SMAD4 endows TGF-ß1-induced highly invasive tumor cells with ferroptosis vulnerability in pancreatic cancer.

Pancreatic ductal adenocarcinoma (PDAC) is an extremely aggressive malignancy prone to recurrence and metastasis. Studies show that tumor cells with increased invasive and metastatic potential are more likely to undergo ferroptosis. SMAD4 is a critical molecule in the transforming growth factor ß (TGF-ß) pathway, which affects the TGF-ß-induced epithelial-mesenchymal transition (EMT) status. SMAD4 loss is observed in more than half of patients with PDAC. In this study, we investigated whether SMAD4-positive PDAC cells were prone to ferroptosis because of their high invasiveness. We showed that SMAD4 status almost determined the orientation of transforming growth factor ß1 (TGF-ß1)-induced EMT via the SMAD4-dependent canonical pathway in PDAC, which altered ferroptosis vulnerability. We identified glutathione peroxidase 4 (GPX4), which inhibited ferroptosis, as a SMAD4 down-regulated gene by RNA sequencing. We found that SMAD4 bound to the promoter of GPX4 and decreased GPX4 transcription in PDAC. Furthermore, TGF-ß1-induced high invasiveness enhanced sensitivity of SMAD4-positive organoids and pancreas xenograft models to the ferroptosis inducer RAS-selective lethal 3 (RSL3). Moreover, SMAD4 enhanced the cytotoxic effect of gemcitabine combined with RSL3 in highly invasive PDAC cells. This study provides new ideas for the treatment of PDAC, especially SMAD4-positive PDAC.

A new glance at autophagolysosomal-dependent or -independent function of transcriptional factor EB in human cancer.

Autophagy-lysosome system plays a variety of roles in human cancers. In addition to being implicated in metabolism, it is also involved in tumor immunity, remodeling the tumor microenvironment, vascular proliferation, and promoting tumor progression and metastasis. Transcriptional factor EB (TFEB) is a major regulator of the autophagy-lysosomal system. With the in-depth studies on TFEB, researchers have found that it promotes various cancer phenotypes by regulating the autophagolysosomal system, and even in an autophagy-independent way. In this review, we summarize the recent findings about TFEB in various types of cancer (melanoma, pancreatic ductal adenocarcinoma, renal cell carcinoma, colorectal cancer, breast cancer, prostate cancer, ovarian cancer and lung cancer), and shed some light on the mechanisms by which it may serve as a potential target for cancer treatment.

Hernandezine induces autophagic cell death in human pancreatic cancer cells via activation of the ROS/AMPK signaling pathway.

Hernandezine (Her) is a bisbenzylisoquinoline alkaloid extracted from the traditional Chinese herbal medicine Thalictrum glandulosissimum. Evidence shows that Her is a natural agonist of adenosine monophosphate (AMP)-activated protein kinase (AMPK) and induces apoptosis and autophagy in tumor cells. In this study, we investigated the role of autophagy in Her-induced cell death in human pancreatic cancer cell lines. We showed that Her dose-dependently suppressed cell proliferation, promoted autophagy and induced autophagic death in pancreatic ductal adenocarcinoma (PDAC) cell lines Capan-1 and SW1990. The IC50 values of Her in inhibition of Capan-1 and SW1990 cells were 47.7 µM and 40.1 µM, respectively. Immunoblotting showed that Her (1-40 µM) promoted the conversion of LC3-I to LC3-II, and Her exerted concentration-dependent and time-dependent effects on autophagy activation in PDAC cells. In transmission electron microscopy and fluorescence image analysis, we found that autophagic vacuoles were significantly increased in Her-treated cells. Knockdown of ATG5, a key gene in the autophagy pathway, alleviated the activation of autophagy by Her. These results demonstrated that Her induced autophagy in PDAC cells. Intensely activated autophagy could promote cell death. The autophagy inhibitors, BafA1 and HCQ significantly inhibited Her-induced cell death, implying that Her induced autophagic cell death in PDAC cells. Moreover, we showed that Her activated autophagy by increasing the phosphorylation of AMPK and decreasing the phosphorylation of mTOR/p70S6K. Knockdown of AMPKα relieves the autophagic cell death induced by Her. Furthermore, Her concentration-dependently enhanced reactive oxygen species (ROS) generation in PDAC cells. Antioxidants could reduce the phosphorylation of AMPK and suppress autophagic cell death induced by Her. Our study provides evidence for the development of Her as a therapeutic agent for the treatment of pancreatic cancer.

Lactate-induced protein lactylation: A bridge between epigenetics and metabolic reprogramming in cancer.

Lactate is not only an endpoint of glycolysis but is gradually being discovered to play the role of a universal metabolic fuel for energy via the 'lactate shuttle' moving between cells and transmitting signals. The glycolytic-dependent metabolism found in tumours and fast-growing cells has made lactate a pivotal player in energy metabolism reprogramming, which enables cells to obtain abundant energy in a short time. Moreover, lactate can provide favourable conditions for tumorigenesis by shaping the acidic tumour microenvironment, recruiting immune cells, etc. and the recently discovered lactate-induced lactylation moves even further on pro-tumorigenesis mechanisms of lactate production, circulation and utilization. As with other epigenetic modifications, lactylation can modify histone proteins to alter the spatial configuration of chromatin, affect DNA accessibility and regulate the expression of corresponding genes. What's more, the degree of lactylation is inseparable from the spatialized lactate concentration, which builds a bridge between epigenetics and metabolic reprogramming. Here, we review the important role of lactate in energy reprogramming, summarize the latest finding of lactylation in tumorigenesis and try to explore therapeutic strategies in oncotherapy that can kill two birds with one stone.