Minimally Invasive Establishment of Murine Orthotopic Bladder Xenografts

Orthotopic bladder cancer xenografts are the gold standard to study molecular cellular manipulations and new therapeutic agents in vivo. Suitable cell lines are inoculated either by intravesical instillation (model of nonmuscle invasive growth) or intramural injection into the bladder wall (model of invasive growth). Both procedures are complex and highly time-consuming. Additionally, the superficial model has its shortcomings due to the lack of cell lines that are tumorigenic following instillation. Intramural injection, on the other hand, is marred by the invasiveness of the procedure and the associated morbidity for the host mouse.With these shortcomings in mind, we modified previous methods to develop a minimally invasive approach for creating orthotopic bladder cancer xenografts. Using ultrasound guidance we have successfully performed percutaneous inoculation of the bladder cancer cell lines UM-UC1, UM-UC3 and UM-UC13 into 50 athymic nude. We have been able to demonstrate that this approach is time efficient, precise and safe. With this technique, initially a space is created under the bladder mucosa with PBS, and tumor cells are then injected into this space in a second step. Tumor growth is monitored at regular intervals with bioluminescence imaging and ultrasound. The average tumor volumes increased steadily in in all but one of our 50 mice over the study period.In our institution, this novel approach, which allows bladder cancer xenograft inoculation in a minimally-invasive, rapid and highly precise way, has replaced the traditional model.     

Combining mTOR Inhibition with Radiation Improves Antitumor Activity in Bladder Cancer Cells In Vitro and In Vivo: A Novel Strategy for Treatment

Purpose

Radiation therapy for invasive bladder cancer allows for organ preservation but toxicity and local control remain problematic. As such, improving efficacy of treatment requires radiosensitization of tumor cells. The aim of study is to investigate if the mammalian Target of Rapamycin (mTOR), a downstream kinase of the phosphatidylinositol 3-kinase (PI3K)/AKT survival pathway, may be a target for radiation sensitization.

Experimental Design

Clonogenic assays were performed using 6 bladder cancer cell lines (UM-UC3, UM-UC5, UM-UC6, KU7, 253J-BV, and 253-JP) in order to examine the effects of ionizing radiation (IR) alone and in combination with RAD001, an mTOR inhibitor. Cell cycle analysis was performed using flow cytometry. In vivo, athymic mice were subcutaneously injected with 2 bladder cancer cell lines. Treatment response with RAD001 (1.5 mg/kg, daily), fractionated IR (total 9Gy = 3Gy×3), and combination of RAD001 and IR was followed over 4 weeks. Tumor weight was measured at experimental endpoint.

Results

Clonogenic assays revealed that in all bladder cell lines tested, an additive effect was observed in the combined treatment when compared to either treatment alone. Our data indicates that this effect is due to arrest in both G1 and G2 phases of cell cycle when treatments are combined. Furthermore, our data show that this arrest is primarily regulated by changes in levels of cyclin D1, p27 and p21 following treatments. In vivo, a significant decrease in tumor weight was observed in the combined treatment compared to either treatment alone or control.

Conclusions

Altering cell cycle by inhibiting the mTOR signaling pathway in combination with radiation have favorable outcomes and is a promising therapeutic modality for bladder cancer.     

Inhibition of Inducible Heat Shock Protein-70 (Hsp72) Enhances Bortezomib-Induced Cell Death in Human Bladder Cancer Cells

The proteasome inhibitor bortezomib (Velcade) is a promising new agent for bladder cancer therapy, but inducible cytoprotective mechanisms may limit its potential efficacy. We used whole genome mRNA expression profiling to study the effects of bortezomib on stress-induced gene expression in a panel of human bladder cancer cell lines. Bortezomib induced strong upregulation of the inducible HSP70 isoforms HSPA1A and HSPA1B isoforms of Hsp72 in 253J B-V and SW780 (HSPA1A^high) cells, but only induced the HSPA1B isoform in UM-UC10 and UM-UC13 (HSPA1A^low) cells. Bortezomib stimulated the binding of heat shock factor-1 (HSF1) to the HSPA1A promoter in 253JB-V but not in UM-UC13 cells. Methylation-specific PCR revealed that the HSPA1A promoter was methylated in the HSPA1A^low cell lines (UM-UC10 and UM-UC13), and exposure to the chromatin demethylating agent 5-aza-2′-deoxycytidine restored HSPA1A expression. Overexpression of Hsp72 promoted bortezomib resistance in the UM-UC10 and UM-UC13 cells, whereas transient knockdown of HSPA1B further sensitized these cells to bortezomib, and exposure to the chemical HSF1 inhibitor KNK-437 promoted bortezomib sensitivity in the 253J B-V cells. Finally, shRNA-mediated stable knockdown of Hsp72 in 253J B–V promoted sensitivity to bortezomib in vitro and in tumor xenografts in vivo. Together, our results provide proof-of-concept for using Hsp72 inhibitors to promote bortezomib sensitivity in bladder cancers and suggest that selective targeting of HSPA1B could produce synthetic lethality in tumors that display HSPA1A promoter methylation.     

Development of an orthotopic human pancreatic cancer xenograft model using ultrasound guided injection of cells

Mice have been employed as models of cancer for over a century, providing significant advances in our understanding of this multifaceted family of diseases. In particular, orthotopic tumor xenograft mouse models are emerging as the preference for cancer research due to increased clinical relevance over subcutaneous mouse models. In the current study, we developed orthotopic pancreatic cancer xenograft models in mice by a minimally invasive method, ultrasound guided injection (USGI) comparable to highly invasive surgical orthotopic injection (SOI) methods. This optimized method prevented injection complications such as recoil of cells through the injection canal or leakage of cells out of the pancreas into the peritoneal cavity. Tumor growth was monitored in vivo and quantified by ultrasound imaging weekly, tumors were also detected by in vivo fluorescence imaging using a tumor targeted molecular probe. The mean tumor volumes for the USGI and SOI models after 2 weeks of tumor growth were 205 mm(3) and 178 mm(3) respectively. By USGI of human pancreatic cancer cell lines, human orthotopic pancreatic cancer xenografts were established. Based on ultrasound imaging, the orthotopic human pancreatic cancer xenograft take rate was 100% for both human pancreatic cancer cell lines used, MiaPaCa-2 and Su86.86, with mean tumor volumes of 28 mm(3)and 30 mm(3). We demonstrated that this USGI method is feasible, reproducible, facile, minimally invasive and improved compared to the highly-invasive SOI method for establishing orthotopic pancreatic tumor xenograft models suitable for molecular imaging.     

Systemic perfusion: a method of enhancing relative tumor uptake of radiolabeled monoclonal antibodies

We evaluated the feasibility of systemic vascular perfusion with saline (mimicking plasmapheresis) as a method to enhance tumor-specific monoclonal antibody (MoAb) tumor/background ratios. Initially, groups of rats were injected intravenously (i.v.) with ¹³¹I-5G6.4 MoAb (murine IgG2aK reactive with ovarian carcinoma). These animal's radioactivity levels were determined by dose calibrator and they were imaged before and after perfusion which was conducted at 4 or 24 h post-antibody injection. Animals were sacrificed after perfusion, as were controls, and normal organ radioactivity levels determined. In addition, nude mice bearing HTB77 ovarian cancers subcutaneously were injected i.v. with ¹³¹I-5G6.4 MoAb and were imaged before and after systemic perfusion with saline 24 h post-5G6.4 injection. Perfusion in rats dropped whole-body 5G6.4 levels significantly at both perfusion times (P < 0.0005). The drop in whole-body radioactivity with perfusion was significantly greater for the animals perfused at 4 h post i.v. 5G6.4 antibody injection (48.3 ± 5.1%) than for those perfused at 24 h post i.v. antibody injection (32.9 ± 2.9%) (P < 0.025). In the nude mice with ovarian cancer xenografts, γ camera images of tumors were visually and quantitatively (by computer image analysis) enhanced by perfusion, with a 2.33-fold greater decline in whole body uptake than in the tumor (P < 0.05). These studies show that (1) much background antibody radioactivity can be removed using whole-body perfusion with saline, (2) that the decline in whole body activity is larger with 4 than 24 h perfusion and (3) tumor imaging can be enhanced by this approach. This and similar approaches that increase relative tumor antibody uptake such as plasmapheresis may be useful in imaging and therapy with radiolabeled antibodies.     

Local regulation of human breast xenograft models

Breast cancer studies implant human cancer cells under the renal capsule, subcutaneously, or orthotopically and often use estrogen supplementation and immune suppressants (etoposide) in xenograft mouse models. However, cell behavior is significantly impacted by signals from the local microenvironment. Therefore, we investigated how the combinatorial effect of the location of injection and procedural differences affected xenograft characteristics. Patient‐derived breast cancer cells were injected into mouse abdominal or thoracic mammary glands ± estrogen and/or etoposide pretreatment. Abdominal xenografts had increased tumor incidence and volume, and decreased latency (P < 0.001) compared to thoracic tumors. No statistically significant difference in tumor volume was found in abdominal xenografts treated ± estrogen or etoposide; however, etoposide suppressed tumor volume in thoracic xenografts (P < 0.02). The combination of estrogen and etoposide significantly decreased tumor incidence in both sites. In addition, mice treated ± estradiol were injected orthotopically or subcutaneously with well‐characterized breast cancer cell lines (MCF7, ZR75‐1, MDA MB‐231, or MCF10Ca1h). Orthotopic injection increased tumor volume; growth varied with estrogen supplementation. Location also altered methylation status of several breast cancer‐related gene promoters. Lastly, vascularization of orthotopic tumors was significantly enhanced compared to subcutaneous tumors. These data suggest that optimal xenograft success occurs with orthotopic abdominal injections and illustrate molecular details of the compelling influence of the local microenvironment on in vivo models. J. Cell. Physiol. 224: 795–806, 2010. Published 2010 Wiley‐Liss, Inc.     

Targeting bladder tumor cells in vivo and in the urine with a peptide identified by phage display

Bladder cancer is one of the most common tumors of the genitourinary tract. Here, we use phage display to identify a peptide that targets bladder tumor cells. A phage library containing random peptides was screened for binding to cells from human bladder tumor xenografts. Phage clones were further selected for binding to a bladder tumor cell line in culture. Six clones displaying the consensus sequence CXNXDXR(X)/(R)C showed selective binding to cells from primary human bladder cancer tissue. Of these, the CSNRDARRC sequence was selected for further study as a synthetic peptide. Fluorescein-conjugated CSNRDARRC peptide selectively bound to frozen sections of human bladder tumor tissue, whereas only negligible binding to normal bladder tissue was observed. When the fluorescent peptide was introduced into the bladder lumen, in a carcinogen-induced rat tumor model, it selectively bound to tumor epithelium. Moreover, when the peptide was intravenously injected into the tail vein, it homed to the bladder tumor but was not detectable in normal bladder and control organs. Next, we examined whether the peptide can detect tumor cells in urine. The fluorescent peptide bound to cultured bladder tumor cells but not to other types of tumor cell lines. Moreover, it bound to urinary cells of patients with bladder cancer, while showing little binding to urinary cells of patients with inflammation or healthy individuals. The CSNRDARRC peptide may be useful as a targeting moiety for selective delivery of therapeutics and as a diagnostic probe for the detection of bladder cancer.     

Evaluation of the Antitumor Activity of Dacomitinib in Models of Human Bladder Cancer

Members of the human epidermal growth factor receptor (HER) family play a significant role in bladder cancer progression and may underlie the development of chemotherapy resistance. Dacomitinib is an irreversible tyrosine kinase inhibitor with structural specificity for the catalytic domains of epidermal growth factor receptor (EGFR), HER2 and HER4 that has exhibited vigorous efficacy against other solid tumors. We evaluated the antitumor activity of dacomitinib in human bladder cancer cell lines expressing varying levels of HER family receptors. These cell lines also were established as bladder cancer xenografts in nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mice to assess dacomitinib activity in vivo. Significant cytotoxic and cytostatic effects were noted in cells expressing elevated levels of the dacomitinib target receptors with apoptosis and cell cycle arrest being the predominant mechanisms of antitumor activity. Cells expressing lower levels of HER receptors were much less sensitive to dacomitinib. Interestingly, dacomitinib was more active than either trastuzumab or cetuximab in vitro, and exhibited increased growth inhibition of bladder tumor xenografts compared with lapatinib. Pharmacodynamic effects of dacomitinib included decreased E-cadherin (E-cad) expression, reduction of EGFR and extracellular signal-regulated kinase (ERK) phosphorylation and reduced mitotic count. Dacomitinib also inhibited tumor growth in a chemotherapy-resistant xenograft and, when combined with chemotherapy in a sensitive xenograft, exhibited superior antitumor effects compared with individual treatments. Evaluation in xenograft-bearing mice revealed that this combination was broadly feasible and well tolerated. In conclusion, dacomitinib exhibited pronounced activity both as a single agent and when combined with chemotherapy in human bladder cancer models. Further investigation of dacomitinib in the preclinical and clinical trial settings is being pursued.     

Construction of a BALB/c-Nu Mouse Model of Invasive Bladder Carcinoma and Preliminary Studies on the Treatment of Bladder Tumors through Internal Iliac Arterial Infusion of Albumin-Bound Arsenic Trioxide (As2O3)

To establish a BALB/c-nu mouse model of invasive bladder carcinoma and to investigate the feasibility, efficacy, and side effects of treating the mouse xenografts with internal iliac arterial infusion of albumin-bound arsenic trioxide (As₂O₃). Bladder tumors were established by intravesicular injection. Color Doppler were used to monitor tumor growth. Albumin-bound As₂O₃ and bovine serum albumin (BSA) nanoparticles were synthesized by cross-linking. BALB/c-nu mice were randomly divided into four treatment groups: 1) normal saline, 2) BSA nanoparticles, 3) As₂O₃ injections, and 4) albumin-bound As₂O₃. In an attempt to replicate the treatment of bladder cancer in humans using internal iliac arterial infusion, the drugs were injected into the mouse abdominal aorta. Tumor xenografts were established successfully. Mice treated with As₂O₃ injections and with albumin-bound As₂O₃ had significantly smaller bladders (36.59% and 37.82% smaller, respectively) than mice given normal saline injections (P < 0.01). Mice receiving As₂O₃ injections had lower white blood cell (WBC) and platelet counts compared with mice receiving normal saline injections only (P < 0.05). However, mice treated with albumin-bound As₂O₃ did not experience a significant decrease in WBC or platelet counts compared with control mice. A model of intra-arterial bladder cancer treatment was successfully established in BALB/c-nu mice. In this model, albumin-bound As₂O₃ appeared to be an effective method for treating bladder tumors, with less severe hematologic side effects compared with As₂O₃ alone. The infusion of albumin-bound As₂O₃ through the internal iliac artery is a promising method of bladder cancer therapy.     

Anticancer effects of a plant lignan 7-hydroxymatairesinol on a prostate cancer model in vivo

Clinical intervention studies and experimental studies with lignan-rich diets suggest that lignans may have inhibitory effects on prostate cancer, but no clinical or experimental studies with purified lignans have been published. The purpose of this study was to investigate the effect of a plant lignan 7-hydroxymatairesinol (HMR) on LNCaP human prostate cancer xenografts in athymic mice. Athymic nude male mice were injected subcutaneously with LNCaP cells. Starting 3 days after tumor cell injections, a control diet or a control diet supplemented with 0.15% or 0.30% of HMR was administered to mice and the tumor take rate and growth was observed for 9 weeks. HMR diet inhibited the growth of LNCaP tumors. Mice treated with HMR had smaller tumor volume, lower tumor take rate, increased proportion of nongrowing tumors, and higher tumor cell apoptotic index compared with controls. Furthermore, the cell proliferation index was reduced in mice receiving the 0.30% HMR diet compared with mice receiving the control diet. Our results suggest that dietary HMR started at the early phase of the tumor development inhibits the growth of the LNCaP human prostate cancer xenografts in athymic male mice.     

藏红花素对人膀胱移行细胞癌T24细胞裸鼠移植瘤的实验研究

目的检测藏红花素（crocin）对人膀胱移行细胞癌T24细胞株裸鼠移植瘤的作用。方法12只裸鼠右后腿背侧皮下接种T24移植瘤细胞后随机分为PBS对照组（6只）和50mmol/L藏红花素治疗组（6只）。从接种后第28d开始,每3d一次于肿瘤局部注射给予PBS或藏红花素,每3d测量1次肿瘤大小,并绘制移植瘤生长曲线;处理后第21d杀鼠摘取移植瘤,光镜、电镜观察肿瘤组织形态改变;RT-PCR检测Bcl-2、Bax mRNA表达;SP-免疫组织化学法分析sur-vivin、cyclinD1蛋白表达。结果藏红花素对人膀胱癌T24细胞裸鼠移植瘤的生长具有抑制作用,抑制率达28.7%。HE染色结果显示肿瘤标本内出现片状坏死灶;电镜观察可见凋亡的形态学改变;RT-PCR检测结果显示Bcl-2的表达水平下降,而Bax的表达水平上调;免疫组化结果显示经藏红花素处理后survivin、CyclinD1的表达下调。结论藏红花素能够抑制人膀胱癌T24细胞裸鼠移植瘤的生长,作用的分子机制与下调Bcl-2、survivin、cyclinD1和上调Bax基因表达有关。     

Orthotopic mouse model of colorectal cancer

The traditional subcutaneous tumor model is less than ideal for studying colorectal cancer. Orthotopic mouse models of colorectal cancer, which feature cancer cells growing in their natural location, replicate human disease with high fidelity. Two techniques can be used to establish this model. Both techniques are similar and require mouse anesthesia and laparotomy for exposure of the cecum. One technique involves injection of a colorectal cancer cell suspension into the cecal wall. Cancer cells are first grown in culture, harvested when subconfluent and prepared as a single cell suspension. A small volume of cells is injected slowly to avoid leakage. The other technique involves transplantation of a piece of subcutaneous tumor onto the cecum. A mouse with a previously established subcutaneous colorectal tumor is euthanized and the tumor is removed using sterile technique. The tumor piece is divided into small pieces for transplantation to another mouse. Prior to transplantation, the cecal wall is lightly damaged to facilitate tumor cell infiltration. The time to developing primary tumors and liver metastases will vary depending on the technique, cell line, and mouse species used. This orthotopic mouse model is useful for studying the natural progression of colorectal cancer and testing new therapeutic agents against colorectal cancer.     

Factors influencing phenotypic diversity of human prostate carcinoma cells metastasizing in athymic nude mice

Three related human prostate carcinoma cell lines, PC-3, 1-LN-PC-3-1A (1-LN), and 1-LN-PC-3-1A clone 4 (clone 4) were compared in terms of relative metastatic capacity in adult and young male nude mice. Only 1-LN produced lung metastases after intravenous injection into both 6- to 8-week-old and 4-week-old nude mice, as well as in mice injected intraperitoneally. The extent of the phenotypic diversity exhibited by these human prostate tumor lines was influenced by inherent dissemination ability, age of the host, and route of injection. These lines provide a useful system for the analysis of the biology of human tumor metastasis in nude mice.     

Preclinical models for neuroblastoma: establishing a baseline for treatment

Background

Preclinical models of pediatric cancers are essential for testing new chemotherapeutic combinations for clinical trials. The most widely used genetic model for preclinical testing of neuroblastoma is the TH-MYCN mouse. This neuroblastoma-prone mouse recapitulates many of the features of human neuroblastoma. Limitations of this model include the low frequency of bone marrow metastasis, the lack of information on whether the gene expression patterns in this system parallels human neuroblastomas, the relatively slow rate of tumor formation and variability in tumor penetrance on different genetic backgrounds. As an alternative, preclinical studies are frequently performed using human cell lines xenografted into immunocompromised mice, either as flank implant or orthtotopically. Drawbacks of this system include the use of cell lines that have been in culture for years, the inappropriate microenvironment of the flank or difficult, time consuming surgery for orthotopic transplants and the absence of an intact immune system.

Principal Findings

Here we characterize and optimize both systems to increase their utility for preclinical studies. We show that TH-MYCN mice develop tumors in the paraspinal ganglia, but not in the adrenal, with cellular and gene expression patterns similar to human NB. In addition, we present a new ultrasound guided, minimally invasive orthotopic xenograft method. This injection technique is rapid, provides accurate targeting of the injected cells and leads to efficient engraftment. We also demonstrate that tumors can be detected, monitored and quantified prior to visualization using ultrasound, MRI and bioluminescence. Finally we develop and test a “standard of care” chemotherapy regimen. This protocol, which is based on current treatments for neuroblastoma, provides a baseline for comparison of new therapeutic agents.

Significance

The studies suggest that use of both the TH-NMYC model of neuroblastoma and the orthotopic xenograft model provide the optimal combination for testing new chemotherapies for this devastating childhood cancer.     

Promoter methylation in head and neck squamous cell carcinoma cell lines is significantly different than methylation in primary tumors and xenografts

Studies designed to identify novel methylation events related to cancer often employ cancer cell lines in the discovery phase of the experiments and have a relatively low rate of discovery of cancer-related methylation events. An alternative algorithm for discovery of novel methylation in cancer uses primary tumor-derived xenografts instead of cell lines as the primary source of nucleic acid for evaluation. We evaluated DNA extracted from primary head and neck squamous cell carcinomas (HNSCC), xenografts grown from these primary tumors in nude mice, HNSCC-derived cell lines, normal oral mucosal samples, and minimally transformed oral keratinocyte-derived cell lines using Illumina Infinum Humanmethylation 27 genome-wide methylation microarrays. We found >2,200 statistically significant methylation differences between cancer cell lines and primary tumors and when comparing normal oral mucosa to keratinocyte cell lines. We found no statistically significant promoter methylation differences between primary tumor xenografts and primary tumors. This study demonstrates that tumor-derived xenografts are highly accurate representations of promoter methylation in primary tumors and that cancer derived cell lines have significant drawbacks for discovery of promoter methylation alterations in primary tumors. These findings also support use of primary tumor xenografts for the study of methylation in cancer, drug discovery, and the development of personalized cancer treatments.     

Near-infrared optical imaging of ovarian cancer xenografts with novel alpha 3-integrin binding peptide "OA02"

Through screening of random one-bead one-compound (OBOC) libraries, we previously identified cyclic peptides with the cDGXGXXc motif that bind to alpha3 integrin subunit on ovarian adenocarcinoma cell lines ES-2, SKOV-3, and CaOV-3. We subsequently synthesized two secondary libraries based on this motif and identified new peptides that bound with a higher affinity to these cell lines. One of the peptides identified from the 20% "down-substituted" focused library was the c-dGHCitGPQ-c ("OA02") peptide. The goal of this study was to determine whether this peptide labeled with near-infrared probes could be detected after intravenous injection in ovarian tumor-bearing mice and if it would selectively localize in the tumor. Three different forms of this peptide were synthesized, "OA02"-biotin (noncovalently linked to streptavidin-Cy5.5); "OA02"-Cy5.5 and "OA02"-AlexaFluo 680. Using a KODAK IS2000MM image station, these peptide probes were used at the near-infrared (NIR) spectra to image nude mice bearing ES-2 (alpha3 integrin positive) and Raji (alpha3 integrin negative) xenografts. The peptide probe displayed highly specific tumor uptake within 15 min, which lasted for 70 min for "OA02"-Cy5.5 and "OA02"-AlexaFluo 680 and for 24 hours for "OA02"-biotin-streptavidin-Cy5.5. Some kidney and bladder signal were noted. Prior injection with anti-alpha3 monoclonal antibody blocked the binding of this peptide to the ES-2 tumors.     

Establishment of a Chinese bladder cancer cell line (T921) with high metastatic activity

Muscle-invasive bladder cancer is prone to metastasis without a standard organ preference. The current cell lines used to study bladder cancer have primarily been derived from individuals in Western populations, and no human bladder cancer cell line has been established from the Chinese population. A bladder cancer cell line was derived from a female Chinese patient with muscle-invasive bladder cancer, and these cells were then xenografted into the bladders of three nude mice. Five weeks later, these mice were killed to observe local invasion and distant metastasis. The metastatic tumors were also removed and analyzed to assess the metastatic mechanism. This bladder cancer cell line, named T921, was successfully established, as evidenced by karyotype and immunohistochemistry analyses. Multi-organ metastases were observed in all three of the nude mice 5 wk after the orthotopic transfer of the cell line. In addition, epithelial–mesenchymal transition (EMT)-related genes were involved in the tumor metastases. The T921 bladder cancer cell line was successfully established, and EMT was observed to play a role in bladder cancer metastasis.     

Establishment of a rabbit model of superior vena cava obstruction.

OBJECTIVE: To explore a method of establishing a rabbit model of superior vena cava obstruction (SVCO) by injecting VX2 tumor cell suspension transcutaneously under ultrasound guidance. METHODS: A suspension of VX2 tumor cells was prepared under sterile conditions. Fifteen adult healthy New Zealand White rabbits were enrolled in the experiment. Under ultrasound guidance, about 0.1 ml of the living tumor cell suspension was transcutaneously injected in front of the anterior wall of the right superior vena cava (SVC). The lumen, wall, blood flow of SVCs and adjacent tissues were examined with gray-scale and color Doppler ultrasonography, every 3 days starting from the 9th day after injection. Meanwhile, CT scanning and digital subtraction angiography (DSA) were also performed. The rabbits were dissected immediately after death and tissue samples were collected for pathologic examination. RESULTS: Fourteen out of 15 rabbits developed tumors that were located close to SVCs and/or SVCs cavity, which was shown by ultrasonography. The diameters of the tumors were 80.7 +/- 4.3 mm. These tumors grew close to SVCs area and resulted in compression and infiltration of SVCs. CT scanning and DSA confirmed the establishment of the SVCO model. The achievement rate of the SVCO model was 93.3%. No rabbit died of complications. CONCLUSION: A method of establishing a rabbit SVCO model by injecting VX2 tumor cell suspension under ultrasonographic guidance was established successfully, and it proved to be simple, effective and repeatable. The imaging characteristics of this model are in good accordance with those of SVCO in patients.     

Intratumoral peptide injection enhances tumor cell antigenicity recognized by cytotoxic T lymphocytes: a potential option for improvement in antigen-specific cancer immunotherapy

Antigen-specific cancer immunotherapy is a promising strategy for improving cancer treatment. Recently, many tumor-associated antigens and their epitopes recognized by cytotoxic T lymphocytes (CTLs) have been identified. However, the density of endogenously presented antigen-derived peptides on tumor cells is generally sparse, resulting in the inability of antigen-specific CTLs to work effectively. We hypothesize that increasing the density of an antigen-derived peptide would enhance antigen-specific cancer immunotherapy. Here, we demonstrated that intratumoral peptide injection leads to additional peptide loading onto major histocompatibility complex class I molecules of tumor cells, enhancing tumor cell recognition by antigen-specific CTLs. In in vitro studies, human leukocyte antigen (HLA)-A*02:01-restricted glypican-3_144–152 (FVGEFFTDV) and cytomegalovirus_495–503 (NLVPMVATV) peptide-specific CTLs showed strong activity against all peptide-pulsed cell lines, regardless of whether the tumor cells expressed the antigen. In in vivo studies using immunodeficient mice, glypican-3_144–152 and cytomegalovirus_495–503 peptides injected into a solid mass were loaded onto HLA class I molecules of tumor cells. In a peptide vaccine model and an adoptive cell transfer model using C57BL/6 mice, intratumoral injection of ovalbumin_257–264 peptide (SIINFEKL) was effective for tumor growth inhibition and survival against ovalbumin-negative tumors without adverse reactions. Moreover, we demonstrated an antigen-spreading effect that occurred after intratumoral peptide injection. Intratumoral peptide injection enhances tumor cell antigenicity and may be a useful option for improvement in antigen-specific cancer immunotherapy against solid tumors.