Establishment and characterization of the first pediatric adrenocortical carcinoma xenograft model identifies topotecan as a potential chemotherapeutic agent

Abstract

Purpose: Pediatric adrenocortical carcinoma (ACC) is a rare and highly aggressive malignancy. Conventional chemotherapeutic agents have shown limited utility and are largely ineffective in treating children with advanced ACC. The lack of cell lines and animal models of pediatric ACC has hampered the development of new therapies. Here we report the establishment of the first pediatric ACC xenograft model and the characterization of its sensitivity to selected chemotherapeutic agents.

Experimental design: A tumor from an 11-year-old boy with previously untreated ACC was established as a subcutaneous xenograft in immunocompromised CB17 scid(-/-) mice. The patient harbored a germline TP53 G245C mutation, and the primary tumor showed loss of heterozygosity with retention of the mutated TP53 allele. Histopathology, DNA fingerprinting, gene expression profiling, and biochemical analyses of the xenograft were conducted and compared with the primary tumor and normal adrenal cortex. The second endpoint was to assess the preliminary antitumor activity of selected chemotherapeutic agents.

Results: The xenograft maintained the histopathologic and molecular features of the primary tumor. Screening the xenograft for drug responsiveness showed that cisplatin had a potent antitumor effect. However, etoposide, doxorubicin, and a panel of other common cancer drugs had little or no antitumor activity, with the exception of topotecan, which was found to significantly inhibit tumor growth. Consistent with these preclinical findings, topotecan as a single agent in a child with relapsed ACC resulted in disease stabilization.

Conclusion: Our study established a novel TP53-associated pediatric ACC xenograft and identified topotecan as a potentially effective agent for treating children with this disease.

Figure 1

Histopathology and immunohistochemistry of primary tumor and the derived SJ-ACC3 xenograft. (A) Section of original viable tumor demonstrates sheets of large polymorphic cells with abundant eosinophilic cytoplasm. Frequent mitoses, including large atypical mitotic figure, are seen. Hematoxillin&Eosin, x400. (B) Weak cytoplasmic inhibin A immunoreactivity confirmes adrenocortical differentiation of the original tumor (immunohistochemistry for inhibin A, x400).(C) Section of SJ-ACC3 demonstrates histopathology similar to that of the original tumor (above) Hematoxillin&Eosin, x400; (D) Strong nuclear staining for p53 in >90% of tumor cells (original tumor); p53 immunohistochemistry; x400.

Figure 2

Principal components analysis (PCA). The genes that were differentially expressed in pediatric adenomas and pediatric carcinomas were used for PCA (p<0.005 and fold > 1.2). The top 3 principal components are represented on the x, y, and z axes. Each symbol represents one pediatric adrenocortical tumor patient, with red indicating adrenocortical carcinoma and blue adrenocortical adenoma. Yellow and orange represent primary tumor and correspondent xenograft, respectively.

Figure 3

Activity of selective agents in the pediatric ACC xenograft model. Kaplan-Meier curves for event-free survival, median relative tumor volume graphs, and individual tumor volume graphs are shown. Control (gray lines); treated (black lines).

Figure 4

Activity of topotecan in the adult (HAC15RW cells derived from H295R) ACC xenograft model. Kaplan-Meier curves for event-free survival, median relative tumor volume graphs, and individual tumor volume graphs are shown. Control (gray lines); treated (black lines).