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Method Article
This protocol describes the generation of murine orthotopic bladder tumors in female C57BL/6J mice and the monitoring of tumor growth.
This protocol describes the generation of bladder tumors in female C57BL/6J mice using the murine bladder cancer cell line MB49, which has been modified to secrete human Prostate Specific Antigen (PSA), and the procedure for the confirmation of tumor implantation. In brief, mice are anesthetized using injectable drugs and are made to lay in the dorsal position. Urine is vacated from the bladder and 50 µL of poly-L-lysine (PLL) is slowly instilled at a rate of 10 µL/20 s using a 24 G IV catheter. It is left in the bladder for 20 min by stoppering the catheter. The catheter is removed and PLL is vacated by gentle pressure on the bladder. This is followed by instillation of the murine bladder cancer cell line (1 x 105 cells/50 µL) at a rate of 10 µL/20 s. The catheter is stoppered to prevent premature evacuation. After 1 h, the mice are revived with a reversal drug, and the bladder is vacated. The slow instillation rate is important, as it reduces vesico-ureteral reflux, which can cause tumors to occur in the upper urinary tract and in the kidneys. The cell line should be well re-suspended to reduce clumping of cells, as this can lead to uneven tumor sizes after implantation.
This technique induces tumors with high efficiency. Tumor growth is monitored by urinary PSA secretion. PSA marker monitoring is more reliable than ultrasound or fluorescence imaging for the detection of the presence of tumors in the bladder. Tumors in mice generally reach a maximum size that negatively impacts health by about 3 - 4 weeks if left untreated. By monitoring tumor growth, it is possible to differentiate mice that were cured from those that were not successfully implanted with tumors. With only end-point analysis, the latter may be mistakenly assumed to have been cured by therapy.
The goal of this method is to generate murine orthotopic bladder tumors and to monitor the implanted tumors as accurately as possible, so that mice without tumor implantation are not thought to have been cured at end-point analysis. Overall, the method shown will reduce the need for large numbers of mice for experimental analysis and ensure greater accuracy in determining therapeutic outcomes.
The development of an orthotopic model for cancer is important, as implanting tumor cells subcutaneously does not recapitulate the environment of the clinical disease or enable the development of therapeutic strategies. The architecture of the bladder permits the instillation of bladder cancer therapies directly into the bladder with minimal systemic effects. Thus, animal models that recapitulate this environment, such as an orthotopic model, are important to evaluate new therapies. The conclusions drawn from any experimental set-up are dependent upon the limitations of the model.
Several techniques have been developed for the production of orthotopic bladder tumors in mice. These rely on damaging the glycosaminoglycan layer of the bladder, enabling tumor cells to be implanted. The techniques used include electrocautery, which results in a single point of damage in the bladder wall, leading to tumor development at one site in the bladder1,2. However, the success rate of tumor implantation using electrocautery is operator-dependent varying from 10 - 90%, and it includes the danger that the bladder wall will be punctured, leading to tumors developing in the peritoneal cavity. Chemical cautery is performed using silver nitrate, which damages the bladder wall3. Similarly, acid has been used to damage the bladder wall4. Trypsin has also been used to damage the bladder as well5. These methods may result in the development of more than one tumor in the bladder. Furthermore, there is a danger of severe damage to the bladder if the chemicals are left in contact with the bladder wall for too long. The method developed by Ninalga et al. uses the positively charged poly-L-lysine (PLL)6 molecules to coat the bladder wall; this enables the negatively charged tumor cells to stick to the glycosaminoglycan layer of the bladder. This method generally results in more than one tumor developing in the bladder, but tumor implantation is at 80 - 100%4,7. Technically, it is also the easiest procedure to perform. To ensure that the tumors that develop are fairly even in size, it is important that the tumor cells are not grouped in large clumps before implantation.
In order to evaluate therapeutic efficacy, it is best to perform this study on mice with fairly similar-sized tumors. Thus, a good detection system that can quantify tumor size soon after implantation is important. Several strategies have been used to evaluate tumors. These include magnetic resonance imaging (MRI)8-10, fluorescence11, bioluminescence12,13, ultrasound14, and enzyme-linked immunosorbent assay (ELISA)15,16. While MRI and ultrasound do not require modifications of the tumor cells, there is a need for sensitive equipment and contrast agents for MRI. The fluorescence-, luminescence-, and ELISA-based assays require modification of the tumor cells to express marker proteins that can be detected by these methods. For luminescence, a substrate is required for the detection of the luciferase activity; thus, there is an added step and increased cost. Both luminescence and fluorescence require specialized equipment. To produce fluorescence, green fluorescent protein (GFP) cyclization, which is catalyzed by molecular oxygen, is required. Thus, GFP expression may be variable within a tumor mass depending on access to oxygen, making this a rather unreliable marker17. Modification of the murine bladder cancer cell line MB49 to secrete human Prostate Specific Antigen (PSA)15,16 as a surrogate marker is another strategy. These markers also provide an alternative means of confirming tumor presence at the termination of the experiment, making them an alternative to immunohistochemistry. This study reports the PLL method of orthotopic tumor implantation and presents a comparison of tumor detection systems, namely ELISA, fluorescence, and ultrasound imaging.
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All animal work adhered to the Institutional Animal Care and Use Committee (IACUC) guidelines on animal use and handling (Protocol number 084/12) at the National University of Singapore.
1. Growing MB49-PSA Cells In Vitro and Measuring PSA Secretion
2. Determining the Sensitivity of PSA Measurements by ELISA and Real-time PCR Analysis
3. Maintaining the Tumorigenicity of the MB49-PSA Cell Line
NOTE: Prolonged growth in vitro leads to a loss of tumorigenicity. To maintain tumorigenicity, the MB49-PSA cell line is passaged through the mouse at least once every 2 years.
4. Implanting the Tumor
NOTE: Each mouse is implanted with 1 x 105 MB49-PSA cells in 50 µL of DMEM blank media in the bladder. Due to the dead space in the catheter, always prepare extra volume (at least 100 µL extra per mouse). An alternative approach would be to use an air filled syringe as described by Kasman et al.5 rather than a filled syringe.
5. Monitoring Tumor Growth with ELISA
NOTE: Tumor presence and growth is monitored in mice by measuring PSA secretion in urine. Researchers should consult with their veterinary staff on monitoring animal health and well-being post-tumor implantation and humane endpoints.
6. Detecting Tumor Presence with Real-time PCR
7. Monitoring Tumor Growth with Fluorescence Imaging
8. Monitoring Tumor Growth with High-frequency Ultrasound Imaging
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PSA secretion from MB49 cells was found to vary with the growth media. MB49-PSA is grown in DMEM media because this results in increased PSA secretion (Figure 1A). In order to determine the sensitivity of the PSA ELISA and real-time PCR, different numbers of MB49-PSA-secreting cells were mixed with MB49 parental cells. PSA ELISA detects a minimum of 1 x 105 PSA-secreting cells/1 x 106 cells (Figure 1B), while real-time PCR analysis d...
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The most critical steps in the protocol are 1) successfully maintaining the tumorigenicity of the cell line; 2) ensuring measurable PSA secretion before tumor cell implantation in mice; 3) generating a single-cell suspension for implantation so as to reduce variation in tumor size; and 4) instilling cells at a slow rate to prevent vesico-ureteral reflux, resulting in tumor cell implantation in the kidney.
After prolonged passage in vitro, MB49/MB49-PSA cells can lose their tumorigenic...
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The authors have nothing to disclose.
This work was funded by a grant from the National Medical Research Council of Singapore (NMRC/CIRG/1335/2012) awarded to Professor Kesavan Esuvaranathan.
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Name | Company | Catalog Number | Comments |
MB49-PSA cells | N/A | N/A | ref (Wu QH, 2004) |
RPMI 1640 media | HyClone | SH30027.01 | |
Dulbecco's Modified Eagle's Medium (DMEM) media | Biowest | L0102 | |
Fetal Bovine Serum (FBS) South American | Biowest | S1810 | |
Fetal Bovine Serum (FBS) South American, Premium | Biowest | S181B | |
Fetal Bovine Serum (FBS) | HyClone | SH30088.03 | |
L-glutamine | Biowest | X0550 | |
Penicillin-Streptomycin | Biowest | L0022 | |
Hygromycin B | Invitrogen | 10687-010 | |
free PSA (Human) ELISA kit | Abnova | KA0209 | |
TRIzol Reagent for RNA extraction | Ambion | 15596026 | |
High Capacity cDNA Reverse Transcription Kit with RNase Inhibitor | Applied Biosystems | 4374967 | |
TaqMan Universal PCR Master Mix | Applied Biosystems | 4304437 | |
TaqMan Gene Expression Assay – Mouse Actb | Applied Biosystems | 4331182 | Mm00607939_s1 |
TaqMan Gene Expression Assay – Human KLK3 | Applied Biosystems | 4331182 | Hs00426859_g1 |
C57BL/6J female mice | In Vivos | 4 - 6 wk old | |
Anesthesia (75 mg/kg Ketamine and 1 mg/kg Medetomidine) | Local pharmacy | ||
Reversal drug (1 mg/kg Atipamezole) | Local pharmacy | ||
Ear punch | Electron Microscopy Sciences | 72893-01 | |
Hartmann's solution or Compound sodium lactate | B Braun | ||
Ophthalmic ointment - Duratears sterile ocular lubricant ointment | Alcon | ||
Heat pack - HotHands handwarmers | Heatmax Inc | ||
Introcan Certo IV catheter | B Braun | 4251300 | 24 G x 3/4″ |
Aquagel Lubricating jelly | Local pharmacy | ||
Poly-L-lysine solution, 0.01%, | Sigma | P4707 | |
cOmplete, Mini, EDTA-free Protease Inhibitor Cocktail | Roche | 4693159001 | |
Quantichrom Creatinine Assay Kit | BioAssay Systems | DICT-50 | |
Fluorescent dye - VivoTrack 680 | Perkin Elmer | NEV12000 | |
RNAlater-ICE Frozen Tissue Transition Solution | Ambion | 4427575 | |
Name | Company | Catalog number | Comments |
Equipment and Software | |||
7500 Realtime PCR System | Applied Biosystems | ||
7500 Software v2.3 | Applied Biosystems | ||
Metabolic Cage | Tecniplast | Vertical type rack for 12 cages | |
BD FACSCanto I system | BD Biosciences | ||
BD FACSDiva software v7 | BD Biosciences | ||
IVIS SpectrumCT in vivo imaging system | Caliper Life Sciences | ||
Living Image Software v3.1 | Caliper Life Sciences | ||
Vevo 2100 imaging system | VisualSonics |
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