Retardation of metastatic tumor growth after immunization with metastasis-specific monoclonal antibodies

The influence of 4 murine monoclonal antibodies (MAbs) directed against surface determinants of a metastasizing rat adenocarcinoma (BSp73ASML) on metastatic spread was evaluated and compared to their in vivo binding as well as to the induction of a humoral anti-MAb response, especially with respect to the development of anti-idiotypic (ID) antibodies of the internal image type. In a protocol of explicit immunization, all 4 MAbs transiently inhibited metastatic growth. Survival was prolonged only with one MAb (4.4ASML). With another MAb (1.1ASML), directed against a new variant form of CD44, metastatic growth was accelerated after transient retardation. Retardation of metastatic growth correlated with the humoral anti-MAb response. This accounted for the isotype- as well as for the idiotype-specific response. An exception was noted after immunization with MAb 1.1ASML. Rats with high levels of anti-1.1ASML antibodies, which inhibited binding to the tumor cells (internal image-type antibodies) showed accelerated metastatic spread. Data are interpreted to mean that MAb-induced inhibition of metastatic spread may be based on 2 independent mechanisms: blockade of metastasis-associated epitopes (i.e., with MAb 1.1ASML) and induction of an anti-mouse Ig response. In the latter case it was irrelevant whether the response was isotype- or idiotype-specific.     

An IgG3 monoclonal antibody established after immunization with GM3 lactone: immunochemical specificity and inhibition of melanoma cell growth in vitro and in vivo

In previous studies, an IgM monoclonal antibody (M2590), established after immunization of C57BL/6 mice with syngeneic B16 melanoma cells, was found to react with melanoma cells, but not with various normal cells and tissues (Taniguchi, M., and Wakabayashi, S., Jpn. J. Cancer Res., 75:418-426, 1984). The structure defined by this antibody was identified as GM3 (Hirabayashi, Y., et al., J. Biol. Chem., 260:13328-13333, 1985) organized in membranes at high density, although the real immunogen was suggested to be GM3 lactone (Nores, G. A., et al., J. Immunol., 139:3171-3176, 1987). Since GM3 lactone was found to be highly immunogenic, we subsequently immunized C57BL/6 mice with GM3 lactone coated on Salmonella minnesotae and established hybridoma DH2, secreting an IgG3 antibody showing preferential reactivity with GM3 lactone over GM3 under certain conditions. The reactivity of the DH2 antibody was competitively inhibited by M2590, and it showed a preferential reactivity with melanoma cells and displayed various immunochemical and immunobiological properties similar to those of M2590. However, DH2 antibody inhibited melanoma cell growth in vivo, induced antibody-dependent cytotoxicity in vitro, and showed a preferential accumulation in melanoma growth in vivo. These properties are characteristic of the IgG3 subclass, in striking contrast to IgM antibody M2590, which does not inhibit cell growth in vivo or in vitro and does not induce antibody-dependent cytotoxicity. Thus, immunization with lactone forms of tumor-associated ganglioside antigens might be useful in the production of antibodies and prevention of tumor cell growth in vivo (antitumor vaccines).     

Immunization of colorectal cancer patients with modified ovine submaxillary gland mucin and adjuvants induces IgM and IgG antibodies to sialylated Tn.

Tn and sialylated Tn (sTn) are blood group-related epitopes expressed on mucins of colon carcinoma and other epithelial tumors and are, therefore, potential targets for immunological control. We have immunized 20 colorectal cancer patients at high risk for recurrence with a vaccine consisting of partially desialylated ovine submaxillary gland mucin (modified OSM) which contains both Tn and sTn determinants. Six patients were treated with modified OSM alone (group 1), eight patients were treated with modified OSM and the immunological adjuvant DETOX (group 2), and six patients were treated with modified OSM and Bacillus Calmette-Guérin (group 3). Pre- and postvaccination sera were tested by enzyme-linked immunosorbent assay and dot blot immune stains for antibodies reactive with modified OSM. Antibody titers increased in 4 of 8 patients immunized with modified OSM and DETOX, in 5 of 6 patients immunized with modified OSM and B. Calmette-Guérin, and in 0 of 6 patients receiving modified OSM without adjuvant. The specificity of induced IgM and IgG antibodies was confirmed by demonstrating reactivity with OSM, bovine submaxillary mucin, and synthetic glycoconjugates sTn-human serum albumin (HSA) and Tn-HSA in enzyme-linked immunosorbent assay and immune stains. Median IgM pre-postvaccination reciprocal titers were 20/80 for Tn-HSA and 10/320 for sTn-HSA. Low level IgG antibody titers against sTn-HSA were detected after vaccination in 7 patients. Toxicity was limited to inflammatory skin reactions at the site of vaccination resulting from the adjuvants. No inflammatory infiltrates were seen in the skin when the modified OSM vaccine was administered in the absence of an immunological adjuvant. These results demonstrate that sTn and Tn can be recognized by the human immune system and that vaccines containing these structures can be administered safely with immunological adjuvants. Attempts to augment the immunogenicity of these carbohydrate antigens by covalent attachment to immunogenic carrier proteins and the use of more potent immunological adjuvants are now being pursued.     

Induction of antibodies reactive with GM2 ganglioside after immunization with lipopolysaccharides from Campylobacter jejuni

Ganglioside GM2, expressed on the surface of some human cancers, is a promising target for immune therapy, since GM2 antibodies are cytotoxic, can be induced in humans by vaccination, and the presence of GM2 antibodies is associated with a better prognosis in melanoma patients. In our efforts to induce long-lived, cytotoxic GM2 antibodies, we investigated lipopolysaccharides (LPS) containing “GM2-like” oligosaccharides. LPS were prepared from Campylobacter jejuni serotypes O:1, O:23, or O:36 (all sharing the oligosaccharide structure GalNAcβ1-4Gal(II³NeuAc)-Hex with ganglioside GM2), and tested for their ability to induce GM2-reactive antibodies. Immunization of NZW rabbits (2 animals per vaccine) with LPS from C. jejuni serotype O:1 in Freund's adjuvant resulted in production of high-titer IgG antibodies reactive with purified bovine brain GM2 in ELISA, dot-blot immune stains and immune thin-layer chromatography, and with GM2 derived from various human tumors by immune thin-layer chromatography. These rabbit antibodies bound to cancer cell lines expressing GM2 on their cell surface, as determined by mixed hemadsorption assays, mediating strong antibody-dependent cellular cytotoxicity (ADCC) with tumor cells expressing cell-surface GM2. Antibodies induced by vaccination with C. jejuni serotype O:1 were higher-titer (IgG ELISA titer > 1:60,000) than antibodies induced by immunization with purified GM2 (IgG ELISA titer > 1:200). Immunization with LPS from C. jejuni serotype O:36 resulted in production of moderately high-titer IgM and low-titer IgG GM2 antibodies. Immunization with LPS from C. jejuni serotype O:23 did not elicit GM2-reactive antibodies. No clinical symptoms were observed in animals immunized with these LPS preparations, with purified GM2 ganglioside, or with LPS derived from C. jejuni serotype O:19 (containing a GMI-like oligosaccharide). Our results indicate that lipopolysaccharides sharing carbohydrate epitopes with gangliosides may be useful immunogens for inducing antibodies to ganglioside antigens. © 1996 Wiley-Liss, Inc.     

Inhibition of growth and metastases in mice by immunization with cholesterol hemisuccinate-enriched tumor cells

Incorporation of cholesterol hemisuccinate (CHS) into the membrane of tumor cell rigidifies the lipid layer, exposes cryptic antigens, and enhances immunogenicity. The local growth and metastatic spread of the 3LL Lewis lung carcinoma were studied in conjunction with immunizations by CHS-enriched 3LL cells. C57BL/6J mice received 2 consecutive immunizations with 10(7) CHS-treated, irradiated (10,000 rad) 3LL cells. Two control groups were immunized with MCA-102 sarcoma cells or CHS-enriched syngeneic spleen cells. All groups were challenged with viable 3LL cells after immunizations. Mice pre-immunized with CHS-enriched 3LL cells showed a delayed tumor growth after subsequent challenge with 3LL. Effect of immunization on the growth of established tumors was examined in 3LL-bearing mice which were treated with 10(7) CHS-enriched tumor cells on days 1-12 after initial tumor implantation. A second identical immunotherapy was given 6 days after the first immunization. Tumor growth was significantly inhibited in mice which received the first immunization 1 day after tumor implantation, while immunization on day 3 or after inhibited the growth rate to a lesser extent. Suppression of pulmonary metastases was assessed after excision of a primary 3LL tumor growing in the foot pad which had reached 8 mm in diameter. Immunization consisted of intraperitoneal injection of 10(7) irradiated CHS-enriched tumor cells following excision and repeated after 6 days. This immunization resulted in a significant decrease in pulmonary metastasis as scored by direct counts of metastatic nodules, by [125I]iododeoxyuridine (125IUdR) incorporation, and by lung weight. Metastatic 3LL cells from nodules which survived immune elimination were isolated and implanted into mice which were pre-immunized with primary 3LL cells enriched with CHS. For comparison, a group of mice was immunized and challenged with primary 3LL cells. Inhibition of tumor growth and pulmonary metastasis formation was observed only in the mice which were challenged with the primary tumor.     

WT1 epitope-specific IgG and IgM antibodies for immune-monitoring in patients with advanced sarcoma treated with a WT1 peptide cancer vaccine

The Wilms'' tumor gene WT1 is highly expressed in various malignancies and may be a common target antigen for cancer immunotherapy. In our group, peptide-based cancer vaccines targeting WT1 CTL epitopes were developed as an immunotherapy for these malignancies. In the present study, WT1 epitope-specific immune responses were analyzed in 31 patients with advanced sarcoma with human leukocyte antigen-A*24:02- and WT1-expressing tumors who received the WT1-235 peptide vaccine as monotherapy. The serum levels of IgG and IgM antibodies against the target epitope WT1-235 and the non-target epitopes WT1-332 and WT1-271 were measured using ELISA. IgM antibodies against WT1-235, WT1-332 and WT1-271 were detected in three (9.6%), four (12.9%) and 20 patients (64.5%), respectively, prior to vaccine administration, indicating immune recognition of the WT1 antigen prior to administering the vaccine. Of 15 patients who had completed the 3-month treatment protocol, WT1-235 IgG was positive in five (33.3%) patients. An enzyme-linked immunospot assay revealed that WT1-235 epitope-specific IL-10 production/secretion in peripheral blood mononuclear cells declined in the first month of vaccine administration in all three patients with positivity for WT1-235 IgM at the start of the vaccine. Furthermore, positivity for both WT1-235 and WT1-271 IgM antibodies at the start of treatment was associated with unfavorable tumor control at 3 months after vaccine administration. These results suggested that WT1 epitope-specific IgG and IgM antibodies may be utilized as immune-monitoring markers for WT1 peptide cancer vaccine immunotherapy. The trials were entered in the University hospital Medical Information Network (UMIN) Clinical Trials Registry (https://www.umin.ac.jp/ctr; no. UMIN000002001 on May 24, 2009 and no. UMIN000015997 on December 20, 2014).     

Effect of immunization with live tularemia vaccine on the growth of various tumor strains in rats

The paper deals with a study of the effect of a single challenge with living tularemia vaccine on the growth of such transplantable tumors as Zajdela's hepatoma, Pliss' lymphosarcoma, Walker's carcinosarcoma, Schwetz' erythromyelosis and sarcoma 45 in Wistar rats. Immunization was followed by a significant (37.2-86%) inhibition of the rate of growth of the said tumors. Ascites was detected in half the vaccinated animals of Zajdela's hepatoma series, this being matched by 100% in controls.     

Detection of IgM and IgG antibodies to Cryptococcus neoformans proteins in blood donors and HIV patients with active cryptococcosis

The serological responses to Cryptococcus neoformans proteins of blood donors and HIV patients with active cryptococcosis from a tropical region were investigated in this study. Exposure to C. neoformans , an organism ubiquitous in the environment, contributes to the antibody responses observed in the blood donors. IgG responses to cryptococcal proteins were stronger than IgM responses in most sera tested in this study. A 53-kDa cryptococcal protein fragment was identified as the most immunoreactive protein on the IgM immunoblots of both blood donors and patients. Overall, there was no obvious difference in IgG responses of patients when compared with blood donors. Some immunogenic protein fragments (27.5, 76, 78 and 91.5 kDa) were detected at least two times more frequently on IgM immunoblots of patients compared with those of blood donors. It is yet to be investigated whether the proteins identified in this study may have any potential to be used as biomarker for cryptococcosis.     

Constructing an adenocarcinoma vaccine: immunization of mice with synthetic KH-1 nonasaccharide stimulates anti-KH-1 and anti-Le(y) antibodies

There is mounting evidence to suggest that immunization-based strategies can be used to mobilize the human immune system against specific carbohydrate antigens displayed on the surface of cancer cells. Following isolation and identification, such antigens can be administered as conjugate vaccines. The tumor-associated carbohydrate antigen KH-1 is 1 such antigen and may serve as a potential target for immunization against adenocarcinoma. However, a serious impediment to the application of a vaccine-based approach involving this antigen is that its availability from natural sources is severely limited. In order to overcome this limitation, we have developed an efficient total synthesis of this complex glycolipid. We have extended our synthesis to reach a structurally related analog in which the ceramide portion of KH-1 is replaced with an allyl substituent. These synthetic advances have led to the preparation of 2 potential vaccine constructs, each based on the conjugation of the KH-1 nonasaccharide and the carrier protein keyhole limpet hemocyanin (KLH). In 1 construct (KH-1-Et-KLH), the nonasaccharide is conjugated to KLH via a simple ethyl linkage, while in the other (KH-1-MMCCH-KLH), conjugation is mediated by a 4-(4-N-maleimidomethyl)cyclohexane-1-carboxyl hydrazide (MMCCH) cross-linker. We report here the immunological properties of these 2 constructs. Mice were immunized with either of the 2 KH-1-KLH vaccine candidates or the KH-1 ceramide, along with the immunological adjuvant QS-21. Immunization with the ceramide served as a negative control and, as expected, failed to stimulate the production of antibodies against the KH-1 glycolipid. The construct in which the KH-1 nonasaccharide is linked to KLH via a simple alkyl chain stimulated significant quantities of IgM antibodies, whereas the construct linked to KLH by MMCCH induced high titers of both IgM and IgG antibodies. Inhibition data demonstrated that antibodies generated in response to immunization with the KH-1-KLH constructs recognize not only the KH-1 antigen but also the Lewis(y) (Le(y)) antigen, which, from a structural perspective, is similar to the 4 residues located at the non-reducing end of the KH-1 nonasaccharide. Thus, the KH-1-KLH constructs elicit an immune response that successfully targets 2 adenocarcinoma markers. As assessed by FACS analysis, the antibodies raised were strongly reactive with the KH-1/Le(y) positive cell line MCF-7 but not with KH-1 and Le(y) negative melanoma cell lines. Based on the results of our study, a KH-1-KLH plus QS-21 vaccine is being prepared for clinical evaluation.     

Variation in agar growth of transformed 3T3 cells after tumor formation in nude mice

Cells from a cloned line of spontaneously transformed 3T3 cells had a colony-forming efficiency in agar (CFEag) of about 10-15% and induced poorly differentiated sarcomas when injected into nude mice. These tumor cells were recultured in vitro and tested for their ability to grow in suspension. Initially, the tumor cells had a CFEag which was a hundredfold to a thousandfold lower than the cells that had been grown only in vitro. After 5-8 further weekly passages, however, the tumor lines recovered their original ability to grow in agar. For determination as to whether this increased CFEag was due to selection of cells with a higher CFEag from the tumor cell population or to adaptation of many of the tumor cells to agar growth, clones were isolated directly from a primary tumor, and each was tested weekly for agar colony formation. All of the tumor clones, as well as the uncloned tumor line, were able to recover their original ability to grow in agar. However, one tumor clone had a relatively high CFEag in the first assay, so the selection hypothesis could not be totally excluded. The initial low CFEag of the recultured cells was not due to the presence of normal nude mouse cells in the population. Before in vivo growth no clones could be isolated from the sublines that had as low a CFEag as the tumor cells isolated after in vivo growth. Tumor cells that had been repeatedly passaged in vivo still had a much lower CFEag than the input cells upon explantation into culture. The results suggest that phenotypic alterations observed during tumor growth and subsequent cultivation have an epigenetic basis.     

Iron nutrition and tumor growth: decreased tumor growth in iron-deficient mice

Groups of 15 mice of three different laboratory strains (BALB/c, C3H/He, DBA/2) were fed on a low iron diet (5 mg iron/kg diet), and three similar groups of 15 mice were maintained on a normal iron diet (312 mg iron/kg diet). When the low iron diet group became iron deficient, tumor cells (5 x 10(5) cells/mouse) of CA07-A (colon adenocarcinoma), HE129 (hepatoma), and M119 (mammary adenocarcinoma) were inoculated s.c. in BALB/c, C3H/He, and DBA/2 mice, respectively. All mice developed tumors, tumors grew more slowly, and the mean tumor sizes were smaller in the low iron diet group at nearly all weekly observations in all three strains of mice. No apparent differences in the behavior, activity (e.g., movement, climbing, running, grooming, etc.), and appearance were observed between low iron diet and normal iron diet mice. The mean body weight of mice at transplantation was less in the low iron than in the normal iron groups for the BALB/c strain but higher in the low iron groups of C3H/He and DBA/2 mice, indicating that food intake of mice on a low iron diet was not impaired. These results suggest that iron nutrition of the host affects tumor growth; tumor cells grow better in an iron-rich environment. This knowledge should be considered when designing treatment for patients with cancer. Iron oversupply in cancer patients might enhance tumor growth and adversely affect cancer therapy.     

Delayed tumor onset and reduced tumor growth progression after immunization with a Her-2/neu multi-peptide vaccine and IL-12 in c-<Emphasis Type="Italic">neu</Emphasis> transgenic mice

Passive immunotherapy with monoclonal antibodies is a routinely performed but cost intensive treatment against certain cancers. Induction of humoral anti-tumor responses by active peptide immunization has therefore become a favorable treatment concept. We have recently identified three peptides representing B-cell epitopes of the extracellular domain of Her-2/neu each of them inducing Her-2/neu specific immune responses with anti-tumor activity in vitro. The present study was performed to evaluate the in vivo protective capacity of a combined vaccination with these three peptides in FVB/N transgenic mice spontaneously developing c-neu overexpressing breast cancers. The three Her-2/neu peptides coupled to tetanus toxoid were administered with or without addition of recombinant IL-12. At the time all untreated mice had developed tumors about 40% of peptide-immunized mice and nearly 60% of mice immunized with the peptide vaccine co-applied with IL-12 remained tumor free. Moreover, co-administration of IL-12 had a significant impact on the retardation of tumor progression. The enhanced anti-tumor efficacy of the vaccine by IL-12 was associated with a Th1 biased immune response as demonstrated by an increased IFN-γ production in vitro and elevated Her-2-specific IgG levels. Our findings clearly demonstrate that this multi-peptide vaccine is effective in tumor prevention and support its use against minimal disease, drug-resistant tumors or even for prophylaxis against cancers overexpressing Her-2/neu. Stefan Wagner and Joanna Jasinska contributed equally to this work.     

Failure of immunotherapy with neuraminidase-treated tumor cell vaccine in mice bearing established 3-methylcholanthrene-induced sarcomas

C3H/HeJ mice bearing MC-80 fibrosarcomas were given immunotherapy consisting of multiple injections of a Vibrio cholerae neuraminidase (VCN)-treated tumor cell vaccine at a site remote from the established tumor. In five separate experiments we were unable to show either partial or complete tumor regression or prolongation of survival for vaccine-treated mice compared to appropriate controls. Further, the use of BCG in addition to VCN-treated tumor cells failed to show any therapeutic efficacy. We could not confirm the successful immunotherapy results reported by others despite multiple efforts of reproduce the immunotherapy model as carefully and precisely as possible.     

Inhibition of multidrug-resistant human tumor growth in athymic mice by anti-P-glycoprotein monoclonal antibodies

In an effort to devise an effective treatment for human drug-resistant cancers, we have developed monoclonal antibodies, MRK16 and 17, reactive to the multidrug transporter protein, P-glycoprotein. The monoclonal antibodies given intravenously effectively prevented tumor development in athymic mice inoculated subcutaneously with drug-resistant human ovarian cancer cells 2780AD. Treatment with MRK16 induced rapid regression of established subcutaneous tumors and apparent cures of some animals. Complement-dependent cytotoxicity (MRK16) and antibody-dependent cell-mediated cytolysis (MRK16 and 17) were observed with these antibodies. These monoclonal antibodies may have potential as treatment tools against multidrug resistant human tumors possessing the P-glycoprotein.     

Mechanism of antitumor activity in mice for anti-epidermal growth factor receptor monoclonal antibodies with different isotypes

In previous studies of monoclonal antibodies (mAbs) against the receptor for epidermal growth factor (EGF) both 528 IgG2a and 225 IgG1 were shown to inhibit growth of A431 cell xenografts in athymic mice. The antitumor activities of the two mAbs were similar and, although they differ in their isotypes, they share many properties. The two mAbs bind to EGF receptors with identical affinities, compete with EGF for binding to EGF receptors, down regulate the receptors identically, block EGF-induced activation of tyrosine protein kinase activity to a comparable degree, and block EGF-induced changes in the proliferation of cultured cells. These similarities in physiological effects permit a direct comparison of the mechanisms of action mAbs of the IgG1 and IgG2a isotypes. We examined in vitro cytotoxicity against A431 cells, using 528 IgG2a and 225 IgG1 mAbs. 528 IgG2a, but not 225 IgG1, demonstrated partial complement-mediated cytotoxicity by the 51Cr release assay and by growth inhibition of cultured A431 cells. 528 IgG2a, but not 225 IgG1, was cytotoxic to A431 cells in the presence of activated peritoneal macrophages, as demonstrated by release of incorporated [3H]thymidine. Neither mAb showed any significant cytotoxicity to A431 cells in the presence of nonadherent spleen cells which contain K-cells. The results of in vitro cytotoxicity experiments suggested that the antitumor activity of 528 IgG2a, but not 225 IgG1, could be mediated by macrophages. This was verified by in vivo experiments in which s.c. tumor cell inocula containing activated macrophages showed enhancement of antitumor effects in animals treated i.p. twice weekly for 3 weeks with suboptimal doses of 528 IgG2a. This enhancement was not observed when 225 IgG1 was used with the same procedure. The results of these experiments suggest that immune mechanisms involving activated macrophages or complement could contribute to the antitumor activity of anti-EGF receptor mAb with the IgG2a isotype, but not with the IgG1 isotype. This observation confirms the findings of others who examined the antitumor activity of IgG2a mAbs in other model systems. IgG1 mAb 225, and possibly IgG2a mAb 528, may prevent growth of human tumor xenografts by altering the physiological functions of the EGF receptor rather than by immune mechanisms.     

Expansion of natural killer cells in mice transgenic for IgM antibody to ganglioside GD2: demonstration of prolonged survival after challenge with syngeneic tumor cells

IgM antibodies to gangliosides, sialic acid-containing glycosphingolipids, have been shown to mediate anti-tumor effects in cancer patients with melanoma and neuroblastoma and to correlate with survival. Mechanisms by which the antibodies induce tumor suppression, however, have not been systematically studied. To investigate this point, we produced and characterized C57BL/6 mice transgenic for IgM antibody to ganglioside GD2. The transgenic (TG) mice showed high IgM, but not IgG antibody titers against GD2 in their sera. No significant clinical symptoms were observed. When EL4 cells, syngeneic T lymphoma that express ganglioside GD2, were injected into TG mice, prolonged survival was observed. Complement-dependent cytotoxicity (CDC) of EL4 cells was mediated with TG mice sera. Neither antibody-dependent cellular cytotoxicity with their sera nor cytotoxic T lymphocyte activity to EL4 cells was shown in TG mice. Spleen lymphocytes from TG mice had increased numbers of natural killer (NK) cells, but not T cells, B cells, or macrophages compared with wild-type mice. Depletion of NK cells with anti-asialo GM1 rabbit serum reduced or abrogated the observed anti-tumor effects, suggesting that NK cells play a major role in tumor eradication or suppression. NK cell activity in TG mice was much higher than wild-type mice. Moreover, TG mice showed prolonged survival after injection with syngeneic B16 melanoma cells, which express GM3, but not GD2 or GD3. Taking these results together, our studies demonstrate that the TG mice have significant anti-tumor characteristics, probably due to CDC and NK cell expansion and activation with anti-ganglioside GD2 antibody.     

Improved vaccine efficacy of tumor exosome compared to tumor lysate loaded dendritic cells in mice

Leukemia immunotherapy frequently does not meet expectation, one of the handicaps being tumor exosome (TEX)‐promoted immunosuppression. We here asked, using the mouse myeloid leukemia WEHI3B and the renal cell carcinoma line RENCA, whether dendritic cell (DC) vaccination suffices to counterregulate TEX‐induced immunosuppression and whether TEX could serve as tumor antigen for DC‐loading. DC‐vaccination significantly prolonged the survival time of WEHI3B‐bearing mice, TEX‐loaded DC (DC‐TEX) being superior to lysate‐loaded DC (DC‐lys), even an excess of TEX not interfering with immune response induction. The superior response to DC‐TEX was accompanied by an increase in WEHI3B‐specific CD4⁺ T cells, evaluated by trogocytosis and proliferation. Similar findings accounted for DC loaded with RENCA TEX. TEX was efficiently taken‐up by DC and TEX uptake supported CD11c, MHCII and IL12 upregulation in DC. Importantly, TEX was partly recruited into the MHCII‐loading compartment such that “TEX” presentation time and recovery in T cells significantly exceeded that of tumor‐lysate. Thus, TEX did not drive DC into a suppressive phenotype and were a superior antigen due to higher efficacy of TEX‐presentation that is supported by prolonged persistence, preferential processing in the MHCII‐loading compartment and pronounced trogocytosis by T helper cells. TEX is present in tumor patients' sera. TEX, recovered and enriched from patients' sera, might well provide an optimized, individual‐specific antigen source for DC‐loading and vaccination.     

PML-RARα-hIL-2DNA疫苗免疫BALB／c小鼠后胸腺初始T细胞水平变化

目的了解PML-RARα-hIL-2基因疫苗免疫小鼠后胸腺初始（naive）T细胞变化情况。方法利用实时定量PCR检测小鼠胸腺组织DNA中T细胞受体删除DNA环（TRECs）的水平，从而评价小鼠胸腺中naiveT细胞含量。结果利用PML-RARα-hIL-2DNA疫苗免疫小鼠后胸腺中所含的TRECs拷贝数明显高于单个基因疫苗PML-RARα或hIL-2组及对照组。结论所构建的PML-RARα-hIL-2双表达质粒可诱导小鼠胸腺产生naive T细胞数量增加，可能与产生更强的细胞免疫应答有关。     

Enhanced tumor growth of both primary and established human and murine tumor cells in athymic mice after coinjection with Matrigel.

Previously we found that the reconstituted basement membrane matrix Matrigel, when premixed with human small-cell lung carcinoma cells and injected subcutaneously into athymic mice, permitted tumor growth, whereas cells injected in the absence of Matrigel did not form tumors. In the present study, we examined additional cell types and determined some of the underlying mechanisms involved in the promotion of tumor formation by Matrigel. The tumor cell lines that we studied included transformed mouse Englebreth-Holm-Swarm tumor cells (T-EHS), human submandibular carcinoma A253 cells, mouse melanoma B16F10 cells, human epidermoid carcinoma KB cells, and human primary renal cell carcinoma cells. When coinjected subcutaneously with Matrigel, these cell lines formed rapidly proliferating tumors. Primary biopsy specimens of human colon carcinoma, when dispersed and coinjected with Matrigel, also formed tumors. Only A253, KB, and B16F10 cells formed small tumors in the absence of Martrigel, but a fivefold to tenfold increase in tumor size was observed in the presence of Matrigel. These data demonstrate a useful method for improving the growth of human tumors in athymic mice.