Clinical & Experimental Metastasis 17: 369–376, 1999. © 1999 Kluwer Academic Publishers. Printed in the Netherlands. 369 Quantitative detection of lac-Z-transfected CC531 colon carcinoma cells in an orthotopic rat liver metastasis model Axel Wittmer 1 , Khashayarsha Khazaie 2 & Martin R. Berger 1 1 Unit of Toxicology and Chemotherapy, German Cancer Research Center (DKFZ), Heidelberg, Germany; 2 Department of Cellular Immunology, German Cancer Research Center (DKFZ), Heidelberg, Germany Received 12 May 1999; accepted in revised form 8 July 1999 Key words: beta-galactosidase, CC531, chemiluminescence, colon cancer, liver metastasis Abstract Disseminated colon carcinoma metastases in the liver are associated with low cure rates and constitute a serious therapeutic problem. Appropriate experimental models which mimic metastases development and outgrowth can provide insight into the mechanism of this lethal process and facilitate the finding of new approaches for its control. We established an orthotopic liver metastases model based on CC531 rat colon adenocarcinoma cells which were transfected with a β -galactosidase gene as marker to facilitate their detection. Intraportal injection of CC531-lac-Z cells resulted in a rapid and locally aggressive growth within the liver and was characterised by a tumour volume doubling time of 20 h and abundant angiogenesis. A commercially available chemi-luminescence assay allowed rapid, quantitative and sensitive detection of the diffusely growing tumour cells. Immunogenicity of CC531-lac-Z cells induced by the marker gene was significantly reduced by co- administering the tumour cells with matrigel. Within an observation period of three weeks following tumour cell injection only 6% of the animals showed lung involvement, thus indicating a specific homing of CC531-lac-Z cells to the liver. This period appears long enough to allow therapeutic manipulations at various stages of tumour growth in the liver. It is envisaged that the model will have applications for various therapeutic strategies. Introduction Colon carcinoma is the second leading cause of cancer death in western countries [1, 2]. The 5-year survival rate of all patients with colon cancer ranges around 60% [3] and the estimated cure rate in Europe amounts to 38–42% after a follow up period of 8 years [4]. The poorest prognosis is related to distant metastases, with the liver being the main target of hematopoetic metastatic spread: 35–40% of oper- able patients harbour micrometastases in their liver at the time of surgery [5] and 70–80% of fatal cases show liver involvement at autopsy [6]. Diffuse or gross hepatic involvement is left to therapeutic options such as systemic chemotherapy, locoregional ad- ministration (portal vein- or hepatic artery infusion [7, 8]), chemoembolisation [9] or combinations of these procedures. Systemic chemotherapy of liver metastases has added little to survival besides palliative effects, which is in line with the modest chemosensitivity of colon tumours known from adjuvant chemotherapy studies. Locoregional chemotherapy such as intraportal infusion therapy has been found to in- crease survival rates by 5–11% after 5 years compared with surgery alone [10, 11]. Hepatic arterial infusion was as- Correspondence to: Martin R. Berger, Unit of Toxicology and Chemother- apy, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, 69120 Heidelberg, Germany. Tel: +49-6221-423310; Fax: +49-6221- 423313; E-mail: M.Berger@DKFZ-Heidelberg.de sessed to achieve distinctly higher tumour response rates than systemic chemotherapy but did not effect survival rates [8]. These studies show, that the current clinical arsenal is insufficient for a break-through against advanced colon cancer and that more detailed knowledge about colon can- cer metastases is needed to overcome this process. Over the last decades, experimental studies repeatedly generated new concepts for more effective anticancer treatment modes, e.g. for inhibition of angiogenesis [12, 13]. With regard to liver metastases, the available animal tumour models can be grouped into the following categories: the majority is based on transplanting tumour cells subcutaneously or intraperi- toneally [14], id est non-orthotopically. Orthotopical models can be sub-grouped into those which imitate the physiologi- cal metastatic spread of colon cancer by intraportal [15–17] or spleen injection [18] which results in a diffuse outgrowth of tumour cells in the liver. Other orthotopical models are based on implanting tissue fragments or cells of a tumour under the Glisson‘s liver capsule and show a local, limited, and nodal growth pattern [19–21]. Quantification of tumour growth in the latter models is often done by measuring tu- mour diameters [19–21], whereas the diffuse models cannot be quantified easily. Attempts to solve this problem include a 3-D reconstruction of metastases by consecutive serial sec- tions [16] or counting tumour nodules in the liver [15]. In addition, an immunohistological examination of tissue with tumour specific antibodies has been tried [15]. These assays