Tumor biology: Use of tiled images in conjunction with measurements of cellular proliferation and death in response to drug treatments

Tumor growth is dependent on the balance between cell proliferation and cel l death, and these events occur heterogenously within an individual tumor. We present a methodology that provides integrative information about cell k inetics, cell death, and cell growth within individual tumors in animals tr eated with cytotoxic chemotherapeutic agents. Using HCT-116 and NCI-H460 ce lls, human colonic adenocarcinoma and non-small cell lung cells, respective ly, traditional xenograft studies mere performed, The tumor-bearing animals were treated with cyclophosphamide (Cytoxan), gemcitabine (Gemzar), or mit omycin C, and extensive analysis of the tumors was studied. Cell kinetics w ere evaluated by measuring the apoptotic and proliferation indices. The abi lity to image an entire tumor section using "tiling" by creating a large mo ntage from many high-resolution images makes it possible to identify region al differences within areas of tumor and to demonstrate differences in thes e tumor regions after treatment with selected chemotherapeutic agents. Two specific areas within tumors have been identified: (a) areas of viable cell s within the cell cycle, determined by bromodeoxyuridine and/or morphologic al characteristics determined by hematoxylin staining; and (b) areas of nec rosis determined by the absence of bromodeoxyuridine and proliferating cell nuclear antigen-labeled cells coupled with morphological changes. By stand ardizing the tumor size to 100 mm(2), different patterns of tumor responses to chemotherapeutic agents were determined. By creating such tiled images and by quantitating cell cycle kinetics, it is possible to gain a more comp lete understanding of tumor growth and response to treatment, leading to th e development of more reliable methods for assessing the clinical behavior of anticancer drugs.