ERBB2 and cancer: Although Gram-positive minicells are negative for lipopolysaccharides (LPS) and may be ultimately more adapted for clinical use, most studies have used Gram-negative minicells that can be easily redirected to cancer-specific receptors (e.g. HER2/neu) with bispecific antibodies targeting both the LPS O-antigen on minicells and a tumor marker [57, 58].