Major Histocompatibilty Complex-Restricted Adaptive Immune Responses to CT26 Colon Cancer Cell Line in Mixed Allogeneic Chimera

BACKGROUND

Although the induction of mixed allogeneic chimera shows promising clinical tolerance results in organ transplantation, its clinical relevance as an anti-cancer therapy is yet unknown. We introduced a mixed allogenic chimera setting with the use of a murine colon cancer cell line, CT26, by performing double bone marrow transplantation.

METHODS

We analyzed donor- and recipient-restricted anti-cancer T-cell responses, and phenotypes of subpopulations of T cells. The protocol involves challenging 1 × 10⁵ cells of CT26 cells intra-hepatically on day 50 after bone marrow transplantation, and, by use of CT26 lysates and an H-2L^d-restricted AH1 pentamer, flow cytometric analysis was performed to detect the generation of cancer-specific CD4⁺ and CD8⁺ T cells at various time points.

RESULTS

We found that immunocompetence against tumors depends heavily on cancer-specific CD8⁺ T-cell responses in a major histocompatibility complex-restricted manner; the evidence was further supported by the increase of interferon-γ-secreting CD4⁺ T cells. Moreover, we demonstrated that during the effector immune response to CT26 cancer challenge, there was a presence of central memory cells (CD62L^hiCCR7⁺) as well as effector memory cells (CD62L^loCCR7^-). Moreover, mixed allogeneic chimeras (BALB/c to C56BL/6 or vice versa) showed similar or heightened immune responses to CT26 cells compared with that of wild-type mice.

CONCLUSIONS

Our results suggest that the responses of primary immunocompetency and of pre-existing memory T cells against allogeneic cancer are sustained and preserved long-term in a mixed allogeneic chimeric environment.

Enhanced Controlled Transdermal Delivery of Ambroxol from the EVA Matrix

To avoid the systemic adverse effects that might occur after oral administration, transdermal delivery of ambroxol was studied as a method for maintaining proper blood levels for an extended period. Release of ambroxol according to concentration and temperature was determined, and permeation of drug through rat skin was studied using two chamber-diffusion cells. The solubility according to PEG 400 volume fraction was highest at 40% PEG 400. The rate of drug release from the EVA matrix increased with increased temperature and drug loading doses. A linear relationship existed between the release rate and the square root of loading rate. The activation energy (Ea) was measured from the slope of the plot of log P versus 1000/T and was found to be 10.71, 10.39, 10.33 and 9.87 kcal/mol for 2, 3, 4 and 5% loading dose from the EVA matrix, respectively. To increase the permeation rate of ambroxol across rat skin from the EVA matrix, various penetration enhancers such as fatty acids (saturated, unsaturated), propylene glycols, glycerides, pyrrolidones, and non-ionic surfactants were used. The enhancing effects of the incorporated enhancers on the skin permeation of ambroxol were evaluated using Franz diffusion cells fitted with intact excised rat skin at 37° using 40% PEG 400 solution as a receptor medium. Among the enhancers used, polyoxyethylene-2-oleyl ether increased the permeation rate by 4.25-fold. In conclusion, EVA matrix containing plasticizer and permeation enhancer could be developed for enhanced transdermal delivery of ambroxol.

Glioblastoma cell death induced by asiatic acid

Asiatic acid (AA), a triterpene, is known to be cytotoxic to several tumor cell lines. AA induces dose- and time-dependent cell death in U-87 MG human glioblastoma. This cell death occurs via both apoptosis and necrosis. The effect of AA may be cell type-specific as AA-induced cell death was mainly apoptotic in colon cancer RKO cells. AA-induced glioblastoma cell death is associated with decreased mitochondrial membrane potential, activation of caspase-9 and -3, and increased intracellular free Ca2+. Although treatment of glioblastoma cells with the caspase inhibitor zVAD-fmk completely abolished AA-induced caspase activation, it did not significantly block AA-induced cell death. AA-induced cell death was significantly prevented by an intracellular Ca2+ inhibitor, BAPTA/AM. Taken together, these results indicate that AA induces cell death by both apoptosis and necrosis, with Ca2+-mediated necrotic cell death predominating.

Ultrasound-Induced hyperthermia increases cellular uptake and cytotoxicity of P-glycoprotein substrates in multi-drug resistant cells

PURPOSE

Localized hyperthermia has been shown previously to augment the cytotoxicity of some lipophilic anticancer drugs. Because many of the substrates for the multi-drug resistance (MDR) transporter P-glycoprotein (P-gp) are lipophilic in nature, studies were conducted to test the hypothesis that hyperthermia induced by ultrasound could also increase cellular uptake and cytotoxicity of P-gp substrates by P-gp-expressing cells.

METHODS

To test this hypothesis, we studied the effects of hyperthermia and ultrasound on cellular accumulation of putative P-gp substrates, rhodamine 123 (R123) and doxorubicin (DOX), and cytotoxicity of DOX in the parent and MDR variants of two human cancer cell lines.

RESULTS

Treatment of cells with hyperthermia or ultrasound (20 min at 41 degrees C) both caused a significant increase over controls (no ultrasound treatment) in R123 and DOX accumulation in the parent and MDR lines of MV522 and KB cells. Ultrasound also substantially increased the antiproliferative effects of DOX in both the parent and MDR variants of MV522 and KB cell lines when compared with controls. Our results also indicated that ultrasound exerted a much greater effect on cellular accumulation of R123 and DOX and cytotoxicity enhancement of DOX in the MDR variants than putative P-gp antagonist such as verapamil.

CONCLUSION

The present results point to the potential use of ultrasound-induced hyperthermia as a much safer alternative to P-gp antagonist for reversal of MDR.

Down modulation of IL-18 expression by human papillomavirus type 16 E6 oncogene via binding to IL-18

To understand modulation of a novel immune-related cytokine, interleukin-18, by human papillomavirus type (HPV) 16 oncogenes, HaCaT, normal keratinocyte cell line, and C-33A, HPV-negative cervical cancer cell line, were prepared to establish stable cell lines expressing E6, E6 mutant (E6m), E6E7, or E7 constitutively. Expressions of various HPV oncogene transcripts were identified by RT-PCR. Expression of HPV oncogene E6 was reversely correlated to the expression of interleukin-18, a novel pro-inflammatory cytokine. The expression of E6 in C-33A, independent of E6 splicing, resulted in decreased IL-18 expression and that of IL-18 was also significantly reduced in HaCaT cells expressing E6. The level of p53 was reduced in C-33A cells expressing E6 whereas not altered in HaCaT cells expressing E6, suggesting that E6 downregulated IL-18 expression via an independent pathway of p53 degradation in HaCaT cells which have a mutated p53 form. However, E7 did not affect IL-18 expression significantly in both C-33A and HaCaT cells. Cotransfection experiments showed that E6 oncogene did not inhibit the activities of IL-18 promoter P1 and P2, suggesting that E6 oncogene indirectly inhibited IL-18 expression. Taken together, E6, E6m and E6/E7 inhibited IL-18 expression with some variation, assuming that cells expressing E6 oncogene can evade immune surveillance by downregulating the expression of immune stimulating cytokine gene, IL-18, and inhibiting the cascade of downstream effects that follow activation of the IL-18 receptor.

Effects of non-ionic surfactants as permeation enhancers towards piroxicam from the poloxamer gel through rat skins

The enhancing effects of non-ionic surfactants on the permeation of piroxicam from the poloxamer gels were evaluated using Franz diffusion cells fitted with excised rat skins. The effectiveness of penetration enhancers, the ratio of piroxicam flux in the presence or absence of enhancers, was defined as the enhancement factor. Among the various non-ionic surfactants tested, polyoxyethylene-2-oleyl ether showed the highest enhancing effects with an enhancement factor of 2.84. To elucidate the mechanisms of the action of enhancers, thermal analysis and histological examinations were carried out. Thermal analysis reveals that various surfactants have different fluidizing effects on stratum corneum. Skin pretreated with the poloxamer 407 gels containing various surfactants showed a loosely layered stratum corneum and wide intercellular space.

A polymer-supported proline-based diamine catalyst for the kinetic resolution of racemic secondary alcohols

The preparation of polymer-supported proline-based diamine catalyst 12 for the kinetic resolution of racemic mixtures of secondary alcohols is described. Not only is the catalyst effective for the resolution of a host of different alcohols, it can also be recovered and reused several times without loss of either activity or selectivity. The catalyst has been used in conjunction with a polymer-supported sequestration strategy, giving rise to an essentially pure mixture of resolved products that can be separated using flash chromatography.

Improvement of gene transfer to cervical cancer cell lines using non-viral agents

Virus-like particles (VLPs) composed of recombinant capsid protein L1 and L2 of human papillomavirus type 16 were conjugated with polylysine (PL) and gene transfer was performed using VLP-PL conjugates to allow the expression of targeted gene. When HeLa cells were incubated with VLP-PL conjugate coupled with plasmid cytomegalovirus beta-galactosidase (pCMVbeta-gal), about 10% of cells were transfected and demonstrated beta-galactosidase activity. Hence chloramphenicol acetyltransferase activity was also expressed significantly in VLP-PL-plasmid simian virus 2 chloramphenicol acetyl transferase (pSV2CAT)-transfected cells, VLP-PL conjugate was tested whether it could transfer a tumor suppressor gene, pCMVp53, to HeLa cells and the exogenously provided p53 gene complexed to VLP-PL conjugate was detected from HeLa cells by polymerase chain reaction (PCR) analysis. Interestingly, additional increase of transfection efficiency was demonstrated in the presence of poloxamer 407 when C-33A cells were transfected with VLP-PL-pCMVbeta-gal complex. The result support the notion that VLP-PL conjugate may be a promising vector to transfer genetic materials into cancer cells and poloxamer 407 can be used for enhancing the transfection efficiency of VLP-PL conjugate.

Carrier-mediated uptake of rhodamine 123: implications on its use for MDR research

We have examined the effects of verapamil and PSC 833 on cellular uptake and release of rhodamine 123 (R123) in two human cancer cell lines. Both verapamil and PSC 833 were able to increase R123 accumulation in the multidrug resistant (MDR) MV522/Q6 and KB-8-5 lines in the release study. However, the effects of these drugs on R123 accumulation during accumulation study were quite different. Incubation with PSC 833 increased R123 accumulation in both MDR lines. By contrast, incubation with verapamil only increased R123 accumulation in the KB-8-5 line. The failure of verapamil to increase R123 accumulation in the MV522/Q6 cells can be attributed to the presence of a carrier system in the parent MV522 cells that recognizes both R123 and verapamil, but not PSC 833, as substrates. These results imply that performing R123 accumulation study without first ascertaining possible role of a carrier system for cellular uptake of R123 and putative P-gp modulators might inadvertently lead one to draw improper conclusions on P-gp activity.

Improvement of receptor-mediated gene delivery to HepG2 cells using an amphiphilic gelling agent

Gene transfer was performed using asialo-oroso-mucoid-polylysine (ASOR-PL) conjugates to allow targeted expression of the gene in cells of hepatic origin. In a gel-electrophoretic analysis, the ASOR-PL conjugate produced a complete DNA retardation effect at the optimal ratio of 222:1 (ASOR-PL conjugate/pCMV beta-gal plasmid). The gene-transfer efficiency of the ASOR-PL conjugate was evaluated in HepG2 cells that express asialoglycoprotein receptor and NIH 3T3 cells that do not. The expression was assayed by 5-bromo-4-chloroindol-3-yl beta-D-galactopyranoside ('X-Gal') staining and Chlorophenol Red beta-D-galactopyranoside. When an expression vector for the tumour-suppressor gene p53, pCMVp53, complexed to ASOR-PL conjugate, was transfected into HepG2 cells, the exogenously provided p53 gene was detected in the HepG2 cells by PCR. To improve the efficiency of DNA delivery and expression of the therapeutic proteins poloxamer 407, a fusogenic peptide, influenza-virus haemagglutinin HA2 and chloroquine were individually incorporated into the system. The expression level of beta-galactosidase in HepG2 cells was increased by about four times by the presence of poloxamer 407, whereas the fusogenic peptide HA2 and chloroquine had no effects. When HepG2 cells were transfected with pCMVp53 in the presence of poloxamer 407, the mRNA of transfected p53 could be detected by reverse transcriptase PCR. The current findings open the possibility that a receptor-mediated gene-delivery system for hepatic gene therapy using ASOR-PL conjugate in combination with poloxamer 407 may be developed in the future.

Enhancing effects of fatty acids on piroxicam permeation through rat skins

To increase the skin permeation of piroxicam from the Poloxamer 407 gel, fatty acid was added as a penetration enhancer to the Poloxamer 407 gel containing 1% piroxicam. The enhancing effects of the enhancer on the skin permeation of piroxicam were evaluated using Franz diffusion cells fitted with intact excised rat skins. To elucidate the modes of the action of enhancers, thermal analysis and histological examinations were conducted. Among fatty acids tested, linoleic acid showed the highest enhancing effects, with an enhancement factor (EF) of 1.76. From the thermal analysis results, fatty acids have fluidizing effects on the stratum corneum. The skin pretreated with the Poloxamer 407 gels containing piroxicam including linoleic acid showed a loosely layered stratum corneum and wide intercellular space.

Permeation of piroxicam from the poloxamer gels

Topical formulations of piroxicam were prepared using poloxamer 407 or poloxamer 188 by a cold method, and the permeation characteristics of piroxicam were evaluated. The permeation rate of piroxicam across the synthetic cellulose membrane and the rat skin decreased as the concentration of poloxamer increased. Though poloxamer gel exhibits reversed thermal behavior, the permeation rate of piroxicam increased with increasing temperature, indicating that the diffusional pathway of piroxicam is a water channel within the gel formulation. The pH of the gel did not affect the permeation rate of piroxicam significantly. As the concentration of piroxicam in the gel formulation increased, the permeation rate of piroxicam increased up to 1% and reached a plateau above 1%. Among various enhancers tested, polyoxyethylene-2-oleyl ether showed the highest enhancing effect, with an enhancement ratio of 2.84. Based on experimental results, the permeation rate of piroxicam can be controlled by changing the poloxamer concentration or drug concentration and by the addition of an appropriate enhancer.

Physicochemical characterizations of piroxicam-poloxamer solid dispersion

To develop an efficient topical delivery system for piroxicam using poloxamer gel formulation, physicochemical behavior of piroxicam in poloxamer was studied. The gelling property of poloxamer and the solubility of piroxicam in the poloxamer were investigated. The interaction between piroxicam and poloxamer was studied by x-ray diffractometry (XRD), infrared (IR) spectroscopy and differential thermal analysis (DTA) with a solid dispersion, coprecipitate, or physical mixture. Poloxamer 407 solutions showed the property of a gel when the concentration was higher than 15% (w/w) and poloxamer 407 increased the aqueous solubility of piroxicam by about 11-fold at the concentration of 22.5% (w/w). The results of XRD did not show the crystalline from of piroxicam in the solid dispersion and results of IR spectroscopic analysis showed an association between functional groups of piroxicam and poloxamer.