Inhibition of tumor growth by poly(ethylene glycol) derivatives of anti-ErbB2 antibodies

Poly(ethylene glycol) (PEG) modification of substances with antitumor activity was shown to enhance penetration into growing solid tumors and extend antitumor effects. Accordingly, PEG was introduced as a modifier to two types of monoclonal antibodies (N12 and L26) specific to the ErbB2 (HER2) oncoprotein. These antibodies suppress the growth of tumors overexpressing ErbB2 (e.g. N87 human tumor) and the effect of PEG on their antitumor activity was evaluated. Methoxy-PEG-maleimide conjugated to sulfhydryl groups at the hinge region of the antibodies impaired their antibody binding to N87 tumor cells and did not enhance the antitumor inhibitory activity in tumor-bearing mice. A branched N-hydroxysuccinimide-activated PEG (PEG2), conjugated through amino groups of the protein, was used for binding to the whole antibody (Ab) or to its monomeric Fab′ fragment. When tested against N87 cells in vitro, the binding activity and antitumor cytotoxic effects of Ab-PEG2 were mostly preserved. PEG2 modification did not seem to alter the tumor-inhibitory activity of the antibodies in vivo and the same pattern of tumor development was observed during the first few weeks following administration. However, the stimulating effects of PEG were observed at later stages of tumor growth since tumor development was either slowed down or completely arrested. Furthermore, a second tumor implanted into the same mice during this later stage was significantly or completely inhibited, as compared to results in mice injected with the unmodified antibody. The Fab′-PEG2 monomeric derivative was also shown to be effective in inhibiting the growth of a second tumor. The extended and prolonged enhancing effect of PEG on the antitumor activity of antibodies or Fab′ fragments directed against ErbB2 may be of importance in the treatment of ErbB2-overexpressing neoplasms. Received: 2 September 1999 / Accepted: 19 February 2000     

Inhibition of the MtTF4 tumor growth by dexamethasone

It is known that estradiol, but not progesterone or dihydrotestosterone, slows down the growth of the MtTF4 tumor. In the present paper, it is shown that: (1) this tumor contains glucocorticoid receptors, (2) its growth is also inhibited by treatment with dexamethasone (Dex), and (3) the growth rate of a cell line and several clones established from the tumor is negatively controlled by Dex 10(-7) M in culture medium containing 10% gelding serum. Unlike estradiol, Dex does not induce cell hypertrophy. This work suggests that the inhibition of the MtTF4 tumor growth by Dex may be due in part to a direct action on tumor cells and, taking into consideration previous reports, it allows us to forward the hypothesis that both Dex and estradiol inhibit MtTF4 tumor growth in two different ways.     

Inhibition of Helicobacter pylori by garlic extract (Allium sativum)

Abstract The antibacterial effect of aqueous garlic extract (AGE) was investigated against Helicobacter pylori . Sixteen clinical isolates and three reference strains of H. pylori were studied. Two different varieties of garlic were used. The concentration of AGE required to inhibit the bacterial growth was between 2–5 mg ml⁻¹. The concentration, for both AGE types, to inhibit 90% (MIC₉₀) of isolates was 5 mg ml⁻¹. The minimum bactericidal concentration (MBC) was usually equal to, or two-fold higher than, minimum inhibitory concentration (MIC). Heat treatment of extracts reduced the inhibitory or bactericidal activity against H. pylori ; the boiled garlic extract showed a loss of efficacy from two-to four-fold the values of MIC and the MBC obtained with fresh AGR. The antibacterial activity of garlic was also studied after combination with a proton pump-inhibitor (omeprazole) in a ratio of 250:1. A synergistic effect was found in 47% of strains studied; an antagonistic effect was not observed.     

Inhibition of growth hormone-stimulated lipolysis by somatostatin, insulin, and insulin-like growth factors (somatomedins) in vitro

The effects of somatostatin, insulin, insulin-like growth factor I (IGF-I), and insulin-like growth factor II (IGF-II)/MSA on growth hormone (GH) (1 microgram/ml)-induced lipolysis were examined employing chicken adipose tissue in vitro. Basal and GH-stimulated glycerol release were inhibited by somatostatin (1 ng/ml) and by IGF-II/MSA (10 and 100 ng/ml). Insulin and IGF-I (10 and 100 ng/ml) completely inhibited the lipolytic response to GH without affecting basal glycerol release. Insulin and IGF-I were equipotent in inhibiting GH-induced lipolysis while IGF-II is only 16% as potent as insulin.     

Inhibition of growth of hamster tumor cells in vitro by pyrrolidone carboxylic acid in a glutamine-dependent system

Summary Pyrrolidone carboxylic acid, which is formed spontaneously when glutamine is incubated at 37°C in a phosphate or bicarbonate medium, was found to inhibit growth of a line of hamster tumor cells which required glutamine for survival and growth. This investigation was supported in part by Grant CA-02568 from the National Cancer Institute, Bethesda, Maryland 20014.     

Inhibition of angiogenesis and angiogenesis-dependent tumor growth by the cryptic kringle fragments of human apolipoprotein(a)

Apolipoprotein(a) (apo(a)) contains tandemly repeated kringle domains that are closely related to plasminogen kringle 4, followed by a single kringle 5-like domain and an inactive protease-like domain. Recently, the anti-angiogenic activities of apo(a) have been demonstrated both in vitro and in vivo. However, its effects on tumor angiogenesis and the underlying mechanisms involved have not been fully elucidated. To evaluate the anti-angiogenic and anti-tumor activities of the apo(a) kringle domains and to elucidate their mechanism of action, we expressed the last three kringle domains of apo(a), KIV-9, KIV-10, and KV, in Escherichia coli. The resultant recombinant protein, termed rhLK68, exhibited a dose-dependent inhibition of basic fibroblast growth factor-stimulated human umbilical vein endothelial cell proliferation and migration in vitro and inhibited the neovascularization in chick chorioallantoic membranes in vivo. The ability of rhLK68 to abrogate the activation of extracellular signal-regulated kinases appears to be responsible for rhLK68-mediated anti-angiogenesis. Furthermore, systemic administration of rhLK68 suppressed human lung (A549) and colon (HCT-15) tumor growth in nude mice. Immunohistochemical examination and in situ hybridization analysis of the tumors showed a significant decrease in the number of blood vessels and the reduced expression of vascular endothelial growth factor, basic fibroblast growth factor, and angiogenin, indicating that suppression of angiogenesis may have played a significant role in the inhibition of tumor growth. Collectively, these results suggest that a truncated apo(a), rhLK68, is a potent anti-angiogenic and anti-tumor molecule.     

Inhibition of tumor growth by interleukin 10 gene transfer in B16(F10) melanoma cells

Interleukin 10 (IL-10) is a potent immunosuppressive cytokine with an antitumor activity. The effect of IL-10 on tumor growth was tested in murine melanoma cells manipulated by gene transfer to secrete IL-10. In mice bearing B16(F10) tumors expressing IL-10 tumor growth was decreased depending on the amount of secreted IL-10.     

Inhibition of somatotroph growth and growth hormone biosynthesis by activin in vitro

Activin-A, a homodimeric protein composed of two inhibin beta A-subunits, was first isolated from gonadal fluids based upon its ability to stimulate FSH secretion and biosynthesis, but was also observed to suppress GH secretion. The present report describes the effects of activin on the biosynthesis of GH and the proliferation of pituitary somatotrophs. In pituitary cells cultured in the presence of 0.7 nM activin for 3 days, GH secretion was decreased by 50% compared to the control value. Inhibition of GH biosynthesis, measured by quantitative immunoprecipitation of [35S]methionine-labeled cells, could be observed after 24 h of activin treatment, and maximal (70%) inhibition of GH biosynthesis was observed after 3 days. Activin inhibited basal as well as GH-releasing factor (GRF)-, glucocorticoid-, and thyroid hormone-stimulated GH biosynthesis. Inhibin, which is known to reverse the effect of activin on FSH secretion, did not reverse the effect of activin on GH biosynthesis. Treatment of somatotrophs with activin for 3 days completely inhibited the growth-promoting effect of GRF on somatotrophs. However, no effect of activin on GRF-stimulated expression of the c-fos protooncogene was observed. These data demonstrate that activin, in addition to its stimulatory effect on FSH secretion, is able to inhibit both expression of GH and growth of somatotropic cells.     

Inhibition of tumor growth mediated by lymphocytes sensitized in vitro to a syngeneic murine teratocarcinoma 402AX

TerC, a cell line derived from a strain 129 teratocarcinoma 402AX, was used to sensitize syngeneic 129 (H-2bc) splenic lymphocytes in vitro. The effector cells generated inhibited in vitro growth of TerC as measured by an 125I-IUDR ost-labeling technique. It was also shown, with a modified Winn assay, that the sensitized cells were effective in preventing TerC growth in vivo. The effector lymphocyte was nonadherent to nylon wool was sensitive to anti-Thy-1.2 + C, and was phenotypically Ly 1-2+. The anti-TerC effector T lymphocytes were not functional in a 51Cr-release assay. However, this failure to lyse appears not to be due to some intrinsic membrane resistance since both BCG and ConA-activated killers were able to lyse TerC. The TerC-sensitized lymphocytes displayed no H-2 restriction and were able to growth inhibit in vitro a wide range of tumorigenic cell lines, e.g., P815 (H-2d), EL-4 (H-2b),Sal (H-2a), and BALB/c (H-2d) 3T12. Mouse blastocyst cell lines were also inhibited. BALB/c 3T3 and mouse fibroblast cell strains were not growth inhibited. Thus, it appears that oncofetal antigens expressed on TerC are capable of initiating a cell-mediated response and that these antigenic specificities are shared by many transformed cell lines.     

Inhibition of poliovirus replication by an extract of Matricaria chamomilla (L)

Hydroalcoholic extract of Matricaria chamomilla added during the early stage of Poliovirus development inhibits cellular and viral RNA synthesis. This inhibition is partially reversible.     

Inhibition in aflatoxin biosynthesis by the extract of Amorphophallus campanulatus (OL) and calcium oxalate

A complete inhibition in aflatoxin production by Aspergillus flavus was observed with greater than 4.5 mg ml^-1 of 20 g 100 ml^-1 leaf extract of Amorphophallus campanulatus (OL). Suppression in growth was also well pronounced (81% at 8.0 mg ml^-1). The comparative efficacy of the corm of the plant was lower. Calcium oxalate, an important constituent of 'OL', completely checked the growth and toxin biosynthesis at 0.4 mg ml^-1 concentration.     

Plant regeneration from protoplasts of common buckwheat (fagopyrum esculentum)

Protoplasts were isolated from hypocotyls of etiolated seedlings from a diploid and the corresponding autotetraploid variety of common buckwheat (Fagopyrum esculentum). The isolated protoplasts started to divide after 4 days in culture in a modified MS medium. Maximum plating efficiency was approximately 1%. Regenerated calli derived from the tetraploid genotype developed roots easily but were recalcitrant to form shoots. Eighteen months following the initiation of cultures, tetraploid embryoids and shoots emerged after 3 weeks on an MS medium containing 0.1 mg/l gibberellic acid.Abbreviations 2,4-D 2,4 — dichlorophenoxyacetic acid - BAP 6-benzylaminopurine - GA gibberellic acid - MS Murashige and Skoog (1962) medium - NAA 1-naphthaleneacetic acid     

Inhibition of migration of tumor cells in vitro by lymphokine-containing supernatants.

Lymphokine-containing supernatants derived from seven different human lymphoid cell lines and lymphokine-containing supernatants from concanavalin A-stimulated murine lymphocytes were found to be capable of reversibly inhibiting the migration of tumor cells in vitro. The tumor cell lines used in these studies were the P815 mastocytoma, Ehrlich ascites, Walker carcinosarcoma, Hepatoma 129, and Sarcoma 37. Preliminary physiochemical evidence suggests that the mediator, here termed TMIF, is distinct from MIF. In any case, these results suggest the possibility that lymphokines other than lymphotoxin or macrophage-activating factors may play a role in tumor immunity.     

Inhibition of tumor cell growth by a human B-cell line

An Adenocarcinoma cell line (Breast-M) and an Epstein-Barr virus (EBV)-infected B-cell line (Hairy-BM) were established from breast tumor tissue. The Hairy-BM was CD20⁺, CD25 (Tac)+ and surface immunoglobulin (sIg)+. Hairy-BM suppressed the in vitro proliferation of Breast-M in a time and a dose-dependent manner. The suppression was also found in 5 different human tumor targets showing tumor-Hairy-BM binding, but not; in 2 murine tumor targets showing no significant tumor-Hairy-BM binding. Lytic activity of Hairy-BM was found only against Breast-M.Abbreviations sIg Surface immunoglobulin - CTL Cytotoxic T-cells - NK Natural killer - IL2 Interleukin 2 - LAK Lymphokine activated killer - CSN Culture supernatant - MTT 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoolium bromide - PCR Polymerase chain reaction - TIL Tumor-infiltrating lymphocytes - HCL Hairy cell leukemia - TNF Tumor necrosis factor