ANTI-METASTATIC EFFECT OF ONCOLYSATES FROM MURINE MELANOMA CELLS TRANSFECTED WITH RECOMBINANT VACCINIA VIRUS ENCODING HUMAN IL-2

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Characterization of plasma membrane shedding from murine melanoma cells

Tumor cells release intact portions of their plasma membranes in the process of membrane fragment shedding. This released material has been shown to inhibit various synthetic functions of normal cells, which may play an important role in certain patho-physiological events occurring in advanced-stage cancer patients. Our studies on metastatic variants of the murine B16 melanoma, B16-F1 (low incidence of lung colonization) and B16-F10 (high incidence of lung colonization) indicate that the shed membrane fragment material is composed predominantly of vesicles, ranging in size from 20 to 100 nm in diameter. The release of membrane fragments represents a small percentage (approximately 16%) of the total shedding of plasma membrane components. Membrane fragments were shed at a higher rate from the highly "metastatic" (colonizing) B16-F10 cells than from poorly metastatic B16-F1 cells, resulting in a 2-fold greater accumulation of membrane fragment material by cultures of B16-F10 cells than by B16-F1 cultures during the 48-hr assay period. The study of various intracellu ar metabolic processes (protein and RNA synthesis, glycosylation, and generation of ATP) required for the shedding of membrane fragments indicated that the shedding event is only dependent on energy when inhibitors of the above processes are present for 2 hr. Treatment of cells with these inhibitors for 8 hr results in cessation of the shedding process, indicating both a limited pool of components to be shed and the requirement for further synthesis of the shed material. Glycoprotein components of the shed membrane fragments were analyzed by SDS-polyacrylamide gel electrophoresis. In addition to quantitative differences, 2 additional bands were present in fluorographs from SDS-PAGE gels from the B16-F10 membrane fragment material which were not present in fluorographs from B16-F1 fragments. The glycoprotein components of shed membrane fragments were shown to represent selected domains of the cell's plasma membranes, in that only certain plasma membrane glycoproteins are shed as part of membrane fragments. The glycoproteins released as non-particulate molecules into the extracellular environment failed to exhibit these quantitative and qualitative differences.     

NK and CD8+ T cell-mediated eradication of poorly immunogenic B16-F10 melanoma by the combined action of IL-12 gene therapy and 4-1BB costimulation

In previous reports, systemic administration of a stimulatory monoclonal antibody directed against the 4-1BB receptor had no effect on survival or tumor burden in mice inoculated with the poorly immunogenic B16-F10 melanoma. We combined IL-12 gene transfer with 4-1BB costimulation to explore a previously noted cooperative anti-tumor effect against this model tumor. We hypothesize that the innate immune response mediated by IL-12-activated natural killer (NK) cells initiates the activation of the immune system, leading to the priming of T cells, whereas 4-1BB costimulation enhances the function of primed tumor-specific T cells. The effect of the combination therapy on the growth of subcutaneous (s.c.) tumors and pulmonary metastasis was examined. The combination therapy significantly retarded the growth of subcutaneously-inoculated tumors, and 50% of tumor-bearing mice survived with complete tumor regression. In contrast, neither IL-12 gene transfer nor anti-4-1BB antibody administration alone was as effective. Enhanced CTL activity against both B16-F10 tumor cells and TRP-2-pulsed EL4 syngeneic tumor cells was observed in tumor-bearing animals treated with the combination therapy 2 weeks after treatment and, in long-term survivors from this combination therapy, at >120 days. In a pulmonary metastatic model, only the combination therapy generated significant protection against metastasis. In vivo depletion of NK or CD8(+) but not CD4(+) subsets eliminated the protective immunity. Furthermore, NK cell depletion significantly reduced both tumor-specific CTL activity and the number of tumor-specific IFN-gamma-producing cells, suggesting that this synergistic effect requires the participation of both NK and CD8(+) T cells.     

Effective anti-metastatic melanoma vaccination with tumor cells transfected with MHC genes and/or infected with newcastle disease virus (NDV)

The therapeutic efficacy of active immunization with B16-F10.9 melanoma cells transfected with syngeneic major histocompatibility complex (MHC) class-l genes, modified by infection with Newcastle Disease virus (NDV) or modified by both treatments, was compared. B16-F10.9 tumor-bearing mice were treated at various stages of tumor growth and metastasis with irradiated, modified tumor-cell vaccines. Irradiated tumor cells and H-2D^b transfectants did not stimulate anti-tumor immunity while H-2K^b transfectants and NDV-modified F10.9 cells showing low and high expression of MHC class-l genes efficiently prevented metastasis of small established tumors. NDV-modified parental-cell vaccines functioned optimally and improved overall survival by about 60%, also at early stages of metastasis establishment. A synergistic effect of H-2K^b expression and virus modification on rejection of micrometastases was observed in mice bearing advanced tumors. Postoperative vaccination of mice carrying multiple metastases with NDV-modified vaccines caused significant, but incomplete, reduction of metastatic tumor load. The therapeutic effect of NDV-modified tumor vaccines was dependent on multiple immune mechanisms. Depletion of CD8, CD4 or NK cells by in vivo treatment with monoclonal antibodies reversed the immunotherapeutic effects of the vaccine. Thus, tumor xenogenization and gene modification may act synergistically to vaccinate against advanced tumors, while single modalities can effectively vaccinate against metastasis at early stages of tumor growth.     

Aerosol delivery of PEI-p53 complexes inhibits B16-F10 lung metastases through regulation of angiogenesis

Inhibition of pulmonary metastases poses a difficult clinical challenge for current therapeutic regimens. We have developed an aerosol system utilizing a cationic polymer, polyethyleneimine (PEI), for topical gene delivery to the lungs as a novel approach for treatment of lung cancer. Using a B16-F10 murine melanoma model in C57BL/6 mice, we previously demonstrated that aerosol delivery of PEI-p53 DNA resulted in highly significant reductions in the tumor burden (P < .001) in treated animals, and also lead to about 50% increase in the mean length of survival of the mice-bearing B16-F10 lung tumors. The mechanisms of this antitumor effect of p53 are investigated in this report. Here, we demonstrate that the p53 transfection leads to an up-regulation of the antiangiogenic factor thrombospondin-1 (TSP-1) in the lung tissue and the serum of the mice. Furthermore, there is a down-regulation of vascular endothelial growth factor (VEGF) in the lung tissue and serum of the B16-F10 tumor-bearing mice treated with PEI-p53 DNA complexes, compared with untreated tumor-bearing animals. In addition, staining for von Willebrand factor (vWF), a marker for the angiogenic blood vessels, revealed that p53 treatment leads to a decrease in the angiogenic phenotype of the B16-F10 tumors. Immunohistochemistry for transgene expression reveals that the PEI-p53 aerosol complexes transfect mainly the epithelial cells lining the airways, with diffuse transfection in the alveolar lining cells, as well as, the tumor foci in the lung tissue. There was also some evidence of apoptosis in the lung tumor foci of animals treated with p53. The data suggest that aerosol delivery of PEI-p53 complexes leads to inhibition of B16-F10 lung metastases, in part by suppression of angiogenesis.     

In vivo induction of antitumor immunity and protection against tumor growth by injection of CD154-expressing tumor cells

As they should enhance tumor-specific antigen presentation by dendritic cells, tumor cell lines genetically modified to express CD154 molecules have been used in an attempt to induce protective antitumor immunity. Two murine models were used: the major histocompatibility complex (MHC) class I negative melanoma B16F10 and the MHC class I positive mammary adenocarcinoma TS/A. CD154 or mock-transfected B16F10 or TS/A cells were injected subcutaneously into H-2-compatible B6D2 mice. CD154 expression by tumor cells induced a complete rejection (in the TS/A model) or a striking reduction (in the B16F10 model) of modified tumors growth, but also a significant protection against the growth of mock tumor cells injected simultaneously, either mixed with the CD154-expressing tumor cells, or in the other flank of mice. Thirty days after CD154-expressing tumor rejection, splenic lymphocytes from surviving tumor-free mice were able to inhibit tumor proliferation in vitro and significant amounts of IFN-gamma were detected in the sera of these mice. Growth kinetics of mock and CD154-expressing tumors in immunocompetent versus nude mice suggest that T lymphocytes and natural killer cells responses are implicated in this antitumor immunity. The injection of CD154-expressing tumor cell induced an antitumor protective response, both locally and distant from the injection site. The effect was most pronounced in MHC class I expressing TS/A tumor model.     

Effects of hyperoxia on B16-F10 cells in vivo

The in vivo effects of hyperoxia were studied in lung colonies formed by B16-F10 melanoma cells in C57BL/6 mice. Several antioxidant defenses were found to change with in vivo exposure: glutathione reductase and glucose-6-phosphate dehydrogenase activities decreased as compared with levels in the cultured cells, glutathione peroxidase activity dramatically increased, and Mn-superoxide dismutase activity and levels of total glutathione were similar in vivo and in vitro. Exposure of tumor-bearing animals to 70%, O2 for 3 weeks did not alter the antioxidant defenses measured in the tumors. One hundred percent O2 exposure did not affect either initial arrest or subsequent retention of radiolabeled B16-F10 cells in the lung. Likewise, hyperoxia did not appear to alter cell division in B16-F10 cells growing in the lung. These results are consistent with our previous studies indicating that the B16-F10 cell line is resistant to levels of O2 in vivo that adversely affect other tumor cell lines.     

Role of the thymus and T-cells in slow growth of B16 melanoma in old mice

Clinical observations suggest that tumors grow more slowly in aged subjects. To investigate the influence of age on tumor growth, we injected the same number of cultured B16 melanoma cells into C57BL/6 mice of various ages. B16 melanoma cells, inoculated s.c., grew more slowly in old (18-20-month-old) as compared to young (6-8-week-old) mice. In young tumor-bearing mice there was a significant increase in the number and the proliferative response to phytohemagglutinin and concanavalin A of splenic T-cells as compared to old tumor-bearing animals. There was no difference in the response of B-lymphocytes from old and young tumor-bearing mice to lipopolysaccharide. The positive association between T-cells and the rate of tumor growth was also suggested by the slower growth of melanoma cells in thymectomized or thymectomized and anti-theta antiserum-treated young mice. Finally, the age-associated difference in tumor growth could be transferred by spleen cells from old or young mice to thymectomized and lethally irradiated syngeneic young animals. Young mice with rapidly growing B16 melanoma tumors have increased numbers and proliferative responses of thymic-derived lymphocytes. It is likely that T-cells or their products facilitate the growth of B16 tumor cells.     

Lipoteichoic acid of Bifidobacterium in combination with 5-fluorouracil inhibit tumor growth and relieve the immunosuppression

To investigate the therapeutic efficacy of lipoteichoic acid of Bifidobacterium (BLTA) in combination with 5-fluorouracil (5-FU) treatment on the mice bearing inoculated hepatoma-22 (H₂₂) cells and the effects of BLTA on immunological regulation of organism, and explore its mechanisms.MethodsTumor-bearing mice were treated with 5-FU alone, BLTA alone or BLTA in combination with 5-FU. The tumor size were observed and measured regularly. The growth inhibiting rate (IR) of tumor was detected. MTT assay was used to evaluate the proliferation of T lymphocytes and splenic NK cell and CTL activity. Enzyme linked immunosorbent assay (ELISA) was used to detect the change of IFN-Γ. FCM was used to detect T subgroup ratio of spleen cells of tumor-bearing mice. Expression change of mRNA and proteins of Foxp3 and TIM-3 were detected by Real-Time-PCR and Western blot in tumor-bearing mice tumor tissue.ResultsBoth 5-FU and BLTA had inhibition effect on tumor-growth. While in the 5-FU + BLTA group, the inhibition of tumor growth was more significant, with increased T lymphocyte proliferation and IFN-Γproduction of spleen cells. Spleen cells of tumor-bearing mice had high CD4⁺CD25⁺regulatory T cell (CD4⁺CD25⁺T_reg) ratio and high mRNA and proteins expression of Foxp3 and TIM-3, but in the BLTA and 5-FU group, CD4⁺CD25⁺T_reg ratio degraded, with down regulation mRNA and proteins expression of Foxp3 and TIM-3. But CD4⁺ T cells also decreased in spleen cells of tumor-bearing mice by alone 5-FU treated, splenic NK cell and CTL activity also degraded, while CD4⁺ T cells and splenic NK cell and CTL activity significantly increased by BLTA treated. BLTA in combination with 5-FU could also enhance the ratio of CD4⁺ T cells and splenic NK cell and CTL activity.ConclusionThe present study suggested that BLTA in combination with 5-FU could enhance antitumor effect, with inhibiting TIM-3/TIM-3L pathway, cutting down immunosuppressive activity of CD4⁺CD25⁺ T_reg and enhancing cell-mediated immunity.     

Administration of 6-gingerol greatly enhances the number of tumor-infiltrating lymphocytes in murine tumors

Tumor-infiltrating lymphocytes (TILs) play critical roles in host antitumor immune responses. It is known that cancer patients with tumor-reactive lymphocyte infiltration in their tumors have better prognoses, while patients with tumors infiltrated by immunosuppressive cells have worse prognoses. We found that administration of 6-gingerol, which is a component of ginger, inhibited tumor growth in several types of murine tumors, such as B16F1 melanomas, Renca renal cell carcinomas and CT26 colon carcinomas, which were established by inoculating tumor cells on the flanks of mice. However, administration of 6-gingerol did not lead to complete eradication of the tumors. 6-Gingerol treatment of tumor-bearing mice caused massive infiltration of CD4 and CD8 T-cells and B220(+) B-cells, but reduced the number of CD4(+) Foxp3(+) regulatory T-cells. The CD8 tumor-infiltrating T lymphocytes in 6-gingerol-treated mice strongly expressed IFN-γ, a marker of activation of cytotoxic T lymphocytes (CTL) CD107a and chemokine receptors that are expressed on T(H) 1 cells, such as CXCR3 and CCR5. To test whether 6-gingerol could promote infiltration of tumor antigen-specific CD8 T-cells into tumors, we adoptively transferred CFSE-labeled OT-1 CD8 T-cells into EG7 tumor-bearing mice. We found that CD8 T cells isolated from 6-gingerol pretreated OT-1 mice, but not from control OT-1 mice, massively infiltrated tumors and tumor draining lymph nodes and divided several times. Our results strongly suggest that 6-gingerol can be used in tumor immunotherapy to increase the number of TILs.     

The changing pattern of the splenic lymphocyte subsets in tumor-bearing mice after oral treatment with OK-432.

The aim of this study was to investigate the influence of oral administration of OK-432 on the tumor growth of tumor-bearing mice. In addition, the changing pattern of the splenic lymphocyte subsets of tumor-bearing mice was evaluated by flow cytometry. OK-432 at a dose of 0.1, 1 or 10 KE was administered orally every 3 days or every other day for 30 days to subcutaneously Meth A tumor-inoculated mice. The tumor growth was significantly inhibited in the 1 KE every 3 days group, in the 1 KE every other day group and in the 10 KE every 3 days group. In the 10 KE every other day group, OK-432 inhibited the tumor growth on days 10 and 20, while the agent did not show a marked inhibitory effect on day 30. The percentages of splenic L3T4-positive cells and splenic asialo GM1-positive cells were significantly increased in the 1 KE every other day group, while the Lyt2+/Thy1.2+ ratio was decreased. On the other hand, in the 10 KE every other day group, OK-432 showed no effect on the percentages of splenic L3T4-positive cells and Lyt2+/Thy1.2+ ratio on days 20 and 30. Our results suggest that the antitumor effect of oral administration of OK-432 may be correlated with the changing pattern of L3T4-positive cells and Lyt2+/Thy1.2+ ratio.     

Anti tumor activities of lentinan and micellapist in tumor-bearing mice

Although Lentinan (LNT) is sold as a medicine, and Micellapist (MME) sold as a food supplement, both LNT and MME are beta-glucans isolated from the Shiitake mushroom (Lentinula edodes). These two substances have been thought to be the same component of Shiitake. In the present study, we evaluated anti tumor activities of LNT and MME in tumor-bearing mice (B10.D2 mice implanted with S908D2 tumor cells) and examined the mechanism of immunopotentiation of these substances. The tumor growth was significantly suppressed in the LNT-treated group. In ex vivo evaluation, the tumor cytotoxicity was significantly reduced by a treatment of splenocytes with anti-CD8 antibody in the LNT-treated group. Furthermore, the tumor cytotoxicity of the LNT-treated group was also significantly reduced by a treatment of splenocytes with anti-CD8 antibody and its complement and with an anti-CD4 and its complement in the effector phase and the induction phase, respectively. A significant prolongation of the survival of tumor-bearing mice as compared to the untreated control group was noted in the LNT-treated group. In the mice treated intraperitoneally with LNT, CD8-positive cells appeared to have suppressed tumor cell proliferation. CD4-positive cells appeared to be involved in this activity of CD8-positive cells. On the other hand, orally administered MME has exerted no clear cytotoxic effects.     

吉西他滨化疗联合树突状细胞瘤内注射对小鼠巨大淋巴瘤的治疗作用

目的：观察吉西他滨对荷B细胞淋巴瘤小鼠脾脏中髓源抑制性细胞（myeloid derived suppressor cell, MDSC）的影响,以及吉西他滨化疗联合树突状细胞（dendritic cells, DCs）治疗巨大淋巴瘤的疗效。方法：小鼠皮下接种A20淋巴瘤细胞,30 d后形成巨大肿瘤,流式细胞仪分析吉西他滨化疗前后荷瘤小鼠脾脏中Gr1+CD11b+ MDSC的比例,免疫磁珠纯化的脾脏MDSC体外加入吉西他滨共培养后,AnnexinV/PI标记法检测细胞凋亡;观察荷瘤小鼠接受吉西他滨化疗联合DCs瘤内注射后肿瘤生长情况及小鼠存活期。结果：荷A20淋巴瘤小鼠脾脏中MDSC的比例显著上调,是正常小鼠脾脏中的10倍以上。体外吉西他滨时间依赖性诱导MDSC凋亡与坏死;荷瘤小鼠体内注射吉西他滨后,脾脏中绝大部分的MDSC被清除。单独吉西他滨注射或DCs瘤内注射对肿瘤生长产生一定的抑制作用,小鼠平均存活天数分别为（48.8±3.6）d和（47.2±7.4）d,而对照组小鼠平均存活天数为（38.8±2.2）d;吉西他滨化疗联合DCs瘤内注射后瘤体持续显著缩小,60%小鼠存活时间均超过90 d。结论：吉西他滨可有效清除荷瘤小鼠脾脏MDSC,吉西他滨化疗与DCs瘤内注射免疫治疗具有协同效应,可以提高对巨大淋巴瘤的疗效,本实验为应用生物化疗综合治疗模式治疗复发、难治性淋巴瘤提供了实验依据。     

IL-2重组痘苗病毒修饰的肿瘤细胞破碎物局部应用后的抗肿瘤作用研究

细胞因子基因转染的瘤苗在体内具有明显的抗肿瘤作用,但逆转录病毒载体转染的肿瘤细胞作为瘤苗在制备及保存上仍然存在不足。本文采用编码人IL-2基因的重组痘苗病毒载体(rVV-IL-2)转染B16-F10小鼠黑色素瘤细胞,经超声破碎及高速离心,制成IL-2基因转染的肿瘤细胞破碎物(IL-2VBO),以此作为瘤苗,局部注射治疗荷瘤小鼠,结果明显抑制了小鼠肿瘤的生长,延长其存活期,外周血淋巴细胞对B16-F10细胞的杀伤活性明显增高,而对YAC-1细胞的杀伤活性则增加不明显,表明IL--2VBO诱导了机体对B16-F10特异性的免疫功能。由于IL-2VBO制备方便,易于保存,同时由于痘苗病毒本身可加强诱导出的免疫反应,因此可望作为一种新的瘤苗应用于肿瘤的主动性免疫治疗。     

石墨烯发热膜的抑瘤作用初探

目的:初步探讨石墨烯发热膜的抗肿瘤作用。方法:体外使用96孔平底板培养对数期生长的CCD-1095SK、MCF-7、A375和B16-F10细胞,使用石墨烯发热膜或温箱在不同温度（37 ℃、40 ℃、41.5 ℃、43 ℃）下恒温处理1小时,继续培养24小时后检测细胞生存率。体内接种黑色素瘤细胞株B16-F10于6~8周龄C57BL/6小鼠和裸鼠,C57BL/6小鼠使用石墨烯发热膜处理（38.5 ℃、39.5 ℃和40.5 ℃,30分钟/次,2次/天）,同时给予达卡巴嗪（dacarbazine,DTIC）80 mg/kg或PBS作为控制,每两天测量一次肿瘤体积并记录小鼠的体重和生存状况,接种后第21天处死小鼠剥离瘤体,称重,多聚甲醛固定后进行HE染色。裸鼠使用石墨烯发热膜处理（37 ℃、38.5 ℃和40 ℃,30分钟/次,2次/天）,每两天测量一次肿瘤体积并记录生存状况。结果:体外石墨烯发热膜处理达到40 ℃时,对MCF-7和A375细胞增殖具有抑制作用,但对于CCD-1095SK和B16-F10细胞,需要达到41.5 ℃才具有增殖抑制作用。在免疫健全的C57BL/6小鼠模型中,石墨烯发热膜40.5 ℃处理组肿瘤体积较控制组减小,石墨烯发热膜40.5 ℃处理和DTIC联用组的肿瘤体积较单独处理组减小。对于免疫不全裸鼠肿瘤模型,石墨烯发热膜处理未能减小肿瘤体积,也未能延长小鼠的生存期。结论:体外石墨烯发热膜处理具有抑制肿瘤细胞增殖的作用,体内联合DTIC和石墨烯发热膜处理具有抑制B16-F10肿瘤模型生长的作用,其机制有可能是间接增强了抗肿瘤免疫应答。     

Activation in vitro of mouse macrophages by syngeneic, allogeneic, or xenogeneic lymphocyte supernatants.

Macrophages from normal C57BL/6 mice, those with a subcutaneous B16 melanoma, and mice immunized against the tumor were examined for in vitro cytotoxicity to B16 tumor cells. Macrophages were treated by incubation with supernatants from B16 cells grown either in unmixed cultures or in cultures containing syngeneic, normal, or sensitized allogeneic (A mouse), or xenogeneic (rat) lymphocytes. The various treated and untreated macrophages were then cultured for 5 days with viable B16 cells prelabeled with 125I-5-iodo-2'-deoxyuridine; the cultures were terminated, and the extent of destruction of the B16 target cells was determined from the amounts of radioactivity remaining in adherent tumor cells. Of the untreated macrophages, only those from immunized mice were cytotoxic to the tumor cells; macrophages from normal and tumor-bearing mice became cytotoxic by incubation with supernatants from cultures containing lymphocytes from immunized syngeneic mice, sensitized allogeneic mice, or sensitized rats; and macrophages incubated with supernatants from cultures containing normal nonsensitized allogeneic or xenogeneic lymphocytes showed no cytotoxicity. Thes results suggested that macrophages from tumor-bearing animals are potentially cytotoxic to their syngeneic tumors and can be activated by mediators released from sensitized syngeneic, allogeneic, and/or xenogeneic lymphocytes in vitro.     

High intensity focused ultrasound enhances anti-tumor immunity by inhibiting the negative regulatory effect of miR-134 on CD86 in a murine melanoma model

HIFU has been demonstrated to enhance anti-tumor immunity, however, the mechanism of which has not been well elucidated. Emerging evidence indicates that miRNAs play important roles in immune response. In this study, we used the B16F10 melanoma allograft mouse model to investigate the role of miRNAs in HIFU-enhanced anti-tumor immunity. We found that HIFU treatment decreased circulating B16F10 cells and pulmonary metastasis nodules while increased IFN-γ and TNF-α in the peripheral blood and cumulative mouse survival, which was associated with inhibition of miR-134 expression and activation of CD86 expression in tumor tissues. Further, we determined that miR-134 directly binds to the 3′UTR of CD86 mRNA to suppress its expression in B16F10 cells. When B16F10 cells transfected with miR-134 were co-cultured with normal splenic lymphocytes, the secretion of IFN-γ and TNF-α from lymphocytes was reduced and B16F10 cell survival was increased. HIFU exposure efficiently decreased miR-134 while increased CD86 expression in B16F10 cells in vitro. CD86 knockdown with siRNA markedly rescued the viability of HIFU-treated B16F10 cells that co-cultured with lymphocytes. Altogether, our results suggest that HIFU down-regulates miR-134 to release the inhibition of miR-134 on CD86 in melanoma cells, thereby enhancing anti-tumor immune response.     

Efficient inducation of local and systemic antitumor immune response by liposome-mediated intratumoral co-transfer of interleukin-2 gene and interleukin-6 gene.

Interleukin 2 (IL-2) expressing plasmid and interleukin 6 (IL-6)-expressing plasmid were encapsulated in liposome and administrated intratumoraly into tumor-bearing mice 4 days after subcutaneous inoculation of B16F10 melanoma cells. The results showed that treatment of tumor-bearing mice with IL-2 gene or IL-6 gene transfer inhibited the growth of subcutaneous tumor and prolonged the survival of tumor-bearing mice significantly when compared with the treatment of PBS or control gene transfer mediated by liposome (P < 0.01). Combined transfer of IL-2 gene and IL-6 gene was found to elicit inhibitory effects on the growth of B16F10 tumor more significantly and prolonged the survival period of tumor-bearing mice more obviously. We investigated the local immunity in tumor microenvironment and found that IL-2 and IL-6 gene transfer could significantly increase the expression of lymphocyte function-associated antigen-1 on tumor infiltrating lymphocytes (TIL) and MHC-I molecule on tumor cells freshly isolated from the tumor mass. The NK and CTL activity of TIL increased markedly after the combined transfer of these two cytokine genes. We also observed the systemic antitumor immune response in the tumor-bearing mice and demonstrated that NK and CTL activity of splenocytes and the production of IL-2, tumor necrosis factor and interferon-gamma from splenocytes increased obviously in mice after the combined transfer of IL-2 and IL-6 gene. In conclusion, local and systemic antitumor immunity of the tumor-bearing host could be induced efficiently after the combined gene transfer. The enhanced specific and non-specific antitumor immunity might be responsible for the more potent antitumor effects of the combined gene therapy.     

Reduced tumorigenicity of B16-F10 mouse melanoma cells transfected with mycobacterial antigen 85A

Immunotherapy based on the administration of the mycobacterium bacillus Calmette-Guerin has been successfully used in the treatment of in situ transitional cell bladder cancer, and may be applicable to the treatment of cutaneous malignant melanoma. Antigen 85A (Ag85A) and heat shock protein 65 kDa (hsp65) are major secreted proteins of Mycobacterium species and potent stimulators of cell-mediated immunity. This study evaluated the ability of Ag85A and hsp65 gene transfection to limit tumor growth by B16-F10 mouse melanoma cells. Immunoblotting confirmed protein expression and secretion by B16-F10 cells that were transiently transfected with plasmid DNA containing the Ag85A or hsp65 gene. Groups of syngeneic C57BL/6 mice were injected subcutaneously with 1x10(5) untransfected B16-F10 cells or B16-F10 cells transiently transfected with either empty vector or vector containing the Ag85A or hsp65 gene. Ag85A-expressing B16-F10 cells exhibited a dramatic 76% reduction (p<0.05, Mann-Whitney U test) in tumor weight in comparison to empty vector controls at 14 days post-inoculation. In contrast, hsp65-transfected B16-F10 cells did not show any change in tumorigenicity. Decreased tumorigenicity by Ag85A-transfected B16-F10 cells was not due to a reduced ability of Ag85A-transfected B16-F10 cells to proliferate since both mock- and Ag85A-transfected B16-F10 cells showed increased in vitro proliferation in comparison to untransfected cells. Hematoxylin and eosin staining revealed that Ag85A-transfected B16-F10 tumors contained an inflammatory leukocyte infiltrate that was not present in hsp65-transfected tumors. Reduced tumor progression by Ag85A-transfected B16-F10 melanoma cells suggests that immunotherapy based on the transient induction of Ag85A expression may be an effective approach for the treatment of cutaneous malignant melanoma.