Benzisothiazolone Derivatives Exhibit Cytotoxicity in Hodgkin's Lymphoma Cells through NF-κB Inhibition and are Synergistic with Doxorubicin and Etoposide

BACKGROUND

The authors investigated the NF-κB inhibitory role of three Benzisothiazolone (BIT) derivatives (1, 2 and 3) in Hodgkin's Lymphoma cells (L428) which constitutively express activated NF-κB. All three compounds showed dose-dependent NF-κB inhibition (78.3, 70.7 and 34.6%) in the luciferase reporter gene assay and were found cytotoxic at IC50 values of 3.3μg/ml, 4.35μg/ml and 13.8μg/ml, respectively by the XTT assay. BIT 1and BIT 2 (but not BIT 3) suppressed both NF-κB subunits p50 and p65 in cytoplasmic and nuclear extracts in a concentration-dependent manner. Furthermore, BIT 1 showed a moderate synergistic effect with the standard chemotherapy drugs etoposide and doxorubicin, whereas BIT 2 and 3 showed a moderate additive effect to antagonistic effect. Cisplatin exhibited an antagonist effect on all the compounds tested under various concentrations, except in the case of 1.56μg/ml of BIT 3 with 0.156μg/ml of cisplatin. The compounds also inhibited the migration of adherent human lung adenocarcinoma cells (A549) in vitro. We conclude that especially BIT 1 and BIT 2 have in vitro anti-inflammatory and anti-cancer activities, which can be further investigated for future potential therapeutic use.

METHODS

Inspired by the electrophilic sulfur in Nuphar alkaloids, monomeric and dimeric benzisothiazolones were synthesized from dithiodibenzoic acid and their NF-κB inhibitory role was explored. NF-κB inhibition and cytotoxicity of the synthesized derivatives were studied using luciferase reporter gene assay and XTTassay. Immunocytochemistry studies were performed using L428 cells. Cell migration assay was conducted using the A549 cell line. L428 cells were used to conduct combination studies and the results were plotted using CompuSyn software.

RESULTS

Benzisothiazolone derivatives exhibited cytotoxicity in Hodgkin's Lymphoma cells through NF-κB inhibition. Potent compounds showed suppression of both NF-κB subunits p50 and p65 in a concentrationdependent manner, both in cytoplasmic and nuclear extracts. Combination studies suggest that benzisothiazolone derivatives possess a synergistic effect with etoposide and doxorubicin. Furthermore, the compounds also inhibited the migration of A549 cells.

CONCLUSION

Benzisothiazolones bearing one or two electrophilic sulfur atoms as part of the heterocyclic framework exhibited cytotoxicity in Hodgkin's Lymphoma cells through NF-κB inhibition. In addition, these derivatives also exhibited a synergistic effect with etoposide and doxorubicin along with the ability to inhibit the migration of A549 cells. Our study suggests that BIT-based new chemical entities could lead to potential anticancer agents.

Broad spectrum anti-infective properties of benzisothiazolones and the parallels in their anti-bacterial and anti-fungal effects

Various mono- and bis-benzisothiazolone derivatives were synthesized and screened against different strains of bacteria and fungi in order to understand the effect of multiple electrophilic sulfur atoms and substitution pattern in the immediate vicinity of reactive sulfur. Staphyllococcus aureus-ATCC 7000699, MRSA and S. aureus-ATCC 29213 (Quality Control strain) were more susceptible to this class of compounds, and the most potent derivative 1.15 had MIC₅₀ of 0.4μg/mL (cf. Gentamicin=0.78μg/mL). CLogP value, optimally in the range of 2.5-3.5, appeared to contribute more to the activity than the steric and electronic effects of groups attached at nitrogen. By and large, their anti-fungal activities also followed a similar trend with respect to the structure and CLogP values. The best potency of IC₅₀=0.1μg/mL was shown by N-benzyl derivative (1.7) against Aspergillus fumigatus; it was also potent against Candida albicans, Cryptococcus neoformans, Sporothrix schenckii, and Candida parapsilosis with IC₅₀ values ranging from 0.4 to 1.3μg/mL. Preliminary studies also showed that this class of compounds have the ability to target malaria parasite with IC₅₀ values in low micromolar range, and improvement of selectivity is possible through structure optimization.