Biologic and biochemical differences between in vitro and in vivo passaged Friend erythroleukemia cells. I. Tumorigenicity and capacity to metastasize

Cloned interferon-sensitive (745) and interferon-resistant (3Cl-8) Friend erythroleukemia cells (FLC) passaged in vitro, are not very tumorigenic when first injected intraperitoneally (i.p.) into syngeneic DBA/2 mice although they do form solid tumors when injected subcutaneously (s.c.). By serially passaging FLC (either 745 or 3Cl-8 cells) i.p. in DBA/2 mice, we obtained two different FLC lines capable of growing i.p. and inducing tumor ascites. The s.c. injection of DBA/2 mice with these in vivo passaged FLC resulted in tumor metastases in the liver and spleen, whereas metastases were not observed in mice inoculated s.c. with in vitro passaged FLC. The capacity of in vivo passaged FLC to metastasize was acquired after several i.p. passages. This highly malignant behavior was a stable characteristic of these cells. All the clones derived from in vivo passaged FLC and passaged more than 14 times in vitro induced hemorrhagic ascites when injected i.p., and metastasized to the liver and spleen when injected s.c. The phenotype of sensitivity or resistance to the inhibitory effect of alpha/beta mouse interferon on virus replication and cell multiplication was conserved during serial i.p. passages and maintained in the clones derived from in vivo passaged cells. These FLC showed a decreased capacity to differentiate in vitro upon treatment with dimethylsulfoxide (DMSO) and a reduced production of Friend leukemia virus with respect to the original clones passaged in vitro.     

Antitumor effects of interferon in mice injected with interferon-sensitive and interferon-resistant Friend leukemia cells. I

Interferon-sensitive (745) and interferon-resistant (3C1-8) Friend leukemia cells (FLC) are highly tumorigenic for DBA/2 mice. The phenotype of interferon sensitivity or resistance does not change with in vivo passage. Daily administration of mouse interferon markedly enhanced the survival time of mice injected with either 745 or 3C1-8 cells. Use of quantitative methods for determining the number of FLC (colony formation in agarose and immunofluorescence) permitted us to show that potent, partially purified or highly purified mouse interferon (s.a. 0.5 to 1 X 10(9) u/mg protein) induced a 100- to 1,000-fold decrease in the number of tumor cells in the peritoneal cavity in the days following inoculation of 745 or 3C1-8 cells. Interferon decreased the number of FLC even when treatment was initiated at a time when tumor cells were multiplying exponentially in the peritoneal cavity. There was no evidence that interferon acted as an inducer of FLC differentiation in vivo. The finding that interferon was equally effective in mice inoculated with interferon-resistant cells as in mice inoculated with interferon-sensitive cells suggests that in this experimental system interferon does not act directly on the tumor cells, but that the interferon-induced antitumor activity is mediated by the host.     

Tumor necrosis factor alpha induces early morphologic and metabolic alterations in Friend leukemia cell tumors and fibrosarcomas in mice

Morphologic and metabolic studies have been carried out on Friend leukemia cell (FLC) tumors (grown in DBA/2 mice) or fibrosarcomas (grown in C3H/HeN or C3H/HeJ mice) shortly after peritumoral injection of recombinant mouse tumor necrosis factor (TNF) alpha. Marked vascular congestion and focal extravasation of erythrocytes were observed as soon as 1 hr after injection of either FLC tumors or fibrosarcomas with TNF. Focal areas of disaggregation of tumor cells were observed 1 hr after injection of TNF. Intraluminal thrombi (composed of degranulated platelets and fibrin) were detected 3 and 6 hr after TNF treatment, and were associated with areas of depletion of endothelial cell cytoplasm. To correlate these morphologic changes in the tumor with alterations in tumor metabolism, NMR spectroscopy and biochemical studies were undertaken on freshly dissected FLC tumors and fibrosarcomas shortly after injection of TNF. The earliest metabolic alterations observed after 1 hr in TNF-treated FLC tumors of fibrosarcomas were: (i) increase in the average intratumoral pH; (ii) decrease in the levels of ATP. These phenomena were not associated with a reduced glycolytic capacity of TNF-treated tumors as, at these early times after injection, the levels of lactic acid were virtually the same for TNF-treated or control treated tumors. Alterations in the levels of some products of phospholipid degradation (GroPCho, GroPEtn, GroP and Cho) also occurred in these tumors as early as 3 hr after TNF treatment. These metabolic changes were not observed in ascitic FLC tumors after TNF treatment. We suggest that TNF induces alterations in tumor blood vessels which subsequently lead to changes in tumor metabolism and tumor degeneration.     

Interleukin-1 beta induces tumor necrosis and early morphologic and metabolic changes in transplantable mouse tumors. Similarities with the anti-tumor effects of tumor necrosis factor alpha or beta

Peri-tumoral injection of recombinant human interleukin-1 beta in mice transplanted s.c. with Friend erythroleukemia cells (FLC) resulted in marked inhibition of tumor growth and increased survival. However, in vitro treatment of FLC (745 or 3Cl-8) with IL-1 beta barely inhibited cell multiplication. IL-1 beta, injected into established solid tumors, induced marked morphologic changes. Vascular congestion and focal extravasation of erythrocytes were observed as early as 6 hr after injection with IL-1 beta of FLC and L1210 tumors and HeJ16 fibrosarcomas. Focal areas of disaggregation of tumor cells and tumor necrosis were observed 6 and 24 hr after IL-1 injection. These morphologic changes were similar to those observed in FLC tumors or HeJ16 fibrosarcomas treated with TNF-alpha or beta. These cytokines determined morphological changes in tumor blood vessels of FLC tumors within 1 hr of injection. Freshly dissected FLC tumors and their tissue extracts were studied by Nuclear Magnetic Resonance (NMR) spectroscopy, shortly after peri-tumoral injection of IL-1 beta or TNF-beta. After 6 hr, both cytokines induced a 3-fold reduction in the levels of two catabolites, glycerophosphorylcholine and glycerophosphorylethanolamine, an accumulation of sn-glycerol 3-phosphate and a more than 10-fold increase in the choline/phosphorylcholine ratio. These results are similar to those reported for TNF-alpha, and can be interpreted on the basis of an activation of glycerophosphorylcholine phosphodiesterase (EC 3.1.4.2) and partial inhibition of choline kinase (EC 2.7.1.32). IL-1 beta and TNF-beta (like TNF-alpha) also induced alkaline shifts (0.10-0.25 units) in the average intratumoral pH value. We suggest that alterations of tumor blood vessels may be the primary events in solid tumors treated with IL-1 beta or TNF. Such alterations lead to early changes in tumor metabolism and subsequent tumor cell degeneration.     

Anti-tumor effects of interferon in mice injected with interferon-sensitive and interferon-resistant Friend leukemia cells. V. Comparisons with the action of tumor necrosis factor

A number of similarities and dissimilarities in the anti-tumor effects of TNF and interferon alpha/beta have been observed in DBA/2 mice injected with Friend erythroleukemia cells (FLC). Mouse TNF exerted marked anti-tumor effects in mice injected either s.c. or i.p. with FLC lines 3C18 or 3 gamma R8 resistant in vitro to the cytotoxic effects of TNF. Likewise, mouse interferon alpha/beta had anti-tumor activity in mice injected with these FLC, resistant to the action of interferon alpha/beta or gamma in vitro. The results of histopathologic examination and 31P nuclear magnetic resonance analyses of 3C18 FLC s.c. tumors injected with TNF resembled the results previously obtained for 3C18 FLC tumors injected with interferon alpha/beta, although the effects of TNF occurred more rapidly. Injection of mice with antibody to mouse interferon alpha/beta or gamma did not abrogate the anti-tumor effects of TNF in mice injected i.p. with FLC. Our results suggest that in this experimental system the anti-tumor effects of TNF, like interferon alpha/beta, do not result from a direct effect on the tumor cells themselves but are host-mediated.     

Antitumor effects of interferon in mice injected with interferon-sensitive and interferon-resistant Friend leukemia cells. III. Inhibition of growth and necrosis of tumors implanted subcutaneously

Administration of highly purified interferon to DBA/2 mice inhibited the growth of interferon-sensitive or interferon-resistant Friend erythroleukemia cells implanted subcutaneously. Injection of interferon at the site of tumor inoculation was more effective than injection of interferon intraperitoneally. Histologic examination of tumors in interferon-treated mice showed extensive areas of tumor-cell necrosis in the absence of an obvious host-cell infiltrate. Interferon inhibited the growth of established subcutaneous tumors and induced complete tumor regression in some mice. Interferon treatment also resulted in an inhibition of tumor metastases in the liver and spleen.     

Microvascular injury in pathogenesis of interferon-induced necrosis of subcutaneous tumors in mice

DBA/2 mice were injected sc with cells from the highly malignant Friend erythroleukemia cell (FLC) 3Cl8 subline, which is resistant to mouse interferon alpha/beta, or with the ESb lymphoma. When interferon alpha/beta was injected intratumorally or peritumorally, tumor growth was markedly suppressed, and established vascularized tumor nodules became progressively necrotic. Tumor necrosis was of the coagulation type that usually results from deprivation of blood flow. Morphologic examination of approximately 1,000 blood vessel profiles and approximately 2,000 endothelial cells in 1-micron Epon sections of sc 3C18 FLC tumors showed that interferon treatment resulted in rapid and pronounced vascular endothelial cell damage that preceded tumor necrosis. No inflammatory cell infiltrate was observed. Our results suggest that interferon alpha/beta exerted an antitumor effect in these tumor models by damaging tumor blood vessels, causing disruption of tumor blood flow, which led to ischemic tumor necrosis.     

Interferon treatment markedly inhibits the development of tumor metastases in the liver and spleen and increases survival time of mice after intravenous inoculation of Friend erythroleukemia cells

To investigate the effect of interferon treatment on the development of tumor metastases, DBA/2 mice were injected i.v. with 2 X 10(6) Friend erythroleukemia cells (FLC) (equivalent to about 5 X 10(5) LD50). FLC multiplied rapidly in the liver and spleen and all untreated or control treated mice died between 7 and 12 days. Daily treatment of mice with potent preparations of mouse interferon alpha/beta was initiated 3 to 72 hr after i.v. inoculation of tumor cells, at times when FLC were already present in the liver and spleen. Interferon treatment resulted in a 100 to 1,000-fold inhibition of the multiplication of FLC in the liver and spleen and a marked increase in mean survival time. Small numbers of tumor cells persisted in the liver and spleen in some interferon-treated mice and could be recovered by bioassay several weeks after tumor inoculation. Most interferon-treated mice died with tumor in the ensuing months. Three of 34 interferon-treated mice were considered cured as they were alive at 386, 325 and 284 days after tumor inoculation. Daily treatment of tumor-inoculated mice with human recombinant interferons alpha D and alpha BDDD, which had antiviral activity on mouse cells in culture, also increased the survival time of mice injected i.v. with FLC. The use of the interferon-resistant 3C18 line of FLC suggests that the marked inhibition of development of established liver and spleen metastases was not due to a direct effect of interferon on the tumor cells, but was host-mediated.     

Anti-tumor effects of interferon in mice injected with interferon-sensitive and interferon-resistant Friend leukemia cells. VI. Adjuvant therapy after surgery in the inhibition of liver and spleen metastases

Adult DBA/2 mice were injected s.c. with the highly malignant, interferon-resistant 3C18 line of Friend erythroleukemia cells (FLC). Eight or 9 days after established s.c. tumors had developed, the primary tumor was excised and mice were treated i.p. with either mouse interferon alpha/beta or a control preparation. At the time of surgery, mice already had tumor cells in the liver. All control-treated mice died in the ensuing 2 weeks with extensive tumor metastases in the liver and spleen. Interferon treatment resulted in an inhibition of the development of liver and spleen metastases and a markedly increased survival time. We conclude that interferon alpha/beta is effective as adjuvant therapy after surgery for metastatic disease in mice.     

Anti-tumor effects of interferon in mice injected with interferon-sensitive and interferon-resistant friend leukemia cells. IV. Definition of optimal treatment regimens

Mouse interferon alpha/beta exerted a similar anti-tumor effect in DBA/2 mice injected i.p. with Friend erythroleukemia cells (FLC) either sensitive or resistant to interferon as determined by both in vitro and in vivo assays. Using this tumor system we attempted to define optimal treatment regimens for interferon administration. Interferon was most effective when injected at the site of tumor inoculation rather than at a distant site. Two factors seemed of especial importance: the amount of interferon injected and the frequency of interferon administration. Thus, for daily administration of interferon, the antitumor effect was directly related to the amount of interferon injected. For a given total dose of interferon, repeated administration of small doses of interferon was more effective than administration of a larger dose at more widely spaced intervals. The anti-tumor efficacy of interferon was independent of the number of FLC inoculated when 10(2) to 10(5) FLC were injected, but interferon treatment was less effective when 10(6) or 10(7) FLC were injected. The relevance of these results to the use of interferon in patients with cancer is discussed.     

Biologic and biochemical differences between in vitro and in vivo passaged friend erythroleukemia cells. II. Changes in cell surface glycoproteins associated with a highly malignant phenotype

Friend erythroleukemia cells (FLC), serially passaged in vkroor by intraperitoneal injection in DBA/2 mice, exhibit markedly different tumorigenicity and capacity to metastasize. We have attempted to determine whether the differences in tumorigenicity between these two lines of FLC were correlated with any biochemical changes in their cell membranes. Although consistent modifications of FLC membrane gangliosides were detected after FLC multiplied in the peritoneum, the pattern of FLC gangliosides was not a stable characteristic and did not correlate with tumorigenicity. In contrast, analysis of FLC membrane glycoproteins by cell surface labelling techniques (i.e., galactose-oxidase-borohydride techniques and polyacrylamide gel electrophoresis-fluorography) or by metabolic labelling of glycoproteins with ³H-galactose, revealed consistent differences in the high MW region of the gels between parental in vitro passaged FLC (either 745 or 3C1-8 cells) and clones derived from in vivo passaged cells. No significant differences in the membrane proteins were detected between in vitro and in vivo passaged FLC when lactoperoxidase-catalyzed iodination and polyacrylamide gel electrophoresis-autoradiography were used. It is seen that repeated in vivo passages of FLC resulted in the appearance of different patterns of membrane glycoproteins and that these changes appeared to be associated consistently with the capacity of these cells to grow as tumor ascites and to metastasize to the liver and spleen.     

Importance of interferon alpha in the resistance of allogeneic C57B1/6 mice to the multiplication of Friend erythroleukemia cells in the liver

Friend erythroleukemia cells (FLC) (H-2d) injected intravenously multiply extensively in the livers of syngeneic DBA/2 mice and not at all in the livers of allogeneic C57B1/6 mice. Our results indicate that interferon alpha (IFN-alpha) is an important factor in the resistance of allogeneic mice to the multiplication of FLC in the liver. (a) After i.v. inoculation of FLC there was an inverse correlation between the presence of IFN-alpha in the serum and the capacity of FLC to multiply in the liver. Thus, all 44 FLC-injected adult C57B1/6 mice had circulating IFN-alpha and FLC did not multiply in the liver of any of the mice. Interferon was not detected in the serum of 83% of 41 FLC-injected DBA/2 mice (and was found only at a low titer in 17% of the mice) and FLC multiplied in the liver of all mice. (b) FLC did multiply in the livers of newborn C57B1/6 mice and in the livers of irradiated adult C57B1/6 mice, and IFN-alpha was not detected in their sera. In contrast, after i.v. inoculation of FLC, IFN-alpha was detected in the sera of 3-week-old and athymic nu/nu adult C57B1/6 mice while FLC failed to multiply in the liver. (c) FLC also induced IFN-alpha in congenic B10.D2 (H-2d) mice and FLC did not multiply in the liver. We suggest that, depending on the site of tumor implantation, different host mechanisms have various degrees of importance in controlling the growth and/or rejection of allogeneic tumor cells, and that IFN-alpha is particularly important when FLC are injected i.v.     

Effects of intralesional interferon on neuroblastoma: changes in histology and DNA content distribution of tumor masses

Local injections of interferon, 30 X 10(4) IU, ten times, were found to reduce masses of neuroblastoma. Histologic findings and nuclear DNA measurements of cells from tumors in which interferon has been injected compared with cells from tumors that did not receive injections demonstrated that the reduction of neuroblastoma masses by interferon did not depend on increased cell differentiation or on interruption of tumor cell production. Although the mechanism of interferon's action on reducing neuroblastoma is unknown, the disappearance of tumor cells may be caused by high levels of interferon in tumor tissues.     

Anti-tumor effects of interleukin-2 and interleukin-1 in mice transplanted with different syngeneic tumors

We have studied the anti-tumor effects of human recombinant IL-2, alone or in association with LAK cells, in mice transplanted subcutaneously (s.c.) with the following syngeneic tumors: highly metastatic Friend leukemia cells (FLC), nonmetastatic FLC, lymphoma RBL-5 cells and HeJ16 fibrosarcoma cells. In these tumor models, peri-tumoral injections of IL-2 were more effective in inhibiting tumor growth than a systemic treatment. Although s.c. IL-2 treatment resulted in marked inhibition of tumor growth in mice injected s.c. with highly metastatic FLC, it was not effective in inhibiting growth of FLC in the liver and spleen. IL-2 therapy was more effective at increasing survival time in mice transplanted with non-metastatic FLC or with RBL-5 cells. In mice transplanted with HeJ16 fibrosarcomas, s.c. IL-2 treatment resulted in highly significant anti-tumor effect and survival of 70% of tumor-injected mice. No general correlation was found between in vitro sensitivity or resistance to the cytolytic activity of LAK cells and the anti-tumor effects observed in vivo. Subcutaneous injection of IL-1 beta in mice transplanted with highly metastatic FLC resulted in a marked increase in survival time and inhibition of metastatic tumor growth in liver and spleen. Combined treatment of IL-1 beta and IL-2 produced a synergistic anti-tumor effect: 60% of mice injected with highly metastatic FLC survived. Combined IL-1/IL-2 treatments exerted no anti-tumor activity either in DBA/2 mice injected with antibody to Thy 1.2 antigen or in nude mice, indicating that T cells play important roles during IL-1/IL-2 therapy. In vitro treatment of FLC with IL-1 beta resulted in a slight inhibition of cell multiplication, whereas even high doses of IL-2 did not affect FLC multiplication. Our results indicate that local combined treatments with IL-1 and IL-2 can induce potent, host-dependent (T cell-mediated) anti-tumor effects against highly malignant tumors.     

Inhibition of mouse alpha/beta-interferon of the multiplication of alpha/beta-interferon-resistant Friend erythroleukemia cells cocultured with mouse hepatocytes

Administration of alpha/beta-interferon (IFN) exerts a marked antitumor effect in DBA/2 mice given injections i.v. of large numbers of IFN-alpha/beta-resistant erythroleukemia cells (FLC). To investigate the possible mechanisms of FLC tumor inhibition in the liver of interferon-treated mice, we developed an in vitro model consisting of a coculture of IFN-alpha/beta-resistant 3Cl8 FLC and syngeneic mouse hepatocytes. Whereas IFN-alpha/beta did not inhibit the multiplication of 3Cl8 FLC cultivated alone, it effectively inhibited the multiplication of 3Cl8 FLC in coculture with hepatocytes. The inhibitory effect was directly proportional to the amount of IFN-alpha/beta added to the cocultures, and more than 90% inhibition of FLC multiplication was noted with 1.6 x 10(5) IU/ml of IFN-alpha/beta on Day 3 of coculture. When FLC were separated from the monolayer of hepatocytes by a pored membrane (0.4 microns), the inhibitory effect on FLC proliferation was unchanged, indicating that a soluble factor(s) released from IFN-treated hepatocytes was most important in the inhibition of FLC multiplication. An inhibitory activity of FLC multiplication was detected only in the conditioned medium of IFN-treated hepatocytes but not in the conditioned medium of control hepatocytes nor in extracts of IFN-treated or control hepatocytes. The inhibitory factor(s) in the conditioned medium of IFN-treated hepatocytes was retained by an ultrafiltration membrane (Mr cut off 10,000), and its activity was completely abrogated by trypsin digestion. Its stability to treatment with 1 M acetic acid as well as lack of correlation between the antiproliferative effect and the amount of L-arginine in the medium distinguished this factor(s) from liver arginase which was also found to be a potent inhibitor of FLC multiplication in vitro. The inhibitory factor(s) was also distinguishable in its biological activity from IFN gamma, interleukin 1 alpha and beta, and transforming growth factor beta 1 and beta 2. These results suggest the possibility that the inhibitory effect of IFN-alpha/beta on the development of 3Cl8 FLC in the livers of IFN-treated mice may be mediated by an IFN-induced inhibitor of FLC multiplication.     

Interaction of IFN α/β with host cells essential to the early inhibition of friend erythroleukemia visceral metastases in mice

We have previously shown that an intact immune system was essential to the increase in survival time of IFN-α/β-treated mice injected i.v. with an IFN-α/β-resistant line of Friend erythroleukemia cells (FLC) highly metastatic to the liver and spleen. Here, we have investigated the early interactions of IFN α/β with host cells prior to the development of the immune response. IFN α/β treatment resulted in 50- to 100-fold inhibition of FLC multiplication in the liver and spleen of normal DBA/2 mice shortly after tumor inoculation, as evaluated by colony formation in agarose. IFN treatment was far less effective in inhibiting the multiplication of FLC in the livers of NK-cell-deficient DBA/2 beige mice, or in immunocompetent DBA/2 mice treated with antibody to asialo GMI, or silica, or in mice subjected to sub-lethal irradiation. Injection of antibody to CD4 or CD5 did not affect the early inhibitory action of IFN α/β on FLC multiplication but did decrease survival time. Light- and electron-microscope examination of the livers of IFN-treated, FLC-injected mice confirmed the early inhibition of FLC multiplication in the liver and spleen. Our results indicate that IFN α/β inhibits the development of FLC visceral metastases by acting first on host cells, such as NK cells and macrophages, and then continues to act in consort with the developing immune response. © 1994 Wiley-Liss, Inc.     

Inhibition of human HT29 colon carcinoma growth in vitro and in vivo by swainsonine and human interferon-alpha 2

Swainsonine, a plant alkaloid and potent inhibitor of Asn-linked oligosaccharide processing, has previously been shown to inhibit organ colonization by metastatic murine tumor cells and to inhibit the growth of transformed fibroblasts in soft agar. In this report, we show that swainsonine has antiproliferative activity against human tumor cells growing in tissue culture and as tumor xenografts in nude mice. The antiproliferative activity of swainsonine was additive with that of human interferon-alpha 2 (HuIFN-alpha 2) in cultures of HT29 colon carcinoma, SN12 renal carcinoma, and A375 melanoma cells. In vivo, the growth rate of HT29m human colon carcinoma tumors in athymic nude mice was reduced by supplementing their drinking water with swainsonine (49%) or by administering HuIFN-alpha 2 systemically (53%); combining these treatments reduced tumor growth by 78%. Combining swainsonine and HuIFN-alpha 2 treatments enhanced the activity of the interferon-inducible enzyme 2',5'-oligoadenylate [2',5'-oligo(A)] synthetase in HT29m tumors compared to that observed in tumors from mice treated with interferon alone. In vitro, swainsonine enhanced interferon-dependent induction of 2',5'-oligo(A) synthetase activity in low-density cultures of HT29m cells. However, swainsonine alone did not stimulate 2',5'-oligo(A) synthetase activity in vivo or in vitro, indicating that the antiproliferative effect of swainsonine is independent of interferon production. The results suggest that in addition to the previously reported antimetastatic activity of swainsonine, the plant alkaloid has antiproliferative activity that is independent from, but additive with, that of interferon in vivo and in vitro.     

Interferon-alpha/beta in virus-induced mouse mammary carcinogenesis: effects on the spontaneous process and on the progression of transplanted pre-neoplastic lesions.

Low levels of anti-viral activity, mainly interferon alpha/beta (IFN-alpha/beta), are regularly found in lymphoid tissues of BALB/c mice infected with the C3H strain of mammary tumor virus. At the time of tumor development, significant amounts of anti-viral activity were detected in homogenates of spleen and mammary tumors, but not in blood and normal mammary glands. This activity is pH2-resistant and neutralized by antibody to IFN/alpha-beta. The pathogenetic role of IFN in mammary carcinogenesis was investigated in 2 ways: (a) by treating virus-infected newborn mice with antibody to IFN-alpha/beta, and (b) by giving either the latter antibody or IFN-alpha/beta to virus-free animals transplanted with pre-neoplastic lesions. Mice were treated only for 2 months, starting either 1 week after birth or immediately after tumor transplant. In case (a), treatment with antibody to IFN-alpha/beta shortened the incubation period of mammary carcinomas and decreased the mean survival time. In case (b), anti-IFN antibody did not significantly affect the development of mammary tumors. However, exogenous IFN-alpha/beta markedly reduced both tumor incidence and mortality rate. These results indicate that endogenous IFN-alpha/beta plays a crucial role in the in vivo restriction of the early infectious phase of spontaneous carcinogenesis and that relatively high doses of IFN-alpha/beta may inhibit the progression of pre-neoplastic lesions.     

Growth properties, differentiation capacity and oncogene expression in metastatic and nonmetastatic Friend leukemia cell variants.

The aims of this study were: (1) to characterize the biologic properties of the WGA-resistant (WR) Friend leukemia cells (FLC) as compared to the original nonmetastatic or highly metastatic FLC; (2) to investigate the possible correlations between the expression of some oncogenes (i.e., c-myc, H-ras and K-ras) and the in vitro and in vivo behavior of FLC. The tumorigenic behavior of the different FLC types strongly depended on the site of tumor injection. Both WR FLC and in vitro passaged FLC did not grow as ascites (when injected intraperitoneally) and developed large solid tumors (when injected subcutaneously), without forming any spleen or liver metastasis. In contrast, in vivo passaged FLC rapidly formed hemorrhagic ascites when injected intraperitoneally; the subcutaneous injection of these cells resulted in the development of solid tumors, which were smaller than the other FLC tumors, but capable of metastasizing to the liver and to the spleen. No significant differences were observed in the in vitro growth characteristics and cell cycle parameters among the different FLC types under various experimental conditions (i.e., FCS concentration or cell seeding densities). Similarly to the metastatic in vivo passaged parental cells, WR FLC exhibited a much lower erythroid differentiation after in vitro addition of either dimethyl sulfoxide or hexamethylene bisacetamide than the in vitro passaged FLC. High levels of c-myc oncogene mRNA were expressed in all FLC variants; no major variations in the c-myc expression were observed in FLC cultivated in medium supplemented with different FCS concentrations and/or seeded at various cell densities. In addition, no changes in the expression of H-ras or K-ras were observed between the different FLC types.     

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.