Differences in immunoreactivity of estrogen receptor (ER) in tamoxifen-sensitive and -resistant breast carcinomas: preclinical and first clinical investigations.

Inherited or acquired tamoxifen resistance is a major constraint in the endocrinological treatment of breast carcinomas. We developed an enzyme-immunoassay that discriminates between tamoxifen-sensitive and -resistant tumors. The procedure was established and standardized using two xenografted breast carcinomas--3366 (highly sensitive to tamoxifen) and 3366/TAM (acquired tamoxifen resistance). The latter model was developed by treatment of 3366 tumor-bearing nude mice during serial passaging over 3 years with tamoxifen. Both lines were estrogen receptor (ER) positive (101 or 82 fmol/mg protein), and revealed no differences in the nucleotide sequences of the hormone binding domain of the ER protein. However, while in the sensitive tumors an upregulation of ER levels was registered after estradiol treatment of tumor bearing nude mice, the ER expression in the resistant line remained unchanged. The tamoxifen sensitive and -resistant breast carcinoma 3366 differed, additionally, in their immunoreactivity of ER to mAB H222. While an incubation with estradiol or tamoxifen of immobilized ER prepared from cytosols of the sensitive tumors 3366 led to a significant increase in immunoreactivity, samples of resistant tumors failed in the exposition of additional immunologically reactive epitopes. These results were the basis for the development of an assay for determination of the tamoxifen response in patients. Our retrospective results with 38 breast tumors from a tumor bank indicated that patients with an increase of immunoreactivity of ER more rarely had a recurrence while under going tamoxifen therapy compared with patients expecting no increase. However, the data indicate interesting changes occurring with the ER of tam-resistant tumors that are to be explained by further mutational or protein-chemical analysis.

Development and characterization of a tamoxifen-resistant breast carcinoma xenograft.

A human tamoxifen-resistant mammary carcinoma, MaCa 3366/TAM, originating from a sensitive parental xenograft 3366 was successfully established by treatment of tumour-bearing nude mice with 1-50 mg kg(-1) tamoxifen for 3 years during routine passaging. Both tumours did not differ significantly in OR- and PR-positivity, however, when compared with the sensitive tumour line, the mean OR content of the TAM-resistant subline is slightly lower. An OR-upregulation following withdrawal of oestradiol treatment was observed in the parental tumours but not in the resistant xenografts. Following long-term treatment with tamoxifen, the histological pattern of the breast carcinoma changed. The more differentiated structures being apparent after treatment with 17beta-oestradiol in the original 3366 tumour were not induced in the resistant line. Tamoxifen failed to induce a tumour growth inhibition in comparison to the tamoxifen-sensitive line. The pure anti-oestrogen, ICI 182 780, revealed cross-resistance. Sequence analysis of the hormone-binding domain of the OR of both lines showed no differences, suggesting that either mutations in other regions of the OR are involved in the TAM-resistance phenotype or that mechanisms outside of this protein induced this phenotype. Oestrogen and anti-oestrogen regulate pS2 and cathepsin D expression in 3366 tumours as in the human breast cancer cell line MCF-7. The resistant 3366/TAM tumours have lost this regulation. The established breast cancer xenografts 3366 and 3366/TAM offer the possibility of investigating mechanisms of anti-oestrogen resistance in an in vivo situation. They can be used to test novel approaches to prevent, or to overcome, this resistance in a clinically related manner.

Anticancer drug sensitivity and expression of multidrug resistance markers in early passage human sarcomas.

We have established new human sarcoma lines and examined their sensitivity to common antitumor drugs and expression of putative multidrug resistance (MDR) proteins. Eighty-two sarcoma samples were transplanted in nude mice. Fourteen of these sarcomas were established as tumor cell lines. We determined a chemosensitivity profile to antitumor drugs (MDR drugs = doxorubicin, mitoxantrone, and vincristine; non-MDR drugs = cisplatin, ifosfamide, and bleomycin) for each tumor line in vivo. Response to chemotherapy with doxorubicin and ifosfamide was observed in 30-50% of these tumor lines. Our results obtained with xenotransplants are similar to the results documented in clinical trials in which doxorubicin and ifosfamide are effective in 30-50% of the patients. Furthermore, we examined expression of MDR-relevant markers like P-glycoprotein, MDR-associated protein, lung resistance protein, and mdr1 mRNA in these xenotransplants. A relationship between mdr1 mRNA expression and response to doxorubicin was demonstrated in >90% of our tumor lines. In six sarcomas with mdr1 mRNA expression, five were resistant against doxorubicin and cross-resistant against several other drugs, whereas from eight sarcomas, which lacked detectable mdr1 mRNA, seven were sensitive to doxorubicin and other drugs. We found lung resistance protein or MDR-associated protein expressed in three resistant and mdr1 mRNA-positive sarcomas. These results demonstrate that mdr1 mRNA expression is a putative marker for drug resistance in our sarcoma lines. We conclude, therefore, that inherent P-glycoprotein expression might be also responsible for drug resistance occurring in treatment of patients with sarcomas. The established tumor lines are useful for additional investigations on mechanisms of drug resistance in sarcomas and as models for preclinical screening of new antitumor drugs.

Reverse transformation of human mammary carcinoma cells.

Exposure of cells derived from human mammary carcinoma cell line, MaTu, to daunorubicin started a selection process which reproducibly gave rise to sublines with different phenotypes. One subline exhibited a fibroblast-like morphology (MaTu/c7), while others retained the epitheloid phenotype of the parental cells (MaTu/p). Among the latter was clone 8 (MaTu/c8) which displayed piling-up structures not seen in MaTu/p cells. Striking differences were detected on immunocytochemistry using the anti-cytokeratin 19 antibody A53-B/A2 which positively reacted with cells from MaTu/c7, but not with those of MaTu/c8 and MaTu/p. In contrast, the anti-blood group H 2 antibody A46-B/B10 positively stained cells from MaTu/c8 and MaTu/p, but not those of MaTu/c7. Assays for tumorigenicity in nude mice demonstrated that MaTu/c7 is far less tumorigenic than MaTu/p, while MaTu/c8 showed a pattern distinguishing it from MaTu/p cells. Cross-resistance assays showed decreasing drug resistance in the order MaTu/c8 > MaTu/c7 > MaTu/p. These data suggest drug-induced differentiation with reversion of the neoplastic phenotype in MaTu/c7 and some form of malignant progression in MaTu/c8. This model system may be helpful for understanding cancer development, especially its relation to differentiation.

Reconstitution of mammary gland development in vitro: requirement of c-met and c-erbB2 signaling for branching and alveolar morphogenesis.

We have established a cell culture system that reproduces morphogenic processes in the developing mammary gland. EpH4 mouse mammary epithelial cells cultured in matrigel form branched tubules in the presence of hepatocyte growth factor/scatter factor (HGF/SF), the ligand of the c-met tyrosine kinase receptor. In contrast, alveolar structures are formed in the presence of neuregulin, a ligand of c-erbB tyrosine kinase receptors. These distinct morphogenic responses can also be observed with selected human mammary carcinoma tissue in explant culture. HGF/SF-induced branching was abrogated by the PI3 kinase inhibitors wortmannin and LY294002. In contrast, neuregulin- induced alveolar morphogenesis was inhibited by the MAPK kinase inhibitor PD98059. The c-met-mediated response could also be evoked by transfection of a c-met specific substrate, Gab1, which can activate the PI3 kinase pathway. An activated hybrid receptor that contained the intracellular domain of c-erbB2 receptor suffices to induce alveolar morphogenesis, and was observed in the presence of tyrosine residues Y1028, Y1144, Y1201, and Y1226/27 in the substrate-binding domain of c-erbB2. Our data demonstrate that c-met and c-erbB2 signaling elicit distinct morphogenic programs in mammary epithelial cells: formation of branched tubules relies on a pathway involving PI3 kinase, whereas alveolar morphogenesis requires MAPK kinase.

Role of morphogenetic factors in metastasis of mammary carcinoma cells.

We have analysed the role of the morphogenetic factors hepatocyte growth factor/scatter factor (HGF), neuregulin and E-cadherin in the process of metastasis and morphogenesis of mammary carcinoma cells. The cDNAs for HGF, neuregulin and E-cadherin were stably expressed in anaplastic human MDA MB 435 carcinoma cells. The altered cells were then injected into the mammary fat pads of nude mice, where they form tumors which can spontaneously metastasize to the lungs. We found that expression of HGF or neuregulin promoted metastasis whereas expression of the cell adhesion molecule E-cadherin was inhibitory. Moreover, expression of E-cadherin reconstituted the ability of the cells to form morphogenetic structures in matrigel cultures in response to HGF. These data demonstrate that HGF and neuregulin, which control branching or lobulo-alveolar morphogenesis of normal breast epithelium, do have metastasis-promoting effects on breast carcinoma cells. Moreover, our results suggest that the differential activities of the two factors can be explained by the degree of epithelial differentiation: induction of morphogenesis requires an intact epithelial adhesion and differentiation system, whereas induction of metastasis is observed when the cells have lost their epithelial characteristics.

Expression of CD44 standard and isoforms in human breast cancer xenografts and shedding of soluble forms into serum of nude mice.

Standard CD44 (CD44s) and variant isoforms (CD44v) are expressed on different malignant cells and tissues. Their upregulation has been implicated, in the progression and metastasis of malignomas. In this work we addressed the question of whether these molecules are also expressed on xenografted human breast carcinomas and if certain expression patterns are correlated with biological parameters like tumour size, hormone receptor status, histology, growth rate, chemoresistance and microenvironment. Additionally, we were interested in the shedding of soluble CD44 (sCD44) into the blood circulation of tumour bearing nude mice. The human breast carcinomas MCF-7, MCF-7/ADR, 4296 and MDA-MB435, 4134 and 4151 were transplanted subcutaneously (sc.) or into the mammary fat pad (mfp.) of nude mice. The expression of the CD44s, -v6, and -v9 isoforms was determined at different time points on tissue samples by immunohistochemistry or RT-PCR employing human-specific antibodies or primers, respectively. The serum concentration of CD44s and -v6 was measured by human specific ELISAs. All tumours expressed CD44s. The lowest level was observed in the MCF-7 cancer. The CD44v6 and -v9 sequences and epitopes were distinctly expressed in MCF-7/ADR. MDA-MB435, 4134, 4151 and 4296, while MCF-7 lacked these isoforms. The highest serum concentration of the v6 isoform was detected in mice bearing the tumour 4296 with a high tendency for lymphogenic metastasis. The serum levels of sCD44 were in 5/6 xenografts linearly correlated with the tumour size. Interestingly, there was a remarkable difference between the two sublines MCF-7 and MCF-7/ADR: Both the tissue and serum levels of CD44 isoforms indicated that the development of multidrug resistance is accompanied by an alteration in the expression of membrane proteins discussed to be involved in metastasis. There was no relation of tissue expression with the transplantation site and the hormone receptor status of the tumour lines. CD44s and its variant isoforms are expressed in human xenotransplanted breast cancers in very different levels and patterns. The highest expression in the tumour 4296 is related to lymphogenic metastasis while the absence of isoforms in the model MCF-7 is related to non-metastatic behaviour. CD44 is shed into the serum and can be used for monitoring of tumour growth.

Development and characterisation of novel human multidrug resistant mammary carcinoma lines in vitro and in vivo.

Clinical chemotherapy of breast carcinomas must be considered insufficient, mainly due to the appearance of drug resistance. The multidrug resistance (MDR) phenotype, either intrinsically occurring or acquired, e.g., against a panel of different antineoplastic drugs, is discussed in relation to several MDR-associated genes such as the MDR-gene mdr1 encoding the P-glycoprotein (PGP), the MRP gene (multidrug resistance protein) encoding an MDR-related protein or the LRP gene encoding the lung resistance protein. Numerous experimental and clinical approaches aiming at reversing resistance require well-characterised in vitro and in vivo models. The aim of our work was to develop multidrug resistant sublines from human xenotransplanted breast carcinomas, in addition to the broadly used line MCF-7 and its multidrug resistant subline MCF-7/AdrR. MDR was induced in vitro with increasing concentrations of Adriablastin (ADR) for several weeks, resulting in a 3.5- to 35-fold increase in IC50 values using the MTT-test. Cell lines were cross-resistant toward another MDR-related drug, vincristine, but remained sensitive to non-MDR-related compounds such as cisplatin and methotrexate. The resistance toward Adriamycin and vincristine was confirmed in vivo by a lack of tumour growth inhibition in the nude mouse system. Gene expression data for the mdr1/PGP, MRP/MRP and LRP/LRP on both the mRNA (RT-PCR) and the protein levels (immunoflow cytometry) demonstrated that induction of mdr1 gene expression was responsible for the acquired MDR phenotype. Rhodamine efflux data, indicated by PGP overexpression, underlined the development of this MDR mechanism in the newly established breast carcinoma lines MT-1/ADR, MT-3/ADR and MaTu/ADR.

Role of HGF/SF and c-Met in morphogenesis and metastasis of epithelial cells.

We have analysed the role of hepatocyte growth factor/scatter factor (HGF/SF) in the process of morphogenesis and metastasis of epithelial (carcinoma) cells. HGF/SF induces various morphogenic responses in epithelial cells that derive from different tissues when these are grown in three-dimensional gels, e.g. branching tubules in kidney, breast, and prostate epithelial cells, crypt-like structures with brush border in colon epithelial cells, and alveolar-like aggregates in lung and pancreas cells. Epithelial cells are thus able to form complex structures in vitro which resemble the structures formed in the organ they originate from. We also examined the response of human breast carcinoma cells to HGF/SF in vivo. MDA MB 435 cells transfected with HGF/SF were injected into the mammary fat pad of nude mice, where they form tumours which spontaneously metastasize to the lungs. We found that expression of HGF/SF promoted metastasis whereas expression of the cell adhesion molecule E-cadherin was inhibitory. Moreover, expression of E-cadherin reconstituted the ability of the cells to form complex structures in response to HGF/SF in vitro. These data demonstrate that the different responses to HGF/SF depend on the state of the epithelial cells: morphogenesis requires epithelial differentiation and cell polarity, whereas metastasis is observed when the cells have lost their epithelial characteristics. Moreover, we have recently identified Gab-1 as a direct-binding substrate of the c-Met receptor. Gab-1 binds to c-Met phosphorylated on tyrosine residues, but not to a number of other tyrosine kinases from different subfamilies. A newly identified proline-rich domain of Gab-1 is responsible for the binding to the bidentate docking site in c-Met. Expression of Gab-1 in epithelial cells is sufficient to induce c-Met-specific cellular responses which include the formation of branching tubules. Thus, Gab-1 seem to correspond to the substrate of the c-Met receptor tyrosine kinase that mediates the epithelial morphogenesis.

Relation of oestradiol-mediated growth stimulation with the expression of c-erbB-2 protein in xenotransplanted oestradiol-receptor-positive and -negative breast carcinomas.

Attempts were made to correlate growth effects induced by oestradiol and tamoxifen with the hormonal regulation of c-erbB-2 protein in experiments in vivo. We report here the responsiveness of four xenotransplanted oestrogen-receptor(ER)-positive and four ER-negative human mammary carcinomas to oestradiol and tamoxifen. Oestradiol in a dose of 0.5 mg/kg significantly increased the growth of the ER-positive mammary carcinomas 3366, MCF-7, 4134 and 4049, but not the ER-negative tumours 4000, 4296 and MT-3. However, within the group of the ER-negative breast carcinomas the tumour 4151 ES deviates from this growth behaviour, as we could prove an estrogen induced growth. The stimulation of tumour growth by oestradiol was always accompanied by a down-regulation of c-erbB-2 protein both in the ER-positive mammary carcinomas and in the ER-negative mammary carcinoma 4151 ES. Tamoxifen significantly inhibited the growth of the ER/PR-positive mammary carcinomas 3366 and MCF-7 but not the ER-positive/PR-negative mammary carcinomas 4049 and 4134. In the group of ER-negative mammary carcinomas only the growth of the oestrogen-responsive tumour 4151 ES was significantly inhibited by tamoxifen. The inhibition of tumour growth by tamoxifen was correlated with a reversion of the oestradiol-induced down-regulation of c-erbB-2, also in the ER-negative/oestradiol-responsive mammary carcinoma 4151 ES. From our results we hypothesize that the oestrogen-dependent growth of ER-negative breast carcinoma 4151 ES could also be correlated with the oestradiol-regulated expression of c-erbB-2 protein.

Influence of liposomes rich in unsaturated or saturated fatty acids on the growth of human xenotransplanted mammary carcinomas and on the levels of heart type fatty acid binding protein.

A panel of 4 human mammary carcinomas passaged in nude mice were subjected to intraperitoneal application of cholesterol-free liposomes enriched with linoleic (unsaturated fatty acid) or stearic acid (saturated fatty acid). The liposomes were examined with regard to their influence on the tumor growth and level of heart type fatty acid binding protein (FABP). Liposomes with different fatty acid composition influenced the growth of mammary carcinomas 3366, BO, 4000 and 4151 in distinct ways. Liposomes with a high content of stearic acid significantly inhibited the growth of mammary carcinomas 3366 and BO, whereas mammary carcinomas 4000 and 4151 were not affected. The growth of mammary carcinoma 3366 was moderately increased after supplementation of liposomes rich in linoleic acid, the tumor BO was significantly inhibited and the growth of MaCa 4000 and 4151 was unchanged. Liposome treatment led to a significant increase in heart type FABP in mammary carcinomas 3366 and BO regardless of whether the animals were treated with liposomes rich in stearic or linoleic acid. Such significant changes of FABP level could not be observed in mammary carcinomas 4000 or 4151. We suggest that the lipid-mediated growth modulation seems to be dependent on an increase of heart type FABPs in these tumor models.

Carboplatin-liposomes (CPL) in immunodeficient mice: improved antitumor activity for breast carcinomas and stimulation of hematopoiesis.

Carboplatin-liposomes (CPL) have been shown to possess a strong stimulatory activity on the hematopoiesis in immunocompetent mice. As we were interested in studying this pharmacological characteristic in parallel with any antitumour effects which might be expected for the encapsulated cytostatic, we used a panel of six human breast carcinomas xenotransplanted to nude mice. The antitumor activity as well as the hematopoietic effects of the vesicles were studied in comparison to, and in combination with, the free drug. Carboplatin was encapsulated into reverse phase evaporation vesicles (REV) and injected i.p. as a single dose of 75 mg kg-1 into tumor-free and breast-carcinoma-bearing animals, respectively. Following a single application of CPL in nude mice, a significant increase of the WBC numbers to about three times for that of the normal level could be observed over a period of at least 28 days. The elevation was due to an increase in both circulating granulocytes and lymphocytes. The peripheral effect was accompanied by a relative decrease of spleen cellularity, while the number of bone marrow cells was hardly affected. There was no influence detectable on circulating blood cells in SCID mice. However, a rather high toxicity of CPL for this immunodeficient mouse strain was noticed. In the panel of breast carcinomas used, free carboplatin and CPL displayed a different pattern of therapeutic efficiencies. In four of the five tumor models tested, a combination of the free with the liposomal drug showed a significant inhibition of tumor growth while effectively preventing a drug-induced leukopenia.(ABSTRACT TRUNCATED AT 250 WORDS)

Establishment and characteristics of two new human mammary carcinoma lines in nude mice with special reference to the estradiol receptor status and the importance of stroma for in vivo and in vitro growth.

Two new human mammary carcinoma lines originating from surgical material were established in nude mice. According to the adopted criteria, the tumor 4049 has been classified as estradiol receptor positive and mammary carcinoma 4296 as estradiol receptor negative. Both tumors proved to be c-erbB-2 protein positive and EGF-receptor negative. In contrast to carcinoma 4296, the in vitro growth and the take rate of mammary carcinoma 4049 in nude mice seems to be dependent on stromal components. Pretreatment of mice with estradiol/peanut oil before tumor engraftment was an essential precondition for the growth of the primary tumor in nude mice. After successful establishment the tumor growth was significantly stimulated by estradiol. The growth rate of mammary carcinoma 4296 was independent of any supplementation of estradiol. The two breast tumors were characterized with regard to their growth behaviour, histology, and sensitivity to cytostatics and antihormones. They are considered suitable tumor models for the testing of antineoplastic substances and for biological experiments.

Antineoplastic activity of alkylphosphocholines (APC) in human breast carcinomas in vivo and in vitro; use of liposomes.

This study examines the in vitro and in vivo activity of alkylphosphocholines (APC) in experimental human breast carcinomas. Three analogs, hexadecylphosphocholine (HPC), octadecylphosphocholine (OPC) and eicosanylphosphocholine (EPC) were investigated. Three hormone receptor negative cell lines were sensitive to all three APCs in vitro whereas the receptor positive MCF-7 line was more resistant. Sensitivity was seen in 4/6 hormone receptor negative tumors in vivo, with HPC being the most active analog. There were no antitumor effects in the four receptor positive models. The reasons for these differences in response between hormone receptor negative and -positive lines are not yet understood and require further study. Gastrointestinal toxicity and hemolysis, the major side effects of the APCs, were reduced by the use of liposomal preparations.

Wild-type p53 is not involved in reversion of the tumorigenic phenotype of breast-cancer cells after transfer of normal chromosome-17.

A number of different candidate tumor suppressor genes involved in human breast cancer are presumed to be located on chromosome 17. To verify the relevance of chromosome 17 abnormalities in breast cancer cells, a normal human chromosome 17 was transferred by microcell fusion to R30 tumor cells derived from an infiltrating ductal mammary carcinoma. The tumorigenicity of the microcell hybrids in nude mice was examined. The tumor volume obtained with different clones was reduced by up to 94% of the value corresponding to the parental tumor cells. This effect was accompanied by a reduction of anchorage-independent growth, as well as cell growth rates on plastic plates. These effects were independent of the continued presence of a transferred 17q arm and could not be attributed to the action of the normal p53 gene. The results support the assumption that in addition to p53 a further tumor suppressor gene is located on 17p which is involved in breast cancer.

Establishment and characteristics of two new human mammary carcinoma lines serially transplantable in nude mice.

Two human mammary carcinomas of postmenopausal women were successfully transplanted into nude mice. Both tumours were classified as epidermal-growth-factor-, oestradiol- and progesterone-receptor-negative and c-erbB2-protein-positive. Histological studies of the primary tumours (4000 and 4151) revealed ductal invasive mammary carcinomas. In the first passages the precondition for the growth of breast carcinoma 4000 were pretreatments of the nude mice with oestradiol and peanut oil before transplantation. The mammary carcinomas 4000 and 4151 described here are suitable for in vivo testing of antineoplastic substances and for biological studies.

Establishment and characterization of a new human oestradiol- and progesterone-receptor-positive mammary carcinoma serially transplantable in nude mice.

A human mammary carcinoma originating from a postmenopausal patient was successfully transplanted into nude mice. According to the adopted criteria the tumour proved to be oestradiol- and progesterone-receptor-positive. Histological studies of the patient tumour revealed a ductal invasive mammary carcinoma with 80% tubular growth pattern. Following transplantation the adenoid structures decreased to 30%; the mitosis rate and grade of malignancy increased. Treatment of the nude mice with 20 micrograms oestradiol benzoate/mouse caused a loss of the oestradiol receptor of the mammary carcinoma. The mammary carcinoma 3366 can be used for testing of antineoplastic substances, antihormones and for studies in regard to down-regulation or blocking of hormone receptors and possible consequences for therapies.

Characterization of two human mammary carcinomas, MT-1 and MT-3, suitable for in vivo testing of ether lipids and their derivatives.

The human mammary carcinomas MT-1 and MT-3 originate from surgical material and were transplanted in nude mice. Both tumors have been classified as estradiol- and progesterone receptor-negative. Therapeutic doses of hormones and anti-hormones remained without growth inhibitory effect. MT-1 and MT-3 proved to be sensitive to conventional cytostatic drugs used for treatment of mammary carcinomas; striking is their sensitivity to ether lipids. Therefore, they are considered suitable tumor models for this class of substances.

[Comparative studies of carcinomas of the human oral mucosa and xenografts in the nude mouse with the aid of computer-supported microscope image analysis]. / Vergleichende Untersuchungen zwischen humanem Mundschleimhautkarzinom und Xenotransplantaten auf der Nude-Maus mit Hilfe der computergestützten Mikroskopbildanalyse.

The complete preservation of the original characteristics of donor tumors after xenografting into nude mice is more and more doubtful. With the aid of traditional biological methods and computer-assisted microscope image analysis the original human tumor tissues, including primary and recurrent tumors and metastases, are compared with nude mouse-grown xenografts. Squamous cell carcinomas of the oral mucosa served as original tumor tissues. Tumor takes were observed in 7 out of 12 cases. 5 transplantable lines could be established. Primaries, recurrent tumors and lymph node metastases are suitable for transplantations into nude mice and yield a comparable success rate. With one exception complete conformity between the original human tumor tissues and nude mouse-grown tumors could be found regarding the degree of differentiation and keratinizing tendency. As to the growth pattern of xenografts characterized by continuous shortening of growth periods, certain variations in the biological properties due to selection processes cannot be excluded. The results of microscope image analysis based on 35 different parameters suggest important differences within the developmental tendency of human tumor tissues and nude mouse-grown xenografts.