The discovery and characterization of K‐563, a novel inhibitor of the Keap1/Nrf2 pathway produced by Streptomyces sp

Abstract

Keap1/Nrf2 pathway regulates the antioxidant stress response, detoxification response, and energy metabolism. Previous reports found that aberrant Keap1/Nrf2 pathway activation due to Kelch‐like ECH‐associated protein 1 (Keap1) mutations or Nuclear factor E2‐related factor 2 (Nrf2) mutations induced resistance of cancer cells to chemotherapy and accelerated cell growth via the supply of nutrients. Therefore, Keap1/Nrf2 pathway activation is associated with a poor prognosis in many cancers. These previous findings suggested that inhibition of Keap1/Nrf2 pathway could be a target for anti‐cancer therapies. To discover a small‐molecule Keap1/Nrf2 pathway inhibitor, we conducted high‐throughput screening in Keap1 mutant human lung cancer A549 cells using a transcriptional reporter assay. Through this screening, we identified the novel Keap1/Nrf2 pathway inhibitor K‐563, which was isolated from actinomycete Streptomyces sp. K‐563 suppressed the expression of Keap1/Nrf2 pathway downstream target genes or the downstream target protein, which induced suppression of GSH production, and activated reactive oxygen species production in A549 cells. K‐563 also inhibited the expression of downstream target genes in other Keap1‐ or Nrf2‐mutated cancer cells. Furthermore, K‐563 exerted anti‐proliferative activities in these mutated cancer cells. These in vitro analyses showed that K‐563 was able to inhibit cell growth in Keap1‐ or Nrf2‐mutated cancer cells by Keap1/Nrf2 pathway inhibition. K‐563 also exerted synergistic combinational effects with lung cancer chemotherapeutic agents. An in vivo study in mice xenotransplanted with A549 cells to further explore the therapeutic potential of K‐563 revealed that it also inhibited Keap1/Nrf2 pathway in lung cancer tumors. K‐563, a novel Keap1/Nrf2 pathway inhibitor, may be a lead compound for development as an anti‐cancer agent.

Potential Applications of NRF2 Modulators in Cancer Therapy

“…Of note, K-563 abrogated the expression of NRF2 target genes such as GCLC, GCLM, AKR1C1 (reductase family 1 member C1), ME1, NQO1 and TXNRD1 in A549 NSCLC cells and in the human gallbladder cancer (GBC) cell line TGBC24TKB, without altering the NRF2 protein levels, its ARE-binding ability, or its nuclear localization. As a result, K-563 promoted ROS accumulation and synergized with either Cisplatin or Etoposide in A549 NSCLC cells, suppressing also cell proliferation in GBC cells (TGBC24TKB) without affecting normal human lung cells (BEAS-2B) [337]. In the context of hematologic tumors, Zhang et al, identified 4f, a pyrazolyl hydroxamic acid derivative with potent antineoplastic effects in human THP-1, HL60 and U937 AML (acute myeloid leukemia) cells.…”

NRF1 or NRF2: Emerging Role of Redox Homeostasis on PERK/NRF/Autophagy Mediated Antioxidant in Tumor and Patient Dependent Chemo Sensitivity

“…In vivo experiments on xenograft mice with A549 cells showed that K563 effectively suppressed the KEAP1/NRF2 signaling pathway within lung cancer tumors. [306].…”

Antioxidative Stress: Inhibiting Reactive Oxygen Species Production as a Cause of Radioresistance and Chemoresistance

“…In addition, the inhibitor K-563 produced by Streptomyces sp. is able to reduce the production of GSH by inhibiting the Keap1-Nrf2 pathway [ 142 ]. Both inhibitors raise the sensitivity of tumour cells by adjusting glucose and glutamine catabolism.…”