The present invention relates to composition comprising at least one non-pathogenic bacterial cell, wherein the non-pathogenic bacterial cell comprises at least a first and a second nucleic acid sequence, the first nucleic acid sequence comprising at least one non-constitutive promoter operably linked to the second nucleic acid sequence that encodes therapeutic agent, wherein the non-constitutive promoter is an inducible promoter responsive to at least one stimuli and the at least one stimuli comprises the presence of a certain density or a certain number of bacterial cells comprising the first and second nucleic acid sequences.