Bacillus thuringiensis is one of the most important microorganisms used against
cancer cell lines in latest studies all over the world. This study aims to perform the isolation, molecular identification, and to identify novel B. thuringiensis strains that specifically targeting human
cancer cell-killing activities in Iran. A total of 88 B. thuringiensis isolates were recovered from Iran. Upon the treatment of the non-hemolytic crystal
proteins by
proteinase K, five isolates belonging to three biotypes, thuringiensis, kurstaki and sotto of B. thuringiensis are found to have different cytotoxicity toward HCT-116 and CCRF-CEM cell lines. Digested inclusions of the isolates consisted of one major poly
peptide of 34-kDa, as estimated by
sodium dodecyl-sulfate polyacrylamide gel electrophoresis. The structure, molecular identification, and functionality of five isolates inclusion
proteins have shown to be closely like to parasporin-2 but their size of activated
protein is not similar to this
parasporin. It is unclear that discovered damaging
proteins are parasporin-2. This 34-kD
protein exhibited varying degrees of cytocidal activity toward human colon and
blood cancer cells and caused cell swelling and the formation of
blebs in the surface of the cells or alteration in cytoskeleton. The soil in the humid and temperate climates of Iran is a good reservoir for
parasporin producing B. thuringiensis. The isolated B. thuringiensis strains exhibit specific and different cytocidal activities against human colon and
blood cancer cells.
Parasporin is a novel cytotoxic
protein to human
cancer cells produced by B. thuringiensis and these toxins appeared to attack an identical target on human
cancer cells.