Antineoplastic Agents/pharmacology; Lactoferrin/chemistry; Lactoferrin/pharmacology; Peptide Fragments/pharmacology; Amino Acid Sequence; Animals; Anti-Bacterial Agents/chemical synthesis; Anti-Bacterial Agents/chemistry; Anti-Bacterial Agents/pharmacology; Antineoplastic Agents/chemical synthesis; Antineoplastic Agents/chemistry; Antineoplastic Agents/toxicity; Breast Neoplasms/pathology; Circular Dichroism; Drug Design; Escherichia coli/drug effects; Fibroblasts; Hemolysis/drug effects; Humans; Hydrophobic and Hydrophilic Interactions; Lactoferrin/toxicity; Mice; Microbial Sensitivity Tests; Molecular Sequence Data; Molecular Structure; Peptide Fragments/chemical synthesis; Peptide Fragments/chemistry; Peptide Fragments/toxicity; Quantitative Structure-Activity Relationship; Staphylococcus aureus/drug effects; Substrate Specificity; Tumor Cells, Cultured