Bactofection of SW620 cell by Lactococcus lactis M4

In this study, a local dairy isolate, L. lactis M4 was investigated for its ability to be developed as a live delivery vector to deliver plasmid DNA into human colon cancer cell line, SW620. L. lactis M4 strain was found to adhere to and internalize SW620 cells optimally after 2 hours of infection period at a multiplicity of infection 250:1, bacteria per cancer cell. Bacteria also managed to survive intracellularly for 7 hours. Entry into SW620 cells was inhibited by Cytochalasin D and Vinblastine, indicating that cell uptake was dependent on microfilament and microtubule stability. Bactofection of SW620 cells by L. lactis M4 was demonstrated through the expression of fluorescent proteins from a novel dual-expression plasmid, pHSR. L. lactis M4 was able to express red fluorescent protein intracellularly of SW620 cells, which were subsequently observed to express green fluorescent protein at 3 hours post-invasion. The expression of fluorescent proteins from pHSR resulted from the bactofection of SW620 cells by L. lactis M4 has proven that this strain can be developed as a vector to deliver plasmid DNA into the cancer cell