CCL21 and colorectal cancer: Development of an engineered probiotic for the targeted treatment of colorectal cancer. They built three detection modules aimed at hypoxia, low pH and lactic acid concentrations. Further, they implemented an adhesion module using the Streptococcus gallolyticus HlpA gene which interacts with heparan sulfate glycoprotein on the tumor surface. Finally, hemolysin E, CCL21 and CDD-iRGD (Bit1 fusion protein of cell death domain and tumor perforin) are used as therapeutic proteins and bacteriophage lysis gene phiX174 E was employed as biocontainment strategy