An in vitro tumor model: analysis of angiogenic factor expression after chemotherapy

Tumor tissues include malignant cells and a stroma made up of mainly inflammatory cells, endothelial cells, and fibroblasts. To differentiate the effects of treatment on angiogenic cytokine secretion in tumor tissue, exponential and stationary phase human CaKi-1 renal cell carcinoma cells, human SW2 small cell lung carcinoma cells, human umbilical vein endothelial cells (HUVECs), murine NIH-3T3 fibroblasts, and murine RAW264.7 macrophages were exposed to gemcitabine, paclitaxel, carboplatin, and the protein kinase Cbeta inhibitor LY317615, and secretion (24 h) of tumor necrosis factor-alpha, basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF), and transforming growth factor (TGF)-beta was determined by a Luminex FlowMetrix assay. After 72 h of exposure, exponential RAW, 3T3, and SW2 cells were sensitive to gemcitabine; exponential and stationary SW2 and HUVECs were sensitive to paclitaxel; and exponential and stationary HUVECs were most sensitive to LY317615. None of the cells secreted detectable tumor necrosis factor-alpha. Generally, exponential cells secreted higher levels of cytokines than stationary cells (stationary cells secreted approximately 10 times less TGF-beta). Only malignant cells secreted VEGF (80-300 pg/10(6) cells). VEGF secretion by exponential SW2 cells decreased in an anticancer agent concentration-dependent manner. Every cell type secreted TGF-beta (40-700 pg/10(6) cells). Exponential 3T3, RAW, CaKi-1, and SW2 cells secreted the most TGF-beta, and levels did not decrease with treatment. Only CaKi-1, SW2, and HUVECs secreted bFGF (0.5-50 pg/10(6) cells). CaKi-1 cells increased secretion of bFGF with therapy. Although malignant cells alone secreted VEGF, stromal cells secreted TGF-beta and bFGF at levels comparable with or greater than malignant cells and thus may be important contributors to tumor growth and progression.