In Vitro Characterization of the Bacteria-derived Hypoxia-selective Cytotoxin BE-₄₃₅₄₇

TY - JOUR

T1 - In Vitro Characterization of the Bacteria-derived Hypoxia-selective Cytotoxin BE-43547

AU - Busk, Morten

AU - Eggertsen, Peter P

AU - Overgaard, Jens

AU - Horsman, Michael R

AU - Tørring, Thomas

AU - Jacobsen, Kristian M

AU - Poulsen, Thomas B

PY - 2023/12

Y1 - 2023/12

N2 - BACKGROUND/AIM: Hypoxia-activated pro-drugs, such as TH-302, may kill hypoxic treatment-resistant tumor cells, but have failed in clinical trials. This may be related to variable levels of drug-activating reductases. Compounds such as bacteria-derived BE-43547, which target hypoxic cells independently of reductases, may be beneficial. This study characterized the in vitro potency and hypoxia selectivity of BE-43547 and TH-302.MATERIALS AND METHODS: Tumor cells were exposed to different oxygenation levels in the presence/absence of drug, and survival was quantified using total cell number (BE-43547) or clonogenic survival (BE-43547 and TH-302) assays. Half-maximal inhibitory concentration (IC 50) values and the hypoxia-cytotoxicity-ratio (HCR: normoxic IC 50/hypoxic IC 50) were determined from dose-response curves. Finally, both drugs were tested in spheroids exposed to 20% or 0% O 2 for 24 h followed by assessment of clonogenic survival. RESULTS: BE-43547 was highly potent and displayed little inter-cell line variability. Strongly enhanced cytotoxicity was observed under oxygen-restricted conditions with HCR's of ~100 and ~20 after 24 h of treatment with 0 or 0.5% O 2, respectively. Reducing treatment time somewhat reduced hypoxia selectivity. Hypoxia selectivity was observed regardless of whether the drug was added before or during the hypoxic challenge. TH-302 IC 50 values varied 10-fold under oxic conditions, whereas those of the anoxic-to-normoxic HCR varied from 15 to 88. Both BE-43547 and TH-302 were unable to completely sterilize anoxic incubated spheroids. CONCLUSION: BE-43547 is highly hypoxia-selective, and unlike TH-302, displayed minimal variability between cell lines, suggesting that BE-43547 targets a fundamental feature/target that is only present, or of survival importance, during hypoxia. Spheroid experiments suggested inadequate tissue penetrability, which may be overcome by designing novel drug analogs.

AB - BACKGROUND/AIM: Hypoxia-activated pro-drugs, such as TH-302, may kill hypoxic treatment-resistant tumor cells, but have failed in clinical trials. This may be related to variable levels of drug-activating reductases. Compounds such as bacteria-derived BE-43547, which target hypoxic cells independently of reductases, may be beneficial. This study characterized the in vitro potency and hypoxia selectivity of BE-43547 and TH-302.MATERIALS AND METHODS: Tumor cells were exposed to different oxygenation levels in the presence/absence of drug, and survival was quantified using total cell number (BE-43547) or clonogenic survival (BE-43547 and TH-302) assays. Half-maximal inhibitory concentration (IC 50) values and the hypoxia-cytotoxicity-ratio (HCR: normoxic IC 50/hypoxic IC 50) were determined from dose-response curves. Finally, both drugs were tested in spheroids exposed to 20% or 0% O 2 for 24 h followed by assessment of clonogenic survival. RESULTS: BE-43547 was highly potent and displayed little inter-cell line variability. Strongly enhanced cytotoxicity was observed under oxygen-restricted conditions with HCR's of ~100 and ~20 after 24 h of treatment with 0 or 0.5% O 2, respectively. Reducing treatment time somewhat reduced hypoxia selectivity. Hypoxia selectivity was observed regardless of whether the drug was added before or during the hypoxic challenge. TH-302 IC 50 values varied 10-fold under oxic conditions, whereas those of the anoxic-to-normoxic HCR varied from 15 to 88. Both BE-43547 and TH-302 were unable to completely sterilize anoxic incubated spheroids. CONCLUSION: BE-43547 is highly hypoxia-selective, and unlike TH-302, displayed minimal variability between cell lines, suggesting that BE-43547 targets a fundamental feature/target that is only present, or of survival importance, during hypoxia. Spheroid experiments suggested inadequate tissue penetrability, which may be overcome by designing novel drug analogs.

KW - Hypoxia

KW - hypoxiaselective drugs

KW - natural drugs

KW - radiotherapy

KW - treatment resistance

UR - http://www.scopus.com/inward/record.url?scp=85178651623&partnerID=8YFLogxK

U2 - 10.21873/anticanres.16735

DO - 10.21873/anticanres.16735

M3 - Journal article

C2 - 38030202

SN - 0250-7005

VL - 43

SP - 5319

EP - 5329

JO - Anticancer Research

JF - Anticancer Research

IS - 12

ER -