Tumor vascular permeability factor stimulates endothelial cell growth and angiogenesis.

Vascular permeability factor (VPF) is an Mr 40-kD protein that has been purified from the conditioned medium of guinea pig line 10 tumor cells grown in vitro, and increases fluid permeability from blood vessels when injected intradermally. Addition of VPF to cultures of vascular endothelial cells in vitro unexpectedly stimulated cellular proliferation. VPF promoted the growth of new blood vessels when administered into healing rabbit bone grafts or rat corneas. The identity of the growth factor activity with VPF was established in four ways: (a) the molecular weight of the activity in preparative SDS-PAGE was the same as VPF (Mr approximately 40 kD); (b) multiple isoforms (pI greater than or equal to 8) for both VPF and the growth-promoting activity were observed; (c) a single, unique NH2-terminal amino acid sequence was obtained; (d) both growth factor and permeability-enhancing activities were immunoadsorbed using antipeptide IgG that recognized the amino terminus of VPF. Furthermore, 125I-VPF was shown to bind specifically and with high affinity to endothelial cells in vitro and could be chemically cross-linked to a high-molecular weight cell surface receptor, thus demonstrating a mechanism whereby VPF can interact directly with endothelial cells. Unlike other endothelial cell growth factors, VPF did not stimulate [3H]thymidine incorporation or promote growth of other cell types including mouse 3T3 fibroblasts or bovine smooth muscle cells. VPF, therefore, appears to be unique in its ability to specifically promote increased vascular permeability, endothelial cell growth, and angio-genesis.     

Tumor growth enhances cross-presentation leading to limited T cell activation without tolerance

Using a tumor model of spontaneously arising insulinomas expressing a defined tumor-associated antigen, we investigated whether tumor growth promotes cross-presentation and tolerance of tumor-specific T cells. We found that an advanced tumor burden enhanced cross-presentation of tumor-associated antigens to high avidity tumor-specific T cells, inducing T cell proliferation and limited effector function in vivo. However, contrary to other models, tumor-specific T cells were not tolerized despite a high tumor burden. In fact, in tumor-bearing mice, persistence and responsiveness of adoptively transferred tumor-specific T cells were enhanced. Accordingly, a potent T cell-mediated antitumor response could be elicited by intravenous administration of tumor-derived peptide and agonistic anti-CD40 antibody or viral immunization and reimmunization. Thus, in this model, tumor growth promotes activation of high avidity tumor-specific T cells instead of tolerance. Therefore, the host remains responsive to T cell immunotherapy.     

Tumor growth suppression by adenovirus-mediated introduction of a cell growth suppressing gene tob in a pancreatic cancer model

TOB (transducer of ErbB-2) is a tumor suppressor that interacts with protein-tyrosine kinase receptors, including ErbB-2. Introduction of the tob gene into NIH3T3 cells results in cell growth suppression. In this study, we evaluated the effect of tob expression in pancreatic cell lines (AsPC-1, BxPC-3, SOJ) and discuss the tumor-suppressing effects of adenoviral vector expressing tob cDNA. We first measured the levels of endogenous tob mRNA being expressed in all pancreatic cancer cell lines. Then, we examined the effect of adenoviral vector containing tob cDNA (Ad-tob vector) on cancer cell lines. The viral vector was expanded with transfection in 293 cells. The titer of the vector was 350 × 10⁶ pfu/ml. These cancer cells were able to be transfected with MOI 20 without adenoviral toxicity. The transfection of Ad-tob vector results in growth suppression of SOJ and AsPC-1 cell lines. The magnitude of the expression of the Ad-tob gene in cancer is correlated to tumor suppressive activity. We prepared pancreatic cancer peritonitis models using a peritoneal injection of AsPC-1 cells. In this model, bloody ascites and multiple tumor nodules were seen at the mesentery after 16 days. AdCAtob (50 × 10⁶ pfu/day) was administered from day 5 to day 9 after 4 days of peritoneal injection of 2 × 10⁶ AsPC-1 cells. Tumor growth suppression occurred 10 days after peritoneal injection of AdCAtob compared with the control group. There were no tumor nodules in the abdomen and no bloody ascites. These results suggest that the peritoneal injection of AdCAtob has potential to suppress the formation of pancreatic cancer peritonitis, and can be applied for chemotherapy-resistant cancer peritonitis.     

Tumor angiogenesis and endothelial cell modulatory factors.

Angiogenesis is the ability of preexisting vasculature to send out capillary sprouts leading to the formation of new vasculature. It is now a well-accepted idea that progression of solid tumors is intrinsically dependent on angiogenesis for growth of the primary tumor and metastatic lesions. Investigations into tumor angiogenesis have focused on inhibition of tumor neovasculature as yet another possible mechanism for impairing tumor progression. Numerous studies have characterized cellular and molecular factors important to vascular formation and development and have led to the identification and understanding of requisite interactions between endothelium, angiogenic cytokines, and the supporting matrix. These studies have also led to the identification of cytokines involved in the proteolytic disruption of the basement membrane, the migration of endothelial cells, and the proliferation and formation of neoendothelium into functional vasculature. As therapies based on antiangiogenic strategies continue to evolve and clinical trials are conducted, these agents may become an important part of the arsenal against tumor proliferation, especially given their favorable toxicity profile. This review discusses the angiogenic cytokines which have been most intensely studied and the receptors they act upon. Additionally, we discuss select proteases and their importance in the development of neovasculature. A better understanding of these components will help in the development of novel therapeutic strategies.     

Tumor growth inhibition in vivo and G2/M cell cycle arrest induced by antisense oligodeoxynucleotide targeting thymidylate synthase.

Chemotherapeutic agents targeting thymidylate synthase (TS) are effective against human tumors. Efficacy is limited by drug resistance, often mediated by TS overexpression. Treatment of HeLa cells in vitro with an antisense oligodeoxynucleotide (ODN 83) targeting human TS mRNA reduces TS mRNA and protein levels, inhibits cell proliferation, and sensitizes cells to TS-targeting drugs (Ferguson et al., 1999). The present study investigates the mechanism by which ODN 83 inhibits cell proliferation and examines its antitumor efficacy in vivo. ODN 83 treatment did not induce apoptosis in HeLa cells in vitro but caused accumulation of cells at G2/M. In contrast, TS-targeting chemotherapeutics arrest at G1 or S. Antisense down-regulation reduced TS mRNA levels in human colon cancer (HT29) cells by 40% in vitro, resulted in G2/M arrest, and reduced proliferation without enhanced cell death. Growth of HT29 tumors in immunocompromised mice was significantly inhibited when antisense ODN 83 treatment began promptly after tumor implantation and was accompanied by a 40% reduction in TS protein levels. Growth of tumors allowed to reach 400 mm3 prior to ODN administration was unaffected by antisense ODN 83. Radiolabeled ODNs were localized to the tumor periphery but evenly distributed in normal tissue. Thus, down-regulation of TS mRNA and protein by antisense ODN treatment exerts a novel G2/M cell cycle block without increasing cell death and inhibits HT29 tumor cell growth in vivo. Antisense ODN 83 may be an effective therapy for colon carcinoma, alone or in combination with TS-targeting cytotoxic drugs.     

Tumor promoter phorbol myristic acetate stimulates immunoglobulin secretion correlated with growth cessation in human B lymphocyte cell lines.

Immunoglobulin production by lymphoblast cell lines was studies using protein A-red blood cell plaque formation to detect individual secreting cells. Immunoglobulin (Ig) secretion by 6 of 12 human B-cell lines tested could be stimulated up to twentyfold by phorbol myristic acetate (PMA) at subtoxic concentrations of 10-1000 ng/ml depending on the line. Stimulation was found with both IgM and IgG cell lines. No switch of Ig class synthesis was found in the cell lines as a result of PMA incubation. Increase in Ig secretion was closely associated with cessation of growth resembling induction of terminal differentiation in the cells. PMA induction of Ig secretion in B lymphocytes from normal peripheral blood requires the cooperation of T cells. PMA stimulation of certain cell lines reported here suggests that the lines are late in the differentiation pathway to plasmacyte and can be easily triggered to secrete Ig by membrane-altering agents.     

Tumor invasion front in oral squamous cell carcinoma

Oral squamous cell carcinoma is a neoplasm that originates from the epithelial mucosa. It is usually more frequent between the fifth and sixth decades of life, and more than 90% of carcinomas of the oral cavity are squamous cell carcinoma. It is an invasive neoplasia with a significant recurrence rate; 40% of patients present with metastases in the cervical lymph nodes at the time of diagnosis. The tumor invasion front is a characteristic of tumor growth, which can be infiltrative or noninvasive. The histopathological parameters examined include the number of mitoses, depth of the tumor, invasion pattern, degree of keratinization, and nuclear pleomorphism. For the pathologist, these parameters are routinely evaluated but are not reported to the treating physician in all cases, which we consider to be useful information when determining the therapeutic route.     

Autologous stem cell transplantation and stem cell mobilization kinetics in elderly patients with B cell non-Hodgkin lymphoma

As known, the world population is aging and as the life span increases the number of advanced-age lymphomas also shows an upward trend. Autologous hematopoietic stem cell transplantation (HSCT) is the standard treatment modality in chemotherapy-sensitive relapsed or refractory aggressive lymphomas. Increased morbidity and mortality related to both the transplant itself and comorbid diseases can be observed in elderly lymphoma patients. Patients who are 65 years or older and underwent autologous HSCT with B-cell non-Hodgkin lymphoma were retrospectively included in our study. In terms of survival analysis, median follow-up was 34.5 months (8–159) while the overall survival (OS) was 58%. In the univariate analysis of prognostic data in OS, patients who were referred to transplantation with complete response had a statistically significant survival advantage (p = 0.043). In terms of the effect of pre-transplant conditioning regimens on survival, BEAM regimen yielded better results, though not statistically significant. Age, number of chemotherapy cycles received before mobilization and radiation therapy had no significant effect on the CD34 (+) cell count in the final product (p = 0.492, 0.746 and 0.078 respectively). In conclusion, autologous HSCT is a practicable treatment modality that provides survival advantage in suitable advanced-age patients with a diagnosis of B-cell non-Hodgkin lymphoma.     

Tumor growth models to generate pathologies for surgical training simulators

Many virtual reality based surgical training simulators have been presented in the last few years. These systems promise to alleviate the lack of realistic training possibilities common to minimally invasive procedures. Virtual reality allows for riskless training on a wide range of findings in a condensed period of time. We investigated different methods for the generation of tumor models suitable for surgical training simulators. The goal of our research is a high fidelity hysteroscopy simulator which provides an individual surgical scene for every training. Emphasis was placed on the modeling of growth processes leading to the generation of macroscopically realistic findings of the most common pathologies in hysteroscopy, namely polyps and myomas found in the uterine cavity. Both a cellular automaton and a particle based tumor growth model are presented and discussed.     

Tumor rejection by disturbing tumor stroma cell interactions.

The stroma of solid tumors is a complex network of different cell types. We analyzed stroma cell interactions in two tumor models during cyclophosphamide (Cy)-induced tumor rejection. In growing tumors, tumor infiltrating macrophages (TIMs) produced interleukin (IL)-10. Beginning 6 h after Cy-treatment T cells in the tumor were inactivated and TIMs switched to interferon (IFN)-gamma production. Both, IL-10 production before and IFN-gamma production after Cy-treatment by TIMs required T cells. With the same kinetics as TIMs started to produce IFN-gamma the tumor vasculature was destroyed which required IFN-gamma receptor expression on host but not tumor cells. These events preceded hemorrhagic necrosis and residual tumor cell elimination by T cells. Together, T cells regulate the function of TIMs and tumor rejection can be induced by disturbing the stroma network.     

Unusual kinetics of white cell clearance in transfused mice

BACKGROUND: Donor white cells (WBCs) in blood transfusions are responsible for complications in recipients, including alloimmunization, graft-versus-host disease (GVHD), and virus transmission and reactivation. The recent use of sequence-specific polymerase chain reaction assays to monitor the kinetics of clearance of donor WBCs in transfused humans and dogs found transient recirculation of donor lymphocytes on Days 3 to 5 after transfusion; this presumably reflected an abortive GVHD reaction to major histocompatibility complex-incompatible recipient cells, after which donor WBCs were cleared to undetectable levels. STUDY DESIGN AND METHODS: This study sought to develop a murine model to further characterize the kinetics and major histocompatibility complex restriction of donor WBC clearance. A sensitive murine Y chromosome- specific polymerase chain reaction assay was developed and applied to serial blood samples collected after transfusions of allogeneic blood to naive inbred, primed inbred, and outbred mice, as well as after transfusions of gamma-radiated blood to naive inbred mice. RESULTS: In inbred mice, both naive and primed to the allogeneic blood donor, transfused WBCs were not cleared to undetectable levels for more than 1 month after transfusion. Transfused outbred mice also showed prolonged donor WBC survival, although at lower levels than inbred mice. There was no evidence of GVHD in either inbred or outbred mice, and gamma radiation had no significant impact on donor WBC persistence. CONCLUSION: These results contrast with the rapid clearance of donor WBCs observed in humans and dogs. The immunologic basis for this discrepancy remains unclear. Caution should be exercised in any extrapolation to humans of conclusions drawn from results in transfused mice.     

Tumor necrosis factor alpha is involved in mouse growth and lymphoid tissue development

Tumor necrosis factor alpha (TNF-alpha), a major mediator of inflammation, also possesses a wide pleiotropism of actions, suggesting its involvement in physiological conditions. TNF-alpha mRNA is present in mouse embryonic tissues and also in fetal thymus and spleen. Repeated injections of a monospecific polyclonal rabbit anti-mouse TNF-alpha antibody in mice, starting either during pregnancy or at birth, led to a severe but transient growth retardation, already present at birth, reaching a 35% decrease in body weight at 3 wk, with complete recovery at 8 wk. The insulin growth factor I (IGF-I) blood levels were decreased to about 50%; growth hormone release and other endocrine functions were unaltered. A marked atrophy of the thymus, spleen, and lymph nodes was also observed, with lymphopenia and impaired development of T and B cell peripheral lymphoid structures. The pathways involving TNF-alpha in IGF-I release and early body growth are probably distinct from those by which TNF-alpha participates in early development of lymphoid tissues, where its low physiological release may contribute to enhance lymphoid cell expansion.     

Tumor growth reduction and DNA transfer by cavitation-enhanced high-intensity focused ultrasound in vivo

The potential application of high-intensity focused ultrasound (US), HIFU, was investigated for nonthermal gene transfer and tumor ablation. Renal carcinoma (RENCA) tumors were implanted on the hind leg of BALB/c mice and injected with a marker plasmid. Optison US contrast agent was also injected into the tumor (IT) or into the venous (IV) circulation. HIFU at 1.55 MHz was applied to the tumors with guidance from diagnostic US images. One test of transfection was also performed with lithotripter shock waves. In one set of exposures, tumor volume was followed for 4 days and a beta-galactosidase marker plasmid was used for localization of transfected cells. A second set of exposures employed a luciferase marker plasmid for assessing overall transfection after 2 days. Use of 100-ms bursts at 8-MPa peak rarefactional pressure amplitude stopped tumor growth during the 4-day period, compared to a 2.8-fold growth in shams and yielded luciferase expression 34-fold greater than in shams. Longer bursts or higher pressure amplitudes led to decreases in tumor growth, but did not yield increases in transfection. The HIFU results were similar to those of shock waves for cavitation enhanced by IT Optison. These results should aid in optimizing the application of HIFU for nonthermal tumor treatment.