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Excessive macroautophagy/autophagy is one of the causes of cardiomyocyte death induced by cardiovascular diseases or cancer therapy, yet the underlying mechanism remains unknown. We and other groups previously reported that autophagy might contribute to cardiomyocyte death caused by sunitinib, a tumor angiogenesis inhibitor that is widely used in clinic, which may help to understand the mechanism of autophagy-induced cardiomyocyte death. Here, we found that sunitinib-induced autophagy leads to apoptosis of cardiomyocyte and cardiac dysfunction as the cardiomyocyte-specific Atg7−/+ heterozygous mice are resistant to sunitinib. Sunitinib-induced maladaptive autophagy selectively degrades the cardiomyocyte survival mediator CCN2 (cellular communication network factor 2) through the TOLLIP (toll interacting protein)-mediated endosome-related pathway and cardiomyocyte-specific knockdown of Ccn2 through adeno-associated virus serotype 9 (AAV9) mimics sunitinib-induced cardiac dysfunction in vivo, suggesting that the autophagic degradation of CCN2 is one of the causes of sunitinib-induced cardiotoxicity and death of cardiomyocytes. Remarkably, deletion of Hmgb1 (high mobility group box 1) inhibited sunitinib-induced cardiomyocyte autophagy and apoptosis, and the HMGB1-specific inhibitor glycyrrhizic acid (GA) significantly mitigated sunitinib-induced autophagy, cardiomyocyte death and cardiotoxicity. Our study reveals a novel target protein of autophagic degradation in the regulation of cardiomyocyte death and highlights the pharmacological inhibitor of HMGB1 as an attractive approach for improving the safety of sunitinib-based cancer therapy. [ABSTRACT FROM AUTHOR]

Liver dysfunction is an outstanding dose-limiting toxicity of gefitinib, an EGFR (epidermal growth factor receptor)-tyrosine kinase inhibitor (TKI), in the treatment of EGFR mutation-positive non-small cell lung cancer (NSCLC). We aimed to elucidate the mechanisms underlying gefitinib-induced hepatotoxicity, and provide potentially effective intervention strategy. We discovered that gefitinib could sequentially activate macroautophagy/autophagy and apoptosis in hepatocytes. The inhibition of autophagy alleviated gefitinib-induced apoptosis, whereas the suppression of apoptosis failed to lessen gefitinib-induced autophagy. Moreover, liver-specific Atg7+/− heterozygous mice showed less severe liver injury than vehicle, suggesting that autophagy is involved in the gefitinib-promoted hepatotoxicity. Mechanistically, gefitinib selectively degrades the important anti-apoptosis factor COX6A1 (cytochrome c oxidase subunit 6A1) in the autophagy-lysosome pathway. The gefitinib-induced COX6A1 reduction impairs mitochondrial respiratory chain complex IV (RCC IV) function, which in turn activates apoptosis, hence causing liver injury. Notably, this autophagy-promoted apoptosis is dependent on PLK1 (polo like kinase 1). Both AAV8-mediated Plk1 knockdown and PLK1 inhibitor BI-2536 could mitigate the gefitinib-induced hepatotoxicity in vivo by abrogating the autophagic degradation of the COX6A1 protein. In addition, PLK1 inhibition could not compromise the anti-cancer activity of gefitinib. In conclusion, our findings reveal the gefitinib-hepatotoxicity pathway, wherein autophagy promotes apoptosis through COX6A1 degradation, and highlight pharmacological inhibition of PLK1 as an attractive therapeutic approach toward improving the safety of gefitinib-based cancer therapy. Abbreviations: 3-MA: 3-methyladenine; AAV8: adeno-associated virus serotype 8; ATG5: autophagy related 5; ATG7: autophagy related 7; B2M: beta-2-microglobulin; CCCP: carbonyl cyanide m-chlorophenylhydrazone; CHX: cycloheximide; COX6A1: cytochrome c oxidase subunit 6A1; c-PARP: cleaved poly(ADP-ribose) polymerase; CQ: chloroquine; GOT1/AST: glutamic-oxaloacetic transaminase 1, soluble; GPT/ALT: glutamic pyruvic transaminase, soluble; HBSS: Hanks´ balanced salt solution; H&E: hematoxylin and eosin; MAP1LC3/LC3: microtubule associated proteins 1 light chain 3; PLK1: polo like kinase 1; RCC IV: respiratory chain complex IV; ROS: reactive oxygen species; TUBB8: tubulin beta 8 class VIII [ABSTRACT FROM AUTHOR]