Establishment and characterisation of patient-derived xenografts as paraclinical models for gastric cancer

Abstract

The patient-derived xenograft (PDX) model is emerging as a promising translational platform to duplicate the characteristics of tumours. However, few studies have reported detailed histological and genomic analyses for model fidelity and for factors affecting successful model establishment of gastric cancer. Here, we generated PDX tumours surgically-derived from 62 gastric cancer patients. Fifteen PDX models were successfully established (24.2%, 15/62) and passaged to maintain tumours in immune-compromised mice. Diffuse type and low tumour cell percentage were negatively correlated with success rates (p = 0.005 and p = 0.025, respectively), while reducing ex vivo and overall procedure times were positively correlated with success rates (p = 0.003 and p = 0.01, respectively). The histology and genetic characteristics of PDX tumour models were stable over subsequent passages. Lymphoma transformation occurred in five cases (33.3%, 5/15), and all were in the NOG mouse, with none in the nude mouse. Together, the present study identified Lauren classification, tumour cell percentages, and ex vivo times along with overall procedure times, as key determinants for successful PDX engraftment. Furthermore, genetic and histological characteristics were highly consistent between primary and PDX tumours, which provide realistic paraclinical models, enabling personalised development of treatment options for gastric cancer.

Figure 1. Histologic and genomic features between primary and PDX tumours.

(A) Tumour section slides were stained to H & E for comparing histology of F1 and F3 PDX tumours with their corresponding F0 tumour in two PDX models. a, F0 from GA006; b, F1 from GA006; c, F3 from GA006; d, F0 from GA013; e, F1 from GA013; f, F3 from GA013. Scale bars = 100 μm. (B,C) De novo and disappeared mutations between F0 and F3 PDX tumours of GA006 (B) and GA013 (C) models. De novo mutations are defined as total allele count being zero in the F0 and greater than or equal to five in F3. The opposite cases are disappeared mutations.

Figure 2. Correlation of genetic features for 726 cancer-related genes between primary and PDX tumours.

(A) Mutations in F0 and F3 tumours among 726 cancer-related genes were indicated in GA006 (dark blue bars) and GA013 (red bars) PDX models. (B) Mutant allele frequencies between F0 and F3 tumours for 14 and 7 mutations detected in GA006 (blue dots) and GA013 (red dots) PDX models, respectively. (C,D) The correlation of mRNA expression levels for 726 cancer-related genes in F0 and F3 tumours was represented as scatter plot in GA006 (C) and GA013 (D) PDX models.

Figure 3. Representative histology of lymphoma transformed PDX tumours.

(A) F0 tumour section slides were stained by H & E. (B) F1 tumour section slides were stained by H & E. (C) Cytokeratin, as a marker of epithelial tumour cells, was not detected by immunohistochemistry in F1 tumour. (D) CD3, as a marker of T cells, was infrequently detected by immunohistochemistry in F1 tumour. (E) CD20, as a marker of B cells, was detected by immunohistochemistry in F1 tumour. (F) Epstein-Barr encoded RNA was detected by in situ hybridization in F1 tumour. Scale bars = 50 μm.

Figure 4. Schematic drawing of sequential histological changes into lymphomas according to the mouse strain during subpassaging in PDX model.

(A) An engrafted adenocarcinoma in an F1 NOG mouse changed into a lymphoma in F2 NOG mice. It was retained in F3 NOG mice, but was not engrafted into F3 nude mice. However, an adenocarcinoma engrafted from an F1 NOG mouse into F2 nude mice retained their histology, and the tumour was not changed into a lymphoma in an F3 nude mouse as well as in F3 NOG mice. (B) Each section slide of primary and PDX tumour during subpassaging was stained by H & E for comparing their histological changes. a, adenocarcinoma in a primary tumour; b, adenocarcinoma in an F1 NOG mouse; c, lymphoma in an F2 NOG mouse; d, adenocarcinoma in an F2 nude mouse; e, lymphoma in an F3 NOG mouse; f, no tumour growth in an F3 nude mouse from an F2 NOG mouse; g, adenocarcinoma in an F3 NOG mouse from an F2 nude mouse; h, adenocarcinoma from an F3 nude mouse from an F2 nude mouse. Scale bars = 100 μm. *from F2 NOG mice, †from F2 nude mice.