Mouse Tumor-Bearing Models as Preclinical Study Platforms for Oral Squamous Cell Carcinoma

Abstract

Preclinical animal models of oral squamous cell carcinoma (OSCC) have been extensively studied in recent years. Investigating the pathogenesis and potential therapeutic strategies of OSCC is required to further progress in this field, and a suitable research animal model that reflects the intricacies of cancer biology is crucial. Of the animal models established for the study of cancers, mouse tumor-bearing models are among the most popular and widely deployed for their high fertility, low cost, and molecular and physiological similarity to humans, as well as the ease of rearing experimental mice. Currently, the different methods of establishing OSCC mouse models can be divided into three categories: chemical carcinogen-induced, transplanted and genetically engineered mouse models. Each of these methods has unique advantages and limitations, and the appropriate application of these techniques in OSCC research deserves our attention. Therefore, this review comprehensively investigates and summarizes the tumorigenesis mechanisms, characteristics, establishment methods, and current applications of OSCC mouse models in published papers. The objective of this review is to provide foundations and considerations for choosing suitable model establishment methods to study the relevant pathogenesis, early diagnosis, and clinical treatment of OSCC.

Keywords: HPV; OSCC; chemical carcinogen-induced; genetically engineered models; mouse models; syngeneic; transplanted; xenograft.

Figure 1

Current mouse models of OSCC. Various methods of establishing OSCC mouse models can be divided into three categories: chemical carcinogen-induced, transplanted, and genetically engineered mouse models. Adhesions: OSCC, oral squamous cell carcinoma; 4NQO, 4-nitroquinoline-1-oxide; B[a]P, Benzo[a]pyrene; DB[a,l]P, Dibenzo[a,l]pyrene; NNN, N'-nitrosonornicotine; CDX, cell-derived xenograft; PDX, patient-derived xenograft; GEMMs, genetically engineered models; SCC, squamous cell carcinoma.

Figure 2

Schematic diagram about the mechanism of 4NQO carcinogenesis. 4NQO is firstly reduced to 4HAQO by NADH and NAD(P)H, while 4HAQO can be acetylated by seryl-tRNA synthetase to form a seryl-AMP enzyme complex. The resultant 4HAQO and seryl-AMP enzyme complex are carcinogenic metabolites that induce the formation of DNA adducts. Mutations caused by these DNA adducts lead to guanine-to-pyrimidine substitution. Adhesions: 4NQO, 4-nitroquinoline-1-oxide; 4HAQO, 4-hydroxy amino quinoline-1-oxide.

Figure 3

4NQO-induced OSCC mouse model. (A–C) Representative gross morphology and pathological stages of the tongue from 4NQO-induced mice. (A) The gross tongue lesion grading system (8×), and the severity of the lesions gradually increased from 0 to 4. (B) Representative pathological stages of tongue lesions. (A,B) Reproduced and modified with permission (59). Copyright © 2014, National Academy of Sciences. (C) A whole slice image of tongue specimen contains tongue lesions of dysplasia, carcinoma in situ, and carcinoma. Reproduced and modified with permission (60). Copyright © 2017, Wiley Online Library.

Figure 4

Xenograft OSCC mouse models. (A–D) An ectopic mouse model of OSCC. (A) OSCC-BD cells overlapped and lost contact inhibition. (B) HE staining showed that OSCC-BD cells had malignant characters. (C) The nude mice were subcutaneously injected with OSCC-BD cells. Tumor formation was observed, and neoplasms were about 1.0± 0.2 cm in size. (D) HE staining showed the neoplasm was typical squamous cell carcinoma. Scale bars, 100 μm (A) and 50 μm (B). Reproduced and modified with permission (110). Copyright © 2015, Springer Nature. (E–H) An orthotopic mouse model injected into the lateral border of the tongue of non-obese diabetes–severe combined immune deficiency (NOD-SCID) mice via HSC-3 cells. The HSC-3 bearing tumors have (E,F) ulcers, (G) neural, and (H) vascular invasion (arrows). Scale bars, 0.2 cm (E), 400 μm (F), and 200 μm (G,H). Reproduced and modified with permission (111). Copyright © 2018, Springer Nature.

Figure 5

Schematic diagram of the generation of xenochimeric mice (XactMice) (162). After the cells are harvested from either cord blood or Granulocyte Colony-stimulating Factor (G-CSF) mobilized adult peripheral blood, the human hematopoietic stem and progenitor cells (HSPCs), which contain hematopoietic stem cells (HSCs), were expanded by an ex vivo technique and injected into sub-lethally irradiated NOD/SCID/IL2rg^−/− (NSG) mice to reconstitute the hematopoietic and immune system. Subsequently, tumor tissue from head and neck squamous cell carcinoma (HNSCC) patients were engrafted into NSG mice to generate the XactMice.

Figure 6

HPV-related OSCC mouse models. Mouse models of HPV-positive oral cancer can be generated by injecting HPV-positive HNSCC cell lines (CDX) or transplanting tumor fragments from HPV-positive HNSCC patients (PDX) or engrafting syngeneic HPV-positive cell lines, e.g., HPV16 E6/E7-expressing MTECs. Also, conditional GEMMs can be utilized to establish HPV-related OSCC mouse models. Adhesions: HPV, human papillomavirus; CDX, cell-derived xenograft; PDX, patient-derived xenograft; MTECs, mouse tonsil epithelial cells; GEMMs, genetically engineered models; Tam, tamoxifen.

Figure 7

The target gene X is knocked out or knocked in via the Cre-loxP recombinase system. Cre enzymes can respectively catalyze recombination between loxP sites oriented in the same direction and flank the target gene. The introduction of Cre recombinase can cause the knock-out of the gene X. The conditional knock-in of the gene X requires another sequence named strong translational and transcriptional termination (STOP), which can terminate the expression of gene X. When Cre recombinase is present, the STOP cassette can be removed and then gene X is expressed.