AHR and cancer: However, we cannot rule out the cytotoxicity of butyrate at high concentrations (above 5 mmol L−1) (Figure S2, Supporting Information), as it accumulates in cancer cells growing in glucose.[25] The AhR activity induced by acetate, valerate, and isovalerate was found at high concentrations (50, 5, and 5 mmol L−1, respectively), whereas isobutyrate had no AhR activity.