The regulation and function of Nrf2 signaling in ferroptosis-activated cancer therapy.

Ferroptosis is an iron-dependent programmed cell death process that involves lipid oxidation via the Fenton reaction to produce lipid peroxides, causing disruption of the lipid bilayer, which is essential for cellular survival. Ferroptosis has been implicated in the occurrence and treatment response of various types of cancer, and targeting ferroptosis has emerged as a promising strategy for cancer therapy. However, cancer cells can escape cellular ferroptosis by activating or remodeling various signaling pathways, including oxidative stress pathways, thereby limiting the efficacy of ferroptosis-activating targeted therapy. The key anti-oxidative transcription factor, nuclear factor E2 related factor 2 (Nrf2 or NFE2L2), plays a dominant role in defense machinery by reprogramming the iron, intermediate, and glutathione peroxidase 4 (GPX4)-related network and the antioxidant system to attenuate ferroptosis. In this review, we summarize the recent advances in the regulation and function of Nrf2 signaling in ferroptosis-activated cancer therapy and explore the prospect of combining Nrf2 inhibitors and ferroptosis inducers as a promising cancer treatment strategy.

PRMT6-mediated ADMA promotes p62 phase separation to form a negative feedback loop in ferroptosis.

Purpose: Due to intrinsic defensive response, ferroptosis-activating targeted therapy fails to achieve satisfactory clinical benefits. Though p62-Keap1-Nrf2 axis is activated to form a negative feedback loop during ferroptosis induction, how p62 is activated remains largely unknown. Methods: MTS assay was applied to measure cell growth. Lipid ROS was detected with C11-BODIPY reagent by flow cytometer. Quantitative real-time PCR (qPCR) and western blotting were performed to determine mRNA and protein level. Immunofluorescence (IF) was performed to examine the distribution of proteins. Fluorescence recovery after photobleaching (FRAP) was adopted to evaluate p62 phase separation. Immunoprecipitation (IP), co-IP and Proximal ligation assay (PLA) were performed to detected protein posttranslational modifications and protein-protein interactions. Tumor xenograft model was employed to inspect in vivo growth of pancreatic cancer cells. Results: Upon ferroptosis induction, Nuclear Factor E2 Related Factor 2 (Nrf2) protein and its downstream genes such as HMOX1 and NQO1 were upregulated. Knockdown of p62 significantly reversed Nrf2 upregulation and Keap1 decrease after ferroptosis induction. Knockdown of either p62 or Nrf2 remarkably sensitized ferroptosis induction. Due to augmented p62 phase separation, formation of p62 bodies were increased to recruit Keap1 after ferroptosis induction. Protein arginine methyltransferase 6 (PRMT6) mediated asymmetric dimethylarginine (ADMA) of p62 to increase its oligomerization, promoting p62 phase separation and p62 body formation. Knockdown of p62 or PRMT6 notably sensitized pancreatic cancer cells to ferroptosis both in vitro and in vivo through suppressing Nrf2 signaling. Conclusion: During ferroptosis induction, PRMT6 mediated p62 ADMA to promote its phase separation, sequestering Keap1 to activate Nrf2 signaling and inhibit ferroptosis. Therefore, targeting PRMT6-mediated p62 ADMA could be a new option to sensitize ferroptosis for cancer treatment.

Relevance and mechanism of STAT3/miR-221-3p/Fascin-1 axis in EGFR TKI resistance of triple-negative breast cancer.

The epidermal growth factor receptor 1 (EGFR) plays a crucial role in the progression of various malignant tumors and is considered a potential target for treating triple-negative breast cancer (TNBC). However, the effectiveness of representative tyrosine kinase inhibitors (TKIs) used in EGFR-targeted therapy is limited in TNBC patients. In our study, we observed that the TNBC cell lines MDA-MB-231 and MDA-MB-468 exhibited resistance to Gefitinib. Treatment with Gefitinib caused an upregulation of Fascin-1 (FSCN1) protein expression and a downregulation of miR-221-3p in these cell lines. However, sensitivity to Gefitinib was significantly improved in both cell lines with either inhibition of FSCN1 expression or overexpression of miR-221-3p. Our luciferase reporter assay confirmed that FSCN1 is a target of miR-221-3p. Moreover, Gefitinib treatment resulted in an upregulation of phosphorylated signal transducer and activator of transcription 3 (p-STAT3) in MDA-MB-231 cells. Using Stattic, a small-molecule inhibitor of STAT3, we observed a significant enhancement in the inhibitory effect of Gefitinib on the growth, migration, and invasion of MDA-MB-231 cells. Additionally, Stattic treatment upregulated miR-221-3p expression and downregulated FSCN1 mRNA and protein expression. A strong positive correlation was noted between the expression of STAT3 and FSCN1 in breast cancer tissues. Furthermore, patients with high expression levels of both STAT3 and FSCN1 had a worse prognosis. Our findings suggest that elevated FSCN1 expression is linked to primary resistance to EGFR TKIs in TNBC. Moreover, we propose that STAT3 regulates the expression of miR-221-3p/FSCN1 and therefore modulates resistance to EGFR TKI therapy in TNBC. Combining EGFR TKI therapy with inhibition of FSCN1 or STAT3 may offer a promising new therapeutic option for TNBC.

Estrogen receptor α inhibits Caveolin 1 translation by promoting m6A-dependent miR199a-5p maturation to confer nab-paclitaxel resistance.

Estrogen receptor positive (ER+) breast cancer patients exhibit poorer responsiveness to nab-paclitaxel compared to ER negative (ER-) patients, with the underlying mechanisms remaining unknown. Caveolin 1 (CAV1) is a membrane invagination protein critical for the endocytosis of macromolecules including albumin-bound chemotherapeutic agents. Here, we demonstrate that ERα limits the efficacy of nab-paclitaxel in breast cancer cells while genetic or pharmacological inhibition of ERα increased the sensitivity of ER+ breast cancer cells to nab-paclitaxel. Notably, CAV1 expression inversely correlates with ERα and relates to improved clinical outcomes from nab-paclitaxel treatment. Importantly, ERα stimulates m6A dependent maturation of miR199a-5p, which is elevated in ER+ breast cancer, to inhibit CAV1 translation by antagonizing m6A modification of CAV1 mRNA. Together, our findings reveal a novel role of ERα in promoting m6A modification and subsequent maturation of miR199a-5p, which is upregulated in ER+ breast cancer, leading to the suppression of m6A modification of CAV1 and its mRNA translation, thereby contributing to nab-paclitaxel resistance. Thus, combining an ER antagonist with nab-paclitaxel could offer a promising strategy for treating ER+ breast cancer patients.