Establishment and evaluation of retroperitoneal liposarcoma patient-derived xenograft models: an ideal model for preclinical study

Abstract

Retroperitoneal liposarcoma (RLPS) is one of the most common subtypes of retroperitoneal soft tissue sarcomas. It is characterized by poor sensitivity to radiotherapy and chemotherapy and a low success rate of complete surgical resection. However, there are few reliable preclinical RLPS models for target discovery and therapy research. In this study, we aimed to establish RLPS patient-derived xenograft (PDX) models that are useful for biological research and preclinical drug trials. A total of 56 freshly resected RLPS tissues were subcutaneously transplanted into non-obese diabetic-severe combined immune deficient (NOD-SCID) mice, with subsequent xenotransplantation into second-generation mice. The tumor engraftment rate of first generation PDXs was 44.64%, and higher success rates were obtained from implantations of dedifferentiated, myxous, pleomorphic, high-grade liposarcomas and those with retroperitoneal organ infiltration. The first- and second- generation PDX models preserved the histopathological morphology, gene mutation profiles and MDM2 amplification of the primary tissues. PDX models can also provide the benefit of retaining original tumor biology and microenvironment characteristics, such as abnormal adipose differentiation, elevated Ki67 levels, high microvessel density, cancer-associated fibroblast presence, and tumor-associated macrophage infiltration. Overall survival (OS) and disease-free survival (DFS) of patients with successful first-generation PDX engraftment were significantly poorer than those with failed engraftment. Treatment with MDM2 inhibitor RG7112 significantly suppressed tumor growth of DDLPS PDX in mice. In conclusion, we successfully established RLPS PDX models that were histologically, genetically, and molecularly consistent with the original tissues. These models might provide opportunities for advancing RLPS tumor biology research, facilitating the development of novel drugs, particularly those targeting MDM2 amplification, adipose differentiation process, angiogenesis, cancer-associated fibroblasts, and so on.

Keywords: Retroperitoneal liposarcoma; patient-derived xenograft (PDX); prognosis; treatment evaluation; tumor biology research.

Figure 1

HE staining of RLPS tissues and corresponding P1-P2 PDX tissues. For DDLPS case 818, case 553, case 012 and case 074, original tumor (P0) and corresponding P1-P2 PDX tissues showed similar morphological structure. Scale bars, 100 μm.

Figure 2

Genetic features of primary tumors and corresponding P1-P4 PDXs in Case702. (a) HE staining of Case702 and corresponding PDXs. Scale bars, 100 μm. (b) In Case702, low-frequency gene mutations with the highest frequency not exceeding 0.03 was detected in the original tumor (P0), and no additional obvious mutations of these genes could be detected in P1-P4 PDXs. (c) FISH analysis showed that both P0 tumor and P1-P4 PDXs had MDM2 amplification (red fluorescence). Green fluorescence indicated chromosome 12, blue fluorescence showed the nucleus stained by DAPI. Scale bars, 20 μm and 5μm.

Figure 3

Expression of adipogenic differentiation and proliferation markers in fat, original RLPS tissues and corresponding P1-P2 PDX models. (a-e) Relative mRNA expression levels of PPARγ, CEBPα, LPL, ADIPOQ, and MKI67. (f) Representative IHC staining of PPARγ. P0 and P1-P2 PDX models are of PPARγ low expression. (g) Representative IHC staining of Ki67. P0 and P1-P2 PDX models are of Ki67 high expression. **P<0.01, ***P<0.001, ****P<0.0001 compared with normal fat. Scale bars, 100 μm.

Figure 4

Expression of tumor microenvironment components in RLPS tissues and corresponding P1-P2 PDX models. (a) Representative IHC staining of CD34. P0 and P1-P2 PDX models are of high microvessel density. (b) Representative IHC staining of α-SMA. P0 and P1-P2 PDXs are both of CAFs infiltration. (c) Representative IHC staining of CD163. P0 and P1-P2 PDXs are both of TAMs infiltration. Scale bars, 100 μm.

Figure 5

Correlation of OS or DFS of RLPS patients with engraftment status of RLPS tissues. (a) OS in RLPS patients with successful P1 PDXs transplantation was poorer than that with failed P1 PDXs transplantation (1.7 years vs. 2.6 years, p=0.0049). (b) DFS in RLPS patients with successful P1 PDXs transplantation was poorer than that with failed P1 PDXs transplantation (1.2 years vs. 2.2 years, p=0.0042).

Figure 6

Therapeutic response of PDX (Case702) to MDM2 inhibitor RG7112. (a-b) Compared with control group, the tumor volume of mice in treatment group were significantly reduced.*:PDX tumors. (c) The mice treated with RG7112 had a lower PDX growth rate (p=0.015).