Abstract
Mycobacterium indicus pranii (MIP) is a non-pathogenic mycobacterium, which has been tested on several cancer types like lung and bladder where tumour regression and complete recovery was observed. In discovering the potential cytotoxic elements, a preliminary test was carried out using four different fractions consisting of live bacteria, culture supernatant, heat killed bacteria and heat killed culture supernatant of MIP against two human cancer cells A549 and CaSki by 3-(4,5-dimethyl thiazol)-2,5-diphenyl tetrazolium bromide (MTT) assay. Apoptosis was investigated in MCF-7 and ORL-115 cancer cells by poly-(ADP-ribose) polymerase (PARP) and DNA fragmentation assays. Among four MIP fractions, only heat killed MIP fraction (HKB) showed significant cytotoxicity in various cancer cells with inhibitory concentration, IC50 in the range 5.6–35.0 μl/(1.0 × 106 MIP cells/ml), while cytotoxicity effects were not observed in the remaining fractions. HKB did not show cytotoxic effects on non-cancerous cells contrary to cancerous cells, suggesting its safe usage and ability to differentially recognize between these cells. Evaluation on PARP assay further suggested that cytotoxicity in cancer cells were potentially induced via caspase-mediated apoptosis. The cytotoxic and apoptotic effects of MIP HKB have indicated that this fraction can be a good candidate to further identify effective anti-cancer agents.
Highlights
Apart from inducing the immune system, certain mycobacteria species were reported to induce a direct cytotoxic effect on cancer cells
Mycobacterium indicus pranii (MIP) was separated into four fractions: live bacteria (LB), culture supernatant (CS), heat killed bacteria (HKB) and heat killed culture supernatant (HKS)
Only MIP HKB fraction showed cytotoxic effects where cell viability reduced to 24% in CaSki and 26% in A549, while the remaining fractions did not show any killing effects (Fig. 1)
Summary
Apart from inducing the immune system, certain mycobacteria species were reported to induce a direct cytotoxic effect on cancer cells. As reported by Saitoh and Morales, BCG and BCG components[4] could induce cancer cell apoptosis, while M. phlei or mycobacterial cell wall and DNA components possess certain anti-tumour activity[10]. These findings provides an insight on exploiting MIP and its cellular components as a potential anti-cancer agent against various human cancer cell lines. As such to date, only certain types of cancers were reported to show cytotoxic effects upon MIP treatment in in vivo[11,12]. We evaluated in vitro cytotoxicity effect of four different MIP fractions consisting of live bacteria, culture supernatant, heat killed bacteria and heat killed culture supernatant against various human cancer type namely breast, cervical, oral, lung, bladder, liver and prostate
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