IITZ-01, a novel potent lysosomotropic autophagy inhibitor, has single-agent antitumor efficacy in triple-negative breast cancer in vitro and in vivo

Abstract

Autophagy is a homeostatic process that recycles damaged organelles and long-lived proteins by delivering them in double-membrane vesicles to lysosomes for degradation. Autophagy has a prominent role in survival, proliferation, and resistance of tumors in metabolic and chemotherapeutic stress conditions. Clinical trials with chloroquine-a known autophagy inhibitor-were unable to achieve complete autophagy inhibition in vivo, warranting the search for more potent autophagy inhibitors. In a process of exploring the mechanism of action of previously identified cytotoxic s-triazine analogs, we discovered that both IITZ-01 and IITZ-02 act as potent autophagy inhibitors. Treatment with these compounds resulted in the vacuolated appearance of cells due to their specific accumulation in lysosomes. In addition, these basic compounds also deacidify lysosomes as evidenced by the decrease in lysotracker red staining and inhibit maturation of lysosomal enzymes leading to lysosomal dysfunction. IITZ-01 and IITZ-02 enhance autophagosome accumulation but inhibit autophagosomal degradation by impairing lysosomal function, finally resulting in the inhibition of autophagy. Interestingly, compound IITZ-01 exhibited more than 10-fold potent autophagy inhibition along with 12- to 20-fold better cytotoxic action than CQ. IITZ-01 and IITZ-02 also abolished mitochondrial membrane potential and triggered apoptosis through the mitochondria-mediated pathway. Furthermore, IITZ-01 and IITZ-02 displayed potent antitumor action in vivo through autophagy inhibition and apoptosis induction in MDA-MB-231 breast cancer xenograft model with IITZ-01 exhibiting superior anticancer efficacy. Overall, these data demonstrate that IITZ-01 is potent autophagy inhibitor with single-agent anticancer activity and awaits further preclinical development as potential anticancer therapeutic.

Combination of an Autophagy Inducer and an Autophagy Inhibitor: A Smarter Strategy Emerging in Cancer Therapy

“…Moreover, clinical trials showed that autophagy is unable to be completely inhibited by CQ in vivo. These warrant us that searching more potent autophagy inhibitors is critical for promoting an opportunity to apply the combination therapeutic strategy in clinical studies (Lalita Guntuku et al, 2019), especially agents that specifically inhibit autophagyrelated (ATG) proteins (Pei-Feng Liu1 et al, 2018).…”

Upregulation of DR5 and Downregulation of Survivin by IITZ-01, Lysosomotropic Autophagy Inhibitor, Potentiates TRAIL-Mediated Apoptosis in Renal Cancer Cells via Ubiquitin-Proteasome Pathway

“…IITZ-01 exerts an anticancer effect in breast, colon and prostate cancer cells [ 15 , 16 ]. We examined whether IITZ-01 could augment TRAIL-induced apoptosis in human renal carcinoma cells.…”

“…IITZ-01, a novel potent lysosomotropic autophagy inhibitor, induced vacuolated appearance of cells due to deacidify lysosomes. IITZ-01 showed more than 10-fold potent autophagy inhibition compare with chloroquine [ 16 ]. As shown in Figure 1 b, IITZ-01 also induced vacuolation in renal carcinoma Caki-1 cells.…”

“…As shown in Figure 1 b, IITZ-01 also induced vacuolation in renal carcinoma Caki-1 cells. Previous study reported about the mechanism of IITZ-01 decreases IAP family protein involving cIAP1, XIAP and survivin in triple-negative breast cancer cells [ 16 ]. However, in our study, survivin was downregulated by IITZ-01, whereas expression of other IAP family protein (cIAP1, cIAP2 and XIAP) was not changed ( Figure 2 ).…”

“…IITZ-01 accumulates autophagosome by inhibiting autophagic flux through damaged lysosome. In addition, IITZ-01 decreases mitochondria membrane potential through downregulation of Bcl-2 and IAP family proteins followed by caspase-dependent apoptosis in breast cancer cells [ 16 ].…”