A suitable model for experimental liver metastasis of human colon cancer xenografts using mice with severe combined immunodeficiency

Establishment and Validation of an Orthotopic Metastatic Mouse Model of Colorectal Cancer

Metastases are largely responsible for cancer deaths in solid tumors due to the lack of effective therapies against disseminated disease, and there is an urgent need to fill this gap. This study demonstrates an orthotopic colorectal cancer (CRC) mouse model system to develop spontaneous metastasis in vivo and compare its reproducibility against human CRC. IGF1R-dependent GEO human CRC cells were used to study metastatic colonization using orthotopic transplantation procedures and demonstrated robust liver metastasis. Cell proliferation assays were performed both in the orthotopic primary colon and liver metastatic tumors, and human CRC patient's specimen and similar patterns in H&E and Ki67 staining were observed between the orthotopically generated primary and liver metastatic tumors and human CRC specimens. Microarray analysis was performed to generate gene signatures, compared with deposited human CRC gene expression data sets, analyzed by Oncomine, and revealed similarity in gene signatures with increased aggressive markers expression associated with CRC in orthotopically generated liver metastasis. Thus, we have developed an orthotopic mouse model that reproduces human CRC metastasis. This model system can be effective in developing new therapeutic strategies against disseminated disease and could be implemented for identifying genes that regulate the development and/or maintenance of established metastasis.

Establishment of canine hemangiosarcoma xenograft models expressing endothelial growth factors, their receptors, and angiogenesis-associated homeobox genes

BACKGROUND

Human hemangiosarcoma (HSA) tends to have a poor prognosis; its tumorigenesis has not been elucidated, as there is a dearth of HSA clinical specimens and no experimental model for HSA. However, the incidence of spontaneous HSA is relatively high in canines; therefore, canine HSA has been useful in the study of human HSA. Recently, the production of angiogenic growth factors and their receptors in human and canine HSA has been reported. Moreover, the growth-factor environment of HSA is very similar to that of pathophysiological angiogenesis, which some homeobox genes regulate in the transcription of angiogenic molecules. In the present study, we established 6 xenograft canine HSA tumors and detected the expression of growth factors, their receptors, and angiogenic homeobox genes.

METHODS

Six primary canine HSAs were xenografted to nude mice subcutaneously and serially transplanted. Subsequently, the expressions of vascular endothelial growth factor (VEGF)-A, basic fibroblast growth factors (bFGF), flt-1 and flk-1 (receptors of VEGF-A), FGFR-1, and angiogenic homeobox genes HoxA9, HoxB3, HoxB7, HoxD3, Pbx1, and Meis1 were investigated in original and xenograft tumors by histopathology, immunostaining, and reverse transcription polymerase chain reaction (RT-PCR), using canine-specific primer sets.

RESULTS

Histopathologically, xenograft tumors comprised a proliferation of neoplastic cells that were varied in shape, from spindle-shaped and polygonal to ovoid; some vascular-like structures and vascular clefts of channels were observed, similar to those in the original tumors. The expression of endothelial markers (CD31 and vWF) was detected in xenograft tumors by immunohistochemistry and RT-PCR. Moreover, the expression of VEGF-A, bFGF, flt-1, flk-1, FGFR-1, HoxA9, HoxB3, HoxB7, HoxD3, Pbx1, and Meis1 was detected in xenograft tumors. Interestingly, expressions of bFGF tended to be higher in 3 of the xenograft HSA tumors than in the other tumors.

CONCLUSION

We established 6 xenograft canine HSA tumors in nude mice and found that the expressions of angiogenic growth factors and their receptors in xenograft HSAs were similar to those in spontaneous HSA. Furthermore, we detected the expression of angiogenic homeobox genes; therefore, xenograft models may be useful in analyzing malignant growth in HSA.

Liposomal irinotecan: formulation development and therapeutic assessment in murine xenograft models of colorectal cancer

PURPOSE

The purpose is to demonstrate whether an appropriately designed liposomal formulation of irinotecan is effective in treating mice with liver-localized colorectal carcinomas.

EXPERIMENTAL DESIGN

Irinotecan was encapsulated in 1,2-distearoyl-sn-glycero-3-phosphocholine/cholesterol (55:45 molar ratio) liposomes using an ionophore (A23187)-generated transmembrane proton gradient. This formulation was evaluated in vivo by measuring plasma elimination of liposomal lipid and drug after i.v. administration. Therapeutic activity was determined in SCID/Rag-2M mice bearing s.c. LS180 tumors or orthotopic LS174T colorectal metastases.

RESULTS

Drug elimination from the plasma was significantly reduced when irinotecan was administered in the liposomal formulation. At 1 hour after i.v. administration, circulating levels of the liposomal drug were 100-fold greater than that of irinotecan given at the same dose. High-performance liquid chromatographic analysis of plasma samples indicated that liposomal irinotecan was protected from inactivating hydrolysis to the carboxylate form. This formulation exhibited substantially improved therapeutic effects. For the LS180 solid tumor model, it was shown that after a single injection of liposomal irinotecan at 50 mg/kg, the time to progress to a 400-mg tumor was 34 days (as compared with 22 days for animals treated with free drug at an equivalent dose). In the model of colorectal liver metastases (LS174T), a median survival time of 79 days was observed after treatment with liposomal irinotecan (50 mg/kg, given every 4 days for a total of three doses). Saline and free drug treated mice survived for 34 and 53 days, respectively.

CONCLUSIONS

These results illustrate that liposomal encapsulation can substantially enhance the therapeutic activity of irinotecan and emphasize the potential for using liposomal irinotecan to treat liver metastases.

Growth and metastatic behavior of five human glioblastomas compared with nine other histological types of human tumor xenografts in SCID mice

The growth and metastatic behavior of five human glioblastoma multiforme xenografts and nine human xenografts of various histological types were compared in severe combined immunodeficient (SCID) mice. The results demonstrate that the metastatic behavior of the human glioblastoma multiforme xenografts did not differ significantly from a variety of other histological xenografts when evaluated at the same transplantation site in the SCID model. These results are consistent with the hypothesis that the site of glioblastoma multiforme growth influences the extraneural metastatic spread of this disease and lead the authors to suggest that the clinical rarity of distant metastasis is not a fundamental property of these cells. A total of 340 male 7- to 8-week-old SCID mice received subcutaneous transplantation of tumor fragments (21-25 mice per tumor type). The tumor-bearing leg was amputated when the tumor reached a volume of 500 mm3; mice were observed for up to 5 months. There was a trend for a lower take rate, longer latent period, longer volume doubling time (VDT) and growth time (GT) in glioblastoma multiforme as opposed to carcinoma and soft tissue sarcoma xenografts. The highest local recurrence rates (78% and 68%) were observed in two glioblastomas multiforme. Both the glioblastoma multiforme and the other histological xenografts exhibited a widely varying metastatic rate: no correlation was demonstrated between VDT, GT, local control/recurrence, and distant metastasis. These findings show SCID mice to be an attractive model for further biological and preclinical studies of human glioblastoma multiforme.

Metastatic models of human cancer xenografted in the nude mouse: the importance of orthotopic transplantation

Metastatic model of human tumor xenografts have been developed using orthotopic transplantation of histologically intact tissue (onplantation) of lung, stomach, colon, pancreatic, prostate and bladder carcinomas. These models represent the entire process of the metastasis, consisting of local tumor growth, vascular and lymphatic invasion at the local site, flow in the vessels and lymphatic, extravasation at the metastatic organs, and seeding and growth at relevant metastatic sites. Orthotopically transplanted human small-cell lung carcinoma displayed a different chemosensitivity pattern compared with the subcutaneous transplanted model, suggesting different pharmacodynamics between the orthotopic lung and the ectopic subcutaneous sites. The intact-tissue orthotopic-onplantation model seems to be useful to study the mechanism of metastasis for discovery of antimetastatic agents and for the patient tumors and for this treatment design.

Significance of in vitro attachment of human colon cancers to extracellular matrix proteins in experimental and clinical liver metastases

The attachment of 7 human colon cancer lines transplantable into nude mice, and primary tumors and liver metastases from 30 patients with colon cancer to 4 extracellular matrix proteins (EMPs)--Matrigel, laminin, fibronectin, and type IV collagen--was evaluated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H (MTT) assay. Cancer cells from the 4 established tumor lines which produced experimental liver metastases in vivo showed significantly greater attachment to each EMP than those from the other 3 tumor lines which did not. Although there were no significant differences between attachment to EMPs of cancer cells from 15 clinical primary tumors with liver metastases and those without, attachment to each EMP of cells derived from liver metastases was significantly greater than that of the cells from the corresponding primary tumors in 8 cases for which liver metastases and primary tumors were examined simultaneously. Attachment to EMPs, which could be determined simply and rapidly using the MTT assay, is thus considered a significant factor in experimental and clinical liver metastases of human colon cancers.

Experimental cancer chemotherapy using a liver metastatic model of human colon cancer transplanted into the spleen of severe combined immunodeficient mice

We have developed a liver metastatic model of human colon cancer using severe combined immunodeficient (SCID) mice. Liver metastases were observed in all the SCID mice on day 28 after intrasplenic injection with 5 x 10(6) dissociated tumor cells of COL-2-JCK, a human colon cancer strain serially transplanted in nude mice. When this model was applied for chemotherapeutic experiments, 5-fluorouracil (5-FU) demonstrated significant antitumor effects in preventing liver metastases, whereas the efficacy of 5-FU was limited in the currently used sc-ip chemosensitivity assay in nude mice. When the human LDH-5 isozyme was evaluated in the homogenized metastatic liver tissue of SCID mice, a good correlation was obtained between the liver tumor weights and LDH-5 isozyme, suggesting that it could be a promising quantitative indicator for metastases. This model would be useful for further studies on the treatment of liver metastases of colon cancer.