Ferroptosis, a form of iron-dependent cell death driven by cellular metabolism and iron-dependent lipid peroxidation, has been implicated as a tumor-suppressor function for cancer therapy. Recent advance revealed that the sensitivity to ferroptosis is tightly linked to numerous biological processes, including metabolism of amino acid and the biosynthesis of glutathione. Here, by using a high-throughput CRISPR/Cas9-based genetic screen in HepG2 hepatocellular carcinoma cells to search for metabolic proteins inhibiting ferroptosis, we identified a branched-chain amino acid aminotransferase 2 (BCAT2) as a novel suppressor of ferroptosis. Mechanistically, ferroptosis inducers (erastin, sorafenib, and sulfasalazine) activated AMPK/SREBP1 signaling pathway through iron-dependent ferritinophagy, which in turn inhibited BCAT2 transcription. We further confirmed that BCAT2 as the key enzyme mediating the metabolism of sulfur amino acid, regulated intracellular glutamate level, whose activation by ectopic expression specifically antagonize system Xc^– inhibition and protected liver and pancreatic cancer cells from ferroptosis in vitro and in vivo. On the contrary, direct inhibition of BCAT2 by RNA interference, or indirect inhibition by blocking system Xc^– activity, triggers ferroptosis. Finally, our results demonstrate the synergistic effect of sorafenib and sulfasalazine in downregulating BCAT2 expression and dictating ferroptotic death, where BCAT2 can also be used to predict the responsiveness of cancer cells to ferroptosis-inducing therapies. Collectively, these findings identify a novel role of BCAT2 in ferroptosis, suggesting a potential therapeutic strategy for overcoming sorafenib resistance.

Excessive and persistent inflammation after injury lead to chronic wounds, increased tissue damage or even aggressive carcinogenic transformation. Effective wound repair could be achieved by inhibiting overactive immune cells to the injured site. In this study, we obtained high concentration of PD‐L1 in exosomes from either genetically engineered cells overexpressing PD‐L1 or IFN‐γ stimulated cells. We found that exosomal PD‐L1 is specially bound to PD‐1 on T cell surface, and suppressed T cell activation. Interestingly, exosomal PD‐L1 promoted the migration of epidermal cells and dermal fibroblasts when pre‐incubated with T cells. We further embedded exosomes into thermoresponsive PF‐127 hydrogel, which was gelatinized at body temperature to release exosomes to the surroundings in a sustained manner. Of importance, in a mouse skin excisional wound model, exosomal PD‐L1 significantly fastened wound contraction and reepithelialization when embedded in hydrogel during inflammation phase. Finally, exosomal PD‐L1 inhibited cytokine production of CD8+ T cells and suppressed CD8+ T cell numbers in spleen and peripheral lymph nodes. Taken together, these data provide evidence on exosomal PD‐L1 exerting immune inhibitory effects and promoting tissue repair.

The initiation and progression of various solid tumors, including pancreatic carcinoma, are driven by a population of cells with stem cell properties, namely cancer stem cells (CSCs). Like their normal counterparts, CSCs are also believed to rely on their own microenvironment termed niches to sustain the population. Hypoxia-inducible factor-1α (HIF-1α) is a major actor in the cell survival response to hypoxia. Recently, several researchers proposed that non-stem cancer cells can convert to stem-like cells to maintain equilibrium. The present study focuses on whether non-stem pancreatic cancer cells can convert to stem-like cells and the role of HIF-1α and autophagy in modulating this conversation. The non-stem pancreatic cancer cells and pancreatic cancer stem-like cells were separated by magnetic sorting column. Intermittent hypoxia enhanced stem-like properties of non-stem pancreatic cancer cells and stimulated the levels of HIF-1α, LC3-II and Beclin. Enhanced autophagy was associated with the elevated level of HIF-1α. The conversation of non-stem pancreatic cancer cells into pancreatic cancer stem-like cells was induced by HIF-1α and autophagy. This novel finding may indicate the specific role of HIF-1α and autophagy in promoting the dynamic equilibrium between CSCs and non-CSCs. Also, it emphasizes the importance of developing therapeutic strategies targeting cancer stem cells as well as the microenvironmental influence on the tumor.

Pancreatic ductal adenocarcinoma (PDAC) is a solid organ malignancy with a high mortality rate. Statistics indicate that its incidence has been increasing as well as the associated deaths. Most patients with PDAC show poor response to therapies making the clinical management of this cancer difficult. Stromal cells in the tumor microenvironment (TME) contribute to the development of resistance to therapy in PDAC cancer cells. Cancer-associated fibroblasts (CAFs), the most prevalent stromal cells in the TME, promote a desmoplastic response, produce extracellular matrix proteins and cytokines, and directly influence the biological behavior of cancer cells. These multifaceted effects make it difficult to eradicate tumor cells from the body. As a result, CAF-targeting synergistic therapeutic strategies have gained increasing attention in recent years. However, due to the substantial heterogeneity in CAF origin, definition, and function, as well as high plasticity, majority of the available CAF-targeting therapeutic approaches are not effective, and in some cases, they exacerbate disease progression. This review primarily elucidates on the effect of CAFs on therapeutic efficiency of various treatment modalities, including chemotherapy, radiotherapy, immunotherapy, and targeted therapy. Strategies for CAF targeting therapies are also discussed.

Objective: To investigate the exact role of GRP78 in artesunate-induced ferroptosis in KRAS mutant pancreatic cancer cells. Methods: Artesunate-induced KRAS mutant human pancreatic cancer cells (AsPC-1 and PaTU8988) ferroptosis was confirmed by fluorescent staining experiments and CCK8. Western blot and short-hairpin RNA-based knockdown assays were conducted to detect GRP78 activity and its role in artesunate-induced ferroptosis. Results: Artesunate induced AsPC-1 and PaTU8988 cell death in ferroptosis manner, rather than necrosis or apoptosis. In addition, artesunate increased the mRNA and protein levels of GRP78 in a concentration-dependent manner in AsPC-1 and PaTU8988 cells. Knockdown GRP78 enhanced artesunate-induced ferroptosis of pancreatic cancer cells in vitro and in vivo. Conclusion: Combining artesunate with GRP78 inhibition may be a novel maneuver for effective killing of KRAS mutant pancreatic ductal adenocarcinoma cells.

Differentiated cancer cells reacquiring stem cell traits following radiotherapy may enrich cancer stem cells and accelerate tumor recurrence and metastasis. We are interested in the mechanistic role of dying cells-derived HMGB1 in CD133⁻ pancreatic cancer cells dedifferentiation following radiotherapy. We firstly confirmed that X-ray irradiation induced differentiation of CD133⁻ pancreatic cancer cells, from either sorted from patient samples or established cell lines, into cancer stem-like cells (iCSCs). Using an in vitro coculture model, X-ray irradiation induced dying cells to release HMGB1, which further promoted CD133⁻ pancreatic cancer cells regaining stem cell traits, such as higher sphere forming ability and expressed higher level of stemness-related genes and proteins. Inhibiting the expression and activity of HMGB1 attenuated the dedifferentiation stimulating effect of irradiated, dying cells on C133⁻ pancreatic cancer cells in vitro and in PDX models. Mechanistically, HMGB1 binding with TLR2 receptor functions in a paracrine manner to affect CD133⁻ pancreatic cancer cells dedifferentiation via activating Hippo-YAP pathway and HIF-1α expression in oxygen independent manner in vitro and in vivo. We conclude that X-ray irradiation induces CD133⁻ pancreatic cancer cell dedifferentiation into a CSC phenotype, and inhibiting HMGB1 may be a strategy to prevent CSC enrichment and further pancreatic carcinoma relapse.