Senescence is associated with tumor metastasis and chemotherapy resistance, yet the mechanisms remain elusive. Here, it is identified that nasopharyngeal carcinoma (NPC) patients who developed distant metastasis are characterized by senescence phenotypes, in which circWDR37 is a key regulator. CircWDR37 deficiency limits cisplatin or gemcitabine‐induced senescent NPC cells from proliferation, migration, and invasion. Mechanistically, circWDR37 binds to and dimerizes double‐stranded RNA‐activated protein kinase R (PKR) to initiate PKR autophosphorylation and activation. Independent of its kinase activity, phosphorylated PKR induces I‐kappaB kinase beta (IKKβ) phosphorylation, binds to and releases RELA from NF‐κB inhibitor alpha (IκBα) to trigger nuclear factor kappa B (NF‐κB) activation, thereby stimulating cyclin D1 (CCND1) and senescence‐associated secretory phenotype component gene transcription in a circWDR37‐dependent manner. Low circWDR37 levels correlate with chemotherapy response and favorable survival in NPC patients treated with gemcitabine or cisplatin induction chemotherapy. This study uncovers a new mechanism of circWDR37 activated PKR in senescence‐driven metastasis and provides appealing therapeutic targets in NPC.
Purpose: Cisplatin-based chemotherapy effectively improves the distant-metastasis control in nasopharyngeal carcinoma (NPC), but approximately 30% of patients develop treatment failure due to chemoresistance. However, the underlying mechanisms remain poorly understood. Experimental Design: CircRNA sequencing data were used to identify metastasis-specific circRNAs and the expression of circIPO7 was validated in NPC tissues as well as NPC cell lines by qRT-PCR. The whole transcriptional profile upon circIPO7 knockdown was applied to explore the biological function and regulatory mechanism, which were further confirmed by in vitro and in vivo metastasis/chemosensitivity assays. We also evaluated the value of circIPO7 expression in predicting NPC metastasis and cisplatin chemoresistance by analyzing a cohort of 183 NPC patients. Results: In the current study, circIPO7, a novel circular RNA (circRNA), is found to be specifically overexpressed in NPC patients with distant metastasis. Knockdown of circIPO7 in NPC cells suppresses their metastasis and increases sensitivity to cisplatin treatment in vitro and in vivo. Mechanistically, circIPO7 binds to Y-box binding protein-1 (YBX1) protein in the cytoplasm and facilitates its phosphorylation at serine 102 (p-YBX1S102) by the kinase AKT, which further promotes YBX1 nuclear translocation and activates FGFR1, TNC, and NTRK1 transcription. Clinically, higher circIPO7 expression indicates unfavorable distant metastasis-free survival in NPC patients given cisplatin-based chemotherapy. Conclusions: Altogether, this study identifies oncogenic circIPO7 as a prognostic marker after cisplatin-based chemotherapy and as a potential therapeutic target for overcoming metastasis and chemoresistance in NPC.
Accurate risk stratification for patients with locoregionally advanced nasopharyngeal carcinoma (LA-NPC) is crucial for treatment decisions and prognosis. Here, we introduce a circRNA-based classifier that could improve the prognostic stratification of LA-NPC patients. The circRNAs are identified by microarray profiling, followed by qRT-PCR validation and selection using a machine learning method in the training cohort (n = 170). Based on the proposed classifier, two prognostic-distinctive NPC subtypes are identified, namely the high-risk subtype (subtype H) and low-risk subtype (subtype L), which have significantly different disease-free survival (HR 2.99, 95% CI 1.58-5.67, P < 0.001). Validation in the internal cohort (n = 170) and external cohort (n = 150) yield similar results and the circRNA-based classifier is an independent risk factor of posttreatment relapse. Meanwhile, multiple interdependent features of different subtypes are observed, including relatively higher immune cell infiltration and immune-related pathways activation in subtype L; and predominant stromal, immunosuppressive and tumor-promoting components with moderate immune activation in subtype H. With a less aggressive and more immune-active tumor microenvironment, patients of subtype L could benefit from the addition of induction chemotherapy. In contrast, patients of subtype H, who are vulnerable to chemoresistance, display a strong tendency to benefit from additional immunotherapy. Overall, we define two NPC prognostic subtypes based on a circRNA classifier across multiple cohorts, which exhibit distinct biological ecosystems and suggest opportunities for the personalization of therapeutic regimens. Citation Format: Yelin Liang, Yuheng Zhao, Qian Li, Wei Jiang, Jun Ma, Na Liu, Yingqin Li. Identification and characterization of nasopharyngeal carcinoma prognostic subtypes based on a circRNA classifier: Implications of stratified treatment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5128.
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