FOXO3a-regulated arginine metabolic plasticity adaptively promotes esophageal cancer proliferation and metastasis.

Esophageal squamous cell carcinoma (ESCC) is a common malignant tumor with a poor prognosis due to a lack of early detection. Indeed, the mechanisms underlying ESCC progression remain unclear. Here, we discovered that abnormal arginine metabolism contributes to ESCC progression. Based on transcriptomic and metabolomic analyses, we found that argininosuccinate synthetase 1 (ASS1) and argininosuccinate lyase (ASL) levels were increased in primary tumor tissues but decreased in lymph-metastatic tumor tissues. Intriguingly, FOXO3a was inversely correlated with ASS1 and ASL in primary and metastatic tumor tissues, suggesting that FOXO3a dissimilarly regulates ASS1 and ASL at different stages of ESCC. Silencing ASS1/ASL inhibited primary tumor growth and promoted metastasis. Conversely, overexpression of ASS1/ASL or increased arginine supply promoted tumor proliferation but suppressed metastasis. In addition, FOXO3a activation inhibited primary tumor growth by repressing ASS1 and ASL transcription, whereas inactivation of FOXO3a impeded metastasis by releasing ASS1 and ASL transcription. Together, the finding sheds light on metastatic reprogramming in ESCC.

Prostate cancer cell-derived exosomal IL-8 fosters immune evasion by disturbing glucolipid metabolism of CD8+ T cell.

Depletion of CD8+ T cells is a major obstacle in immunotherapy; however, the relevant mechanisms remain largely unknown. Here, we showed that prostate cancer (PCa) cell-derived exosomes hamper CD8+ T cell function by transporting interleukin-8 (IL-8). Compared to the low IL-8 levels detected in immune cells, PCa cells secreted the abundance of IL-8 and further accumulated in exosomes. The delivery of PCa cell-derived exosomes into CD8+ T cells exhausted the cells through enhanced starvation. Mechanistically, exosomal IL-8 overactivated PPARα in recipient cells, thereby decreasing glucose utilization by downregulating GLUT1 and HK2 but increasing fatty acid catabolism via upregulation of CPT1A and ACOX1. PPARα further activates uncoupling protein 1 (UCP1), leading to fatty acid catabolism for thermogenesis rather than ATP synthesis. Consequently, inhibition of PPARα and UCP1 restores CD8+ T cell proliferation by counteracting the effect of exosomal IL-8. This study revealed that the tumor exosome-activated IL-8-PPARα-UCP1 axis harms tumor-infiltrating CD8+ T cells by interfering with energy metabolism.

RelB-activated GPX4 inhibits ferroptosis and confers tamoxifen resistance in breast cancer.

Tamoxifen (TAM) resistance remains a major obstacle in the treatment of advanced breast cancer (BCa). In addition to the competitive inhibition of the estrogen receptor (ER) signaling pathway, damping of mitochondrial function by increasing reactive oxygen species (ROS) is critical for enhancing TAM pharmacodynamics. Here, we showed that RelB contributes to TAM resistance by inhibiting TAM-provoked ferroptosis. TAM-induced ROS level promoted ferroptosis in TAM-sensitive cells, but the effect was alleviated in TAM-resistant cells with high constitutive levels of RelB. Mechanistically, RelB inhibited ferroptosis by transcriptional upregulating glutathione peroxidase 4 (GPX4). Consequently, elevating RelB and GPX4 in sensitive cells increased TAM resistance, and conversely, depriving RelB and GPX4 in resistant cells decreased TAM resistance. Furthermore, suppression of RelB transcriptional activation resensitized TAM-resistant cells by enhancing ferroptosis in vitro and in vivo. The inactivation of GPX4 in TAM-resistant cells consistently resensitized TAM by increasing ferroptosis-mediated cell death. Together, this study uncovered that inhibition of ferroptosis contributes to TAM resistance of BCa via RelB-upregulated GPX4.

Stromal cell-derived small extracellular vesicles enhance radioresistance of prostate cancer cells via interleukin-8-induced autophagy.

Radiation is a curative treatment for localized prostate cancer (PCa). Unfortunately, radiotherapeutic efficacy is often diminished when patients develop more aggressive or metastatic phenotypes. Recent studies have demonstrated that extracellular vesicles participate in cancer therapeutic resistance by delivering small bioactive molecules, such as small non-coding RNAs. Here, we show that stromal cell-derived small extracellular vesicles (sEVs) facilitate the radioresistance of PCa cells by transporting interleukin-8 (IL-8). Indeed, prostatic stromal cells secrete more IL-8 than AR-positive PCa cells, which can be accumulated in sEVs. Intriguingly, the uptake of stromal cells-derived sEVs by radiosensitive PCa cells enhanced their radioresistance, which could be attenuated by silencing CXCL8 in stromal cells or inhibiting its receptor CXCR2 in PCa cells. sEV-mediated radioresistance has been validated in zebrafish and mouse xenograft tumours. Mechanistically, the uptake of stromal sEVs triggers the AMPK-activated autophagy pathway in PCa cells under the irradiation condition. Consequently, inactivating AMPK efficiently resensitized radiotherapy either by utilizing an AMPK inhibitor or silencing AMPKα in PCa cells. Furthermore, chloroquine (CQ), a lysosomal inhibitor, sufficiently resensitized radiotherapy via blockade of autophagolysosome fusion, leading to autophagosome accumulation in PC cells. Collectively, these results suggest that stromal cells enhance the radioresistance of PCa cells mainly through sEVs that deliver IL-8.