Outcomes studies of many types of cancer have revealed that tumors of indistinguishable histological appearance at the time of presentation may differ significantly in aggressiveness and in their response to therapy. A strategy that would enable early identification of patients at high-risk for disease progression, and allow screening of multiple therapeutic agents simultaneously for efficacy would improve management of cancer significantly. We have developed an orthotopic organ culture model of bladder cancer in which quantum dot-based fluorescent imaging approaches are used to obtain quantitative measurements of tumor cell behavior. Human transitional cell carcinoma (TCC) cells were labeled with quantum dots and the cells instilled into the rat bladders cultured ex vivo. Cell implantation, proliferation and invasion into the organ wall were monitored using epifluorescence imaging and two-photon laser scanning microscopy (TPLSM). Qdot-labeled tumor foci were evident in the bladder wall by 7 d of organ culture. Several of the lesions had increased in size by 14 d, with an ∼3-fold increase in tumor area at 14 d compared with 7 d. Intravesical administration of the chemotherapeutic agent, thiotepa, led to a reduction in size of established tumor foci after 4 d exposure of drug. This was in contrast to continued expansion of tumor cell masses in control bladders receiving no drug. To estimate the depth of invasion of Qdot-labeled tumor cells into the bladder wall, we employed TPLSM. Tissue was processed in the presence of Hoechst dye 33342 and the lectin wheat-germ agglutinin conjugated to the fluorophore Alexa 488 to highlight nuclei and tissue architecture, respectively. Measurement of fluorescent signals from both tumor cells and the surrounding tissue enabled evaluation not only of the size of tumor foci, but also the extent of tumor cell invasion into the bladder wall. Using this approach, we compared the growth and invasion of the TCCSUP and 253J-BV bladder cancer cell lines. Based on acquisition of optical sections (z-series) through the bladder wall, both lines gave rise to tumor cell masses of similar vertical dimensions at 7 d following tumor cell instillation (75 ± 31 μm for TCCSUP vs. 80 ± 19 μm for 253J-BV). However, the extent of invasion of each line into the bladder wall differed significantly (p<0.05). Tumor foci derived from TCCSUP cells remained superficial with an average depth of invasion of 14 ± 8 μm (microns). In contrast, 253J-BV tumor foci invaded to a depth of 85 ± 20 μm microns. Thus, we were able to assign distinct phenotypes to two metastatic bladder cancer cell lines based on different patterns of invasiveness into the bladder wall. Taken together, these observations suggest that our assay system, which we have named EViTAS (ex vivo tumor assay system), can recapitulate salient aspects of tumor growth in the host and is amenable to behavioral profiling of human cancer.
[Proc Amer Assoc Cancer Res, Volume 47, 2006]