Chemotherapeutic profiles of human tumors implanted in SCID mice showing appreciable inconsistencies with those in nude mice

Challenges in pre-clinical testing of anti-cancer drugs in cell culture and in animal models

Experiments with cultures of human tumor cell lines, xenografts of human tumors into immunodeficient mice, and mouse models of human cancer are important tools in the development and testing of anti-cancer drugs. Tumors are complex structures composed of genetically and phenotypically heterogeneous cancer cells that interact in a reciprocal manner with the stromal microenvironment and the immune system. Modeling the complexity of human cancers in cell culture and in mouse models for preclinical testing is a challenge that has not yet been met although tremendous advances have been made. A combined approach of cell culture and mouse models of human cancer is most likely to predict the efficacy of novel anti-cancer treatments in human clinical trials.

Establishment of human tumor xenografts in immunodeficient mice

Heterotransplantation of human cancer cells or tumor biopsies into immunodeficient rodents (xenograft models) has, for the past two decades, constituted the major preclinical screen for the development of novel cancer therapeutics. Despite limitations, these models have identified clinically efficacious agents, and remain the 'workhorse' of the pharmaceutical industry. However, if therapeutic approaches to treating tumors according to their molecular characteristics are to be achieved, additional new models of human cancer will be required to represent the genetic diversity that exists within tumor histologies. This protocol details a method for establishing xenografts from primary solid-tumor isolates or cells grown in culture. The procedure relies on immunodeficient mice to provide a host for the establishment of human xenografts. The procedure can be completed in 1-2 h with results being obtained in 1-4 months.

Accelerated preclinical testing using transplanted tumors from genetically engineered mouse breast cancer models

PURPOSE

The use of genetically engineered mouse (GEM) models for preclinical testing of anticancer therapies is hampered by variable tumor latency, incomplete penetrance, and complicated breeding schemes. Here, we describe and validate a transplantation strategy that circumvents some of these difficulties.

EXPERIMENTAL DESIGN

Tumor fragments from tumor-bearing MMTV-PyMT or cell suspensions from MMTV-PyMT, -Her2/neu, -wnt1, -wnt1/p53(+/-), BRCA1/p53(+/-), and C3(1)T-Ag mice were transplanted into the mammary fat pad or s.c. into naïve syngeneic or immunosuppressed mice. Tumor development was monitored and tissues were processed for histopathology and gene expression profiling. Metastasis was scored 60 days after the removal of transplanted tumors.

RESULTS

PyMT tumor fragments and cell suspensions from anterior glands grew faster than posterior tumors in serial passages regardless of the site of implantation. Microarray analysis revealed genetic differences between these tumors. The transplantation was reproducible using anterior tumors from multiple GEM, and tumor growth rate correlated with the number of transplanted cells. Similar morphologic appearances were observed in original and transplanted tumors. Metastasis developed in >90% of mice transplanted with PyMT, 40% with BRCA1/p53(+/-) and wnt1/p53(+/-), and 15% with Her2/neu tumors. Expansion of PyMT and wnt1 tumors by serial transplantation for two passages did not lead to significant changes in gene expression. PyMT-transplanted tumors and anterior tumors of transgenic mice showed similar sensitivities to cyclophosphamide and paclitaxel.

CONCLUSIONS

Transplantation of GEM tumors can provide a large cohort of mice bearing mammary tumors at the same stage of tumor development and with defined frequency of metastasis in a well-characterized molecular and genetic background.

Experimental chemotherapy against canine mammary cancer xenograft in SCID mice and its prediction of clinical effect

The effectiveness of 6 antitumor agents has been evaluated for canine mammary gland tumor (CMG-6) serially transplanted into severe combined immunodeficiency (SCID) mice. CMG-6 diagnosed as a solid carcinoma was subcutaneously transplanted into SCID mice and six antitumor agents were intravenously given to the mice as a single injection. The effectiveness was evaluated by Treatment group/Control group percent (T/C %) and statistical significance determined by Mann-Whitney's U-test in tumor volume. The minimum effective doses (MEDs; mg/kg) of mice were as follows; cyclophosphamide (CPM) 65, doxorubicin (DXR) 6, cisplatin (CDDP) 5, vincristine (VCR) 1.6, vinblastine (VLB) more than 5.5, 5-fluorouracil (5-FU) 105. Clinical effects of the drugs were predicted based on area under the curve (AUC) of dogs given a clinical dose (AUCdog)/AUC of mice given a MED (AUCmouse) ratios from published references. The AUC ratios were as follows; CPM 2.24, DXR 0.19, CDDP 1.20, VCR 0.04, VLB <1.24 and 5-FU 1.15. Drugs indicating more than 1.0 in AUCdog/AUCmouse ratio were CPM, CDDP and 5-FU, and would be suggested as effective in the original patient with CMG-6. The combination chemotherapy using clinically equivalent doses in CDDP and CPM, which were the two highest values in AUCdog/AUCmouse ratio by single agent therapy, was performed and shown to have additional effects as compared to the responsiveness of each agent against CMG-6.