells, can also be modelled using in vitro engineered matrices.

Fig. 5 |. Engineered matrices for standardizing cancer organoid models.

a, Compared with animal-derived matrices, engineered matrices offer high batch-to-batch reproducibility and enable standardization of cancer organoid formation and culture. b, Designer engineered matrices can be formulated to mimic patient- and disease-specific composition and structure of the native tumour ECM. c, High-throughput screening of tunable engineered matrices can provide insight into the roles of biochemical and mechanical matrix properties in cancer organoid biology.