KRAS/ERK pathway phosphorylates DICER1, causing its nuclear translocation, and phosphomimetic
Dicer1
contributes to tumorigenesis in mice. Mechanisms through which phospho-DICER1 regulates tumor progression remain undefined. While DICER1 canonically regulates microRNAs (miRNA) and epithelial-to-mesenchymal transition (EMT), we found that phosphorylated nuclear DICER1 (phospho–nuclear DICER1) promotes late-stage tumor progression in mice with oncogenic
Kras
, independent of miRNAs and EMT. Instead, we observe that the murine AT2 tumor cells exhibit altered chromatin compaction, and cells from disorganized advanced tumors, but not localized tumors, express gastric genes. Collectively, this results in subpopulations of tumor cells transitioning from a restricted alveolar to a broader endodermal lineage state. In human LUADs, we observed expression of phospho–nuclear DICER1 in advanced tumors together with the expression of gastric genes. We define a multimeric chromatin-DICER1 complex composed of the Mediator complex subunit 12, CBX1, MACROH2A.1, and transcriptional regulators supporting the model that phospho–nuclear DICER1 leads to lineage reprogramming of AT2 tumor cells to mediate lung cancer progression.
DICER1 controls micro(mi)RNA-mediated epithelial-to-mesenchymal transition (EMT) to regulate tumorigenesis of lung adenocarcinomas (LUADs). We discovered that DICER1 is phosphorylated by ERK and nuclear translocated and phospho-DICER1 contributes to tumorigenesis. Mechanisms through which phospho-DICER1 regulates tumor progression remain undefined. We show that phospho-nuclear DICER1 associates with invasive human LUADs with oncogenic KRAS mutations and promotes late-stage tumor progression in mice with oncogenic Kras mutations. Surprisingly, phosphomimetic DICER1 regulates LUAD progression independent of miRNAs and EMT. Integrating single-cell RNA sequencing, fluorescent in situ RNA hybridization, immunofluorescence, and ATAC-sequencing, in mice,we discovered that phosphomimetic DICER1 generates an open chromatin state in the lung tumor alveolar cells leading to expression of gastrointestinal genes and altered AT2 cell identity. Strikingly, we also observe the gastric gene signature in human LUADs with phospho-DICER1 and KRAS mutations. We propose that phosphorylated nuclear DICER1 regulates chromatin remodeling leading to tumor cell reprogramming which drives lung cancer progression.
Citation Format: Raisa A. Reyes-Castro, Shin-Yu Chen, Jacob Seemann, Swathi Arur. Phosphorylated nuclear DICER1 promotes open chromatin state and lineage plasticity of lung adenocarcinomas [abstract]. In: Proceedings of the AACR Special Conference: Cancer Metastasis; 2022 Nov 14-17; Portland, OR. Philadelphia (PA): AACR; Cancer Res 2022;83(2 Suppl_2):Abstract nr A018.
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