Validation of a Preclinical Model of Diethylnitrosamine-Induced Hepatic Neoplasia in Yucatan Miniature Pigs

Abstract

Objective: The purpose of this study was to reduce the time to tumor onset in a diethylnitrosamine (DEN)-induced hepatocellular carcinoma (HCC) swine model via partial liver embolization (PLE) and to characterize the model for use in translational research. Methods: Eight Yucatan miniature pigs were injected intraperitoneally with either saline (n = 2) or DEN (n = 6) solution weekly for 12 weeks. Three of the DEN-treated pigs underwent PLE. The animals underwent periodic radiological evaluation, liver biopsy, and blood sampling, and full necropsy was performed at study termination (∼29 months). Results: All DEN-treated pigs developed hepatic adenoma and HCC. PLE accelerated the time to adenoma development but not to HCC development. Biomarker analysis results showed that IGF1 levels decreased in all DEN-treated pigs as functional liver capacity decreased with progression of HCC. VEGF and IL-6 levels were positively correlated with disease progression. Immunohistochemical probing of HCC tissues demonstrated the expression of several important survival-promoting proteins. Conclusion: To our knowledge, we are the first to demonstrate an accelerated development of hepatic neoplasia in Yucatan miniature pigs. Our HCC swine model closely mimics the human condition (i.e., progressive disease stages and expression of relevant molecular markers) and is a viable translational model.

Improved, Shorter-Latency Carcinogen-Induced Hepatocellular Carcinoma Model in Pigs

“…Immunohistochemical staining for glypican-3, glutamine synthetase, and serum amyloid A was negative in all HCC lesions, which was not helpful in distinguishing malignant from benign lesions, but does support the categorization of well-differentiated HCC on histologic grade. Contrary to the findings by Mitchell et al [13], the livers in our pig models did not demonstrate a significant component of fibrosis or cirrhosis; hence, our study does not suggest that HCC induced via DENA in pigs arises in a background of liver cirrhosis.…”

“…In this study, the addition of PB to accelerate the tumor latency period was explored, and hepatic lesions were found as early as 5 months after treatment on MRI in 2 pigs and confirmed as HCC on pathologic examination at 10 months, representing parity and favorable tumor latency period compared to the studies by Li et al [12] and Mitchell et al [13], respectively. In addition to PB, differences in treatment protocol include a higher dose of DENA (15 vs. 10 mg/kg) as well as older age of pigs prior to initiation of treatment (6 vs. 3 months; Table 2).…”

“…Prior studies in DENA-induced HCC in pigs demonstrated a tumor latency period from 10-12 months (Li et al [12]) to 16-27 months after treatment (Mitchell et al [13]). In this study, the addition of PB to accelerate the tumor latency period was explored, and hepatic lesions were found as early as 5 months after treatment on MRI in 2 pigs and confirmed as HCC on pathologic examination at 10 months, representing parity and favorable tumor latency period compared to the studies by Li et al [12] and Mitchell et al [13], respectively.…”

“…More recently, Li et al [12] demonstrated reliable production of HCC in China Taihu pigs with a daily intraperitoneal injection of DENA for 3 months with hepatic tumors appearing 10-12 months after treatment, representing a significant improvement in the time latency to tumor formation. In another study, Mitchell et al [13] showed that performing partial liver embolization hastens DENA-induced HCC; however, their average tumor latency was not favorable compared to that of Li et al [12] (27 months for DENA alone and 16 months for DENA + partial liver embolization).…”

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“…[44,45] These models developed cirrhosis and, eventually, liver cancer over a 12-24 months period; however, this time frame is relatively impractical given the expense of housing animals for a protracted period, the unpredictability of spontaneous cancer formation, and the resultant delay in initiation of tumor-related scientific activities. In addition, tumors formed in the described model were small and numerous, which is more representative of advanced human liver cancer where the disease has already disseminated.…”