Feng Li

CircSMAD2 accelerates endometrial cancer cell proliferation and metastasis by regulating the miR-1277-5p/MFGE8 axis

Endometrial cancer (EC) is a common gynecological malignant tumor. CircRNAs play crucial roles in cancer progression and metastasis. However, the biological functions of circRNAs in EC remain largely unknown. CircSMAD2, miR-1277-5p, MFGE8 and relative maker protein expression in EC tissues or cell lines were analyzed by quantitative real-time polymerase chain reaction and Western blot. In vitro and in vivo functional assays, including EDU, CCK8, colony formation, transwell, tube formation and tumor xenograft assays, were conduct to explore the effects of circSMAD2 on EC. Mechanism assays were conducted to confirm the binding between miR-1277-5p and circSMAD2 or MFGE8 expression. Upregulation of circSMAD2 was uncovered in both EC tissues and cell lines. Functionally, silencing of circSMAD2 apparently inhibited the proliferation, migration, invasion and angiogenesis of EC cell lines in vitro. Mechanistically, circSMAD2 sponged miR-1277-5p to upregulate MFGE8 expression. The decrease of miR-1277-5p and increase of MFGE8 were observed both in EC tissues and cell lines. Then MFGE8 knockdown or miR-1277-5p upregulation suppressed EC cell oncogenic biological behavior. Rescue experiments showed that miR-1277-5p mimics countervailed the anticancer effects of circSMAD2 silencing on EC. Besides that, MFGE8 overexpression also attenuated the inhibitory action of miR-1277-5p mimic in EC. Moreover, knockdown of circSMAD2 inhibited EC growth in vivo. CircSMAD2 functions as an oncogene in promoting the progression of EC through miR-1277-5p/MFGE8 axis.

A positive feedback loop of OTUD1 and c-Jun driven by leptin expedites stemness maintenance in ovarian cancer

Cancer stem cells (CSCs) are closely associated with drug resistance and recurrence in ovarian cancer patients. Although leptin is a high-risk factor for ovarian cancer and promotes stemness maintenance, a therapeutic strategy that counteracts the downstream signaling pathway of leptin remains elusive. Herein, the deubiquitinase OTUD1 was identified as a critical regulator of leptin in maintaining OCSCs properties. Mechanistically, leptin treatment significantly increased the chromatin enrichment of the transcription factor c-Jun, including the OTUD1 gene enhancer, which was sufficient to increase the OTUD1 protein level and subsequently cause OTUD1 aggresome formation, ASK1 recruitment and JNK/c-Jun pathway activation. The resultant positive feedback loop of c-Jun and OTUD1 was required for OCSCs stemness maintenance. Notably, the disruption of the positive feedback loop by targeting c-Jun or ASK1/JNK with T-5224, selonsertib, or ibrutinib markedly inhibited the leptin-induced stemness maintenance of OCSCs and tumorigenicity. Our findings reveal a crucial mechanism for leptin-mediated stemness maintenance and indicate that targeting c-Jun or the identified positive feedback loop has translational potential for ovarian cancer patients.

Aggresome formation promotes ASK1/JNK signaling activation and stemness maintenance in ovarian cancer

AbstractAggresomes are the product of misfolded protein aggregation, and the presence of aggresomes has been correlated with poor prognosis in cancer patients. However, the exact role of aggresomes in tumorigenesis and cancer progression remains largely unknown. Herein, the multiomics screening reveal that OTUD1 protein plays an important role in retaining ovarian cancer stem cell (OCSC) properties. Mechanistically, the elevated OTUD1 protein levels lead to the formation of OTUD1-based cytoplasmic aggresomes, which is mediated by a short peptide located in the intrinsically disordered OTUD1 N-terminal region. Furthermore, OTUD1-based aggresomes recruit ASK1 via protein-protein interactions, which in turn stabilize ASK1 in a deubiquitinase-independent manner and activate the downstream JNK signaling pathway for OCSC maintenance. Notably, the disruption of OTUD1-based aggresomes or treatment with ASK1/JNK inhibitors, including ibrutinib, an FDA-approved drug that was recently identified as an MKK7 inhibitor, effectively reduced OCSC stemness (OSCS) of OTUD1high ovarian cancer cells. In summary, our work suggests that aggresome formation in tumor cells could function as a signaling hub and that aggresome-based therapy has translational potential for patients with OTUD1high ovarian cancer.