Figure 1. Identification of genes associated with the host response to tissue inhibitor of metalloproteinase 2 (TIMP-2). A) Strategy for comparing gene expression patterns of MC38/null and MC38/TIMP-2 tumor cells in vitro and in vivo. Using cDNA microarrays, MC38/null (green) and MC38 TIMP-2 (red) were compared in vitro and in vivo after 6 or 12 days of growth. Genes associated with tumor-host interactions due to TIMP-2 might be similarly expressed in vitro (e.g., yellow spot in lower left corner of top array, arrowhead), but differentially expressed in vivo (red spot in lower left corner of bottom two arrays, arrowheads). B) cDNA microarray analysis identified 13 such genes. Each pixel represents the expression ratio on one array. Red indicates upregulation in the MC38/TIMP-2 sample, and green indicates downregulation. Color intensity is proportional to expression ratio. Black represents ratios close to 1.0. C) Microarray and qRT-PCR data for PTPN16, the murine gene for mitogen-activated protein (MAP) kinase phosphatase-1 (MKP-1). Expression ratios were close to 1.0 in vitro, but showed upregulation in MC38/TIMP-2 tumors in vivo.