Rodent Tumour Transplant Model: To Assess the Effects of Immunosuppressive Agents on Tumour Growth after Transplantation

Abstract

Introduction: Transplantation has immense benefits for the recipients, but there can be some serious risks associated both in short and long terms. One such risk factor is either the development of a de-novo tumour or transmission of a tumour from the donor inadvertently. The use of immunosuppression in transplant recipients can remove the natural checks against cancerous cells by the immune system and thus the behaviour of tumours can be unpredictable. We describe a tumour transplant model to assess the behaviour of transplanted tumour in hosts in the presence of different immunosuppressive agents. Methods: Rat kidney tumour cells (BP36B) were transfected with a lentivirus based construct designed to produce stable transfects that would express both green fluorescence protein (GFP) and Luciferase. The presence of Luciferase can be detected by supplying a substrate, luciferin, which produces a bioluminescent product. The substrate can be injected into live animals and the cells expressing the luciferase be detected in real time. Fixed number of tumour cells of Wistar origin (1.8* 107) were injected subcutaneously into two different strains of rats - Wistar and Lewis; to mimic well-matched (Wistar) and poorly-matched (Lewis) groups. Animals were further divided into treatment group receiving cyclosporine and a control group with no immunosuppression. Tumour behaviour was monitored in real time with IVIS spectrum in vivo imaging system. 10-15 minutes before imaging, the animals were injected with Luciferin (substrate for Luciferase) and the anaesthetised animals were placed in a heated dark chamber and photons emitted from the labelled tumour cells were detected on an ultra sensitive CCD camera. Animals were scanned once weekly for 4-6 weeks and tumour behaviour was monitored in different experimental conditions. Cyclosporine treatment in half of the animals from both strains was stopped midway to further determine the role of rejection on transplanted tumour cells. Tumour depth was determined in some animals with 3D reconstruction and was reconfirmed after post mortem examination in palpable tumours. Results: All the animals displayed good bioluminescent signals. Due to the high sensitivity of the imaging system, we were able to monitor the tumour cells even in the absence of palpable tumour lumps. Significantly varied tumour behaviour under different experimental conditions was observed using this model. Conclusions: This model provides a highly sensitive approach of monitoring tumour behaviour under different experimental conditions even in the absence of palpable tumours. Accurate measurements for local and distant spread can be made in live animals. Furthermore post mortem analysis of the tumour cells can be done with florescent microscopy for tissue invasion and flow cytometry for hematopoietic metastasis.Figure: [Rat image]