Role of Di-allyl Disulfide, a Garlic Component in NF-κB Mediated Transient G2-M Phase Arrest and Apoptosis in Human Leukemic Cell-lines

Abstract

Diallyl disulfide (DADS), the major organosulfur component of processed garlic is very effective in chemoprevention of several types of cancers; however, its detailed mechanism is yet to be divulged. Present study shows antiproliferative activity of DADS against human leukemic cell-lines, mainly U937. DADS induced transient G2/M phase arrest, which is evident from FACS analysis. The results revealed that a significant transcriptional induction of p21 happened in early hours of treatment, which is due to increased nuclear translocation of NF-κB and its specific binding to p21 promoter. However, in the later hours, G2/M arrest is lost leading to apoptosis via intrinsic mitochondria-mediated pathway through generation of reactive oxygen species followed by changes in mitochondrial membrane potential. Western blots indicate release of cytochrome-c, activation of caspase-3, cleavage of PARP1, and finally decrease in bcl-2 levels. In addition, inactivation of NF-κB by its inhibitor BAY 11-7085 causes early onset of apoptosis without any transient G2/M arrest. Thus, in conclusion, DADS induces reversible G2/M arrest through NF-κB mediated pathway in human leukemic cell lines, like U937, K562, and Jurkat, lacking wild type p53. However, G2/M arrest is lost owing to the incapability of the damage repair system that leads to apoptosis.

ACKNOWLEDGMENTS

We thank Prof. Uma Dasgupta, Department of Biophysics, Molecular Biology and Bioinformatics, University of Calcutta for allowing her tissue culture facility, and Dr. Tapas K. Sengupta for his helpful suggestions. We are grateful to Mr. Abhijit Bhattacharjee (CU, Kolkata) and George Banik (NICED, Kolkata) for their immense help in FACScan analysis. We acknowledge DST and UGC for funding the work and UGC (RFSMS) for providing fellowship to Pritha Dasgupta. This work was supported by grants from Department of Science and Technology (SR/SO/BB-58/2007), Govt. of India and University Grant Commission (UGC-37-398/2009) to Sumita Sengupta and Departmental grant from UGC-DSA.