1α, 25 Dihydroxyvitamin D (1,25(OH)2D) inhibits the T cell suppressive function of myeloid derived suppressor cells (MDSC).

Myeloid derived suppressor cells (MDSC) suppress the ability of cytotoxic T cells to attack and clear tumor cells from the body. The active form of vitamin D, 1,25 dihydroxyvitamin D (1,25(OH)2D), regulates myeloid cell biology and previous research showed that in mouse models 1,25(OH)2D reduced the tumor level of CD34+ cells, an MDSC precursor, and reduced metastasis. We tested whether MDSC are vitamin D target cells by examining granulocytic- (G-MDSC) and monocytic (M-MDSC) MDSC from tumors, spleen, and bone marrow. Vitamin D receptor (VDR) mRNA levels are low in MDSC from bone marrow and spleen but are 20-fold higher in tumor MDSC. At all sites, M-MDSC have 4-fold higher VDR mRNA expression than G-MDSC. Bone marrow MDSC were induced to differentiate in vitro into tumor MDSC-like cells by treating with IFN-γ, IL-13, and GM-CSF for 48 h. This treatment significantly elevated Arg1 and Nos2 levels, activated the T cell-suppressive function of MDSC, increased VDR expression 50-fold, and made the MDSC responsive to 1,25(OH)2D treatment. Importantly, 1,25(OH)2D treatment reduced the T cell suppressive capacity of cytokine-induced total MDSC and M-MDSC by ≥70 % and tumor-derived M-MDSC by 30-50 %. Consistent with this finding, VDR deletion (KO) increased T cell suppressive function of in vitro M-MDSC by 30 % and of tumor-derived M-MDSC by 50 % and G-MDSC by 400 %. VDR KO did not alter Nos2 mRNA levels but significantly increased Arg1 mRNA levels in tumor M-MDSC by 100 %. In contrast, 1,25(OH)2D treatment reduced nitric oxide production in both in vitro derived M- and G- MDSC. The major finding of this study is that 1,25(OH)2D signaling through the VDR decreases the immunosuppressive capability of MDSC. Collectively, our data suggest that activation of vitamin D signaling could be used to suppress MDSC function and release a constraint on T-cell mediated clearance of tumor cells.

Fibronectin-mediated Calmette-Guerin bacillus attachment to murine bladder mucosa. Requirement for the expression of an antitumor response.

Adjuvant intravesical Calmette-Guerin bacillus (BCG) is an effective treatment for superficial bladder cancer. The mechanisms by which BCG mediates antitumor activity are not known. We investigated the initial interaction of BCG with the bladder mucosa to determine whether binding was essential for the development of antitumor activity. Herein, we show that bladder urothelial disruption induced by acrolein, adriamycin, or electrocautery resulted in BCG binding in areas of urothelial damage. Binding induced by each method was inhibited by anti-fibronectin (FN) antibodies but not by antibodies to the basement membrane component laminin. Intravesical BCG binding also was inhibited by pretreating BCG with soluble FN. Inhibition of intravesical FN-mediated BCG attachment prevented immunization via the intravesical route. Moreover, the expression of both delayed hypersensitivity in the bladder of BCG-immunized mice and antitumor activity was inhibited by blocking FN-mediated intravesical BCG attachment. These data suggest that intralumenal attachment of BCG appears to be mediated by FN. Moreover, these data suggest that intravesical FN mediated attachment of BCG is a requisite step in BCG-mediated antitumor activity in the murine bladder tumor model.

Characterization of the internalization of bacillus Calmette-Guerin by human bladder tumor cells.

Adjuvant intravesical Mycobacterium bovis BCG is the treatment of choice for recurrent superficial bladder cancer. Fibronectin (FN) was previously demonstrated to be necessary for the retention of BCG within the bladder and for the expression of antitumor activity. Recent studies have demonstrated that BCG attach and are ingested by bladder epithelial cells, suggesting the existence of a second bacterial attachment mechanism. We report the characterization of the molecules involved in BCG attachment and internalization by the human bladder transitional cell carcinoma cell line T-24. Pretreatment of T-24 cells with monoclonal antibodies to either alpha 5 or beta 1 integrin subunits significantly inhibited both BCG attachment and ingestion. Exogenous FN was observed to enhance both attachment and ingestion of BCG, and anti-FN was observed to inhibit both phenomena. Latex beads precoated with either FN or laminin (LN) but not BSA were ingested by T-24 cells, but only FN-coated beads inhibited BCG attachment and ingestion. Pretreatment of BCG with FN augmented both attachment and ingestion. The role of bacterial FN binding proteins was evaluated. A monoclonal antibody to a 55-kD FN-binding protein was observed to abrogate attachment and ingestion. These results demonstrate that attachment and ingestion of BCG are mediated in part by the alpha 5 beta 1 integrin receptor and are dependent on FN. These studies demonstrate a mechanism of entrance of mycobacteria into epithelial cells and suggest a second role for FN in the adjuvant antitumor effect of BCG.

Protein arginine methyltransferase 5 functions as an epigenetic activator of the androgen receptor to promote prostate cancer cell growth.

Protein arginine methyltransferase 5 (PRMT5) is an emerging epigenetic enzyme that mainly represses transcription of target genes via symmetric dimethylation of arginine residues on histones H4R3, H3R8 and H2AR3. Accumulating evidence suggests that PRMT5 may function as an oncogene to drive cancer cell growth by epigenetic inactivation of several tumor suppressors. Here, we provide evidence that PRMT5 promotes prostate cancer cell growth by epigenetically activating transcription of the androgen receptor (AR) in prostate cancer cells. Knockdown of PRMT5 or inhibition of PRMT5 by a specific inhibitor reduces the expression of AR and suppresses the growth of multiple AR-positive, but not AR-negative, prostate cancer cells. Significantly, knockdown of PRMT5 in AR-positive LNCaP cells completely suppresses the growth of xenograft tumors in mice. Molecular analysis reveals that PRMT5 binds to the proximal promoter region of the AR gene and contributes mainly to the enriched symmetric dimethylation of H4R3 in the same region. Mechanistically, PRMT5 is recruited to the AR promoter by its interaction with Sp1, the major transcription factor responsible for AR transcription, and forms a complex with Brg1, an ATP-dependent chromatin remodeler, on the proximal promoter region of the AR gene. Furthermore, PRMT5 expression in prostate cancer tissues is significantly higher than that in benign prostatic hyperplasia tissues, and PRMT5 expression correlates positively with AR expression at both the protein and mRNA levels. Taken together, our results identify PRMT5 as a novel epigenetic activator of AR in prostate cancer. Given that inhibiting AR transcriptional activity or androgen synthesis remains the major mechanism of action for most existing anti-androgen agents, our findings also raise an interesting possibility that targeting PRMT5 may represent a novel approach for prostate cancer treatment by eliminating AR expression.

Concanavalin A-activated suppressor cell activity in peripheral blood lymphocytes of urologic cancer patients.

Concanavalin A (Con A)-inducible suppressor cell activity in peripheral blood lymphocytes (PBL) of urologic cancer patients and of appropriate controls with benign urologic disorders was measured concurrently. Although the proliferative responses to Con A of the cancer patients were significantly lower than those of controls, no difference in Con A-induced suppressor cell activity was demonstrated between cancer patients and controls when tested under a variety of conditions. Moreover, regression analysis revealed no correlation between the proliferative response to Con A and suppressor cell activity in either cancer patients or controls. The results indicated that Con A-inducible suppressor cell activity was unaltered in urologic cancer patients and suggested that suppressor cells of the type that can be activated by Con A were not involved in the general immunologic impairment frequently associated with urologic cancer.

Viral vector delivery in solid-state vehicles: gene expression in a murine prostate cancer model.

BACKGROUND: Although there are increasingly more clinical trials involving gene therapy, efficient gene transfer remains a major hurdle to success. To enhance the efficiency of delivery of viral vectors in gene therapy protocols, we evaluated the effect of various matrices to act as a vehicle for recombinant virus during intratumoral injection. METHODS: The ability of several vehicles (catgut spacer, polyglycolic acid, chromic catgut, and gelatin sponge matrix) to deliver the canarypox virus ALVAC to the cells of the murine prostate cancer cell line RM-1 was studied in vitro and in vivo. ALVAC recombinants encoding the murine cytokines interleukin 2 (IL-2), interleukin 12 (IL-12), and tumor necrosis factor-alpha (TNF-alpha) were used to assess enhancement of antitumor activity after intratumoral inoculation. Confirmatory experiments were conducted by use of another mouse prostate cancer cell line, RM-11, and a mouse bladder cancer cell line, MB-49. All statistical tests were two-sided. RESULTS: The gelatin sponge matrix proved to be the most effective solid-state vehicle for delivering viral vectors to cells in culture. In addition, this matrix statistically significantly enhanced expression of ALVAC-delivered reporter genes in tumor models when compared with fluid-phase delivery of virus (P =.037 for the RM-1 model and P =.03 for the MB-49 model). Statistically significant growth inhibition of established tumors was observed when a combination of the three recombinant ALVAC viruses expressing IL-2, IL-12, and TNF-alpha was delivered with the matrix in comparison with 1) fluid-phase intratumoral injection of the ALVAC recombinants, 2) no treatment, or 3) treatment with parental ALVAC (all P<.05). CONCLUSIONS: Viral vector delivery in a solid-state vehicle resulted in improved recombinant gene expression in vivo and translated to greater inhibition of tumor growth in an immunotherapy protocol for heterotopic tumor nodules. The efficient delivery of reporter genes described herein may prove useful in many solid tumor gene therapy protocols.

Effect of canarypox virus (ALVAC)-mediated cytokine expression on murine prostate tumor growth.

BACKGROUND: Canarypox virus, ALVAC, does not replicate in infected mammalian cells and has potential as a vector for gene therapy in the treatment of cancer. PURPOSE: Recombinant viruses carrying DNA sequences encoding interleukin 2 (ALVAC-IL-2), interferon gamma (ALVAC-IFN gamma), tumor necrosis factor-alpha (ALVAC-TNF-alpha), or the co-stimulatory molecule B7-1 (ALVAC-B7-1) were investigated as agents for the treatment of a newly defined mouse prostate tumor model. METHODS: RM-1 mouse prostate cancer cells, which are syngeneic (i.e., same genetic background) to C57BL/6 mice, were used. The expression of foreign gene products in vitro in infected RM-1 cells was measured by immunoprecipitation, bioassay, or flow cytometry. The effects of foreign gene product expression on RM-1 tumor cell growth in C57BL/6 mice were measured after subcutaneous injection (in the back) of 5 x 10(5) uninfected or infected cells; measurements included determinations of time to a measurable tumor size, tumor size as a function of time, and survival. The induction of protective immunity by uninfected and infected RM-1 cells was tested by injection of lethally irradiated (70 Gy) cells and subsequent challenge with uninfected cells. The generation of cytotoxic T cells was monitored by use of a 51Cr release assay. Severe combined immunodeficient (SCID) mice were used to determine whether T or B lymphocytes were involved in ALVAC vector-mediated antitumor responses. Data were analyzed by use of Pearson's modification of the chi-squared test and Kaplan-Meier survival methods. Reported P values are two-sided. RESULTS: The level of foreign gene product expression in ALVAC-infected RM-1 cells was dependent on the multiplicity of virus infection used; a multiplicity of five viruses per infected cell was chosen for subsequent experiments. RM-1 tumor growth in C57BL/6 mice was not affected by tumor cell expression of IL-2 alone, IFN gamma alone, or B7-1 alone; however, expression of TNF-alpha alone significantly delayed tumor growth at early time points (compared with parental ALVAC-infected tumors, P = .0001 at day 21 and P = .037 at day 28). Tumor cell expression of both TNF-alpha and IL-2 completely inhibited tumor growth in 60%-100% of treated mice. No protection against subsequent tumor challenge was detected in mice previously exposed to RM-1 cells expressing both TNF-alpha and IL-2. Cytotoxic T-lymphocyte activity toward RM-1 cells was not observed in C57BL/6 mice that rejected tumors. Tumor cell expression of TNF-alpha and IL-2 also resulted in tumor growth inhibition in SCID mice. CONCLUSIONS: RM-1 mouse prostate cancer cells are readily infected by ALVAC vectors, and foreign gene products are efficiently expressed. Inhibition of RM-1 tumor growth by tumor cell expression of TNF-alpha and IL-2 appears to involve nonspecific antitumor activity.

Inhibition of murine prostate tumor growth and activation of immunoregulatory cells with recombinant canarypox viruses.

BACKGROUND: Immunization with modified tumor cells carrying recombinant immunomodulatory genes is being explored as cancer immunotherapy. In this study, we examine whether canarypox ALVAC viruses carrying immunostimulatory cytokine genes (granulocyte-macrophage colony-stimulating factor, interleukin 2, interleukin 12, and tumor necrosis factor-alpha) can induce antitumor immunity (to rechallenge) in the RM-1 model of a highly aggressive, weakly immunogenic murine prostate cancer. METHODS: For antitumor activity studies, RM-1 murine prostate cancer cells were infected with the parental ALVAC virus or one or two recombinant ALVAC-cytokine viruses and then injected into male C57BL/6 mice. For rechallenge studies, other mice were first given an injection subcutaneously with irradiated (nonproliferating) recombinant ALVAC-infected RM-1 cells and then (10 days later) with untreated RM-1 cells. For the determination of which immune cells were required for antitumor activity, mice were immunodepleted of CD4, CD8, or natural killer (NK) NK1.1 cells with the corresponding monoclonal antibodies and were then given an injection of ALVAC-cytokine-infected RM-1 cells. For all experiments, tumor outgrowth and animal survival were monitored. RESULTS: After subcutaneous injection into mice, RM-1 cells infected with one (except ALVAC-interleukin 2) or two ALVAC-cytokine recombinants had statistically significantly greater antitumor activity than RM-1 cells infected with parental ALVAC (P<.001 for all; two-sided test). The antitumor activity of RM-1 cells infected with any two ALVAC-cytokine recombinants was greater than, but not statistically significantly different from, that of RM-1 cells infected with any one ALVAC-cytokine recombinant. NK1.1 cells were necessary for antitumor activity, but tumor-specific CD4(+) regulatory T cells were also induced that inhibited CD8(+) RM-1-specific cytotoxic T cells, resulting in the lack of immunity to a rechallenge by RM-1 cells. DISCUSSION: Canarypox viruses can transfer immunostimulatory cytokine genes into RM-1 prostate cancer cells. When such cells were injected into mice, the cytokines induced an antitumor response against this highly aggressive, weakly immunogenic tumor. This response, however, did not protect the mouse against a rechallenge with RM-1 cells because suppressor CD4(+) T cells were induced that inhibited tumor-specific CD8(+) cytotoxic T cells.

Concanavalin A-inducible suppressor cells in regional lymph nodes of cancer patients.

Regional tumor-draining lymph nodes of 11 of 14 patients with urological tumors and one of four controls studied contained suppressor cell precursors that could be activated by concanavalin A (Con A) to suppress the proliferative response of autologous lymphocytes to Con A. In contrast, no suppression of lymphocyte proliferation by lymph node cells that were not activated with Con A was observed in four patients tested. The suppressive effect was not due to decreased viability or increased release of cold thymidine by Con A-activated cells nor to alteration in the time course of the proliferative response of Con A-activated cells. Mitomycin C treatment of lymph node cells 24 hr after activation did not abrogate their suppressive activity. Peak suppression was observed after 72 hr in culture. The amount of suppression measured could be maximized by treatment of suppressor cells with mitomycin C 24 hr after activation and by washing the cells immediately before pulse labeling with tritiated thymidine. The concentration of Con A required to produce peak suppression varied from patient to patient with optimal doses ranging from 5 to 25 microgram/ml.

Modulation of fibronectin-mediated Bacillus Calmette-Guérin attachment to murine bladder mucosa by drugs influencing the coagulation pathways.

Adjuvant intravesical Bacillus Calmette-Guérin (BCG) has proved to be an effective treatment for superficial bladder cancer. Intraluminal attachment of BCG organisms via binding to the extracellular matrix protein, fibronectin (FN), appears to be required for expression of the antitumor efficacy of BCG against a murine bladder tumor. Initial studies demonstrated that radiolabeled FN localized to the acutely injured urothelium but not to intact urothelium. These studies also demonstrated that exogenous administration of FN enhanced BCG attachment to the injured but not to the intact urothelium. Because FN has been shown to be an integral part of clot formation at sites of urothelial injury, drugs known to affect fibrin clot formation were tested for their effects on BCG attachment and antitumor efficacy in a murine bladder tumor model. A stabilizer of fibrin clot formation was shown to enhance both BCG attachment and antitumor efficacy in the same model. An increased number of BCG organisms were also retained in the lymph nodes and spleens of mice receiving fibrin clot stabilizers, suggesting indirectly that immunological mechanisms are involved in the antitumor efficacy of BCG. The data presented herein provide further support for the hypothesis that BCG attachment to the injured bladder is mediated by FN. Furthermore, modulation of BCG-FN attachment is demonstrated to be possible with drugs influencing the coagulation pathway. This attachment is shown to be required for the antitumor efficacy in a murine bladder tumor model, and thus modulation of BCG-FN attachment appears to have significant influence on the antitumor efficacy of BCG in the murine bladder tumor model.

Intravesical Bacillus Calmette-Guérin therapy for murine bladder tumors: initiation of the response by fibronectin-mediated attachment of Bacillus Calmette-Guérin.

Intravesical Bacillus Calmette-Guérin (BCG) is considered to be one of the most effective treatments for superficial bladder cancer. Although the mechanisms by which BCG inhibits tumor growth are not known, previous studies have shown that systemic immunization to BCG and the local expression of the immune response in the bladder are associated with a favorable response to BCG therapy. We have investigated the conditions required for the initiation of an immunological response after the intravesical instillation of BCG. Initial histological studies showed that BCG attached to the bladder wall only in areas where the urothelium was damaged by electrocautery and suggested that attachment was associated with the fibrin clot. Quantitative studies verified the histological observations. Minimal BCG attachment (mean less than 10(2) colony forming units) was observed in normal bladders in contrast with a mean of 1.42 X 10(4) colony forming units/bladder in bladders damaged by electrocautery (10 separate experiments). BCG attachment to the bladder wall was durable since organisms were observed in bladders 48 h after instillation. To investigate the proteins to which BCG attached, we tested the binding of BCG to extracellular matrix and inflammatory proteins which comprise a significant portion of the fibrin clot. BCG bound in vitro to coverslips coated in vivo with extracellular matrix proteins but did not bind to control albumin-coated coverslips. BCG also bound to coverslips coated with purified plasma fibronectin but not to coverslips coated with other purified extracellular matrix proteins including laminin, fibrinogen, and type IV collagen. BCG attachment to coverslips coated with either extracellular matrix proteins or purified fibronectin was inhibited by antibodies specific for fibronectin. Moreover, BCG attachment to cauterized bladders in vivo was inhibited by antifibronectin antibodies. These results demonstrate that fibronectin mediates the attachment of BCG to surfaces and suggest that it is the primary component mediating attachment within the bladder. Moreover, the data suggest that the BCG-fibronectin interaction may be a requisite first step for the initiation of the antitumor activity in intravesical BCG for bladder cancer.

Reduction of bladder tumor growth in mice treated with intravesical Bacillus Calmette-Guérin and its correlation with Bacillus Calmette-Guérin viability and natural killer cell activity.

The effect of intravesical Bacillus Calmette-Guérin (BCG; Pasteur strain) treatment on the frequency of implantation and growth rate of the murine transitional cell carcinoma of the bladder, MBT-2, was studied. MBT-2 cells were instilled into the bladder immediately after electrocauterization, and BCG instillations (40, 80, and 160 micrograms/instillation) were initiated 24 hr later and continued on a weekly basis for 4 weeks. BCG treatment significantly (p less than 0.0002) reduced the incidence of tumor implantation in a dose-dependent manner and resulted in significantly (p less than 0.0001) smaller tumors when they appeared in BCG-treated mice. The therapeutic effect of BCG correlated with augmentation of natural killer cell (NK) activity and positive purified protein derivative (PPD) footpad reactions. In experiments in which treatment was initiated with rapidly growing BCG organisms (10(7) colony-forming units/mg), tumor implantation was inhibited, there was a dose-dependent increase in NK activity, and mice had positive footpad reactions in PPD. In experiments in which BCG with reduced viability (10(6) colony-forming units/mg) and slower growth rates was used for treatment, no significant inhibition of tumor implantation was observed, NK activity was depressed, and PPD footpad tests were uniformly negative. The results suggest that the therapeutic effects of BCG therapy in this murine model correlate with augmentation of NK activity and positive footpad reactions to PPD and further suggest that the viability and growth rate of BCG organisms are important factors in determining the efficacy of intravesical BCG therapy.

Heightened interferon-gamma production by mononuclear cells from bladder cancer patients.

Interferon-gamma (IFN-gamma) production by peripheral blood leukocytes from bladder cancer patients was compared with that of patients with prostate cancer and benign prostatic hyperplasia, nontumor-bearing patients with bacterial infections, and normal controls. Leukocyte preparations including mononuclear cells isolated on a Ficoll-Hypaque density gradient (Fraction 2) and glass-nonadherent mononuclear cells (Fraction 3) were stimulated with Protein A from Staphylococcus aureus, and IFN-gamma production was monitored 24 hr later. The class of interferon produced was identified by antibody neutralization experiments which clearly showed S. aureus Protein A-induced interferon to be IFN-gamma. There was significantly heightened IFN-gamma production by Fraction 3 cells from bladder cancer patients and patients with bacterial infections. Heightened IFN-gamma production by bladder cancer patients was not observed in the Fraction 2 cells. No correlation was observed between IFN-gamma production and patients with invasive or noninvasive bladder cancer, but IFN-gamma production was lower in patients having Stage C or D tumors than in those having Stage A or B tumors. These results in conjunction with previous reports demonstrating heightened IFN-gamma production during periods of antigenic stimulation suggest that bladder tumors may induce a cell-mediated immune response in the host as evidenced by the elevation in IFN-gamma production. Moreover, the results suggest that macrophages may be important regulators of IFN-gamma production in bladder cancer patients.

Effects of alpha-difluoromethylornithine and recombinant interferon-alpha 2 on the growth of a human renal cell adenocarcinoma xenograft in nude mice.

The effects of human recombinant interferon-alpha 2 (IFN-alpha 2) and alpha-difluoromethylornithine (DFMO) as single agents and in combination were studied for efficacy against the renal cell adenocarcinoma (JDF-1) in an in vitro clonogenic assay and in vivo as xenografts in nude mice. In vitro studies showed dose-dependent inhibition of JDF-1 colony formation by IFN-alpha 2. DFMO alone did not significantly inhibit colony formation even though ornithine decarboxylase activity was significantly inhibited. The combination of IFN-alpha 2 and DFMO synergistically inhibited JDF-1 colony formation. The synergism was more readily observed at low IFN-alpha 2 concentrations. In vivo studies showed a similar tumor growth inhibition pattern. JDF-1 tumors were implanted s.c. in nude mice, and drugs were administered continuously by Alza minipumps (IFN-alpha 2) and in drinking water (DFMO) for 28 days. IFN-alpha 2 alone significantly inhibited JDF-1 growth, while DFMO alone had no significant inhibitory effect. The combination of IFN-alpha 2 and DFMO inhibited tumor growth in an apparent additive manner at the doses used. This was reflected in the mean tumor weights obtained at the termination of the experiment: control, 1484 +/- 187 (S.E.) mg; DFMO only, 1106 +/- 129 mg; IFN-alpha 2 only, 941 +/- 186 mg; and DFMO plus IFN-alpha 2, 620 +/- 109 mg. Assessment of mouse natural killer cell activity at the time of sacrifice showed that DFMO inhibited natural killer cell activity, while IFN-alpha 2 had no effect. DFMO was observed to inhibit ornithine decarboxylase activity in JDF-1 tumors by 78%, IFN-alpha 2 by 18%, and the combination by 78%. In addition, the drugs individually and in combination had similar inhibitory effects on JDF-1 spermidine content. One of the unexpected findings was the alteration in the spermine:spermidine ratio in the tumors treated with the combination of DFMO and IFN-alpha 2. The ratio in this group decreased to 0.44, while ratios for control, IFN-alpha 2 only, and DFMO only were 0.99, 0.66, and 0.88, respectively. These results clearly show that combined therapy with DFMO and IFN-alpha 2 is more effective than is single-drug therapy. The mechanism by which these drugs coordinately inhibit tumor growth is unclear but appears to be associated with direct inhibition of tumor cell proliferation, possibly by modulation of polyamine metabolism.

Technical factors affecting the reproducibility of intravesical mouse bladder tumor implantation during therapy with Bacillus Calmette-Guérin.

Four methods of intravesical implantation of the transplantable mouse bladder tumor, MBT-2, and their effects on intravesical therapy with Bacillus Calmette-Guérin (BCG) were compared, and modifications which improved implantation are described. Pretreatment of the bladder with N-methyl-N-nitrosourea (MNU) resulted in tumor implantation in approximately two-thirds of the animals; however, all tumors penetrated the bladder wall. Using the MNU implantation procedure, intravesical BCG therapy was shown to reduce MBT-2 outgrowth by 77%. Tumor cell instillation after electrocautery produced an incidence of tumor implantation similar to that of the MNU procedure. The efficacy of BCG for the electrocautery implantation procedure also was similar to the MNU method. With the electrocautery procedure, the electrode and tumor cells were introduced into the bladder via a catheter prepared from PE 10 polyethylene tubing. The procedure required two catheterizations and produced a 24% incidence of extravesical tumors. Use of a Teflon catheter and a single catheterization for tumor cell instillation resulted in a reproducible method for implanting MBT-2 tumors which were all confined within the bladder. The efficacy of BCG therapy was unchanged from that described for the other implantation techniques.

Comparison of the fibronectin-binding ability and antitumor efficacy of various mycobacteria.

Although the mechanism by which Bacillus Calmette-Guerin (BCG) exerts an antitumor effect on superficial bladder tumors is not fully understood, recent evidence has implicated binding of BCG organisms to fibronectin (FN) as requisite for this antitumor efficacy. Various substrains of BCG and other mycobacteria were tested in vitro for their relative capacities to bind both matrix and soluble FN. A substrain of Mycobacterium kansasii, designated the "high-binding strain," was found to bind FN more readily (P less than 0.05) in in vitro studies, when compared to commercially available substrains of BCG (Tice, Connaught, and Armand Frappier). The binding by the three commercial strains of BCG to FN in vitro appeared to be equivalent. The high-binding strain was further demonstrated to attach more readily in vivo to the acutely injured murine bladder (P less than 0.005) than the Armand Frappier substrain. Finally, using the MB49 murine bladder tumor model, an enhanced antitumor effect (P less than 0.05) was noted in mice treated with intravesical high-binding strain, in comparison to the Armand Frappier substrain, during five weekly treatments. It appears not only that the commercial substrains of BCG bind FN in an equivalent manner but also that the relative binding capacities of the substrains correlate directly with antitumor activity. A substrain of M. kansasii appears to have been identified which may prove more clinically effective than the currently available strains of BCG.

Inhibition of mouse bladder tumor proliferation by murine interferon-gamma and its synergism with interferon-beta.

We studied the effect of interferon-gamma (IFN-gamma) and mouse L-cell interferon (IFN-beta) on the proliferation of a mouse bladder tumor, MBT-2. A liquid culture clonogenic assay was used, and a linear relationship was obtained between the number of cells plated and the number of colonies formed. When the cells were assayed in the presence of various doses of murine IFN-gamma or IFN-beta, colony formation was inhibited in a dose-dependent manner. Partially purified IFN-gamma was more effective than IFN-beta in inhibiting MBT-2 colony formation in that IFN-beta exhibited a 50% inhibition dose of approximately 1000 units/ml, while the 50% inhibition dose for the partially purified IFN-gamma was approximately 70 units/ml. The 50% inhibition dose for recombinant IFN-gamma was 700 units/ml, suggesting that multiple lymphokines were active in the partially purified preparation. Further studies with partially purified IFN-gamma showed that the inhibitory effect was time dependent with the maximal effect observed after 48 hr of exposure in a 5-day assay. Treatment of partially purified IFN-gamma for 24 hr at pH 2.0 resulted in the abrogation of the antiproliferative effect. Studies in which partially purified IFN-gamma preparations were treated with a monoclonal antibody against IFN-gamma also resulted in abrogation of antiproliferative activity, confirming the nature of the antiproliferative agent to be IFN-gamma. Further studies showed that murine recombinant IFN-gamma also inhibited MBT-2 proliferation in a dose-dependent manner, confirming that IFN-gamma alone mediates antiproliferative activity. Combinations of IFN-beta and recombinant IFN-gamma acted synergistically in the inhibition of MBT-2 proliferation.

Abrogating cholesterol esterification suppresses growth and metastasis of pancreatic cancer.

Cancer cells are known to execute reprogramed metabolism of glucose, amino acids and lipids. Here, we report a significant role of cholesterol metabolism in cancer metastasis. By using label-free Raman spectromicroscopy, we found an aberrant accumulation of cholesteryl ester in human pancreatic cancer specimens and cell lines, mediated by acyl-CoA cholesterol acyltransferase-1 (ACAT-1) enzyme. Expression of ACAT-1 showed a correlation with poor patient survival. Abrogation of cholesterol esterification, either by an ACAT-1 inhibitor or by shRNA knockdown, significantly suppressed tumor growth and metastasis in an orthotopic mouse model of pancreatic cancer. Mechanically, ACAT-1 inhibition increased intracellular free cholesterol level, which was associated with elevated endoplasmic reticulum stress and caused apoptosis. Collectively, our results demonstrate a new strategy for treating metastatic pancreatic cancer by inhibiting cholesterol esterification.

Interaction of Mycobacterium tuberculosis with human respiratory mucosa.

OBJECTIVE: Endobronchial infection is associated with pulmonary tuberculosis in the majority of cases. We have investigated the adherence of Mycobacterium tuberculosis to the human respiratory mucosa. DESIGN: Organ cultures constructed with human tissue were infected with M. tuberculosis in the presence or absence of mycobacterial fibronectin attachment cell surface proteins and examined by scanning electron microscopy. RESULTS: M. tuberculosis adhered mainly to extracellular matrix (ECM) in areas of mucosal damage, but not to ciliated mucosa, intact extruded cells, basement membrane or collagen fibres. Bacteria also adhered to fibrous but not globular mucus and occasionally to healthy unciliated mucosa, open tight junctions and to extruded cells that had degenerated, exposing their contents. There was a significant reduction (p<0.05) in the number of bacteria adhering to ECM after pre-incubation of bacteria with fibronectin and after pre-incubation of the tissue with M. avium fibronectin attachment protein (FAP) and M. bovis antigen 85B protein, in a concentration dependent manner. The combined effect of FAP and antigen 85B protein was significantly greater than either protein alone. Bacterial adherence to fibrous mucus was not influenced by fibronectin. CONCLUSION: We conclude that M. tuberculosis adheres to ECM in areas of mucosal damage at least in part via FAP and antigen 85B protein.

Optimum conditions for the reproducible measurement of concanavalin A-activated suppressor cell activity.

The reproducibility of the measurement of concanavalin A (Con A)-inducible suppressor cell activity in human peripheral blood lymphocytes was examined. Suppressor cells were activated for 24, 48, or 72 hr with 3, 6, and 12 micrograms of Con A (Con A in concentrations greater than 12 micrograms/ml was toxic to the lymphocytes) per ml and suppression of the proliferative response of autologous lymphocytes to varying concentrations of Con A (3, 6, and 12 micrograms/ml) was measured. No single set of conditions consistently produced optimal suppression. Assays performed concurrently using lymphocytes from the same subject produced comparable suppressor cell activity; however, considerable variability in suppressor cell activity was observed under all conditions tested when five normal subjects were examined on as many as four separate occasions. The variability was reduced but not eliminated by reporting the data for each assay in terms of a peak suppression value determined from multiple sets of conditions. The results suggest that small differences in suppressor cell activity between patient groups may be masked by the intrinsic variability of the assay system.