Novel xenograft and cell line derived from an invasive intraductal papillary mucinous neoplasm of the pancreas give new insights into molecular mechanisms

Abstract

Objectives: Intraductal papillary mucinous neoplasms (IPMNs) of the pancreas are a unique entity with malignant potential. Histologically, pancreatic ductal adenocarcinoma (PDAC) arising in IPMN (intraductal papillary mucinous carcinoma [IPMC]) appears similar to sporadic PDAC; biologically, however, IPMC seems to have a less aggressive clinical course. Little is known about the genetic signature of IPMC. In this study, we describe a novel xenograft model and cell culture created to biologically and genetically characterize these tumors.

Methods: Xenograft mice and cell lines were created from IPMC. Global genomic changes were evaluated by cytogenetic analysis and array comparative genomic hybridization. Specific mutations and sonic hedgehog (Shh) pathway activity were examined and xenografts evaluated for sensitivity to anti-Shh therapy.

Results: Cytogenetic analysis showed a tetraploid karyotype with multiple aberrations. KRAS and p53 mutations and overexpression of the Shh pathway were identified. Array comparative genomic hybridization revealed multiple chromosomal aberrations comparable with previously published data in IPMNs. Murine xenograft tumors were sensitive to anti-Shh treatment.

Conclusions: Characterization of IPMC cell lines and xenografts reveals similarities to previously published data on IPMN. In comparison to PDAC, moreover, these data reveal shared aberrations and distinct genomic changes. Thus, these xenograft model and cell lines may be useful for future preclinical investigations.

FIGURE 1

Histological diagnosis of IPMC. Hematoxylin and eosin stain. The primary tumor shows intraductal papillary growth (A). The arrow indicates malignant features (B) and invasive ducts (C) (original magnifications ×40, ×100, and ×200, respectively). The IPMC xenograft tumor reveals features similar to those of a moderately differentiated adenocarcinoma (D; original magnification ×100).

FIGURE 2

Karyotype of IPMC cell culture. A typical G-banded karyotype of the IPMC cell culture shows basically tetraploid features with multiple chromosomal abnormalities. mar indicates marker chromosomes.

FIGURE 3

Array CGH. Array CGH results for chromosome 6, 12, and 18, showing the following copy number changes: loss of distal 6p, loss of 6q, loss of 12p13.1–13.33, loss of 18q, and gain of 18p.

FIGURE 4

Sonic hedgehog pathway misexpression. Real-time quantitative PCR results for relative expression of Shh pathway members compared with normal pancreas. The graph shows fold overexpression of sonic hedgehog (Shh), Patched1 (Pch1), Patched2 (Ptch2), Gli2, and Smoothened (Smo).

FIGURE 5

Histological examination results. Anti-Shh treatment effects. Hematoxylin and eosin and immunohistochemistry Ki-67 staining (all images in original magnification ×100). Compared with controls, xenografts treated with 5E1, cyclopamine, or forskolin show a reduction of viable glands and proliferative cells. Treatment of xenograft mice with 5E1 and forskolin significantly reduces tumor growth (P = 0.007 and P = 0.049, respectively), proliferation (Ki-67–positive cells), and viable gland density compared with controls (P < 0.001).