Vitamin D3 and ceramide reduce the invasion of tumor cells through extracellular matrix components by elevating protein phosphatase-2A

Increasing phosphorylation reactions by protein kinase A (PKA) or reducing dephosphorylation reactions of protein phosphatase-2A (PP-2A) increases the invasiveness of Lewis lung carcinoma (LLC) cells, as measured by their capacity to traverse extracellular matrix (ECM)-coated filters. Metastatic LLC-LN7 variants have reduced PP-2A activity when compared to nonmetastatic LLC-C8 variants. Immunoblotting showed that this reduced level of PP-2A activity was not due to reduced levels of the PP-2A catalytic (C) subunit. The cellular PP-2A activity could be stimulated by addition of C2-ceramide to LLC-LN7 lysates, or by incubating cells with either C2-ceramide or with a noncalcemic analog of vitamin D3, which has previously been shown to stimulate the release of ceramide. These treatments to elevate PP-2A activity in metastatic LLC-LN7 cells resulted in a decline in their capacity to invade through select (ECM) components, particularly through vitronectin and laminin. Underscoring the importance of PP-2A in limiting the invasiveness of tumor cells was the demonstration that LLC-LN7 cell transfectants overexpressing the PP-2A C alpha subunit were less invasive through ECM components than the wild-type cells. Invasion by these cells was further reduced by additionally increasing PP-2A activity by incubation with C2-ceramide or the vitamin D3 analog. These results suggest a role of a vitamin D3/ceramide/PP-2A pathway in limiting the invasiveness of tumor cells through select ECM components.

Protein phosphatases-1 and -2A regulate tumor cell migration, invasion and cytoskeletal organization

The role of protein kinase A (PKA) and protein phosphatases (PP) -1 and -2A in regulating the metastatic phenotype of Lewis lung carcinoma (LLC) cells was evaluated. The metastatic LLC-LN7 cells were more motile and invasive than were nonmetastatic LLC-C8 cells. Compared to the nonmetastatic cells, the LLC-LN7 cells had increased PKA activity and a deficiency in PP-2A. Nonmetastatic LLC-C8 cells became migratory and invasive when PP-1 and P-2A activities were inhibited with okadaic acid. This stimulation of LLC-C8 motility was tempered by PKA inhibition. Also examined was if the okadaic acid-stimulated LLC-C8 motility was associated with a change in the cytoskeletal organization to that typical of metastatic cells. Treatment of nonmetastatic LLC-C8 cells with okadaic acid caused a redistribution of F-actin toward the periphery of the cells, and eventually to a loss of the filamentous actin network. All of these effects were reversed upon removal of okadaic acid. Our results show that PP-1/2A maintain reduced motility and increased cytoskeletal organization within nonmetastatic LLC cells.

Heparin-binding growth factor(s) derived from head and neck squamous cell carcinomas induce endothelial cell proliferations

BACKGROUND

Tumor growth is dependent on the expansion and proliferation of the host vascular system into the primary neoplasm (angiogenesis). The development of an intact vascular system requires migration and proliferation of endothelial cells and assembly into microvessels. Previous studies in our laboratory demonstrated that head and neck squamous cell carcinomas (HNSCC) are angiogenic in vivo. To clarify the mechanism of HNSCC-induced angiogenesis, the present study sought to determine if HNSCCs produced endothelial cell mitogens in vitro.

METHODS

Production of PGE-2, TGF-beta, FGF-2 (basic-FGF [fibroblast growth factor]), and vascular endothelial cell growth factor (VEGF) were quantitated by enzyme-linked immunoabsorbant assay (ELISA) in five HNSCC lines. Cell free supernatants of 5 HNSCC lines were tested in a nonradioactive proliferation assay using human umbilical vein endothelial cells (HUVECs).

RESULTS

All lines demonstrated enhanced endothelial cell proliferation in a dose-dependent fashion. Fractionation of these supernatants by heparin column chromatography significantly reduced endothelial cell proliferation in the five lines tested (range, 31.7% to 46.23% reduction; mean, 38.14+/-6.02%). Pretreatment with antibody to VEGF but not transforming growth factor (TGF)-beta inhibited endothelial cell proliferation.

CONCLUSIONS

These studies indicate HNSCCs produce factor(s) which stimulate endothelial cell proliferation and that VEGF may be involved in HNSCC-induced endothelial cell mitogenesis.

Nuclear accumulation of Saccharomyces cerevisiae Mcm3 is dependent on its nuclear localization sequence

BACKGROUND

The proteins of the Mcm2-7 family are required for the initiation of DNA replication. In Saccharomyces cerevisiae the nuclear envelope does not break down during the mitotic phase of the cell cycle. Large nuclear proteins, such as the Mcm proteins, which accumulate in the nucleus during specific portions of the cell cycle, must have regulated mechanisms to direct their entry into the nucleus.

RESULTS

We have identified a nuclear localization sequence (NLS) in Mcm3, and demonstrated that it is necessary for the translocation of Mcm3 into the nucleus and sufficient for directing Escherichia coli beta-galactosidase to the nucleus. Immediately adjacent to the nuclear localization sequence are four potential sites for phosphorylation by Cdc28. Mutagenesis of all four sites has no immediate phenotypic effect on cell growth or viability, nor does it affect nuclear accumulation of Mcm3, although two-dimensional protein gel analysis has shown that at least some of these sites are normally phosphorylated in vivo. Substitution of the Mcm3 NLS by the SV40 large T-antigen NLS also directs the nuclear accumulation of the Mcm3-T-antigen protein, although cell growth is compromised. Replication activity in cells bearing either the Mcm3-Cdc28 phosphorylation site mutations or the Mcm3 T-antigen NLS substitution, as measured by plasmid stability assays, is comparable to activity in wild-type cells.

CONCLUSIONS

The Mcm3 protein is imported into the nucleus by a specific NLS. The cell cycle specific nuclear accumulation of Mcm3 appears to be a result of nuclear retention or nuclear targeting, rather than nuclear import regulated through the NLS.

Association of arsenic-induced malignant transformation with DNA hypomethylation and aberrant gene expression

Inorganic arsenic, a human carcinogen, is enzymatically methylated for detoxication, consuming S-adenosyl-methionine (SAM) in the process. The fact that DNA methyltransferases (MeTases) require this same methyl donor suggests a role for methylation in arsenic carcinogenesis. Here we test the hypothesis that arsenic-induced initiation results from DNA hypomethylation caused by continuous methyl depletion. The hypothesis was tested by first inducing transformation in a rat liver epithelial cell line by chronic exposure to low levels of arsenic, as confirmed by the development of highly aggressive, malignant tumors after inoculation of cells into Nude mice. Global DNA hypomethylation occurred concurrently with malignant transformation and in the presence of depressed levels of S-adenosyl-methionine. Arsenic-induced DNA hypomethylation was a function of dose and exposure duration, and remained constant even after withdrawal of arsenic. Hyperexpressibility of the MT gene, a gene for which expression is clearly controlled by DNA methylation, was also detected in transformed cells. Acute arsenic or arsenic at nontransforming levels did not induce global hypomethylation of DNA. Whereas transcription of DNA MeTase was elevated, the MeTase enzymatic activity was reduced with arsenic transformation. Taken together, these results indicate arsenic can act as a carcinogen by inducing DNA hypomethylation, which in turn facilitates aberrant gene expression, and they constitute a tenable theory of mechanism in arsenic carcinogenesis.

Mcm2 and Mcm3 are constitutive nuclear proteins that exhibit distinct isoforms and bind chromatin during specific cell cycle stages of Saccharomyces cerevisiae

The Mcm2-7 proteins are a family of conserved proteins whose functions are essential for the initiation of DNA synthesis in all eukaryotes. These patients are constitutively present in high abundance in actively proliferating cells. In Saccharomyces cerevisiae, the intracellular concentrations of Mcms are between 100 and 500 times the number of replication origins. However, these proteins are limiting for the initiation of DNA synthesis at replication origins. Our studies indicate that only a small fraction of Mcm2 and Mcm3 tightly associates with chromatin, from late M phase to the beginning of the S phase. The rest of the Mcm2 and Mcm3 proteins are disturbed to both the cytoplasm and nucleoplasm in relatively constant levels throughout the cell cycle. We also show that S. cerevisiae Mcm3 is a phosphoprotein that exists in multiple isoforms and that distinct isoforms of Mcm2 and Mcm3 can be detected at specific stages of the cell cycle. These results suggest that the localization and function of the Mcm proteins are regulated by posttranslational phosphorylation in a manner that is consistent with a role for the Mcm proteins in restricting DNA replication to once per cell cycle.

Myeloid differentiation treatment to diminish the presence of immune-suppressive CD34+ cells within human head and neck squamous cell carcinomas

Within human head and neck squamous cell carcinomas (HNSCC) that produce granulocyte-macrophage CSF are CD34+ cells that exhibit natural suppressive (NS) activity. The present study aimed to identify how these NS cells mediate suppression and how to diminish their presence. CD34+ cells that were immunomagnetically isolated from fresh surgical HNSCC specimens produced a soluble product that blocked normal T cell stimulation through the TCR/CD3 complex. This inhibitory activity could be neutralized with Abs to TGF-beta1. Since prior studies showed that the CD34+ NS cells within HNSCC cancers are myelomonocytic progenitor cells, the feasibility of using cytokines that can induce myeloid cell differentiation to diminish the presence of CD34+ NS cells was tested. Adding low doses of 100 U/ml IFN-gamma plus 10 U/ml TNF-alpha to bulk cultures of dissociated HNSCC cancers diminished the frequency of CD34+ cells. Studies with CD34+ cells that were isolated from the HNSCC cancers showed that this cytokine treatment induced differentiation of the CD34+ cells predominantly into monocytic cells. The consequence of treating CD34+ NS cells with the myeloid differentiation treatment was the loss of suppressive activity, a decline in TGF-beta production, and the production of TNF-alpha by the resulting monocytic cells. In HNSCC bulk cultures containing high levels of CD34+ NS activity, IFN-gamma/TNF-alpha not only reduced CD34+ cell levels, but also increased the capacity of the intratumoral T cells to express the p55 IL-2R. These studies show that IFN-gamma/TNF-alpha can induce differentiation of TGF-beta-secreting CD34+ NS cells into nonsuppressive monocytic cells that secrete TNF-alpha.

Myeloid differentiation treatment to diminish the presence of immune-suppressive CD34+ cells within human head and neck squamous cell carcinomas

Within human head and neck squamous cell carcinomas (HNSCC) that produce granulocyte-macrophage CSF are CD34+ cells that exhibit natural suppressive (NS) activity. The present study aimed to identify how these NS cells mediate suppression and how to diminish their presence. CD34+ cells that were immunomagnetically isolated from fresh surgical HNSCC specimens produced a soluble product that blocked normal T cell stimulation through the TCR/CD3 complex. This inhibitory activity could be neutralized with Abs to TGF-beta1. Since prior studies showed that the CD34+ NS cells within HNSCC cancers are myelomonocytic progenitor cells, the feasibility of using cytokines that can induce myeloid cell differentiation to diminish the presence of CD34+ NS cells was tested. Adding low doses of 100 U/ml IFN-gamma plus 10 U/ml TNF-alpha to bulk cultures of dissociated HNSCC cancers diminished the frequency of CD34+ cells. Studies with CD34+ cells that were isolated from the HNSCC cancers showed that this cytokine treatment induced differentiation of the CD34+ cells predominantly into monocytic cells. The consequence of treating CD34+ NS cells with the myeloid differentiation treatment was the loss of suppressive activity, a decline in TGF-beta production, and the production of TNF-alpha by the resulting monocytic cells. In HNSCC bulk cultures containing high levels of CD34+ NS activity, IFN-gamma/TNF-alpha not only reduced CD34+ cell levels, but also increased the capacity of the intratumoral T cells to express the p55 IL-2R. These studies show that IFN-gamma/TNF-alpha can induce differentiation of TGF-beta-secreting CD34+ NS cells into nonsuppressive monocytic cells that secrete TNF-alpha.

Inhibition of tumor invasiveness by 1alpha,25-dihydroxyvitamin D3 coupled to a decline in protein kinase A activity and an increase in cytoskeletal organization

The capacity of cloned metastatic Lewis lung carcinoma cells (LLC-LN7) to invade through reconstituted basement membrane-coated filters was reduced after incubation with 1alpha,25-dihydroxyvitamin D3 [1,25(OH)2D3]. This was observed at doses as low as 10(-10) M 1,25(OH)2D3. The 1,25(OH)2D3-treated cells also had reduced levels of protein kinase A (PKA) activity and an increase in the level of polymerized actin, properties that have previously been demonstrated for less metastatic LLC variants. In addition, levels of the intermediate filament protein vimentin increased in 1,25(OH)2D3-treated LLC-LN7 tumor cells. In contrast, the levels and distribution of tubulin were not affected by 1,25(OH)2D3. The possibility that the decline in PKA activity was involved in the 1,25(OH)2D3 modulation of the cytoskeletal components was evaluated. To accomplish this, LLC-7 transfectants whose PKA levels were blocked due to expression of a mutated PKA R(1alpha) subunit (LN7-REV) were incubated with 1,25(OH)2D3 and their levels of F-actin were measured. In the absence of 1,25(OH)2D3 treatment, the PKA-defective LN7-REV cells had an increased level of polymerized actin as compared to the wild-type LLC-LN7 cells. This level of F-actin was minimally affected by 1,25(OH)2D3, suggesting that PKA activity is required for 1,25(OH)2D3 modulation of actin polymerization. These studies show that 1,25(OH)2D3 can reduce PKA activity in tumor cells, and that this reduction in PKA may be an intermediate signal through which 1,25(OH)2D3 affects the cytoskeleton and diminishes tumor invasiveness.

Correlation of middle meatal and maxillary sinus cultures in acute maxillary sinusitis

Cultures obtained from the middle meatus have been used frequently in the past to direct therapy in patients with acute maxillary sinusitis. However, no convincing data have been published to indicate that middle meatal cultures accurately represent the bacterial flora within the maxillary sinus. The hypothesis of this experiment is that bacteria obtained by directed middle meatal cultures qualitatively and quantitatively correlate with cultures taken by maxillary sinus puncture. Acute sinusitis was induced by injecting 10(8) colony-forming units of bacteria directly into the maxillary sinuses of rabbits in which the ostia were occluded with cotton packs. Eight animals were injected with Staphylococcus aureus, eight with Haemophilus influenzae, and eight with Streptococcus pneumoniae. The packs were removed after 3 days, and specimens were obtained from the middle meatus in the region of the maxillary sinus ostium, and from the maxillary sinus, 1 day later. The contralateral maxillary sinuses of six of the animals were injected with normal saline and served as controls. There was a 100% correlation rate between cultures of specimens obtained from the maxillary sinus and from the middle meatus in all 24 animals. In addition, the quantitative counts from the middle meatus and the maxillary sinus correlated. Control animals showed no bacterial growth from either the middle meatus or the maxillary sinus. These results show that, in an animal model of acute sinusitis, cultures of specimens from the middle meatus reflect the contents of the maxillary sinus.

Increased recurrence and metastasis in patients whose primary head and neck squamous cell carcinomas secreted granulocyte-macrophage colony-stimulating factor and contained CD34+ natural suppressor cells

Human head and neck squamous cell carcinomas (HNSCC) that produce high levels of granulocyte-macrophage colony-stimulating factor (GM-CSF) have been shown to contain CD34+ natural suppressor cells that inhibit the activity of intratumoral T-cells. The present study evaluated whether GM-CSF production and the presence of CD34+ cells within primary HNSCC would translate into increased recurrence, metastasis or cancer-related death during the 2 years following surgical excision. Freshly excised primary HNSCC of 20 patients that subsequently developed disease, and of 17 patients that remained with no evidence of disease were analyzed for production of GM-CSF and for CD34+ cell content. The cancers of patients that subsequently developed recurrences or metastatic disease produced almost 4-fold the levels of GM-CSF and had approximately 2.5-fold the number of CD34+ cells as did cancers of patients that remained disease-free. In a second method of analysis, the prognostic significance of high vs. low GM-CSF and CD34+ cell values was evaluated. These analyses showed that patients whose cancers produced high GM-CSF levels or had a high CD34+ cell content had a disproportionately high incidence of recurrence or metastatic disease (94% and 100%, respectively), while the majority of patients whose primary cancers produced low levels of GM-CSF or had a low CD34+ cell content remained disease-free (16% and 19%, respectively). Our results indicate that the presence of CD34+ cells in GM-CSF-producing HNSCC is associated with a poorer prognosis for the cancer patients and suggest the utility of these parameters as prognostic indicators of outcome. Mechanistically, our results suggest that the presence of immune suppressive CD34+ cells in GM-CSF-producing HNSCC leads to increased tumor recurrence or metastasis.

Protein phosphatase-2A association with microtubules and its role in restricting the invasiveness of human head and neck squamous cell carcinoma cells

The role of protein phosphatase-2A (PP-2A) in regulating the motility and adhesion of human head and neck squamous cell carcinomas (HNSCC) was investigated. Immunofluorescent staining of these HNSCC cells showed PP-2A can co-localize with microtubules. That the PP-2A influences motility was shown by the increase in HNSCC cell migration through laminin and vitronectin when PP-2A was selectively inhibited with low dose okadaic acid, and by the reduction in invasion through these same matrix components by elevators of PP-2A activity. Motility of HNSCC cells through collagen I or fibronectin was not modulated by PP-2A. The reduction in HNSCC migration through vitronectin or laminin that resulted from treatment with PP-2A elevators was associated with an increase in cellular adhesiveness to these same ECM components. These studies show the association of PP-2A with the cellular cytoskeleton and its role in restricting the invasiveness of tumor cells through select extracellular matrix components.

Increased interleukin-6 production by cerebral cortical tissue of adult versus young mice

The cytokine interleukin-6 (IL-6) has been implicated as a contributor to injury in several neurological disorders. The amounts of IL-6 released by the cerebral cortical tissue of mice of varying maturational age groups were measured and found to increase with age. Specifically, the basal level of IL-6 released from the tissue of infant (less than 2 weeks old) mice was low, although the tissue could be readily stimulated to secrete high levels of IL-6. Higher levels of IL-6 were released from young adult (2 month old) mice. Adult mice that were either 6 or 9 months of age secreted significantly higher levels of IL-6 compared to the tissue of either the young adult or infant animals, although the difference between levels secreted by the 6- or 9-month old groups was minimal. IL-6 production by adult cerebral cortical tissue could be further stimulated, but it was less readily achieved compared to the tissue of infants. In response to the negative regulator transforming growth factor-beta (TGF-beta), the levels of IL-6 released by stimulated cerebral cortical tissue of infants, as well as by unstimulated and stimulated tissue of adults, were reduced to the low basal levels of IL-6 produced by infant tissue. These results suggest that normal development and aging are correlated with an increase in IL-6 production that may be due to shifts in levels of stimulatory or inhibitory regulatory controls, but not to an inability of young tissue to produce IL-6 or to a lack of responsiveness of adult tissue to negative regulatory control by TGF-beta.

Lipid peroxidation assessment of free radical production following release of obstructive uropathy

PURPOSE

To identify if free radicals were released following relief of ureteric obstruction.

MATERIALS AND METHODS

Free radical production was assessed by a high performance liquid chromatography assay of malondialdehyde (MDA) in a 24-hour complete unilateral ureteric obstruction model in Wistar rats.

RESULTS

In the first experiment, a rise greater than 20% above prerelease levels in renal venous malondialdehyde levels was observed at 8, 15, 22, and 30 minutes following release. At 45 and 60 minutes, levels were similar to the prerelease levels. In the second experiment, renal venous samples taken before release and at 10 and 20 minutes after release in control and obstructed groups (n = 7) identified a significant difference (T = 10 minutes p = 0.006 and T = 20 minutes p = 0.045). A significant MDA rise following release occurred only in the obstructed group (obstruction group; MDA level T = 0 min. 1.01 mumol/l. +/- 0.13, T = 10 min. 2.12 mumol/l. +/- 0.3 p = 0.016, T = 20 min. 2.09 mumol/l. +/- 0.28 p = 0.016.

CONTROL GROUP

T = 0 min. 1.13 mumol/l. +/- 0.23, T = 10 min. 1.05 mumol/l. +/- 0.18 p = 0.95, T = 20 min. 1.23 mumol/l. +/- 0.19 p = 0.67). In the third experiment, an attempt was made to block free radical release with allopurinol. No statistical difference between the control and obstructed groups with allopurinol was noted at 20 minutes after release. A Kruskal Wallace two-way analysis identified a significant difference between experiments two and three at both time periods (p = 0.049).

CONCLUSION

This study suggests, for the first time, that free radicals are released after relief of ureteric obstruction and that this release is partially attenuated by allopurinol pretreatment.

cDNA cloning and characterisation of a maize homologue of the MCM proteins required for the initiation of DNA replication

A central question in cell cycle regulation is how DNA replication is initiated and executed only once in each cell cycle. The cell cycle-regulated assembly of specific initiation protein complexes at chromosomal origins appears to specify the initial sites and timing of DNA replication, and to restrict this process to only one round in the somatic cell cycle. Among the enzymes involved in origin activation, the MCM proteins play a conserved key role. In particular, MCM3 homologues have been shown to be components of the DNA replication licensing activity in yeast and vertebrates. In spite of our detailed knowledge of the regulation of the initiation of DNA synthesis in yeast, there is virtually no information available on the molecules involved in origin activation in higher plants. We have isolated a cDNA from maize root apices, termed ROA (Replication Origin Activator), encoding a protein which shares a high degree of homology with the MCM3 subfamily of MCM proteins. Analysis of gene organisation by Southern blotting shows 2-4 copies per haploid genome of closely related ROA sequences and the presence of further less related sequences in a multigene family. The steady-state levels of ROA mRNA are under developmental control, being relatively high in proliferative tissues such as the root apex, the developing cob and the coleoptile, and are strongly correlated with that of the histone H4 transcript. In situ hybridisation analysis in the root apex reveals that ROA mRNA expression is limited to specific subpopulations of cycling cells, which is typical of cell cycle-regulated expression. The isolation of nearly identical sequences from barley and Arabidopsis by the polymerase chain reaction indicates that MCM-related proteins are conserved in higher plants.

Mechanisms of immune suppression in patients with head and neck cancer: influence on the immune infiltrate of the cancer

Freshly excised human head and neck cancers (219 primary cancers; 64 metastatic lymph node cancers) were analyzed for the immune inhibitory mediators released from the cancer tissues and the immune infiltrate within the tumor. Significant levels of the immune inhibitory mediators transforming growth factor-beta (TGF-beta), prostaglandin E2 (PGE2) and interleukin-10 (IL-10) were released from these cancers. Also released was granulocyte-macrophage colony-stimulating factor (GM-CSF), whose secretion was associated with an intratumoral presence of CD34+ cells. We have previously shown that CD34+ cells within human head and neck cancers are immune inhibitory granulocyte-macrophage progenitor cells. The presence of TGF-beta, PGE2 and IL-10 was associated with a reduced content of CD8+ T-cells within the cancers. The CD4+ cell content appeared to be less affected by these immune inhibitory mediators. Instead, parameters indicative of CD4+ cell function (p55 IL-2 receptor expression, release of IL-2 and IFN-gamma) were diminished in cancers that released higher levels of TGF-beta, IL-10 and GM-CSF and had a higher CD34+ cell content. Furthermore, metastatic cancers released higher levels of the soluble immune inhibitory mediators and lower levels of IFN-gamma and IL-2 than did primary cancers, although CD34+ cells were similarly present in both primary and metastatic cancers. Our results show that human head and neck cancers have a multiplicity of non-mutually exclusive mechanisms of immune suppression that are most prominently associated with reduced CD8+ cell influx and reduced influx and altered function of intratumoral CD4+ cells.

Vitamin D3 treatment of tumor bearers can stimulate immune competence and reduce tumor growth when treatment coincides with a heightened presence of natural suppressor cells

By secreting granulocyte-macrophage colony-stimulating factor (GM-CSF), Lewis lung carcinoma tumors induce immune suppressive granulocyte-macrophage progenitor cells. Treating mice having established tumors and high levels of suppressor activity with vitamin D3 eliminated suppressor activity, increased anti-tumor immunity, induced an immune stimulatory cell population, and reduced tumor growth. When instead, the vitamin D3 treatment was initiated earlier, when implanted tumors first became detectable and when natural suppressor activity was less prominent, the treatment had no effect. Thus, vitamin D3 treatment can stimulate the immune competence of tumor bearers when treatment is targeted to coincide with a heightened presence of GM-CSF-induced suppressor cells.

Protein kinase A regulates Lewis lung carcinoma adherence to extracellular matrix components and spontaneous metastasis

Tumor cell adhesion to and migration through the extracellular matrix (ECM) can influence their capacity to disseminate. Since prior studies with Lewis lung carcinoma (LLC) tumors had shown metastatic clones to have more protein kinase A (PKA) activity than nonmetastatic clones, the present study assessed if PKA regulates the interaction between tumor and the ECM, and how this may be associated with the metastatic capacity of the tumor cells. This was accomplished with the use of metastatic (LLC-LN7) and nonmetastatic (LLC-C8) variants that had been stably transfected to overexpress the PKA Calpha subunit or to have blocked PKA activity. Cells with increased PKA activity were less adherent to vitronectin, laminin, and collagen I, and could more readily migrate through these ECM components than could transfectants with reduced PKA activity. PKA did not regulate adhesion to or migration through fibronectin, and did not appear to be associated with changes in expression of surface integrins. In addition to modulating tumor adhesion and migration in vitro, PKA activation caused an increased formation of metastases from s.c. tumors, but did not regulate formation of experimental metastases by i.v. injected tumor cells. These results suggest that PKA signaling is important for modulating the tumor-ECM interaction and can facilitate tumor transit from the primary tumor site.

Immune modulation by interleukin-12 in tumor-bearing mice receiving vitamin D3 treatments to block induction of immunosuppressive granulocyte/macrophage progenitor cells

Lewis lung carcinoma (LLC-LN7) tumors stimulate myelopoiesis and increase the presence of granulocyte/macrophage (GM) progenitor cells having natural suppressor activity. Treatment of these tumor-bearing mice with interleukin-12 (IL-12) resulted in minimal immune modulation. The objective of this study was to determine whether eliminating natural suppressor activity would allow for immune stimulation by IL-12. Treatment of LLC-LN7 tumor-bearing mice with vitamin D3 eliminated natural suppressor activity. In mice that were first treated with vitamin D3 and then also with IL-12, there was stimulation of splenic T cell proliferation in response to immobilized anti-CD3 plus IL-2. In addition, spleen and lymph node cells from vitamin-D3/IL-12-treated tumor-bearing mice became stimulated in response to autologous tumor to produce interferon gamma (IFN gamma), although IL-2 production was not stimulated. A prominent effect of the combined vitamin-D3/IL-12 treatment regimen was the synergistic augmentation of autologous tumor-specific cytolytic activity within the regional lymph nodes. The generation of these tumor-specific effector cells required the presence of the tumor mass since such activity was not elicited in the lymph nodes of mice from which the tumors had been surgically excised. The results of this study show that, after treatment of tumor bearers with vitamin D3 to eliminate GM-suppressor cells, IL-12 can induce select regional antitumor immune responses, particularly IFN gamma production and cytolysis by regional lymph node cells of autologous tumor.

Suppression of T cell proliferation by tumor-induced granulocyte-macrophage progenitor cells producing transforming growth factor-beta and nitric oxide

Production of high levels of granulocyte-macrophage CSF (GM-CSF) by LLC-LN7 tumors results in myelopoietic stimulation and an increase in cells having natural suppressor (NS) activity. Prior studies showed these NS cells could be isolated from the bone marrow of tumor-bearing mice with an Ab (ER-MP12) that recognized GM-progenitor cells. The present study showed these cells to also be in the spleen, lymph node, and tumor, and that treatment of tumor-bearing mice with low doses of IFN-gamma plus TNF-alpha reduced the frequency of E-MP12+ cells. Studies focused on characterizing the intratumoral ER-MP12+ cells and the mechanism by which they suppress T cell proliferation. When isolated and seeded in soft agar with CSF-containing LLC-LN7 supernatants, the ER-MP12+ cells grew into colonies, most of which contained both granulocytic and monocytic cells. Tumor-derived ER-MP12+ cells and their culture supernatants were suppressive to T cell proliferation. Among the factors produced by ER-MP12+ cells were TGF-beta, nitric oxide (NO), IL-10, and prostaglandin E2 (PGE2). However, it was TGF-beta and NO that mediated the suppression of T cell proliferation by ER-MP12+ cells. Intratumoral ER-MP12+ cells could be maintained as suppressive blastlike cells for at least 4 days in cultures containing CSFs, but adding IFN-gamma plus TNF-alpha to these cultures caused their differentiation mainly into nonsuppressive TNF-alpha-secreting monocytic cells. These results show that intratumoral ER-MP12+ cells having homology to GM-progenitor cells suppress T cell function by producing TGF-beta and NO. IFN-gamma/TNF-alpha treatment stimulates their differentiation and shift from production of TGF-beta and NO to production of TNF-alpha.

Suppression of T cell proliferation by tumor-induced granulocyte-macrophage progenitor cells producing transforming growth factor-beta and nitric oxide

Production of high levels of granulocyte-macrophage CSF (GM-CSF) by LLC-LN7 tumors results in myelopoietic stimulation and an increase in cells having natural suppressor (NS) activity. Prior studies showed these NS cells could be isolated from the bone marrow of tumor-bearing mice with an Ab (ER-MP12) that recognized GM-progenitor cells. The present study showed these cells to also be in the spleen, lymph node, and tumor, and that treatment of tumor-bearing mice with low doses of IFN-gamma plus TNF-alpha reduced the frequency of E-MP12+ cells. Studies focused on characterizing the intratumoral ER-MP12+ cells and the mechanism by which they suppress T cell proliferation. When isolated and seeded in soft agar with CSF-containing LLC-LN7 supernatants, the ER-MP12+ cells grew into colonies, most of which contained both granulocytic and monocytic cells. Tumor-derived ER-MP12+ cells and their culture supernatants were suppressive to T cell proliferation. Among the factors produced by ER-MP12+ cells were TGF-beta, nitric oxide (NO), IL-10, and prostaglandin E2 (PGE2). However, it was TGF-beta and NO that mediated the suppression of T cell proliferation by ER-MP12+ cells. Intratumoral ER-MP12+ cells could be maintained as suppressive blastlike cells for at least 4 days in cultures containing CSFs, but adding IFN-gamma plus TNF-alpha to these cultures caused their differentiation mainly into nonsuppressive TNF-alpha-secreting monocytic cells. These results show that intratumoral ER-MP12+ cells having homology to GM-progenitor cells suppress T cell function by producing TGF-beta and NO. IFN-gamma/TNF-alpha treatment stimulates their differentiation and shift from production of TGF-beta and NO to production of TNF-alpha.

Prostaglandin E2-protein kinase A signaling and protein phosphatases-1 and -2A regulate human head and neck squamous cell carcinoma motility, adherence, and cytoskeletal organization

Human head and neck squamous cell carcinoma (HNSCC) cultures were established from cancers of two patients. These cells were used to study if phosphorylation reactions by protein kinase A (PKA) and dephosphorylation reactions by protein phosphatases-1 and -2A (PP-1/2A) regulate tumor motility and adhesion to extracellular matrix components, and if this might be associated with cytoskeletal reorganization. Both cultures were motile and adherent to collagen I, fibronectin, vitronectin and laminin. Motility and adhesiveness was dependent on production of prostaglandin E2 PGE2 and on PKA activation. Blocking PP-1/2A activity with okadaic acid resulted in a PKA-dependent increase in m otility and, in some instances, adhesiveness by the HNSCC cells. The okadaic acid-induced increase in motility and adhesiveness coincided with a reduction in filamentous actin. These data suggest PKA and PP-1/2A have opposing effects in regulating the motility, adherence, and actin polymerization.

Bi-directional stimulation of adherence to extracellular matrix components by human head and neck squamous carcinoma cells and endothelial cells

Head and neck squamous cell carcinoma (HNSCC) cultures were established from two patients to determine if cancer and endothelial cells bi-directionally regulate their adherence to extracellular matrix components (ECM), an important process for tumor vascularization and metastasis. Soluble products from endothelial cells transiently enhanced adherence by HNSCC to ECM and increased surface levels of beta 1 and beta 4 integrins, although not beta 3. HNSCC products enhanced endothelial cell adherence to fibronectin and laminin, and beta 1 and beta 4 expression. These data show bi-directional enhancement of adherence to ECM and integrin expression among endothelial and tumor cells, which may facilitate metastasis and neovascularization.

The involvement of metabotropic glutamate receptors and their intracellular signalling pathways in sustained nociceptive transmission in rat dorsal horn neurons

The excitatory responses of individual dorsal horn neurons to cutaneous brush, repeated application of the C-fibre-selective chemical algogen, mustard oil, or to ionophoretic (1S,3R)-ACPD [a metabotropic glutamate receptor (mGluR) agonist] were monitored by extracellular recording. We have previously shown that the responses of dorsal horn neurons to mustard oil are inhibited by several selective antagonists of mGluRs. Effects of ionophoresis of the mGluR antagonists (R,S)-CHPG and L-AP3 and a range of selective inhibitors of intracellular signalling pathways were examined on evoked responses here. The results suggest that protein kinase C, phospholipase A2 and perhaps Ca2+/calmodulin kinase II play a role in mediating the sustained elevated activity of dorsal horn neurons that is incrementally elicited by repeated application of mustard oil, but probably make little contribution to sustained brush-evoked activity. Concurrence in the sensitivity of mustard oil- and (1S,3R)-ACPD-evoked activity to (R,S)-CHPG, L-AP3 and to inhibitors of intracellular signalling pathways, suggests that mGluRs are an important origin of these intracellular signals required for sustained nociception.

Treating tumor-bearing mice with vitamin D3 diminishes tumor-induced myelopoiesis and associated immunosuppression, and reduces tumor metastasis and recurrence

Metastatic Lewis lung carcinoma (LLC-LN7) tumors that secrete granulocyte/macrophage-colony-stimulating factor (GM-CSF) stimulate myelopoiesis and induce bone marrow-derived immunosuppressor cells that are homologous to granulocyte/macrophage progenitor cells. In vitro treatment of the LLC-LN7 cells with 1 alpha,25-dihydroxyvitamin D3 reduced tumor cell production of suppressor-inducing activity, although suppressor-inducing activity could be restored by reconstituting the tumor supernatants with recombinant GM-CSF. Treatment of mice having LLC-LN7 tumors with vitamin D3 reduced tumor production of GM-CSF and the frequency of myeloid progenitor cells. This was associated with a reduction in immunosuppressor activity and an increase in T cell function. Vitamin D3 treatment of mice having palpable tumors transiently retarded tumor growth, but caused a prominent reduction in tumor metastasis. Treating mice with vitamin D3 after tumor excision resulted in a reduction in the tumor-induced myelopoietic stimulation and associated immunosuppressive activity, and enhanced T cell function. These mice had a markedly reduced incidence of tumor recurrence. The results of this study suggest that vitamin D3 treatment of mice with GM-CSF-secreting tumors can interrupt the myelopoiesis-associated immunosuppressor cascade and, in turn, reduce tumor metastasis and recurrence.