# A DNA Methylation-Dependent NOP56/MYC Positive Feedback Loop Promotes the Proliferation and Migration of Non-Small Cell Lung Cancer Through Regulating Ribosome Biogenesis

## TL;DR

This study shows that NOP56, a protein involved in ribosome assembly, promotes non-small cell lung cancer growth and spread through a DNA methylation-dependent feedback loop with MYC.

## Contribution

The discovery of a NOP56/MYC positive feedback loop regulated by DNA methylation in non-small cell lung cancer.

## Key findings

- NOP56 is upregulated in NSCLC and linked to poor patient outcomes.
- NOP56 activates MYC signaling via IRES-dependent translation, forming a self-amplifying loop.
- Reduced DNA methylation contributes to NOP56 upregulation in NSCLC.

## Abstract

Non-small cell lung cancer is a leading cause of cancer mortality, underscoring the need for new therapeutic concepts. Cellular proliferation depends on the construction of ribosomes, the protein-synthesizing machinery, and malignant cells often intensify this process. We investigated whether NOP56, a factor in ribosome assembly, is pathologically elevated in this disease, how it influences tumor growth and dissemination, and which molecular events drive its increase. Integrating cohorts with mechanistic studies in vitro and in vivo, we show that NOP56 is upregulated, associates with unfavorable outcomes, and accelerates proliferation, invasion, and ribosome production. We further demonstrate that it activates a pro-growth gene program through a specialized mode of translation, which in turn augments NOP56, establishing a self-amplifying loop; reduced DNA methylation also contributes. These findings identify NOP56 as a tractable therapeutic node and inform biomarker development and rational combinations targeting ribosome biogenesis.

Background: Recent findings underscore the importance of ribosome biogenesis, a complex molecular machinery, in cancer biology, highlighting opportunities for targeted treatment strategies. Here, we revealed that dysregulation of ribosome biogenesis is a distinctive feature of non-small lung cancer (NSCLC). However, further investigation is required to pinpoint which specific processes within this complex pathway are aberrant in this malignancy. Methods: The expression levels and clinical significance of NOP56 in NSCLC were investigated by microarray analysis, qPCR, TCGA and GEO datasets. Function assays were conducted to explore the biological role of NOP56 in NSCLC cells. The mechanisms that mediate the upregulation of NOP56 were investigated by bisulfite DNA sequencing, luciferase reporter assay, chromatin immunoprecipitation and TCGA datasets. The downstream pathway of NOP56 was explored by RNA sequencing, qPCR, Western blot and luciferase reporter assay. Results: High expression of NOP56 was detected in NSCLC tissues and was associated with poor prognosis. Functional assays revealed that overexpression of NOP56 promoted NSCLC cellular proliferation, metastasis and ribosome biogenesis in vitro, and further accelerated tumorigenesis in vivo. Mechanistically, NOP56 activates MYC signaling by regulating IRES-dependent translation, which in turn transcriptionally upregulated NOP56 expression, creating a positive feedback loop. Additionally, hypomethylation also contributed to the upregulation of NOP56 in NSCLC. Conclusions: Our study demonstrated that NOP56/MYC forms a positive feedback loop that enhances ribosome biogenesis and drives the progression of NSLSC, positioning NOP56 a promising therapeutic target for this malignancy.