Expression of metastatic potential of tumor cells in young nude mice is correlated with low levels of natural killer cell-mediated cytotoxicity

Model of human transitional cell carcinoma: tumor xenografts in upper urinary tract of nude rat

An in vivo model for the study of human transitional cell carcinoma (TCC) in the urinary tract is desirable. Orthotopic xenografts are useful in order to approximate better the behavior of human tumor cells in situ. Prior models have been described in the urinary bladder of the nude mouse and rat. We have developed the first model of implantation of human TCC in the upper urinary tract of an experimental animal. The kidneys of homozygous nude rats 4 weeks of age were inoculated with 1-5 x 10(6) cells of the RT4 well-differentiated papillary human TCC line through bilateral flank incisions, with transparenchymal injection of tumor cells into either the collecting system (renal pelvis) or the parenchyma. The overall implantation rate was 92% (54/59 kidneys). However, implantation into the collecting system occurred in only 45% (18/45) of the group. Ligation of the ureter prior to inoculation to produce urine stasis improved the mucosal implantation rate. Despite suspect urine cytology findings in the renal pelvis injection group, no distal seeding of the urinary tract was seen. Intraparenchymal tumor growth was less differentiated and had a higher fraction of mitotic cells than mucosal tumors. Vascular and lymphatic invasion were commonly seen; however, distant metastasis was not observed. This model will prove useful in determining the role of seeding in recurrent disease and in developing less invasive modalities for the treatment of upper tract TCC.

Alcohol consumption suppresses metastasis of B16-BL6 melanoma in mice

Female C57BL/6 mice were fed a defined, pelleted diet and given 10% w/v or 20% w/v ethanol in their drinking water. Natural killer (NK) cell cytolytic activity was compared between water-drinking and ethanol-consuming mice and in mice that were also treated with polyinosinic-polycytidylic acid (poly I:C) to augment NK cell activity or with anti-NK1.1 antibody to decrease activity. NK cell cytolytic activity was not altered in mice given 10% ethanol, but was decreased in mice given 20% ethanol compared to water-drinking mice. Poly I:C treatment increased and anti-NK1.1 antibody treatment decreased NK cell activity in both water-drinking and 20% ethanol-consuming mice. Experimental and spontaneous metastases of B16-BL6 melanoma were evaluated as a function of the duration of ethanol consumption before tumor inoculation and as a function of altered NK cell activity. Experimental metastasis was inhibited after 4 and also after 6.5 weeks of ethanol exposure. Poly I:C treatment inhibited tumor lung colonization irrespective of ethanol consumption. Anti-NK1.1 antibody treatment increased metastasis, although to a lesser degree in mice consuming 10% ethanol. Spontaneous metastasis was inhibited in mice consuming 10% ethanol for 4 weeks, and in mice consuming 20% ethanol for 1 and 4 weeks before melanoma inoculation.

The plasminogen-plasmin system in malignancy

The study of the plasminogen-plasmin system has, in the past, contributed much to the understanding of fibrinolysis and thrombolysis. Attention is now focused on the role of the components of this system in many biologic functions. Findings of uPA, its receptor and its inhibitor in many tumor tissues and tumor cell lines, strongly implicate their involvement in tumor invasion, tumor cell proliferation and metastasis. The characteristics of the plasminogen activators, the uPA receptor and the plasminogen activator inhibitors as well as their expression and regulation in tumors and tumor cell lines are reviewed.

Metastatic potential of human renal cell carcinoma: experimental model using subrenal capsule implantation in athymic nude mice

The aim of this study was to determine whether subrenal capsule (SRC) implantation is a suitable model for the study of the metastatic potential of our human renal cell carcinoma (HRCC) lines and to establish new sublines with enhanced metastatic ability. NMRI athymic nude mice 7-11 weeks old received SRC implantation of our HRCC lines RC43 and RC21. These lines were not metastatic when implanted s.c. Mice were killed after 4 or 8 weeks, or when moribund. With the RC43 cell line the success rate for implantation was 69%, with 89% of these showing metastases. The average volume of the implanted tumour fragments was 0.5 mm3 (range 0.28-0.7), the average volume at the primary site at the time of death was 9087 (9-32000) mm3. Metastases were found in lymph nodes, liver, spleen, peritoneum, psoas muscle, pancreas, diaphragm and skin. The average volume of the metastases was 4139 (0.5-9000) mm3. Growing cell lines were established in vivo and in vitro from one splenic, one peritoneal, one diaphragmatic, and one hepatic metastasis. These sublines have faster in vivo and slower in vitro growth rates than the parental lines. With the RC21 cell line the success rate for implantation was 56% and the metastatic rate 78%. The average volume of the implanted tumour was 0.8 mm3 (0.28-1.2), the average volume at the primary site at the time of death was 2685 mm3 (1.4-6534) and the average volume of metastases was 7.1 mm3 (0.5-37.5). Metastases were found in lymph nodes, lung and skin. No establishment was attempted for RC21 because of the small dimensions of these metastases.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparative studies between nude and scid mice on the growth and metastatic behavior of xenografted human tumors

The growth and metastatic behavior of three human tumor cell lines and a human colon carcinoma previously passaged in vivo were compared between nude mice and scid mice after xenotransplantation. The three human tumor lines included a bladder carcinoma (T24B), a melanoma (RPMI 7931) and a lacZ gene-transduced breast cancer (MDA-MB-435 BAG). The lacZ gene codes for beta-galactosidase, which can be stained blue with chromogenic substrate X-gal, thus allowing the highly sensitive detection and quantitative examination of human cancer metastasis in host mice. Adult (7-14 weeks) NMRI nude and C.B-17 SCID mice were inoculated with 0.5-5 x 10(6) tumor cells s.c. Comparable take rate, latent period and growth rate of implanted tumors were observed in nude and scid mice for each of the cell lines tested. At the time of autopsy, which varied from 6 to 11 weeks after inoculation, a significantly higher incidence of spontaneous lung metastasis was discovered in scid mice (96%) than in age-matched nude mice (27%, total P less than 0.001). In vitro assays for NK cell-mediated cytotoxicity revealed no significant differences between the two strains of mice. Our results suggest that nude and scid mice are equally suitable for propagating human tumors. However, the metastatic capacity of human tumor cells appears to be better expressed in scid mice. Scid mice may therefore provide an advantageous model for the study of human tumor metastasis.

Experimental metastasis of oncogene-transformed NIH 3T3 cells in chick embryo

By means of a highly sensitive and quantitative assay for specific detection of metastasized tumor cells in chick embryonic organs using the polymerase chain reaction (PCR), we have examined the experimental metastatic ability of individual clones of NIH 3T3 cells, transformed with oncogenes: v-Ki-ras, v-Ha-ras, v-src, v-fos, and v-abl. Such a transformed clone had different metastatic abilities in different embryonic organs. Among them, two clones of NIH 3T3 cells transformed with ras-oncogenes (v-Ki-ras or v-Ha-ras) metastasized to liver and lungs of chick embryo, and grew there more rapidly than the other clones. The parental NIH 3T3 cells were detected as slight bands of PCR products after iv injection, indicating some cells were trapped in chick embryonic organs, but did not grow. These findings indicate that the transformed cells are able to invade the organ tissues and grow in embryonic chick organs, but non-metastatic cells such as the untransformed-NIH 3T3 cells are not able to grow in the secondary sites. These experiments clearly demonstrate the usefulness of this assay system to study genes involved in malignant transformation.

Effects of bacillus Calmette-Guerin on cytotoxic activities of peripheral blood lymphocytes against human T24 lined and freshly isolated autologous urinary bladder transitional carcinoma cells in patients with urinary bladder cancer

The effects of bacillus Calmette-Guerin (BCG) on the cytotoxic activities of peripheral blood lymphocytes against human T24 lined and freshly separated autologous urinary bladder transitional carcinoma cells in patients with urinary bladder cancer were analyzed in a 12-hour chromium 51 (51Cr) release assay. The results of this study indicate that BCG activates the tumor killing system through stimulation of effector cells and elevation of target cell susceptibility in patients with urinary bladder cancer, suggesting that BCG-augmented cytotoxicity may be oriented specifically to urinary bladder cancer cells. This could explain the remarkable clinical benefits of intravesical instillation of BCG against urinary bladder cancer.

Isolation and characterization of PC-3 human prostatic tumor sublines which preferentially metastasize to select organs in S.C.I.D. mice

We have developed and partially characterized a mouse model system for studying human prostate tumor cell metastases in vivo. To develop this model we have selected highly invasive (3 x I.) and non-invasive (3 x N.I.) PC-3 human prostatic tumor sublines based on enhanced and diminished capacities to migrate across a reconstituted basement membrane barrier (Matrigel) in Boyden chamber chemotactic assays. When the 3 x I. cells were injected intravenously (i.v.) in the tail vein of severe combined immune deficient (scid) mice, the cells initially metastasized to a wide variety of tissues as demonstrated by using [125I] IUdR labeled cells and histology. Four distinct sublines were eventually isolated which preferentially metastasized at approximately 80% efficiency to the lumbar vertebrae (PC-3 ML), the mandibular region of the right cheek (PC-3 MC), the rib cartilage (PC-3 MR), and the right front knee bone (PC-3 MK), respectively. Implantation experiments at different sites indicated that organ metastases may somehow be conferred on the tumor subclones by the host tissue.

Natural killer-cell activity under conditions reflective of tumor micro-environment

Natural-killer(NK) activity was examined in the presence of low oxygen tension, low glucose concentration and acidic pH, to determine whether physical conditions present in the tumor micro-environment could play a role in down-regulating cytolytic activity of tumor-infiltrating lymphocytes with NK phenotype. Anoxia (0% O2), but not hypoxia (1% O2), significantly reduced NK activity, as did acidic pH (6.4 or 6.7). Low glucose concentration (6 mg/dl) did not impair NK activity. Combinations of either moderate (1% O2, 26 mg/dl glucose, pH 6.7) or extreme (0% O2, 6 mg/dl glucose, pH 6.4) alteration of physical conditions significantly reduced NK activity. This study indicates that the physico-chemical conditions present within solid tumors are capable of down-regulating NK activity.

The mechanism of action of a synthetic immunomodulator, 3,6-bis(2-piperidinoethoxy)acridine trihydrochloride (CL 246,738), in natural killer cell activation in animals

CL 246,738 is a low molecular weight, synthetic immunomodulator. The present study was done to determine the interaction among interferon (IFN), macrophages, and natural killer (NK) cells in mice following oral administration of CL 246,738. Splenic NK activity as evidenced by lysis of YAC-1 lymphoma cells in vitro was found to be augmented by the compound not only in normal mice, but also in immunodeficient beige and nude mice. Lytic activity remained elevated from one to seven days after a single treatment and the peak activation varied depending on the source of NK cells. NK cell activity associated with the peritoneal exudate cell population peaked at day 1 and returned to normal by day 2, whereas NK cell activity of peripheral blood lymphocytes peaked at day 3 and remained significantly elevated until day 7. Liver associated NK activity peaked at day 4 and remained significantly elevated at day 7 after treatment with CL 246,738. Lung associated NK activity was elevated by day 1 after treatment, peaked at day 4 and returned to normal by day 7 after drug administration. The drug was also effective in inducing IFN in all mouse strains tested. When these drug-treated mice were given antibody to IFN-(alpha + beta) but not to IFN-(beta), both IFN levels and NK cell activity decreased, suggesting the importance of IFN-(alpha) in this system. Furthermore, mice that had received carrageenan prior to, but not after CL 246,738 administration showed reduced serum IFN titers as well as decreased NK cell activity, indicating that macrophages played an intermediate role in immune enhancement by the drug.(ABSTRACT TRUNCATED AT 250 WORDS)

A new rat colon cancer cell line metastasizes spontaneously: biologic characteristics and chemotherapeutic response

A new cell line (RCN-9) was established in culture from a transplantable rat colon adenocarcinoma, which was induced in the colon of a male Fischer F344 rat by subcutaneous administration of 1,2-dimethylhydrazine. When RCN-9 cells were injected subcutaneously or into the cecal subserosa of syngeneic rats, carcinomas with progressive growth were obtained and the development of lung (63.6%) and liver (40.0%) metastases, respectively, ensued. Antitumor effects of 5-fluorouracil (5-FU), adriamycin (ADM) and mitomycin C (MMC) against RCN-9 were examined in vivo and in vitro. 5-FU and ADM had antitumor effects both in vivo and in vitro; MMC had antitumor effects in vitro. These results show that the RCN-9 cell line can be used both as a model to study mechanisms of metastasis from colon carcinoma and as a model in chemotherapeutic studies of metastatic disease from colon carcinoma.

Orthotopic implantation is essential for the selection, growth and metastasis of human renal cell cancer in nude mice [corrected]

Human neoplasms are heterogeneous for a variety of biological properties that include invasion and metastasis. The presence of a small subpopulation of cells with a highly metastatic phenotype has important clinical implications for diagnosis and therapy of cancer. For this reason, it is important to develop an animal model for the selection and isolation of metastatic variants from human neoplasms and for testing the metastatic potential of human tumor cells. We have implanted human renal cell carcinoma (HRCC) cells (obtained from a surgical specimen) into different organs of nude mice and then recovered the tumors and established each in culture. The 5 established lines differed in their biological-metastatic properties and had a unique karyotype, indicating that growth at different organs selects for different subpopulations of HRCC. Moreover, the HRCC did not metastasize unless they were implanted orthotopically. These findings indicate that the appropriate nude mouse model for studying the biology and therapy of HRCC must be based on the orthotopic implantation of tumor cells.

N-methylformamide affects spontaneous metastases of 3LL lines and increases natural killer activity of tumor-bearing mice

The antitumor activity of the polar solvent N-methylformamide (NMF) was evaluated on three lines derived from the Lewis lung carcinoma (3LL), endowed with different metastatic potential. Two administration schedules were tested, these being repeated regimens of NMF (200 mg/kg per dose) for 12 consecutive days, starting 24 h or 6-10 days after tumor implantation (early or late treatment, respectively). The results of the present work can be summarized as follows: (1) NMF regimens did not greatly affect tumor growth behavior of 3LL lines; conversely, they markedly influenced their spontaneous colonizing ability in the lungs, either by delaying early metastatic spread or by reducing the number and size of pulmonary metastases already implanted. (2) A significant increase of NK cell activity during and after early treatment with NMF was observed in the more-metastasizing lines, thus suggesting the possibility of an immunomodulating effect of NMF.

Reduction of metastasis in a murine mammary tumour model by heparin and polyinosinic-polycytidylic acid

A murine mammary tumour model has been used to test the efficacy of a combination of heparin and the interferon inducer, poly I:C on spontaneous metastasis from a s.c. primary tumour and on experimental metastasis following i.v. injection of tumour cells. This treatment has no effect on the growth of primary tumours, but lung metastases arising from these tumours were reduced. When tumour cells were injected i.v. the number of lung colonies was significantly reduced and survival time extended. Short-term treatment did not prevent the subsequent growth of extravasated, but dormant tumour cells, although mice treated for 8 or 12 weeks survived at least 6 months without any sign of lung colonies. Several mechanisms may contribute to the overall effect of this treatment; a reduction in the mitotic indices of lung colonies (observed in poly I:C treated mice) and also NK cells appeared to be important for the effectiveness of poly I:C since the reduction in experimental metastasis was abrogated by concomitant treatment with anti-asialo GM1 serum.

Inhibition of lung colonization of mouse colon 26 adenocarcinoma by recombinant mouse interferon beta through a modification of platelet function

Recombinant murine interferon beta (MuIFN-beta) given i.v. efficiently inhibited both pulmonary arrest and formation of lung colonies of NL-17, a highly metastatic variant of mouse colon adenocarcinoma 26. NL-17 was rather resistant to MuIFN-beta in vitro and was highly resistant to natural killer cells of mice even though they were treated in vivo with MuIFN-beta. Platelets isolated from MuIFN-beta-treated mice showed reduced aggregating activity induced by NL-17. Since lung colonization by NL-17 is influenced by platelet aggregation, the inhibition of colonization by MuIFN-beta could be partly mediated through modification of platelet function in vivo. The effect of MuIFN-beta on platelet function and its subsequent inhibition of lung colony formation give new insights into the action of recombinant MuIFN-beta.

Natural killer activity is present in rat lung lavage and inhibited by lidocaine

Natural killer (NK) cells play an important role in defense against tumors and certain infected cells. Although NK activity is present in cells recovered from lung parenchyma, its demonstration in cells retrieved from normal bronchoalveolar lavage (lung lavage) has been difficult. In this study, we report that NK cells are present and active in normal rat lung lavage. Purified effector cells retrieved from lung lavage and peripheral blood mononuclear cells were compared for NK activity. NK activity was tested in a four hour 51-chromium release assay against radiolabeled Yac-1 target cells and expressed as lytic units (LU). There was no difference in NK activity between the blood and lung (80 +/- 10 LU vs. 62 +/- 15 LU). Since lidocaine is used in lung lavage for topical anaesthesia in humans and to increase the cell yield in animals, we also sought to determine if it could affect NK activity. We found that lidocaine inhibited NK activity in a dose dependent manner when it was instilled into the airways prior to performance of lavage. Lidocaine did not affect the yield of cells recovered from lavage, their relative proportions, nor their viability. Lung macrophages (93 +/- 1% nonspecific esterase positive) inhibited blood NK activity, an effect significantly augmented by lidocaine. In sum, we report that NK activity in lung lavage is similar to that found in blood and may be regulated by alveolar macrophages and that topical lidocaine inhibits NK activity, an effect which needs to be considered in studies of these cells from lung lavage.

The nude mouse as a model for the study of human pancreatic cancer

The purpose of this study was to characterize an in vivo model of human pancreatic cancer suitable for chemotherapy and immunotherapy studies. In this study we report a 2-year experience in growing the MIA PaCa-2 (CRL 1420) human pancreatic cancer cell line in 92 adult (8 weeks old) and 256 young (3-6 weeks old) nude mice. Ten million tumor cells were transplanted into orthotopic (duodenal lobe of the pancreas) and/or heterotopic positions (hepatic and subcutaneous) and data on operative mortality, effect of total body irradiation (TBI), tumor growth kinetics, and survival are presented comparing the two age groups. Operative mortality was due to anesthetic intolerance which was higher in the young mouse population (13.4% versus 5.7%). Adult mice withstood TBI (500 rad) without mortality but young mice were highly sensitive to radiation damage and their maximum tolerated dose (LD50) was 425-450 rad. Subcutaneous tumors grew significantly more often in young compared to adult animals (97.9% versus 69%) and this finding was not affected by TBI (96.9% versus 75%), though tumors did appear more quickly after TBI. An average of 14.7 +/- 2.8 days was required for the subcutaneous tumors to become macroscopically apparent in the adult population compared with 3.1 +/- 0.8 days in the young mice. The largest subcutaneous tumor diameter 28 days following tumor implant averaged 9.3 +/- 0.6 mm in the young animals and 5.5 +/- 1.7 mm in the adult population (P less than 0.01). Treatment of young mice with human recombinant interleukin-2 (IL-2) (10,000 Units twice a day for 28 days) produced a 27% decrease in tumor growth. This effect was abolished by prior irradiation of the young mice with 375 rad TBI. Pancreatic tumor growth also occurred more consistently in young than in adult animals (91.2% versus 64.3%) and irradiation did not affect pancreatic tumor take in either group. Occasionally intrapancreatic tumor growth was associated with liver metastases in animals that were killed after 28 days (17.8% in young and 22.2% in adult animals). However, when more than 45 days elapsed before sacrificing the animals, the incidence of hepatic metastases increased to 57.1%. This was slightly less than the incidence of hepatic lesions found after direct injection of cancer cells into the liver by portal vein injection (71.4%). Direct extension of tumor into surrounding tissues was common with frequent involvement of the duodenum (83.7%), kidneys (30.6%), and other intraabdominal organs (43.9%). Survival was significantly longer in adult compared to young mice.(ABSTRACT TRUNCATED AT 400 WORDS)

Intraperitoneal tumor growth and chemotherapy in a rat model

Animal models are important to evaluate new treatment modalities. In the present paper a new animal model is described, in which the effects of intraperitoneal (i.p.) administration of cytostatic drugs on cancers restricted to the peritoneal cavity can be studied. The tumor cell line used is a chemically induced carcinoma (CC531), sensitive in vitro to cisplatin (cDDP), carboplatin (CBDCA), 5-fluorouracil (5-FU), doxorubicin and mitoxantrone. Three to 5 weeks after i.p. inoculation of 2 x 10(6) CC531 cells, 80% of Wag/Rij rats develop small tumor nodules on peritoneal surfaces. Both tumor size and localization at this time are comparable to the human situation, especially to cases of minimal residual disease ovarian carcinoma. The model has been used to determine the usefulness of i.p. treatment in comparison to i.v. Changing the route of administration of cDDP from i.v. to i.p. increases tumor platinum concentrations and prolongs survival. The model offers the possibility to study drug pharmacokinetics and tumor drug penetration related to i.p. drug administration.

alpha-Difluoromethylornithine inhibits liver metastasis produced by intrasplenic injection of human tumor cells into nude mice

The purpose of these studies was to examine metastatic potentials of a human colon tumor xenograft (T6) and three different human tumor cell lines (LS174T, HT29 and A549) using the intrasplenic-nude mouse model system (ISMS model system). A further objective was to study the activity of alpha-difluoromethyl-ornithine (DFMO) against primary and metastatic growth of the xenograft and the three cell lines. DFMO is an irreversible inhibitor of ornithine decarboxylase, a rate-limiting step in polyamine biosynthesis. Tumor burdens in the liver of nude mice were observed 6 weeks after the intrasplenic injection with LS174T and 12-14 weeks after intrasplenic injections with T6, HT29 and A549. Most of the mice developed primary tumor growth in the spleens. DFMO showed significant activity against liver metastases but had little or no activity against primary tumor growth in the spleens of the ISMS model and against s.c. growth of the xenograft. The studies demonstrated that the ISMS model system is an excellent system for studying metastatic behavior of human tumors and for studying the antimetastatic activity of experimental drugs.

Expression of human recombinant plasminogen activators enhances invasion and experimental metastasis of H-ras-transformed NIH 3T3 cells

The gene transfer technique was used to examine the role of plasminogen activator (PA) in the invasive and metastatic behavior of tumorigenic cells. H-ras-transformed NIH 3T3 clonal cells producing a very low level of PA were generated and further transfected with an expression plasmid containing a cDNA sequence encoding either the urokinase-type or the tissue-type human PA. Compared with the parental transformed cells, clonal cells expressing high levels of both types of recombinant PA invaded more rapidly through a basement membrane reconstituted in vitro. Furthermore, cells expressing high levels of recombinant urokinase-type PA also caused a higher incidence of pulmonary metastatic lesions after intravenous injection into nude mice. Both activities were reduced by the serine proteinase inhibitor EACA; invasion was also suppressed by antibodies blocking the activity of human PAs and by the synthetic collagenase inhibitor SC-44463. These findings provide direct genetic evidence for a causal role of PA in invasive and metastatic activities.

Natural resistance in mice against Friend cells injected intravenously. III. Comparison between in vivo and in vitro passaged interferon-sensitive (745) and interferon-resistant (3Cl8) cell clones

In vitro (FLC-Vt) or in vivo (FLC-V) passaged Friend erythroleukaemia cells of DBA/2 origin were tested for susceptibility to natural resistance (NR) in vivo or to NK cell activity in vitro. Scarcely oncogenic FLC-Vt cells were highly susceptible to in vivo NR (measured as rapid organ clearance or growth inhibition in lethally irradiated mice) or to in vitro NK attack. Conversely, highly oncogenic FLC-V cells were weakly susceptible to NR and to NK as well. These data seem to point out that natural immunity, which is up-regulated by endogenous or exogenous interferons, can play a significant role in surveillance against mouse leukaemic cells of retrovirus origin.

Expression of human recombinant plasminogen activators enhances invasion and experimental metastasis of H-ras-transformed NIH 3T3 cells

The gene transfer technique was used to examine the role of plasminogen activator (PA) in the invasive and metastatic behavior of tumorigenic cells. H-ras-transformed NIH 3T3 clonal cells producing a very low level of PA were generated and further transfected with an expression plasmid containing a cDNA sequence encoding either the urokinase-type or the tissue-type human PA. Compared with the parental transformed cells, clonal cells expressing high levels of both types of recombinant PA invaded more rapidly through a basement membrane reconstituted in vitro. Furthermore, cells expressing high levels of recombinant urokinase-type PA also caused a higher incidence of pulmonary metastatic lesions after intravenous injection into nude mice. Both activities were reduced by the serine proteinase inhibitor EACA; invasion was also suppressed by antibodies blocking the activity of human PAs and by the synthetic collagenase inhibitor SC-44463. These findings provide direct genetic evidence for a causal role of PA in invasive and metastatic activities.

Radioimmunolocation of hepatic and pulmonary metastasis of human colon adenocarcinoma

We have established a large library of monoclonal antibodies against a human hepatoma cell line called FOCUS. One such monoclonal antibody (SF-25) detects a 125-kilodalton cell surface antigen found on FOCUS cells. As both the liver and the colon are of endodermal origin, we examined the possibility of expression in colon adenocarcinomas. This antigen was found in all 23 colon adenocarcinoma tissues surgically obtained but was absent in the adjacent normal mucosal counterpart as determined by a direct radioimmunohistologic technique. In the present study, we have established a model for human metastatic colon adenocarcinoma using the LS 180 cell line. Athymic mice were further immunosuppressed by intravenous injection of anti-NK cell antibodies (antiasialo GM1). After 24 h, mice were injected with LS 180 cells either via the tail vein or into the spleen followed by splenectomy. Macroscopic pulmonary and lymphatic metastasis developed within 2-3 wk after injection of cells and 9 of 10 mice died with advanced metastatic disease 2-3 wk later. In addition, macroscopic hepatic metastases were evident in 4 of 5 mice 3-4 wk after intrasplenic injection. Both hepatic as well as pulmonary and lymphatic tumor spread was localized by nuclear imaging with 125I-SF-25. Furthermore, micrometastases were detected by autoradiography 5-10 days later. Monoclonal antibody SF-25 is a potential candidate for tumor localization and the experimental metastatic colon cancer animal model may be useful for treatment evaluation of monoclonal antibody SF-25 either alone or in combination with other monoclonal antibodies when conjugated to radionucleotides and chemotherapeutic agents.

The combined effect of interferon and 5-FU on tumor-cell metastasis in the nude mouse

In searching for a suitable animal model system to study colorectal tumor-cell metastasis, the method of injecting tumor cells directly into the spleen of athymic nude mice was explored. The cells used in this study consisted of the Colo 205 cell line, isolated and established from the ascitic fluid of a patient with adenocarcinoma of the colon. In spite of showing tumorigenicity in nude mice after subcutaneous injections, anchorage-independent clonal growth in soft agar, and invasion in the chick embryo skin, the Colo 205 cells failed to metastasize to the lung or liver after intrasplenic injections. The effects of interferon, and interferon in combination with 5-fluorouracil (5-FU), on tumor formation in the spleen, were studied. The combined interferon- and 5-FU-treated animals displayed a significant difference from the controls in the generation of spleen tumors. This combination may possess potentially useful applications in the treatment of solid tumors such as those in the colon and rectum.

Action of recombinant alpha interferon against experimental and spontaneous metastases in a murine model

The therapeutic potential of rHuIFN-alpha A/D, a hybrid human IFN molecule with equal activity on murine cells, was studied in experimental and spontaneous metastatic models of a murine colon carcinoma COLON 26. rHuIFN-alpha A/D inhibited experimental pulmonary metastases of COLON 26 and prolonged the survival of BALB/c mice. Dose scheduling, survival and tumour-cell clearance studies showed that the first 5 days were critical in the inhibition of pulmonary metastases. However, it is unlikely that lung NK cells were involved in the anti-metastatic effect of rHuIFN-alpha A/D because inhibition of pulmonary metastases and a decrease in radio-labelled tumour-cell survival was seen in BALB/c mice depleted selectively of their NK cells by prior treatment with rabbit antiasialoGMI serum. Although rHuIFN-alpha A/D stimulated NK-cell activity in BALB/c mice, it was ineffective in abrogating the NK suppressant action of rabbit anti-asialoGMI serum on murine lung NK cells. Thus, IFN may mediate its early antimetastatic effect via a mechanism independent of NK-cell stimulation. IFN also inhibited the development of lung metastases from s.c. COLON 26 tumors in normal, NK-depleted and T-cell-deficient mice.

Effects of the immunomodulator PSK on growth of human prostate adenocarcinoma in immunodeficient mice

Tumor growth alterations were studied using an immunomodulator, PSK. Four human prostate tumor lines were grown in two types of immunodeficient mice. Two of the lines were selected because they are able to metastasize to lungs in host animals. Outbred NIH Swiss athymic mice having normal natural killer cells and athymic Beige mice deficient in natural killer cells were used as animal hosts. PSK treatment was given to tumor-bearing hosts to some animals soon after solid tumors were injected and to others after solid tumors were well-established. Low dose cyclophosphamide was given to some animals to decrease host natural killer cells and polyinosinic-polycytidylic acid (poly I:C) was given to other animals to increase natural killer cell activity. Measurement of tumor doubling times, host survival and metastatic capabilities showed that either poly I:C or PSK treatment in NIH Swiss animals soon after tumor cells were injected significantly increased tumor doubling times and host survival and decreased the incidence and number of metastatic lung lesions. Two of the tumor lines incapable of metastasizing in NIH Swiss mice were metastatic in the Beige athymic, natural killer-cell-deficient animals.

A new human pancreatic carcinoma cell line developed for adoptive immunotherapy studies with lymphokine-activated killer cells in nude mice

A human tumor cell line designated SU.86 has been established from a moderate-to-poorly differentiated pancreatic carcinoma of ductal origin specifically for adoptive immunotherapy studies. This line was characterized as to its ability to be lysed in vitro by autologous and allogeneic lymphokine-activated killer (LAK) and natural killer cells and to grow in nude mice. SU.86 has been growing continuously in cell culture for more than 100 passages since 22 September 1986. Transplantation orthotopically and heterotopically into athymic Swiss nude mice showed that tumor take was 100% in the orthotopic position when young (4 to 6 wk old) mice were used and 0% when adult (8 wk old) mice were used (P = 0.004). In the heterotopic position (subcutaneous), tumor take was 100% in neonate (2 to 3 wk old) and young mice and 50% in adults. The rate of tumor growth was inversely correlated with age (P less than 0.001). The histologic pattern is similar to that observed in most human pancreatic carcinomas with pseudoglandular structures and frequent mitotic figures. SU.86 has a doubling time of 77 h in vitro and produces carcinoembryonic antigen, 594 ng/10(6) cells in 3 d. Chromosomal analysis shows heterogeneity with two notable cell subpopulations. The cell line is moderately sensitive to lysis by LAK cells in a standard, 4-h chromium-51 release assay (35.4 +/- 4.0%). When grown together with LAK cells in vitro, it is lysed completely in culture in 8 to 15 d, depending on the serum concentration.

Human tumor xenografts as model for drug testing

This paper reviews the history of xenografts, the endpoints commonly used to evaluate response and chemotherapeutic results obtained with serially maintained human tumor xenografts from different laboratories, and discusses the potential clinical relevance of the heterotransplant model for cancer chemotherapy. Specifically, an attempt is made to correlate the published xenograft data with the clinical data. Drug testing with different types of xenotransplanted tumors has shown that the response of xenografts obtained in immune-deficient animals is comparable to that in clinical practice. In addition, xenografts of a particular tumor type are able to identify agents of known clinical activity against that disease.

Cellular heterogeneity. Explanation for changing of tumor phenotype and biologic behavior in soft tissue sarcomas

Many human soft tissue sarcomas are known to show variable structures in a given tumor and to be able of changing the histological feature during the course of the disease. These facts prompted an experimental study in order to ascertain if by use of long-term cultures of an established rat fibrosarcoma cell line (RFS) in respective inoculation tumors a histological picture different from the original fibrosarcoma could be produced. It was found that inoculation tumors generated by later subcultures partly corresponded to tumors with features of malignant histiocytomas and malignant fibrous histiocytomas. In a further experiment we attempted to initiate metastatic dissemination of a primarily non-metastasizing xenotransplanted RFS sarcoma in nude mice. By repeated diminution operations comparable to inadequate tumor surgery in human metastasis formation in lung parenchyme was attained. Taking into account cellular heterogeneity as basically responsible for the phenomena observed, different causal aspects concerning the experimental results are discussed. We deduce from our findings that the concept of histogenetic classification of soft tissue sarcomas should be replaced by an interpretation according to the actual differentiation. This also applies to malignant fibrous histiocytomas which are at least in part mesenchymal tumors and not descendants of mononuclear phagocytic cells and may originate by a dedifferentiation process of otherwise defined sarcoma types.

Influence of H-2K transfection on susceptibility of fibrosarcoma tumor cells to natural killer (NK) cells

In this study, we have used the T-10 fibrosarcoma tumor cells to further analyze the relationship between metastatic competence, expression of H-2K antigens and susceptibility to lysis by virus augmented NK cells in vitro. Our results show an inverse correlation between metastatic properties of the original T-10 clones, IC9 and IE7, and susceptibility in vitro to lysis by virus-augmented NK cells. Restoration by transfection of expression of H-2K genes (H-2Kb or H-2Kk) led to the alteration of the metastatic phenotype of the tumors cells, yet had minor influence on the putative susceptibility of these clones to NK. These observations suggest that expression of MHC gene products, while affecting metastases, does not exclusively determine sensitivity to NK cells.

Pulmonary tumor colony formation following i.v. inoculation of six human colorectal carcinoma xenografts in young gnotobiotic athymic mice

The lung colonizing potential of 6 xenografted human colorectal adenocarcinomas following tail vein inoculation of tumor cell suspensions into gnotobiotic 3-4-week-old congenitally athymic mice was investigated. One of the lines, CRCo2, was of particular interest, as apparently distinctive lung colonizing phenotypes, large (greater than 2.5 mm diameter) and small (less than 1 mm diameter) colonies were identified, and variant lines with greater, equal, or lesser ability to grow in the lungs relative to the sc tumor of origin were observed. Another line, CRCo1, was also able to grow well in the lungs following tail vein inoculation, but subsequent cycles of lung tumor recovery and reinoculation i.v. did not result in an enhancement of the tumor's lung colonizing ability relative to the initial i.v. inoculation of the sc carried tumor. Scattered lung colonies were observed following i.v. inoculation of sc carried xenografts in three of the four other lines, but we could not consistently recover lung colonies with these tumors. The data are in accord with the clinical observation that pulmonary metastasis is not a high frequency event in human colorectal carcinoma, illustrating the selective nature and experimental utility of this model of metastasis. Further, there were indications of the inefficient and/or random nature of the metastatic process in some of the tumors, while in others, evidence for both effectively higher and lower metastatic variants were found, as might be predicted in heterogeneous tumor cell populations.

Lung natural killer and interleukin-2 activity in lung cancer. A pulmonary compartment of augmented natural killer activity occurs in patients with bronchogenic carcinoma

Studies were performed to determine if natural killer (NK) cell and interleukin-2 (IL-2) activities are increased in lungs that harbor malignancy. The NK activity (ability to lyse 51Cr-K562 cells) in bronchoalveolar lavage mononuclear cells (BAC) and washed whole blood cells (Blood) was measured in 8 patients with bronchogenic carcinoma and 8 healthy control subjects. The mean NK activity by BAC from the patients with bronchogenic carcinoma was 2.81 lytic units, and from the control subjects it was 0.19 lytic units (p less than 0.001). When the data were expressed as a ratio of NK activity for BAC/Blood, the mean ratio was 0.98 in patients with cancer compared with 0.12 in control subjects (p less than 0.003). IL-2 activity was bioassayed in recovered bronchoalveolar lavage fluid (BAL) using 3H-thymidine uptake by IL-2-dependent T-cells. The concentration of IL-2 was expressed as units per microgram albumin and also as units multiplied by a dilution factor. The median concentration of IL-2 in BAL from the patients with bronchogenic carcinoma was 10.5 units x 10(-3)/micrograms albumin (range, 3.7 to 229), and from the healthy control subjects it was 0.37 units x 10(-3)/micrograms albumin (range 0.26 to 0.70) (p less than 0.001). When IL-2 activity was expressed as total number of IL-2 units in recovered lavage fluid times a dilution factor (volume of saline used for lavage/volume of lavage fluid recovered), the median number of IL-2 units was 4.7 for the patients with bronchogenic carcinoma and 0.085 for the control subjects (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Interferon-induced alterations in metastatic capacity, class-1 antigen expression and natural killer cell sensitivity of melanoma cells

Pre-treatment of B16 melanoma cells with recombinant interferon-gamma (IFN-gamma) markedly increased their lung-colonising capacity following i.v. injection into syngeneic mice as compared with control cells. A similar enhancement was observed following the injection of treated cells into athymic nude mice but not in athymic mice carrying the beige mutation. Pre-treatment of syngeneic mice with anti-asialo GM1 antibody effectively abrogated any interferon-induced increase in experimental metastatic activity. The same IFN-gamma treatment significantly increased resistance of B16 cells to splenic natural killer (NK) cell activity as determined by in vitro assays. IFN-alpha/beta pre-treatment of B16 cells decreased sensitivity to NK-cell-mediated lysis to a lesser extent than IFN-gamma and had no detectable effect upon the subsequent metastatic activity of the tumor cells. Class-I antigen expression was altered by these IFN treatments, with IFN-gamma causing dramatic increases in expression of H-2Db antigen, in a pattern consistent with the possibility that increased H-2 antigen expression on B16 cells led to decreased NK-cell sensitivity which was reflected by an increase in experimental metastatic capacity.

Growth of a human carcinoma (HEp3) in nude mice: rapid and efficient metastasis

Our aim was to identify conditions which would permit the development of spontaneous metastasis of a human tumor in nude mice in a rapid and predictable manner and to explore ways to quantitate metastasis. Using a human squamous carcinoma--HEp3--we determined that invasiveness and metastasis were influenced by the host. HEp3 cells grew very rapidly and without a significant lag period in Balb/c and NIH(S)-II nude mice kept in aseptic conditions; a much longer lag period was observed in NIH-Swiss mice kept in conventional conditions. The HEp3 tumor displayed a highly invasive behavior in N-NIH(S)-II mice, in which it invaded the body wall, gaining access to the peritoneal cavity. Microinvasion was noted in all strains of mice inoculated with HEp3 cells. To prolong survival of the mice until metastases became evident, primary tumors were excised when they weighed 1-2 gm. N-NIH(S)-II and Balb/c nude mice, maintained in germ-free conditions, were most receptive to the development of metastases-lung metastases developed in 80% of these mice. Over 60% of all metastases were present within 4 weeks following the removal of the primary. Only 26% of tumor bearing NIH-Swiss developed lung metastases. Lung metastases were observed in some mice in the absence of local microinvasion, local tumor recurrence, and regardless of the presence of lymph node involvement. They were also noted in mice from which primary tumors were not excised. We compared three methods of lung metastasis detection: histology, detection of tumor cells in the cultures of lung minces, and the measurement of the levels of human urokinase-type plasminogen activator directly in the lysates of lungs. The detection of tumor cells in cultures of lung minces appeared to be the most sensitive of these methods and the determination of enzyme in lung lysates seemed to hold most promise for a quantitative approach. These data indicate that, the type of tumor, as well as the genetic background and the maintenance conditions of the host, have to be carefully selected to ensure the successful outcome of the particular tumor-host interaction being studied. Adherence to these guidelines allowed us, in the case of the HEp3 tumor, to develop a rapid, predictable, and efficient model in which to study factors affecting metastasis of this human tumor.

The effect of the immune status of the TAR mouse on the growth and metastasis of tumour xenografts

Mice thymectomised at 3-4 weeks of age and subsequently given whole-body irradiation (9 Gy) under cytosine arabinoside cover (TAR mice) provide an alternative model to the athymic nude (nu+/nu+) mouse for studying the biological characteristics of tumour xenografts. In the present study we have evaluated the repopulation events in the bone marrow and spleen following whole body irradiation of TAR mice, and analysed immune competence up to 98 days following irradiation. Repopulation of both bone marrow and spleen was evident in the weeks following whole body irradiation, and an initial increase in the relative proportion of T-lymphocytes present in the spleen was followed by a decrease in the percentage of lymphocytes expressing T-cell markers, which remained below the level observed in control mouse spleen cell preparations. TAR mice exhibited a decreased ability to respond to a non-specific T-cell mitogen and to elicit a T-cell dependent antibody response to influenza viral antigen. Both TAR and control mice possessed macrophages which could be activated to the tumouricidal state, and natural killer activity of TAR mice was enhanced greater than 3-fold above control values. The ability of TAR mice to accept tumour xenografts decreased with the increasing time interval between irradiation and subcutaneous implantation of tumour cells, and (in some instances) spontaneous regression was observed. In addition, a hamster tumour cell line possessing high metastatic potential in its syngeneic host was shown to metastasise to the regional lymph node, lungs, liver, kidneys and spleen of TAR mice from a cell inoculum implanted subcutaneously immediately after irradiation; however, with increasing time between irradiation and inoculation of tumour cells tumour metastasis decreased. The ability of TAR mice to support the growth and metastasis of tumour xenografts would appear to inversely correlate with the increase in natural killer cell activity following irradiation.

Growth and metastatic behavior of human tumor cells implanted into nude and beige nude mice

The growth and metastatic behavior of several human tumor lines grown in adult nude mice, nude mice pretreated with antiserum against asialo GM1 glycoprotein, and beige nude mice were studied. The cell lines were all injected s.c. and i.v. A human colon carcinoma line was also injected into the spleen, and two human renal carcinoma lines were injected into renal subcapsule. All the tumor lines grew as fast or faster in adult nude mice compared with beige nude mice. There were no discernible differences in the production of experimental lung metastasis among the three groups of mice, but human colorectal carcinoma cells and human renal carcinoma cells produced more metastases in nude mice than in beige nude mice after intrasplenic or renal subcapsule injection, respectively. In vitro cytotoxicity assays confirmed that adult nude mice had high levels of natural killer (NK) cell activity whereas nude mice pretreated with anti-asialo GM1 serum and beige nude mice did not. The in vitro NK cell activity of nude mice was demonstrable against mouse lymphoma cells but not against human leukemia cells which were sensitive to lysis by human NK cells. These results suggest that the implantation of human tumor cells into beige nude mice, which are deficient in NK cell activity does not provide an advantageous model for the study of growth and metastasis of human neoplasms.

Experimentally induced metastases of malignant fibrous histiocytomas xenotransplanted into nude mice from an established sarcoma cell line (RFS)

An experimental approach for inducing metastases from xenotransplanted malignant fibrous histiocytomas in nude mice is presented. Malignant fibrous histiocytomas were generated by inoculation of an established cell line (RFS) in the back of 16 nude mice. 7 nude mice were subjected to diminution operations carried out twice and three times, respectively, 6 out of these animals developed metastases, whereas no metastases were found in the inoperated control group (9 mice). The metastasis formation is explained by sarcoma heterogeneity, some factors which might contribute to the phenomenon of tumor dissemination are discussed.

The different effects of recombinant human tumor necrosis factor on rat fibrosarcoma sublines

The antitumor effect of recombinant human tumor necrosis factor (rH-TNF) on two clones of rat fibrosarcoma with different metastatic potential to lymph nodes was examined. The colony formation of clone A, which has high metastatic potential, was completely inhibited by continuous exposure to rH-TNF at 50 U/ml. In contrast, colony formation of clone G, which has low metastatic potential, was not inhibited by high concentrations of rH-TNF (10,000 U/ml). The inhibitory effect of rH-TNF on colony formation by clone A was also observed with a 1-h exposure to rH-TNF. This effect was time and concentration dependent, as determined by the colony assay, 3H-thymidine uptake assay, and 51Cr-release assay. 3H-thymidine and 3H-uridine uptake per cell of clone A exposed to rH-TNF was not decreased. This suggests that the mechanisms of the antitumor effect of rH-TNF were not due to inhibition of DNA and RNA synthesis of tumor cells. In vivo growth and lymph node metastases of clone A inoculated i.p. to Donryu strain rats were completely suppressed by 14 consecutive i.p. injections of 10(5) or 10(6) U/kg per day of rH-TNF. On the other hand the growth of clone G was not influenced by rH-TNF administration.

Basic mechanisms of metastasis

Metastatic disease is responsible for the majority of deaths caused by cancer. The process of metastasis is an orderly, stepwise process that results in the selection of cells that possess the capability to establish viable metastases. These cells must be locally invasive and be able to survive the physical traumas of dissemination and normal host defenses. Once metastatic cells have been arrested in a capillary bed, they must be able to invade the host organ parenchyma and survive in that milieu. Studies in a number of model systems have documented the phenotypic alterations in cells that have "metastatic potential." These differences may stem from normal tumor cell heterogeneity and surprisingly reflect only minor differences in gene expression. The role of activated oncogenes in metastasis is unclear, but a number of laboratories have documented that transfection with activated Ha-Ras results in increased metastatic potential. An increased understanding of the genetic basis of metastatic potential may suggest new directions for intervening in this deadly process.

Defense mechanism and macroscopic tumor growth in lung tissue

A total of 126 resection specimens from malignant lung tumors were cut into serial sections, and tumor volume and macroscopic growth pattern were computed. Four characteristic tumor growth patterns could be separated: Tumors growing in bizarre, irregular shapes; Tumors growing in spheroid shapes; Tumors growing in ellipsoid shapes; Tumors growing in mixed growth pattern. The immunologic response of the host tissue was analyzed grading the number of lymphocytes, plasma cells, macrophages in and at the boundary of the tumor tissue. Lymphocytic subpopulations were analyzed in 46 cases using monoclonal antibodies (BS3/BS4; T3, OKT4, OKT8, OKT11, OKT14). The majority of lymphocytes were T-lymphocytes and monocytes in cases with inflammatory response of host tissue. The ratio of inducer/helper subset (OKT4+) compared to suppressor/cytotoxic subset (OKT8+) was similar in expression as reported for circulating peripheral T-lymphocytes. The different growth patterns depend upon cell type of tumor, immunologic response of the host tissue, and tumor volume. The findings indicate that tumor progression into lung tissue is partly due to "localized metastatic growth" of different tumor cell subpopulations.

The effect of interferon on experimental metastases in immunocompetent and immunodeficient mice

A recombinant human hybrid alpha interferon (rIFN-alpha A/D) with antiviral, immunomodulating and cell-growth-inhibitory activity on murine cells strongly inhibited the development of experimental pulmonary metastases of the Colo 26 adenocarcinoma in BALB/c mice. Twenty-one days after i.v. injection of 5 X 10(4) cells, 8/8 control mice had greater than 200 lung tumour nodules whereas 1/6 mice receiving 500 ng rIFN-alpha A/D had one lung tumour nodule and the other 5 mice were tumour-free. Equally strong inhibition was seen in immunodeficient BALB/c nu/nu (athymic) and beige nu/nu (athymic and NK-deficient) mice. Scheduling experiments in vivo showed that the most important time of IFN treatment was from the day of tumour cell injection to day 5, although statistically significant reductions in lung tumour nodule number and lung weight were seen even when IFN treatment was started 7 days after cell injection. rIFN-alpha A/D was cytostatic to Colo 26 in vitro, causing 50% or more inhibition of cell growth or colony number at IFN levels that could be achieved in the sera of IFN-treated mice. Although rIFN-alpha A/D stimulated NK-cell activity in BALB/c mice, Colo 26 cells were resistant in vitro to such cells whether from control or IFN treated mice.

Development of a metastatic human colon cancer xenograft model in the nude mouse

The objective of our experimental protocols was to develop a metastatic model for a human colon carcinoma xenograft in congenitally athymic nude mice. This model would be useful in evaluating the efficacy of radiolabeled monoclonal antibodies for detection and treatment of regional and distant metastases. The LS-174T human colon carcinoma line was used to establish primary subcutaneous tumors in nude mice. Mice were killed at varying time intervals to establish the incidence of spontaneous metastases. Only lung micrometastases were observed during the 2-month observation period. To increase the metastatic rate, the site of primary implantation was varied and/or surgical manipulations were performed. Excision of small primary tumors resulted in a low incidence of local recurrence and no distant metastases. However, with excision of large primary tumors, a high local recurrence rate was noted and over 30% of mice had gross metastases. Mice bearing hind footpad tumors underwent excision when tumors were at least 1 cm in size. There were no local recurrences, but by 8 weeks over 40% had large pulmonary metastases. The LS-174T tumor was also established as a primary implant in the spleen from which 10 to 15% of the mice developed liver or lung metastases. The LS-174T tumor can metastasize in the nude mice and the latter two models may prove very useful in imaging and therapy studies.

Interaction between specific dietary factors and experimental chemotherapy of metastatic melanoma

The single and combined effects of (a) dietary restriction of phenylalanine and tyrosine, (b) levodopa methylester chemotherapy, and (c) megadose sodium ascorbate supplementation on experimental metastasis was determined in B16-BL6 melanoma. Dietary restriction and levodopa methylester therapy inhibited tumor outgrowth, whereas ascorbate alone was inactive. In combination, however, the effect of dietary restriction and levodopa methylester chemotherapy was augmented by sodium ascorbate. Tumor cells surviving this combination therapy (treated population) were isolated from the lungs of treated mice, and proved to be tumorigenic when inoculated SC into the back of naive mice. The resulting tumors grew more slowly than those produced by inoculation of similarly isolated control cells (control population), irrespective of whether the diet was adequate or deficient in phenylalanine and tyrosine. Failure of the treated tumor cell population to exhibit reduced sensitivity to the combination chemotherapy or, unlike the control population, to exhibit variation in pigmentation levels, suggests that the restriction of phenylalanine and tyrosine during drug therapy alters the tumor response to reduce heterogeneity and perhaps interferes with the emergence of drug resistance.

Acquired resistance towards immune defense during metastatic progression represents a secondary phenomenon

The role of natural immune defense in the control of metastatic spread of tumor cells was evaluated by adapting an s.c.-grown, antigenic, but non-immunogenic rat fibrosarcoma (Bsp6S) to ascitic growth (BSp6A) in the strain of origin (BDX), where peritoneal cells display a high level of NK and macrophage activity. Parallel tests were performed to determine whether tumor cells can selectively adapt to non-specific immune defense, i.e. whether antigenicity of the non-immunogenic tumor remains unaltered, and whether this is accompanied by metastatic progression. During adaptation to ascitic growth the tumor line gradually lost susceptibility to NK cells and macrophages. This was due to the appearance of an increasing number of resistant clones (BSp6S, none; BSp6A, 50% of clones), which had lost binding structures for NK cells and macrophages. No alteration could be observed in antigenicity of the BSp6A variant as revealed by clonal analysis using LD of CTL. Neither BSp6S nor BSp6A cells metastasized. When the ascitic variant was retransplanted s.c. (BSp6AS), susceptibility to NK cells and macrophages was further decreased, in the sense that all clones of the BSp6AS variant became resistant. Furthermore, the BSp6AS variant had lost some of the tumor-associated antigens (TAAs) found on BSp6S and A variants. More important, upon s.c. transplantation BSp6AS regularly metastasized to the draining LN, contrary to BSp6S and BSp6A. When locally growing tumors were excised, rats implanted with BSp6AS frequently died with metastatic tumor burdens in LNs and lung, while other animals survived after excision of BSp6S or BSp6A. The data indicate a correlation between resistance to lysis, morphology and metastatic capacity. But the initial loss of susceptibility to NK cells and macrophages during adaptation to ascitic growth, which can be considered as an escape mechanism, was not accompanied by increased metastatic capacity. Hence, we suppose that with respect to metastatic progression of the BSp6AS variant, resistance to lysis by loss of binding structures represents only a secondary, but not a causative, element.

Rationale and methods for the use of nude mice to study the biology and therapy of human cancer metastasis

Human neoplasms are biologically heterogeneous. The extensive cellular diversity found in malignant neoplasms is generated by the rapid emergence of clonal subpopulations of tumor cells with different properties that include invasion, metastasis and responsiveness to treatment. Studies in rodent systems have indicated that cancer metastases can be clonal in their origin and that different metastases can originate from different progenitor cells from the primary tumor. This metastatic heterogeneity of tumor cells has many ramifications for studies of tumor biology, in general, and studies of therapy, in particular. The heterogeneous nature of metastatic human neoplasms can now be studied under defined conditions in healthy athymic nude mice. The neoplasms must be free of mouse pathogens and the mice must be kept in specific-pathogen-free conditions. Careful consideration must be given to the intimate tumor-host relationship for each tumor system studied, because the metastatic potential of human neoplasms can vary with the site of implantation into nude mice. Several methods for studying the biology of human neoplasms in the nude mouse are described as well as techniques to assure the success of these studies. The data show that the healthy young nude mouse can be a useful in vivo model for ascertaining the metastatic potential of human neoplasms, for selecting and maintaining cell variants of high metastatic potential from heterogeneous human tumors, and for studying therapeutic agents directed against metastatic cells proliferating in visceral organs.

Restoration by recombinant interferon alpha A/D of host defense systems against tumor in immunosuppressed mice

Recombinant human interferon alpha A/D (alpha A/D) restored or augmented host defense systems against tumors in immunosuppressed mice. In normal C57BL/6 mice, inoculation of B16 melanoma F1 cells caused few pulmonary metastasis, whereas in mice pretreated with cyclophosphamide (CY) it caused a high incidence of pulmonary metastasis, leading to earlier death than in the normal mice inoculated with the same dose of the tumor. alpha A/D given after the CY treatment counteracted the deleterious effects of the CY treatment. Since such restorative activity was seen even against the subline of B16 F1 which had been made resistant to its direct antiproliferative effect, alpha A/D seems to exert its effect indirectly through host defense systems. However, this activity of alpha A/D in the mice pretreated with CY was abrogated by inoculation of anti-asialo GM1 serum but not by i-carrageenan. The CY treatment reduced NK activity, while alpha A/D given after the CY treatment restored or augmented the NK cell activity in lung cells and peripheral blood mononuclear cells, but not in spleen cells. These findings suggest that the restoration or augmentation of NK activity in the lung and/or peripheral blood might be the major factor leading to the antimetastatic activity of alpha A/D in the mice treated with CY.

Dendritic cells that have interacted with antigen are targets for natural killer cells

Natural killer (NK) cells (poly I:C induced, x-ray resistant, nonadherent, Thy-1-, Ly-1.1-, Ly-2.1-, anti-asialo GM1-positive, and cytotoxic for YAC-1) suppressed T lymphocyte proliferation in mixed lymphocyte reaction (MLR) and autologous MLR cultures. Dendritic cells (DC) were required for proliferation of lymphocytes in both responses. The question whether lymphocytes or DC were the targets for NK cells was resolved by taking advantage of the fact that NK cells, but not DC, lose activity after 24 h in culture. Three findings indicate that DC, not lymphocytes, are targets for NK cells. First, responses suppressed by NK cells were fully restored by adding small numbers of DC to cultures 24 h after NK cells had been added. Second, DC incubated alone with NK cells and antigen for 24 h did not stimulate proliferation of lymphocytes. Third, lymphocytes incubated alone with NK cells for 24 h proliferated normally when DC were added. Additional experiments showed that DC became targets only after interaction with antigen. Thus, we suggest that NK cells may regulate lymphocyte proliferation by monitoring antigen presentation by DC.

Differential action of six human interferons against two human carcinomas growing in nude mice

Six different pure human interferons (IFNs), were tested for anti-tumour effect against two human carcinomas, breast and bowel, growing in nude mice, in a total of 36 experiments. The IFN-alpha mixture, analogue and subtypes showed the greatest activity, particularly against the breast cancer xenograft, whereas IFN-beta and IFN-gamma had little effect. However, circulating IFN could be found in the sera of mice treated with all 3 IFN types. In terms of amount of IFN protein, IFN-alpha Con1, an IFN-alpha analogue, was the most effective, a dose of 0.1 micrograms/mouse/day being sufficient to induce breast tumour regression, and IFN-gamma the least effective, a dose of 10 micrograms/mouse/day having no effect on the same tumour. A more detailed comparison of 2 IFN-alpha subtypes showed that a daily dose of 1 microgram IFN-alpha A was more effective than the same dose of IFN-alpha D, but as this IFN had approximately 30 times less antiviral activity on human cells than IFN-alpha D, these IFNs were probably at least equally effective in terms of human cell units. IFN-alpha D stimulated mouse spleen natural killer cell activity but it was not clear whether this stimulation was involved in anti-tumour activity. We conclude that this model system is useful for investigating direct anti-tumour activity of a wide range of IFN types and subtypes.