K. Lapis

Proteoglycans and tumor progression: Janus-faced molecules with contradictory functions in cancer.

Understanding the details of the molecular mechanism of tumor dissemination revealed that several proteoglycan species are involved in the process but their role can be described as Janus-faced. One level of proteoglycan alterations is at the expression of their genes coding for the core protein. Characteristically, in progressing tumors two patterns emerged: loss or neoexpression of surface proteoglycans (PG) depending on the initial expression pattern of the cell type of origin. The situation is similarly complex concerning the changes of glycosaminoglycan (GAG) of the PG during tumor progression. This is due to the fact that the majority of PGs involved is hybrid molecule meaning that their core protein can be glycanated both with chondroitin and heparan sulfate. However, such an alteration in glycanation of PG may fundamentally change the function of the molecule, especially the one operating at the cell surface. Among the extracellular PGs, decorin emerged as inhibitor of progression while perlecan as a promoter of the process. Analysis of the available data indicate that during metastatization tumor cells must express at least one cell surface HSPG species from the syndecan-glypican-CD44v3 group. Furthermore, the HS-chain of these proteoglycan(s) carry important molecular signatures (suphution or epimerization patterns). Experimental data suggest that tumor cell surface heparan sulfate (PG) may provide a target for specific anti-metastatic interventions.

Wheat germ extract decreases glucose uptake and RNA ribose formation but increases fatty acid synthesis in MIA pancreatic adenocarcinoma cells.

The fermented wheat germ extract with standardized benzoquinone composition has potent tumor propagation inhibitory properties. The authors show that this extract induces profound metabolic changes in cultured MIA pancreatic adenocarcinoma cells when the [1,2- 13 C 2 ]glucose isotope is used as the single tracer with biologic gas chromatography–mass spectrometry. MIA cells treated with 0.1, 1, and 10 mg/mL wheat germ extract showed a dose-dependent decrease in cell glucose consumption, uptake of isotope into ribosomal RNA (2.4%, 9.4%, and 28.0%), and release of 13 CO 2 . Conversely, direct glucose oxidation and ribose recycling in the pentose cycle showed a dose-dependent increase of 1.2%, 20.7%, and 93.4%. The newly synthesized fraction of cell palmitate and the 13 C enrichment of acetyl units were also significantly increased with all doses of wheat germ extract. The fermented wheat germ extract controls tumor propagation primarily by regulating glucose carbon redistribution between cell proliferation–related and cell differentiation–related macromolecules. Wheat germ extract treatment is likely associated with the phosphorylation and transcriptional regulation of metabolic enzymes that are involved in glucose carbon redistribution between cell proliferation–related structural and functional macromolecules (RNA, DNA) and the direct oxidative degradation of glucose, which have devastating consequences for the proliferation and survival of pancreatic adenocarcinoma cells in culture.

Effect of lentinan on macrophage cytotoxicity against metastatic tumor cells

We studied the effect of lentinan, a fungal polysaccharide immunomodulator, on mouse peritoneal macrophages. The i.p. treatment of mice with 10 mg/kg lentinan affected the number, plastic-adherence, and endogen peroxidase activity of peritoneal cells. The cytotoxicity of lentinan-stimulated peritoneal macrophages was determined against several murine and human metastatic tumor targets: Lewis lung carcinoma (LLT) and two human melanomas, and was found to be significantly higher than that of the macrophages from control animals. However, the highly metastatic variant of LLT (LLT-HH) was resistant to the cytolytic effect of resident and lentinan-activated macrophages as well, indicating that the stimulation for cytotoxicity depends not only on the functional activity of the effector but also on the sensitivity of the target.

Role of elastin-matrix interactions in tumor progression

Data from the literature now indicate that cancer cells can specifically interact with the unique extracellular matrix protein, elastin. The interaction is mediated by two elastin-binding proteins (EBP), S-gal/EBP (organized into the elasin receptor/elastonectin complex) and galectin-3, components of two laminin receptors. Studies revealed that the expression of both EBPs is closely associated to the invasive/metastatic potential of various cancer types. This is due to the fact that elastin-ligation of S-gal/EBP induces motogenic, as well as mitogenic signals and releases various elastases from cancer cells and the induction depends on the metastatic potential. Studies also demonstrated that certain cancer cells can synthesize elastin and express lysyl oxydase, providing explanation for frequent appearance of elastic tissue in tumors such as breast or gastric cancers. Clinico-pathological data suggest some correlation with tumor progression of the presence of the elastic tumor stroma. Since elastic tissue may be a significant reservoir of angiostatic molecule(s) this extracellular matrix protein can also have a role in tumor-induced angiogenesis. Soluble elastin as well as elastin peptides are potent inhibitors of the metastatic process in experimental tumor models. On the other hand, elastin peptides can also be used to design targeted therapies exploiting the unique physicochemical nature of this matrix protein. Altogether, these data suggest a significant role for tumor cell-elastin interactions in tumor progression.

Inhibitory effects of analogs of luteinizing hormone-releasing hormone and somatostatin on pancreatic cancers in hamsters events that accompany tumor regression

Syrian golden hamsters bearing N‐nitrosobis(2‐oxopropyl)amine (BOP)‐induced pancreatic carcinomas were treated for 2 months with the delayed delivery systems of the agonist D‐Trp‐6‐LH‐RH (microcapsules releasing 25 μg/day for 30 days), the somatostatin analog RC‐160 (the microcapsules liberating 48.2 μg/day for 30 days), or with the combination of these two analogues. The increase in the dose of RC‐160 was possible in view of the lack of toxicity of this analog. This higher dose of RC‐160 exerted a greater suppressive effect on pancreatic cancers than the regimens previously used (5‐25 μg/day). RC‐160, D‐Trp‐6‐LH‐RH, and their combination reduced the number of pancreatic carcinomas and significantly inhibited tumor growth as compared with the controls. The combination had the strongest tumor‐inhibitory effect and reduced tumor weight by 85% as compared with controls. Both the light and electron microscopic analysis of the tumors showed that the inhibitory effect was due to the enhancement of apoptosis (programmed cell death) of tumor cells. Insulin‐like growth factor (IGF‐I) receptors were detected immunohistochemically in the untreated tumors and their number decreased after the treatment with the analogues. Binding of D‐Trp‐6‐LH‐RH and RC‐160 to tumor cells was shown immunohistochemically and receptors to these analogues and IGF‐I were also determined biochemically by radioligand titration. Treatment with D‐Trp‐6‐LH‐RH and RC‐160 decreased the binding capacity of receptors for D‐Trp‐6‐LH‐RH and IGF‐I, producing down‐regulation of these receptors. This suggests that pancreatic tumor cells with receptors to these peptides are sensitive to the treatment. This work reinforces the view that the combination of high doses of somatostatin analog RC‐160 with LH‐RH agonists or antagonists should be considered for the development of a new hormonal therapy for ductal pancreatic cancers.

Platelet-Mimicry of Cancer Cells: Epiphenomenon with Clinical Significance

Stem cell mimicry of cancer cells has been known for a long time and is considered to be responsible for ectopic gene expressions. The stem cell characteristics of tumor cells are shown to be involved in epithelial-mesenchymal transition and in the phenomenon of vascular mimicry. Certain cancer types acquire a geno-phenotype closely resembling the platelets and express several megakaryocytic genes (adhesion receptors αIIbβ3, thrombin receptor and PECAM/CD31 and/or platelet-type 12-LOX) able to activate the coagulation cascade or the platelets themselves. Here we define these potentials as platelet mimicry of cancer cells typical of pancreatic, breast, prostate, colorectal and urogenital cancers and melanoma. Data all support that platelet mimicry of certain cancer types is an important factor in their hematogenous dissemination and provides an attractive therapeutic target. Besides the long-available preclinical data, clinical trials have only recently provided evidence that targeting platelet mimicry of cancers is an efficient way to prevent tumor progression. The systematic discovery of the markers of platelet mimicry in various cancer types and their molecular targeting may provide new supportive therapeutic modalities for the management of the progressing disease.

Interaction between elastin and tumor cell lines with different metastatic potential ; in vitro and in vivo studies

SummaryInteractions between the extracellular matrix macromolecules and tumor cells are critical in the process of metastasis formation. We show here that elastins (both mature insoluble elastin and a 75-kDa soluble peptide: κ-elastin) adhere rapidly to two cell lines with high metastatic capacities: a metastatic lung carcinoma cell line (3LL-HM) and a human amelanotic melanoma cell line (A-2058); by contrast the low-metastatic Lewis lung carcinoma cell line variant as well as a rhabdomyosarcoma cell line with a low metastatic potential bind to elastins to a much lower extent.3H-labelled κ-elastin was used in order to study elastin-3LL-HM interaction. It was found to be saturable (2 ng3H-labelled κ-elastin/106 cells), with one class of high-affinity binding sites having Kd equal to 1.3 nM and 16000 sites/cell. The binding of κ-elastin to 3LL-HM cells at its receptor triggered several cell responses; (a) increase of intracellular Ca2+ concentration; (b) induction of 3LL-HM chemotaxis toward the κ-elastin gradient; (c) stimulation of the adherence of mature insoluble elastin. In contrast to non-transformed cells such as fibroblasts and smooth muscle cells, the adhesion kinetics of insoluble elastin to 3LL-HM did not exhibit a lag period; the rapid binding of insoluble elastin to the tumor cells was followed by its slow detachment from the cells, which lasted for 6 h. 3LL-HM cells but not human skin fibroblasts were shown to secrete elastinolytic activity inhibitable by metal-chelating agents.In vivo studies were performed in order to evaluate the influence of κ-elastin binding to 3LL-HM cells on their ability to form lung colonies in mice. It was shown that pretreatment of 104 3LL-HM cells with 10 ΜMkelastin and the simultaneous i.v. injection into mice of 750 Μg κ-elastin together with the highly metastatic cells was able to reduce the number of lung colonies by more than 70% after 12 days.

Growth inhibition of MXT mammary carcinoma by enhancing programmed cell death (apoptosis) with analogs of LH-RH and somatostatin

BDF female mice inoculated with MXT mammary adenocarcinoma were treated for 30 days with microcapsules of the luteinizing hormone-releasing hormone (LH-RH) agonist D-Trp-6-LH-RH (releasing 25µg/day for 30 days), microcapsules of the somatostatin agonist RC-160 (liberating 25µg/day for one month), or the combination of these peptides. Bilateral surgical ovariectomy was performed in one group which served as an additional control. Tumor volume was measured weekly during the treatment period of 30 days. When tumor volume changes in the treated groups were compared to the corresponding changes in controls, the combination of D-Trp-6-LH-RH and RC-160 was the most effective in inhibiting tumor growth and approached the effect of surgical ovariectomy. At the conclusion of the experiment, tumor weights were also measured. All peptide analogs inhibited tumor weight by 42 to 63%. In the D-Trp-6-LH-RH treated group, ovarian weights and uterine weights decreased by 48% and 52%, respectively, as compared to controls. Histologically, the regressive changes in tumors caused by the treatment with RC-160, D-Trp-6-LH-RH and their combination were characterized by the coexistence of apoptosis (programmed cell death) and coagulation necrosis. The transition of apoptosis into coagulation necrosis was a common finding. The term ‘apoptotic index’ is proposed for the ratio of tumorous glands containing apoptotic cells. The apoptotic index was higher in the treated groups than in the control.

Effect of MSC on the immune response of mice

The supposed immunostimulatory actions of MSC, a new fermented wheat germ extract standardized to its benzoquinone composition (trade name: AVEMAR) were studied examining blastic transformation of peripheral blood lymphocytes of mice treated with MSC. It was found that MSC significantly increased the degree of blastic transformation caused by Concanavalin A. Using the B10LP to C57Bl skin graft system, MSC (0.03 and 3.0 g kg(-1) applied orally) acted in favour of restoring the immune function. On the other hand, 2,6-dimethoxy-p-benzoquinone (DMBQ), applied in equivalent doses (0.012 and 1.2 mg kg(-l)), did not shorten the rejection time of skin grafts. The immune restoring effect, as well as the blastic transformation enhancing potential of MSC may be exploited in various cases of decreased immune response.

Growth inhibition of estrogen independent MXT mouse mammary carcinomas in mice treated with an agonist or antagonist of LH-RH, an analog of somatostatin, or a combination.

SummaryFemale BDF1 mice inoculated with MXT (3.2) estrogen independent mouse mammary carcinoma were treated for three weeks with microcapsules of the luteinizing hormone-releasing hormone (LH-RH) agonist [D-Trp6]LH-RH, the antagonist SB-75, the somatostatin analog RC-160, or combinations. The lack of estrogen dependence of the tumor was proved by bilateral surgical ovariectomy, which had no effect. In two experiments, treatment with 25µg/day doses of each analog alone resulted in a significant inhibition of tumor growth as shown by a 40–53% inhibition of tumor volumes, 38–43% decrease in tumor weights, and histological signs of tumor regression. However, the combination of SB-75 or [D-Trp6]LH-RH with somatostatin analog RC-160 caused greater reduction of tumor volume (68 and 61%) or tumor weights (59 and 56%), than single analogs, and histologically the occurrence of apoptosis and decrease in AgNOR numbers was more pronounced in the groups receiving combination therapy. Specific binding sites for [D-Trp6]LH-RH, EGF, and IGF-I were demonstrated in the tumor membranes. The binding capacity of LH-RH receptors was decreased by treatment with the analogs, the greatest down-regulation being caused by combination therapy. A significant decrease in EGF binding capacity was observed after treatment with the LH-RH analogs, alone or especially in combination with somatostatin analog RC-160. The combination of these analogs also caused a reduction in IGF-I receptors. The finding that LH-RH agonists and antagonists and somatostatin analogs inhibit the growth of estrogen independent mammary tumors, and that combinations are more effective than single analogs, might be of practical importance in human breast cancer therapy.