CAF secreted miR-522 suppresses ferroptosis and promotes acquired chemo-resistance in gastric cancer

TLDR

Ferroptosis is an iron‑dependent, lipid‑peroxidation–driven form of non‑apoptotic cell death, and cancer‑associated fibroblasts promote tumor progression and drug resistance through exosome secretion. The study aims to elucidate how CAF‑derived exosomes regulate lipid metabolism and ferroptosis in gastric cancer. The authors screened ferroptosis‑related genes by mass spectrometry, isolated CAF exosomes, quantified miRNAs via RT‑qPCR, and induced ferroptosis with erastin while measuring lipid‑ROS, cell viability, and mitochondrial membrane potential to demonstrate that exosomal miR‑522 inhibits ALOX15. Exosomal miR‑522 from CAFs, packaged by hnRNPA1 and stabilized by USP7, is up‑regulated by cisplatin/paclitaxel, suppresses ALOX15, reduces lipid‑ROS, and thereby confers chemo‑resistance in gastric cancer.

Abstract

Ferroptosis is a novel mode of non-apoptotic cell death induced by build-up of toxic lipid peroxides (lipid-ROS) in an iron dependent manner. Cancer-associated fibroblasts (CAFs) support tumor progression and drug resistance by secreting various bioactive substances, including exosomes. Yet, the role of CAFs in regulating lipid metabolism as well as ferroptosis of cancer cells is still unexplored and remains enigmatic.Ferroptosis-related genes in gastric cancer (GC) were screened by using mass spectrum; exosomes were isolated by ultra-centrifugation and CAF secreted miRNAs were determined by RT-qPCR. Erastin was used to induce ferroptosis, and ferroptosis levels were evaluated by measuring lipid-ROS, cell viability and mitochondrial membrane potential.Here, we provide clinical evidence to show that arachidonate lipoxygenase 15 (ALOX15) is closely related with lipid-ROS production in gastric cancer, and that exosome-miR-522 serves as a potential inhibitor of ALOX15. By using primary stromal cells and cancer cells, we prove that exosome-miR-522 is mainly derived from CAFs in tumor microenvironment. Moreover, heterogeneous nuclear ribonucleoprotein A1 (hnRNPA1) was found to mediate miR-522 packing into exosomes, and ubiquitin-specific protease 7 (USP7) stabilizes hnRNPA1 through de-ubiquitination. Importantly, cisplatin and paclitaxel promote miR-522 secretion from CAFs by activating USP7/hnRNPA1 axis, leading to ALOX15 suppression and decreased lipid-ROS accumulation in cancer cells, and ultimately result in decreased chemo-sensitivity.The present study demonstrates that CAFs secrete exosomal miR-522 to inhibit ferroptosis in cancer cells by targeting ALOX15 and blocking lipid-ROS accumulation. The intercellular pathway, comprising USP7, hnRNPA1, exo-miR-522 and ALOX15, reveals new mechanism of acquired chemo-resistance in GC.