A tumor mass does not consist of merely cancerous cells but also the tightly surrounding tumor microenvironment (TME), made up of both the non-cellular extracellular matrix (ECM) and various types of stromal cells. Though chemotherapy resistance is often attributed to tumor heterogeneity, cancer progression and malignancy is also profoundly influenced by its interaction with the surrounding TME. Residing hepatic stellate cells (HSC) in the liver are considered a major component of a liver TME because they transdifferentiate into highly proliferative and motile myofibroblasts that are associated with desmoplasia and tumor growth. HSC activation can occur in response to various cytokines, such as TGF-ß, from either a neighboring cell in response to an injury or from cancerous cells within the tissue. Myofibroblastic HSCs are responsible for the major changes that occur in the liver ECM associated with an aggressive TME via two mechanisms, the deposition of new ECM components and the physical remodeling of the preexisting ECM. A healthy, balanced TME is thought to result in a less aggressive, more vulnerable cancer while a more remodeled, unbalanced TME that consists of activated HSCs result in a more aggressive and less responsive cancer to chemotherapy.

In order to test this relationship between the TME architecture and cancer cell malignancy as well as chemoresistance, we have developed a 3-dimensional organoid model that can assess the effect of a remodeled TME on a cancer spheroid. Our lab has published the general organoid system that we utilize here; in short, we embedded a colorectal cancer cell line (HCT116) spheroid into an organoid consisting of HSCs (LX2) and collagen type 1. We then activated the LX2s to become myofibroblastic with exogenous TGF-ß causing excessive deposition and remodeling of collagen around the cancer spheroid. The remodeled TME that resulted from TGF-ß-mediated activation was quantified by analyzing the stiffness of the organoid that surrounds the spheroid as well as the in-depth, computational image analysis of the collagen fibers via CT-FIRE.

Our compression data, measured rheologically, revealed TGF-ß-mediated activation of the HSCs resulted in a stiffening of the organoid around the tumor spheroid. Results from the Picrosirus Red staining revealed the more remodeled organoid, containing activated HSCs, produced longer, wider, and more aligned characteristics around the spheroid. Our immunohistochemistry data indicated that the remodeled TME inhibits colon cancer cell growth and migration within the organoid. This inhibited proliferation, in combination with the physical collagen barrier in the activated TME, is thought to have a large effect on the ability for a chemotherapy to successfully penetrate and induce cytotoxic effects on the cancer cells. Collectively, the ability to manipulate the tumor organoids' TME towards fibrosis enables us to predict chemotherapy response based on TME properties and not solely cancer cells in isolation.

Citation Format: Anthony Dominijanni. Modeling the tumor microenvironment architecture of metastatic colorectal cancer in 3D organoids [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3999.