Patient-derived cancer modeling for precision medicine in colorectal cancer: beyond the cancer cell line

Abstract

Since effective immunotherapeutic agents such as immune checkpoint blockade to treat cancer have emerged, the need for reliable preclinical cancer models that can evaluate and discover such drugs became stronger than ever before. The traditional preclinical cancer model using a cancer cell line has several limitations to recapitulate intra-tumor heterogeneity and in-vivo tumor activity including interactions between tumor-microenvironment. In this review, we will go over various preclinical cancer models recently discovered including patient-derived xenografts, humanized mice, organoids, organotypic-tumor spheroids, and organ-on-a-chip models. Moreover, we will discuss the future directions of preclinical cancer research.

Keywords: Patient-derived cancer models; humanized mice; organ-on-a-chip models; organoids; organotypic-tumor spheroids; patient-derived xenografts; preclinical cancer models.

Figure 1.

Preclinical study in the PDX model. (a) Tumor growth curve of colorectal cancer PDX treated with Irinotecan. (b) Weights of individual tumors from each group. Error bars, ± s.d. (n = 5 per group). (c) Mouse weight during treatment. Statistical analysis was performed using a one-way analysis of variance followed by the Newman–Keuls posttest. (d) Representative photographs of individual tumors from each group. Tumor volume and body weight were recorded at regular intervals until tumors reached approximately 1,000mm3. To compare the groups, Student’s t-test was performed, and the p-value was indicated as asterisk mark. (** P < .01, *** P < .001).

Figure 2.

Patient-derived organotypic tumor spheroids (OTS). (a) Phase-contrast imaging (4X, 10X) of OTS derived from the colorectal cancer patients. (b) Immunofluorescence staining of CD3 immune cells in patient-derived OTS. Fresh tumor samples were obtained from the Department of Surgery at Samsung Medical Center in accordance with protocols approved by the Institutional Review Board. For the establishment of PDOTS, fresh tumor specimens were received in media (DMEM or RPMI) on ice and minced in a 10 cm dish using sterile forceps and scalpel. The minced tumor was resuspended in high-glucose DMEM with 100 U mL−1 type IV collagenase (Life Technologies, Carlsbad, CA), and 125 mg/ml Dispase II (Life Technologies, Carlsbad, CA) for 30 min at 37°C. Following digestion, samples were pelleted and resuspended in fresh media and passed over 100 μm filters. Cell fractions were pelleted and embedded in Matrigel (BD Bioscience) on ice and plated into 24‑well plates (1x104 cells with 50 μl of Matrigel per well). Matrigel was polymerized at 37°C for 15 min. PDOTS were fixed in 4% paraformaldehyde for 10 min at room temperature, permeabilized with 0.2% Triton X‑100 in PBS for 5 min at room temperature and incubated in blocking buffer (2% BSA and 0.2% Triton X‑100 in PBS) for 1 h at room temperature. PDOTS were labeled with antibodies against EpCAM, clone 9C4, (BioLegend, cat no. 324210, 1:100 dilution) and CD3 (BD Pharmingen, cat no.555340, 1:100 dilution) overnight at 4°C. Cells were analyzed with a laser scanning confocal microscope (magnification, x20). DAPI and protein signals were detected at excitation wavelengths of 633 and 488 nm, respectively.