Survival Period Of Tumor-bearing Mice Research Articles

Chemotherapy-Induced Cellular Senescence Promotes Stemness of B-Cell Non-Hodgkin's Lymphoma Via CCL21/CCR7/NF-Κb Signaling Activation

A bs tract: Resistance to existing therapies is currently the main reason for treatment failure in refractory/relapsed B-NHL patients, and treatment-induced cellular senescence (TIS) is one of the important mechanisms of tumor drug resistance. In our previous studies, we found that the anti-apoptotic and tumorigenic ability of chemotherapy-induced senescent B-NHL cells was significantly enhanced, and the survival period of tumor-bearing mice was significantly shortened, but the mechanism is still unclear. In this study, we identified the C-C chemokine receptor 7 (CCR7) by single-cell RNA-sequencing, which showed significant differential expression in senescent B-NHL cell population and non-senescent cell population. CCL21/CCR7 dependent B-NHL-TIS initiates downstream transcription of NF-κB, thereby enhancing phenotypic and functional stemness features, including the up-regulation of stemness markers, CD34, CD44, LGR5, CD150, and stronger colony forming ability and cell sphere forming ability. The analysis results of clinical patients showed that the expression of CCR7 in the peripheral blood of B-NHL patients was significantly higher than that of healthy normal people and leukemia patients. The expression of CCR7 in peripheral blood of B-NHL patients before treatment was significantly lower than that of relapsed patients, and The expression in abnormal B lymphocyte population is significantly higher than that in normal T and B lymphocyte population, high expression of CCR7 is associated with recurrence and poor prognosis in B-NHL patients. Targeting CCR7/NF-κB signaling has positive significance in inhibiting the acquisition and maintenance of stemness in aging B-NHL cells and preventing tumor drug resistance and recurrence. K ey words: Stress-induced senescence; CCR7; CCL21; senescence related stemness; B-cell non-Hodgkin's lymphoma

Engineered DBCO+PD-1 Nanovesicles Carrying 1-MT for Cancer-Targeted Immunotherapy.

Liver cancer cells evade immune surveillance and anticancer response through various pathways, including the programmed death-ligand 1 (PD-L1)/programmed death-1 (PD-1) immune checkpoint axis that exhausts CD8+ T cells. Inhibitors or antibodies of the PD-L1/PD-1 signaling axis are considered promising drugs for cancer immunotherapy and exhibit favorable clinical responses. However, adverse effects, immune tolerance, and delivery barriers of most patients limit the clinical application of PD-L1/PD-1 antibodies. Thus, it is critical to develop a novel delivery strategy to enhance anticancer immunotherapy. In this study, we bioengineered cell membrane-derived nanovesicles (NVs) presenting PD-1 proteins and dibenzocyclooctyne (DBCO) to encapsulate 1-methyltryptophan (1-MT) (DBCO+PD-1@1-MT NVs). DBCO can specifically interact with N-azidoacetylmannosamine-tetraacetylate (Ac4ManN3) labeled onto metabolic cells for targeted killing of cancers. We next explored the effects of DBCO+PD-1@1-MT NVs on anticancer Hepa1-6 cells in vitro and in vivo. Results showed that PD-1@1-MT NVs dramatically inhibited Hepa1-6 proliferation, promoted peripheral blood mononuclear cell (PBMC) expansion, and strengthened anticancer therapy via blockading the PD-1/PD-L1 immune checkpoint axis, owing to the 1-methyltryptophan (1-MT) enhancement of anticancer immunotherapy efficacy through suppressing the activity of indoleamine 2,3-dioxygenase (IDO). Thus, 1-MT was encapsulated into PD-1 NVs to synergistically enhance cancer immunotherapy. Results have shown that PD-1@1-MT NVs obviously attenuated tumor growth, promoting IFN-γ production, increasing the T cells infiltration in tumors and spleens, and improving the survival period of tumor-bearing mice compared to monotherapy. Therefore, we propose a promising delivery strategy of the combination of DBCO+PD-1 NVs and 1-MT for specific and effective cancer-targeted immunotherapy.

Gold Nanoclusters-Based NIR-II Photosensitizers with Catalase-like Activity for Boosted Photodynamic Therapy.

Photodynamic therapy (PDT) under fluorescence imaging as a selective and non-invasive treatment approach has been widely applied for the therapy of cancer and bacterial infections. However, its treatment efficiency is hampered by high background fluorescence in the first near-infrared window (NIR-I, 700–900 nm) and oxygen-dependent photosensitizing activity of traditional photosensitizers. In this work, we employ gold nanoclusters (BSA@Au) with the second near-infrared (NIR-II, 1000–1700 nm) fluorescence and catalase-like activity as alternative photosensitizers to realize highly efficient PDT. The bright NIR-II fluorescence of BSA@Au enables the visualization of PDT for tumor with a high signal-to-background ratio (SBR = 7.3) in 4T1 tumor-bearing mouse models. Furthermore, the catalase-like activity of BSA@Au endows its oxygen self-supplied capability, contributing to a five-fold increase in the survival period of tumor-bearing mice receiving boosted PDT treatment compared to that of the control group. Moreover, we further demonstrate that BSA@Au-based PDT strategy can be applied to treat bacterial infections. Our studies show the great potential of NIR-II BSA@Au as a novel photosensitizer for boosted PDT against cancer and bacterial infections.

Inhibitory of active dual cancer targeting 5-Fluorouracil nanoparticles on liver cancer in vitro and in vivo.

The chitosan (CS) material as the skeleton nano-drug delivery system has the advantages of sustained release, biodegradability, and modifiability, and has broad application prospects. In the previous experiments, biotin (Bio) was grafted onto CS to synthesize biotin-modified chitosan (Bio-CS), and it was confirmed that it has liver cancer targeting properties. Single-targeted nanomaterials are susceptible to pathological and physiological factors, resulting in a state of ineffective binding between ligands and receptors, so there is still room for improvement in the targeting of liver cancer. Based on the high expression of folate (FA) receptors on the surface of liver cancers, FA was grafted onto Bio-CS by chemical synthesis to optimize the synthesis of folic acid-modified biotinylated chitosan (FA-CS-Bio), verified by infrared spectroscopy and hydrogen-1 nuclear magnetic resonance spectroscopy. The release of FA-CS-Bio/fluorouracil (5-FU) had three obvious stages: fast release stage, steady release stage, and slow release stage, with an obvious sustained release effect. Compared with Bio-CS, FA-CS-Bio could promote the inhibition of the proliferation and migration of liver cancer by 5-FU, and the concentration of 5-FU in hepatoma cells was significantly increased dose-dependently. Laser confocal experiments confirmed that FA-CS-Bio caused a significant increase in the fluorescence intensity in liver cancer cells. In terms of animal experiments, FA-CS-Bio increased the concentration of 5-FU in liver cancer tissue by 1.6 times on the basis of Bio-CS and the number of monophotons in liver cancer tissue by in vivo dynamic imaging experiments was significantly stronger than that of Bio-CS, indicating that the targeting ability of FA-CS-Bio was further improved. Compared with Bio-CS, FA-CS-Bio can significantly prolong the survival time of 5-FU in the orthotopic liver cancer transplantation model in mice, and has a relieving effect on liver function damage and bone marrow suppression caused by 5-FU. In conclusion, FA-CS-Bio nanomaterials have been optimized for synthesis. In vivo and in vitro experiments confirmed that FA-CS-Bio can significantly improve the targeting of liver cancer compared with Bio-CS. FA-CS-Bio/5-FU nanoparticles can improve the targeted inhibition of the proliferation and migration of liver cancer cells, prolong the survival period of tumor-bearing mice, and alleviate the toxic and side effects.

LncRNA-IMAT1 Promotes Invasion of Meningiomas by Suppressing KLF4/hsa-miR22-3p/Snai1 Pathway.

Malignant meningiomas often show invasive growth that makes complete tumor resection challenging, and they are more prone to recur after radical resection. Invasive meningioma associated transcript 1 (IMAT1) is a long noncoding RNA located on Homo sapiens chromosome 17 that was identified by our team based on absolute expression differences in invasive and non-invasive meningiomas. Our studies indicated that IMAT1 was highly expressed in invasive meningiomas compared with non-invasive meningiomas. In vitro studies showed that IMAT1 promoted meningioma cell invasion through the inactivation of the Krüppel-like factor 4 (KLF4)/hsa-miR22-3p/Snai1 pathway by acting as a sponge for hsa-miR22-3p, and IMAT1 knockdown effectively restored the tumor suppressive properties of KLF4 by preserving its tumor suppressor pathway. In vivo experiments confirmed that IMAT1 silencing could significantly inhibit the growth of subcutaneous tumors and prolong the survival period of tumor-bearing mice. Our findings demonstrated that the high expression of IMAT1 is the inherent reason for the loss of the tumor suppressive properties of KLF4 during meningioma progression. Therefore, we believe that IMAT1 may be a potential biological marker and treatment target for meningiomas.

MEOX2-mediated regulation of Cathepsin S promotes cell proliferation and motility in glioma

Nuclear transcription factor Mesenchyme Homeobox 2 (MEOX2) is a homeobox gene that is originally discovered to suppress the growth of vascular smooth muscle and endothelial cells. However, whether or not it is connected to cancer is yet unknown. Here, we report that MEOX2 functions as a tumor-initiating element in glioma. Bioinformatic analyses of public databases and investigation of MEOX2 expression in patients with glioma demonstrated that MEOX2 was abundant at both mRNA and protein levels in glioma. MEOX2 expression was shown to be inversely linked with the prognosis of glioma patients. MEOX2 inhibition changed the morphology of glioma cells, inhibited cell proliferation and motility, whereas had no effect on cell apoptosis. Besides, silencing MEOX2 also hampered the epithelial-mesenchymal transition (EMT), focal adhesion formation, and F-actin assembly. Overexpression of MEOX2 exhibited opposite effects. Importantly, RNA-sequencing, ChIP-qPCR assay, and luciferase reporter assay revealed Cathepsin S (CTSS) as a novel transcriptional target of MEOX2 in glioma cells. Consistently, MEOX2 causes glioma tumor development in mice and greatly lowers the survival period of tumor-bearing mice. Our findings indicate that MEOX2 promotes tumorigenesis and progression of glioma partially through the regulation of CTSS. Targeting MEOX2-CTSS axis might be a promising alternative for the treatment of glioma.

A practical strategy to subcutaneous administered in-situ gelling co-delivery system of arsenic and retinoic acid for the treatment of acute promyelocytic leukemia

Arsenic trioxide (ATO) combined with all trans retinoic acid (ATRA) is the first choice for the treatment of low and medium risk acute promyelocytic leukemia (APL). Clinical studies reported that the combination of ATO and ATRA could achieve a significant curative effect. However, the retinoic acid syndrome, serious drug resistance and the short half-life in vivo which lead to frequent and large dose administration limit the application of ATRA. In addition, the preparations of arsenic are conventional injections and tablets in clinic, which has poor patients' compliance caused by frequent long-term administration and serious side effects. In order to overcome the above limitations, a phospholipid phase separation gel (PPSG) loaded with ATO and ATRA was developed. ATO+ATRA-PPSG (AAP), as a biodegradable sustained-release delivery system, was the first achievement of co-delivery of hydrophilic ATO and lipophilic ATRA with high drug loading which is the main problem in the application of nano preparation. The prepared PPSG displayed high safety and biocompatibility. The drug in PPSG was released slowly and continuously in vivo and in vitro for up to 10 d, which could reduce the side effects caused by the fluctuation of blood drug concentration and solve the problem of the long treatment cycle and frequent administration. In vivo pharmacokinetics depicted that PPSG could improve the bioavailability, decrease the peak concentration, and prolong the t1/2 of ATO and ATRA. Particularly, AAP significantly inhibited the tumor volume, extended the survival period of tumor-bearing mice, and promoted the differentiation of APL cells into normal cells. Therefore, ATO+ATRA-PPSG not only could co-load hydrophilic ATO and lipophilic ATRA according to the clinical dosage, but also possessed the sustained-release and long-acting treatment effect which was expected to reduce administration time and ameliorate compliance of patients. Thus, it had great potential for clinical transformation and application.

Mechanisms of Fritillariae Thunbergii Flos in lung cancer treatment from a systems pharmacology perspective

Ethnopharmacological relevanceFritillariae Thunbergii Flos (FTF) included in the Chinese Pharmacopoeia (1977 Edition) is a Chinese medicinal herb traditionally used to treat bronchitis. In recent years, it has been applied in the treatment of lung cancer. However, the molecular mechanism remains largely unknown. MethodsThe screening of bioactive compounds, acquisition of drug targets, network construction, and experimental validation in vivo were combined to explored the mechanism of FTF in the treatment of lung carcinoma with regards to systems pharmacology. ResultsThe network Lung Cancer Pathway consisted of 114 nodes (44 compounds and 70 potential targets) and 361 edges, as well as modules that included inflammatory response, angiogenesis, negative regulation of the apoptotic process, and positive regulation of cell proliferation and migration. It was examined by conducting experiments that involved the administration of ethanol-based extracts of FTF in Lewis lung carcinoma mice. The extracts exerted excellent anti-lung cancer effects in vivo by significantly inhibiting tumor proliferation, thereby extending the survival period of tumor-bearing mice. Moreover, FTF induced the downregulation of PIK3CG, Bcl-2, eNOS, VEGF, p-STAT3, and STAT3 genes in tumor-bearing mice. ConclusionsThe findings of the present study verify the therapeutic effects and mechanism of FTF on lung cancer and provide a theoretical basis to support the comprehensive utilization of FTF resources.

Immunological evaluation of a novel HLA-A2 restricted phosphopeptide of tumor associated Antigen, TRAP1, on cancer therapy

The tumor necrosis factor receptor associated protein 1 (TRAP1) is a mitochondria chaperon protein that has been previously implicated as a target for cancer therapy due to its expression level is linked to tumor progression. In this study, an immunodominant phosphopeptide of TRAP1 was identified from an HLA-A2 gene transfected mouse cancer cell line using mass spectrometry, and a synthetic phosphopeptide was generated to evaluate the potency on cancer immunotherapy. In the transporter associated with antigen processing (TAP) deficient cell, the conjugated phosphate group plays a critical role to enhance the binding affinity of phosphopeptide with HLA-A2 molecule. On the basis of immunological assay, immunization of synthetic phosphopeptide could induce a high frequency of IFN-γ-secreting CD8+ T cells in HLA-A2 transgenic mice, and the stimulated cytotoxic T lymphocytes showed a high target specificity to lysis the epitope-pulsed splenocytes in vivo and the human lung cancer cell in vitro. In a tumor challenge assay, vaccination of the HLA-A2 restricted phosphopeptide appeared to suppress the tumor growth and prolong the survival period of tumor-bearing mice. These results suggest that novel phosphopeptide is naturally presented as a HLA-A2-restricted CTL epitope and capable of being a potential candidate for the development of therapeutic vaccine against high TRAP1-expressing cancers.

L-Borneol induces transient opening of the blood-brain barrier and enhances the therapeutic effect of cisplatin.

The blood-brain barrier (BBB) protects the central nervous system from external insults by limiting substance diffusion through the endothelial interface. The presence of the BBB makes drug delivery in neurological disorders very challenging. Cisplatin has been shown to be cytotoxic to glioma cells, but substantial limitations exist in its clinical applications due to difficulties in penetration across the BBB. Here, we show that L-borneol, a messenger drug widely used in traditional Chinese medicine, can induce transient disruption of the BBB after 20 min of oral administration. The permeability of the BBB began to recover within 1 h of the administration of L-borneol. Different dosages of L-borneol (100, 150, 300, 600, and 900 mg/kg) could induce significant Evans blue leakage (P<0.05). Oral administration of L-borneol elevated cisplatin concentrations in peritumoral tissue (1.24±0.12 μg/g) and tumor loci (1.41±0.13 μg/g), compared with those in the paraffin control (0.88±0.10 and 0.92±0.15 μg/g, respectively) (P<0.05). Furthermore, we found that the median survival period of tumor-bearing mice was significantly higher in the cisplatin plus L-borneol group (24.0±4.9 days) than in the cisplatin plus vehicle group (19.3±3.9 days) (P<0.05). The neurological deficits were more severe in the vehicle and cisplatin plus vehicle groups at 14 and 21 days after implantation of intracranial glioma cells than in the cisplatin plus L-borneol group. In conclusion, our results indicate that the transient opening of the BBB induced by L-borneol could enhance cisplatin accumulation within the glioma tissue and improve the survival of tumor-bearing mice.

Antitumor effect and immune response induced by local hyperthermia in B16 murine melanoma: Effect of thermal dose

This study aimed at investigating the antitumor effect and immune response induced by local high-temperature hyperthermia at different thermal doses in B16 murine melanoma. The screened optimal thermal dose (50°C, 15 min) which was demonstrated to be the most effective in immune response activation was applied to the treatment of lung metastasis. The optimal thermal dose was determined by evaluating the tumor volume change, survival period of tumor-bearing mice, and immune indices including interleukin (IL)-2, interferon (IFN)-γ and TNF-α mRNA expression in the spleen of mice subjected to local hyperthermia at various thermal doses. The activation of the immune response was further investigated by rechallenging the cured mice 60 days after hyperthermia treatment. The screened optimal thermal dose combined with immunoadjuvant compound 48/80 was applied for melanoma lung metastasis. While local hyperthermia effectively inhibited B16 melanoma tumor growth and prolonged the survival period of tumor-bearing mice, the antitumor immunity was significantly enhanced and the effect was thermal dose-dependent. Higher temperatures (≥50°C) induced a significant effect even with a short treatment time (≤15 min). No tumor regrowth was observed for rechallenged B16 melanoma in mice following treatment with local hyperthermia at a higher temperature. Local hyperthermia by optimal thermal dose in combination with immunoadjuvant compound 48/80 is an effective approach for the treatment of B16 melanoma lung metastasis. This study indicated that the use of a local high-temperature hyperthermia protocol inhibits tumor growth and stimulates a favorable antitumor immune response against malignant melanoma. The results of these experiments may have clinical significance for the treatment of melanoma.

Establishment of prostate cancer orthotopic transplantation model in C57BL/6 mice

Objective ＂To ＂investigate the regularity in establishing the prostate cancer orthotopic transplantation model in C57BL/6 mice. Methods RM-t cells （0.5×10^6） were injected into the right and left dorsal lateral prostate capsules of 30 C57BL/6 male mice respectively using micro-syringe. Five mice were sacrificed every three days to observe the local growth, the occurrence and development of prostate cancer, and the remaining five mice were fed to death to calculate the average survival period of tumorbearing mice. Results The volume of prostates was significantly different among the five groups. From the 12th day, significant retention of urine, ureterectasia （bilateral or unilateral ） , increased kidney volume and pelvieetasis were observed. The rate of tumor formation in the five groups which included the 3rd, 6th, 9th, 12th d and 15th day was all 100%. HE staining showed that prostate cancer cells gradually replaced the normal prostate tissue. At the 12th day, muscle tissue around prostate was invaded by prostate cancer. In some samples there was metastasis of seminal vesicles and bladder at the 15th day. The rate of metastasis in pelvic lymph nodes at the 12th or 15th day was 80%. The average survival period of tumor-bearing mice was （15.60 ± 0. 89） days. Conclusion The prostate cancer orthotopic transplantation model in C57BL/6 mice can better simulate the process of occurrence, development, local invasion and lymph node metastasis of human prostate cancer and be suitably used as a model of prostate cancer research. Key words: Prostatic neoplasms ; Orthotopic transplantation; Model, animal

Gene transfer of AIMP1 and B7.1 into epitope-loaded, fibroblasts induces tumor-specific CTL immunity, and prolongs the survival period of tumor-bearing mice

T helper type 1 (Th1) cell-mediated immune responses play various roles in cellular immunity, including inducing cytotoxic T lymphocytes (CTLs) and they have been shown to be crucial in cancer immunotherapy. Previously, we found that aminoacyl-tRNA synthetase-interacting multifunctional protein 1 (AIMP1) stimulated antigen-presenting cells to secrete IL-12, leading to enhanced Th1 cell responses. In this study, as a way of enhancing antigen-specific Th1 responses, mouse fibroblasts (H-2 b) were genetically modified to express an AIMP1 and a costimulatory B7.1 (Fb/AIMP1/B7.1). Fb/AIMP1/B7.1 cells were then loaded with an ovalbumin epitope as a model antigen (Fb/AIMP1/B7.1/OVA), and tested to determine if they induced OVA-specific CTLs in C57BL/6 mice (H-2 b). Immunization with Fb/AIMP1/B7.1/OVA cells induced strong cytotoxic activities against OVA-expressing EG7 tumor cells, but not against other H-2 b tumor cells. The levels of the cytotoxic response in the immunized mice with Fb/AIMP1/B7.1/OVA cells were significantly higher than the responses in mice immunized with other cell constructs. CD8 + T cells were a major cell-type of OVA-specific antitumor immunity induced by Fb/AIMP1/B7.1/OVA cells. Furthermore, treatment with Fb/AIMP1/B7.1/OVA cells significantly prolonged the survival period of EG7 tumor-bearing mice. These results indicate that AIMP1-secreting, epitope-loaded fibroblasts efficiently induce antigen-specific CTL responses in mice.

Induction of potent anti-tumor immunity by direct injection of Ad-LIGHT at the site of tumor inoculation

The aim of this study was to observe the therapeutic effects of adenovirus-mediated LIGHT gene transfer in murine B16 melanoma in vivo. C57BL/6 mice were inoculated subcutaneously with B16 cells to establish the murine melanoma model. The tumor-bearing mice were injected at the site of tumor inoculation with recombinant adenoviral vectors expressing the murine LIGHT gene. The tumor growth and survival period of tumor-bearing mice were observed. The splenic NK and CTL activity were measured in vitro by lactate dehydrogenase (LDH) release assay. The amounts of cytokines were determined with ELISA kits. The LIGHT gene could be efficiently transduced into tumor tissue after injection of Ad-LIGHT. Treatment with Ad-LIGHT significantly inhibited the tumor growth and prolonged the survival period of the tumor-bearing mice. The splenic NK and CTL activity of the mice was also enhanced after LIGHT gene transfer. The production of IL-2 and IFN-gamma from lymphocytes derived from mice treated with Ad-LIGHT was increased significantly compared with control groups. Our results indicate that local expression of the LIGHT gene can induce potent anti-tumor immunity and may be a promising treatment strategy for melanoma.

Antigen-specific cytotoxicity and cell number of adoptively transferred T cells are efficiently maintained in vivo by re-stimulation with an antigen/interleukin-2 fusion protein.

In order to maintain in vivo anti-tumor efficacy of antigen (Ag)-specific T cells in adoptive immunotherapy for a prolonged period, we constructed a fusion protein (OVA/IL-2) containing ovalbumin (OVA) as a model tumor Ag, co-valently linked to murine interleukin-2 (IL-2). The OVA/IL-2 protein produced in a baculovirus expression system displayed potent IL-2 bio-activity. Immunization with the OVA/IL-2 protein after adoptive transfer of OVA-specific T cells maintained the OVA-specific cytotoxicity and cell number of adoptively transferred T cells long term in vivo, while a simple mixture of recombinant OVA (rOVA) and rIL-2 did not. The response was dependent on the injection doses and times of the OVA/IL-2 protein. Furthermore, weekly re-stimulation of adoptively transferred OVA-specific T cells with the OVA/IL-2 protein cured 70% of tumor-bearing mice. In contrast, re-stimulation with a mixture of rOVA and rIL-2 could not significantly prolong the survival period of tumor-bearing mice. These studies suggest that the co-valent linkage between IL-2 and antigen confines the effect of IL-2 to antigen-specific T cells, leading to efficient maintenance of the anti-tumor activity of adoptively transferred T cells.

Antitumor effect of granulocyte-macrophage colony-stimulating factor (GM-CSF)-gene encoded vaccinia melanoma oncolysate and its immunological mechanisms

Vaccinia melanoma oncolysate (VMO) prepared by infecting B16F10 melanoma cells with recombinant vaccinia virus encoding murine GM-CSF gene was tested for its therapeutic effect on the preestablished melanoma. C57BL/6 mice were inoculated s.c. with 1 × l0 5 B16F10 melanoma cells and received s.c. administration with VMO prepared with GM-CSF gene-encoded vaccinia virus(GM-CSFVMO), VMO prepared with thymidine kinase gene-deficient vaccinia virus(TKVMO), B16F10 melanoma oncolysate(BMO), or PBS 3 days after tumor inoculation. The same treatment was bolstered one week later. The results demonstrated that GM-CSFVMO treatment significantly inhibited the growth of subcutaneous tumor and prolonged the survival period of tumor-bearing mice. Further study elucidated that cytotoxicity of PBL and splenocytes towards B16F10 increased obviously after treatment with GM-CSFVMO, but NK activity remained unchanged. These results suggest that the tumor oncolysate vaccine prepared with GM-CSF gene-encoded vaceinia virus might exert potent therapeutic effect on the preestablished tumor through the efficient induction of specific antitumor immune response of the host.

Survival period of tumor-bearing mice is prolonged after the interferon-γ-producing gene transfer

A highly tumorigenic keratinocyte-derived carcinoma cell line, designated as Pam-T, was established from a Pam212 line. The intradermal injection of more than 10 5 of these cells into syngeneic BALB c mice induced substantial tumors. The tumors progressively enlarged and then invaded the peritoneal cavity leading to the death of the host mice. To comprehensively investigate the effects of interferon-γ on tumorigenicity, we manufactured interferon-γ-producing PamT cells by interferon-γ gene transfer and examined the characteristics of the tumors induced by these cells in syngeneic mice. Interferon-γ producing cells exhibited an apparently similar in vitro cell growth pattern and in vivo tumor formation to control cells, but the mean survival of the mice with the interferon-γ-producing cells was significantly longer compared with control mice.