Antineoplastic Agents/pharmacology; ErbB Receptors/antagonists & inhibitors; Piperazines/pharmacology; Protein Kinase Inhibitors/pharmacology; Pyrazoles/pharmacology; Pyrimidines/pharmacology; Receptor, IGF Type 1/antagonists & inhibitors; Animals; Antineoplastic Agents/metabolism; Apoptosis/drug effects; Cell Proliferation/drug effects; Drug Resistance, Neoplasm/drug effects; Drug Stability; ErbB Receptors/genetics; ErbB Receptors/metabolism; Erlotinib Hydrochloride; Female; HT29 Cells; Humans; Male; Membrane Potential, Mitochondrial/drug effects; Mice; Microsomes, Liver/metabolism; Mutation; Phosphorylation/drug effects; Piperazine; Piperazines/metabolism; Protein Kinase Inhibitors/metabolism; Pyrazoles/metabolism; Pyrimidines/metabolism; Quinazolines/pharmacology; Receptor, IGF Type 1/metabolism; Signal Transduction/drug effects; Xenograft Model Antitumor Assays