Serial Passage In Nude Mice Research Articles

Development of a unique mouse model for pancreatic cancer lymphatic metastasis

Lymphatic metastasis of pancreatic cancer is a predictor of poor prognosis. However, the molecular mechanisms are largely unknown, thus, making the development of appropriate cell lines and experimental models critically important for future investigations. The purpose of the present study was to establish a 'pancreatic cancer cell and mouse model with high lymphatic metastasis potential' for in-depth study of the underlying mechanisms. The BxPC-3-LN subline, derived from the BxPC-3 human pancreatic cancer cell line, was established through serial passages in nude mice via footpad injections. The subline was able to develop notable lymphatic metastases in 100% of the recipient mice 8 weeks after tumor cell implantation. Compared with the parental BxPC-3 cells, BxPC-3-LN cells were more aggressive, displaying invasive ultrastructure, increased migration and invasion ability, and chemoresistance. Metastasis-related gene alteration including upregulation of MMP14, MMP24, MIF and ADRM1, and downregulation of TGFB2 and ROBO1 were also observed in BxPC-3-LN cells by cDNA microarrays. Thus, the newly selected BxPC-3-LN subline can serve as a unique model for further study of lymphatic metastasis of pancreatic cancer.

Insulin-like growth factor binding protein 5 suppresses tumor growth and metastasis of human osteosarcoma

Osteosarcoma (OS) is the most common primary malignancy of bone. There is a critical need to identify the events that lead to the poorly understood mechanism of OS development and metastasis. The goal of this investigation is to identify and characterize a novel marker of OS progression. We have established and characterized a highly metastatic OS subline that is derived from the less metastatic human MG63 line through serial passages in nude mice via intratibial injections. Microarray analysis of the parental MG63, the highly metastatic MG63.2 subline, as well as the corresponding primary tumors and pulmonary metastases revealed insulin-like growth factor binding protein 5 (IGFBP5) to be one of the significantly downregulated genes in the metastatic subline. Confirmatory quantitative RT-PCR on 20 genes of interest demonstrated IGFBP5 to be the most differentially expressed and was therefore chosen to be one of the genes for further investigation. Adenoviral mediated overexpression and knockdown of IGFBP5 in the MG63 and MG63.2 cell lines, as well as other OS lines (143B and MNNG/HOS) that are independent of our MG63 lines, were employed to examine the role of IGFBP5. We found that overexpression of IGFBP5 inhibited in vitro cell proliferation, migration and invasion of OS cells. Additionally, IGFBP5 overexpression promoted apoptosis and cell cycle arrest in the G1 phase. In an orthotopic xenograft animal model, overexpression of IGFBP5 inhibited OS tumor growth and pulmonary metastases. Conversely, siRNA-mediated knockdown of IGFBP5 promoted OS tumor growth and pulmonary metastases in vivo. Immunohistochemical staining of patient-matched primary and metastatic OS samples demonstrated decreased IGFBP5 expression in the metastases. These results suggest 1) a role for IGFBP5 as a novel marker that has an important role in the pathogenesis of OS, and 2) that the loss of IGFBP5 function may contribute to more metastatic phenotypes in OS.

399 DEVELOPMENT AND CHARACTERIZATION OF CLINICALLY RELEVANT TUMOR MODELS FROM PATIENTS WITH RENAL CELL CARCINOMA

You have accessJournal of UrologyKidney Cancer: Basic Research1 Apr 2011399 DEVELOPMENT AND CHARACTERIZATION OF CLINICALLY RELEVANT TUMOR MODELS FROM PATIENTS WITH RENAL CELL CARCINOMA Jose Karam, Xiu-Ying Zhang, Pheroze Tamboli, Vitaly Margulis, Hua Wang, E. Jason Abel, Stephen Culp, and Christopher Wood Jose KaramJose Karam Houston, TX More articles by this author , Xiu-Ying ZhangXiu-Ying Zhang Houston, TX More articles by this author , Pheroze TamboliPheroze Tamboli Houston, TX More articles by this author , Vitaly MargulisVitaly Margulis Dallas, TX More articles by this author , Hua WangHua Wang Houston, TX More articles by this author , E. Jason AbelE. Jason Abel Houston, TX More articles by this author , Stephen CulpStephen Culp Houston, TX More articles by this author , and Christopher WoodChristopher Wood Houston, TX More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2011.02.487AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Animal models are instrumental in understanding disease pathophysiology and mechanisms of therapy action and resistance in vivo. We sought to establish and characterize a panel of mouse models of renal cell carcinoma (RCC) derived from patients undergoing radical nephrectomy. METHODS Renal cell carcinoma mouse models were established from four patients with distinct histologies of renal cell carcinoma. Tumor tissues obtained during surgery were implanted into subcutaneous space of female BALB/c nude mice and serially passaged into new mice. Tumors obtained directly from patients and those derived from serial passages in nude mice were characterized by histology, Short Tandem Repeat (STR) fingerprinting, VHL gene sequencing, and Single Nucleotide Polymorphism (SNP) analysis for each of the four histologies. Tumor bearing mice were treated with sunitinib or everolimus and growth was compared between different histologies and different tumor passages. Primary cell cultures were also derived from patient tumors and were transfected with a lentiviral vector carrying the luciferase gene. Bioluminescence imaging (BLI) of mice was performed after intraperitoneal injection of luciferin in 2 of the models. RESULTS Four subcutaneous xenograft mouse models were developed: MDA−RCC−48, MDA−RCC−55, MDA−RCC−62, and MDA−RCC−80, representing papillary type 1, papillary type 2, clear cell, and clear cell with sarcomatoid features renal cell carcinoma, respectively. Tumor growth was dependent on the histologic type, size of implanted tumor chip, and possibly the passage number. We confirmed that the mouse tumors accurately and faithfully represent their respective original patient tumors as STR fingerprints were matching, histology on H&E staining was comparable, and SNP profiles and VHL mutation status were conserved with multiple passages. BLI results were commensurate with the subcutaneous xenograft growth patterns and enabled sequential and non−invasive monitoring of growth in an orthotopic implantation setting. Mice treated with sunitinib and everolimus exhibited an initial response to these agents, followed by a later stage of resistance to these agents, which mimics the clinical observations in patients with RCC. CONCLUSIONS We developed four mouse xenograft models of RCC with clear cell and papillary histologies, with stable histologic and molecular characteristics. We are currently using these models to identify mechanisms of action, molecular correlates of response, and resistance to novel targeted therapies. © 2011 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 185Issue 4SApril 2011Page: e161 Advertisement Copyright & Permissions© 2011 by American Urological Association Education and Research, Inc.MetricsAuthor Information Jose Karam Houston, TX More articles by this author Xiu-Ying Zhang Houston, TX More articles by this author Pheroze Tamboli Houston, TX More articles by this author Vitaly Margulis Dallas, TX More articles by this author Hua Wang Houston, TX More articles by this author E. Jason Abel Houston, TX More articles by this author Stephen Culp Houston, TX More articles by this author Christopher Wood Houston, TX More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Abstract PL05-04: Gene signatures for targeted and cytotoxic agents can guide new anticancer drug development

The identification of biomarkers or gene signatures predicting tumor response to novel targeted or cytotoxic therapy has the potential to individualize and improve the effectiveness of anticancer therapy. The FDA strongly recommends developing such companion diagnostic tests. Clinical relevance of predictive markers has, for example, been demonstrated for EGFR inhibitors like cetuximab or pamituzumab, which are primarily effective in tumors with wild type k‐ras status. Sets of genes ‐ the so‐called gene signatures ‐ have probably even a greater potential for prediction of tumor response than a single marker gene. Our hypothesis was that the correlation of drug response with gene expression would allow the identification of gene signatures that can predict the drug response of individual tumors. The expression profiles of thousands of genes are easily accessible with gene expression arrays, provided fresh or frozen tumor samples are available. However, in the clinic it is difficult to discriminate between groups of responding and resistant tumors as would be required for the derivation of gene signatures. Therefore, we used patient‐derived tumor models established subcutaneously in nude mice to determine the in vivo sensitivity towards registered and developmental compounds. Patient tumors established subcutaneously in serial passage in nude mice were characterized for their sensitivity towards two targeted and 10 standard cytotoxic anticancer agents. The latter included the alkylating agents cyclophosphamide, ifosfamide, mitomycin‐C and cisplatin; the antimetabolites 5‐FU and gemcitabine; the topoisomerase II inhibitors adriamycin and etoposide as well as the tubulin binders paclitaxel and docetaxel. The mean number of tumors treated with any of the various drugs was 54 (range 31–78). The tumor xenografts9 gene expression profiles were determined using the Affymetrix HG‐U133 plus 2.0 mRNA expression array representing ∼38,500 human genes. For all 12 tested agents, predictive gene signatures were identified and subsequently verified using the leave‐one‐out cross‐validation (LOOCV) technique. For three of the drugs, signatures were further validated using an independent set of previously untested tumors. Tumors were considered as responsive if the drugs effected a tumor volume inhibition to less than 11–41% of vehicle control tumors (T/C %). The median cut‐off for all drugs was a T/C of 25%. Using these criteria, on average one third of the test tumors were classified as sensitive (responders) and two thirds were resistant (non‐responders). The bioinformatic analysis yielded predictive gene signatures consisting of 20–129 genes (mean for the 12 drugs: 87 genes). On average, the response rate of predicted responders (83%) was 2.45 fold higher than that of all test tumors (random testing, 34%). This increase of response rates, following signature‐guided testing, was consistent for all agents. Conversely, 94% of the predicted non‐responders (range: 84–100%) proved to be non‐responders in the nude mouse. The function of the majority of genes (59%) making up the predictive gene signatures was unknown. Genes with known function are implicated in cell proliferation, apoptosis, DNA repair, cell cycle, metabolism and transcription. In summary, the predictive gene signatures presented here for 12 cytotoxic agents have the potential to substantially increase tumor response rates compared to empirical drug treatment. Similarly, the VEGF antibody Bevacizumab (BV) was also evaluated in 72 tumors (colon, NSC‐lung, breast and renal cancers). BV was administered iv once weekly for 3 weeks. Antitumor activity was evaluated as the minimum T/C value or after 28 days. Using a T/C of We have also developed a gene signature for Cetuximab (CTX) consisting of 21 genes. Using a T/C of For both marketed drugs and drugs in development, gene signatures have great potential to increase the response rates compared to empirical drug treatment. However, clinical application of the gene signatures needs validation in a clinical setting. In a first clinical feasibility study with 72 patients with different solid tumors that we have initiated, the tumor response to BV and CTX was predicted to be 26 tumors (36%) for BV and 13 (18%) for CTX, the latter mainly colon and gastric cancers. Gene signatures have a great potential to increase the response rates compared to empirical drug treatment for marketed drugs and also for drugs in development. However, the gene signatures need to be further validated in clinical studies. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):PL05-04.

Establishment and characterization of a new highly metastatic human osteosarcoma cell line

Osteosarcoma is the most common primary malignancy of bone in children and young adults. There is a paucity of tumorigenic and highly metastatic human osteosarcoma cell lines that have not been further transformed by exogenous means. Here we establish and characterize a highly metastatic human osteosarcoma cell line that is derived from a poorly metastatic MG63 line through serial passage in nude mice via intratibial injections. The occasional pulmonary metastases developed from MG63 were harvested and repassaged in mice until a highly metastatic subline (MG63.2) was established. The parental MG63 and highly metastatic MG63.2 cells were further characterized in vitro and in vivo. MG63.2 cells demonstrated increased cell migration and invasion compared to the parental MG63 cells. Conversely, cell adhesion was significantly greater in MG63 cells when compared to the MG63.2 cells. MG63.2 cells grew at a slightly slower rate than that of the parental cells. When injected into nude mice, MG63.2 cells had a greater than 200-fold increase in developing pulmonary metastases compared to the parental MG63 cells. MG63.2 cells also formed larger primary tumors when compared to the parental MG63 cells. Further analysis revealed that ezrin expression was up-regulated in the metastatic MG63.2 cells. Interestingly, expressions of MMP-2 and MMP-9 were down-regulated, and expression of TIMP-2 was up-regulated in the MG63.2 cells. Taken together, we have established and characterized a highly metastatic human osteosarcoma cell line that should serve as a valuable tool for future investigations on the pathogenesis, metastasis, and potential treatments of human osteosarcoma.

Clonogenic assay with established human tumour xenografts: correlation of in vitro to in vivo activity as a basis for anticancer drug discovery

Pluripotent cells can be grown in clonogenic assays. The tumour stem-cell fraction, which accounts for <0.4% of the total cells, and which is considered the most relevant cell type in the development of metastases and recurrences, is able to divide and to form colonies in a semisolid matrix (agar or methylcellulose). Major applications of the tumour clonogenic assay (TCA) are chemosensitivity testing of tumours and xenografts, and for assessments within drug discovery programmes. Of critical relevance for the usefulness of the TCA is whether it can predict sensitivity or resistance towards clinically used agents. When we compared the response of human tumours established as xenografts in nude mice in the TCA in vitro to that of the clinical response, 62% of the comparisons for drug sensitivity, and 92% of the comparisons for drug resistance were correct. The same percentage of true/false observations was found when tumours were tested after serial passage in nude mice in the TCA in vitro and their response compared to in vivo activity in corresponding xenografts (60% and 90%, respectively). The highest correct predictive values were, however, found when the clinical response of tumours was compared to their explants established in the nude mouse and treated in vivo. Of 80 comparisons performed, we observed a correct prediction for tumour resistance in 97% and for tumour sensitivity in 90%. In our opinion, the TCA with established human tumour xenografts has an important role in current drug discovery strategies. We therefore included the TCA as secondary assay in our approach to anticancer drug discovery and found that a number of novel agents were active; these are now in advanced preclinical development or clinical trials. Thus, the tumour clonogenic assay has proven predictive value in the chemosensitivity testing of standard and experimental anticancer drugs.

No evidence of tumor growth stimulation in human tumors in vitro following treatment with recombinant human growth hormone

In a recent study we demonstrated that recombinant human growth hormone (r-hGH; Saizen) delayed tumor-induced cachexia in human tumor xenografts in vivo. Such a therapeutic effect could have a great impact in the supportive care of advanced cancer patients. Before large clinical studies are initiated possible growth stimulation should be excluded. This question was investigated in vitro in 20 human tumor models, which had been established in serial passage in nude mice. The effect of continuous exposure of r-hGH was investigated at dose levels ranging from 0.3 ng/ml up to 0.1 microg/ml in colorectal (n=2), gastric (n=1), non-small cell lung (n=4), small cell lung (n=1), mammary (n=3), ovarian (n=2), prostate (n=2) and renal cancers (n=2), and melanoma (n=3) using a modified Hamburger and Salmon clonogenic assay. The results show that there was neither tumor growth inhibition nor any evidence for tumor growth stimulation in any of the tumors studies. Therefore this preclinical study in 20 human tumor models indicated no direct risk for tumor growth enhancement.

Growth patterns and cell kinetics of human osteosarcoma xenografts in serial passages in nude mice analyzed by in vivo labelling with iododeoxyuridine.

A human osteoblastic osteosarcoma was transplanted in nude mice and followed in seven serial passages. Tumor cell kinetics was analyzed by in vivo labelling with the thymidine analogue iododeoxyuridine (IdUrd). Immunohistochemistry was used to measure the IdUrd labelling index. Duration of S phase (ts) was estimated by flow cytometry. From these two parameters potential doubling time (tpot) was calculated. Cell kinetic parameters showed low variations between passages and also between xenografts in same passage. Smaller variations of ts compared to labelling index and tpot were found. tpot was generally short with an interpassageal mean of 1.3 days and CV=14.8%. All xenografts showed DNA aneuploidy (mean DNA index --1.6). Homogeneous tumor growth was indicated by low variations of volume doubling time and lag time. There was no correlation between tumor growth and cell proliferation. Histopathological characteristics of the donor patients tumor were retained during serial transplantation.

Establishment of a human small cell lung carcinoma cell line carrying amplification of c-myc gene and chromosomal translocation of t(3p;6p) and t(12q;17p).

A transplantable tumor and an in vitro culture cell line (GK‐T3) were established from metastatic liver tissue of human small cell lung carcinoma (SCLC). Southern blot analysis revealed about 30‐fold amplification of c‐myc gene in the tumor cells in liver, xenografts, and in vitro cell line. The degree of c‐myc amplification was essentially conserved through serial passages in nude mice and cultivation in vitro. The level of c‐myc mRNA was significantly increased in these cells. Cytogenetically, numerical and complex structural abnormalities were observed in GK‐T3 cells, including t(3p;6p), t(12q;17p), two homogeneously staining regions (hsrs) and several double minutes (dmins). These results suggest that activation of c‐myc gene and alteration of gene(s) round these chromosomal breakpoints may play a role in tumorigenesis of GK‐T3 SCLC.

The clonogenic assay with human tumor xenografts: Evaluation, predictive value and application for drug screening

The feasibility, evaluation and predictive value of the colony-forming assay with human tumor xenografts for screening anticancer drugs have been studied. Using human tumors grown in serial passage in nude mice, adequate colony formation was observed in 215 of 251 (86%) different solid human tumors of various histologies. Based on in vitro growth characteristics, a quality-controlled assay protocol was developed. With the proposed criteria for standardized evaluation of individual experiments a substantial increase in assay reliability was achieved. The five clinically established agents, cisplatin, doxorubicin, etoposide, mitomycin-C and vindesine, were studied for anticancer activity in the clonogenic assay. Drugs were applied over a wide dose range by continuous exposure, yielding clear dose-response effects with coefficients of correlation between r = 0.946 and 0.995. Relevant dose levels predicting correctly for the clinical efficacy of the agents were determined by comparison of in vitro anticancer activity to in vitro toxicity on human bone marrow as follows: cisplatin 0.1 micrograms/ml, doxorubicin 0.01 micrograms/ml, etoposide 0.1 micrograms/ml, mitomycin-C 0.005 micrograms/ml, vindesine 0.01 micrograms/ml. At these concentrations, clinically sensitive tumor types showed inhibition of colony formation in 99 of 240 cases (41%), whereas 11% (19/176) of clinically resistant tumors were responsive. The relevant dose levels used equal between 0.3% and 4.0% of the achievable peak plasma concentrations in man. The predictive value of the clonogenic assay was determined by treatment of the same tumors in vitro and in vivo in tumor-bearing nude mice. In 174/220 comparisons (79%), in vitro data predicted correctly for the in vivo sensitivity of the xenografted malignancies.(ABSTRACT TRUNCATED AT 250 WORDS)

Cytogenetic and quantitative DNA analysis of primary and xenografted human osteosarcomas

We have analyzed, cytogenetically and by flow DNA cytometry, three human osteosarcomas. From one case, both the primary tumor (T9) and three of its serial passages in nude mice were analyzed. From the two other tumors (T1, T4), nude mouse xenografts were examined. Complex karyotypic rearrangements were invariably found in the short-term culture preparations. The major clones were hypodiploid in T1 but near-triploid in all other tumor samples. No rearrangement common to all tumors could be identified. The DNA indexes were 1.0/2.0 (T1), 1.4 (T4), 0.9/1.8 (T9 primary), and 1.7 (all T9 xenografts). Thus, there was good correlation between the DNA indexes and the chromosome numbers. Chromosomal evolution could be studied in one case, in which both the primary tumor (T9) and its xenograft passages (1, 4, and 7), obtained 1, 7, and 11 months after the first transplantation of T9 cells to nude mice, were analyzed. All but one of the clonal marker chromosomes found in the primary tumor were retained in all passages. On the other hand, several new clonal markers developed.

Osteosarcoma and interferon

This work assessed the transplantability of human osteosarcomas to immunodeficient nude mice. Osteosarcomas serially transplanted in nude mice were characterized by growth rate, histologic features, and nuclear DNA content. The osteosarcoma xenografts were used to investigate the antitumor effects of interferon (IFN). Tumor tissue from 25 primary osteosarcomas was transplanted into nude mice. All tumors were histologically of high grade (III-IV). Flow DNA cytometry disclosed that all, except 1, had a nondiploid DNA content. 14 of the 25 osteosarcomas grew in serial passage in nude mice, i.e., the take rate was 0.6. The transplantable osteosarcoma group was characterized by a predominance of Grade IV lesions, and a high proportion of proliferating cells, compared to the nontransplantable. The 14 osteosarcoma xenografts, established in nude mice, were heterogeneous with respect to growth rate, histologic subtype, DNA content, and proliferative activity. However, the osteosarcomas retained the basic characteristics of their respective original tumor; the xenografts exhibited the same histologic appearance and DNA content in the first 2 passages in nude mice. During serial transplantation of the 14 osteosarcomas, the histologic features remained unaltered from passage to passage during the observation period of up to 3 years. The aneuploid DNA content was also unchanged over time in most tumors. However, in 4 osteosarcomas with 2 aneuploid cell populations, the cell population with the higher DNA content became predominant, while the other gradually disappeared. Hence, the changes in DNA content involved polyploidization, followed by selection of the cell population with higher DNA content. At the same time growth rate increased, but histologic features were unchanged. This study of osteosarcoma, serially transplanted in nude mice, shows that growth rate, histologic appearance, and DNA content are relatively stable tumor features. The observed changes in DNA content illustrate the development of aneuploidy in malignant tumors. The antitumor effects of human nIFN-alpha were assessed in the 14 osteosarcoma xenografts. In dose-response experiments, based on 2 different tumors, 2 x 10(5) IU/day of nIFN-alpha was found to arrest tumor growth. This dose was chosen as the standard dose in subsequent experiments. Among the 14 osteosarcomas, tumor regression or growth arrest was seen in 5, whereas 8 were only partially growth inhibited with the standard dose. The remaining osteosarcoma was growth inhibited with higher nIFN-alpha doses. Hence, all 14 analyzed osteosarcomas were sensitive to the antitumor effect of nIFN-alpha.(ABSTRACT TRUNCATED AT 400 WORDS)

Growth and ploidy of human osteosarcoma xenografts in serial passage in nude mice

Six human osteosarcoma tumors have been transplanted to and maintained as xenografts in serial passage in nude mice. The xenografts, characterized by growth rate, histologic appearance, and DNA flow cytometric data, are now in the 6–17 passages in mice. Histologic appearances and growth rates of the xenografts were unchanged through all passages except for one xenograft in which the growth rate doubled in passage 3. All six tumors had hyperploid DNA contents. The ploidy levels were unchanged, compared to their original tumors, in all passages of five xenografts. One xenograft, concomitantly with the increase in growth rate, also doubled the ploidy from 2.8 to 5.6 C. There was a good agreement between the proportion of S-phase cells and mitotic indices of the six xenografts. The growth rate, depending also on cell loss, was less related to the proliferative activity of the xenografts. It was concluded that osteosarcomas have a stable aneuploid DNA content in nude mice, but polyploidization can occur after a number of passages.

Efficacy of the anticancer agent cisplatin in the treatment of human cervical squamous carcinoma xenografted in nude mice.

Two human squamous carcinomas of the cervix, established by serial passage in nude mice, are described. The response of the tumours to cis-diamminedichloroplatinum (CDDP) was assessed by comparing tumour weights and by histological observations. Tumours treated with CDDP 10 mg/kg/week for 2 weeks regressed significantly and microscopy revealed extensive degeneration. Treatment with CDDP 5 mg/kg/week produced tumour growth retardation and microscopy showed some degenerative changes, however, viable cells, many of which were mitotic, were evident. There was, therefore, a dose-response relationship. The sensitivity of the tumours to CDDP lends support to its use in humans with this malignancy.

Comparison between macroscopic and microscopic evaluation of tumour responsiveness using the subrenal capsule assay

Using the subrenal capsule assay in normal mice, a histologic evaluation was made of 8 human primary ovarian tumours and 3 human colon, 2 lung and 5 ovarian carcinomas growing in serial passage in nude mice. The results of the evaluation indicated that there is a tumour- and drug-dependent correlation between the macroscopically and microscopically evaluated effects, with cyclophosphamide demonstrating excellent concordance but adriamycin and cisplatin both demonstrating consistently more tumour cell killing on histologic analysis than could be appreciated macroscopically. Leukocyte infiltration and fibrosis were greatly increased by the latter 2 drugs, leading to unrepresentative macroscopic measurements. Variable amounts of host cell infiltration can also be demonstrated in the untreated control when normal mice are used. The use of nude mice decreases the discrepancy between macroscopic and microscopic evaluation.

Growth characteristics of human malignant tumours and cell lines in serial passages in nude mice.

Two osteosarcoma cell lines, one fibrosarcoma and one undifferentiated mesenchymal tumour obtained at operation, all of human origin, were transplanted in serial passages in athymic nude mice. The growth rate was analysed and the morphologic appearance compared both with the original tumours and after each passage. All tumours retained their morphologic characteristics during the transplantation and passaging in the nude mice with only minor alterations in structure. The growth rates of the tumours showed great variability even in the same passage of each tumour, although the growth rates became somewhat more regular and predictable after some passages.

Metastasis of human tumors in athymic nude mice.

The incidence of metastasis of xenogeneic tumors transplanted to nude mice is controversial. We studied 106 malignant human tumor lines in a total of 1,045 nude mice, and observed metastasis in only 14 instances (1.3%), involving 11 different tumor lines. Three of the lines showed repeated metastasis. Breast tumor lines metastasized with significantly greater frequency than other tumor types. None of the sarcoma lines metastasized. Tumors derived from human metastases were no more prone to metastasizing in nude mice than were tumors derived from primary sites. However, deep penetration of the body wall during growth of the tumor transplant was highly correlated with metastasis (p less than 0.001). Such factors as nude mouse health, tumor size and growth rate, and age and sex of the host mouse were not correlated with metastasis. Serial passage in nude mice did not select for a more malignant tumor line, since the incidence of metastasis did not differ at various passage levels. Thus, metastasis of human malignant tumors in nude mice would appear to depend primarily upon the site of tumor growth in the nude mouse, and upon the intrinsic metastasizing capability of the tumor line employed.